Iso osimodel-090714010225-phpapp01

a.k.a. ISO OSI Reference Modela.k.a. OSI Model

1Krishna Kumar Bohra (KKB), MCA LMCST

www.selectall.wordpress.com

Avoidable duplication of equipment resources

Inability to communicate efficiently

To breaks network communication into smaller, simpler parts that are easy to develop

To facilitates standardization of network components to allow multiple – vendor development and support

To allow different types of network hardware and software to communicate with each other



ISO International Standard Organization

Established in 1947

Multinational body dedicated to worldwide agreement

Standard of international level

Covers all aspects of network communications

It is Open System Interconnection MODEL

Allow two different Machines to connect without change in hardware and software

It is model for understanding and designing a network architecture



Designed for communication across all types of computer system

Layered framework

7 separate but related layer

Each defines segment of process of moving information across network

Developers / Designers distilled the process of transmitting data to its most fundamental element

Related networking functions and its functionality are collected and discrete group ; became layer



Message from Device A to Device B

Travels several intermediate Nodes

These intermediate nodes involve only the first 3 layer

Please Do Not Touch Steve’s Pet Alligator



Data of L7 layer passed to layer 6

Data of L6 layer passed to layer



1 Peer to Peer Process

1. Sending bit stream form Machine A to Machine B

Layer 2 provides services to Layer 3 (talking about Single Machine)

Layer x provides services to Layer x (talking about In Between Machine)

Communication between them governed by agreed upon series of rules - “Protocol”

The process on each machine that communicates at given layer – “Peer to Peer Process”

Only Physical layer (direct communication)

2. Data from Higher to move down

3. Sending machine adds its own info part to message

4. Added info are called ‘Header’(beginning of message)

(Layers added Header 6,5,4,3,2) 7

Krishna Kumar Bohra (KKB), MCA LMCSTwww.selectall.wordpress.com

5. Added info are called ‘Trailer’(end of message)

(Layers added Trailer 2)

Every layer transform message for next layer

At receiving end the message is unwrapped (It is for every layer)

Interfaces between layers

All receiving and sending of information and network information (between layers) only possible by interface ; between pairs of Layers.

It defines what information, services a layer must provide to layer above it; process modulation.



Organization of layers

Three subgroups

1 Layer (1,2,3) [Network Support Layer] Deals with physical aspect of data from 1 device to other device

a. Electric Specification b. Physical Connection

c. Physical Address d. Transport timing

2 Layer (5,6,7) [User Support Layer] Interoperability among unread software system

3 Layer (4)End to End reliability of data transmission (Layer4)

Reliable transmission of link (Layer 3)

The process of putting Header and Trailer goes on Layer by Layer (except Layer 7 and Layer 1), Layer 2 both have Header and Trailer.



Software

Software +

Hardware

Hardware

N/W support

layer

User support

layer

Link between

Physical Layer > Changed info Electromagnetic signal > Physical Link > L1 > (transformed info into bits > than Layer by Layer Corresponding Header and Trailer removed. 10


•Physical characteristics of interfaces and medium.

•Representation of bits.•Physical topology. •Line configuration. •Data rate. •Synchronization of bits. •Transmission mode.

•Framing. •Physical addressing. •Flow control. •Error control. •Access control.



•Logical addressing. •Routing.

•Service-point addressing. •Segmentation and reassembly.• Connection control. •Flow control. •Error control.



•Dialog control. •Synchronization.

•Translation. •Encryption. •Compression.



•Network virtual terminal. •File transfer, access, and management.• Mail services. •Directory services.



1. The International Standards Organization created a model called the Open Systems InterconnectionOpen Systems Interconnection,

which allows diverse systems to communicate.

2. The seven-layer OSI model provides guidelines for the development of universally compatible universally compatible

networking protocols. networking protocols.

3. The physical layer coordinates the functions required to transmit a bit stream over a physical medium.

4. The data link layer is responsible for delivering data units from one station to the next without errors.

5. The network layer is responsible for the source-to-destination delivery of a packet across multiple

network links.

6. The transport layer is responsible for the process-to-process delivery of the entire message.

7. The session layer establishes, maintains, and synchronizes the interactions between communicating

devices.

8. The presentation layer ensures interoperability between communicating devices through

transformation of data into a mutually agreed upon format. 15


1. Data Communications and Networking - Behrouz A. Forouzan

2. OSI model - Wikipedia, the free encyclopedia



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