microsoft powerpoint - it640-session17-networking basics-2005

IT 640 Modern Information Systems

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Dr Deepak B PhatakSubrao Nilekani Chair Professor

Kanwal Rekhi School of Information TechnologyIIT Bombay

Session 17, Networking Basics

IT640-Session 17, Networking BasicsDr. Deepak B Phatak 2

SESSION OVERVIEW

Internet TechnologiesNetworking Basics

ObjectivesLAN and WANIntroduction to Principles of NetworkingLayered Model


Internet Technologies

Internet and Web Permits Access to Information That is Stored on Different Computers (Servers) Across the WorldThis Accessibility Can be Incorporated as a Component of Information Systems


Networking Objectives

Resource SharingDistributed Data Bases Possible

High ReliabilityAs Good as a Single System

Cost EffectivenessAffordable Information Systems Possible

ScalabilityNumber of Users, Number of Transactions


Scale of Networks

0.1 M Circuit Board1 M Computer System10 M Room100 M Building1 Km Campus10 Km City100 10000 Km Countries

LAN

WAN


Networking Basics

Permit Exchange of InformationThrough Communication Between any Two Computer Systems on the NetworkHandling Information

Broken into Smaller Chunks (Packets) by Sender, and Reassembled by Receiver


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Networking Basics

Handling CommunicationNetwork Must Ensure that All Packets of Information (Eventually) Reach the DestinationAddressing Mechanism Needed for NodesCommunication Protocol NeededInternational Standards Exist

IEEE 802.X


Networking Basics

Each Computer Node Must Have:Hardware to Connect to Network

Network Interface Card (NIC)

Software to CommunicateProtocol Suite (Such as TCP/IP)

Some Medium to Carry SignalsCables, Radio,


Network Types

Broadcast NetworksSingle Communication Channel Shared by Multiple MachinesPackets Sent by One System With a Destination AddressPacket Handled Only by Addressee, Ignored By Other Systems


Broadcast Networks

Packets Can be Addressed to ALL Systems

True Broadcast

Or Can Be Addressed To a Subset of Systems

Multicast


Point to Point Networks

Consists of Many Connections Between Pairs of SystemsPackets Travel To Destination Across Several Systems

Multiple Routes May ExistSpecial Routing Mechanisms Required


Local Area Networks

Privately Owned NetworksWithin Buildings or CampusesWidely Used To Connect PCs to Departmental or Campus ServersBroadcast Technology Typical

Topology: Bus or Ring


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Bus Topology

BUS

PC1 PC2 PC3 PCn


Bus Topology

At Any Instant, Any One Machine TransmitsTransmission Control in Ethernet (IEEE 802.3) is Decentralized

If Packets Collide, Each Machine Re-Transmits After Random TimeTypically Works at 10 or 100 Mbps


Ring Topology

PC1

PC2

PC3

PCn Token


Ring Topology

Packets Move around a RingTransmission Control Achieved Through Special MechanismIBM Token Ring (IEEE 802.5)

A Token is Passed Along RingToken Holder TransmitsOperates at 4 and 16 Mbps


Inter-Network

Multiple Networks Connected With Each OtherA Router Used To Forward Packets From One Node on one Network, Meant for a Node on Another NetworkRouter is Essentially a Packet Switching Node

Minimum One per LAN


Wide Area Networks

Router

Router

Router

Mumbai

Nagpur

Pune


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Wide Area Networks

Inter-Network of LANs at Many Locations Through RoutersRouters Connected Through Point to Point Connections

Typically Through Leased or Dial-up Lines of PSTN / PSDN


The Layered Model

Network Software has to Perform a Number of Functions at a NodeLayering Permits Isolation of Functions

Each Layer Implements Some Services Through its Own Protocol SuiteService Can be Connection Oriented or Connectionless


The Layered Model

A Specific Layer at One End Talks to The Corresponding Layer at The Other EndWithin a Node, Interacts With other layers Above & BelowTwo Important Reference Models

ISO (OSI) and TCP


Open System Interconnect (OSI Model)

Seven Layer ModelApplicationPresentation SessionTransportNetworkData LinkPhysical


The ISO-OSI Reference Model

Physical medium

Transport

Network

Data-Link

Session

Presentation

Application

Transport

Network

Data-Link

Session

Presentation

Application


Physical Layer

Transmission of Raw BitsRecognition of 0 and 1Bit Rates Decided at This Layer

Media, Mechanical/Electrical Issues Typical Media is Copper

Twisted Pair, Coaxial Cable

Optical FiberVery Large Bandwidths (Gbps)Low Attenuation (30Km)


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Data Link Layer

Main TaskTake The Raw Transmission Reception Facility and Ensure Error-Free CommunicationSend Data Frames, Receive & Process Acknowledge FramesControl Access To Shared Channel

