ATM Protocol and Signalling by ziafat ali

1 © NOKIA CTXX 5882_1.0en.PPT/ 17.05.2001 / Kamolwun Dankhonsakul

ATM Protocols and SignallingATM Protocols and Signalling


Objectives

After completing this module, the student should be able to:

• Name the three planes in ATM protocol reference model and their functions.

• List the three main protocol layers of ATM and describe their functions.

• Describe the main functions of AAL type 2 signalling protocol.

• List different uses for an ATM network. Describe in block diagrams how such a network can be structured in 3G.


Contents

• ATM protocol• Physical layer, ATM layer, ATM adaptation layer

• Switching in ATM network• Switching in ATM layer• AAL type 2 switching

• ATM signalling• Signalling protocol layers• AAL type 2 signalling

• ATM as a transport network in 3G• ATM interface• General protocol model for UTRAN terrestrial

interface


ATM Protocol Reference Model

I.321 Reference Model

Physical Layer

ATM Layer

ATM Adaptation Layer

User Plane Control Plane

Plane Management

Layer Management

Management Plane

Higher LayersHigher Layers

Performs call and connection control functions, e.g. signalling procedures

For user information transfer and associated controls(e.g. flow control, error control, etc.)

Performs management functions related to the system as a whole

Performs management functions relating to layer's resources and parameters (e.g. OAM information flows)


Protocol Reference Model

ATM Layer

Physical Layer

ATM Layer


Physical Medium (PM)

Transmission Convergence (TC)

Segmentation and Reassembly (SAR)

Convergence Sublayer (CS)


ATM cell

• Header contains routing and error control information

• Payload carries the actual user information, either voice, data, or video

Header5 bytes

Payload48 bytes

53 bytes


ATM layer functions

Convergence Sublayer (CS)

PayloadPayload HeaderHeader

48 bytes5 bytes

User data

AAL

Segmentation and Reassembly Sublayer (SAR)

ATM Layer

Transmission Convergence (TC)

48 bytes

Physical Medium Dependent(PMD)

SD

H O

/H

PayloadHeader

Scramble frame and adapts the signals to the optical or electrical transmission medium

STM-1 Frame

Physical Layer


ATM protocol structure

ATM Adaptation Layer(AAL)

ATM Layer

Physical Layer

ATM Layer

Physical Layer

Physical medium Physical medium

ATM End System (BS) ATM End System (RNC)

ATM Switch

ATM network

ATM Adaptation Layer(AAL)

ATM Layer

Physical Layer

ATM Layer

Physical Layer

Physical medium

ATM Switch


ATM adaptation layer and supported traffic

ATM layerPhysical layer

Bit rate

Timing required between source & dest.

Connection mode

Example of traffic types

AAL

Constant Variable

Synchronised Not synchronised

Connection orientedor connectionlessConnection oriented

Voice, circuit emulat

ion

Video, voice with

silence remove

d

Data, SMDS

Data, Fram

e Relay,

IP

AAL1 AAL3/4AAL2 AAL5

SMDS : Switched Multimegabit Data Service


ATM Adaptation Layer 2 (AAL2)

• Human speech• contains significant periods of silence• requires low bandwidth for transmission• compressed voice is variable bit rate (VBR) but delay

sensitive

• AAL2 enables these low bit rate and delay sensitive applications to share a single ATM VCC

• improve the network bandwidth utilisation • reduce the call establishment time

• AAL2 is especially suitable for carrying voice packets that are produced by speech codecs

• AAL2 also supports longer packet lengths up to 64 Kbytes


AAL2 (1/2)

OFFSET FIELD, 1 byte (indicates where the next AAL2 PDU starts)

AAL PACKET, fixed header, payload

ATM CELL, 5-byte header + 48-byte payload

String of AAL Packet Data Units

1 2 3 4

AALheader

ATM CELLHEADER 1 2 3 4

ATM cell

Transmission pathVirtual PathVirtual Channel (VC)ATM Cell

User Layer


ATM Layer


AAL2 (2/2)

String of AAL2 Packet Data Units String of AAL2 Packet Data Units

1 2 3 4 5 6

AAL2header

AAL2 is suitable for delay critical applications

ATM CELLHEADER

ATM CELLHEADER

HEADER = 5 BYTES

PAYLOAD = 48 BYTES

1 2 3 4 4 5 6

ATM cell

OFFSET FIELD, 1 byte (indicates where the next AAL2 PDU starts)

AAL2 PACKET, fixed header, variable length payload (max. 48 bytes)


PADDING


AAL2 cell packingLow bit rate voice

ch#4

ch#3

ch#2

ch#1

Silence

. . . .

