Networks

Overview ( Lei You ) Overview of Local Network Topology

( Ryan McKenzie ) Internetworking Protocol ( Benjamin A

Pullen ) Mobile IP ( Hui Tan )

Overview

What is a Network? Two or more computers are connected

together by a medium and are sharing resources. These resources can be files, printers, hard drives, or CPU number-crunching power.

A network can consist of two computers connected together on a desk, or it can consist of many Local Area Networks (LANs) connected together to form a Wide

Area Network (WAN) across a continent.

The Big Picture Many individuals have asked to see the

"Big Picture" of networking: How does everything . Where does Microsoft NT fit in with routers and the OSI layers? What about UNIX, Linux and Novell?

The big picture in the following slide attempts to show all areas of networking and how they tie into each other.

Graphical Symbols Used in the Big Picture

Circles Network Operating Systems Squares Communication & cabling protocols

(OSI Transport to Physical Layer) Storm Clouds Telecommunications media or

Information Providers that connect to the Internet

Machine symbol Network "linker" can be a bridge, router, brouter or gateway

Jagged haphazard dotted line - the Internet

Telecommunications Components of The Big Picture

ISDN Integrated Services Digital Network Private Branch Exchanges PBXs, Key Systems Telcos AT&T, Bell Telephone, Sprint, Telus DataPac & DataRoute Packet switching and analog

switching WAN protocols Cell Relay Digital packet switching WAN protocol Frame Relay Digital packet switching WAN protocol X.25 Analog packet switching WAN protocol ATM Asynchronous Transfer Mode WAN protocol World Wide Web Hypertext-based multimedia

system ADSL Asymmetrical Digital Subscriber Line

ISO/OSI Model

The International Standards Organization (ISO) Open Systems Interconnect (OSI) is a standard set of rules describing the transfer of data between each layer in a network operating system. Each layer has a specific function. For example, the physical layer deals with the electrical and cable specifications.

The OSI Model clearly defines the interfaces between each layer. This allows different network operating systems and protocols to work together by having each manufacturer adhere to the standard interfaces. The application of the ISO OSI model has allowed the modern multi protocol networks that exist today.

Seven Layers in the OSI Model

7. Application Layer (Top Layer) 6. Presentation Layer 5. Session Layer 4. Transport Layer 3. Network Layer 2. Data Link Layer 1. Physical Layer (Bottom Layer)

ISO/OSI Model …

The OSI model provides the basic rules that allow multi protocol networks to operate. Understanding the OSI model is instrumental in understanding how the many different protocols fit into the networking jigsaw puzzle.

The Big Picture can be broken up according to

its protocols into the following four areas:

Local Loops

LANs

MANs

WANs

The Local Loop

The Local Loop is often called "the last mile", and it refers to the last mile of analog phone line that goes from the telephone company's central office (CO) to your house.

The Local Loop …

Typical Local Loop Protocols

Voice Lines Modem Connections – 56 kbps ISDN (Integrated Services Digital

Network) - 2 x 64 kbps digital lines ADSL (Asymmetrical Digital Subscriber

Line) - up to 8 Mbps * Cable Modems - up to 30 Mbps

Cable modems are not part of the local loop but do fall into the category of the last mile, or how high speed digital communication gets to the premises (home). It would incredibly expensive to replace the existing cabling structure. And because this cabling was designed for voice communications rather than digital, all of these protocols are needed to overcome the existing cabling limitations in the local loop and provide high speed digital data transmission.

Local Area Networks (LANS)

A Local Area Network is a system of computers that share resources such as disk drives, printers, data, CPU power, fax/modem, applications, etc. They usually have distributed processing, which means that there are many desktop computers distributed around the network and that there is no central processor machine (mainframe).

Local Area Networks (LANS) …

Components Used by LANs

Cabling standards

Hardware

Protocols

LANS: Cabling Standards Cat 3, 4 and 5 cables IBM Type 1-9 cabling standards EIA568A and 568B Ethernet cabling standards: IEEE 802.3

(10Base5), IEEE 802.3a (10Base2), IEEE 802.3i (10BaseT)

Unshielded Twisted Pair (UTP) Shielded Twisted Pair (STP) Connectors: RJ45, RJ11, Hermaphroditic

connectors, RS-232, DB-25, BNC, TEE

LANS: Hardware Devices

Network Interface Cards (NICs) Repeaters Ethernet Hubs or multi port repeaters Token Ring Multi Station Access Units

(MSAUs), Control Access Units (CAUs) and Lobe Access Modules (LAMs)

Bridges

LANS: Hardware Devices …

Brouters Routers Gateways Print servers File servers Switches

LANS: Examples of Protocols Ethernet frame types: Ethernet_II,

Ethernet_SNAP, Ethernet_802.2, Ethernet_802.3

Media Access Control layer (MAC layer) Token Ring: IBM and IEEE 802.5 Logical Link Control Layer (LLC) IEEE 802.2 TCP/IP IPX/SPX Asynchronous Transfer Mode (ATM)

Metropolitan Area Networks (MANs)

A Metropolitan Area Network is a system of LANs connected throughout a city or metropolitan area. MANs have the requirement of using telecommunication media such as voice channels or data channels. Branch offices are connected to head offices through MANs. Examples of organizations that use MANs are universities and colleges, grocery chains, and banks.

