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IT 640 Modern Information Systems
1
IT 640 Modern Information Systems
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
IT640-Session 17, Networking BasicsDr. Deepak B Phatak 3
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
IT640-Session 17, Networking BasicsDr. Deepak B Phatak 4
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
IT640-Session 17, Networking BasicsDr. Deepak B Phatak 5
Scale of Networks
0.1 M Circuit Board1 M Computer System10 M Room100 M Building1 Km Campus10 Km City100 10000 Km Countries
LAN
WAN
IT640-Session 17, Networking BasicsDr. Deepak B Phatak 6
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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IT640-Session 17, Networking BasicsDr. Deepak B Phatak 7
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
IT640-Session 17, Networking BasicsDr. Deepak B Phatak 8
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,
IT640-Session 17, Networking BasicsDr. Deepak B Phatak 9
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
IT640-Session 17, Networking BasicsDr. Deepak B Phatak 10
Broadcast Networks
Packets Can be Addressed to ALL Systems
True Broadcast
Or Can Be Addressed To a Subset of Systems
Multicast
IT640-Session 17, Networking BasicsDr. Deepak B Phatak 11
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
IT640-Session 17, Networking BasicsDr. Deepak B Phatak 12
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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IT640-Session 17, Networking BasicsDr. Deepak B Phatak 13
Bus Topology
BUS
PC1 PC2 PC3 PCn
IT640-Session 17, Networking BasicsDr. Deepak B Phatak 14
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
IT640-Session 17, Networking BasicsDr. Deepak B Phatak 15
Ring Topology
PC1
PC2
PC3
PCn Token
IT640-Session 17, Networking BasicsDr. Deepak B Phatak 16
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
IT640-Session 17, Networking BasicsDr. Deepak B Phatak 17
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
IT640-Session 17, Networking BasicsDr. Deepak B Phatak 18
Wide Area Networks
Router
Router
Router
Mumbai
Nagpur
Pune
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IT640-Session 17, Networking BasicsDr. Deepak B Phatak 19
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
IT640-Session 17, Networking BasicsDr. Deepak B Phatak 20
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
IT640-Session 17, Networking BasicsDr. Deepak B Phatak 21
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
IT640-Session 17, Networking BasicsDr. Deepak B Phatak 22
Open System Interconnect (OSI Model)
Seven Layer ModelApplicationPresentation SessionTransportNetworkData LinkPhysical
IT640-Session 17, Networking BasicsDr. Deepak B Phatak 23
The ISO-OSI Reference Model
Physical medium
Transport
Network
Data-Link
Session
Presentation
Application
Transport
Network
Data-Link
Session
Presentation
Application
IT640-Session 17, Networking BasicsDr. Deepak B Phatak 24
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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IT640-Session 17, Networking BasicsDr. Deepak B Phatak 25
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
IT640-Session 17, Networking BasicsDr. Deepak B Phatak 26
Network Layer
Control The Operation of Routing of packets Across Networks. Address Resolution
Through Static TablesThrough Dynamic Tables
Handle Network CongestionUsage Accounting
IT640-Session 17, Networking BasicsDr. Deepak B Phatak 27
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
IT640-Session 17, Networking BasicsDr. Deepak B Phatak 28
Session And Presentation Layers
Establishing Sessions, to provide Dialog Services, SynchronizationResolve Common Presentation Issues
Text Coding ASCII, EBCDIC
IT640-Session 17, Networking BasicsDr. Deepak B Phatak 29
Application Layer
Several Standards For Application Level Services
Virtual TerminalsE-MailFile TransferDirectory Look-up
IT640-Session 17, Networking BasicsDr. Deepak B Phatak 30
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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IT640-Session 17, Networking BasicsDr. Deepak B Phatak 31
TCP-IP Reference Model
Physical medium
TCP
IP
Data-Link
FTP Application layer
Transport Layer
Network Layer
HTTP TELNET
IT640-Session 17, Networking BasicsDr. Deepak B Phatak 32
Internet (Network) Layer
Connection less Packet Switched LayerPacket Formats Defined
Internet Packet (IP)Max Length 65535 Bytes
Usually ~ 1500 Bytes
IT640-Session 17, Networking BasicsDr. Deepak B Phatak 33
Network Layer
Control The Operation of Routing of packets Across NetworksHandle Network CongestionUsage Accounting
IT640-Session 17, Networking BasicsDr. Deepak B Phatak 34
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
IT640-Session 17, Networking BasicsDr. Deepak B Phatak 35
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
IT640-Session 17, Networking BasicsDr. Deepak B Phatak 36
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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IT640-Session 17, Networking BasicsDr. Deepak B Phatak 37
The IP Datagram Header
OPTIONS
DESTINATION ADDRESS
SOURCE ADDRESS
HEADER CHECKSUMPROTOCOLTIME TO LIVE
FRAGMENT OFFSETDF
MFIDENTIFICATION
TOTAL LENGTHTYPE OF SERVICE
HEADER LENGTH
VERSION
IT640-Session 17, Networking BasicsDr. Deepak B Phatak 38
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
IT640-Session 17, Networking BasicsDr. Deepak B Phatak 39
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
IT640-Session 17, Networking BasicsDr. Deepak B Phatak 40
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
IT640-Session 17, Networking BasicsDr. Deepak B Phatak 41
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
IT640-Session 17, Networking BasicsDr. Deepak B Phatak 42
UDP
SOURCE PORT DESTINATION PORT
UDP LENGTH UDP CHECKSUM
UDP Header Format
Sends & Receives Capsulized Raw IP Datagrams
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IT640-Session 17, Networking BasicsDr. Deepak B Phatak 43
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
IT640-Session 17, Networking BasicsDr. Deepak B Phatak 44
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
IT640-Session 17, Networking BasicsDr. Deepak B Phatak 45
Domain Name Resolution
Networks understand IP AddressName Given to a RESOLVER Application
Sends it to a DNS ServerGets Back Resource Records
IT640-Session 17, Networking BasicsDr. Deepak B Phatak 46
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
IT640-Session 17, Networking BasicsDr. Deepak B Phatak 47
Mailboxes, Mailing Lists, Message Format (To, From, cc, bcc )MIME
Multipurpose Internet Mail ExtensionsPermits Description of Content TypeText, Image, Audio, Video, Application
IT640-Session 17, Networking BasicsDr. Deepak B Phatak 48
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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