CS3502: Data and Computer Networks INTRODUCTION

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Oct 24, 2013 (3 years and 7 months ago)

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CS3502:


Data and Computer Networks


INTRODUCTION








introduction: CS3502


overview of computer networks Track


course objectives


homeworks, tests, grading


approximate schedule

objectives: 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: 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: CS3502


network definitions



classifications



models (high level)


ISO model


DOD model


IEEE model


purposes of networks


network industries


communication protocols

Basic 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 Networks


local, long distance telephone networks


computer LANs: ethernet, token ring


ARPANet/MILNET WANs


Cable TV networks


Cellular phone networks


The INTERNET

network definitions


Networks


computer network


distributed network


LAN, MAN, WAN


integrated network


internetwork/Internet

network classification


geographical coverage (LAN ... WAN)


topology


switching technique


speed (data rates)


data/information content

geographical 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 coverage


MANs


traditional category


cable TV, local phone


DQDB, FDDI (?)


less used, as most networks can be classified
into LAN/WAN

geographical 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 topologies


star


ring


bus


fully connected


tree


mesh

switching 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 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 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
-
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
-
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 model


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


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 networks


resource sharing


increased reliability (redundancy, etc.)


efficiency


communications


future applications: voice, video, data,
images, appliances, .... ?

basic network services


e
-
mail


file transfers (ftp, etc)


remote login (rlogin, telnet)


WWW (web)

network 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 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


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 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 networks


reasons for standards


advantages


disadvantages


standards organizations

communication 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 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 protocols


three basic phases of data
communications


1. connection establishment


2. data transfer


3. connection termination


connection
-
oriented/connectionless