N E T W O R K S

Introduction to ATM Meir Leshem

May 2009

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N E T W O R K SSeminar Contents

Introduction to ATM

Adaptation Layers

Traffic Management

ATM Signaling

OAM

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ATM Fundamental Concept

VoiceEnergy

Pause Pause Listening

Speaking Speaking

All communications are bursty

TimeTherefore, a high performance packet

switching network can carry allcommunications

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ATM Vision: The Ultimate Integrated Services Network

ATMNetwork

Voice

Data Video

Video

Video

Voice

Voice

Data

Data

ATM network moves (fixed length packets) with low delay and low delay variation at high speedsDevices at ends translate (e.g., segment and reassemble) between cells and original traffic

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N E T W O R K STDM

TDM - Time Division Multiplexing A circuit switching technology Each channel has a fixed Time Slot (basic unit 64 kbit/s)

( for example: 30 TDM channels on one E1 trunk) Suitable for Circuit Switching technology

A circuit is established between the talks for the entire

duration of the call Fixed bit rate for any service

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N E T W O R K SATM

ATM - Asynchronous Transfer Mode A fastfast packet switching technology (cell = small packet, 48 bytes) Statistical multiplexing of several connections on the same link ATM Switch routes the user data (cells) to the next switch

using the VP, VC in the cell header Connection oriented

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ATM Cell Structure(it all started with a single cell)

Header Payload

4 1 48 bytes

VCI

VCI

VPI

VPI

VCI PTI

HEC

CL

P

GFC

VPI - Virtual Path IdentifierVCI - Virtual Channel IdentifierGFC - Generic Flow Control

PTI - Payload Type IdentifierCLP - Cell Loss PriorityHEC - Header Error Check

NNI UNI

VCI

VCI

VPI

VPI

VCI PTI

HEC

CL

P

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N E T W O R K SATM Basic Features

Connection oriented mode

No control flow or error protection for connections

Limited functionality of cell header

Small and fixed payload size

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Combinations of reserved VPI, VCI and PTI values

A - 0 or 1 depending on the specific function, C - Transmitted as 0, may be changed to 1 by the network

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ATM Connection Identifiers

VC1

VC2VP1

VC1

VC2VP2

VC1

VC2VP1

VC1

VC2VP2

Link 1

VC1

VC2VP1

VC1

VC2VP2

VC1

VC2VP1

VC1

VC2VP2

A

BC

D

E

F

G

H

I

Network and SwitchesLink 1

Link 2 Link 2

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Examples of VP and VCI Operations

ATMSwitch

VPI=20VCI=33 VPI=2

VCI=14

VPI=8VCI=56

ATMSwitch

VPI=5VCI=13

VPI=9VCI=27

VPI=4VCI=10

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VP and VC Switching

VC1

VC2

VC1

VC2

VC4

VC3

VC1

VC2

VP Switch

VC Switch

VPI 4

VPI 11

VCI3

VCI2

VCI1

VCI4

VPI3’

VPI 5

VPI 3

VPI 2’

VPI 1’

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N E T W O R K SExamples of VP and VC Switching

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Reserved VCIs at a UNI

VPI=0

VCI=35

VCI=45

Example of two VC services on VPI=0Only VCIs 35 and 45 are used for user data

}Reserved VCIs:VCI=5 for signaling, VCI=16 for ILMIVCI=3 and VCI=4 for F4 OAM

VPI=20

ActiveVCIs

unknown

Example of VP serviceNetwork knows nothing of whichVCIs are used for user data

} Standard VCIs that come with a VPIVCI=3 and VCI=4 for F4 OAM

VCIs 0-15 reserved for ITU-TVCIs 16-31 reserved for ATM Forum

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V P L

Virtual Path and Channel Connections

VCL VCL VCL

ATM NE ATM NE

VCLsVCI = Virtual Channel IdentifierVCL = Virtual Channel LinkVCC = Virtual Channel Connection

VPI = Virtual Path IdentifierVPL = Virtual Path LinkVPC = Virtual Path Connection

V P L V P L V P L

VCCs ATM NE ATM NE

Virtual Channel Connections

Virtual Path Connections

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N E T W O R K SThe ATM Layered Model

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N E T W O R K SB-ISDN Reference Model

TC - Transmission Convergence SSCS - Service Specific Sub LayerPM - Physical Medium CPS - Common Part SublayerSAR - Segmentation And Reassembly

Convergence Layer

SAR LayerAAL

ATMCELL VPI/VCI translationCELL multiplex/demultiplexCELL HDR generation/extraction

CELL rate decoupling (idle cells)Cell delineationHDR HEC sequence (generation/recovery)

PMBIT TimingPhysical Medium

TC PhysicalLayer

SSCS

CPS

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B-ISCN/ATM Layer and Sublayer Model

Layer name Functions performed

Higher layers Higher layer functions

AAL

ATM

LAYER

MANAGEMENT

ConvergenceSublayer (CS)

SAR Sublayer

Service Specific Sub Layer (SSCS)

Common Part Sublayer (CPS)

Segmentation and Reassembly

Generic flow controlCall header generation/extractionCell VCI/VPI translationCell multiplexingCell rate decoupling (unassigned Cells)

PHYS ICAL

TransmissionConvergence (TC)Sublayer

Physical mediumDependent (PMD)

