Computer Networks

Major Muhammad Faisal AmjadCS Dept

CPS 422

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Internet………

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Everyone uses it

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We want it Everywhere

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Even at our fingertips

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We even call and meet each other over the Internet

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Why should TV be an exception

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World has become a global village because of the InternetSo… What is Internet ???It is a collection of a very large number of “inter-connected NETWORKS” that connect millions of “devices” that can “communicate”with each otherAnd why should we study networks

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What is this course about?

Introductory (first) course in computer networkingLearn principles and Architecture of computer networkingThis is NOT a course on network building or specific usage, HoweverInternet architecture/protocols will be studied to understand networking principles.

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What is this course about?Goals:

learn a lot (not just facts, but principles)enjoy learning Computer Networks (Not as a burden)be able to make intelligent decisions about network design, use and managementbe able to pick up and learn details of a particular system as you need itbe able to quickly find protocol descriptions and problemsolutionsbe able to discuss data communication systems with supervisors and co-workers on the job (and may be impress them with high sounding technical jargons)

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Course InformationWho is this course for?o Undergrads of TE and BESE

Prerequisites:o Willingness to work hard (for survival in this course and ultimately

in your profession)Course materials:o text: Data and Computer Communications By William Stallings

Fifth Editiono text: Data Communications and Networking By Behrouz

Forouzan, Third Editiono Other Ref books (if necessary) will be indicated during the course.o WWW readings.o Class notes

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Course Information

Coursework amount %ageWritten assignments as needed 10%Announced / unannounced quizzes as needed 10%Midterm Exam 1 30%Final exam 1 50%

Workload:

Credit Hours: 3+1

Missing quizzes / assignments / exam will land you into trouble. DON’T MISS THEM.

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Course Conduct

Networking is a Vast subject and only key concepts can be covered in the class.You are expected to read the rest from the book and other refs.Feel free to ask questions during the class about any concepts that are not clear.Material covered in the class will include someconcepts from other textbooks. Please pay attention to the class discussion.

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Course OutlineNetworking OverviewLayered Approach to Network ArchitectureComparison of OSI and TCP/IP architecturePhysical Layer (Will not be covered in detail since Analog & Digital Comm has already been studied)o Analog / Digital Communicationo Transmission Mediao Data Encodingo Interfacingo Multiplexingo Packet Switching / Circuit Switching

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Course Outline (Contd…)

Data Link Layero Error Detection / Correction / Controlo Elementary Data Link Protocolso Sliding Window Protocolso MAC Sub-layer

MAC Protocols (CSMA, ALOHA, WLANs etc.)IEEE 802 Standards for LANsBridgesHigh Speed LANs

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Course Outline (Contd…)

The Network Layero Internetworking Conceptso Internet Addressingo ARPo IP – Connectionless Datagram Deliveryo Routingo IP – Error and Control (ICMP)o Subnet and Subnet Extension

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Course Outline (Contd…)

The Transport Layero Process – to – Process Deliveryo User Datagram Protocol (UDP)o Transmission Control Protocol (TCP)o Congestion Controlo Quality of Service (QoS)

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Course Outline (Contd…)

The Application Layero Client-Server Model and the Socket Interfaceo Domain Name System (DNS)o E-mail (SMTP) and File Transfer (FTP)o HTTP and the WWW

Network Security

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Networking Overview

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Data CommunicationData Communication is the exchange of data between two devices via some form of transmission mediumFundamental characteristics of data communication:o Delivery – to correct destinationo Accuracy – without errorso TimelinessComponents of data communication:o Messageo Sendero Receivero Mediumo Protocol

Message

Step 1Step 2Step 3…….

Step 1Step 2Step 3…….

Protocol Protocol

SenderReceiver

Transmission Medium

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Simplified Communication Model

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Simplified Data Communication Model

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Direction / Timing of Data Flow

o Simplex

o Half Duplex

o Full Duplex

Direction of Data

Mainframe

Monitor

Data Direction at time 1Workstation

Workstation

Data Direction at time 2

Data Direction at all timesWorkstation

Workstation

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Protocol

A protocol is a set of rules that governs data communications. It represents an agreement between the communicating devices.Without protocol, devices may be connected but not communicating.

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Example protocolsa human protocol and a computer network protocol:

Get http://www.mcs.edu.pk/index.htm

TCP connectionreq.

TCP connectionreply.

<file>time

Hi

HiGot thetime?2:00

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Network CriteriaPerformanceo e.g. transit time, response timeo Depends upon media, no of users, hardware

capabilities, software efficiency etc.Reliabilityo Freq of failureo Failure recoveryo Robustness in a catastrophe

Security

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Network TopologiesMeshStarBusRing

Network Topologies

Mesh Star Bus Ring

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Mesh Topology

•A fully connected mesh network has n(n-1)/2 physical links to connect n devicesIs the network in figure above a fully connected mesh ?

•No of I/O ports required

•Ease of installation / reconfigure

•Link failure

•Availability of link BW

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Star Topology

HUB / Switch

•No of I/O ports required

•Ease of installation / reconfigure

•Link failure

•Availability of link BW

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Bus Topology

Tap Tap Tap Tap

•No of I/O ports required

•Ease of installation / reconfigure

•Link failure

•Availability of link BW

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Ring Topology•No of I/O ports required

•Ease of installation / reconfigure

•Link failure

•Availability of link BW

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Network CategoriesLocal Area Network (LAN)Metropolitan Area Network (MAN)Wide Area Network (WAN)

Network Categories

LAN MAN WAN

Can you name some other Network Categories ?(Within a few buildings) (Within a city) (Across many cities)

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An ExampleNetworkingConfiguration

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Internet StandardsAn Internet Standard is a thoroughly tested specification that is useful to and adhered to by those who work on the Internet.Any specification begins as an Internet Draft which is a working document (work-in-progress) with no official status and a 6-month lifetime.Upon recommendation from Internet authorities, a Draft may be published as a Request For Comment (RFC). Each RFC is edited, assigned a number and made available to all interested parties.

Visit the URL http://www.ietf.org

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Assignment # 1 (Due: Thur 27th Mar 2009)

Give advantages / disadvantages of various network topologies studied.Find out and list other network categories (e.g. LAN/MAN). Give a very brief (2-3 lines) explanation of each.Find out Two Internet Drafts and Two RFCs from the Internet, Give their numbers/names, Topics and their author(s) names.

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