chapter 1 introduction 1.1network and the internet network and the internetnetwork and the internet...
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Chapter 1 IntroductionChapter 1 Introduction
1.11.1 Network and the Internet
1.1.1 1.1.1 Traditional Needs of Networking
1.1.2 1.1.2 The needs of Home Networks
1.1.3 1.1.3 Networking and Economics
1.21.2 Network Hardware Components
1.2.1 1.2.1 Servers
1.2.2 1.2.2 Workstations
1.2.3 1.2.3 Connecting Devices
1.2.4 1.2.4 Networking Medium
Chapter 1 Introduction
1.1 1.1 Network and the Internet Network and the Internet (1/4)(1/4)
A network is a set of nodes connected together by a shared medium. A node can be a computer or a connecting device.
It is any device with an IP address.A computer on a network is also called a host.
The medium may be a cable or radio wave The most elementary network
connects two computers together using a cross-over cable. The Internet is a large collection of networks.
Chapter 1 Introduction
1.1 1.1 Network and the Internet Network and the Internet (2/4)(2/4)
Chapter 1 Introduction
1.1 1.1 Network and the Internet Network and the Internet (3/4)(3/4)
The Internet and a home network: they use the same protocol
to connect and send information.
Technologies to connect a network to the Internet: dial-up access DSL cable modems wireless technologies etc.
Chapter 1 Introduction
1.1 1.1 Network and the Internet Network and the Internet (4/4)(4/4)
Chapter 1 Introduction
1.11.1.1 Traditional Needs of Networking.1 Traditional Needs of Networking
Networking is to connect computers together for the purpose of
communication, and sharing of resources.
The resources on a network refer to datahardwaresoftware, and services (e.g. Internet access).
Chapter 1 Introduction
1.11.1.1 Traditional Needs of Networking.1 Traditional Needs of Networking
A. A. Sharing of Data B. B. Sharing of Hardware C. C. Sharing of Software D. D. Communication E. E. Internet Sharing
Chapter 1 Introduction
1.11.1.1 Traditional Needs of Networking.1 Traditional Needs of Networking
A. Sharing of Data A. Sharing of Data
On a network, folders and files in a computer can be shared out to allow authorised users to access from other computers.
A file server has a larger storage capacity, and allows access to files by different users.
Advantages: Better Version Control
User can always access the most updated version of data which may be modified by different users.
Without a network, the same file may be stored in several computers -- it is difficult to tell which one is the most updated.
Data treated with more intensive care more frequent backup, automatic file duplication using another hard disk.
Chapter 1 Introduction
1.11.1.1 Traditional Needs of Networking.1 Traditional Needs of Networking
B. Sharing of Hardware B. Sharing of Hardware
Chapter 1 Introduction
1.11.1.1 Traditional Needs of Networking.1 Traditional Needs of Networking
B. Sharing of Hardware B. Sharing of Hardware
Hardware can be shared out so that it can be accessed by other computers on the network. e.g. a printer, CD-ROM drive or fax modem,
Advantage: saves the cost in purchasing many hardware no need to use a particular computer for printing
Chapter 1 Introduction
1.11.1.1 Traditional Needs of Networking.1 Traditional Needs of Networking
C. Sharing of Software C. Sharing of Software
Some software are to work in a networked environment e.g. the network version of a DBMS
The DBMS is installed in a computer called database server Some software vendors provide site licensed software
the software may be installed in all the computers in a site, or some computers, depending on the agreement.
Site license is less expensive than purchasing individual copies for computers
if there are large number of computers in a site
Chapter 1 Introduction
1.11.1.1 Traditional Needs of Networking.1 Traditional Needs of Networking
D. Communications D. Communications
On a network, users may communicate with others e-mails notice boards chat rooms newsgroups videoconferencing etc.
Each user is identified by the user name. If the network is connected to the Internet,
communication means reaching people in another part of the world.
Chapter 1 Introduction
1.11.1.1 Traditional Needs of Networking.1 Traditional Needs of Networking
E. Internet Sharing E. Internet Sharing
Chapter 1 Introduction
1.11.1.1 Traditional Needs of Networking.1 Traditional Needs of Networking
E. Internet Sharing E. Internet Sharing
Internet sharing means simultaneous use of one Internet connection by more than
one computer within an organisation. Most ISPs assign one global IP address per subscriber
A router with NAT function allows computers to use the same global IP address
Business plans of an ISP allow Internet sharing Target customers
offices, and schools.
Chapter 1 Introduction
1.11.1.2 The Needs of Home Networks.2 The Needs of Home Networks
A home network is similar to the network of a business, but comprises smaller amount of nodes and less sophisticated software and connecting devices.
Why setting up a home network? A. Internet sharing B. setting up a smart home C. setting up a home entertainment system.
