CS3502:CS3502:

Data and Computer Data and Computer NetworksNetworks

INTRODUCTIONINTRODUCTION

introduction: CS3502introduction: CS3502

overview of computer networks Track

course objectives homeworks, tests, grading approximate schedule

objectives: CS3502objectives: CS3502 gain good overview of networking detailed knowledge of

physical layer data link layer local area networks

elementary protocol specification and analysis

elementary performance analysis

homeworks, etc: CS3502homeworks, etc: CS3502 homeworks passed out in class OR in

electronic form. NOT GRADED. solutions for majority of homeworks

provided. 3 tests spaced roughly 1/3 of quarter tests based - in order of priority- on

homeworks class notes, lectures text

introduction: CS3502introduction: CS3502 network definitions classifications models (high level)

ISO model DOD model IEEE model

purposes of networks network industries communication protocols

Basic TermsBasic Terms Communication Information Data Node Data

Communication Data Processing

- moving information from one physical node to another

- data

- a pattern of 0’s and 1’s

- a physical system for holding information

- moving data from one physical node to another

- changing data within a node

Examples of NetworksExamples of Networks local, long distance telephone

networks computer LANs: ethernet, token ring ARPANet/MILNET WANs Cable TV networks Cellular phone networks The INTERNET

network definitionsnetwork definitions Networks computer network distributed network LAN, MAN, WAN integrated network internetwork/Internet

network classificationnetwork classification geographical coverage (LAN ...

WAN) topology switching technique speed (data rates) data/information content

geographical coveragegeographical coverage

LANs simpler, less software layers higher data transfer rates (generally) simple routing IEEE standards easily connected together via bridges examples: ethernet, token ring, FDDI

geographical coveragegeographical coverage MANs

traditional category cable TV, local phone DQDB, FDDI (?) less used, as most networks can be

classified into LAN/WAN

geographical coveragegeographical coverage WANs

data speeds slower, in general (this distinction fading)

national, international boundaries includes internetworking ARPANet first example much more complex software OSI model

network topologiesnetwork topologies

star ring bus fully connected tree mesh

switching techniquesswitching techniques broadcast

no switching or routing; 1 station transmits, all others can receive

collisions occur if more than 1 attempts to transmit at once

examples: ethernet LAN and radio networks, satellites (to some degree)

switching techniquesswitching techniques

circuit switching 3 distinct phases traditional voice network nice for user, but inefficient use of

transmission facilities served traditional voice networks

well, but gradually becoming outdated by new technology

switching techniquesswitching techniques message switching

sends entire message as single transmission

efficiency problems from unbound msg. size packet switching

fixed packet size much more efficient use of facilities several refinements; fast packet switching

(ATM) is culmination

network model: ISO 7-layersnetwork model: ISO 7-layers

designed ~1970; still heavily referenced 7 layer model for networks --

1. physical - moves a bit from a to b using a physical(electrical, optical, etc.) signal

2. data link - groups bits into frames, or messages, for error control and information

3. network - routing function

network model: ISO 7-layersnetwork model: ISO 7-layers

4. transport - end to end; interface between user apps and the network/internet

5. session, presentation - ??

7. application - user interface to network, and user services: email, file transfer, world wide web, etc.

network model: IEEE LAN network model: IEEE LAN modelmodel

complements ISO model for LAN specific networks;

more specific in data link, physical layers; other layers unchanged

layers: physical MAC: media access control LLC: logical link control

network model: DoD model network model: DoD model

Alternative view; viewed networks as basic building blocks, thus not included in model

Fewer layers Applications host-host (transport; now TCP ) internet layer (now IP) network interface layer

purposes of networkspurposes of networks

resource sharing increased reliability (redundancy, etc.) efficiency communications future applications: voice, video,

data, images, appliances, .... ?

basic network servicesbasic network services

e-mail file transfers (ftp, etc) remote login (rlogin, telnet) WWW (web)

network ing industrynetwork ing industry

historically two separate and very different industries -- computers and communications

computer industry: IBM, DEC, Sun, Apple, Cray, SGI, Compaq, Dell, Gateway, Microsoft, etc

communications: AT&T, Sprint, MCI-WorldCom, RBOCs, GTE, other phone companies, etc.

network ing industrynetwork ing industry

these 2 industries have been merging signs of the merging

initial purpose of each signals importance of each to the other research labs Sun’s logo “the network is the computer”

industry sectors industry sectors

Computer Industry mainframes, “big” computers - IBM, Cray mid-size, workstations - Sun, SGI, (DEC,

Tandem) personal computers (manufacurers) -

Compaq, Dell, Gateway PCs - software - Microsoft semiconductors for PCs - Intel, AMD, NSM

industry sectorsindustry sectors Communications

long distance telephone (ATT, Sprint) local telephone (Pacific Bell, etc.) telecom. equipment (Lucent, Nor.

Telecom) telco eqmt (Lucent, etc.) data; internet (Cisco, 3Com)

internet service providers (AOL, etc) radio, wireless data, satelite, etc

standards for networksstandards for networks

reasons for standards advantages disadvantages standards organizations

communication protocolscommunication protocols protocol: the algorithm or procedure

used for communication between processes at the same layer

examples: telephone call; e-mail protocol processes make use of

lower layers as a service. heart of communications process

communication protocolscommunication protocols some things protocols do

bit interpretation to signals group bits into messages error detection and correction synchronization make more efficient use of networks

facilities

communication protocolscommunication protocols

three basic phases of data communications1. connection establishment2. data transfer3. connection termination

connection-oriented/connectionless