software package for hub selection in lans
TRANSCRIPT
I
Abstract
One of the most important devices used in local computer networks are the hubs which
were and still be used with a great success because it is considered as the center of the network
and acts as the only point in star-wired networks. Hub devices are classified depending on their
configuration into three kinds: (Stand-alone, Stackable, and Enterprise hubs) and on their
functionality into: (Passive, Active, Intelligent, and Switching Hubs). Each kind has its own
benefits and limitations.
This research include a comparative study of all hub kinds through discussing their
specifications, how they work, and how specific kind fits in constructing a given network. First
we discussed the above three hub configurations then the discussion directs to the internal
functions of hubs. Dual-Speed hubs, specifications of some hub products, wiring schemes and
topologies are also explained during the research.
Therefore, and in order to show how to connect such networks, we have picked an office to
build a local network and express how the computers can be connected to the hub and the
suitable installation for the wiring system. The system also accepts maps for 2 other buildings
and chooses the rooms specified to install the computers in then the system should compute the
cable lengths and the ideal place to install the hub.
From among the most important things we realized from the work in this research is that
despite the fact that intelligent hubs are the most powerful kind of hubs regarding their functions
and Enterprise hubs regarding the flexible design and configuration, any type of hubs can be
suitable for a given cost and network requirements.
The system has been implemented using a PC computer, with PII processor and Visual Basic 6.0
programming language and Adobe Premiere and 3D Max programs to construct the buildings
and generating design graphics
II
List of Abbreviations
ANSI American National Standards Institute
ARCnet Attached Resource Computer Network
ATM Asynchronous Transfer Mode
AUI Attachment Unit Interface
CAT1 Category 1 Twisted Pair Cable
CAT4 Category 4 Twisted Pair Cable
CAT5 Category 5 Twisted Pair Cable
CSMA/CD Carrier Sense Multiple Access / Collision Detection
DUD Disconnect Unauthorized Device
EMI Electromagnetic Interference
FDDI Fiber Distributed Data Interface
IEEE Institute of Electrical and Electronics Engineers
ISO International Standards Organization
LAN Local Area Network
LEDs Light Emitting Diodes
MAU Multistation Access Unit
MIB Management Information Base
NICs Network Interface Cards
NTK Need To Know
OSI Open System Interconnection
RI Ring In
RMON Remote Monitoring
RO Ring Out
III
SNMP Simple Network Management Protocol
SNMP v.2 Simple Network Management Protocol version 2
STP Shielded Twisted Pair
TP Twisted Pair
UTP Unshielded Twisted Pair
WAN Wide Area Network
IV
......................................................................................................................................................... I Abstract
List of Abbreviations .................................................................................................................................. II
Figure List.................................................................................................................................................. VII
Table List .................................................................................................................................................. VIII
........................................................................................................................................... 1 1 Introduction
1.1 Relative Work ............................................................................................................................... 3
1.2 Aim of Thesis ................................................................................................................................ 4
1.3 Thesis Layout ................................................................................................................................ 4
.............................................................................................................. 6 2 Computer Networks and Hubs
2.1 Introduction ................................................................................................................................... 6
2.2 Network Topology ........................................................................................................................ 6
2.2.1 Bus Topology ........................................................................................................................ 6
2.2.2 Ring topology ........................................................................................................................ 7
2.2.3 Star topology ......................................................................................................................... 7
2.3 Network architecture ..................................................................................................................... 8
2.4 Ethernet ......................................................................................................................................... 8
2.5 Token ring ..................................................................................................................................... 9
2.5.1 ARCnet Architecture........................................................................................................... 10
2.6 Cable Types ................................................................................................................................ 11
2.6.1 Coaxial Cable ...................................................................................................................... 11
2.6.2 Twisted Pair Cable .............................................................................................................. 12
2.6.3 Fiber Optic Cable ................................................................................................................ 12
2.7 Open System Interconnection Reference Model ......................................................................... 13
2.8 Connectivity Devices .................................................................................................................. 14
2.8.1 Router .................................................................................................................................. 15
2.8.2 Bridge .................................................................................................................................. 15
2.8.3 Switch ................................................................................................................................. 15
2.8.4 Repeater .............................................................................................................................. 15
2.8.5 Hub ...................................................................................................................................... 15
2.9 Shared Media LAN Wiring Centers ............................................................................................ 16
2.9.1 Networks and Hubs ............................................................................................................. 16
V
2.9.2 Basic Specifications ............................................................................................................ 18
2.9.3 Multi-station Access Units (MAUs) ................................................................................... 19
2.10 Wiring Center Categories............................................................................................................ 20
2.10.1 Stand-alone Hubs ................................................................................................................ 20
2.10.2 Stackable Hubs .................................................................................................................... 21
2.10.3 Enterprise Hubs ................................................................................................................... 21
2.11 Wiring Centers Technology Analysis ......................................................................................... 24
.......................................................................................... 25 3 Functional and Security Features in Hubs
3.1 Introduction ................................................................................................................................. 25
3.2 Passive Hubs ............................................................................................................................... 26
3.3 Active Hubs ................................................................................................................................ 26
3.4 Intelligent Hubs ........................................................................................................................... 27
3.4.1 Modular design ................................................................................................................... 28
3.4.2 Structured Wiring Architecture ........................................................................................... 29
3.5 Switching Hubs ........................................................................................................................... 30
3.6 The 10/100Mbps Dual-Speed Hub ............................................................................................. 32
3.6.1 The Difference between Ethernet and Fast Ethernet ........................................................... 32
3.7 Hub Management ........................................................................................................................ 38
3.8 Practical Advice and Information ............................................................................................... 39
3.9 Simple Network Management Protocol (SNMP) ....................................................................... 39
3.9.1 The SNMP Model ............................................................................................................... 40
3.10 Example of Hubs ......................................................................................................................... 42
3.10.1 SuperStack II Dual-Speed Hub 500 .................................................................................... 42
3.10.2 Passive listening .................................................................................................................. 43
3.10.3 IBM 8237 Ethernet Stackable Hub ..................................................................................... 44
3.10.4 Intrusion .............................................................................................................................. 45
3.10.5 Port Scanning ...................................................................................................................... 45
3.10.6 D-Link Dual-Speed Rack-mount Hub Stack ....................................................................... 46
3.10.7 NetStacker II Stackable 10/100 Hubs ................................................................................. 47
3.10.8 EtherEZ Hub 10 .................................................................................................................. 48
3.11 Choosing a Hub ........................................................................................................................... 48
VI
3.11.1 Breadth of Products Offered ............................................................................................... 49
3.11.2 Depth of Services Offered ................................................................................................... 49
3.11.3 Price of Product versus Operational Savings ...................................................................... 49
4 Design and Implementation of ...................................................................... 50 the Proposed System
4.1 Introduction ................................................................................................................................. 50
4.2 Description of the System ........................................................................................................... 50
4.3 System Architecture .................................................................................................................... 50
4.3.1 Hardware Architecture ........................................................................................................ 51
4.3.2 Software Architecture ......................................................................................................... 51
4.4 The Design Process ..................................................................................................................... 51
4.5 The System Algorithms .............................................................................................................. 54
4.5.1 Select Category ................................................................................................................... 54
4.5.2 Fill Index with Subjects ...................................................................................................... 55
4.5.3 Fill Contents with Subjects ................................................................................................. 56
4.5.4 Open Database of the System ............................................................................................. 57
4.5.5 Continue the Second Part of the Practical Example ............................................................ 57
4.5.6 Index Search ........................................................................................................................ 57
4.5.7 Contents Search................................................................................................................... 58
4.6 The Implementation Process ....................................................................................................... 58
4.7 Parts of the System ...................................................................................................................... 59
4.8 The System Windows ................................................................................................................. 59
4.8.1 The Network Analysis Part ................................................................................................. 61
4.8.2 The Practical Example Window ......................................................................................... 61
4.8.3 Designing a Network Window ............................................................................................ 65
4.8.4 Network Knowledge Window ............................................................................................ 69
4.9 The Results .................................................................................................................................. 69
4.10 The Limitations ........................................................................................................................... 70
VII
Figure List
Figure 2.1 Ring Topology ............................................................................................................................... 7
Figure 2.2 Bus Topology ................................................................................................................................ 7
Figure 2.3 Star Topolgy ................................................................................................................................ 8
Figure 2.4 Star Ethernet ............................................................................................................................... 9
Figure 2.5 Token Ring Architecture .............................................................................................................. 9
Figure 2.6 ARCnet Architecture .................................................................................................................. 10
Figure 2.7 Coaxial Cable .............................................................................................................................. 11
Figure 2.8 Fiber Optic Cable ........................................................................................................................ 12
Figure 2.9 OSI Reference Model ................................................................................................................ 13
Figure 2.10 Repeaters, Bridges, and Routers .............................................................................................. 14
Figure 2.11 Basic 10Base-2 Network .......................................................................................................... 16
Figure 2.12 Building 10Base-T Network using the Hub .............................................................................. 17
Figure 2.13 Connecting Multiple Hubs to form Network Backbone ........................................................... 18
Table 2-1 LAN Technologies Comparison Quick Reference Chart .............................................................. 18
Figure 2.16 Stand-alone hub ....................................................................................................................... 23
Figure 2.17 Stackable hub ........................................................................................................................... 23
Figure 2.18 Enterprise hub .......................................................................................................................... 24
Figure 3.1 Adding a Switch to Adjust Network Wiring................................................................................ 32
Figure 3.2 The 5-4 Rule used in 10Mbps Ethernet ...................................................................................... 33
Figure 3.3 Class II Rule used in 100Mbps Fast Ethernet ............................................................................. 33
Figure 3.4 Internal 10Mbps and 100Mbps Segments ................................................................................. 34
Figure 3.5 Auto-negotiation Ports .............................................................................................................. 35
Figure 3.6 The Internal Switch connecting 10Mbps and 100Mbps Segments ........................................... 36
Figure 3.7 The Internal Switch connecting 10Mbps and 100Mpbs Logical Hubs ....................................... 36
Figure 3.8 100Mbps Bus connecting Dual-Speed Hubs .............................................................................. 37
Figure 3.9 External Switch Port in Dual-Speed Hubs .................................................................................. 37
Figure 3.10 Standards-based Network Management Communications Protocols .................................... 38
Figure 4.1Flowchart of the System ............................................................................................................. 53
Figure 4.2 The Main Window ...................................................................................................................... 59
Figure 4.3 The Contents Tab ....................................................................................................................... 60
Figure 4.4 The Index Tab ............................................................................................................................. 60
Figure 4.5The Network Analysis Category .................................................................................................. 61
Figure 4.6 Top View of the Building before constructing the Network ...................................................... 61
Figure 4.7 Choosing the Location of the Hub ............................................................................................. 62
Figure 4.8 Choosing the Location of the Network Server along with Cable Length to the Hub ................. 62
VIII
Figure 4.9 Installing the Computers and Choosing the Cable Lengths in the 2nd Room ............................. 63
Figure 4.10 Installing the Computers and Choosing the Cable Lengths in the 3rd Room ........................... 63
Figure 4.12 Top View of the Building after constructing the Network ....................................................... 64
Figure 4.11 Installing the Computers and Choosing the Cable Lengths in the 4th and 5th Rooms .......... 64
Figure 4.13 The Map of the First Building before Constructing the Network ............................................ 65
Figure 4.14 Choosing the Computers for the Network ............................................................................... 66
Figure 4.15 The Hub Location and the Wiring System after Connecting the Computers .......................... 66
Figure 4.16 The Map of the Second Building before Constructing the Network ....................................... 67
Figure 4.17 Choosing the Computers for the Network ............................................................................... 67
Figure 4.18 The Hub Location and the Wiring System after Connecting the Computer ............................ 68
Figure 4.19 Network Knowledge Window .................................................................................................. 69
Table List
Table 2-1 LAN Technologies Comparison Quick Reference Chart .............................................................. 18
Table 2-2 Some of the major technical features to be used for comparative analysis are listed below in
table 2-2. Before purchasing a wiring center of any type, the implications of various possible features
listed in the Wiring Center Technology Analysis may be useful to consider. [6] ...................................... 24
Table 3-1 Features of Passive, Active, Intelligent and Switching Hubs. ...................................................... 30
IX
1
1 Introduction
One of the most fascinating aspects of computer industry is the rapid pace at which
available products manage to evolve. Unlike most other industries, where product lines
experience revolutionary growth every five to fifteen (or potentially more) years, most
projections show networking technology undergoing logarithmic growth every year and a
half. Part of the reason for this explosive growth is the large number of software publishers
and hardware manufacturers dedicated to improving the speed and performance of
computing.
Because network computing is such a large component of computing in the business world,
it is quite easy to see why there are so many vendors who specialize in networking hardware
and software all dedicated to making the LAN and WAN perform as well as they possibly
can. Originally, only medium to large-sized businesses could afford the cost of networking
hardware. The affordable price and added convenience of having a LAN has made it
common place to see networks in many homes and offices. Each PC in a LAN is able to
access shared files and devices anywhere on the LAN. This makes the sharing of expensive
devices, such as laser printers or large removable storage drives a cost-effective alternative
to purchasing a device for every user.
