l6 mecse ncc

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