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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
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