Chapter 1 Introduction
1.11.1.2 The Needs of Home Networks.2 The Needs of Home Networks
A. Internet SharingA. Internet Sharing
(As of May 2005, more than 60% of the families in HKSAR have access
to the Internet) Very often, Internet sharing happens in these families. ISP’s Plans for home customers are
lower in price than those business plans most ISPs do not agree with Internet sharing by home
customers. However, with the growing reality of Internet sharing, many
ISPs begin to adjust their policies check your subscriber agreement to see your ISP's policy.
Chapter 1 Introduction
1.11.1.2 The Needs of Home Networks.2 The Needs of Home Networks
B. Smart HomeB. Smart Home
Chapter 1 Introduction
1.11.1.2 The Needs of Home Networks.2 The Needs of Home Networks
B. Smart HomeB. Smart Home
Smart home Also called Home automation system combining technologies in networking and controlling home
appliances to enable people to manage their homes from a computer, even
remotely Some of the tasks:
1. Automatic light control 2. Control home appliances remotely 3. Control access to a home 4. Monitor home remotely 5. Enhance home security 6. Others
alert you changes in environment such as temperature, brightness and moisture
Chapter 1 Introduction
1.11.1.2 The Needs of Home Networks.2 The Needs of Home Networks
C. Home Entertainment SystemC. Home Entertainment System
Chapter 1 Introduction
1.11.1.2 The Needs of Home Networks.2 The Needs of Home Networks
C. Home Entertainment SystemC. Home Entertainment System
Home Entertainment System Combines
DVD player, TV tuners of PCTraditional audio-visual equipment
• such as TV and Hi-Fi system Network technology
Allows audio and video signals, movies and music to be played from a computer and distributed over the network.
Example is Windows® XP Media Center Edition (MCE)
Chapter 1 Introduction
1.11.1.3 Networking and Economics .3 Networking and Economics
An entire industry has emerged that develops networking technologies and provides networking services.
A new platform for people to conduct business e-commerce
Telecommuting employees are working at home, rather than in the office kept together by
the company network and other telecommunication channels.
flexible workplace and time less traffic congestion more quality family time increased productivity less company overhead
Chapter 1 Introduction
1.1.2 2 Network Hardware Components
On a network, hardware include 1.2.1 servers 1.2.2 workstations 1.2.3 connecting devices 1.2.4 networking medium.
Chapter 1 Introduction
1.1.2.1 2.1 Servers
A server is a computer that performs tasks for other computers manages the network
enforcing securitysharing of filessharing of hardware
A dedicated server is expensive, becauseperformance features, and fault-tolerant features
• reliable, and • robust
Chapter 1 Introduction
1.1.2.1 2.1 Servers
A. Performance Features
1. Multiple Processors Servers can run using one or more processors. Requirement:
the architecture of the motherboard and the Operating System (OS).
Note:2 processors may not double (2x) the overall performance
because • not all instructions can take the advantage of multiple
processors.
Chapter 1 Introduction
1.1.2.1 2.1 Servers
A. Performance Features
Chapter 1 Introduction
1.1.2.1 2.1 Servers
A. Performance Features
2. Larger and more reliable RAM If RAM is not enough ,
swapping is needed and the performance suffers
Buffering requires memory Buffering: look ahead and retrieve data from disks to improve the
performance. ECC RAM
Error Correcting Code RAM able to
• detect errors in two bits, and • correct error in one bit
better than parity check:• detect error in one bit
Chapter 1 Introduction
1.1.2.1 2.1 Servers
A. Performance Features
3. Bus capabilities Bus: the path between
the processor, RAM and peripheral devices.
In a server, large volume of data is moving over the bus. Peripheral Component Interconnect (PCI) bus
32-bit (33 MHz) used by traditional PCmay form a bottleneck in a server with several Network
Interface Cards
Wider and faster buses are neededFor example, 64-bit PCI-X bus (133 MHz).
Chapter 1 Introduction
1.1.2.1 2.1 Servers
A. Performance Features
4. Disk Interface IDE (Integrated Drive Electronics)
less expensive meets the needs in ordinary PCs
SCSI (Small Computer Systems Interface) handle simultaneous access to more than one hard disk more common in servers
Chapter 1 Introduction
1.1.2.1 2.1 Servers
B. Fault-tolerant Features
Fault-tolerant means that even a part fails, the whole system can still operate
Fault-tolerant guarantees the uptime of a network, and provides continued data availability.
Fault-tolerant requires redundant components
take over when there is a failure.
“hot swap” componentscan be replaced without turning off the computer
Chapter 1 Introduction
1.1.2.1 2.1 Servers
B. Fault-tolerant Features
1. RAID System (Redundant Array of Inexpensive Disks) a set of hard disks that appear to as a logical disk for
fault tolerant and/or improving performance.