LANs require a Hub, a hardware device that all PCs on a network are connected to by
cabling in a star networks. Hubs are a very important part of the networking process. Hubs
are wiring concentrarors, which make use of structured wiring to connect stations on a
LAN. They contain user ports into which each station’s cable is connected. Many hubs are
called intelligent, or manageable, which means that each of the ports on the hub can be
configured, monitored, enabled, and disabled by a network operator from a hub
management console.
The hub manages receiving and transmitting data from networked devices. Hubs come in
many different port configurations, but they will probably need a 4, 8, or 12 ports,
depending on the number of PCs connected together. Each port supports a single
2
10Base-T1 connection from a PC or peripheral. In case of using Coaxial cable, there will be
a need to find a hub with one coaxial port and minimal twisted pair ports. In contrast to
manageable hubs, there are standard hubs, which are cheaper and usually used for home or
small office networks.
While some theoretically minded people would claim that the hardware involved in a
network isn't extremely important, they probably haven't ever actually dealt with setting up
one. Hardware is important. While in theory, every hub should send and receive signals
perfectly, that isn't always the case. And the problem is that when asking two network
administrators what hub they recommend, two entirely different answers will be obtained.
From picking the cable (optical fiber, coaxial, or copper), to choosing a server, the most
suitable hardware for a given needs should be found.
One of the most important aspects in the world of computer networks is the network
security. Network security is setup to guard against unauthorized access, alteration, or
modification of information, and unauthorized denial of service. A well-established network
security and a well-implemented security policy can provide a highly secure solution so that
only authorized people gain access to the system, that communications on the network are
kept private from outsiders, and that data being communicated is kept safe. Some kinds of
hubs have additional features added to their main function that provide security to the
network. All these features will be explained in chapter three from this research.
When thinking about what type of standard hub can be purchased, what will be doing with
the network in the near future must be thought about. Will many more devices be added to
the network? If so, the hub should be assured to handle network expansion. [1,2,3,4]
All these and related issues will be clarified in this research by explaining the basic kinds of
hubs: Passive, Active, Intelligent, and Switching hubs, their functions, configurations and
differences between them which gives a good basis in deciding to purchase the suitable hub
in building small or medium-sized networks.
1 10Base-T Ethernet version that uses twisted-pair cabling, the name is derived from the speed of the
network (10Mbps), the signaling type (baseband), and the cable type (twisted pair).
3
1.1 Relative Work
Mitchell Bradley [13], part I of this article provides a general characteristics and key
features in hubs and brief description of the three kinds of hubs (passive, active, and
intelligent) by examining their basic functions. Part II lists three different factors
that determine the cost of the hub which are: the number of ports it features, the
speed rating, and the manufacturers and their reputation for quality, and gives a brief
explanation for each factor.
Wang Jonathan [14], this paper comprises a detailed illustration of dual-speed hubs
and how they can help in solving the two problems associated with migration from
standard Ethernet to Fast Ethernet which are: network wiring adjustment and
network structure adjustment. It also contains the most common specifications
shared by such hubs including Auto Detection, Internal 10Mbps and 100Mbps
segments, Auto-negotiation ports, and Extension port or external switch port
although there is no uniform standard defined for them yet. Finally it illustrates a
case study in replacing the old 10Mbps Ethernet with a new Fast Ethernet.
A MARKEN Communication, this paper explains intelligent hubs that serve as
central points for combining end-user connectivity, internetworking, and
management capabilities. It illustrates their importance for distributed computing
environment, their features including modularity and multiple access, their selection
consideration in terms of flexibility and expandability, and their role in simplifying
network management.
Intel Corporation, January [31], the purpose of this paper is to provide a foundation
for evaluating hubs as the shared-media architecture now face stiff competition from
switched-based technology. It considers the security and reliability issues as some
network connectivity products now add features such as redundant power supplies
and hot swapability to help eliminate downtime. Others supply intrusion,
eavesdropping protection and port locking features to maximize network security. It
also illustrates the cost of either devices because they will continue to play a critical
role in network infrastructure.
Clark Tom, this paper gives a comprehensive discussion about Fibre Channel hubs
which are wiring concentrators analogous to Ethernet and Token Ring hubs. These
hubs are called Arbitrated loop hubs because they were engineered in response to
problems that arose when Arbitrated Loops were built by simply connecting
transmit to receive among multiple devices. This allows a circular data path or loop
to be created, but poses significant problems for troubleshooting and adding or
removing devices. Hubs resolve these problems by collapsing the loop topology into
a star configuration. Arbitrated Loop hubs provide Port Bypass circuitry that
automatically reconfigures the loop if a device is removed or added. Fibre Channel
technology has a growing acceptance as a mean to solve wide variety of storage
problems.
4
EtherWAN Systems [15], this paper explains the three problems arise in migration
from standard Ethernet to Fast Ethernet which are: speeds not interchangable,
topology limitations, and single collision domain and how these problems can be
overcomed by a dual-speed hubs as a reasonable solution.
1.2 Aim of Thesis
This research aims to give a comparative study of three kinds of hubs both in terms of
functionality (Passive, Active, Intelligent, and Switching hubs) and in terms of configuration
(Stand-alone, Stackable, and Enterprise or Modular hubs). All hub features such as auto-
negotiation, jabber protection, and intrusion protection will be discussed along the text. As a
result, this thesis offers a comprehensive foundation for choosing the suitable kind of hub for a
given network specifications and requirements.
1.3 Thesis Layout This thesis is organized as follows
Chapter One
Gives an introduction to the research by explaining some general aspects of hub devices. It
also contains the relative work, aim of thesis, and thesis layout.
Chapter Two
This chapter provides a description of computer networks, their topology, architectures, media
alternatives, and connectivity devices. It also explains the hubs by introducing three kinds of
them in terms of configuration: stand-alone, stackable, and enterprise or modular hubs. Finally it
presents a table called Wiring Centers Technology Analysis contains the implications and
options used with hubs.
Chapter Three
Hub functionality is explained in this chapter. According to their functions, hubs can be
classified into three different categories: Passive, Active, Intelligent, and Switching hubs. This
chapter also discusses the dual-speed capability provided by some kinds of hubs. Along the text
the relationship between SNMP protocol and some network devices including hubs will be
explained. This chapter also examines some of security features found in advanced hub products
5
such as LAN Security Architecture (LSA) and intrusion and jabber protection. Also there is a
comparative table between the above types in order to conclude which is the best and how to
choose the suitable kind.
Chapter Four
This chapter presents the design and implementation of the proposed system. Among the
sections discussed in this chapter are the design process, system algorithms, implementation
process, system parts, and illustration of the system windows. This chapter finally contains the
result that lists all the security features founded in hubs then explaining the limitations of these
devices.
Chapter Five
Includes a discussion, conclusions, and the suggestions for future work.
6
2 Computer Networks and Hubs
2.1 Introduction
As continuing in the quest to build the perfect networking environment for any
organization, many decisions will be faced with this quest. One of the most basic yet most
important is the topology of the network. That decision sets the stage for everything that is
yet to come: what levels of performance and reliability can be expected, what kind of
administrative and support issues will have to be faced, how to scale or expand the network,
and how large a dent the network will make in the operating budget.
In many cases, the thought of having to purchase hubs prevents most people from building
10base-T networks. While a fear of the unknown is natural, the fear of hubs is sometimes
more like an uncontrollable phobia. If the user in the position of having to upgrade an
existing 10base-2 LAN, the additional cost of hubs should not stop from getting the
increased performance and flexibility of the infrastructure that hubs can offer. In fact,
the cost of a hub will depend on the type of hub decided to be purchased. [1]
Before examining the hubs with their associated features, it is better to have a brief look on
network topologies and find out and why a star topology is considered as the most common,
easy to use, and troubleshoot network topology. Then we'll discuss some common network
architectures that use the hubs such as Ethernet, Token Ring, and ARCnet. Some cable
types used within these network architectures will also be explained too. This chapter also
contains a brief illustration of network connectivity devices such as router, bridge, and
switch. After that we'll explain the hubs in more details.
2.2 Network Topology
The word topology is commonly used to discuss the properties of various types of
networks. Topology is the branch of mathematics that examines the characteristics of
geometric shapes. Networks have shapes, and the shape a network takes has much to do
with the way it functions. The following three types of physical topologies are frequently
used in computer networking: [5]
2.2.1 Bus Topology
The bus topology is a linear arrangement with terminators on either end and devices connected
to the "bus" via connectors and/or transceivers. The purpose of the terminator is to close off the
ends of the bus topology, thereby completing the electrical circuit and allowing the data signals
to flow. A bus topology without properly matched terminators will not work. The weak link in
7
the bus physical topology is that a break or loose connection anywhere along the entire bus will
bring the whole network down. [6]
2.2.2 Ring topology
In the ring topology, each PC connected is actually an active part of the ring, passing data
packets in a sequential pattern around the ring. If one of the PCs dies, or a network adapter
card malfunctions, the "sequence" is broken, the token is lost, and the network is down. In
addition, any cable breaks bring down the entire network. [6]
2.2.3 Star topology
The star physical topology avoids these two aforementioned potential problems by
employing some type of central management device. Depending on the network architecture
and sophistication of the devices, it may be called a hub, a wiring center, a concentrator,
MAU (Multiple Access Unit), a repeater, or a switching hub. By isolating each PC or node
on its own leg or segment of the network, any node or cable failure only affects that leg,
whereas, the remainder of the network continues to function normally. Because all network
data in a star topology are going through this one central location, it makes a marvelous spot
to add system monitoring, security, or management capabilities. Conversely, since all
network data are going through this one central location, it makes a marvelous networking
characteristic known as a single point of failure. Any node can be lost and the network will
be fine but hub loss will goes the whole network down.
Most modern cabling systems are designed in a star physical topology. Networks with star
wiring topologies can be significantly easier to trouble shoot and repair than bus or ring
wired networks. With a star network, a problem node can be isolated from the rest of the
network by simply disconnecting the cable and directly connecting it to the cable hub.
If the hub is considered "intelligent", management software developed for that hub type
could disconnect the suspect port. [6,5] Figure 2-1 highlights the differences between these
physical topologies.
Figure 2.2 Bus Topology Figure 2.1 Ring Topology
8
2.3 Network architecture
The following are the most popular network architectures used in computer networking:
2.4 Ethernet
provide multiple Ethernet ports. These devices are known as hubs since they provide the
central portion, or hub, of media system.
A newer variation of Ethernet, 10Base-T and 100Base-TX, are cabled using wiring hubs
(concentrators), as shown below in figure 2-2. Each station is connected to the hub via an
individual UTP (Unshielded Twisted Pair) cable.
Ethernet was originally developed by DIX - the Digital Corporation, the Intel Corporation,
and the Xerox Corporation in the early 1970s. Ethernet uses the CSMA/CD (Carrier Sense
Multiple Access with Collision Detection) media contention access method and supports a
maximum throughput of 10 or 100Mbps. Several varieties are available based on medium type
including:
10Base-5
A 10Mbps Ethernet standard for thick coaxial cable media
10Base-2
A 10Mbps Ethernet standard for thin coaxial cable media
10Base-T
A 10Mbps Ethernet standard for unshielded twisted pair cable media
10Base-F
A 10Mbps Ethernet standard for fiber optic cable media.
Figure 2.3 Star Topolgy
9
An older, common wiring system for Ethernet (10Base2) and (10Base5) uses coaxial cable
in a linear bus topology. Ethernet was designed to be easily expandable to meet the networking
needs of a given site. To help extend Ethernet systems, networking vendors sell devices that
Ethernet is generally used on light to medium traffic networks, and performs best when a
network's data traffic is sent in short bursts. Ethernet is the most popular network standard. It has
become especially popular in many university and government installations. [5,1,7]
2.5 Token ring
Token Ring is wired in a physical star to obtain the advantages of a central wiring hub. All
stations can be connected and disconnected at that central point, and the wiring hub can be
equipped with hub management and diagnostic systems. Therefore Token Ring sometimes
referred to as a star-wired-ring. Figure 2-3 depicts this network architecture. [5]
Token Ring uses a non-contention token-passing architecture. The topology is physically a star,
but logically uses a ring to pass the token from station to station. Each node must be attached to a
hub/concentrator called a Multistation Access Unit (MAU or MSAU). The MAU is the central
cabling component for IBM Token Ring networks. The 8228 MAU was the original wiring hub
developed by IBM for Token Ring networks.
Figure 2.4 Star Ethernet
Figure 2.5 Token Ring Architecture
10
2.5.1 ARCnet Architecture
Typical ARCnet installations are wired as a star. The most popular star-wired installations
of ARCnet run off two types of hubs:
Passive hubs cannot amplify signals. Each hub has four connectors. A port on a
passive hub can only connect to an active device (an active hub or an NIC). Passive
hubs can never be connected to a passive hub.
Active hubs have active electronics that amplify signals and split them to multiple
ports. The number of ports on an active hub varies with the manufacturer, but eight is
typical. A port on an active hub can be connected to a port on another active device
(such as another active hub or an NIC) or to a passive hub. Figure 2-4 illustrates
ARCnet architecture.
ARCnet is an acronym for Attached Resource Computer NETwork, which was founded
by the Datapoint Corporation. ARCnet operates at 2.5Mbps throughput and uses coax, twisted
pair, or fiber optic cabling to connect network devices. But an ARCnet network is used primarily
with either coax or twisted pair cable. UTP cable is simple to install and provides a reliable
connection to the workstations, whereas coax provides a means to span longer distances.