Metropolitan Area Networks (MANs)…

Metropolitan Area Networks

(MANs)…

The main criterion for a MAN is that the

connection between LANs is through a

local exchange carrier (the local phone

company). The protocols that are used for

MANs are quite different from those used

for LANs (except for ATM, which can be

used for both under certain conditions).

Examples of MAN Protocols

RS 232, V 35 X.25 (56kbps), PADs Frame Relay (up to 45 Mbps), FRADs Asynchronous Transfer Mode (ATM) ISDN (Integrated Services Digital Network) PRI and BRI Dedicated T 1 lines (1.544 Mbps) and Fractional T 1 T 3 (45 Mbps) and OC 3 lines (155 Mbps) ADSL (Asymmetrical Digital Subscriber Line) up to 8

Mbps XDSL (many different types of Digital Subscriber Lines)

Wide Area Networks (WANS)

WANs connect LANs together between cities

Wide Area Networks (WANS) …

The main difference between a MAN and a WAN is that the WAN uses Long Distance Carriers. Otherwise the same protocols and equipment are used as a MAN.

References

1. Introduction to Networking and Data Communications

Eugene Blanchard Edited by Joshua Drake, Bill Randolph and Phuong

Ma2. Computer Networking: A Top-Down Approach

Featuring the Internet Jim Kurose & Keith Ross 3. Internetworking Technology Overview Cisco Systems4. Internetworking Case Studies Cisco Systems

Network Topology

Overview of Network Topologyand

Case Study of Flat Neighborhoods

Goals in Topology Design Reliable and Robust Fast and Efficient Simple and Scalable

Examples of well known designs follow this slide, we shall assume all topologies are using 100 Mbit Ethernet as the medium and rate them on design categories.

Bus Topology Robustness

Efficiency

Simplicity

Scalability

Bus Topology Robustness

Good Efficiency

Good Simplicity

Excellent Scalability

Fair

Ring Topology Robustness

Efficiency

Simplicity

Scalability

Ring Topology Robustness

Poor Efficiency

Good Simplicity

Very Good Scalability

Poor

Star Topology Robustness

Efficiency

Simplicity

Scalability

Star Topology Robustness

Very Good Efficiency

Very Good Simplicity

Poor Scalability

Excellent

A New Topology is Born

In the past, it has been standard to come up with a topology first, and then adapt it to certain tasks. Modern design philosophy has changed this practice. Now a subset of problems or needs gives rise to special task network designs. One such design has been conceived right here at UK.

The Flat Neighborhood Network Brought about by the need to build

a large cluster supercomputer from common networking components.

Driven to evolve from the need for (more) efficient communication between cluster nodes.

The Basics of FNN’sThis example shows how

one could construct a FNN for 6 PCs using just two NICs/PC and three 4-port switches. Note that every PC has at least one single-switch latency path to every other PC; some PC pairs have more than one such path.

Multiple small, interleaved subnets link each machine by a number of one-switch latency paths. Any machine can belong to as many subnets as it has network cards onboard. Sounds simple, but several problems arise from the design.

Some NEW Design Problems

Design of Subnets Routing and

Addressing

Wiring Scheme Efficient use of

Bandwidth

The Solutions:Subnets and Wiring

The wiring scheme and subnets can now be designed by a piece of software developed in the KAOS lab. This problem appears to be NP Complete (Very Bad) and must be solved using a genetic search algorithm. A simplified version allows you to design your own FNN on the web.

http://aggregate.org/FNN/

The Solutions:Genetic Search Algorithm

Generate 256 random networks. Evaluate and rate each based on…

Latency, Bandwidth Balance, Comm. Patterns Throw out bottom 2/3 results and

replace with mutations thereof. Merge Subnets of pairs in top 1/3

results. Re-Evaluate and rate accordingly

The Solutions:Basic Routing

Each machine in the cluster swaps unique identifiers with all of its neighbors at boot up. Address resolution is done locally using the table that this swap generates.

Non-Dynamic Solution

The Implementation: KLAT2 Assembled on April 11, 2000 in the KAOS lab by Dr.

