data and computer networks ppt 4877
TRANSCRIPT
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CS3502:CS3502:
Data and Computer Data and Computer NetworksNetworks
INTRODUCTIONINTRODUCTION
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introduction: CS3502introduction: CS3502
overview of computer networks Track
course objectives
homeworks, tests, grading
approximate schedule
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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
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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
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introduction: CS3502introduction: CS3502
network definitions
classifications
models (high level) ISO model
DOD model
IEEE model
purposes of networks
network industries
communication protocols
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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
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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
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network definitionsnetwork definitions
Networks
computer network
distributed network
LAN, MAN, WAN
integrated network
internetwork/Internet
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network classificationnetwork classification
geographical coverage (LAN ... WAN)
topology
switching technique
speed (data rates)
data/information content
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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
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geographical coveragegeographical coverage
MANs
traditional category
cable TV, local phone
DQDB, FDDI (?)
less used, as most networks can be classified into LAN/WAN
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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
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network topologiesnetwork topologies
star
ring
bus
fully connected
tree
mesh
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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)
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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
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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
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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
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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.
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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
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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
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purposes of networkspurposes of networks
resource sharing
increased reliability (redundancy, etc.)
efficiency
communications
future applications: voice, video, data, images, appliances, .... ?
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basic network servicesbasic network services
file transfers (ftp, etc)
remote login (rlogin, telnet)
WWW (web)
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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.
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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”
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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
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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
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standards for networksstandards for networks
reasons for standards
advantages
disadvantages
standards organizations
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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
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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
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communication protocolscommunication protocols
three basic phases of data communications1. connection establishment2. data transfer3. connection termination
connection-oriented/connectionless