Figure 2.6 ARCnet Architecture
11
The figure above shows an ARCnet configuration using active and passive hubs. Active
hubs are required to extend the network for long distances and to configure networks that have
more than four nodes. Passive hubs are used as an economical means of splitting a port an active
hub to support three devices. [5].
2.6 Cable Types
Cables fall into two broad categories, electrical conductors and fiber optic, with various
types of cables available in each category. Prior to an examination of fiber optic cables, this
section examines two types of electrical cables: coaxial and twisted pair. [5]
2.6.1 Coaxial Cable
Coaxial cable, named from the two cable axes that run the length of the wire, is a versatile
and useful transmission medium. The cable consists of a solid or braided outer conductor
surrounding either a solid or a stranded inner conductor. The conductors are usually
separated by a dielectric material, and the entire wire is covered with an insulating jacket.
Coaxial wire allows for greater shielding from interference and greater segment distances.
Coaxial 10base-5/2 has a transmission rate of 10Mbps. 10base-5 has a maximum segment
length of about 500m/segment, whereas 10base-2 is about 180m/segment. Figures 2-5
shows a breakdown of coaxial cable.
Figure 2.7 Coaxial Cable
12
As the diameter of the coaxial cable increases, the data pipeline increases and so does the
transfer rate. But larger wires are also expensive and require special installation tools, thereby
making the installation of large-circumference coaxial cable cost-prohibitive. [1]
TP is normally used to carry data at speeds from 10Mbps to 100Mbps, but the speed can be
decreased by a number of error characteristics such as data loss or electromagnetic interference
(EMI).
Category Specifications for TP
The five major categories of TP cable are listed below:
Category 1 Category 1 wiring is mainly used to carry voice. Category 1 is not certified
to carry data of any type
Category 2 Category 2 wiring is used to carry data at rates up to 4Mbps. This type of
wiring is popular for older token-based networks utilizing the 4Mbps specification of
the token-passing protocol.
Category 3 it is used primarily in older Ethernet 10base-T LANs and is certified to
carry data at 10Mbps.
Category 4 Category 4 wiring is used primarily when implementing token-based or
10base-T/100base-T networks. CAT4 is certified at 16Mbps and consists of four
twisted wires.
Category 5 Category 5 wiring is the most popular Ethernet cabling category. It is
capable of carrying data at rates up to 100Mbps and is used for 100base-T and 10base-
T networks. [1]
2.6.2 Twisted Pair Cable
Fiber optic cable is a thin, flexible medium that carries data in the form of light waves
through a glass "wire" or cable. This transfer medium works for distances exceeding the 1-
kilometer range and is extremely secure (there is no electric signal to tap). Fiber optic cables
come in two varieties: single mode and multimode.
The composition of fiber optic cable is similar to that of the coaxial cable. It has a solid core
made up of one strand of ultra-thin glass or sheathed in a plastic covering (cladding), which
reflects the light back into the cable's core. The cladding is covered by a concentric layer of
thin plastic (jacket) that protects it. When there is more than one fiber, the fibers are
grouped together into a bundle and covered with another thin layer of plastic. Figure 2-7
shows a diagram of fiber optic cable. [1]
2.6.3 Fiber Optic
Cable
The Open System
Figure 2.8 Fiber Optic Cable
13
Interconnection (OSI) reference model describes how information from a software application in
one computer moves through a network medium to a software application in another computer.
The OSI reference model is a conceptual model composed of seven layers, each specifying
particular network functions. The model was developed by the International Organization for
Standardization (ISO) in 1984, and it is now considered the primary architectural model for
inter-computer communications.
The OSI model divides the tasks involved with moving information between networked
computers into seven smaller, more manageable task groups. A task or group of tasks is
then assigned to each of the seven OSI layers. Each layer is reasonably self-contained so
that the tasks assigned to each layer can be implemented independently. This enables the
solutions offered by one layer to be updated without adversely affecting the other layers.
Figure 2-8 lists the seven layers of the OSI reference model:
2.7 Open System Interconnection Reference Model
The Open System Interconnection (OSI) reference model describes how information from a
software application in one computer moves through a network medium to a software
application in another computer. The OSI reference model is a conceptual model composed
of seven layers, each specifying particular network functions. The model was developed by
the International Organization for Standardization (ISO) in 1984, and it is now considered
the primary architectural model for inter-computer communications.
The OSI model divides the tasks involved with moving information between networked
computers into seven smaller, more manageable task groups. A task or group of tasks is
then assigned to each of the seven OSI layers. Each layer is reasonably self-contained so
that the tasks assigned to each layer can be implemented independently. This enables the
solutions offered by one layer to be updated without adversely affecting the other layers.
Figure 2-8 lists the seven layers of the OSI reference model:
Figure 2.9 OSI Reference Model
14
Host layers: (layers 7, 6, 5, and 4) provide accurate data delivery between computers:
Application Layer: This layer provides services to application processes such as
electronic mail and file transfer.
Presentation Layer: This layer ensures that information sent by the application layer
of one system would be readable by the application layer of another.
Session Layer: This layer establishes, manages, and terminates sessions between
applications.
Transport Layer: This layer is responsible for reliable network communication
between end nodes.
Media Layers: (layers 1, 2, and 3) controls physical delivery of the message over the network:
Network Layer: This layer provides connectivity and path selection between two end
systems. The network layer is the layer at which routing occurs.
Data Link Layer: This layer provides reliable transit of data across a physical link.
Physical Layer: The physical layer defines the electrical, mechanical, procedural, and
functional specifications for activating, maintaining, and deactivating the physical link
between end systems. [8,9].
2.8 Connectivity Devices
Networks connect to other networks through repeaters, bridges or routers. A repeater
corresponds to the physical layer and always routes signals from one network segment to
another. Bridges route using the data link layer and routers route using the network layer.
Figure 2-10 illustrates the three interconnection types. [10] .
Figure 2.10 Repeaters, Bridges, and Routers
15
2.8.1 Router
Routers join two networks that may or may not be similar. They function in the network
layer of the OSI Model. The purpose of the router is to choose the best route between two
networks that have multiple paths between them. A router knows its own location as well as
a packet of data's final destination. It looks in a routing table to identify the best path. [11]
2.8.2 Bridge
The purpose of a bridge is to link two geographically distant but similar networks that use the
same protocol. Bridges operate at the data link layer of the OSI model. They are a combination
of both hardware and software. A typical bridge consists of a box that sits between two networks
and has its own processor, memory, and software; its operations are transparent to the network
user. A bridge performs a filtering and forwarding functions. If the destination address in the
routing table (internal to the bridge) is on the same network segment as the source address, the
bridge automatically discards the data packets. The bridge can discard the packet because the
station to which it is addressed will already have received the packet. Packets can be delivered
without the help of the bridge. It passes only packets addressed to computers on the opposite side
of the bridge. The process is called filtering. If the destination address is in the internal routing
table but not on the same network segment, the bridge determines the port associated with the
address and forwards the packet to that port. This process is called forwarding. [11]
2.8.3 Switch
This refers to a hub that directs network packets to the port they are intended for, without
broadcasting them to all connections. Switched 10Base-T can move data faster than 100Base-T
hub, because the 100Base-T hub takes up the hub's entire bandwidth with each packet sent.
Switches operate at the Data Link layer of the OSI Model [11]
2.8.4 Repeater
All types of network connections suffer from attenuation and pulse distortion; for a given cable
specification and bit rate, each has a maximum length of cable. Repeaters can be used to increase
the maximum interconnection length. A repeater, as its name would imply, merely "repeats" each
bit of digital data that it receives. This repeating action actually "cleans up" the digital signals by
retiming and regenerating them before passing these repeated data from one attached device or
LAN segment to the next. Repeaters can only link devices or LAN segments of similar network
architectures. Repeaters function at the Physical layer of the OSI Model. [10,6]
2.8.5 Hub
Hubs are a subset of repeaters that allow attachment of single devices rather than LAN segments
to each hub port. The terms hub and concentrator or "intelligent concentrator" are often used
interchangeably. Distinctions can be made between these broad classes of wiring centers. A hub
is often the term reserved for describing a stand-alone device with a fixed number of ports,
16
which offers features beyond that of a simple repeater.The type of media connections and
network architecture offered by the hub is determined at the time of manufacture as well. For
example, a 10BaseT Ethernet hub will offer a fixed number of RJ-45 twisted pair connections for
an Ethernet network. Additional types of media or network architectures are not usually
supported. Hubs operate at the physical layer of the OSI Model. [6]
2.9 Shared Media LAN Wiring Centers
The most common network physical topology employed today is the star topology, and the
heart of the star topology is the wiring center. A wiring center may be alternatively known
as a hub, a concentrator, a repeater, a MAU, or a variety of other terms. In this section and
the sections that follow, wiring center functionality, configurations, and technology will be
examined for shared-media network architectures. [6]
2.9.1 Networks and Hubs
As its name implies, a hub is a center of activity. In more specific network terms, a hub, or
concentrator, is a common wiring point for networks that are based around a star topology.
ARCnet, 10base-T, as well as many other proprietary network topologies, all rely on the use
of hubs to connect different cable runs and to distribute data across the various segments of
a network. Hubs basically act as a signal splitter. They take all of the signals they receive in
through one port and redistribute it out through all ports.
Some hubs actually regenerate weak signals before retransmitting them. Other hubs retime the
signal to provide true synchronous data communication between all ports. Figure 2-11 shows
what a basic 10base-2 network might look like and the way the machines are connected to each
other. The data being sent from the first system in the chain must be handled by each system
between the originating and destination systems.
Figure 2.11 Basic 10Base-2 Network
17
Figure 2-12 shows the same network as Figure 2-11 if it were built using 10base-T. It illustrates
how the topology is different and how a hub fits into the network topology
For example, on a 10base-T network, all of the devices will be physically wired to one or
more hubs using UTP/STP cabling. A hub will have multiple ports and possible multiple types of
ports so that can connect many devices to it. In case of connecting multiple hubs together, one of
the other higher-speed ports can be used on the hubs to build a backbone to the network. Each
hub and possibly the network servers should be connected directly to this high-speed backbone.
Because the majority of communication on most LANs is between workstations and the
primary servers, the backbone of network wire or segment will play a very important part in the
overall performance of the network. Figure 2-13 shows how the backbone connects the multiple
hubs and servers directly over a dedicated connection. That dedicated connection ideally should
be high-speed Ethernet or some other kind of high-speed connection, possibly fiber optic. [1]
Figure 2.12 Building 10Base-T Network using the Hub
18
Figure 2.13 Connecting Multiple Hubs to form Network Backbone
2.9.2 Basic Specifications
All hubs have a basic set of features that is determined in part by the types of cabling that run to
the hub. In many respects, a hub is simply another network device that must perform within the
standard parameters of the particular type of network to which the hub is connected. Despite the
fact that hubs provide additional services to a network than simply an interface, they must still
follow the restrictions placed on the medium by the IEEE.
The majority of connections to most hubs are through RJ-45 jacks. RJ-45 jacks are the
standard connector type for many kinds of Ethernet that rely on twisted-pair cabling. From
10base-T to 100base-T, the cabling that runs from most workstations, printers, and other
devices on the LAN to the hub is more than likely some type of twisted-pair cable,
depending on the speed of the network. At either end of that cable is the RJ-45 connector.
The length of each cable run to a hub is limited by the medium in use. Table 2-1, For
example, outlines some LAN technologies, their estimated speed, and their maximum
segment lengths. As illustrated in the table, any length of 10base-T cabling cannot exceed
100 meters or roughly 330 feet in length. This is a limitation in the specification of 10base-
T from the IEEE, not a limitation of any particular hub. For example, if the hub has a
10base-F connector to connect the hub to a high-speed backbone, the maximum run of that
connection may be as far as 2 kilometers as defined by the IEEE specification for 10base-F.
Table 2-1 LAN Technologies Comparison Quick Reference Chart
Technology
Speed
(Mbps)
Maximum Segment
Length (meters)
Token Based
Token Ring 4, 16 100
Simple Ethernet
10Base-T 10 100
19
10Base-F (Multimode) 10 Up to 2,000
10Base-F (Singlemode) 10 Up to 25,000
10Base-5 10 500
10Base-2 10 185
Fast Ethernet
100Base-T4 100 100
100Base-TX 100 100
100Base-FX (Multimode) 100 412 (half duplex)
2,000 (full duplex)
100Base-FX (Singlemode) 100 20,000
Gigabit Ethernet
1000Base-T (UTP) 1000 100
1000Base-T (fiber-singlemode) 1000 3,000
1000Base-T (coax) 1000 25
Since hubs are electronic devices that take a single signal and broadcast it to multiple ports,
hubs need a power source. Most hubs have LEDs that can be used to monitor various conditions.
The two most common are LEDs to monitor power and active connections at particular ports.
Other hubs have additional LEDs to monitor traffic on a particular port, as well as packet
collisions on the LAN in general. [1]
2.9.3 Multi-station Access Units (MAUs)
A MAU is IBM's name for a Token Ring Hub. A MAU is manufactured with a fixed
number of ports, and connections for unshielded or shielded twisted pair. MAUs typically
have eight ports with two additional ports labeled RI (Ring In) and RO (Ring Out). These
specialized cascading ports allow multiple MAUs to be linked in single logical ring. MAUs
may also be cascaded to each other via fiber optic cable as opposed to shielded twisted pair.