As in Broadcast Mechanisms


Network Layer

Control The Operation of Routing of packets Across Networks. Address Resolution

Through Static TablesThrough Dynamic Tables

Handle Network CongestionUsage Accounting


Transport Layer

Take The Message From Higher Layer And Convert Into Smaller Units (Packets). Reassemble in The Right SequenceEstablish Distinct Network Service for Each Transport ConnectionTrue End-to-End Layer


Session And Presentation Layers

Establishing Sessions, to provide Dialog Services, SynchronizationResolve Common Presentation Issues

Text Coding ASCII, EBCDIC


Application Layer

Several Standards For Application Level Services

Virtual TerminalsE-MailFile TransferDirectory Look-up


TCP/IP Reference Model

Developed in ARPANETAgency of DoD, USA1969, Four MainframesEvolved into the INTERNET

Defined by Cerf & Kahn in 1974ISO Model is Academically Neat

ButTCP/IP is the De Facto Standard


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TCP-IP Reference Model

Physical medium

TCP

IP

Data-Link

FTP Application layer

Transport Layer

Network Layer

HTTP TELNET


Internet (Network) Layer

Connection less Packet Switched LayerPacket Formats Defined

Internet Packet (IP)Max Length 65535 Bytes

Usually ~ 1500 Bytes


Network Layer

Control The Operation of Routing of packets Across NetworksHandle Network CongestionUsage Accounting


IP Addresses (32 Bit)

Class ABegin with 07 bit network address(NA), 24 bit host address(HA)

Class BBegin with 1014 bit network address, 16 bit host address

0

10

NA HA


IP Addresses

Class CBegin with 11021 bit network address, 8 bit host address

Class DBegin with 1110Used for multicast addresses

Class E (11110) For Future Use

1110

110


IP Addresses

Written in Decimal Notation191.48.144.16

Special Addresses0.0.0.0 (This Host)255.255.255.255 All Hosts 127. (Anything) is a Loop BackHost Addresses Could Be Divided

Subnet + Host


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The IP Datagram Header

OPTIONS

DESTINATION ADDRESS

SOURCE ADDRESS

HEADER CHECKSUMPROTOCOLTIME TO LIVE

FRAGMENT OFFSETDF

MFIDENTIFICATION

TOTAL LENGTHTYPE OF SERVICE

HEADER LENGTH

VERSION


Transport Layer (TCP, UDP)

Transmission Control ProtocolEstablishes a Reliable ConnectionEnsures Error Free Delivery

User Datagram ProtocolConnectionless ProtocolUsed Heavily For

One-Shot Request Reply Queries

Transmission of Speech, VideoError Prone But Less Delay


Transport Layer

TCPTransmission Control ProtocolReliable End to End Byte StreamTakes Data Streams And Breaks These Into (IP) Packets < 64K ( Normal:1500 B)

Service ModelEnd Points Called Sockets Are CreatedEach Socket Number (Address)

Has IP Address of Host + A 16 bit PORT Number


TCP

Connections Identified By Pair of Sockets(Socket1, Socket2)

Ports < 256 Used For Special ServicesFTP : 21Telnet : 23

Connections Are Full DuplexExchanges Data In Segments

Header (20 Bytes + Options) + Data


TCP Header

OPTIONS (0 or More 32-bit Words)

TCP UNUSED FLAGS

Header WINDOW SIZELength

CHECKSUM URGENT POINTER

SOURCE PORT DESTINATION PORT

Data (Optional)

ACKNOWLEDGEMENT NUMBER

SEQUENCE NUMBER


UDP

SOURCE PORT DESTINATION PORT

UDP LENGTH UDP CHECKSUM

UDP Header Format

Sends & Receives Capsulized Raw IP Datagrams


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APPLICATION LAYER

Simplification of AddressesARPANET had a File Called hosts.txt Domain Name System (DNS)

Hierarchical System.in, .jp, .uk, or generic (.com, .org)

.co, .ac, .ernet, .iitb, .tifr, .pspl,

.it, .cse, .me, .ae, Example: quark.it.iitb.ac.in


DNS

Domain Names AreCase InsensitiveEither Absolute or Relative

Each Domain Controls Allocation of Names Under it

NCST in India

Name Length 63, Total 255 Chars


Domain Name Resolution

Networks understand IP AddressName Given to a RESOLVER Application

Sends it to a DNS ServerGets Back Resource Records


E-Mail

One of The Earliest ApplicationsElaborated in 1982 Arpanet Proposal

Two SubsystemsUser Agents (Client Side)Message Transfer Agents (Server Daemons)

Five Basic FunctionsComposition, Transfer, Reporting, Displaying, Disposition


E-Mail

Mailboxes, Mailing Lists, Message Format (To, From, cc, bcc )MIME

Multipurpose Internet Mail ExtensionsPermits Description of Content TypeText, Image, Audio, Video, Application


E-Mail Transfer and Delivery

SMTPSimple Mail Transfer ProtocolTCP Connection to Port 25Checks Existence of RecipientTransfers All Mail, Closes Connection

Delivery Protocols (To Fetch Mail)POP3 (Post Office Protocol)IMAP (Interactive Mail Access Protocol)Vacation Daemon

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