Computer Networks

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Introduction
Computer Networks
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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.

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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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Network Topologies
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Transmission Media

• Wireline
• String
• Garden Hose
• Copper
• Twisted Pair
• Coax
• Optical Fiber

• Wireless
• Sound
• Light and mirrors
• Infrared
• RF
• Microwave

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Network Scope

• Local Area Network (LAN)
• Metropolitan Area Network (MAN)
• Wide Area Network (WAN)

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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

• Data Transfer

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Circuit Switching versus Packet Switching

• Dedicated
• fixed bandwidth
• route fixed at setup
• idle capacity wasted
• network state

• Best Effort
• 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 Application Layer
• 6 Presentation Layer
• 5 Session Layer
• 4 Transport Layer
• 3 Network Layer
• 2 Data link Layer
• 1 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 Application Layer
• 4 Transport Layer
• 3 Network Layer
• 2 Data link Layer
• 1 Physical Layer

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TCP/IP versus OSI

• "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 ltxgt 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/