Dietz and Mr. Mattox Fully Functional on April 16 The first working implementation of an FNN

The Main Event:KLAT2 vs. Superdome

KLAT2 vs. SuperdomeRound 1: Cost

KLAT2 Total Value: $41,205 Peak Performance:

64 GFlops $643.83 / GF

Superdome Total Value: $1.5M /

yr Peak Performance:

672 GFlops $2,232.14 / GF / yr

Advantage KLAT2

KLAT2 vs. SuperdomeRound 2: Upgrading

KLAT2 Purchase new Nodes Upgrade the Old

Nodes Recompute Scheme Rewire EVERYTHING

Superdome Purchase a new

Cabinet Plug and Play

Advantage Superdome

The Lowdown FNN’s provide wonderful cost

efficiency, but are plagued by limitations. Number if NIC’s in each node PCI Bus Speed Increased Physical Distance Complexity of Design

Use of KLAT2 KLAT2 is mainly a lab experiment, thus

its practical uses are limited : Insufficient Non-Volatile Storage Weak Back-Up System Slow Internet Connection to the WAN Limited Application Compatability

With further R+D, the FNN cluster may evetually bring about a “supercomputer in every home” movement.

Summary Topology Development Philosophy

has Evolved Special Purpose Topologies use

Networks to Solve Specific Problems

Network Topologies are Always Expanding More Topologies Being Concieved Faster, More Advanced Media

The Credits Dr. Hank Dietz, (859) 257-4701

http://www.engr.uky.edu/ece/faculty/dietz/index.html Mr. Tim Mattox at the KAOS Lab, (859) 257-9695

http://aggregate.org/KAOS/ KAOS Lab Documentation and Publications on FNN’s

http://aggregate.org/FNN/ Dr. Craig Douglas, (859) 257-2326

http://www.ccs.uky.edu/~douglas/ Mr. John Connolly at the UK Center for Computational

Sciences http://www.ccs.uky.edu/~connolly/

UK SDX Home Page http://sdx.uky.edu/

Internetworking Protocol Version 4

(IPv4)

Topics: Why? What? How?

Why IP? Why do we build networks? Why do we need inter-networks?

What is IP? Protocol suit defining an interface

between lower level hardware functionality and higher level application oriented protocols.

Provides a “least common denominator” for all network hardware.

Provides best effort service for datagram delivery from host to host.

How?

How?

Fields

Version(4 bits) – 4Header Length(4 bits) – Size of the

header in 4 byte words.Type of Service(8 bits) – Mostly

unused.Length(16 bits) – Total length of IP

datagram in bytes.

Fields continued Identification(16 bits) – ‘unique’

identifier Flags(3 bits) – 0, Don’t fragment,

More fragments. Fragment Offset(13 bits) – Offset of

fragment in 8 byte words.

Fields continued, again Time To Live (8 bits) – Hop count. Protocol(8 bits) – Higher level

protocol address. Header Checksum – One’s

compliment sum of all 16 bit words in IP header.

Fields, more? Source Address(32 bits) – Where it

came from. Destination Address(32 bits) –

Ummm, you know.

Fields, will it ever end!? Options – options. Padding – even out to 32 bit words.

Fragmentation IP only requires ~500 byte MTU

from hardware layer but allows for packet sizes up to 65535 bytes.

IP datagrams can be fragmented into smaller packets to travel over various networks then reassembled at the destination.

Fragmentation Fragments from the same

datagram carry the same identifier field.

All fragments except the last have the More Fragments bit set.

The Offset Field is an index into the original datagram payload.

IP Addressing Hierarchical (cuz that’s what CS people

do) 32 Bits long. Globally unique (most of the time.) Assigned to network adapter, not host. Composed of network part and host part. Hosts on the same physical network have

the same network address.

IP Addressing Class A - [0][7 Bit Network][24 Bit

Host] Class B - [10][14 Bit Network][16

Bit Host] Class C - [110][21 Bit Network][8

Bit Host]

IP Addressing Classless IP addressing (the way it

really is.) Arbitrarily long network portion

followed by host portion. Can not tell dividing line from IP

address. A netmask is used to divide the

address.

IP Forwarding Each host has a table with tuples of

network addresses, address length, next hop information, and interface information.

To forward an IP packet, find the longest network address that matches destination address.

Send the packet out the corresponding interface to the next hop (may be local.)