Some standardsRAID-0, 1, 2, 3, 4, 5RAID-10 = RAID-1+ RAID-0
A. How is speed improved?disk heads can work independently
B. How is data loss prevented in case of disk failure?redundancy
Chapter 1 Introduction
1.1.2.1 2.1 Servers
B. Fault-tolerant Features
Chapter 1 Introduction
1.1.2.1 2.1 Servers
B. Fault-tolerant Features
2. UPS (Uninterruptible Power Supply) connected between
the mains power supply, and the computer.
includes a battery, and charging circuit
Advantages: Data availability
• the server is still accessible when power fails
Preventing data loss• alerts user to save data in files
Avoiding hardware damage• power fluctuation can reduce life-
expectancy of electrical devices
Chapter 1 Introduction
1.1.2.1 2.1 Servers
B. Fault-tolerant Features
3. Backup Server takes over services when needed by
installed with the services in duplicateholding an updated copy of the important information
• e.g. the user account database
needs not be exactly the same as the working server Examples “backup domain controllers” BDC
Chapter 1 Introduction
1.1.2.2 2.2 Workstations
A workstation is a computer that allows users to make access to the resources on the
network also called clients on a client/server network may be connected to network using
cables, or radio waves
can be converted from a standalone PCby installing
• Network Interface Card (NIC), and • networking software.
Chapter 1 Introduction
1.1.2.2 2.2 Workstations
A. Network Interface Card (NIC) (1/4)
Network Interface Card (NIC) Also called network adapter is required in all computers
including servers and workstations consists of circuitry that prepares/receives data several types:
Ethernet NIC• 10Base-2, 10Base-T, 100Base-T and
1000Base-T, 10Base-F, 10GBase-LR etc.• different data transmission rates and
for different cables Token Ring NIC wireless NIC
Chapter 1 Introduction
1.1.2.2 2.2 Workstations
A. Network Interface Card (NIC) (2/4)
Chapter 1 Introduction
1.1.2.2 2.2 Workstations
A. Network Interface Card (NIC) (3/4)
MAC address (Medium Access Control) unique identifier of NIC six-byte (48-bit) code burnt permanently
in the ROM of the NIC
C:\>IPCONFIG /ALL...Description . . . . . . . . : VIA Rhine II Fast Ethernet Adapter
Physical Address. . . . . . : 00-30-18-52-68-2E....
Chapter 1 Introduction
1.1.2.2 2.2 Workstations
A. Network Interface Card (NIC) (4/4)
The first 3 bytes identify the manufacturere.g. 00-11-11(16) represents Intel® Corporation.
Chapter 1 Introduction
1.1.2.2 2.2 Workstations
B. Networking Software (1/4)
Chapter 1 Introduction
1.1.2.2 2.2 Workstations
B. Networking Software (2/4)
Operating systems (OS) forms the major difference between
a workstation, and a server Servers are installed with
Network Operating System (NOS) manages the network, and entertains requests from clients
Workstations are installed with Desktop OS + networking software for
communicating with other computers, and sending and receiving data over the network
drivers for the NIC, and programs for protocols
Chapter 1 Introduction
1.1.2.2 2.2 Workstations
B. Networking Software (3/4)
Workstations may use OS from different vendors e.g. a Windows 2003 network allows Macintosh PC as well as
Windows PC to connect The networking software for workstations
may be available from the NOS of the server or from the desktop OS itself
Type of computer Operating System
Server Network Operating System
Client Desktop OS with networking software
Chapter 1 Introduction
1.1.2.2 2.2 Workstations
B. Networking Software (4/4)
Chapter 1 Introduction
1.1.2.3 2.3 Connecting Devices
A connecting device moves data from one network cable to another directs traffic
within a network, or across multiple networks.
include repeatershubsbridgesswitches, and routers.
