Carriers get ready for MPLS-TP

CEN Feature (Dec 14 2010)

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   As carriers move farther away from traditional TDM network designs toward networks based largely on Ethernet, IP/MPLS and WDM, they continue to uncover new issues with which they must grapple.

    

   More and more carriers have deployed MPLS at their optical network core to enable the core network to act much like a TDM transport network but with a greater level of efficiency. And some carriers now are looking to achieve the same result in their access networks.

    

   Meanwhile, some carriers also are seeking the ability to configure Ethernet circuits end-to-end from routers located near the network edge through an optical core and back to routers located near the network edge at the opposite end of the connection.

    

   The emerging MPLS Transport Profile (MPLS-TP) aims to address both of those requirements.

    

   As Michael Howard, principal analyst for Infonetics Research, explains, carriers are most likely to consider using MPLS-TP in the aggregation network if that network is straining to support an increasing volume of video traffic. To address this, he says, many carriers are looking to adopt a distributed approach to Broadband Remote Access Server (B-RAS) or subscriber management functionality. 

    

   “Many operators have a big B-RAS in the middle of their metro network,” explains Howard. “With all of video traffic growing, that one B-RAS is probably going to break.”

    

   As Howard notes, “Distributed B-RAS uses an edge router with subscriber management in it. No one is building a B-RAS any more. It’s a function on an edge router. Where a carrier has three or four DSLAMs in a central office, they will move a B-RAS there and they’re also looking at putting a cache there.”

    

   Essentially, he says, this creates a telco content distribution network—and it requires an IP address and being part of an IP network.

    

   It’s important to note, though, that some operators see MPLS-TP adding little value but significant complexity in the access network. As Howard says, a carrier focused on providing Ethernet services to the business market may prefer a pure Ethernet approach to the access network.

    

   At the core of the network, however, there is more widespread acceptance of MPLS as a transport protocol. But in that role MPLS has an important limitation. As Howard explains, MPLS relies on the LDP protocol to establish circuits and “if you want to go from a router to optical gear, LDP won’t do that—LDP only knows how to talk to routers.”

    

   MPLS-TP on the other hand, enables service providers to build a circuit from any place to any place, Howard says. “The model is the same as it was with T-1,” he explains. “On TDM, you would have a T-1 go from San Francisco to New York and it would get bundled into SONET and go across on the optical network and come out as a T-1 in New York. MPLS-TP allows the same capability, but it’s more flexible because it runs on packet networks.”

    

   MPLS-TP is sometimes viewed as a rival technology to Provider Backbone Bridge Traffic Engineering (PBB-TE), which aims to provide some of the same functionality in the Ethernet domain—and in the aggregation network, Howard says, PBB-TE largely achieves that goal, making it potentially attractive to carriers relying on Ethernet in the access network. But he says, “PBB-TE was just for access, not to go across an MPLS core—it’s just designed for aggregation and access.”

    

   Equipment supporting MPLS-TP is already on the market or under development from numerous optical and router vendors. But quite a lot of carriers seem to be taking a “wait and see” approach to the technology. Only one-third of network operators in an Infonetics survey conducted this year said they planned to implement MPLS-TP this year or next.

    

   Overture Networks, a Carrier Ethernet solutions provider, reports that its customers are seriously considering MPLS-TP in their access networks, according to Mark McDonald, vice president of product management for Overture. “Our customers see value in MPLS-TP for end-to-end provisioning and performance management.”

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