. . . .

Short packet hh ch#1ch#1 hh ch#2ch#2 hh ch#3ch#3 hh ch#4ch#4 hh ch#2ch#2 . . . .

StandardATM cell

HH

Start field

HH

CID (Channel ID) in the header


ATM Adaptation Layer 2 sublayers

CPS Common Part SublayerSSCS Service Specific Convergence Sublayer

ATM layer

Higher layers

AAL2 CPS

AAL2 SSCS

CPS AAL2 channel multiplexing and demultiplexing

Segmentation and reassembly function

for application packets

AAL2

User data

Put 3-byte header that includes a single byte Channel ID (CID)


ATM Adaptation Layer 5

• AAL5 can be used for• IP over ATM• Frame Relay/ATM interworking• signalling traffic bearer

• AAL5 is used for Internal control connections between units in RNC and MGW.


AAL5

PADDING FIELD, variable length to fill the 48-byte ATM cell

AAL5 PACKET, fixed header, variable length payload


AAL5 Packet Data Unit AAL5 Packet Data Unit

USER DATA - Variable length 1 - 65 535 bytesUSER DATA - Variable length 1 - 65 535 bytes

PAYLOAD = N x 48 BYTES

AAL5header

ATM cell 1 ATM cell 2………... ………..ATM cell n

AAL5 is suitable for packet data


ATM Adaptation Layer 5 sublayers

CS Convergence SublayerCPCS Common Part Convergence SublayerSAR Segmentation and Reassembly Sublayer

SDU Service Data UnitSSCF Service Specific Co-ordination FunctionSSCOP Service Specific Connection Oriented ProtocolSSCS Service Specific Convergence Sublayer

ATM layer

Higher layers

AAL5 CPS

AAL5 SSCS

CPCS Transparent transport of

SDUs

SSCFMaps Layer 3 to SSCOP

SSCOPReliable data transfer

SARSDU segmentation and

reassembly

Co

mm

on

par

t


Switching in ATM network

• Switching in ATM layer• VP switching• VC switching

• Switching in AAL layer Type 2


Virtual channel and virtual path switching

VPI 3

VPI 8

VPI 36

VPI 23 VPI 9

VP switch

Port

VCI 9VCI 10

VCI 9VCI 10

VCI 15

VCI 26

VCI 9VCI 10

VC switch

Port

Port


ATM virtual connections and AAL2 connections

VCC

User 1

User 2

User 3

PHY

ATM

AAL2

H #1 #2

Process

#3

ATM cell

Upper layer

PHY

ATM

AAL2 Process

H #1 #2 #3

ATM cell

Upper layer

H #5 #6 #7 ATM

AAL2

H #5 #6

Process

#7

ATM cell

Upper layer

BS RNC MGW

VCC

ATM connection

AAL2 connections

ATM connection

PHY

ATM cell


Signalling in 3G network

• Signalling protocol layers• Control Plane• User Plane

• AAL Type 2 Signalling


ATM protocol for signalling and user data

Physical layer

ATM layer

SignallingAAL (SAAL) AAL

Signalling protocol User data

C-Plane U-Plane


Signalling protocol layers

SAAL Signalling ATM Adaptation LayerSCCP Signalling Connection Control PartSSCF Service Specific Coordination FunctionSSCOP Service Specific Connection Oriented

AAL5 ATM Adaptation Layer 5B-ISUP Broadband ISDN User PartMTP3 Message Transfer Part lever 3NBAP Node B Application Protocol

Physical Layer

ATM Layer

SAR

CPCS

SSCOP (Q.2110)

SSCF (Q.2140)

MTP3b

SSCS SAAL

SS#7

B-ISUP

NNI

SAAL UNI SAAL NNI

AAL5

Signalling protocol e.g. NBAP

AAL5

UNI

Physical Layer

ATM Layer

SAR

CPCS

SAAL

SSCOP (Q.2110)

SSCF (Q.2130)SSCS

AAL5

SCCP

RNSAP/RANAP


AAL type 2 signalling

• AAL type 2 signalling protocol is a separate new protocol- not an extension of any existing ATM signalling protocols

• AAL type 2 signalling protocol provides functions to dynamically establish and release AAL type 2 point-to-point connections.

