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Introduction
Computer Networks
Spring 2000
John Kristoff
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Motivation and Scope
Computer networks and internets: an
overview of concepts, terminology and
technologies that form the basis for digital
communication in private corporate
networks the the global Internet.
Spring 2000
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Motivation for Networks
Information Access
Sharing of Resources
Facilitate Communications
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What a Network Includes
Transmission hardware
Special-purpose hardware devices
interconnect transmission media
control transmission
run protocol software
Protocol software
encodes and formats data
detects and corrects problems
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What a Network Does
Provides communication that is
Reliable
Fair
Efficient
From one application to another
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What a Network Does
[continued]
Automatically detects and corrects
Data corruption
Data loss
Duplication
Out-of-order delivery
Automatically finds optimal path from
source to destination
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Data Communication versus Networking
With only two nodes, mostly EE issues.
With more than two nodes, lot more issues!
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Direction of Transmission
Point to Point
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Broadcast
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Network Topologies
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Transmission Media
Wireline
Wireless
String
Garden Hose
Copper
Sound
Light and mirrors
Infrared
RF
Microwave
Twisted Pair
Coax
Optical Fiber
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Network Scope
Local Area Network (LAN)
Metropolitan Area Network (MAN)
Wide Area Network (WAN)
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Data Transmission
Serial
Parallel
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Multiplexing
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Communication Modes
Simplex
Half-duplex
Full-duplex
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Connection-oriented
versus Connectionless
Connection Setup
Data Transfer
Connection
Termination
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Data Transfer
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Circuit Switching versus
Packet Switching
Dedicated
Best Effort
fixed bandwidth
route fixed at setup
idle capacity wasted
network state
Spring 2000
end-to-end control
multiplexing technique
re-route capability
congestion problems
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Examples
Public Switched Telephone Network
Internet
Postal Service
Train
Car and highway system
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Standards
Hardware
Software
Protocols
Advantages and Disadvantages
Proprietary, De Facto, De Jure
Standards Bodies
IETF, IEEE, OSI, ANSI, ATM Forum, etc.
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Protocols
Rules, standards and etiquette
Metric System
English
Dinner party
Morse Code
TCP/IP
HTML
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Layering
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Headers, Data and Trailers
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Encapsulation
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ISO OSI Reference Model
7:
6:
5:
4:
3:
2:
1:
Application Layer
Presentation Layer
Session Layer
Transport Layer
Network Layer
Data link Layer
Physical Layer
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Interfaces and Services
PDUs
SDUs
SAPs
Peer communications
Service Primitives
etc... read Tanenbaum 1.3.3 and 1.3.5
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TCP/IP Model
5:
4:
3:
2:
1:
Application Layer
Transport Layer
Network Layer
Data link Layer
Physical Layer
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OSI versus TCP/IP
“Rough consensus and running code”
Simplicity
Time to market
Availability
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Network Classification
Physical medium: copper, fiber, wireless
Scope: LAN, MAN, WAN
Topology: bus, star, ring, mesh
Switching style: circuit, packet
Application: voice, data, video
Protocol: IP, OSI, Ethernet, ATM
Transmission rate: 10Mb/s, Gigabit
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Terms I (we) Often Use
Frames: think data link layer
Packets: think network layer
Datagrams: think IP
Segments: think TCP
Cells: think ATM
Layer <x>: refer to reference models
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The End-to-End Argument
“End-to-End Arguments in System Design”
J.H. Saltzer, D.P. Reed, and D.D. Clark
http://web.mit.edu/Saltzer/www/publications
/
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