Cell rate decoupling (idle cells)Cell delineationTransmission frame adaptationTransmission frame generation/ recovery

Bit timingPhysical medium

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ATM Protocol Reference Model

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B-ISDN Protocol Reference Model

Signaling CO CLOther VBRServices

CBRServices

ATM

PHY

Convergence Sublayer (CS)

Segmentation and ReasssemblySublayer (SAR)

PlaneManagement

LayerManagement

Management Plane

AAL

ControlPlane

VBR Services

UserPlane

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ATM Application Program Interfaces

F4, F5OAM

Q.2931

Q.2130

Q.2120

AAL5 AAL2 AAL1

ATM

PHY

MIBs

Planemanagement

Layer management

Overallmanagement

data

ATMOAMdata

Signalingcontrol

AAL message modestream mode,ILMI access

AAL CBRmode

ATMcell

accessATMAPI

AAL CBR/VBRmode

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User plane higher-layer protocolsfor voice, video and WAN data

CircuitEmulation

Service(CES)

Voice &telephony

overATM

(VTOA)

Videoon

demand(VOD)

Framerelay

networkinterworking

Framerelay

serviceinterworking

ATMDXI and

FUNI

ATMaccess

toSMDS

AAL1 AAL2 AAL3/4AAL5

FR-SSCS

ATM layer

Physical layers

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ATM Protocol Support for Voice and Video

CircuitEmulation

Serviceaf-vtoa-0078

Voice &telephony

overATM

af-vtoa-0089

VoiceTrunking over

ATM using AAL2af-vtoa-113.000

AAL1I.363.1

AAL2I.363.2

AAL5I.363.5

I. 366.2

ATM layerI.361

Physical layersG.804, I.432, UNI 3.1, T1.646

ResidentialBroadband

(RBB)

Video onDemand(VOD)

Other principle standardsUNI Signaling : Q.2931, UNI 3.1, UNI 4.0 (af-sig-0061.000)Signaling AAL: Q.2110, Q2130Traffic Management: I.371, af-tm-0056.000OAM: I.610NE Management: GR-CORE-1248

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N E T W O R K SRelationship of User and Network Layers

User User

ULP ULP

AALAAL

ATM ATM

PhysicalPhysical PhysicalPhysical

ATM

PhysicalPhysical

ATM

PhysicalPhysical

ATM

PhysicalPhysical

UNI NNI NNI UNI

ATM Network

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Functional division of WAN ATM PDH

access system within ATM switch

SWITCHCORE

Addresstranslate

Policing& UPC

Trafficshaping

OAM

ATM

CELL

MUX

&

DEMUX

ATMcell

delin.+

HECgen.ITU

I.432

TXConv.ITU

G.804

OFF-THE-SHELFE1 FRAMERS

OFF-THE-SHELFT1 FRAMERS

OFF-THE-SHELFT3/E3 FRAMERS

SWITCHING ATM LAYER PMD LAYER

Dynamicswitching

Traffic handlingand signaling

Trafficdistribution

Mapping Transmission

Vendor specific:Shared memoryBus switchBanyan, input OR output buffered

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N E T W O R K SMultiservice ATM Multiplexer

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N E T W O R K SDirect Hec Mapping for E1

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State diagram for cell synchronization(“Direct HEC”)

SYNCPRE

SYNC

nconsecutive

incorrect HEC

mconsecutivecorrect HEC

Cell bycell

Incorrect HEC

Correct HEC

Bit by bit

HUNT

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Automatic HEC model for ATM switching equipment

No bit error - No action

Single bit error- Error correction

Noerror- No

action

Multiple bit error- Cell is deleted

Errordetected- Cell isdeleted

Correctionmode

Detectionmode

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ATM Multiplexing Function - the “Chopper”and the “Postman”

Data

VP1=0, VCI=51

H 48 B48 B48 B48 B

Voice

VP1=0, VCI=52

H 48 B48 B48 B48 B

Video

VP1=0, VCI=53

H 48 B48 B48 B48 B

PostmanChopper

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ATM Multiplexing FunctionCell Scheduling by a “Gatekeeper” at the UNI

DataVC1=51

VoiceVC1=52

VideoVC1=53

Gatekeeper

Lowest priority

Highest priority

Next highest priority

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Illustration of Virtual Channels SupportingMultimedia Application

H P H P H P H P H PVideo

H P H P H PVoice

H P H P H P H PData

Virtual Channel VPI=0, Vci=53 (Video)

Virtual Channel VPI=0, Vci=52 (Voice)

Virtual Channel VPI=0, Vci=51 (Data)

ATMMultiplexing

Function

Non real time variable bit rate (nrt-VBR)

Constant bit rate (CBR)

Real time variable bit rate (VBR)

User = Network Interface (UNI)

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N E T W O R K SIUB ATM

Active

VCs

Stand by

VCs

VP1

VC45

VC43

VC33

VC44

AAL5

AAL5

AAL5

AAL5

Q.2630

NBAP-Common

Mub-B

VC41 AAL0 Sync-B

NBAP-Dedicated

VC 39

VC38

VC36

VC32

VC34

VC37

AAL2

AAL5

AAL5

AAL5

AAL0

AAL5

User Plane

DCH, PCH, RACH, FACH

Q.2630

NBAP-Common

Mub-A

Synch-A

NBAP-Dedicated

N E T W O R K S

Thank You