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LAN Services to Get New Look

Posted on: Thursday, 16 September 2004, 06:00 CDT

Major service providers could begin offering high-bandwidth, low- cost Virtual Private LAN Services next year if the proposed standard for the Ethernet/Multiprotocol Label Switching-based technology is approved by yearend as expected.

Major U.S. carriers including AT&T and MCl are kicking the tires on VPLS - a LAN extension service that supports service-level agreements (SLA) and QoS for individual applications (see story page 59).

AT&T says it is premature to comment in detail but confirms that the company is working on a service, adding that there is no timetable for deployment. MCI says it is looking at a variety of Layer 2 technologies it could add to its existing IP VPN services, including VPLS. Verizon already offers an Ethernet service that runs over its MPLS core network, but it is not based on VPLS. However, Verizon has successfully trialed VPLS in its lab and could offer services based on it within 10 to 24 months, a spokesman says. SBC offers point-to-point Ethernet services now, but by adopting VPLS it also plans to offer point-to-multipoint. Other carriers such as Time Warner already offer VPLS services, and Pennsylvania provider TelCove says it plans to offer them soon.

Why VPLS?

VPLS is in the final stages of review by the IETE and once it is approved, equipment vendors such as Alcatel, Cisco, Extreme Networks, Foundry Networks and Riverstone Networks that have already produced VPLS gear based on drafts of the standard can work toward interoperability This is important to carriers that don't want to be locked into buying equipment from a single vendor. Approval is anticipated by early next year at the latest, says Marc Lasserre, co- author of the VPLS proposal and chief scientist for Riverstone.

Once the standard is in place, service providers would consider the technology more seriously as a solid base on which to build new services, says Mark Bieberich, an analyst with The Yankee Group. "You will see some of these Tier 1 service providers commit to VPLS offerings within six to 12 months," he says.

Meanwhile, two smaller U.S. carriers already offer VPLS services, Masergy in Dallas and Sure West in Roseville, Calif. These companies have the advantage of not having existing data service offerings that VPLS would compete against,says Erin Dunn, an analyst with Vertical Systems Group. VPLS doesn't cut into their existing accounts and doesn't require phasing out other technologies such as TDM, frame relay and ATM.

Another drawback for carriers is that the service requires Ethernet connections from customer sites to carrier points of presence, and Ethernet is far from universally available. "The likelihood of finding a service provider with Ethernet access everywhere you need it is unlikely? Dunn says.

Part of the problem is that high-bandwidth Ethernet access requires fiber, and that resource is available mostly in cities. Masergy expands its service area by using devices that carry Ethernet over copper wires instead. Tasman Networks' gear presents customers with two Ethernet ports and can plug into a T-1 or T-3 on the WAN side, running Ethernet over the wire via point-to-point protocol, says Jim Brunetti, Masergy's director of engineering.

Because copper has a slower top speed, using it limits the top speed of Ethernet services that can run over it. On fiber, speeds can reach IG bit/sec.

Coming attractions

One of the major attractions of VPLS-based services is that they cost less for more bandwidth than other transport services. For example, a customer upgrading a T-I frame relay network to a 1OM bit/ sec Ethernet service would get nearly seven times the bandwidth for just double the price, says David Parks of The Yankee Group.

It's possible to offer VPLS-like services using Ethernet access and MPLS backbones without actually using VPLS. For example, Verizon offers Transparent LAN Service (TLS), which can create multipoint- to-multipoint LANs in metropolitan networks, but not between metropolitan networks, says Vin Alesi, a distinguished member of technical staff for the carrier's data services architecture group. TLS can unite two or more metropolitan Ethernet LANs via a point-to- point link, but they remain separate islands and do not afford truly meshed connections, he says. Traffic can get between the islands but not be directly routed to individual machines. VPLS would enable this LAN emulation across wide areas, not just metropolitan regions, Alesi says.

Beyond supporting fully meshed networks.VPLS eliminates the need for customers to share Layer 3 routing information with their carriers, which can be a headache or could violate corporate policy With MPLS VPNs, for instance, customers must route their traffic into their providers' networks and deal with advanced routing protocols such as Border Gateway Protocol.

With VPLS, they deal with the services as if it were part of their Ethernet network. The demarcation point can be an Ethernet switch rather than a router.

Bigger site support

Another plus is that VPLS makes it possible to support very large numbers of sites. As demand for Ethernet services grows, the underlying Ethernet mechanisms for separating traffic become limited by the number of VLANs a network can support, about 4,000. VPLS defines the means to extend that number into the millions, which makes it likely that more carriers will support VPLS as Ethernet services grow in popularity.

Ethernet services in the U.S. generated less than $500 million in carrier revenue this year, and VPLS is an insignificant amount of that sum, says Dunn, but she projects that Ethernet services revenue will grow to $1.3 billion by 2007. This includes point-to-point and metropolitan Ethernet services from SBC, Verizon and BellSouth.

VPLS also can offer separate service quality to different applications, which would be key to running VoIP on these networks, Parks says. And VPLS gives carriers controls to offer strong SLAs.

As carriers consider VPLS, they are looking for a way to make it compatible with other Layer 2 access technologies such as ATM and frame relay with Ethernet access, Parks says. That means one site could be connected to the MPLS network via frame relay, another via Ethernet and a third via ATM, and all three sites could connect with the others over an MPLS backbone. This would let carriers that already have frame relay and ATM customers migrate them gradually rather than forcing a change to Ethernet at all their sites. SBC says it wants to offer such services and has the means to do so using Cisco switches.

Even when all the bugs are worked out of VPLS, the popularity of other new technologies such as IPVPNs could hold back VPLS."I don't think VPLS will ever achieve the status of frame relay," Parks says.

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Senior Editor Denise Pappalardo contributed to this story.

Copyright Network World Inc. Sep 6, 2004

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