20
MAUs offer varying degrees of management capability. Active Management MAUs are
able to send alerts to management consoles regarding malfunctioning Token Ring adapters
and can also forcibly remove these misbehaving adapters from the ring. Removing
malfunctioning nodes is especial critical in Token Ring LANs due to the possibility of one
of the malfunctioning nodes becoming disabled while holding onto the token. Although
such an event would be at the very least inconvenient, it would not be catastrophic since the
active monitor workstation is capable of regenerating a new token. [6]
2.10 Wiring Center Categories
In terms of configuration and features, wiring centers can be separated into three broad
categories:
Stand-alone hubs
Stackable hubs
Enterprise (Modular) hubs
2.10.1 Stand-alone Hubs
They are fully configured hubs offering a limited number (12 or fewer) ports of a particular
type of network architecture (Ethernet or Token Ring) and media. They are fully configured
and include their own power supply but are not generally expandable, do not include
management software, and are the least expensive of the three wiring center categories. Stand-alone hubs usually include some method of linking them to other stand-alone hubs,
either by connecting them together with a length of 10Base-5 coaxial cable or cascading
them using twisted pair between individual ports on each hub. Stand-alone hubs are best
suited for small, independent workgroups, departments, or offices typically with fewer than
12 users per LAN.
In figure 2-14 below we see that network A has four 100Base-TX* hubs connected together
by a single cable. This cable could be a coaxial or fiber optic cable. All hubs are part of a
single LAN. Network B illustrates two 100Base-TX hubs cascaded. Here the cable
connecting the two ports is unshielded twisted pair (CAT5) wire. All of the hubs that are
cascaded in this fashion are also part of a single LAN. [6,5] .
21
2.10.2 Stackable Hubs
These types of hubs add expandability and manageability to the basic capabilities of the
stand-alone hub. Stackable hubs can be linked together, or cascaded, to form one larger virtual
hub of a single type of network architecture and media.
Historically, the stackable concept has been the preferred method of moving data between
different nodes or devices on a network. When originally introduced in the form of a network
hub, the stacking solution proved immediately successful for many reasons including those of
flexibility and price. Although a later arrival to the market than its chassis based predecessor, the
stackable hub soon became the standard in the 802.x Ethernet hub market.
Hubs may be cascadable or stackable via cascading ports which may be specialized ports
on the hub or may be switch
configurable "normal" ports
allowing repeated data to
flow out of a cascading port to the next hub rather than the normal inbound-only port traffic
flow. In general, cascading ports are proprietary in nature, thereby making it impossible to
cascade hubs of different vendors together.
Specialized hub-to-hub cascading cables may also be required and the
maximum allowable distance between stackable hubs may vary as well. Stackable
hubs also vary as to stackability, with the number of stackable hubs ranging from
4 to 20 and the total number of stacked ports ranging from 48 to 768.
Given the larger number of ports, management software becomes essential. Most stackable
hubs offer some type of local management software as well as links to enterprise management
software platforms such as HP Open-View, Sun's SunNet Manager, IBM NetView, Novell's
ManageWise, and Microsoft SMS (System Management Server).
When they are linked together, stackable hubs act like a modular hub that they can be
managed as a single unit. One manageable hub, used within a stack can typically provide the
management for all other hubs in the stack. These hubs are ideal when an organization wants to
start with minimal investments but knows that its LAN will grow. By utilizing stackable hubs, an
organization doesn't need to invest in a large chassis, which may only have one or two cards in it
for a considerable length of time until more are needed. [6,12,5]
2.10.3 Enterprise Hubs
Also known as Modular Concentrators, differ from stackable hubs in both physical design and
offered functionally. Rather than being fully functional self-contained units, enterprise hubs are
modular by design, offering a chassis-based architecture to which a variety of different modules
(or communications card) can be inserted. In some cases, these modules can be inserted and/ or
removed while the hub remains powered-up, a capability known as host-swappable.
Figure 2.14 Cascading Stand-alone Hubs
22
Each module acts like a stand-alone hub; when the communications modules are placed in
the card slots in the chassis, they connect to a communications backplane that links them
together so that a station connected to a port on one module can easily communicate with a
station on another module. Among the possible modules supported by enterprise hubs are:
Ethernet, Fast Ethernet, Gigabit Ethernet, Token Ring, and FDDI
port modules in a variety of port densities and media choices.
Management modules
Router modules
Bridge modules
WAN link modules
Multiple power supplies for redundant power
The modular hub can be equipped with a wide variety of connectivity and network
management modules designed to provide customized solution for the creation of enterprise-
wide LANs and WANs
Modular hubs typically range in size from four to 14 slots, so the network can be easily
expanded. Typically, several slots in a modular hub will be filled with 10Base-T Ethernet
modules. For instance, with 10 modules, each supporting 12 users, a single hub could support
120 users over 10Base-T. The modules are linked by the high-speed backplane, which can also
be used to connect the communications modules to a management module that manages all of
the cards in the chassis.
In addition to using one management module for a large number of ports, all of the
modules share a common power supply. Another advantage of some modular hubs is that
Ethernet, Token Ring, and even FDDI communications modules can be placed in the same
chassis, using the same common power supplies.
These broad category definitions and labels are not standards and are not universally
adhered to by manufacturers. Signaling standards defined as part of IEEE or ANSI LAN
standards allow hubs and NICs of different vendors to interoperate successfully in the most
cases. Figure 2-15 differentiates between the functionality of the major categories of wiring
centers, whereas figure 2-16 illustrates some of the physical differences between the three major
categories of hubs. [6,5]
23
Figure 2.1515 Wiring Centers Functional Comparison
Figure 2.16 Stand-alone hub
Figure 2.17 Stackable hub
24
2.11 Wiring Centers Technology Analysis
Table 2-2 Some of the major technical features to be used for comparative analysis are listed
below in table 2-2. Before purchasing a wiring center of any type, the implications of
various possible features listed in the Wiring Center Technology Analysis may be useful to
consider. [6]
Wiring Center Characteristic Implications / Options
Expandability Most stand-alone hubs are neither expandable nor casadable.
Stackable hubs are cascadable and enterprise hubs are expandable by
adding more LAN modules. Enterprise hubs vary in the number of open
slots from approximately 5 to 20. Total backplane capacity (speed) is
important because this is the shred network media that must be
shared by all attached modules.
Network Architectures Options: Ethernet, Token Ring, FDDI, AppleTalk, 100Base-T, 100VG-
AnyLAN. Not all enterprise hubs have all types of network architecture
modules available.
Internetworking Are bridging and/or routing modules available that can redirect traffic
from module to module? Across which different types of network
Figure 2.18 Enterprise hub
25
architecture modules will traffic need to be bridged?
Reliability Is an integrated UPS included? Are power supplies redundant? Are
modules hot-swappable? Are cooling fans redundant? Which
components are capable of being replaced by the user?
Management Is the local hub management program available? Are SNMP
management protocols supported? Is monitoring software available?
What security services available? Can ports be remotely
enabled/disabled? Can the hub be controlled by a port attached
workstation or only by a special management console? Are
management statistics and alarms graphically displayed? What
operating systems can the management software run on? Options:
DOS, OS/2, Windows, Windows NT, UNIX, etc. Can a map of the
network be displayed? Which enterprise network management
systems are supported? Options: HP Open View, IBM NetView, Sun
SunNet Manager, Novell ManageWise.
3 Functional and Security Features in Hubs
3.1 Introduction
Hubs provide a crucial function on networks with a star topology. The hub is one of the
most important elements of a LAN. It is the central connection point for wiring the network, and
all stations on the LAN are linked to each other through the hub. There are many different types
of hubs, each offering specific features that allow varying levels of service. Technically
speaking, three different types of hubs exist:
Passive hubs
Active hubs
Intelligent hubs
In the following sections, we talk about some of the standard features of most hubs, the
differences between Passive, Active, Intelligent, and Switching hubs, as well as some of the
additional features found in today's more high-performance hubs. Also we discuss the concept of
dual-speed hubs and auto-negotiation feature, an important feature that help in migration from
traditional Ethernet to higher-speed network architecture
26
Fast Ethernet. This chapter also contains an illustration of SNMP (Simple Network
Management Protocol) which is a protocol used in hubs and other connectivity devices to
provide network management.
Some of the hub products manufactured by some companies such as 3Com and IBM will
be explained along with their relative features and to which type of hubs they are belong. Also
there will be a comparison between the 3 types of hubs in terms of functionality to know which
is the best and to give a good basis in choosing the right hub for a given kind of network.
[1,13,5]
3.2 Passive Hubs
Passive hubs, as the name suggests, are rather quiescent creatures. They do not do very
much to enhance the performance of the LAN, nor do they do anything to assist in
troubleshooting faulty hardware or finding performance bottlenecks. They simply take all of
the packets they receive on a single port and rebroadcast them across all ports, the simplest
thing that a hub can do.
A passive hub is a simple signal splitter. Its main function is to connect the arms of the star
while maintaining the proper electrical characteristics. Passive hubs do not amplify the
electrical signal of incoming packets before broadcasting them out to the network. They
route all traffic to all nodes. This means that a tremendous load can be created when much
communication takes place between computers. Every computer has the additional burden
of reading the address of each piece of information it receives to determine if the
information is intended for that computer. Information containing other addresses are
discarded
Passive hubs commonly have one 10base-2 port in addition to the RJ-45 connectors that
connect each LAN device. As mentioned earlier in section 2.3.1, 10base-5 is 10Mbps
Ethernet that is run over thick coax. This 10base-2 connector can be used as a network
backbone. Other, more advanced passive hubs have AUI* ports that can be connected to the
transceiver of the choice to form a backbone that may be found more advantageous.
Most passive hubs are excellent entry-level devices that can be used as the starting points in
the world of star topology Ethernet. In case of upgrading from 10base-2, even the most
inexpensive 10base-T setup will deliver a whole new world of performance. [1,13,5]
3.3 Active Hubs
Active hubs actually do something other than simply rebroadcasting data. Generally, they
have all of the features of passive hubs, with the following additional features.
1. Watching the data being sent out. Active hubs take a larger role in Ethernet
communications by implementing a technology called store and forward where the hubs
actually look at the data they are transmitting before sending it. This is not to say that the
hub prioritizes certain packets of data; it does, however, repair certain "damaged" packets
and will retime the distribution of other packets.
27
2. If a signal received by an active hub is weak but still readable, the active hub restores the
signal to a stronger state before rebroadcasting it. This feature allows certain devices that
are not operating within optimal parameters to still be used on the network. If a device is
not broadcasting a signal strong enough to be seen by other devices on a network that uses
passive hubs, the signal amplification provided by an active hub may allow that device to
continue to function on the LAN.
3. Some active hubs will report devices on the network that is not fully functional. In this
way, active hubs also provide certain diagnostic capabilities for the network.
4. Active hubs will also retime and resynchronize certain packets when they are being
transmitted. Certain cable runs may experience electromagnetic (EM) disturbances that
prevent packets from reaching the hub or the device at the end of the cable run in timely
fashion. In other situations, the packets may not reach the destination at all.
5. Active hubs provide certain performance benefits and, sometimes, additional diagnostic
capabilities. Active hubs are more expensive than simple, passive hubs and can be
purchased in many configurations with various numbers and types of ports. Some people
use the term concentrator when referring to a passive hub and multiport repeater when
referring to an active hub. [1,13]
6. Active hubs can compensate for packet loss by retransmitting packets on individual ports
as they are called for and retiming packet delivery for slower, more error-prone
connections. Of course, retiming packet delivery slows down overall network performance
for all devices connected to that particular hub, but sometimes that is preferable to data loss
especially since the retiming can actually lower the number of collisions seen on the LAN.
If data does not have to be broadcast over and over again, the LAN is available for use for
new requests more frequently. Again, it is important to point out that active hubs can help
in diagnosing bad cable runs by showing which port on the hub warrants the retransmission
or retiming.
3.4 Intelligent Hubs
Routers, bridges, and switches are examples of hub devices that can route transmissions
intelligently. Intelligent hubs also can incorporate diagnostic features that make it easier to
troubleshoot network problems. It also typically includes remote management support via
SNMP. [1,13,5]
In addition to all of the features found in active hubs, incorporating intelligent hubs into the
network infrastructure gives the following abilities:
1. Managing the network from one central location. If a problem develops with any device on
a network that is connected to an intelligent hub, the problem can be easily identified,
diagnosed, and remedied using the management information provided by each intelligent
hub, that is, in the event it is a problem that cannot be remedied by the hub itself. This is a
significant improvement over standard active hubs. Troubleshooting a large enterprise-
scale network without a centralized management tool that can help to visualize the network
infrastructure usually leaves running from wiring closet to wiring closet trying to find
poorly functioning devices.
