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Introduction
Chapter 1
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Uses of Computer Networks
Business Applications
Home Applications
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Business Applications of Networks
Client server model
In this model the data are stored on powerful computers called
server.
Users have simple machines called clients, with which they access
remote data.
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Business Applications of Networks (2)
The client-server model involves requests and replies.
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Home Network Applications
Access to remote information
Person-to-person communication
Interactive entertainment
Electronic commerce
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Home Network Applications (3)
Some forms of e-commerce.
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Transmission technology
Two types
Broadcast links Point-to-point links
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Broadcast links
Have a single communication channel shared by all the machines on
the network
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Broadcast Networks (2)
Classification of interconnected processors by scale.
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Personal Area Network
APANis a network that is used for communicating amongcomputers and computer devices (including telephones)in close proximity of around a few meters within a room
PANs can be wired with a computer bus .
PANs can also be wireless through the use ofbluetooth
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A LAN is a networkthatis usedforcommunicating among
computerdevices, usuallywithin an officebuildingor
home (a few hundred meters).
LANs enable the sharing of resourcessuch as files or
hardware devices that may be needed by multiple users
Is fast, with speeds from 10 Mbps to 10 Gbps
Requires little wiring, typically a single cable connecting
to each device
Has lower cost compared to MANs orWANs
Local Area Network
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Local Area Networks
Two broadcast networks
(a) Bus
(b) Ring
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Metropolitan Area Networks
A metropolitan area network based on cable TV.
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Wide Area Networks
Relation between hosts on LANs and the subnet.
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Wide Area Networks (2)
A stream of packets from sender to receiver.
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Network Software
Protocol Hierarchies
Design Issues for the Layers
Connection-Oriented and Connectionless Services
Service Primitives
The Relationship of Services to Protocols
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Network SoftwareProtocol Hierarchies
Layers, protocols, and interfaces.
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Protocol Hierarchies (3)
Example information flow supporting virtual communication in layer 5.
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Design Issues for the Layers
Addressing
Error Control
Flow Control Multiplexing
Routing
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Connection-Oriented and Connectionless
Services
Six different types ofservice.
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Service Primitives
Five service primitives for implementing a simple connection-
oriented service.
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Fundamental Parts of a Network
Network - A network is computers connected together in a waythat allows information to be exchanged between the computers.
Node - A node is anything that is connected to the network.
Segment - A segment is any portion of a network that is
separated, by a switch, bridge or router, from other parts of thenetwork.
Topology - Topology is the way that each node is physicallyconnected to the network. Common topologies include:
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Set of nodes is connected via a shared communication line called
backbone.
Information sent from a node travels along the backbone until it
reaches its destination node
Bus Topology
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The ring network is like a bus network, but the end of the network is
connected to the first node
Nodes in the network use tokens to communicate with each other
A token is attached to the message by the sender to identify which
node should receive the message. as the message moves around the
ring.
Backbone
Ring Topology
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Each node is connected to a device in the center of the network
called a hub
The hub simply passes the signal arriving from any node to the
other nodes in the network
Hub
Star Topology
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Star Bus Topology
S
tar bus - Star bus combines elements of the star and bus topologies .Nodes in particular areas are connected to hubs (creating stars),and the hubs are connected together along the network backbone(like a bus network).
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Reference Models
The OSI Reference Model
The TCP/IPReference Model
A Comparison of OSI and TCP/IP A Critique of the OSI Model and Protocols
A Critique of the TCP/IPReference Model
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Reference Models
The OSI
reference
model.
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Reference Models (2)
The TCP/IP reference model.
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Reference Models (3)
Protocols and networks in the TCP/IP model initially.
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Comparing OSI and TCP/IPModels
Concepts central to the OSI model
Service
s
Interfaces
Protocols
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A Critique of the OSI Model and Protocols
Why OSI did not take over the world
Bad timing
Bad technology Bad implementations
Bad politics
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Bad Timing
The apocalypse of the two elephants.
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A Critique of the TCP/IPReference Model
Problems:
Service, interface, and protocol not distinguished
Not a general model
Host-to-network layer not really a layer No mention of physical and data link layers
Minor protocols deeply entrenched, hard to replace
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Hybrid Model
The hybrid reference model to be used in this book.
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The ARPANET
(a) Structure of the telephone system.
(b) Barans proposed distributed switching system.
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The ARPANET (2)
The original ARPANET design.
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The ARPANET (3)
Growth of the ARPANET (a) December 1969. (b) July 1970.
(c) March 1971. (d) April 1972. (e) September 1972.
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NSFNET
The NSFNET backbone in 1988.
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Internet Usage
Traditional applications (1970 1990)
News
Remote login
File transfer
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ATM Virtual Circuits
A virtual circuit.
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ATM Virtual Circuits (2)
An ATM cell.
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The ATMReference Model
The ATM reference model.
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The ATMReference Model (2)
The ATM layers and sublayers and their functions.
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Ethernet
Architecture of the original Ethernet.
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WirelessLANs
(a) Wireless networking with a base station.
(b) Ad hoc networking.
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WirelessLANs (2)
The range of a single radio may not cover the entire system.
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WirelessLANs (3)
A multicell 802.11 network.
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Network Standardization
WhosWho in the TelecommunicationsWorld
WhosWho in the International StandardsWorld
Who
sW
ho in the Internet StandardsW
orld
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ITU
Main sectors Radiocommunications
Telecommunications Standardization
Development Classes ofMembers
National governments
Sector member
s
Associate members
Regulatory agencies
IEEE 802 St d d
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IEEE 802 Standards
The 802 working groups. The important ones are
marked with *. The ones marked with are
hibernating. The one marked with gave up.
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Metric Units
The principal metric prefixes.