asynchoronous transfer modes1

8/9/2019 Asynchoronous Transfer Modes1

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Definition

ATM standard

ATM network

ATM interfaces

ATM cell

ATM Adaptation layer(AAL)

to be contd...


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ATM Application

ATM Services Categories

ATM advatages

ATM advantages

ATM challenges

References


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Asynchronous Transfer Mode (ATM) is a

technology that has the potential of

revolutionizing data communications and

telecommunications.

ATM is a packet switching.


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Low-level network layer

Single transport mechanism

Streamlined protocol


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ITU-T I.361

Defines the ATM Layer functions.

ITU-T

I.363

Defines the ATM Adaptation Layer-

protocols.

ITU-T I.610

Defines the ATM Operation andMaintenance (OAM) functions


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1) User-to-NetworkInterface (UNI)

2) Network-to-NetworkInterface (NNI)

3) Inter-CarrierInterface (ICI)


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1. User-to-Network Interface (UNI)

Ex

ists between a single end user and a public ATM network.

2. Network-to-Network Interface (NNI)

Exists between switches in a single public ATM network.

3. Inter-Carrier Interface (ICI)

It is located between two public ATM networks


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Virtual channel:

Achannel that provides transportation of ATM cells

between two or more endpoints for information transfer.

Virtual paths:

It is a group of Virtual Channels that are carried on the

same physical facility and share the same Virtual Path

Identifier (VPI) value.


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Small size, may reduce queuing delay of highpriority cellsFixed size, more efficient switching

Diagram of the UNI ATM Cell Diagram of the NNI ATM Cell


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1) 5 bytes header:

(I) General flow control defined across the UNI

flow across the UNI

intended to control the traffic 4 bits must be set to 0's.(II) Virtual path control routing field for network an 8-bit field for the UNI and a 12-bit field

for the NNI, is used to identify virtual paths.


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yVirtual Channel Identifier (VCI)

16-bit field is used to identify a virtual channel

For idle cells, the VCI is set to all 0's.

yPayload Type Identifier (

PTI)

three bits of the PTI

Continue.Continue.


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yCell Loss Priority (CLP)

The 1-bit CLP field

used for explicit indication of the priority of the

cell

yHeader Error Control (HEC)

8-bit fieldIt capable of detecting all single-bit

errors and some multiple-bit errors.


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ATM ApplicationsATM Applications


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ATM Service CategoriesATM Service CategoriesReal-time services

Constant bit rate uncompressed audio/video info

Videoconferencing, TV, pay-per-view, VOD, etc.

Non-real-time services

Available bit rate bursty apps requiring reliable end-

to-end connection

e.g. LAN, router-to-router reliability


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ATM AdvantagesATM Advantages

Universality

Mixed traffic types, real-time and non-real-

timeScalability

LANs, WANs, WLANs

Efficient use of network resources Bandwidth

on demand concept

Simplified network infrastructure


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ATM challengesATM challengesIn-network mux/buffering can lead to cell

delay or loss

Many types of traffic

Large geographic distribution


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ReferencesReferences

y http://www.iec.org

y Amos E. Joel, Jr.,Asynchronous Transfer Mode

(IEEE Press, 1993)

y "Broadband ISDN and ATM". http://world-

class-programme.com


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THANK YOUTHANK YOU

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