2. Another significant and often overlooked feature of intelligent hubs is their ability to offer
flexible transmission rates to various devices. Of course, intelligent hubs have additional
28
ports for connecting high-speed backbones just like other types of hubs. However, the
intelligent hubs support standard transmission rates of 10, 16 and 100Mbps to desktop
systems using standard topologies such as Ethernet, Token Ring or FDDI. This means that
the system can be gradually upgraded from 10Mbps connections to 100Mbps connections,
or simply deliver faster transmission speeds to devices that need faster services.
3. In addition, to boost the flexibility in configuration and management of networks of mixed
media and mixed levels of technology, intelligent hubs have incorporated support for other
technologies such as terminal servers, bridges, routers, and switches. Additionally, modern
intelligent hubs provide more comprehensive and easier-to-use network management
software, which make them a crucial component of most comprehensive network
management systems.
4. Intelligent hubs add extra features to an active hub that are of particular importance to
businesses. An intelligent hub typically is stackable (built in such a way that multiple units
can be placed one on top of the other to conserve space).
5. They can make informed path selections and perform some network management.
Intelligent hubs route traffic only to the branch of the star on which the receiving node is
located. If redundant paths exist, an intelligent hub can route information around normally
used paths when cable problems occur.
Intelligent hubs offer many advantages over passive and active hubs. Organizations
looking to expand their networking capabilities so users can share resources more efficiently and
function more quickly can benefit greatly from intelligent hubs. The technology behind
intelligent hubs has only become available in recent years and many organizations may not have
had the chance to benefit from them; nevertheless intelligent hubs are a proven technology that
can deliver unparalleled performance for the LAN.
3.4.1 Modular design
The terms concentrator, intelligent concentrator, smart hub or enterprise hub are often
reserved for a device characterized by its flexibility and expandability. A concentrator starts with
a fairly empty, boxlike device often called a chassis. This chassis contains one or more redundant
power supplies and a "built-in" network backbone. This backbone might be Ethernet, Token
Ring, FDDI, AppleTalk, 100Base-T, 100VG-AnyLAN, or some combination of the above. Into
this "backplane" individual cards or modules are inserted.
For instance, an 8 or 16 port twisted pair Ethernet module could be purchased and slid into
place in the concentrator chassis. A network management module supporting the SNMP
network management protocol could then be purchased and slid into the chassis next to the
previously installed 10Base-T Port module. In this "mix and match" scenario,
additional cards could be added for connection of PCs with Token Ring
adapters or PCs or workstations with FDDI adapters.
These modules are most often hot-swappable, allowing modules to be added
or removed without shutting down the entire enterprise hub. Obviously, the
capacity of these enterprise hubs is equally as important as the flexibility afforded
29
by the modular design. In fact, several hundreds ports of varying network
architectures are often supported by enterprise hubs.
This "network in a box" is now ready workstations to be hooked up to it through twisted
pair connections to the media interfaces on the network interface cards of the PCs or
workstations. Allowing different media types to be intermixed in the concentrator was one of its
first major selling points. Ethernet can run over UTP, STP, Thick and Thin Coax as well as Fiber
Additional modules available for some concentrators may allow data traffic from this
"network in box" to travel to other local LANs via bridge or router add-on modules. These
combination concentrators are sometimes called Internetworking Hubs.
Communication to remote LANs or workstations may be available through the addition of
other specialized cards, or modules, designed to provide access to Wide Area Network services.
Whereas, all local network traffic travels through this single enterprise hub, it is also an ideal
location for security modules to be added for either encryption or authentication functionality.
Backplane design within enterprise hubs is proprietary and, as a result, the modules for
enterprise hubs are not interoperable. Therefore, it is important to ensure that the enterprise hub
to be purchased has available all types of modules in terms of network architecture, media type,
management, internetworking, WAN interfaces, or security. [6]
3.4.2 Structured Wiring Architecture
Management of larger networks and internetworking begins with "structured wiring". With
structured wiring, all of the network stations are physically star wired to intelligent hubs.
Intelligent hubs are hubs that can be monitored and managed by network operators. This
combination of a star topology and intelligent hubs make troubleshooting and fault isolation
easier and faster because each endstation is attached to the network on its own individual
port, which means it can be monitored easily and, if necessary, can be easily turned off.
In addition, structured wiring makes adding users to the network, moving them, or making
other physical changes on the network very simple. Since both Ethernet and Token Ring
networks can use twisted pair cable and can be configured in a physical star topology, a
structured wiring architecture will support either network technology.
The cornerstone of the network is the intelligent hub, or concentrator, which serves as the
control point for systems activity, management, and growth. By integrating any
combination of connectivity, internetworking, and management capabilities into intelligent
hubs, network managers can create the perfect physical network infrastructure for their
environment
The term concentrator is generally associated with 10BASE-T/100Base-TX Ethernet
networks, while the term Multistation Access Unit (MAU) is used to refer to the Token Ring
wiring hub. Just as these two LAN technologies use different media access methods,
30
concentrators and MAUs perform different media access functions internally, but at one level
they perform the same function: They are both network wiring hubs.
A typical hub has multiple user ports to which computers and peripheral devices such as
servers are attached. Each port supports a single 10BASE-T/100Base-TX twisted pair connection
from a network station. When an Ethernet packet is transmitted to the hub by one station, it is
repeated, or copied, over onto all of the other ports of the hub. In this way, all of the stations
"see" every packet just as they do on a bus network, so even though each station is connected to
the hub with its own dedicated twisted pair cable, a hub-based network is still a shared media
LAN. [5]
3.5 Switching Hubs
From all the previous sections we can provide the following table, which lists the features
for each kind of the above mentioned hubs: [6]
A Switching hub, or LAN switch, seeks to overcome this "one-at-a-time" broadcast scheme
which can potentially lead to data collisions, retransmissions, and reduced throughput
between high-bandwidth-demanding devices such as engineering workstations or server-to-
server communications.
The Ethernet switch is actually able to create connections, or switch, between any two
attached Ethernet devices on a packet-by-packet basis in as little as 40 milliseconds. The
"one-at-time" broadcast limitation previously associated with Ethernet is overcome with an
Ethernet switch. Ethernet is not the only network architecture for with LAN switches are
available. Either stand-alone versions or slid-in modules for enterprise switches are also
available for Token Ring, FDDI, and Fast Ethernet.
In addition, many high-end LAN switches also support ATM (Asynchronous Transfer
Mode) which is a type of switching that allows not only the previously mentioned LAN
network architectures to be switched extremely quickly but can also switch voice, video,
and image traffic equally well. In fact ATM can switch any type of digital information over
LANs or WANs with equal ease and speeds that are currently in the gigabit/second range.
Super-Switches or Mega-Switches support multiple different LAN architectures, ATM, as
well as interface to WAN services. The "network in a box" or "backbone in a box" offered by concentrators and hubs shrinks
the length of the network backbone but doesn't change the architectural characteristics of a
particular network backbone. For instance, in an Ethernet concentrator, multiple
workstations may access the built-in Ethernet backbone via a variety of media, but the basic
rules of Ethernet such as CSMA/CD access methodology at 10Mbps still control
performance on this "Ethernet in a box". Only one workstation at a time can broadcast its
message onto the shared 10Mbps backbone.
Table 3-1 Features of Passive, Active, Intelligent and Switching Hubs.
Function: signal splitter, they do not amplify the signal before
31
Passive Hubs rebroadcasting. They route all traffic to all nodes.
Traffic Optimization: tremendous load can be created when
there is much communication between computers.
Price: the most inexpensive.
Active
Hubs
Function: implement Store and forward technique (repair
damaged packets) and retime the distribution of other
packets.
Diagnostic capabilities: report devices that are not fully
functional and diagnose bad cable runs.
Packet loss: compensate by retransmitting packets on
individual ports as they are called.
Price: more expensive than passive hub.
Intelligent
Hubs
Function: informed path selection, route traffic only to the
branch of the star on which the receiving node is located.
Gives the ability to manage the network from one central
location.
Offer flexible transmission rates to various devices: 10, 16,
and 100Mbps.
Have incorporated support for many technologies such as
Ethernet, Token Ring, and FDDI.
Include remote management support via SNMP.
Switching
Hubs
Function: create switched connections between any two
attached devices.
Overcome "one-at-a-time" broadcast scheme adherent to
Ethernet networks.
Support multiple LAN architectures.
Available in stand-alone and modular versions.
Support ATM.
32
Support an interface to WAN services.
3.6 The 10/100Mbps Dual-Speed Hub
With the maturity of Fast Ethernet technology and constantly declining cost, more and more
users select Fast Ethernet as their choice of network infrastructure. For the majority 10Mbps
Ethernet network users, in their process of migrating to 100Mbps Fast Ethernet network,
there must be some kind of “co-existence” transition period for both 10Mbps and100Mbps
network. Certain degree of inconvenience is unavoidably created by such co-existence of
10Mbps and 100Mbps network. For example, a switch is required to connect hubs running
at different speed and a wiring adjustment may be needed to accommodate cable
requirements.
Further more, users may be forced to take significant change and investment because of the
difference between traditional Ethernet and Fast Ethernet which causes existing network
structure and topology obsolete. From the second half of 1997 network equipment
manufacturers start to promote Dual-Speed hub to address these practical problems.
[14,15,16]
3.6.1 The Difference between Ethernet and Fast Ethernet
Two major problems encountered in the upgrading to a pure 100Mbps or a co-existing
network are:
3.6.1.1 Network wiring adjustment
If all users are upgraded to 100Mbps simultaneously, we can simply replace the 10Mbps
hubs with 100Mbps hubs. However, in a gradual upgrade situation, we need to move some
users to 100Mbps hubs while keep the rest intact in the 10Mbps hubs. In this case, we need
to add a switch to connect both 10Mbps hubs and 100Mbps hubs as illustrated in
Figure 3-1.
Figure 3.1 Adding a Switch to Adjust Network Wiring
33
3.6.1.2 Network structure adjustment
In addition to the cable quality, topology is another big difference between Ethernet and
Fast Ethernet. In the 10Mbps Ethernet network configuration and in order to remain within
IEEE 802.3 10Mbps Ethernet rules, the maximum length of cable between the hub and an
attached device must not exceed 100 m (328 ft). No more than four 10Mbps hubs between
any two devices on the network can be connected together in a series as shown in Figure 3-
2. This Ethernet specification is known as 5-4 rule. In another word, the 5-4 rule for
10Base-T states that five 100-meter link segments and four hubs can be installed between
any two end stations located on the same LAN segment or collision domain.
As for Fast Ethernet network configuration and in order to remain within IEEE 802.3
100Mbps Fast Ethernet rules, the maximum length of cable between the hub and the
attached device must also not exceed 100 m (328 ft). But no more than two 100Mbps hubs
between any two devices on the network can be connected together in a series by a cable
with a maximum length of 5 m. So that the total cable distance between the two devices
does not exceed 205 m (672.4 ft) as shown in figure 3-3. This is known as Class II rule
associated with Fast Ethernet.
To accommodate the higher transmission speed and the need of shorter collision
detection response time in the Fast Ethernet, the 5-4 rule is replaced with Class II specification
that allows only two Fast Ethernet hubs linked together within a maximum diameter of 5 meters.
Such restriction totally changes the topology as illustrated in Figure 3-3.
Figure 3.2 The 5-4 Rule used in 10Mbps Ethernet
Figure 3.3 Class II Rule used in 100Mbps Fast Ethernet
34
A 10Mbps Ethernet network built with several hubs daisy-chained under 5-4 rule can not
be upgraded to 100Mbps Fast Ethernet by simply replacing the hubs, additional investment in
Fast Ethernet switch or even adjustments in the network structure and wiring are required. The
emergence of dual-speed hub provides users the investment protection and solutions for above
problems. [14,15]
3.6.1.3 Different Types of Dual Speed Hubs
Dual-speed hubs were introduced for more than five years, no uniform standard is defined
but with different specifications from different manufactures, but they can be generally
categorized as:
Manual Switch
This is the earlier design that relies on manual switch to change operating speed. These
dual-speed hubs operate at either 10Mbps or 100Mbps, can not support both speeds
simultaneously. They are designed mainly to protect user’s investment not address the upgrade
application problems.
Auto Detection The newly dual speed hubs feature auto detection function that allows each individual port
automatically detect and select optimum operating speed at 10Mbps or 100Mbps. Not only such
design protects user investment but also address the application problems of integrating different
speed network. Majority of the dual-speed hubs released recently, such as 3Com SuperStack II
Dual Speed Hub or Edimax’s ED-1516, adopt this auto detection design. The major features of
the “auto detection” dual-speed hubs include:
3.6.1.3.1 Internal 10Mbps and 100Mbps Segments
In order to connect both 10Mbps and 100Mbps networks, the dual-speed hub has two
independent built-in segments, one for connecting 10Mbps Ethernet network and the other
for connecting 100Mbps Fast Ethernet network, just like two small hubs are built inside the
dual-speed hub. Because of the transmission speed, these two segments are totally
independent as illustrated in Figure 3-4.
Figure 3.4 Internal 10Mbps and 100Mbps Segments
35
3.6.1.3.2 Auto-Negotiation Port
Depending on the speed of the attached network devices, each individual port of a dual-speed
hub provides Auto-Negotiation capability that automatically senses and selects optimum speed at
10Mbps or 100Mbps. Then the dual-speed hub will connect the ports to corresponding segment
as illustrated in Figure 3-5.