• The benefits of AAL2 signalling:

• The speed of AAL2 connection establishment is increased because intermediate ATM switches do not delay the process storing and forwarding AAL signalling protocol messages.

• The switched AAL2 connection can be established on top of any ATM network regardless of the protocol used for establishing ATM level connections.


AAL type 2 signalling protocol

RNSAP/RANAP AAL2 SIG

MTP3b

ATM

SSCF-NNI

SSCOP

AAL5

SSCF-UNI

STCSCCPNBAP

Physical

AAL2 SIG AAL type 2 signallingMTP3b Broadband Message Transfer Part lever 3NBAP Node B Application ProtocolRNSAP Radio Network System Application Part

RANAP Radio Access Network Application PartSSCF Service Specific Co-ordination FunctionSSCOP Service Specific Connection Oriented ProtocolSTC Signalling Transfer Converter


AAL type 2 signalling protocol architecture

AAL Type 2Served userAAL Type 2Served user

AAL Type 2Signalling


MTPConverter

MTPConverter

SAAL-UNIConverterSAAL-UNIConverter

…….Converter

…….Converter

SAAL-UNISAAL-UNI …….Converter

…….Converter

MTP Layer 3

SAAL-NNI

SignallingProtocol

SignallingTransportConverter

SignallingTransport

AAL Type 2

SignallingMessages

AAL Type 2Served userAAL Type 2Served user



MTPConverter

MTPConverter

SAAL-UNIConverterSAAL-UNIConverter

…….Converter

…….Converter

SAAL-UNISAAL-UNI …….Converter

…….Converter

MTP Layer 3

SAAL-NNI


ATM as a transport network in 3G

UNI User Network InterfaceNNI Network Node Interface

PSTNMGW MSCBSUE

A BIu-CSIubUu

UNI NNI

IP networkGGSN

Iu-PS

NNI

RNC

SGSN

RNCBS

BS

Iur

NNI

UNI

UNI

ATM is employed

Gn Gi


Why is the ATM selected as a transport network in 3G?

• ATM provides efficient support for transmission of voice, data, and video

• ATM provides QoS guarantee and reliability

• ATM utilises statistical multiplexing, so• less bandwidth can be reserved• transmission cost saving are considerable

• ATM supports the soft handover functionality

• AAL2 meet the specific requirements of mobile telephony such as low delay and loss

• AAL2 allows low bit rate and delay sensitive applications to share a single ATM connection

• maximise the network utilisation


General protocol modelfor UTRAN terrestrial interfaces

TransportNetworkLayer

RadioNetworkLayer

ALCAP(s)

Signalling Bearer(s)

Application Protocol

Signalling Bearer(s)

Data Stream(s)

Data Bearer(s)

User PlaneControl Plane

TransportNetwork

Control Plane

TransportNetwork

User Plane

TransportNetwork

User Plane

Physical Transmission layer

ALCAP Access Link Control Application Part

All UTRAN-related issues are visible only in the radio network layer

Used for all 3G specific control signalling such as setting up bearers to the UE

- RANAP in Iu - RNSAP in Iur - NBAP in Iub- etc.

Always set up by O&M

Used for all control signalling within the transport network layer

Used to set up and tear down data bearers for the user plane

Always set up by O&M


Protocol structure for Iub


RadioNetworkLayer

AAL2 SIG (Q.2630.1)

NBAP

DC

H F

P

AAL2

Transport NetworkUser Plane


ATM

Transport NetworkControl Plane


AAL5

SSCF-UNISSCOP

AAL5

STC(Q.2150.2)SSCF-UNI

SSCOP

RA

CH

FP

FA

CH

FP

PC

H F

P

DS

CH

FP

CP

CH

FP



Protocol structure for Iur


RadioNetworkLayer

AAL2 SIG (Q.2630.1)

RNSAP DCH FP

AAL2



ATM



AAL5

SCCPMTP3b

SSCF-NNISSCOP

AAL5

STC (Q.2150.1)MTP3b

SSCF-NNISSCOP

CCH FP



Protocol structure for Iu-CS


RadioNetworkLayer

AAL2 SIG (Q.2630.1)

