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European Advanced Networking Test Center

Transport ofVoice over ATM

with Adaptation Layer 2ATM User Conference, Stuttgart 2001

Gabriele SchrenkManaging Director

EANTC AG


Topics

! Introduction EANTC

! AAL2 Technology and Applications

! Current Status and Outlook


About EANTCHighly specialised Provider of

Services in the field of NetworkTechnologies

Vendor-IndependentNetwork Quality Assurance

EANTC Business Areas! Test and certification of network

components for manufacturers! Test of high-speed enterprise /

service provider networks andnetwork design consultancy

! Research and development oftest methods and analysis tools

! Vendor-neutral technology seminars(both ATM & MPLS)

EANTC, Berlin-Charlottenburg


Interoperability Test EventsEANTC periodically invites all

manufacturers of networkingequipment to join

MPLS Group Testing Events:November 2001: MPLS Virtual Private

Networks / Traffic Engineering09/2000: MPLS (RSVP-TE, LDP, CR-LDP)April 2000: ATM Hierarchical PNNI 1.01999: ATM PNNI 1.0, MPLS, MPOA1998: ATM Signalling Performance,

Traffic Management (ABR), MPOA1997: ATM Signalling / Routing

PNNI 1.0, UNI 4.01996: LAN Emulation 1.01995: ATM Signalling UNI 3.0 / 3.1

MPLS Participants since 1999:3Com, Agilent, Alcatel, AviciSystems, Cabletron, Cisco Systems,Data Connection, Juniper Networks,NetTest/GN Nettest, Inverness, Ixia,Marconi/Fore Systems,NortelNetworks/Bay Networks,Riverstone, Radcom, Siemens,Spirent Communications


Motivation for AAL 2

Introduction and Concepts


Transport Voice over ATM

Use AAL1?! Supports isochronous service! Suitable for ISDN channels! Low-Bandwidth performance?! Transport of compressed voice in fixed-length packets does

not perform well

Use AAL5?! Supports Voice-over-IP-like service! Variable packet length possible! Does not support isochronous services! Low-Bandwidth performance?


AAL1 vs. AAL2 Performance

Compressed Voice: ≤ 8Kbit/sAAL1 Performance:

! 8000 bit/s : 47*8 bit/cell= 20 cells/s ≅ 1 cell / 50 ms

Partial cell fill method! 10 Bytes/Cell => 1 cell / 10 ms! But: 37 of 47 Bytes/Cell wasted = 78 %

Virtual ChannelAAL 1 AAL 1


AAL2 Solution

Solution: Multiplex multiple small-bandwidth voicechannels onto one ATM channel

Carrier


AAL 2 - Concept

AAL 2 defines an ATM overlay network:

Short packet switching network! Connection oriented network with point-to-point capability only! Maximum packet size is 45 Byte! AAL2 Signalling is introduced for AAL2 channel management

Short PacketMUX

Short PacketMUX ATM Switch

ATM Virtual Channel

AAL2 Signalling

ATM Signalling ATM Signalling

AAL2 Data Channels


AAL 2 - Standards! I.363.2 ATM Adaptation Layer 2 (1997)

! I.366.2 AAL2 Sublayer for Trunking (1999)

! Q.2630.1 AAL Type 2 Signalling Protocol (1999)

! af-vmoa-0145 ATM Loop Emulation Serviceusing AAL2 (2000)


AAL 2 - Transmission

CPS-SDUs

CPS-Packets

CPS-PDUs

ATM Cells

Time

45 oct.

28 oct.

45 oct.

45 oct.

21 oct.

42 oct.28 oct.