3.6.1.3.3 Internal Switch
As explained in early section that we can not simply replace traditional 10Mbps Ethernet
hub with 100Mbps Fast Ethernet hub in many installations without adjustment on the
network structure or topology. Two Fast Ethernet hubs can only be linked through a 5
meters UTP cable, while there’s no such restriction in 10Mbps Ethernet. A dual-speed hub
with extension port feature is designed specifically to address such restriction, the extension
port is actually an external switch port which connects the internal 100Mbps segment and
another 100Mbps hub as illustrated in Figure 3-9. The dual speed hub with the extension
port will no longer be restricted by Class II hub specification, therefore fits in traditional
10Mbps Ethernet network structure and topology and attains the ultimate goal of “One-to-
one replacement”. There are only a few manufactures provide such unique dual-speed hubs,
Edimax’s ED-1416 series dual-speed hubs are one of such design. [14].
Therefore, users can attach different speed network devices to any port of the dual-speed hub
without worry of the communication problem as illustrated in Figure 3-6
Figure 3.5 Auto-negotiation Ports
36
3.6.1.3.4 Stackable Dual-Speed Hub
Hubs with stackable function allow several hubs cascaded together through the stacking
cables to form a logical hub with higher port density. Unlike regular Ethernet hub, two large
logical hubs - one 10Mbps and one 100Mbps, are created when several stackable dual-speed
hubs are cascaded. All the 10Mbps segments are cascaded together to form a logical hub
while all the 100Mbps segments form another 100Mbps logical hub, these two logical hubs
will then be connected by the internal switch from one of the dual speed hubs as illustrated
in Figure 3-7
S
Some manufacturers apply different approach in cascading the dual-speed hubs, it relies on each
individual dual-speed hub’s internal built-in switch to routing the traffic and cascading all the
dual-speed hubs through a 100Mbps-only bus as illustrated in Figure 3-8.
Figure 3.6 The Internal Switch connecting 10Mbps and 100Mbps Segments
Figure 3.7 The Internal Switch connecting 10Mbps and 100Mpbs Logical Hubs
37
Advantage of such design is more independent bandwidth segments are created and the
disadvantage is increased latency and cost by built-in switches in every dual-speed hub. The first
approach requires only one of the dual-speed hub come with built-in switch
3.6.1.3.5 Extension Port or External Switch Port
As explained in early section that we can not simply replace traditional 10Mbps Ethernet
hub with 100Mbps Fast Ethernet hub in many installations without adjustment on the
network structure or topology. Two Fast Ethernet hubs can only be linked through a 5
meters UTP cable, while there’s no such restriction in 10Mbps Ethernet. A dual-speed hub
with extension port feature is designed specifically to address such restriction, the extension
port is actually an external switch port which connects the internal 100Mbps segment and
another 100Mbps hub as illustrated in Figure 3-9. The dual speed hub with the extension
port will no longer be restricted by Class II hub specification, therefore fits in traditional
10Mbps Ethernet network structure and topology and attains the ultimate goal of “One-to-
one replacement”. There are only a few manufactures provide such unique dual-speed hubs,
Edimax’s ED-1416 series dual-speed hubs are one of such design. [14]
Figure 3.9 External Switch Port in Dual-Speed Hubs
Figure 3.8 100Mbps Bus connecting Dual-Speed Hubs
38
3.7 Hub Management
Because all local area network traffic must pass through the hub, it becomes an ideal place
for installation of management software to both monitor and manage network traffic. As
previously stated, stand-alone hubs are rarely manufactured with management software. In
the case of
stackable and enterprise hubs, two layers of management software are most often involved:
1: First, Local Hub Management Software is usually supplied by the hub vendor and runs
over either DOS or Windows. This software allows monitoring and management of the hub
from a locally attached management console.
2: Second, since these hubs are just a small part of a vast array of networking devices that
may have to be managed on an enterprise basis, most hubs are also capable of sharing
management information with enterprise network management systems such as HP
OpenView, IBM NetView, Sun SunNet Manager, Novell ManageWise, or Microsoft SMS
Network management information transfer between multivendor network devices and
enterprise network management systems must be characterized by standards-based
communication. The standards that govern this network management communication are
part of the TCP/IP family of protocols more correctly known as the Internet Suite of
Protocols. Specifically, network management information is formatted according to the
SNMP (Simple Network Management Protocol). The types of information to be gathered
and stored have also been defined as MIBs (Management Information Bases).
There are actually numerous MIBs defined with the most often used one for network
monitoring and management known as the RMON (Remote Monitoring) MIB. Network
statistics and information is gathered in the first place and packetized in SNMP format by
specialized software
known as agents which reside within the monitored network device and are supplied by the
network device's manufacturer.
Enterprise network management systems such as Hp OpenView are able to interpret,
consolidate, and display information and alarms from a variety of different networking
equipment manufactured by a variety of different vendors. Figure 3-10 illustrates the
relationship of the various aspects of standards-based network management
communications protocols. [6]
Figure 3.10 Standards-based Network Management Communications Protocols
39
3.8 Practical Advice and Information
Some hub management issues are particular to stackable and/or enterprise hubs. For
example :Many stackable hubs offer network management capabilities as an optional
hardware or software upgrade. It is important to fully understand the ease with which
this upgrade can be accomplished and weather or not the hubs must be powered off
while doing so. The network management traffic may exit the hub via a separate serial
port or travel along a separate bus within the hub so as not to diminish the amount of
bandwidth available for data. These options are sometimes referred to as out-of-band
management connections .The entire stack of hubs should be viewed, monitored, and
managed by the network management software as a single, virtual hub.
The local hub management software should be simple, easy to use, and preferably
Windows-based with the capability to talk to enterprise network management platforms
should that need arise.
If possible, management modules or upgrades should be included with the original purchase
in order to avoid potential upgrade hassles. Buying management modules at purchase time
is often more economical than buying upgrades later.
An issue particular to Token Ring modules included in enterprise hubs is that the
management software should be able to dynamically assign ports located on the same
physical module into different logical rings in order to optimize network performance. [6]
:
3.9 Simple Network Management Protocol (SNMP)
A widely used network monitoring and control protocol. Data is passed from SNMP agents
which are hardware and/or software processes reporting activity in each network device (hub,
router, bridge, etc.) to the workstation console used to oversee the network. Originating in the
UNIX community, SNMP has become widely used on all major platforms. There is a newer
version of SNMP, known as SNMP v.2. It is a revised protocol that includes improvements to
SNMP in the areas of performance, security, confidentiality, and manager-to-manager
communications. SNMP is now very widely used. All major operating systems, servers,
workstations, routers, hubs and switches offer the standard SNMP facilities, but most vendors
enhance these features with their own MIB’s. The most important new enhancement which has
been developed was the Remote Monitoring (RMON) MIB extension. RMON/RMON2 gives
the administrator the possibility to determine the usage of segments and the protocols that are
used most of the time. [17,18,19].
40
3.9.1 The SNMP Model
The SNMP model of a managed network consists of four components:
1. Managed nodes.
2. Management Stations.
3. Management Information.
4. A management protocol.
These pieces are illustrated in figure 3-11 and discussed below
41
Finally, security and authentication play a major role in SNMP. A management station has
the capability of learning a great deal about every node under its control and also has the
capability of shutting them all down. Hence it is of great importance that agents be convinced
that queries allegedly coming from the management station, in fact, come from the management
station. In SNMPv1, the management station proved who it was by putting a (plaintext)
password in each message. In SNMPv2, security was improved considerably using modern
cryptographic techniques. However, this addition made an already bulky protocol every bulkier,
and it was later thrown out. [17]
Network management is done from management station, which are, in fact, general-
purpose computers running special management software. The management stations contain one
or more processes that communicate with the agents over the network, issuing commands and
getting responses. In this design, all the intelligence is in the management stations, in order to
keep the agents as simple as possible and minimize their impact on the devices they are running
on. Many management stations have graphical user interface to allow the network manager to
inspect the status of the network and take action when required.
Most real networks are multivendor, with hosts from one or more manufactures, bridges
and routers from other companies, and printers from still other ones. In order to allow a
management station (potentially from yet another suppliers) to talk to all these diverse
components, the nature of the information maintained by all the devices must be rigidly
specified. Having the management station ask a router what its packet loss rate is of no use if the
router does not keep track of its loss rate. Therefore, SNMP describes (in excruciating detail) the
exact information each kind of agent has to maintain and the format it has supply it in. The
Figure 3.11 Components of the SNMP Management Model
42
largest portion of the SNMP model is the definition of whom has to keep track of what and how
this information is communicated.
Very briefly, each device maintains one or more variables that describe its state. In the
SNMP literature, these variables are called objects, but the term is misleading because they are
not objects in the sense of an object-oriented system because they just have state and no methods
(other than reading and writing their values). The collection of all possible objects in a network
is given in a data structure called the MIB (Management Information Base).
The management station interacts with the agents using the SNMP protocol. This protocol
allows the management station to query the state of an agent's local objects, and change them if
necessary. Most of SNMP consists of this query-response type communication.
This model assumes that each managed node is capable of running an SNMP agent
internally. Older devices or devices not originally intended for use on a network may not have
this capability. To handle them, SNMP defines what is called a proxy agent, namely an agent
that watches over one or more nonSNMP devices and communicates with the management
station on their behalf, possibly communicate with the devices themselves using some
nonstandard protocol.
The managed nodes can be hosts, routers, bridges, hubs, printers, or any other devices
capable of communicating status information to the outside world. To be managed directly by
SNMP, a node must be capable of running an SNMP management process, called an SNMP
agent. All computers meet this requirement, as do increasingly many bridges, routers, and
peripheral devices designed for network use. Each agent maintains a local database of variables
that describe its state and history and affect its operation.
3.10 Example of Hubs
Now it is useful to explain some of the hub products found in the market and manufactured by
the most well-known companies in this field such as 3Com and IBM
3.10.1 SuperStack II Dual-Speed Hub 500
We can conclude form its name that this product belongs to the stackable hub category and
functionally acts as an intelligent hub as will be discovered later in this section.
The SuperStack II Dual-Speed hub is an easy-to-use, 10/100 autosensing manageable and
stackable hub. It is ideal for users that want the power of Fast Ethernet and flexibility to
connect 10Mbps devices (workstations and other equipment) in the same hub or stack. The
Dual-Speed hub 500 has 12 or 24 shielded RJ45 10/100 autosensing ports on the front panel
which can both be used to connect 10Base-T (Ethernet) or 100Base-TX (Fast Ethernet)
devices to the hub. There are two segments (10Mbps and 100Mbps) in the hub, which are
linked by a switch, so the 10Mbps and 100Mbps workstations and equipment can
communicate. Some features of this product are explained as follows:
10/100 Autosensing on Every Port.
Autosensing 10/100Mbps per port offers full compatibility with Ethernet and Fast Ethernet devices. The
ports automatically detect the
43
speed of the attached device and direct the data to the appropriate hub segment.
Smart Autosensing
Smart autosensing ensures that both speed and cable quality are automatically sensed to
maximize performance. The Smart autosensing 10/100Mbps feature enabled by the
management module enhances the standard autosensing feature by recognizing not only the
cable speed (10 or 100Mbps), but also the cable quality (incorrect/correctly installed
Category 3, 4, or 5 cable) and maximizes the throughput. Once enabled by the user, Smart
Autosensing allows forgetting the cable category issues because the hub determines the
optimal setting.
Distance Extender Modules
The optional 100Base-TX and 100Base-FX distance extender modules significantly
expand the configuration capabilities of the SuperStack II Dual-speed Hub 500. These slide-in
modules overcome the Fast Ethernet Class II hub and cabling distance restrictions that handicap
existing network configurations. They allow connecting the hub to any Fast Ethernet device over
distances up to 100 meters over copper wire or up to 2 kilometers (in full duplex mode) over
fiber optic cable.
SNMP and RMON Management Module
A user-installable Dual-Speed hub 500 Management Module can be fitted in one of the
transceiver module slots, providing management where needed. A single module manages the
entire stack and provides full SNMP and RMON support.
LAN Security Architecture (LSA)
3Com's patented LSA comes standard with the hub's management to deliver advanced
security features to protect the valuable network resources. Features such as Need To Know
(NTK) protects sensitive data on the network by preventing passive listening to sensitive
information, and Disconnect Unauthorized Device (DUD) automatically detects and/or disables
unauthorized devices and then notifies the network management station. [16,20].
3.10.2 Passive listening
Also called passive attacks involve eavesdropping on, or monitoring, transmission without
actually disturbing the network. With eavesdropping, an attacker listens to (or watches)
information in transit. Wire-tapping is a classic eavesdropping attack. The main concern of
the point of vulnerability in the network is eavesdropping by another employee or
unauthorized user. Data is transmitted in the form of frames or packets containing the
source and destination address, and other related information. An eavesdropper can monitor
the traffic of this information on the network. Individuals who attempts to read privileged
data, perform unauthorized modification to data, or disrupt the system, on the other hand,
carry out active attacks. [21,22]
44
3.10.3 IBM 8237 Ethernet Stackable Hub
According to its configuration, this product is stackable. Functionally, it acts as an
intelligent hub. This hub comes in 3 models: Model 001, 002, and 003. Each new model
adds more advanced features to the model preceding it. Among the features to this hub are
the following:
A Robust and Reliable Platform
3 separate internal Ethernet backplanes (segments).
