EEC-682/782 Syllabus Computer Networks I Definitionacademic.csuohio.edu/zhao_w/teaching/Old/EEC682-S0… · · 2005-01-25Store and forward or packet switch ... Computer Networks

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EEC-682/782Computer Networks I

Lecture 1

Wenbing [email protected]

(Lecture nodes are based on materials supplied by Dr. Louise Moser at UCSB and Prentice-Hall)

Spring Semester 2005EEC-682: Computer Networks I

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Outline

SyllabusIntroduction to computer networks

DefinitionUses of computer networksNetwork hardwareNetwork software


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Course ObjectivesBecome familiar with the basics of computer networks

What is a computer networkWhat are the network architecturesWhat are the fundamental protocols

Get some hands-on experiences Learn some basic network computing techniques


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Outline of Lectures

Introduction to computer networksPhysical layerData link layerMedium access control sublayerNetwork layerTransport layerApplication layerNetwork security

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Outline of assignments

Assignment 1: Sockets for inter-process communicationLearn some basic network programming skills

Assignment 2: Set up your Web homepageOptional project

Must be implementation related, potential projectsImplementation of a group communication systemImplementation of a reliable point-to-point transport service that resembles TCP in the user space using UDPBuild a switch using a PC and a few network interface cards

Can substitute for a midterm/final exam, or enhance your grade


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Grading PolicyGrade components & relative weights:

Class participants: 5%Assignments: 20%

No group is allowed, must do the assignments independentlyLate turn-in accepted, but with penalties

1st midterm exams: 25% (chapters 1-4)2nd midterm exams: 20% (chapters 5-6)Final exam: 30% (chapters 1-8)Exams are all closed-book closed-notesOptional project: can substitute one exam, or 25% extra

Individual projectA demo, detailed report, and source code required

Do not cheat!Do not copy other student’s homework, exams or projectDo not copy someone else’s work found on the Internet

Including project implementation and reportYou can quote a sentence or two, but put those in quote and give referenceYou can build your project or homework on top of open source libraries, but again, you need to explicitly give acknowledgement and state clearly which parts are implemented by you


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Reference TextsAndrew S. Tanenbaum :

“Computer Networks”4th Edition, Prentice-Hall, 2003

Richard Stevens:“Unix Network Programming: Volume 1 Sockets and XTI”

2nd Edition, 1998

Andrew S. Tanenbaum and Marten van Steen:“Distributed Systems: Principles and Paradigms”

Prentice-Hall, 2002


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Misc

Instructor:Dr. Wenbing Zhao

e-mail: [email protected] hours:

TTh 6:00-7:50pmOffice hours: TTh 4:00-6:00pm and by appointment

Networking Lab (SH 306)Upon request, I can create account on the lab machines for youCan remotely login

Course Web site:http://academic.csuohio.edu/zhao_w/teaching/eec682.htmLecture nodes and homework will be posted

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Introduction of Computer Networks

Uses of computer networksNetwork HardwareNetwork software


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Definition of Computer Network

Interconnected collection of autonomous computersInterconnected – able to exchange info via copper wire, fiber, microwaves, satellites, etc.Autonomous – act independentlySingle network vs. network of networks


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Computer Network vs Distributed SystemDistributed system - A collection of independent computers that appear to the users as a single coherent system

software specifically designed to provide an integrated computing facilityTwo aspects (1) independent computers and (2) single system ⇒ middleware

Computer network – User must handle network management explicitly


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Uses of Computer Networks

Business applicationsHome applicationsMobile usersSocial issues

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Business Applications of Networks

Goals of using computer networks for businessResource sharingProvide powerful communication medium among employeesDoing business electronically with other companiesDoing business with consumers over the Internet (e-commence)


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Resource SharingResource sharing

equipment, software programs, dataClient-server model

Server – provides services for clientsA network with two clients and one server.


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Client-Server Model

The client-server model involves requests and replies.


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Home Network Applications

Access to remote informationWWW, online newspapers, sports news

Person-to-person communicationInstant messaging, chat room, peer-to-peer communication/file sharing

Interactive entertainmentVideo on demand, game playing

Electronic commerceOnline banking, online auction, etc.

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In peer-to-peer system there are no fixed clients and servers.


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Some forms of e-commerce.


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Mobile Network UsersWireless network

Portable office, military, taxis, trucksFixed wireless, mobile wireless

Combinations of wireless networks and mobile computing

Future applicationsWireless parking meters, vending machine inventory report, utility meter reading, merge of cell phones and PDAs, m-commerce, personal area networks and wearable computersSmart watches, smart dust


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Social Issues

Offending contentCopyright violationsSpamsVirusesWho is responsible?

Network operator? Software provider? Users?What kind of control is appropriate?

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Network Hardware

No generally accepted taxonomy. Two dimensionsTransmission technologyScale

Transmission technologyBroadcast linksPoint-to-point links (unicasting)

ScalePersonal area networksLocal area networksMetropolitan area networksWide area networksThe Internet


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Classification by Scale


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Local Area Networks

LAN typically spans a room, a building or a campusLANs are distinguished from other kinds of networks by three characteristics

Size – restricted in size => worst-case transmission time is boundedTransmission technology – typically using broadcast

Static and dynamic broadcast channel allocationTopology


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Local Area Networks

Two broadcast networks(a) Bus(b) Ring

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Metropolitan Area NetworksMAN covers a cityA metropolitan area network based on cable TV.


