Topics. Transport of Voice over ATM with Adaptation Layer 2 ATM User Conference, Stuttgart ! Introduction EANTC

Transcription

1 Transport of Voice over ATM with Adaptation Layer 2 ATM User Conference, Stuttgart 2001 Gabriele Schrenk Managing Director EANTC AG Topics! Introduction EANTC! AAL2 Technology and Applications! Current Status and Outlook

2 About EANTC EANTC, Berlin-Charlottenburg Highly specialised Provider of Services in the field of Network Technologies Vendor-Independent Network Quality Assurance EANTC Business Areas! Test and certification of network components for manufacturers! Test of high-speed enterprise / service provider networks and network design consultancy! Research and development of test methods and analysis tools! Vendor-neutral technology seminars (both ATM & MPLS) Interoperability Test Events MPLS Participants since 1999: 3Com, Agilent, Alcatel, Avici Systems, Cabletron, Cisco Systems, Data Connection, Juniper Networks, NetTest/GN Nettest, Inverness, Ixia, Marconi/Fore Systems, NortelNetworks/Bay Networks, Riverstone, Radcom, Siemens, Spirent Communications EANTC periodically invites all manufacturers of networking equipment to join MPLS Group Testing Events: November 2001: MPLS Virtual Private Networks / Traffic Engineering 09/2000: MPLS (RSVP-TE, LDP, CR-LDP) April 2000: ATM Hierarchical PNNI : ATM PNNI 1.0, MPLS, MPOA 1998: ATM Signalling Performance, Traffic Management (ABR), MPOA 1997: ATM Signalling / Routing PNNI 1.0, UNI : LAN Emulation : ATM Signalling UNI 3.0 / 3.1

3 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?

4 AAL1 vs. AAL2 Performance AAL 1 Virtual Channel AAL 1 Compressed Voice: 8Kbit/s AAL1 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 % AAL2 Solution Carrier Solution: Multiplex multiple small-bandwidth voice channels onto one ATM channel

5 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 AAL2 Signalling AAL2 Data Channels ATM Virtual Channel Short Packet MUX ATM Signalling ATM Switch ATM Signalling Short Packet MUX AAL 2 - Standards! I ATM Adaptation Layer 2 (1997)! I AAL2 Sublayer for Trunking (1999)! Q AAL Type 2 Signalling Protocol (1999)! af-vmoa-0145 ATM Loop Emulation Service using AAL2 (2000)

6 AAL 2 - Transmission Time 45 oct. 45 oct. 21 oct. CPS-SDUs 28 oct. 45 oct. 28 oct. 42 oct. CPS-Packets CPS-PDUs ATM Cells Idle Cell AAL2 Layers and Services Applications:! Carrier Trunking! Loop Emulation Service

7 AAL2 Higher Layers Carrier Trunking Loop Emulation Service Assured Data Transfer ATM Adaptation Layer (AAL2) Basic Trunking Service Error Detection Segment. / Reassembly SSCS Common Part Sublayer CPS ATM Layer AAL2 Basic Trunking Service I.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 to emulate analog / ISDN telephony service => Higher-layer protocols needed for call management

8 Voice over ATM Carrier Trunks One 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 AAL2 Signalling Message ERQ Length = xyz Conn. El. Id Dest. E AAL2 Trunk ISDN 030 A SW3 ATM Relay C AAL 2 Routing Table 089 D 069 B 030 A ISDN 069 B SW1 SW2 PNNI Routing SW FAC.. SW2 39FF SW FE80 D ISDN 089

9 Loop Emulation Service Second major application for Voice over ATM Idea: Extend the local loop through an ATM access network 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 Data connection between DSL modem and router Internet Data gateway Enterprise Network IAD xdsl ATM Network DSLAM PSTN IAD Digital Subscriber Loop (DSL) Voice connection between Integrated Access Device (IAD) and Voice gateway Voice Gateway GR-303 TR-008 V5.x

10 LES Protocol Stacks Transparently relays the analog / ISDN voice service through ATM: ISDN on top of 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 for competitive carriers: Expensive local exchanges can be centralized at any point in the ATM backbone! In contrast to Voice over IP: Provides 100 % the same analog / ISDN voice service as before (including metering pulse, national ISDN, )

11 Current Status and Future of Voice over ATM Current Status Loop 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

12 Outlook AAL2 Carrier Trunks will also be used in! 3 rd 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 packet access networks available with ISDN service quality! AAL2 might even be used without underlying ATM (VoMPLS, VoUMTS)

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