Multiple Model 002 or Model 003 management units can be installed in 8237 stack. If the
primary management unit must be taken out of service, the backup management unit
automatically takes over with no loss of management function or management data.
All models of the 8237 are hot-pluggable; they can be replaced individually without
disrupting the other hubs in the stack.
Configuration data is stored in nonvolatile memory and is automatically restored after
power disruption.
Excessive collision protection: the 8237 will partition (disable) any of the 10Base-T ports
when more than 32 consecutive collision-causing frames are transmitted from that port.
While the port is disabled transmissions from the network to that device are maintained.
The port is automatically re-enabled when the condition clears.
Jabber protection: the 8237 partition a port when a node transmits continuously for 6.5
milliseconds. The port is automatically re-enabled when transmission from that port stops
for 9.6 microseconds. All 8237 models offer these intelligent features to protect the
network and keep it running.
Raw Management Power with RMON
The model 003 Advanced Management Unit contains, in addition to the SNMP
management features of the Model 002, a remote monitoring agent that supports all nine groups
of RMON MIB. This agent employs a dedicated 386 processor with 4MB RAM standard (20MB
maximum). RMON serves as a tool for network planning and troubleshooting by revealing
detailed network status. It's able to monitor any single Ethernet segment connected to one of the
8237 stack packplanes. The RMON MIB nine groups are:
Statistics: keeps segment statistics such as number of packets, collisions, broadcasts
and more.
History: holds historical statistics and utilization. Configurable historical studies.
Alarms: allows alarms on other MIB variables.
Hosts: statistics for each host/device on the network.
Host Top N: sorted host statistics.
Traffic Matrix: statistics for traffic between nodes.
Filters: filter capability.
Packer Capture: ability to capture filtered packets.
Events: allows notification to management station based on an event or alarm.
Built-in Security for Intrusion Protection
45
The 8237 provides intrusion protection at the port level and the 8237 features
eavesdropping protection with automatic address-learning mode. Intrusion protection is enabled
by assigning a preferred-source address to each 8237 repeater port authorized to access the
network through that port. If the source address of an incoming packet does not match the
preferred-source address for that port, the system can be configured to send an SNMP warning
message or to disable the port at the same time. [23,24]
3.10.4 Intrusion
The first step in an intrusion attack is to gather information about the network that is to be
attacked. This is done by probing the target network to try and find any weaknesses or
security holes that can be exploited.
A tool such as a Port Scanner can be used to easily scan every port on a range of network
addresses searching for any vulnerable ports. If any port connections are made, these are
reported to the hacker and in this way a picture of the network is built up. Once the hacker
has gained as much information as possible, they will then try to breach the security of the
network using one of the vulnerable ports discovered. A good network security product will
block port scanners, denying the hacker the ability to gather information about the network.
[21,25]
When a network is connected to the Internet to increase information sharing,
communications, or productivity, the network is vulnerable to potential intrusions and
attacks. Intrusion is where a hacker enters the network and tries to gain information (such as
passwords or access to data). This might be done without the owner of the network even
knowing that anyone has gained unauthorized access to the network. Intrusion attacks are
used to gain unauthorized access to a device or network. Once inside, the hacker can steal
data or passwords, or can vandalize the system by destroying valuable data.
3.10.5 Port Scanning
Refers to the act of using various open ended technologies, tools and commands to be able
to communicate with another remote computer system or network, in a stealth mode,
without being apparent, and be able to obtain certain sensitive information about the system
functions and the properties of the hardware and the software being used by the remote
systems. In another word, port scanner is a program that automatically detects security
weaknesses in a remote or local host.
Ports are basically entry exit points that any computer has, to be able to communicate with
external machines. Each computer is enabled with 3 or more external ports. These are the
ports used by the computer to communicate with the other computers, printer, modem,
mouse, scanner and other peripherals.
However these are not the only ports that any computer has. Every computer is also blessed
with virtual ports that number in a few thousand ... Sixty five thousand five hundred and
thirty six to be precise. The computer uses these numerous ports to virtually communicate
with other systems when using specific protocols. Under normal circumstances all these
ports are open and their status is said to be "listening for connections" which means that
they are ready to establish communication with other machines on a network. In such a case
46
any external machine wishing to send data shall, unless restricted, be allowed to
communicate directly with that machine. [26,27]
3.10.6 D-Link Dual-Speed Rack-mount Hub Stack
D-Link’s DFE-2600 series dual-speed stackable hubs provide an easy and cost-effective
transition to Fast Ethernet. They give departmental users the 10/100Mbps dual-speed
flexibility, scalable expansion, and the most competitive price for plug-and-play connection
of Ethernet and Fast Ethernet.
With Ethernet/Fast Ethernet support at the port level, this hub can deploy 100Mbps when and
where needed, and will run 10Mbps on some desktops on the network
D-Link’s DFE-2600 series dual-speed stackable hubs provide an easy and cost-effective
transition to Fast Ethernet. They give departmental users the 10/100Mbps dual-speed
flexibility, scalable expansion, and the most competitive price for plug-and-play connection
of Ethernet and Fast Ethernet.
Dual-Speed Flexibility
With Ethernet/Fast Ethernet support at the port level, this hub can deploy 100Mbps when
and where needed, and will run 10Mbps on some desktops on the network
Easy to Use
Each port on the hubs supports dual 10/100Mbps speeds. The hubs auto-negotiate the speed
with the connected nodes and create independent 10Mbps and 100Mbps segments. No
configuration setting is necessary, and Ethernet and Fast Ethernet users can be physically
located anywhere on the network.
Stackable in groups of 5, the hubs allow users to gradually add ports as their network
expands. Users can start with a single hub, then add units to eventually reach 120 ports per
stack. An MDI-II interface allows easy cascading of 2 stacks to bring the port density up to
238.
Optional 100Base-TX twisted-pair and 100Base-FX fiber modules provide easy micro-
segmentation and cost-effective inter-stack traffic bottleneck elimination. They also allow the
cable distance between hubs to be extended beyond the Fast Ethernet standard guidelines.
10/100Mbps Integration
With a built-in switching function, connection between 10Mbps and 100Mbps segments of
the entire stack is transparent. This allows 10Mbps and 100Mbps users to talk to each other
transparently.
Exclusive Configuration
Optional 100Base-TX twisted-pair and 100Base-FX fiber modules provide easy micro-
segmentation and cost-effective inter-stack traffic bottleneck elimination. They also allow the
cable distance between hubs to be extended beyond the Fast Ethernet standard guidelines
47
Industry-standard SNMP
Depending on requirements, users can configure the stack to be with or without SNMP
management. SNMP agent is built into the master hub, allowing users to monitor network
traffic and set up security from a management station. In addition, redundant backup SNMP
agents can be configured by stacking 2 master hubs together.
Key Features
16 or 24 10/100Mbps dual-speed ports per hub.
Up to 5 units (120 ports) per stack.
1 MDI-II uplink port and 2 expansion slots per hub for easy expansion.
Choices of managed and unmanaged stacks.
Built-in Switch function for integrating 10Mbps and 100Mbps users.
Full-duplex 100Base-TX and 100Base-FX switch modules for easy segmentation
and cable extension.
Removable power supply for easy maintenance.
Redundant backup SNMP management.
Per-port intrusion control for network security.
RMON support. [28]
Managed from D-View, HP OpenView, SunNet Manager.
RS-232 console port (master hubs).
Network traffic, analytical graphs monitoring.
3.10.7 NetStacker II Stackable 10/100 Hubs
Asante’s NetStacker Dual-speed Stackable Hubs allow small and larger-sized business to
implement departmental networks and access network resources at speeds up to 100Mbps,
with a design that is plug-and-play ready, cost-effective and expandable.
Performance and Flexibility
Asante’s NetStacker 12 and 24-port dual-speed stackable hubs provide the option of 10Mbps or
100Mbps operation, for connecting network devices to a Fast Ethernet network.
NetStacker II Hubs include an internal bridge module allowing simultaneous transmission
between 10Mbps and 100Mbps connections.
Auto-negotiation feature makes installation and configuration easy by automatically detecting
and configuring 10Mbps and 100Mbps.
Supports up to eight unmanaged 12 or 24-port stacked units for up to 192 ports, and includes one
standard MII slot on each unit for 100Base-FX connectivity options..
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Asante’s NetStacker Dual-speed Stackable Hubs allow small and larger-sized business to
implement departmental networks and access network resources at speeds up to 100Mbps,
with a design that is plug-and-play ready, cost-effective and expandable.
Performance and Flexibility
Asante’s NetStacker 12 and 24-port dual-speed stackable hubs provide the option of 10Mbps or
100Mbps operation, for connecting network devices to a Fast Ethernet network.
NetStacker II Hubs include an internal bridge module allowing simultaneous transmission
between 10Mbps and 100Mbps connections.
Auto-negotiation feature makes installation and configuration easy by automatically detecting
and configuring 10Mbps and 100Mbps.
Supports up to eight unmanaged 12 or 24-port stacked units for up to 192 ports, and includes one
standard MII slot on each unit for 100Base-FX connectivity options.
3.10.8 EtherEZ Hub 10
The EtherEZ line of hubs includes 5-, 8-, and 16-port 10Mbps standalone, unmanaged hubs
designed for home and small office users who need a legacy 10Base-T connection. They feature
uplink ports for easy, affordable, network expansion, and a designated daisy-chain port to enable
cascading hubs as the network grows.
Features
Choice of 5-, 8-, or 16-port densities.
Wide choice of power supplies.
Additional ports on 8- and 16-port models for backbone and mixed media connectivity.
Daisy
Benefits
Plug-and-play - no software or switches to configure.
At-a-glance LEDs for easy network monitoring.
Automatic port partitioning and reconnection isolates problems until faults are corrected.
Jabber lockup protection prevents data loss.
Easy, affordable network expansion. [28]
3.11 Choosing a Hub
When it comes time to choose a vendor for networking hardware, not necessarily just hubs,
there are three things that must be considered before making any purchases:
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1: Breadth of products offered
2: Depth of services offered
3: Price of product versus operational savings [1]
3.11.1 Breadth of Products Offered
infrastructure, more educated purchasing decision should be made. Finding a vendor who
makes a highly scaleable workgroup- to enterprise-level intelligent hub system and
additional products such as routers, bridges, and network interface adapters that all function
under the same network management system, might prove to be a bit of a challenge. While
there are many vendors that make hubs for specific audiences, and it may be really easy to
purchase any old product from the local computer store to get started, it is important to look
at the big picture. This step is critically important on the verge of expansion or when just
now implementing a star topology on the LAN as part of the overall upgrade path. Besides,
many vendors will argue that their products work best in a brand-homogeneous
environment. [1]
As a beginning to search for the perfect hub, more vendors undoubtedly will be
encountered, many of whom will be offering almost identical product lines. If there is an
intent to network only a few machines together, perhaps fewer than 12, selecting any of the
many passive hubs offered on the market will more than likely be satisfied. In case of a
long-term goal for a workgroup that includes a larger, more high-end network
3.11.2 Depth of Services Offered
Many larger vendors also provide networking consulting and installation services through
local distributors and certified resellers. When having to build a network or upgrade an
existing one, these services may be found quite beneficial. If the LAN implementation is
going to be a one-time-only type of project and have no immediate plans to upgrade until
the technology significantly improves, nothing will be lost by picking any product that will
fulfill the needs from any vendor. At the same time, there is no telling how any level of
assistance from a qualified professional can benefit the implementation. Having someone to
bounce an idea off may change the whole outlook on what are trying to accomplish with the
network. However, only an experienced network engineer can help to build a network
computing environment that will fulfill a given needs in the best possible way. [1]
3.11.3 Price of Product versus Operational Savings
Many of the more high-end manufacturers of intelligent hubs and comprehensive network
hardware solutions are significantly more expensive than their nearest competitors with
seemingly similar product lines. While entry-level passive hubs obviously will be less than
entry-level intelligent hubs, the three-digit price difference for the same number of ports and
the same overall specified speed may seem like wasted money. However, depending on the
scope of the project or the performance that is needed from the LAN, the additional
expense in hardware may save lots of time, money, and aggravation when it comes down to
adding additional nodes, adding routing capabilities, trying to troubleshoot problem
connections, increasing operating speed on certain systems, or simply using the network. It
50
should be award that certain increased costs in hardware could offer substantial savings in
operation later, when there is a need to be more flexible and open. [1]
4 Design and Implementation of the Proposed System
4.1 Introduction
As for the implementation part, we explain the implementation process in which we specify
how we implement the system using the algorithms mentioned in the previous part and the
language we have used to write the code of the system. This chapter also contains a detailed
explanation of the system parts where each part has a specified function to complete the
whole function of the system. Finally there will be a comprehensive illustration of the
windows used inside the system, the purpose of each one, how they work, and the
relationships between them.
First of all and in the design part, we give a brief description for the proposed system. Then
we explain the system architecture in terms of hardware and software along with its related
requirements. The design part also contains the design process in which the primary
components of the system were explained then giving a flowchart to show how these
components work. The last topic in the design part is the algorithms associated with every
function in the system.
This chapter presents the design and implementation of the proposed system (Designing
Local Networks using Hub Devices). It contains some examples concerning how to design a
local network and what rules should be followed in choosing the suitable hub kind.
