ATM With Vikas Kurdia

8/2/2019 ATM With Vikas Kurdia

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Vikas Kurdia

Asst. ProfessorHead of Department, MCA

I.T.M. College, Bhilwara

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Design Goals Need for transmission system to optimize use of high

data rate transmission media.

Must interface with existing system without requiringtheir replacement.

Inexpensive.

Must able to work with existing PSTN.

Must be connection oriented. To as many function to hardware and eliminate as

many software functions for speed.

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Asynchronous TDMATM is cell relay protocol.

Uses 53 byte cell as basic unit of data exchange.

It uses ATDM for data transfer. This means no particulartime slot is reserved and cells are transmitted as and when they

arrive.

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Architecture

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Virtual Connections Transmission Path : Transmission Path is the physical

connection between an endpoint and a switch or between two

switches.

Virtual Path : Virtual Path provides a connection between two

switches.

Virtual Circuit : Virtual Circuit provides a connection

between two endpoints.

VP is identified by VPI. VC is identified by VCI.

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Cont

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ATM Cell A cell is a small, fixed sized block of information used in

data exchange (53 bytes).

In cell networks, as frames of different sizes and formatsapproach, they are split into multiple small data units ofequal length and are loaded into cells.

These cells are then multiplexed with other cells androuted through cell network.

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UNI Cell

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NNI Cell

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ATM Layers

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ATM Adaption Layer

ATM Layer

Phycial Layer


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Physical Layer Deals with physical characteristic of medium.

ATM design is used with SONET.

Also used to define boundary of cell. Next cell is just 53bytes ahead of current cell.

Cell Rate Decoupling- When no user data is available,dummy cells are inserted to fill time slot.

Encoding and Transmission- Encoding orrepresentation of bits depend on physical media e.g.different encoding for copper wire than for fiber cable.

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ATM Layer Provides routing, switching, traffic management,

multiplexing services.

Accept 48 byte payload from AAL and transform themto 53 byte cell by adding additional 5 byte header.

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Application Adaption Layer (AAL)ATM must accept frames as well as raw of bits to form

a cell.

Two Sub Layers for AAL. Segmentation and Assembly (SAR) for

segmentation at source and reassembly at destination.

Convergence Sub layer (CS) to guarantee integrity of

data before preparation.

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Thank You

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ATM With Vikas Kurdia

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