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April 10, 2023 M.E. CSE-IT/NCC 1
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Lecture : 05 Sub: Net-Centric Computing
Unit 01 : OSI Model
Class : ME CSE(Info.Tech)
Date : 21/08/2007
Delivered By
Manik Dhore
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C I need no warrant for being,
and no word of sanction upon my being.
I am the warrant and the sanction
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What OSI Defines ?
How n/w devices contact each other?
Methods by which device knows when to transmit data and when not to
Methods to ensure that n/w transmission is received correctly and by the right recipient
How to ensure that network devices maintain a proper DTR of data flow ?
How bits are represented on the n/w media ?
How to sequence the layers with Connection / Connectionless?
How to organize network functions into seven layers ?
How to organize peer to peer mode ?
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Design Issues of Protocol Layers
Mechanism for identifying sender and receiver
I.e. Addressing
Rules for Data Transfer
Unidirectional ( Simplex )
Bi-directional ( Half and Full Duplex)
Methods for Error Control :
Error Detection
Error Correction
Queuing mechanism for Fast Sender and Slow Receiver
Methods to process arbitrarily long messages
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Algorithms for Route decisions
Multiplexing and demultiplexing for multiple connections
Centralized
Decentralized
Dynamic
Logical decompositions of complex network
Standard interfaces between n/w layers
Symmetry in functions
Standard communication network language
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Link approach
Connection Oriented
Connectionless
Connection Oriented Means
i. Acknowledgment
ii. Flow Control
iii. Error Control
Connectionless Means
i. No Acknowledgment
ii. No Flow Control
iii. No Error Control
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Happiness is that state of consciousness
which
proceeds from the achievement of one's values.
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OSI Model
7. Application
6. Presentation
5. Session
4. Transport
3. Network
2. Data Link
1. Physical
1. Application
2. Presentation
3. Session
4. Transport
5. Network
6. Data Link
7. Physical
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Application Layer
provides network services to application processes ( such as electronic mail, file transfer,terminal emulation )
Interface to TDI or Third Party
Gateways for different network file formats
Presentation Layer
Data representation
Format of data
Data structures
Ensure data is readable by receiving system
Negotiates data transfer syntax for application layer.
Resolves differences between format
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Session Layer Interhost communication
Establishes, manages and terminates sessions between applications
Controlling dialogues between applications in the end systems
Dialogue discipline, Grouping and Recovery
Ex.
Logging Process
Remote Terminal Access in half duplex
Transaction Processing checkpoints, backups
Token management in half duplex mode
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Transport Layer
End-to-end connection reliability
Concerned with data transports issues between hosts
Data transport reliability
Establishes, maintains, terminates virtual circuits. / multiple network connections
Fault detection and recovery / Error Control
Flow control management
Error free delivery of data
Fragmentation and reassembly ( into packets as per network layer specification )
Decision about service type
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Network Layer Addresses Resolution
Controlling Subnet
Providing best path
Provides connectivity and path selection between two end systems
Domain of routing / Route decision and selection
Congestion Control Mgt.
Accounting
Large Packet Mgt.
Heterogeneous n/w problem mgt
Determines Quality of Service
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Data Link Layer
Access to media
Provides reliable transfer of data across media.
Physical addressing, network topology, error notification,
flow control.
Framing : Break packets into frames according to the
specifications of physical layer standard I.e encapsulation
and de-capsulation of data
Error Control and Recovery for physical Channel
Link Management
Collision Avoidance and collision content resolution
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Physical Layer
Binary transmission
Wires / Cables
Connectors
Voltages
Data rates
Initial Connection
Turn down connection
Pin assignments
Concentrators / Hubs/ Repeaters
Wiring Schemes
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Don't fall before you're pushed
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Needs of DOD Ability to connect multiple networks ie homogeneous as well as heterogeneous ( Internetworking )
Network must be able to survive the loss of subnet hardware
Multiple transmission lines
Connectionless services
Real Time Speech Transmission
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TCP / IP Model
4. Application
3. Host to Host
2. Internet
1. Network Access Layer
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OSI TCP/IPISO in 1977 and adopted in DoD in 1974 by Vint Cerf &
1983 Robert Kahn
Developed by dedicated team Developed by open process
Copyrighted and carry a Free
Purchase fees
Proprietary Non-proprietary
Intended to be a Inter- Never indented to be
National standard
Designed with layers Not designed with layers
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OSI TCP/IPDevised first and protocols Protocol came first and then
Invented latter model
Seven Layers Four Layers
T-Layer is connection Both- less and oriented
N/w –Layer is both N/w layer is connection
oriented
Gives interface,service No clear distinction
And protocols
Generalized Not Generalized
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OSI TCP/IPStrongly describes protocol Poorly describes protocol
stack stack
Separate Layers Can view in layers
Not Popular Very Popular
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TCP/IP Network Components
FTP, Telnet, POP TFTP, DNS, BOOTP
SMTP,FINGER,HTTP SNMP,NFS
TCP UDP
ICMP ARP
RARP IP OSPF
RIP X.25 Packet Level
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TCP/IP Model
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TCP Port Numbers
32-bit Sequence Number
32-bit Ack Number
Flags : URG, ACK, PSH, RST, SYN, FIN
Urgent Pointers
Connection Oriented
Reliable
Full Duplex
ID Assignment to multiple virtual circuits
Works with IP
Maintain the sessions
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TCP Header
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Provides a lossy connection (data may vanish).
