William Stalling - Slide 01 Intro Notes

8/8/2019 William Stalling - Slide 01 Intro Notes

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EE-4074htt p : / / www.csc.gatech.edu/ ~copeland/ 407 4/

Prof. John A. Copelandjohn.cop [email protected] ech.edu

404 894-5177

Offic e: GCATT Bldg 57 9

email or call for off ice visit, or call Kathy Cheek, 404 894 -56 96

Int roduction

EE4603.01 V1

Text: Local and Met ropolit an Netwo rks,

6t h Edition

by William Stallings

The class Web sit e is:htt p:/ / www.csc.gat ech.edu/ ~copeland/ 460 3/

On t his site you will find (event ually):

Class calendar (t est dat es, etc.)

Reading assignment s

Lect ure Notes (pdf f i les to print)

Homework assignments ( and answers), a Q&A folder

Homework assignment s will be t ext f iles, sent

by email and posted on t he Web. Answers

will be edited int o t hem, and t hey will be

ret urned by email to me.

Grades will be sent t o you by email.

Uses of Comput er Net works

Tradit ional ( several years old)

Access to cent ral databases

Synchronization of distributed data

Client -Server Model (r equest- reply)

Collaborative w ork groups ( e.g., Lotus Not es)

New Uses

Human Communicat ion (em ail, games, news groups,

class Web sit es)

Access t o many sources of inform ation ( World Wide

Web - t ext, image, sound, video, ...)

Real-time information (traffic cameras)


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Communication Netw orks

Problem: Use digit al informat ion generated by one

computer on anot her computer wit hout retyping.

Early solut ions: Paper t ape, punched cards, magnetict ape, floppy disks, cdroms, .... -> " sneaker net "

Problem: Users want t o use remot e computer t o

access informat ion.

Early solut ions: Terminal directly wired t o a " main

frame" computer. Desktop uses a "modem" wit h phone

dial up. Limited t o one connection at a time.

Recent solution t o bot h: Connection by a "real t ime"

data communicat ion networ k . Remot e dial upconnections t o net work v ia modem and ISDN "Terminal

Adapt or" allow mult iple "virt ual circuit s."

Connect devices by point t o point l inks.

Reasonable when t he number of connect ions are small, anddistances are small.

Not reasonable when the number of connect ions are large, anddistances are large. C = n*(n-1 )/ 2.

TransmissionMedium

Data Communicat ion Net work

Connect each device (st ation, host , server) t o a "node". Nodes do

not generate information; only transport information (bit s) t o/

from ot her nodes

Node


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Classificat ion of Communicat ion Net works

Communication

Network

Packet

Broadcast

Network

Packet Terrestrial Radio

Sat ellite Radio Netwo rk

Local Area Networ k

Switched

Network

Circuit -

SwitchedNetwork

Packet -Switched

Network

Virtual-Circuit

Network

Datagram

Network


Communication

Network

Packet

Broadcast

Network

Packet Terrestrial

Radio

Sat ellit e Radio

Net work

Local Area Net work

Switched

Network

Circuit-

Swit chedNetwork

Packet -Switched

Network

Virt ual-

CircuitNetwork

Datagram

Network

Packet Broadcast Netw ork

In a Broadcast Network, t here are no intermediat e switchingnodes.

- Each stat ion has a t ransmitt er/ receiver t hat communicates

over a medium shared by other st ations.- Transmission from any st ation is received by all otherstations.

Topologies of broadcast networks:

TerrestrialRadio

Satell ite Network

Ring Netwo rk

Bus Netw ork


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Communication

Network

Packet

Broadcast

Network


Sat ellit e Radio Network

Local Area Network

Swit ched

Network

Circuit -

SwitchedNetwork

Packet -Switched

Network

Virtual-Circuit

Network

Datagram

Network

Swit ched Communicat ion Netw ork A Switched Communication Network consists of an interconnected

collection of swit ches (nodes). Dat a is routed from swit ch to

switch on dedicat ed channels, forming a circuit (or connect ion).Circuit s are "set up" and "t aken down."

4E

3A

5

C

D

B

1

7

6

2

St ation

1

7

6

2

Circuit A -D

A

1 Switch or Node

Local Connect ion

Trunk or Long -Haul


Communication

Network

Packet

Broadcast

Network


Sat ellit e Radio Network

Local Area Network

Swit ched

Network

Circuit-

Swit ched

Network

Packet-

Swit ched

Network

Virtual-

Circuit

Net work

Dat agram

Network


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The Swit ching Met hod of a Swit ched

Communication Networ k is t he way

data are processed and routed in t hat

network.

The basic met hods are:

- Circuit Swit ching

- Packet Swit ching

> Dat agram Packet Swit ching

Swit ched

Network

Circuit-

Swit ched

Net work

Packet-

Swit ched

Net work

Virtual-

Circuit

Network

Dat agram

Network

Circuit Swit ching In a circuit-swit ched net work, a dedicated

communication path is established between t wo

stat ions t hrough nodes (switches) of t he

network.

Dat a is t ransport ed at a fixed bit rate on t hese

paths.

A circuit swit ched connect ion (circuit) occupies

a fixed capacity ( bandwidth, bits per second) ofeach link for the lifet ime of t he connection.

Capacit y unused by t he circuit cannot be used by

ot her circuits.

Circuit-swit ched communicat ion involves three

phases:

- Circuit establishment (Dial - call set up)

- Dat a Transfer (Talk)

- Circuit disconnect (Hang up -call take down)

Circuit-Swit ched

Net work

Address Data Erro r Check

Data Packet

Packet Swit ching

Dat a are sent in a sequence of " chunks" , so-called

packets.

Each packet is passed through t he net work fr om

node t o node along some pat h ( route).

At each node the ent ire packet is received, stored

briefly, queued with ot her packet s going t o the

same next node, and then forwarded t o t he next

node ( store and forward network ).

Choice of t he next node depends on the " address"

within t he packet.

The met hod of selection of t he rout e depends on

whether t he packet is a "Datagram" or is part of a

"v irtual circuit."

Packet-

Swit ched

Network


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Communication

Network

PacketBroadcast

Network


Satellite Radio Network

Local Area Network

Switched

Network

Circuit-

SwitchedNetwork

Packet-

Swit ched

Net work

Virt ual-

Circuit

Network

Datagram

Net work

Dat agram Packet Swit ching

Packet s are routed independent ly of each other.

Packet s are called Dat agrams, because they areindependent m essages.

Due to independent rout ing, dat agrams may arrive out oforder (out -of-sequence delivery).

4E

3A

5

C

D

B

1

7

6

2

Virt ual-Circuit Packet Swit ching

4E

3A

5

C

D

B

1

7

6

2

All packets fr om one packet st ream (same source and

destinat ion addresses) are sent along the same pat h.

Virt ual-circuit switc hing guarantees in-sequencedelivery of packet s.

Packets from different virtual circuits are int erleaved.

Circuit -swit ched communication involves three phases:

Circuit Establishment , Dat a Transfer , CircuitDisconnect .


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Communication

Network

Packet

Broadcast

Network


Sat ellite Radio Netwo rk

Local Area Networ k

Switched

Network

Circuit -

SwitchedNetwork

Packet -Switched

Network

Virtual-Circuit

Network

Datagram

Network

Documents

William Stalling - Slide 01 Intro Notes