MPLS Migration Gets a Voice

Today, the MPLS/Frame Relay Alliance announced the completion of an implementation agreement that should make it easier for wireless and other carriers transmitting compressed voice traffic to migrate their backbones to IP/MPLS.

The new agreement, which is officially called "I.366.2 Voice Trunking Format over MPLS," is just one in a series of agreements the Alliance has been working on to help carriers migrate legacy services like voice to an IP/MPLS core (see MPLS Forum Makes Gains). Earlier this summer the Alliance formally announced an implementation agreement for Time Division Multiplexing over MPLS, which defines implementations for transporting constant bit-rate TDM traffic over Multiprotocol Label Switching (MPLS). (See MPLS/FRA OKs TDM-MPLS IA.)

All in all, these developments can only help the case for MPLS, which carriers are looking at for the purpose of unifying their IP and transport networks.

For example, some wireless providers have been using voice compression over an ATM backbone to bypass the voice network and avoid the tolls and regulations associated with it. As they shift toward IP/MPLS, their equipment needs to be updated so that traffic can be transmitted in its existing format.

There are other reasons why these MPLS developments could aid migration. Applications like voice that run over ATM transport require the addition of what’s called an ATM Adaptation Layer (AAL). These layers have been defined by the a International Telecommunication Union (ITU) and are used to “adapt” the nature of the applications to be transported over ATM. AAL 2 is the Adaptation Layer defined for compressed voice used in cellular networks.

Using current technology, it’s difficult and somewhat messy to transport AAL 2 traffic over an IP/MPLS backbone. There are a number of protocol conversions that must take place, which negates many of the efficiencies that IP/MPLS transport is supposed to provide.

The new implementation agreement from the MPLS/Frame Relay Alliance is designed to eliminate these conversions. Using an encapsulation methodology similar to ATM, the new standard provides a mechanism for AAL 2 traffic to be transported directly over an IP/MPLS backbone, just as it would be transported over an ATM backbone.

The biggest benefit for carriers is that it makes the IP/MPLS migration much easier and potentially less expensive. The only equipment that must be upgraded is the provider edge router. Standing radio and ATM gear can remain untouched.

“This makes the whole transition from ATM to IP/MPLS much smoother,” says Dave Sinicrope, working group chairman in the Alliance and a systems manager for LM Ericsson (Nasdaq: ERICY). “And they can also make this migration much more gradually without making big network changes.”

A few vendors are already at least partially in compliance with the new standard. RAD Data Communications Ltd., which has been pushing for this standard all along, has a product called the RAD Vmux, which already does much of this AAL 2 conversion.

Nortel Networks Corp. (NYSE/Toronto: NT) also has products that will likely be easily upgraded to handle the new standard. And Ericsson says it is working on a product that will comply with the standard.

Data-centric IP edge routing vendors like Cisco Systems Inc. (Nasdaq: CSCO), Juniper Networks Inc. (Nasdaq: JNPR), Laurel Networks Inc., and Riverstone Networks Inc. (Nasdaq: RSTNE) will likely have a tougher time adapting their products. These vendors have focused much of their attention on complying with Layer 2 data standards developed in the Internet Engineering Task Force (IETF), like Draft Martini, which defines point-to-point MPLS connections. Some people question whether these vendors would even attempt to get into this market.

“The data vendors aren’t completely comfortable with handling TDM traffic, especially compressed voice,” says Yaakov Stein, chief scientist at RAD Data Communications. “So I’m sure this won’t be a top priority for them, but eventually I expect they’ll try to add this functionality.”

— Marguerite Reardon, Senior Editor, Light Reading

techathiest 12/4/2012 | 11:23:20 PM
re: MPLS Migration Gets a Voice This story is incomplete. The MEF folks are also working on Circuit Emulation Services over MPLS. Why so much focus on RAD? There are other vendors like Atrica, Jedai and Luminous who do voice circuits over MPLS. Not sure if Jedai does voice circuits over MPLS or over Ethernet.

With MEF, MPLS forum and IETF all defining specs for carrying voice in MPLS encapsulated packets, how likely is any of the incumbent carriers to deploy it. Does the market exist?
Y(J)S 12/4/2012 | 11:22:55 PM
re: MPLS Migration Gets a Voice Dear techatheist,

I completely agree that circuit emulation is being treated in many fora (IETF, MPLS-FR Alliance, MEF, ITU-R/SG13) - perhaps too many!

But you seem to have missed the point here.

This Implementation Agreement is NOT about circuit emulation - that was covered by the previous IA (number 4.0). This one is about what is called in ATM terminology "loop emulation".

Unlike circuit emulation that handles constant bit-rate high-bandwidth TDM, this IA deals with
large numbers of low-bandwidth, variable-bandwidth, voice channels.

That is why the previous IA used AAL1, while this one uses AAL2.

The MEF, and the IETF (except for the AAL2 mode of draft-anavi) are NOT working on loop emulation at present.

It is useful to think of this IA as an efficient mechanism for transporting a large number of VoIP channels (since it supports compressed voice, silence suppression, tone and fax relay, etc.)
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