AAL2 Optimal

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AAL2 Overview

Prepared by: ETK/DCS Tamara Dumić

Top right corner for field-mark, customer or partner logotypes. See Best practice for example.

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Ericsson Confidential AAL2 OverView 2006-10-102

• Concept introduced by Ericsson on ISS-95 (1995)• Bandwidth efficient transmission of low rate, short and

variable length packets in delay sensitive applications• Several (up to 248) AAL2 user information streams are

multiplexed on the same ATM connection.• Standardized in ITU-T I.366, I.363, Q.2630• Ericsson owns the “AAL2 patent”

• Inventor: Lars-Göran Petersen

• Cello supports:• node internal AAL2 connections• network wide AAL2 connections

• Cello may also act as a pure AAL2 switch

ATM adaptation layer 2

ATM Cells

User 1 User 2 User 3 User 1


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Service Specific CS

Common Part Sublayer

SAP

SAP

SS

CS

CP

S

Com

mon

Par

t

AA

L2

ATM

AAL2 layer

CPS is implemented on ET as AAL2 multiplexor/demultiplexor

SSSAR is implemented on SPM (or application device)

AAL2U is the interface between CPS and SSSAR


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AAL2 Service Specific Convergence Sublayer, SSCS (ITU-T I-366.1)

• Support for Service Specific Segmentation and Reassembly, SSSAR

• SSSAR-SDUs of up to 2048 octets supported on the SP boards

• Service Specific Transmission Error Detection, SSTED, and Service Specific Assured Data Transfer, SSADT, are NOT supported

Service Specific CS

Common Part Sublayer

SAP

SAP

SS

CS

CP

S

Com

mon

Par

tAA

L2

ATM


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AAL2 CPS-packet (I.363.2)

CID LI

UUI HEC CPS-INFOCID LI

HECUUI

CPS-INFO

Channel Identifier Length Indicator

Header Error ControlUser-to-User Indication

Information (Payload)

(8 bits) (6 bits)

(5 bits)(5 bits)

(1-45 octets*)*64 octet option is NOTsupported

CPS-packet header3 bytes

CPS-packet payload


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AAL2 CPS PDU

OSF SN

SN P PADOSF

ATMheader

PADP

Offset fieldSequence number

PaddingParity

(6 bits) (1 bit)

(0 to 46 octets)(1 bit)

Start field1 octet

CPS-PDU payload

CPS-PDU

AAL2 CPS packet


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Multiplexing of AAL2 CPS packets

ATM header 5 bytes

Payload 47 bytes

Connection 1

Conn. 2

Conn. 3

Conn. 1

….ATM connection

ATM cell

AAL2 CPS-packet

AAL2 connections

CPS packet header, 3 bytes

CPS PDU header 1 byte


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AAL2 path carrying multiplexed AAL2 connections

AAL2 connection segment (AAL2U)

AAL2 Mux/demux

ET board

ATM port

Switch

Device with AAL2 SAP

AAL2 Mux/demux

ET board

ATM port

Switch

AAL2U

AAL2SSAR

User

L1L1L1

ATMATM

L1PHY

SAP

AAL2U

L1L1

AAL2CPS

ATMAAL2U

AAL2SSAR

User

L1 L1 L1

ATM ATM

L1 PHY

SAP

AAL2U

L1 L1

AAL2CPS

ATM

AAL2 Path

AAL2 Link

AAL2U Link AAL2U Link

AAL2 Connection

AAL2 Connection

AAL2 CEP

AAL2 SAP or ATM SAP

AAL2 CP

AAL2 Data Transport


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WCDMA RAN Architecture

AAL2


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Iub Interface Protocol Stack

DC

H

FP

RA

CH

F

P

DC

H

FP

PC

H

FP

NBAP

Q.2630.2

UNI SAAL

AAL5

UNI SAAL

AAL5

ATM

AAL2

Physical Layer


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CPP Signaling & Transport services

SIGNALLINGSERVICE

TRANSPORT SERVICECONTROL PLANE

TRANSPORT SERVICE USER PLANE

Ethernet

AAL2

PDH/SDH

TDM

Q.2630

AAL0

SCCP

UNI-SAAL

AAL5AAL1

MTP L2

Connection Control

Application

MTP L3 / MTP L3b / M3UA

NNI-SAAL SCTP

ATMIP

UDP


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AAL2 Implementation Structure

Subsys ANS - ATM Network Signalling

Software blocks:AAL2 Network Connection ControlAAL2 Access PointAAL2 CPS Resource ControlAAL2 Netw. Conn. Ctrl. Administrator

Software blocks:AAL2 SSCS AdministratorAAL2 SSCS Resource Control

Software blocks:AAL2 Path End-Point AdministratorAAL2 CPS Data Transfer

Software blocks:AAL2 SSCS Data Transfer

AAL2 Transport Services Interface

Subsys ACT - ATM Connection Control and Terminations

Subsys AET - ATM Exchange Terminals Subsys SPP - Special Purpose Processors

Subsys CMACello Management Adaptations

AAL2 MAOs:Aal2 ApAal2 SpAal2 Routing CaseAal2 Path Vcc TpAal2 Path DistributionUnitAal2QosProfileAal2QosCodePointProfile

Cello ManagedObject Interface

AAL2NCI AAL2GRI AAL2RI AAL2ERI AAL2EDI

PEFIAAL2RI

AAL2AIAAL2GRI

MAO-fROIFs

MAO-fROIFs

A2RI


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MOM


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Operator’s view...

