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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
European Advanced Networking Test Center
Topics
! Introduction EANTC
! AAL2 Technology and Applications
! Current Status and Outlook
European Advanced Networking Test Center
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
European Advanced Networking Test Center
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
European Advanced Networking Test Center
Motivation for AAL 2
Introduction and Concepts
European Advanced Networking Test Center
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?
European Advanced Networking Test Center
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
European Advanced Networking Test Center
AAL2 Solution
Solution: Multiplex multiple small-bandwidth voicechannels onto one ATM channel
Carrier
European Advanced Networking Test Center
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
European Advanced Networking Test Center
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)
European Advanced Networking Test Center
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
European Advanced Networking Test Center
AAL2 Layers and Services
Applications:
! Carrier Trunking
! Loop Emulation Service
European Advanced Networking Test Center
AAL2 Higher Layers
ATM Layer
SSCS
Common Part SublayerCPS
ATMAdaptationLayer(AAL2)
Assured Data Transfer
Error Detection
Segment. / Reassembly
BasicTrunkingService
CarrierTrunking
Loop EmulationService
European Advanced Networking Test Center
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
European Advanced Networking Test Center
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
European Advanced Networking Test Center
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
European Advanced Networking Test Center
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
European Advanced Networking Test Center
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
European Advanced Networking Test Center
LES Protocol Stacks
Transparently relays the analog / ISDN voiceservice through ATM:
ISDN on topof Trunking,AAL2 cells,
ATM(complex
hierarchy)
Transparent ISDN
European Advanced Networking Test Center
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, …)
European Advanced Networking Test Center
Current Status
and Future ofVoice over ATM
European Advanced Networking Test Center
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
European Advanced Networking Test Center
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)
European Advanced Networking Test Center
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)
European Advanced Networking Test Center
Thanks! Any Questions?
Please visit our homepagewww.eantc.com