Network Protocol Models and Architecture Networks and Protocols Prepared by: TGK First Prepared on: Last Modified on: Quality checked by: Copyright 2009

Network Protocol Models and Architecture

Networks and Protocols

Prepared by: TGK First Prepared on: Last Modified on:

Quality checked by: Copyright 2009 Asia Pacific Institute of Information Technology



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Topic & Structure of the lesson

Network Standards and ProtocolsThe ISO-OSI ModelComparing TCP/IP Architecture and the OSI Model



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Learning Outcomes

At the end of this module, YOU should be able to:

• Explain the importance of Network standards and Protocols

• Explain the purpose of the OSI standards model and its contribution to network communications

• Explain the purpose of the TCP/IP architecture and the implementation for network communications

• Explain the differences between the OSI model and TCP/IP architecture



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Key Terms you must be able to use

If you have mastered this topic, you should be able to use the following terms correctly in your assignments and exams:

• Reference model• Protocol suite



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Main Teaching Points

• OSI Model• Layering• OPEN communications• Communication process• TCP/IP architecture • Protocols



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Network Standards and Protocols

• Standards are important, especially to an area such as

interconnectivity

• In data communications, the International Organization

for Standards (ISO) has a proposed standard called the

Open System Interconnect (OSI) Model

• Complexity of communication system has increased

tremendously however, all networks share common

functions

• ISO has identified and stratified these functions in the

Reference Model for Open Systems Interconnection



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• The Open Systems Interconnect

• OPEN - means any two systems conforming to the

reference model and standards can communicate.

i.e. different networks can interconnect

• The Model defines a “ Communications

Architecture” using a seven (7) layer model which

provides a blueprint for building a computer network

• Characteristics of the ‘Layer’ ConceptCharacteristics of the ‘Layer’ Concept

• Peer Layer Concept

• Entities on each layer communicate with their

equivalent on the other side

The ISO-OSI Model



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• Service Concept

• Each layer uses the ‘service’ provided by the next

lower layer

• Each layer provides ‘service’ to the next higher

layer

• Independence Concept

• Each layer is independent

• It carries out its own task independently of other

layers

• Implementation of each layer is independent within

the standards

The ISO-OSI Model



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• A layer does not care or need to know how the next

layer does its job

• The OSI layers

The ISO-OSI Model

Application

Presentation

Session

Transport

Network

Data link

Physical



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The ISO-OSI Model

• OSI communication process



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The ISO-OSI Model

• OSI layers’ headers and trailer



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The ISO-OSI Model

• OSI Application layer

• Includes functions defined by user

• Sometimes application programs must communicate

with each other across the network

• Content & Format of data exchanged dictated by

needs of organizationApplication

Presentation

Session

Transport

Network

Data link

Physical

Data Date=mm/dd/yy



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The ISO-OSI Model

• OSI Presentation layer

• Receiving Application

• Has a different set of formatting rules

• Uses a different date format

• Presentation layer is responsible for translating from

one format to another

• This can be done by changing:

• To a standard transmission format, which is

converted by its peer layer / Directly to a format

expected by receiving application



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• The Presentation layer operation

The ISO-OSI Model

Application

Presentation

Session

Transport

Network

Data link

Physical

Data (compressed) Date Date=dd/mm/yy



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The ISO-OSI Model

• OSI Session layer

• Establishes connection between applications

• Try to re-establish connection if a failure occurs

• Enforces rules for carrying on a dialogue between

applications

• Rules Specify:

• Order in which application is allowed to

communicate

• Pacing of information transfer so as not to

overload recipient (flow control)

• How to bring session to an orderly conclusion



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• Direction of information flow

• The Session layer operation

The ISO-OSI Model

Application

Presentation

Session

Transport

Network

Data link

Physical

ID Length Data (compressed)

connection established, Half-duplex, etc



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The ISO-OSI Model

• OSI Transport layer

• First layer concerned with world external to its

processor

• Generates address of end user (the SENDER of data)

• Ensures no packets have been lost in transmission

and no duplicate packets occur

• OSI Network layer

• Routes packets - is concerned with the establishing

connections across network

• Collects billing and accounting information



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• Upon receiving message from Transport Layer the

Network layer:

Logs event to the accounting system

Prepares message for transmission to next node

on path to destination

Looks up address of next node in Routing Table

and appends address

If message is long, divides it into transmission

units and appends a sequence number to each unit

Sends each unit

The ISO-OSI Model



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The ISO-OSI Model

• The Network layer operation

Application

Presentation

Session

Transport

Network

Data link

Physical address of next network node

Routing TSAP Chksum ID Length Data Seq no Header



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• OSI Data link layer

• Establishes and controls the physical path to next

node. Tries to make the physical link reliable, in

particular includes:

• Error detection and correction

• Defining beginning and end of data field

• Resolving competing requests for use of shared

communications link

• OSI Physical layer

• Specifies electrical connections between

transmission medium and computer system such as:

The ISO-OSI Model



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• Number of wires use to carry signals

• Size and shape of Connectors

• Speed of data transmission (BPS)

• Comparing the IEEE standards with the OSI Physical layer:

The ISO-OSI Model

OSIPhysical(Layer 1)

802.310Base-T

802.310Base-T

802.3100Base-T

802.3100Base-T

802.3Other

PhysicalLayer

802.3Other

PhysicalLayer

802.5Physical

Layer4 Mbps

802.5Physical

Layer4 Mbps

802.5Physical

Layer16 Mbps

802.5Physical

Layer16 Mbps

OtherPhysical

Layer

OtherPhysical

Layer

Multiple Physical Layer StandardsAdded as technology maturesAdded if standards creators cannot decide on one

Multiple Physical Layer StandardsAdded as technology maturesAdded if standards creators cannot decide on one



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Comparing TCP/IP and OSI model



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• TCP/IP Chronology

• Late 1960s: Requirement specified by US DoD

• Early 1970s: ARPAnet implemented

• Late 1970s: Widespread use in US universities

• Mid 1980s: Commercial use increasing

• Early 1990s: HTTP became largest proportion of

Internet traffic

• Purpose of TCP/IP

• Provides a common communication standard for

network devices



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- `mainframes, PCs, workstations, printers, remote `mainframes, PCs, workstations, printers, remote

devices, telephones, televisions?devices, telephones, televisions? Provides a framework for interconnection and

interoperation regardless of platform or physical network medium

Where is TCP/IP used

Basic applications:• Telnet (23)

– remote terminal session




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• FTP (21/20)– File transfer

• SMTP/POP (25/110)– Electronic mail

• NFS (Uses RPC)– Network File System

• More advanced applications:– HTTP (WWW port 80)

Overview• The term TCP/IP is used generically to refer to

anything and everything related to the specific network and transport layer protocols:




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TCP UDP IP ARP TELNET FTP




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Quick Review Question

1. List the major disadvantages with the layered approach to protocols.

2. Discuss the need or lack of need for a network layer(OSI layer 3) in a broadcast network.



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Follow Up Assignment

Presentation on Layered Model Approach (OSI or TCP/IP)



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Summary of Main Teaching Points



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Q & A

Question and Answer Session



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Topic and Structure of next session

• Data Link and Flow Control

Overview of Data Link Control and Flow Control

MechanismsFlow Control TechniquesError Detection TechniquesError Control Techniques

Next Session

Documents

Network Protocol Models and Architecture Networks and Protocols Prepared by: TGK First Prepared on: Last Modified on: Quality checked by: Copyright 2009