Aal2Sp‘50001’

Aal2ApapFroId=12

AAL2 network address of a node (A2EA)

CPP node

AESAList of (AP id, Priority)

‘50002’ (12,1)

‘12345’ (11,1) (13,2)

Aal2RoutingCase

Aal2PathVccTp

Aal2PathVccTp

Aal2PathVccTp

Other node

‘50002’

Aal2PathDistributionUnit

Aal2Ap

Data link

Signalling linkMTP3B or UNI-SAAL

Aal2ApapFroId=11

Aal2ApapFroId=13


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AAL2 Connection Types

SPB

CEP

SPB

CEP

SPB

CEP

SPB

CEP

AAL2link

CP

ET

CP

ET

CP

ET

AAL2link

CP

SPB ET

CEP

SPB

CEP

ORIG node TRANSIT node TERM node

AAL2 Network-Wide Connection

AAL2 Node internal (CEP-CEP)

AAL2 Node internal (CEP-SUGR/CEP)


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AAL2 CEP AAL2 CEPs (AAL2 terminations) are located

on:

– SPB board (in case of RNC)

– MSB board (in case of MGw)

– RAX, TX (in case of RBS) SSCS RC (AAL2 RH) manages CEPs for CPP

provided boards -> only SPB is a part of CPP

SPB

SPP SPP

SPP

SPPCEP

CEPCEPCEPCEP

CEP

processorId

AAL2ADM(SSCS ADM)

AAL2RH(SSCS RC)

Application

AAL2ERI

RNC control application uses AAL2ERI interface on ORIG

node to reserve AAL2 CEP on a processor located on SPB


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AAL2 CP

AAL2 Path contains 256 channels (248 used for traffic) Determined by channel ID (0-255) 0-7 not used (reserved for special purposes Q.2630)

AAL2Path VC

AAL2Path VC

VPPhysicallayer

VP

VC AAL2Path

VC AAL2Path

AAL2 Channel

AAL2 CP


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CEP/CP Differencies

CEP– Located on SPB, MSB,

RAX, TX boards– Reserved/released by

application over AAL2ERI

– SSCS RC is ERI server (ACT)

– cepId (50-450)– Every connection has 2

CEPs

CP– On ET boards– Reserved/Released by

AAL2NCC– Handled by

AAL2CPSRC program– cpId = cid (8-255)– Network wide

connection can use many CPs (depending on the number of nodes it is spanning)


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CPP Node BCPP Node A

MP

Appl.

MP

Device

User 1

Appl.

Reserveend point

Routing

NCIServer

NCIConnectrequest

Application signaling

CPP Node C

MP

ETET

Q.2630signaling

Q.2630signaling

Device

User 2ET ET

Reserveend point

AAL2 connection establishment

CEP CEP

Routing Routing


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AAL2 Interfaces and Functions - Originating Node

User control application

SSCSResource Control

Q.2630Access Point

CPSResource Control

SSCSData Transfer

CPSData Transfer

UserData Transfer

ATMData Transfer

Switch control

AAL2 EDI

MP

ETSP (/Appl Dev)

AAL2 ERI AAL2 NCI

AAL2RI

AAL2DI

AAL2 NetworkConnection Control

Q.2630signalling

Application layer signalling

Userdata

1. Setup transm. channel

2. Confirm (AESA, SUGR)3. Reserve CEP 4. Connect (CEP, AESA, SUGR)

5. Select & Reserve CP Req.6. Connect

7. ERQ

8. Connect CP8. Connect CEP

9. ECF


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AAL2 Interfaces and Functions - Transit Node

Q.2630Access Point

CPSResource Control

CPSData Transfer

ATMData Transfer

Switch control

MP

ET


Q.2630signalling

ATMData Transfer

CPSData Transfer

ETUserdata

Userdata

CPSResource Control

Q.2630Access Point

Q.2630signalling

1.ERQ

2.Reserve CP Res. 3.Select & Reserve CP Req.4.Connect5.ERQ

6.Connect CP Res. 6.Connect CP Res.

7.ECF 8.ECF


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AAL2 Interfaces and Functions - Terminating Node

User control application

SSCSResource Control

Q.2630Access Point

CPSResource Control

ATMData Transfer

CPSData Transfer

Switch control

MP

ET

AAL2 ERIAAL2 GRI

AAL2RI


Q.2630

Application layer signalling

Userdata

UserData Transfer

SSCSData Transfer

AAL2 EDI SP (/Appl Dev)

AAL2DI

2.Reserve CEP

1.Setup transm. channel

3.Reserve SUGR

4.Confirm (AESA, SUGR)

5.ERQ6.Reserve CP Res.