Chapter 1 Introduction
1.1.2.3 2.3 Connecting Devices
A. Repeater
Attenuation signal travelling along a cable would become weaker and
weaker Effective transmission length
guarantees signal transmission over the given distance beyond which the signals may become too weak to be
detected. e.g. 100 m for Cat-5 UTP
A repeater amplifies signals are electrically powered does not understand the signals cannot help direct traffic cannot join dissimilar networks
e.g. Ethernet network and Token Ring network are dissimilar
Chapter 1 Introduction
1.1.2.3 2.3 Connecting Devices
B. Hubs
A hub also called cable concentrator common connection for cables
Each cable connects • the NIC of a computer to a port of the hub
consist of multiple ports can be used as a repeater
Broadcasting A hub broadcasts
because it echoes incoming signals to all ports
A hub-based network would easily get overloaded
Chapter 1 Introduction
1.1.2.3 2.3 Connecting Devices
C. Bridge
A bridge is not dumb because it can confine the traffic within each segment
by examining the dataagainst a forwarding table that
• records the MAC addresses of all nodesand forward data to the correct segment
can divide a larger network into smaller segments to improve efficiency
connects two dissimilar networks e.g. Token Ring and Ethernet
Chapter 1 Introduction
1.1.2.3 2.3 Connecting Devices
C. Bridge
Chapter 1 Introduction
1.1.2.3 2.3 Connecting Devices
D. Switches
A switch is a cable concentrator
joins the network cables together does not echo signals to all other ports, because
it examines data against
• a table of the MAC address of each port forwards data to the correct port
• similar to a bridge. produces less “collisions” allows several pairs of nodes to transmit at the
same time allows full-duplex
Conclusion: switch-based networks are faster than hub-
based
Chapter 1 Introduction
1.1.2.3 2.3 Connecting Devices
E. Routers
A router connects two or more networks together routes data between networks keeps a routing table is able to determine the best path for signals
Note: a router port is either connected to • a network, or
• another router.
is a vital equipment for a LAN to connect to the Internet
called • SOHO router, broadband router or
residential gateway
Chapter 1 Introduction
1.1.2.4 2.4 Networking Medium
Networking media are classified into tangible
exists in the form of a physical cable, • e.g. coaxial cable, twisted pair and fiber optic
intangibleuses in wireless technology
• e.g. radio waves Note:
Data is always transmitted in the form of physical signals known as carrier. e.g. electronic or optical signals in cables; radio waves in wireless technology
Chapter 1 Introduction
1.1.2.4 2.4 Networking Medium
A. Coaxial Cable (1/2)
A coaxial cable consists of
a central copper wire (core) an insulating layer a wire mesh
• used as shielding an outer plastic jacket
needs a BNC connector has effective transmission length up to
500 m is mainly used in bus network
e.g. old Ethernet networks (10Base-2 and 10Base-5)
is used in cable TV network for broadband Internet accesses.
Chapter 1 Introduction
1.1.2.4 2.4 Networking Medium
A. Coaxial Cable (1/2)
Shielding is done by wire mesh stops
external electromagnetic interference (EMI) • due to other electric currents
the cable from interfering neighbouring cables• to eliminate cross-talk
Advantages of shielding: increase effective transmission length increase rate of transmission
Chapter 1 Introduction
1.1.2.4 2.4 Networking Medium
B. Twisted Pair Cable
A twisted pair cable consists of copper wires twisted
in pairs Why use twists?
To cancel the magnetic fields due to
both wires
Result: cables do not produce EMI eliminate cross-talk
Chapter 1 Introduction
1.1.2.4 2.4 Networking Medium
B. Twisted Pair Cable
1. UTP (Unshielded Twisted Pair) Cables can be placed side by side without affecting each other But, susceptible to external EMI
because unshielded
are lower price than STP. several grades : Cat-3, Cat-5, Cat-7 etc.
Cat-5 • the most popular
• maximum effective transmission length: 100 m
• consists of 4 pairs of wires
• used in
– Ethernet, ATM and Token Ring networks.
• speed: 100 Mbps, 1 Gbps (1000 Mbps)
Chapter 1 Introduction
1.1.2.4 2.4 Networking Medium
B. Twisted Pair Cable
2. STP (Shielded Twisted Pair) cables are able to
resist external EMI eliminate cross-talk between two cables
are more expensive, but higher speed longer effective transmission length
are best used in “noisy” environmente.g. near a transformer station.
Chapter 1 Introduction
1.1.2.4 2.4 Networking Medium
C. Powerline
Powerline communication (PLC) uses powerline as networking medium has two types
indoor, and outdoor.
Indoor PLC for setting up local area network
Outdoor PLC Broadband over Power Lines (BPL) Advantage:
infrastructure is already available Major problem:
interfere with radio transmission, because power cable is • unshielded and • untwisted
Chapter 1 Introduction
1.1.2.4 2.4 Networking Medium
D. Fiber-optic Cable
Fiber-optic cables use glass to carry light signals
instead of electrical signals are used as network backbone
to provide high speed connection up to 10 Gbps
cannot be intercepted easily because they do not emit electromagnetic waves (radio
waves) So, very secure
have little attenuation can span miles of distance often used across floors in a building or
between buildings. are expensive
costly to install and maintain.
Chapter 1 Introduction
1.1.2.4 2.4 Networking Medium
E. Radio waves
Radio waves are used in wireless technology require
wireless NIC in computers, and an access point
• for common connection
Advantages: inexpensive flexible easy to install
Disadvantages: slow in transmission radio signals can be
intercepted easily.