Basically the chapter is divided into two parts: Design Part and Implementation Part.
4.2 Description of the System
In order to design the system, we carefully chose the components that reflect its intended
object. This object is to make the user of the system understand how to use the hub to
construct a good network for a given building specifications, how the suitable type of hub
can be determined, how the hub can be placed in the building, what is the right place, and
how to compute the suitable cable runs between that hub and any computer in the network.
Therefore we choose the Network Design component to be the heart of the system which
handle the above mentioned functions. Network Design component was divided into two
options: Practical Example and Designing a Network that will be explained later in this
chapter. The system also contain another components that play an important role and
considered as a good foundation in enhancing the knowledge of the user about the
networks, hubs, cables, and other topics related to computer networking. These are Network
Analysis and Network Knowledge.
All these parts of the system will be discussed in more details in the design process section
and the sections that follow
4.3 System Architecture
The overall system architecture consists of the following:
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4.3.1 Hardware Architecture
The system was implemented using a personal computer PII with 10GB Hard Disk, 64MB
RAM, and 450MHz processor.
4.3.2 Software Architecture
The system was implemented using Visual Basic 6.0 programming language along with
Adobe Premier and 3D Max programs to help in building the design graphics.
4.4 The Design Process
The system contains three major components:
Network Analysis
Network Design
Network Knowledge The system contains three major components:
Network Analysis
Network Design
Network Knowledge
We put the Network Analysis as the first component because it acts as important
foundations the network analyst must understand before begin with building any network. It
involves the necessary requirements about the many types of networks and cables and where we
can use one cable type instead another. Also it contains some problems that face the network
builder and how they can fix them.
The most important part is the Network Design that comprises two choices: Practical
Example and Designing a Network. In the Practical Example we have constructed a building
with 5 rooms and the proposed network that must be installed in this building or office comprises
8 computers. These computers must be wired together to a hub. The system shows how to install
the hub and the right place for this installation. Then come the installation of the cables that
connect the hub to the computers to complete the wiring system and ensure the best network
design for this office. As for the part of Designing a Network another 2 buildings one with one
floor and the other with two floors. The maps of these buildings are given to the system by a
scanner and enter the system to analyze them and choose the computers for the rooms. After
choosing the computers (servers or workstations) the system will compute the suitable cable
lengths and give a list of the most suitable locations for placing the hub depending on the
priorities of these places. The following flowchart shown in Figure 4.1 illustrates the operations
52
included within the Network Design part of the proposed system as it the most distinct part in
representing the role of the system.
Finally we have the Network Knowledge that serves as help for the system. This part
include general topics such as an introduction to networking, network operating systems, data
transmission media, access methods, network architectures, network topology, hubs: the central
connection point, routers, bridges, switches and so on.
53
Figure 4.1Flowchart of the System
54
4.5 The System Algorithms
The following set of algorithms demonstrates the procedures used to implement the
proposed system.
4.5.1 Select Category
This algorithm is used to select from among the main three parts of the system mentioned in
the preceding section which are Network Analysis, Network Design, or Network
Knowledge:
Select Category Algorithm
Input: Category Index
Output: Display the selected category
Step1: hide the main interface of the system
Step2: Case Index
Case 0
Load and display the file of the Network Analysis
Case 1
If Practical Example Then
Load and display the first part of the Network Design
" Before designing the network inside the office"
Else if Designing a Network Then
Load and display Designing a Network option
"Designing networks in 2 different buildings"
Case 2
Load and display the file of the Network Knowledge
Step3: End
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The most important step in this algorithm is Step2 (Case Statement) which handle and
enable the user to choose any of the three cases or options written for the Network Analysis,
Design and Knowledge. Inside the second case there is two further options which are the
Practical Example and Designing a Network. More details about these two options were
discussed in the Design Process section. The third case load and display all the information
stored inside the Network Knowledge category
4.5.2 Fill Index with Subjects
The Index is an important part of the system because it organizes all the Subjects in
alphabetical order and hence simplify searching it to find any specific subject the user want
to read. The following algorithm was written to fill this Index with all the subjects and
arrange them alphabetically:
Fill Index with Subjects Algorithm
Input: Initial Starting
Output: Filled Index
Step1: Hide the Main Menu
Step2: With Sindex "Set of Records in the Database"
If No. of records <> 0 Then
Move to the first subject
Do while Not EOF
Add the current subject to Index
Move to the next subject
Loop
Step3: End with
If we want to show the Index we have to hide the Main Menu first as this Main Menu lies in
front of both the Index and the Contents which will be discussed later. Therefore the first
step in this algorithm is to hide the Main Menu. The second step is to fill the variable
Sindex, which was declared as of type RecordSet that mean a set of records in the database,
with data form that database. First we must check the number of records in the database, it
must be not equal zero, and if this is the case the algorithm will move to point to the first
record. Then it will enter a Do While statement to continue adding new subject, move the
pointer to the next subject and repeat the loop until the last subject is added.
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4.5.3 Fill Contents with Subjects
The Contents also stores the information of the system but in different manner. It organizes
the data as a tree that reflects the logical arrangement of the subjects and the related topics
branching from them. The algorithm below illustrates how to fill this Tree (Contents) with
data taken form the system database:
Fill Contents with Subjects Algorithm
Input: Initial Starting
Output: Filled Contents
Step1: Declare nodx as Node in the Tree of Subjects
Step2: Set nodx to (Networking)
"Root of the Tree"
Step3: Set nodx to (Network Analysis)
"1st branch from Networking"
Set nodx to (Network Design)
"2nd
branch from Networking"
Set nodx to (Network Knowledge)
"3rd
branch from Networking"
Step4: Set nodx to (How to wire a network)
"1st branch from Network Analysis"
Step5: Repeat all Subjects branched from network analysis
Step6: Repeat step 4 and 5 for Network Design and Knowledge
Step7: Ensure the Root of the Tree always visible
Step8: End
Then comes filling the branches of the root, which are Network Analysis, Network Design,
and Network Knowledge. This was done by step3. Step4 sets nodx to "How to wire a network"
subject, which is the first branch from the Network Analysis branch. Step5 and step6 repeats the
above statements to fill the remaining subjects belong to Network Analysis and the subjects of
Network Design and Network Knowledge. Finally step7 ensures that the root of the tree "
Networking" be always visible when choosing the Contents part.
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As one can see, this algorithm includes repeating some statements which differ only in the
name of the subject and which handle the process of filling the tree. First and in step1 we
declared the variable nodx to be any Node in the tree. Step2 sets nodx to the networking subject
which was considered as the root of the tree.
4.5.4 Open Database of the System
This algorithm is used to open the database of the system by setting the variable mydb1 to
the database DB1.mdb, this is done by step1. Step2 sets the variable Sindex to hold the set
of records contained within this database:
Open Database of the System Algorithm
Input: Initial Starting
Output: Open database for processing
Step1: Set mydb1 to database DB1.mdb
Step2: Set Sindex to be the set of records in the database
Step3: End
4.5.5 Continue the Second Part of the Practical Example
This algorithm was written to continue the second part of the Practical Example. Step1
loads the intended file for building the network inside the office. Step2 runs the design and
step3 hides the continue button.
Continue the Second Part of the Practical Example Algorithm
Input: Click Continue Button
Output: Play the 2nd
part of the Practical Example
Step1: Load the file of the 2nd
part of the Practical Example
"Building the network inside the office"
Step2: Play the design and Hide the Continue Button
4.5.6 Index Search
All processing in this algorithm was done in the fields of the database as follows:
Index Search Algorithm
Input: Click a subject in the Index
Output: The contents of that subject
Step1: With Sindex
Find the ID of the clicked subject
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Load the file this ID belongs to
"Network Analysis, Design, or Knowledge"
Search the file about the bookmark related to this subject
Display the text beginning from that bookmark
Step2: End with
Step3: End
Here the algorithm uses a with statement to enter the database, search for the ID of the
subject which have been clicked in the first place, load the file containing this subject
depending on that ID and display the subject from its bookmark
4.5.7 Contents Search
"Network Analysis, Design, or Knowledge"
Contents Search Algorithm
Input: Click a subject in the Tree (Contents)
Output: The contents of that subject
Step1: With Sindex
Find the TreeLoc of the clicked subject
Load the file this ID belongs to
Step2: End with
Search the file about the bookmark related to this subject
Display the text beginning from that bookmark
The function of this algorithm is the same for the previous one except that it uses the
TreeLoc field instead of the ID field for searching the intended subject, the rest of the
algorithm is the same.
4.6 The Implementation Process
The system was written in Microsoft Visual Basic 6.0 to get the benefits of the visual
windows facility provided by this programming language. The system includes a database
designed using Microsoft Access program that contains all the data used by the system to
fill some of its components such as the Network Analysis and the Network Knowledge.
Among the fields in this database are ID, Subject, TextLoc, TreeLoc, and Doc. The ID is a
unique number to define each subject in the text and simplify the search for a specific
subject to the user of the system. The Subject field contains the subject title. The TextLoc is
a bookmark used to determine the beginning of the subject and TreeLoc is used to construct
the tree associated with the contents part of the system. As for the Network Design, it was
implemented by the 3D Max and Adobe premiere programs that were the most powerful
tools in designing the buildings and generating the design graphics to show the progression
of constructing the networks for these buildings.
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4.7 Parts of the System
The primary parts of the system can be categorized into four basic parts. Each category has
its special function in the system. Figure 4-2 illustrates these categories and their sub
categories. The four primary parts are Menu, Contents, Index, and Options.
The most important part is the Menu as it contains the three basic functions of the system:
Network Analysis, Network Design, and Network Knowledge. It also has the Exit function
to quit the system.
The contents and Index categories are used to easily find any subject interested by the user.
Finally there is the Option category which include Copy, Print, Export, Find, and Exit
4.8 The System Windows
Our proposed system has one main window that comprises everything discussed previously.
This window is shown in figure 4-3 below:
In this window one can see the primary three parts of the system: Network Analysis,
Network Design, and Network Knowledge. These parts belong to the Menu tab that lies beside
the Contents and Index tabs. Therefore clicking the Menu tab will show those three parts.
As mentioned earlier, the Contents tab displays the subjects of the system as a tree, this
was done to help in understanding a given topic and to whom it belongs. The following figure 4-
4 illustrates the Index tab.
Figure 4.2 The Main Window
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Figure 4.3 The Contents Tab
Figure 4.4 The Index Tab
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4.8.1 The Network Analysis Part
This part of the system is important to overview before entering the Network Design part.
The window of this part is shown in figure 4-6 below:
4.8.2 The Practical Example Window
The following windows illustrate the steps performed in constructing the network in the first
building:
Figure 4.5The Network Analysis Category
Figure 4.6 Top View of the Building before constructing the Network
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Figure 4.7 Choosing the Location of the Hub
Figure 4.8 Choosing the Location of the Network Server along with Cable Length to the Hub
63
Figure 4.10 Installing the Computers and Choosing the Cable Lengths in the 3rd Room
Figure 4.9 Installing the Computers and Choosing the Cable Lengths in the 2nd Room
64
Figure 4.11 Installing the Computers and Choosing the Cable Lengths in the 4th and 5th Rooms
Figure 4.12 Top View of the Building after constructing the Network
65
4.8.3 Designing a Network Window
Here we have used two buildings, one with one floor and the other with two floors to show
how to build the networks inside them. The system takes the maps from a file. Then by
choosing the locations of the computers (workstations and servers) the system will provide
the user with the right place of the hub and the suitable wiring system along with the
approximate lengths of the cables connected to that hub. The following figures demonstrate
these operations.
Figure 4.13 The Map of the First Building before Constructing the Network
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Figure 4.14 Choosing the Computers for the Network
Figure 4.15 The Hub Location and the Wiring System after Connecting the Computers
67
Figure 4.16 The Map of the Second Building before Constructing the Network
Figure 4.17 Choosing the Computers for the Network
68
Figure 4.18 The Hub Location and the Wiring System after Connecting the Computer
69
4.8.4 Network Knowledge Window
As mentioned previously in this chapter, Network Knowledge category was used as a help to the
user and contains some important topics such as Introduction on Networking, Network
Topologies, Access Methods and so on. Figure 4-20 illustrates the Network Knowledge.
4.9 The Results
The following security features was concluded during the work in this research, but are
related only to more advanced hub kinds:
1. Intrusion protection with automatic address learning mode.
2. Need To Know (NTK) for protecting sensitive data.
3. Disconnect Unauthorized Device (DUD).
4. Port scanning protection.
5. Eavesdropping and passive listening protection. 6. Jabber/excessive collision control featuring automatic partition and reconnection.
7. Monitoring and analyzing network traffic by SNMP protocol.
8. Supporting RMON agents (full 9 groups).
Figure 4.19 Network Knowledge Window
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4.10 The Limitations
From among the limitations still in some hub devices are the following:
1. Using a hub in the network cause loosing some network bandwidth because all ports
share the same wire.
2. The network will suffer from a lot of collisions in case of using broadcasting protocol.
3. Not all kinds of hubs support dual-speed feature.
Each manufacturer has a different way of dealing with the power of the signal being sent through
the wire. Some manufacturers recommend cable lengths of no longer than 50m