7.Reserve CEP Res.

8.Connect

9.Connect CP 9.Connect CEP

10.ECF


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AAL connections with different QoS demands are handled separately before entering the AAL2 Path

The AAL2 QoS separation provides better link utilization

AAL2 QoS separation

AAL2 PathQoS A

QoS C

AAL2 QoS Profile

AAL2MUX


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The AAL QoS classes are described by the bound for node delay, probability of delay and probability of loss

The values above are default values

AAL2 QoS classes

QoS class Delay Delayprobability

Lossprobability

A 5 ms 5/10.000 5/10.000

B 15 ms 5/10.000 5/10.000

C 25 ms 1 1

D 50 ms 1 1


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The AAL2 CAC and QoS separation provides more accurate QoS and better link utilization

AAL2 CAC

AAL2CAC

Current utilization + new connection OK?

=> Yes/No

New connection: - Bit rate - SDU size - QoS class OK?


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AAL2 routing

Routing function– Based on E.164 destination address– Points out an available AAL2 Access Point towards terminating node

An AAL2 Access Point controls a set of AAL2 paths of equal characteristics

Path selection within an AAL2 Access Point– Round-robin selection of AAL2 path– AAL2 path (ATM-link) status and CAC must give permission

Alternative Routing (Cello 3)– Each routing case can specify up to 5 (configurable) alternative AAL2

Access Points (AP) with the same or different priorities– Round Robin between APs is used as load sharing function with same

priority– Re-attempts are done due to local reject (AP is disabled or congested)– Loops between adjacent nodes are avoided


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ITU-T recommendation Q.2630.1/.2/.3 (Q.AAL2)

AAL type 2 Served User

AAL type 2 Signaling

Signaling BearerUNI-SAAL/MTP3b

Generic primitives

PrimitivesSAP

SAP

AAL type 2 Served User

AAL type 2 Signaling

Signaling BearerUNI-SAAL/MTP3b

Generic primitives

Primitives SAP

SAP

AAL2 signalling PDUs

Lay

erM

ana

gem

ent

Lay

erM

ana

gem

ent

Scope of Q.2630

Q.2150.1 (MTP3B)Q.2150.2 (SAAL UNI)

ERQ, ECF, REL, RLC,

RES, RSC, BLO, BLC, UBL, UBC

IN SERVICE, OUT OF SERVICE, CONGESTION,TRANSFERREQ, TRANSFERIND


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ANS/ACT subsystem mapping to AAL2

AAL2 Network Connection Control (ANS AAL2 NCC) provides supervision of application clients, routing of network wide AAL2 connections, reservation and release of SUGRs, control of connect and disconnect of a node internal and network wide AAL2 connections and control of communication towards data transfer applications.

AAL2 Common Part Sublayer Resource Control (ANS AAL2 CPSRC) provides AAL2 network control with means to reserve and release AAL2 channel resources on an AAL2 Path.

AAL2 Access Point (ANS AAL2 AP) provides Q.2630 signalling capabilities towards other nodes.

AAL2 Network Connection Control Administrator (ANS AAL2 NCC ADMIN) communicates with O&M functions for AAL2 managed objects and distributes AAL2 configuration data.

AAL2 Service Specific Common Sublayer Administrator (ACT AAL2 SSCS ADMIN) receives SSCS resources registration and distributes this information towards SSCS RC

AAL2 Service Specific Common Sublayer Resource Control (ACT AAL2 SSCS RC) provides application programs with service to reserve AAL2 Connection End Point.

AAL2 transport services (AAL2TS) provide application programs with interfaces to control node internal and network wide AAL2 connections and to send AAL2 data (AAL2ERI,AAL2NCI,AAL2GRI,AAL2RI, AAL2EDI).


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Differences between CPP releasesCPP5- selection of distribution unit- UBR+ Aal2 Path

CPP5.1- movable Aal2Ap and Aal2Pdu- improved Aal2Path selection- push of PM counters

CPP6- soft resource control distribution- removed unrestricted parameters on Aal2Ap

Prototyping work- Overload protection / Load control

Future- Q.2630.3 – connection priority, modification- better retainability- Aal2Path selection per subrack


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Documents and pages

http://www.design.etk.ericsson.se/DEPARTMENTS/ETK_D_C/sys_mng/aal2_subsys/index.shtml

FS - AAL2 Function Specification ( 155 17-96/CSX101 09 )FD – AAL2 Network Connection Control ( 1/15516-96/CSX 101 09 )FD – AAL2 Managment ( 2/15516-96/CSX 101 09 )FD – AAL2 SSCS ( 3/15516-96/CSX 101 09 )FD – AAL2 CPS ( 4/15516-96/CSX 101 09 )UG – AAL2 Transport Services ( 1553- CXA 104 201 )IWD – AAL2 connection Interfaces survey ( 155 19 – 96/CSX 101 09 )Delivery Module Description for AAL2 Distributed NCC

Transport services in Cello ( 4/1551 - CSX 101 09)


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