Internetworking and ATM

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Internetworking and ATM

Lecture 8, April 30, 2003

Data Communications and Networks
Mr. Greg Vogl

Uganda Martyrs University

April 30, 2003

Data Communications and Networks:
Lecture 8: Internetworking and ATM

2

Overview

Internetworking

IU A247 Lectures 4, 5

Hodson Ch. 11

BITDCO Lectures 16, 17

ATM

IU A247 Lecture 14

Hodson Ch. 10

BITDCO Lectures 23, 24

April 30, 2003

Data Communications and Networks:
Lecture 8: Internetworking and ATM

3

Uses of Interconnection Devices

Partition an existing network or isolate
a server

For security and performance

Combine existing isolated networks

For communication and consistency

Create a backbone or hierarchy

For organisation, ease of future expansion

Connect a network to a larger network

April 30, 2003

Data Communications and Networks:
Lecture 8: Internetworking and ATM

4

Internetworking and the OSI Model


April 30, 2003

Data Communications and Networks:
Lecture 8: Internetworking and ATM

5

Repeater

Simplest device, OSI physical level

Repeats and increases the signal

Extends range of a IEEE 802.3 LAN

Operates at same speed as the LAN

Retiming, reconstructs preamble

Auto
-
partition to isolate faulty segments

Local, fibre, multi
-
port, or mixed media

April 30, 2003

Data Communications and Networks:
Lecture 8: Internetworking and ATM

6

Bridge

Connects different types of 802 LANs

Works at MAC level (lower Data Link layer)

Connects distant LANs; extends range

Can connect LANs to a backbone

Stores and forwards; buffering

No flow control; delays; buffer overflow

Filters traffic; pass only non
-
local traffic

Improves security, performance of LANs

April 30, 2003

Data Communications and Networks:
Lecture 8: Internetworking and ATM

7

Mechanics of a Bridge

Each port has unique hardware address

Each port has a table to store addresses

Records sender and receiver addresses

Packets only sent if not on local LAN

Translates frames to different protocols

Arranges, removes fields; recalculates CRC

Stand
-
by bridge provides alternate path

Spanning tree algorithm finds, cuts loops

April 30, 2003

Data Communications and Networks:
Lecture 8: Internetworking and ATM

8

Router

Works at network layer of OSI model

Interconnects two or more networks

Administered separately

may be very far apart

Intelligently filters data by user or type

Provides security e.g. acts as a firewall

Provides network management info

e.g. Simple Network Management Protocol

April 30, 2003

Data Communications and Networks:
Lecture 8: Internetworking and ATM

9

Mechanics of a Router

Has an
Internet address

Constant, assigned by administrator

Handles 1 or more
address protocols

e.g. IP (TCP/IP), IPX (IPX/SPX, Novell)

Uses a dynamic
routing protocol

e.g. Routing Information Protocol (RIP)

Stores network addresses in routing tables

Delivers
packets

to next network segment

April 30, 2003

Data Communications and Networks:
Lecture 8: Internetworking and ATM

10

Other Devices

Brouter

A device that can act as a bridge or router

Used in multiple
-
protocol networks

Gateway

A device to connect networks

Works at higher levels of protocol stack

Combination of hardware and software

April 30, 2003

Data Communications and Networks:
Lecture 8: Internetworking and ATM

11

X.25

An old public network run by telecomms

Implemented internationally, up to 64 kbps

Connection
-
oriented (virtual circuit)

Establish call, transfer data, disconnect

Addressing, routing, multiplexing

At network layer

Packet assembly/disassembly standards

X.3 PAD device, X.28 commands for DTE

April 30, 2003

Data Communications and Networks:
Lecture 8: Internetworking and ATM

12

Frame Relay

Another public network technology

Derived from ISDN, used in B
-
ISDN

64 kbps to 2 Mbps, can also carry voice

Permanent virtual circuits

Data Link Connections have IDs

Statistical multiplexing in data link layer

Higher level layers handle errors

April 30, 2003

Data Communications and Networks:
Lecture 8: Internetworking and ATM

13

Fibre Distributed Data Interface

Double ring of fibre optic cable

Similar to token bus and token ring

Primary, secondary rings

Fault tolerance; self healing

Provides backbone capability

Connect with concentrators and bridges

100 Mbps, 2km between active nodes

4 bit/5 bit encoding

April 30, 2003

Data Communications and Networks:
Lecture 8: Internetworking and ATM

14

ATM: Asynchronous Transfer Mode

Fast (155, 622 and 1200 Mbit/s)

Efficient, lightweight

Constant, scaleable bandwidth per user

Seamlessly interconnects LANs, WANs

Devices connect ATM switches to existing LANs

Can emulate LAN connections

Useful for data, voice, audio, images, video

Used for high
-
speed direct server connection

Used to create network backbone

April 30, 2003

Data Communications and Networks:
Lecture 8: Internetworking and ATM

15

ATM Switching

Packet switching

based on B
-
ISDN

Not circuit switching like ISDN

Asynchronous

like a modem

Hardware is synchronous

Error handling at end points

No overhead in the packet itself

April 30, 2003

Data Communications and Networks:
Lecture 8: Internetworking and ATM

16

ATM Implementation

Cells
: small packets with low overhead

5 byte header + 48 byte data = 53 bytes

Request
quality of service
metrics

Peak/min cell rates, delay, loss ratio etc.

Establish uni
-
directional
virtual circuit

Using dynamic routing

Transfer data cells in correct order

Using the virtual circuit

April 30, 2003

Data Communications and Networks:
Lecture 8: Internetworking and ATM

17

ATM Switches

Use shared memory

Buffer/queue for two simultaneous inputs

Routing table

at each input port

Traffic management

Congestion control

Admission control

Resource reservation

Rate
-
based control

April 30, 2003

Data Communications and Networks:
Lecture 8: Internetworking and ATM

18

April 30, 2003

Data Communications and Networks:
Lecture 8: Internetworking and ATM

19

ATM Cell Format

Generic Flow Control

Protocol Connection ID

Virtual Path ID

Virtual Channel ID

Payload Type ID

Cell Loss Priority

Header Error
Correction (CRC)

Data (“payload”)