RANAP

AAL2



ATM

Control Plane


User Plane


AAL5

SCCPMTP3b

SSCF-NNISSCOP

AAL5

STC Q.2150.1)MTP3b

SSCF-NNISSCOP

Iu User Plane Protocol


Protocol structure for Iu-PS


RadioNetworkLayer

RANAP Iu User Plane Protocol



ATM



AAL5

SCCPMTP3b

SSCF-NNISSCOP

AAL5

GTP-UUDP

IP



ATM Adaptation Layer for User Plane


PSTNMGW MSCBSUE

A BIu-CSIubUu

IP networkGGSN

Iu-PS

RNC

SGSN

RNCBS

BS

Iur

Gn Gi

AAL2 AAL2

AAL5

AAL2

AAL2

AAL2


ATM Adaptation Layer for Control Plane


PSTNMGW MSCBSUE

A BIu-CSIubUu

IP networkGGSN

Iu-PS

RNC

SGSN

RNCBS

BS

Iur

Gn Gi

RANAPSCCPMTP3

NNI SAAL (AAL5)

RANAPSCCPMTP3

NNI SAAL (AAL5)

RNSAPSCCPMTP3

NNI SAAL (AAL5)

NBAPUNI SAAL (AAL5)

NBAPUNI SAAL (AAL5)


ATM Adaptation Layer for Transport Network Control Plane

(AAL type 2 signalling)


PSTNMGW MSCBSUE

A BIu-CSIubUu

IP networkGGSN

Iu-PS

RNC

SGSN

RNCBS

BS

Iur

Gn Gi

AAL2 SIGSTC

MTP3bNNI SAAL (AAL5)

AAL2 SIGSTC

MTP3NNI SAAL (AAL5)

AAL2 SIGSTC

UNI SAAL (AAL5)

AAL2 SIGSTC

UNI SAAL (AAL5)


Iu -CS UP

A/µ-law,PCM,UDI,etc.

WCDMAL1

MAC

RLC-U

E.g. Vocoder

PHY

ATM

AAL2

FP

WCDMAL1

PHY PHY

ATM ATM

AAL2 AAL2

FP

MAC

RLC-U

PHY PHY

ATM

AAL2

Iu -CS UP

E.g. Vocoder

Link Layer

PHY PHY

Link Layer

A/µ-law,PCM,UDI,etc.

PSTNN-ISDN

PSTNMGW MSCRNCBSUE

A BIu-CSIubUu

PHY

ATM

AAL5

SSCOP

SSCF-UNI

PHY

ATM

AAL5

SSCOP

SSCF-NNI

MTP3b

SCCP

RANAPNBAP

PHY

ATM

AAL5

SSCOP

SSCF-UNI

NBAP

PHY

ATM

AAL5

SSCOP

SSCF-NNI

MTP3b

SCCP

RANAP

PHY

TDM

MTP

SCCP

BSSAP'

PHY

TDM

MTP

SCCP

BSSAP'

UNI NNI

USER PLANE

CONTROL PLANE

Protocol Stack for Circuit Switched Data


Protocol Stack for Packet Switched Data

PHY

ATM

AAL5

SSCOP

SSCF-UNI

PHY

ATM

AAL5

SSCOP

SSCF-NNI

MTP3b

SCCP

RANAPNBAP

PHY

ATM

AAL5

SSCOP

SSCF-UNI

NBAP

PHY

ATM

AAL5

SSCOP

SSCF-NNI

MTP3b

SCCP

RANAP

RNC SWU MSC

GTP-U

UDP

ATM ATMWCDMA

L1

MAC

RLC-U

PDCP

E.g.IPv4, IPv5

PHY

ATM

FP

PHY PHY

AAL2AAL2WCDMAL1

AAL5

FP LLC/SNAP

MAC IP

RLC-U

PDCP

ATMAAL5

LLC/SNAPLink

Layer

IP IP

GTP-U

UDP

PHY PHY PHY

LinkLayer

IP

UDP

E.g. IPv4, IPv5

PHY

GTP-U GTP-U

UDP

IPnetwork

SGSN GGSNRNCBS

Iu-PSIubUu

UNI NNI

USER PLANE

CONTROL PLANE

Gn Gi

UE

SAAL NNISAAL UNI


RNC

PHY

ATM

AAL2

FP

RNC

Iur

SWU

PHY

ATM

AAL5

SSCOP

SSCF-NNI

MTP3b

SCCP

RNSAP

PHY

ATM

AAL5

SSCOP

SSCF-NNI

MTP3b

SCCP

RNSAP

NNI

USER PLANE

CONTROL PLANE

RNC

RNC

PHY

ATM

AAL2

FP

SAAL NNI

Protocol Stack for Iur Interface


AAL type 2 signalling

PSTNMGW MSCRNCBSUE

AIu-CSIubUu

UNI NNI

PHY

ATM

AAL5

SSCOP

SSCF-UNI

STC (Q.2150.2)