IP ForwardingExample:

Interface0 = 128.163.125.2/24

Interface1 = 24.249.125.187/24

Address/Length Next Hop Interface

128.163.125.0/24 Local Interface0

128.168.0.0/16 128.163.125.1 Interface0

24.249.125.0/24 Local Interface1

0.0.0.0/0 24.249.125.1 Interface1

What’s Next? IPv6 128 bit addressing (more people

can play quake.) Fewer fields for simplicity

Overview

Mobility in the Internet Basic Mobile IP Protocol IMHP : Route Optimization in

Mobile IP Other Issues

Mobile Computers’ Characteristics May change point of network

connection frequently May be in use as point of network

connection changes Usually have less powerful CPU, Usually have less powerful CPU,

less memory and disk spaceless memory and disk space Less secure physicallyLess secure physically Limited battery powerLimited battery power

Current State of Mobile Computing Mobile computers are one of the fastest

growing segments of the PC market Short-range wireless networks (Bluetooth)

available from IBM, Toshiba, Dell, HP… High-speed (11 Mbps) wireless LAN products

are now easily and cheaply available (IEEE 802.11a, IEEE 802.11b)

Low speed (currently 128 Kbps) Metropolitan Area Wireless Network services are available in some cities and spreading (Metricom’s Ricochet)

Mobility in the Internet Problem with current IP .It assumes that a node’s IP address

uniquely identifies its point of attachment to the Internet

Mobility alternatives without Mobile IP

.On moving, change IP address Use host-specific routes(using LSR)

to reach mobile hosts .Mobility vs. Portability

Functional Entities in Mobile IP

Functional Entities in Mobile IP : -Mobile Node -Home Agent -Foreign Agent Each mobile node is assigned a unique

home address within its home network When away from home network, it is

assigned a care-of address either by : -Registering with a Foreign Agent -Obtaining a temporary IP address

Basic Mobile IP

F.A.

M.H.

H.A.Correspondent node

Protocol Overview

Agent Discovery Registration Tunneling

Agent Discovery

Extension of ICMP Router Discovery protocol

Used by mobile nodes to discover Foreign Agents and to detect movement from one subnet to another

Mobility Agents (H.A.s and F.A.s) periodically broadcast agent advertisements

Agent Discovery (...contd.)

Mobile node expects to receive periodic advertisements

If it doesn’t receive them, it deduces that either

-it has moved OR -its agent has failed Mobile node can also broadcast

Agent Solicitation messages

Registration Mechanism by which M.H.

communicates reachability info to its H.A.

Registration messages create or modify a mobility binding at a H.A., which is then valid for a certain lifetime period

Uses 2 control messages sent over UDP -Registration Request -Registration Reply

Registration Authentication (..contd.)

Replay Protection : Needed to ensure that registration messages are not replayed by a malicious host. Done using :

-Nonces OR -Timestamps

Registration Authentication

Concern : Forged registrations permit malicious hosts to remotely redirect packets destined for the mobile host

Default authentication between M.H. and H.A. uses MD-5 with a shared secret key

No authentication between M.H. and F.A.

Delivering Datagrams : When the mobile host is away,

H.A. intercepts packets addressed to the M.H. and tunnels them to the M.H.s care-of address

The tunneling scheme could use either of :

- IP-in-IP Encapsulation -‘Minimal’ Encapsulation

Delivering Datagrams (..contd.) Broadcast Datagrams -A H.A. forwards a broadcast datagram

only if the M.H. requested forwarding of broadcast datagrams (in the registration request)

Multicast Datagrams -M.H. can use a local multicast router -M.H. can use a bidirectional tunnel to its

H.A.

IMHP Extension to the basic Mobile IP

protocol that features : -Route Optimization -Authentication of Management packets Defines four entities : -Mobile Hosts -Local Agents -Cache Agents -Home Agents

Route Optimization (IMHP)

Triangle Routing in basic Mobile IP -Limits performance transparency

-Creates bottleneck at Home Agent

H.A.

F.A.

M.H.

Correspondent Node

Route Optimization Eliminates triangle routing Any correspondent node can maintain a binding cache Correspondent node tunnels datagrams directly to the care-off address of the mobile host

F.A.

H.A.

M.H.

Correspondent Node

Binding Management

Four message types : -Binding Warning -Binding Request -Binding Update -Binding Acknowledge Lazy notifications are used

(except MH to HA and previous FA)

Foreign Agent Smooth Handoff

As part of registration, M.H. requests its new F.A. to notify its previous F.A.

New F.A. sends binding update to prev F.A.

Previous F.A. updates its binding cache entry for the M.H. and sends a binding ack.

Authentication of binding update is based on a shared registration key

Special Tunnels

When a F.A. receives a tunneled datagram for a M.H. for which it has no entry, it is tunneled back to the H.A. in a special tunnel

Gives the datagram one more chance of successful delivery

Avoids possible routing loops

Authentication in IMHP

IMHP has simple authentication

procedures which preserve the level of security in today’s Internet

is defined to make use of strong authentication

Authentication in IMHP (..contd.)

M.H. to H.A. authentication -strong authentication based on a

shared secret General Authentication -a random number specified in

binding request is echoed in the reply by the H.A.