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Wide Area Networks

Spans a large geographical area, often a country or continentNetwork structure in WAN

Host or end systemCollection of machines that run user (application) programs

Communication Subnet – connects hostsTwo distinct components

Transmission lines – move bits (circuits, channels, trunks)Routers or switching elements that connect two or more transmission lines

Two types of designsPoint-to-point channelsBroadcast channels


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Wide Area Networks

Relation between hosts on LANs and the subnet.


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Wide Area Networks

Point-to-point channelsStore and forward or packet switchIf no direct connection, must use intermediate switching elements where store packets until required output line is free and then forwardMany different topologies – ring, star, tree, irregular

ring star tree irregular

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Wide Area Networks

A stream of packets from sender to receiver.


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Wide Area NetworksBroadcast channels

Sent by one, received by allAddress field specifies intended destinations

Multicast if more than one destinationWhen machine receives packet, checks address ignores if not for itTopologies

ringbus satellite


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Wide Area Networks

Broadcast channelsNeed to arbitrate simultaneous access to mediumTwo approaches

Static Divide time into slots, use round robin strategyWaste channel capacity when nothing to send

DynamicCentralized – bus arbitration unit decides who goes nextDecentralized – each machine decides for itself

A B C A B C


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Wireless Networks

Categories of wireless networksSystem interconnectionWireless LANsWireless WANs

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Wireless Networks(a) Bluetooth configuration(b) Wireless LAN


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Wireless Networks

(a) Individual mobile computers(b) A flying LAN


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Home Network CategoriesComputers

Desktop PC, PDA, shared peripheralsEntertainment

TV, DVD, VCR, camera, stereo, MP3Telecomm

Telephone, cell phone, intercom, faxAppliances

Microwave, fridge, clock, furnace, air conditionerTelemetry

Utility meter, burglar alarm, babycam


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Network SoftwareProtocol hierarchies / Network architecturesDesign issues for the layersConnection-oriented and connectionless servicesService primitivesThe relationship of services to protocols

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Protocol HierarchiesProtocol hierarchies are organized into layers or levels with different protocols at each layerEach layer offers certain services to higher layers, hiding the details of implementation of those servicesLayer n on one machine communicates with layer n on another machineInterface between adjacent layers defines operations and services offered by lower layer to upper layer


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Protocol HierarchiesLayers, protocols, and interfaces.


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Network Architectures

Network Architecture - A set of layers and protocolsMust contain enough information for implementationDoes not contain details of the implementation and specification of the interfacesIt is not even necessary that the interfaces on all machines in a network be the same

Protocol Stack - A list of protocols used by a certain system, one protocol per layerThe subjects of network architectures, protocols stacks, and the protocols themselves are the principal topics of this course


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Protocol HierarchiesThe philosopher-translator-secretary architecture.

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Protocol HierarchiesExample information flow supporting virtual communication in layer 5.


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Design Issues for the Layers

Each layer needsMechanisms for

connection establishment and addressingConnection termination or release

Rules for data transferSimplex – one directionHalf duplex – either direction, but not simultaneouslyFull duplex – both directions simultaneouslyNumber of logical channels and their priority

Error controlError detecting and correcting codesPositive and negative acksRe-sequencing packets that arrives out of order


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Design Issues for the Layers

Each layer needsFlow control

Need to keep a fast sender from swamping a slow receiverUse feedback from receiver to sender

Finite buffersInability of receiver to accept arbitrarily long messagesUse mechanisms for disassembling, transmitting, reassembling

MultiplexingSeveral unrelated conversations between pair of communicating processes

RoutingWhich route to use if there are several


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Connection-Oriented and Connectionless Services

Connection-oriented serviceModeled after telephone system – establish connection before communicationSome service allow a negotiation among sender, receiver and subnet regarding the parameters to be used, such as max message size, etc.

Connectionless serviceModeled after postal system – a message carries full destination address, and each one is routed through the system independent of all the others

Ordering of messages are not guaranteed

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Quality of service – characterize each serviceReliable service – it does not lose data

Implemented by having the receiver acknowledge the receipt of each messageThe acknowledgement process introduces overhead and delaysTwo variations

Message sequences – message boundaries are preservedByte streams – message boundaries are not preserved

Example: file transferUnreliable connectionless service – datagram service

No acknowledgement is usedIn analogy with telegram service

Acknowledged datagram serviceLike sending a registered letter and requesting a return receipt

Request-reply service – used in client/server model


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Six different types of service.


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Service Primitives

Five service primitives for implementing a simple connection-oriented service.


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Service PrimitivesPackets sent in a simple client-server interaction on a connection-oriented network.

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Relationship of Services to Protocols

Services and protocols are distinct conceptsA service is a set of primitives (operations) that a layer provides to the layer above it

Defines what operations the layer is prepared to perform on behalf of its usersHow service is implemented is not revealed (hidden)Relates to an interface between two layers, with lower layer being the service provider and the upper layer being service user

A protocol is a set of rules governing the format and meaning ofthe packets, or messages that are exchanged by the peer entities within a layer

Entities use protocols to implement their service definitionsDifferent protocol could be used to provide the same serviceProtocol and service are completely decoupled


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Relationship of Services to Protocols

The relationship between a service and a protocol.

Documents

EEC-682/782 Syllabus Computer Networks I Definitionacademic.csuohio.edu/zhao_w/teaching/Old/EEC682-S0… · · 2005-01-25Store and forward or packet switch ... Computer Networks