AAL2 SIG

PHY

ATM

AAL5

SSCOP

SSCF-UNI

STC (Q.2150.2)

AAL2 SIG

PHY

ATM

AAL5

SSCOP

MTP3b

STC (Q.2150.1)

AAL2 SIG

PHY

ATM

AAL5

SSCOP

MTP3b

STC (Q.2150.1)

AAL2 SIG

RNC

Iur

NNIRNC

PHY

ATM

AAL5

SSCOP

MTP3b

STC (Q.2150.1)

AAL2 SIG

PHY

ATM

AAL5

SSCOP

MTP3b

STC (Q.2150.1)

AAL2 SIG

SSCF-NNI SSCF-NNI

SSCF-NNI SSCF-NNI


ATM Protocols and SignallingATM Protocols and Signalling

Review Questions


1. Fill in the type of the AAL used at different interfaces for user

traffic

PSTNUE

A BIu-CSIubUu

IP network

Iu-PS

Iur

Gn Gi

BS RNC MGW MSC

BS RNC

BSSGSN GGSN

AAL2 AAL2

AAL2

AAL2 AAL5

AAL2


2. Fill in the type of the AAL used at different interfaces for control

traffic

PSTNUE

A BIu-CSIubUu

IP network

Iu-PS

Iur

Gn Gi

NBAPUNI SAALAAL5

BS RNC MGW MSC

BS RNC

BSSGSN GGSN

NBAPUNI SAAL (AAL5)

RANAPSCCPMTP3NNI SAAL (AAL5)

RNSAPSCCPMTP3NNI SAAL (AAL5)

RANAPSCCPMTP3NNI SAAL (AAL5)

NBAPUNI SAAL(AAL5)


3. Which of the following statementsis not true?

a) The AAL type 2 signalling provides functions to dynamically establish and release AAL type 2 point-to-point connections.

b) The AAL type 2 signalling protocol is at Iub, Iur, and Iu-CS interface to set up the AAL2 connection for user traffic.

c) The signalling bearer under AAL type 2 signalling at Iub interface is SAAL UNI.

d) The signalling bearer under AAL type 2 signalling at Iur interface is SAAL UNI.


4. Fill in the type of AAL used at different interfaces for AAL type

2 signalling


PSTNUE

A BIu-CSIubUu

IP network

Iu-PS

Iur

Gn Gi

NBAPUNI SAAL

AAL5

BS RNC MGW MSC

BS RNC

BSSGSN GGSN

AAL2 SIGSTCUNI SAAL (AAL5)

AAL2 SIGSTCMTP3bNNI SAAL (AAL5)

AAL2 SIGSTCMTP3bNNI SAAL (AAL5)

AAL2 SIGSTCUNI SAAL (AAL5)


ATM Adaptation Layer for User Plane

UNI User-Network InterfaceNNI Network-Node Interface

PSTNUE

A BIu-CSIubUu

IP network

Iu-PS

Iur

Gn Gi


ATM Adaptation Layer for Control Plane


PSTNUE

A BIu-CSIubUu

IP network

Iu-PS

Iur

Gn Gi

NBAPUNI SAAL

AAL5


ATM Adaptation Layer for Transport Network Control Plane

(AAL type 2 signalling)


PSTNUE

A BIu-CSIubUu

IP network

Iu-PS

Iur

Gn Gi

NBAPUNI SAAL

AAL5


What, where, and why ATM ?

• What is ATM ?• Asynchronous Transfer Mode• Based on fixed length packet (each ATM packet = 53 bytes)• Connection oriented (virtual circuits, virtual paths)• Different adaptation layers for different types of services.

• Where is ATM used in 3G?• Specified by 3G PP R99 to be used in Iu, Iub, and Iur.

• Why is ATM chosen for 3G? • Industry trend to migrate towards Packet Switched Data (like ATM and IP)• To enable Voice Over IP, Streaming video, videoconferencing Quality of Service (QoS) becomes an important issue• Back then and even today, IP networks don't fulfil the QoS requirements, ATM does

Documents

ATM Protocol and Signalling by ziafat ali