Idle Cell


AAL2 Layers and Services

Applications:

! Carrier Trunking

! Loop Emulation Service


AAL2 Higher Layers

ATM Layer

SSCS

Common Part SublayerCPS

ATMAdaptationLayer(AAL2)

Assured Data Transfer

Error Detection

Segment. / Reassembly

BasicTrunkingService

CarrierTrunking

Loop EmulationService


AAL2 Basic Trunking ServiceI.366.2: Carry narrow-band telephony calls over AAL2

! Voice (analog / ISDN, optionally compressed)! Voice-band data (modem, fax calls)! Circuit mode data (ISDN data)

! Secondary Messaging: Dialled Digits (DTMF),Fax Demodulation, …

Trunking service implements complex mechanisms toemulate analog / ISDN telephony service

=> Higher-layer protocols needed for call management


Voice over ATM Carrier TrunksOne major application for Voice over ATM:

! Tunnels long-distance voice calls over ATM backbone! Substitutes Circuit Emulation Service (CES)

Benefits:! Scalable for lots of parallel calls (trunks of 256

connections each)! Ability to compress calls up to 10x – cost-saving! May use intelligent ATM routing / rerouting! With ATM traffic management, voice can be routed

through the same backbone as IP data


AAL2 Carrier Trunks: Example

ISDN030

ISDN069

ISDN089

ATM

A

B

C

D

AAL 2 Routing Table089 D069 B030 A

PNNI RoutingSW1 390276FAC..SW2 39FF0239....SW3 470005FE80

AAL2 Signalling MessageERQ Length = xyz

Conn. El. Id

Dest. E164+49891234567

AAL2 Trunk

SW1

SW3

SW2

Relay


Loop Emulation Service

Second major application for Voice over ATM

Idea: Extend the ‘local loop’ through an ATM accessnetwork

Support voiceband services:! from Public Switched Telephone Network (PSTN)! to customer premises equipment! over bandwidth-constrained ATM connections

Used in Digital Subscriber Line (xDSL) architectures


LES Reference Model

ATMNetwork

DSLAM

xDSL

Internet

PSTN

GR-303TR-008V5.x

EnterpriseNetwork

Data gateway

VoiceGatewayIAD

IAD

Data connection between“DSL modem” and router

Digital Subscriber Loop (DSL)

Voice connection between“Integrated Access Device”(IAD) and Voice gateway


LES Protocol Stacks

Transparently relays the analog / ISDN voiceservice through ATM:

ISDN on topof Trunking,AAL2 cells,

ATM(complex

hierarchy)

Transparent ISDN


Loop Emulation Service Benefits! Provide voice services to data (IP) xDSL customers

over the same infrastructure(generates additional revenue)

! Simplifies voice infrastructure construction forcompetitive carriers: Expensive local exchanges canbe centralized at any point in the ATM backbone

! In contrast to Voice over IP: Provides 100 % the sameanalog / ISDN voice service as before(including metering pulse, national ISDN, …)


Current Status

and Future ofVoice over ATM


Current StatusLoop Emulation Service:

! Voice over DSL (VoDSL) standards complete! A lot of manufacturers currently develop Integrated Access

Devices (IADs) and Voice Gateways! DSL infrastructure available in European / US market! First mass deployments expected Q1/2002?

Carrier Trunks:! Implementations for Mux/Demux available! First installations already seen (no mass deployment expected)! Relay (AAL2 trunk router) implementations not yet available


Outlook

AAL2 Carrier Trunks will also be used in …! 3rd generation mobile networks (UMTS, currently

tested)! Voice over MPLS (VoMPLS) trunks in IP carrier

networks (early development)

AAL2 Loop Emulation Service will also be used in…! Other types of ATM-based access networks

(Cable TV / Powerline, up to street cabinets)


Conclusion! Substantial number of applications for AAL2 under

development

! Future competition with VoIP, MEGACO, etc.as well as Metro Ethernet access expected

! ATM / AAL2 is the first voice technology for packetaccess networks available with ISDN service quality

! AAL2 might even be used without underlying ATM(VoMPLS, VoUMTS)


Thanks! Any Questions?

Please visit our homepagewww.eantc.com

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