Does not guarantee packets are delivered in order.
Useful for real time applications.
UDP applications can implement their own packet loss checking but it is best to use TCP for this.
UDP
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UDP Frame Format
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IP Connectionless
Unreliable
Uses only packet switching
TOS : Priority, Delay, Throughput, Reliability
Satellites and Leased Lines
Flags : DF and MF
Don’t and More
TTL : Number of hops ( If not delivered return to)
Protocol : Application Layer
Padding
Offset of fragment
Packet Size : 64 K
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IP header
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Internet Control Message Protocol packets are used for various control purposes. Here are some common ones:
Time exceeded: TTL hit 0.
Echo request: Can you hear me out there?
Echo reply: Yes I can hear you.
Source Quench: Stop sending so much data.
Timestamp request/reply (as echo but with times).
ICMP
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Netware IPX/SPX Network Component
SAP NLSP File Server
NCP RIP
SPX
IPX
LSL MLID ODI
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Netware Suite Proprietary Protocol Suite
Developed by : Xerox Network System
IPX : Internetwork Packet Exchange
SPX : Sequenced Packet Exchange
Modular in nature
Architecture is server – centric
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IPX
Connectionless datagram service
Broadcast mechanism for error notification and time synchronization
Dynamic route selection
Transport Control : Max 16 bridges using counter
Packet Type : 0x8035
Destination Address : 12 bytes
Network Number – 4 bytes
Node Address -- 6 bytes
Socket Number -- 2 bytes
Data in packets : 546 bytes
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Microsoft NetBIOS/ NetBEUI Network Components
File I/O Named Pipes Redirector Server Mail slots
NetBIOS Sockets SMB
NetBEUI
NDIS
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NETBIOS (Network Basic Input Output System)
•NetBios is also a session/transport layer protocol
• Starting and stopping sessions.
• Name registration
• Session layer data transfer(reliable)
• Datagram data transfer(unreliable)
• Protocol driver and network adapter management functions
1) nbstat -n Lists all registered NetBios names.2) nbstat -c Shows the NetBios cache.3) nbstat -R Reloads the NetBios name cache from the lmhosts file.
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NetBEUINetBIOS Extended User Interface
Basically Transport Layer Protocol
Performance in LAN environment is very good
Requires small amount of configuration
Requires small amount of resources (Memory)
Can handle maximum 254 sessions
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Books
Lecture 01/02/03/04/06 :
1. Tananbaum :
Computer Networks PHI De Facto Standard
2. High Speed Networks and Internet PHI
3. ISDN Broadband ISDN with Frame Relay and ATM Pearson
4. Data Communication and Networking by
Forouzan Edition 2 and 3 , TMH
Short questions and answers
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5. Data and Computer Communication by William Stalling 4th and 6th edition PHI
6. Network Communication Technology by Elahi
Thomson Pub, Short questions and answers
7. An Introduction to Computer Networking by
Mansfield and Antonakos, Pearson Education
8. Building Practical Ethernet Networks BPB
9. Internetworking By Miller
10. Networking Devices by Miller
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11. Telecommunications Network Design Algorithms by Kershanbaum A. TMH
12. Comer : Computer Networks Vol.1, 2 and 3
13. TCP/IP Illustrated By Steven Vol. 1,2 and 3
14. IP Telephony by Douskails B. Pearson
And N- number of cited web references
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1. Write a Client – Server program for ping by building your own packets. ( Individual) ( c-Language) ( Time 1 week)
2. Design a sniffer for windows by using packet driver and calculate the bandwidth utilization ( protocolwise) of your network
3. Design a configurable firewall for windows(VB)
4. Develop a simulation software to simulate working of Frame Relay
5. Develop a simulation software to simulate working of ATM
6. Develop a simulation software to simulate working of ISDN
7. Develop a package for the following compression methods
I) Run length Encoding ii) Facsimile Compression
iii) String Matching iv) Wavelet Compression
v) JPEG
Note : Assignment 2-7 are group assignment
Team Size is 5 ( According to roll number)
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Practical Guidelines
Assignment No.1 :
•TCP/IP Illustrated by Steven Vol.1,2 and 3
•Simple Client Server
•Use of RAW Sockets
•Building of ICMP Packets
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Assignment No.2 :
Sniffer ( Study Ethereal First)
Download Packet Driver
Install it
Use the driver services
Map the data
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Assignment No.3 :
Firewall
Download Packet Driver
Install it
Use the driver services
Configure the ports
Map the data
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Assignment No.4,5,6 :
Frame Relay
Study Frame Use Operations
Use Java , JavaScript, JSP
Simulate Protocol Operations
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Assignment No.7 :
Compression
Plenty books are available