Is MPLS alternative DOA?

* Provider Backbone Transport proponents face tough crowd at MPLS conference

Granted, it was an MPLS-immersed conference. And Cisco had its best engineering SWAT team there to exterminate anything that threatened its router franchise.

But this week’s Future-Net conference -- formerly MPLScon -- showed just what a daunting uphill climb MPLS alternatives such as Provider Backbone Transport (PBT) have to gain market momentum.

PBT -- which chief proponent Nortel now calls Provider Backbone Bridging-Traffic Engineering (PBB-TE) and is proposing as an amendment to the IEEE 802.1Q standard -- is an Ethernet derivative intended to bring connection-oriented characteristics and deterministic behavior to Ethernet. PBT turns off Ethernet's Spanning Tree and media access control (MAC) address flooding and learning characteristics to enable Ethernet to behave more like a traditional carrier transport technology.

PBT and PBB-TE are extensions of the IEEE 802.1ah specification Provider Backbone Bridging (PBB), which scales virtual LANs (VLAN) by encapsulating MAC addresses within MAC addresses.

But router vendors such as Cisco assail PBT as a limited niche technology that supports only point-to-point Ethernet applications and lacks the multipoint, multiservice capabilities of MPLS, as well as an integrated control plane.

One of the themes of this year’s Future-Net was “The Great Ethernet Debate,” featuring discussion and presentations on emerging Ethernet transport techniques in the face of a 10-year-old installed base of MPLS switches and routers. Nortel was virtually the lone wolf baying in the hostile wilderness on the benefits of PBT over MPLS and offspring Virtual Private LAN Service (VPLS) for Ethernet transport applications.

Small, privately held edge switch maker Hammerhead Systems tried to show how its HSX 6000 switch could function as a PBT service gateway, but may have done more to complicate the technology than to clarify its role. From a PBT perspective, the conference could have benefited from the presence of advocates Siemens, Avici or Huawei; or BT or Shanghai Telecom, two carriers that are using or plan to use the technology.

The service providers that were here this week never gave PBT a mention during their presentations on MPLS/VPLS features and functions, until prodded to do so during question and answer sessions.

“It seems like PBT in the metro is a step back from what the technology is capable of,” said Keao Caindec, chief marketing officer at Ethernet service provider Yipes Enterprise Services. But Caindec acknowledged Yipes does not face the same issues as a large carrier looking to packetize its SONET access and metro infrastructures.

Verizon does, yet while acknowledging a potential role for PBT in the service edge, it has too much invested and embedded in MPLS and VPLS to carve out a niche for PBT.

“If it is not a large MPLS infrastructure, there might be a simpler role” for PBT, said Stuart Elby, vice president of network architecture for Verizon Business. He did mention, however, that there could be a role for the PBB in the Verizon Business network to perform VLAN scaling.

Perhaps a small consolation for PBT proponents, but Verizon’s position is a glaring example of PBT’s challenge: to get service providers to look askance at 10 years of investment, development, deployment, experience and maturity in MPLS for a traffic engineering alternative for metro Ethernet.

But Ethernet’s been around even longer -- 30 years. That may be why some believe PBB, PBT and MPLS/VPLS could peacefully coexist.

“I don’t think it’s one vs. the other,” said Marc Lasserre, chief scientist at Alcatel-Lucent. “There will be metro access networks running PBB or PBB-TE aggregated into” MPLS/VPLS.

“The main value of PBB is its MAC-in-MAC capability, and (hierarchical) VPLS will make use of it for MAC (address) hiding,” Lasserre added.

One of the chief benefits of PBT is its inherent Ethernet simplicity while MPLS has 10 years of complexity bloat, according to proponents. But Hammerhead did not convince Cisco of this during a presentation on the applications of its HSX 6000 switch as a PBT service gateway capable of interworking with the installed base of MPLS and VPLS edge devices.

“I’m perplexed as to how this is mitigating complexity,” said Cisco Distinguished Consulting Engineer Monique Morrow after the Hammerhead presentation, referring to the switch’s need to support PBT, MPLS and VPLS protocol stacks -- as well as the need for service providers to buy and deploy another switch to connect PBT islands to the MPLS/VPLS edge.

“You have quite a bit of embedded complexity,” Morrow said to Norival Figueira, Hammerhead’s system architect, CTO and Future-Net presenter. “It’s beyond me what you are trying to address in the market.”

Figueira appeared to accept Morrow’s invitation to discuss the matter privately.

Indeed, Cisco engineering sharpshooters seemed omnipresent at the conference, eager to pick off any emerging packet transport alternative pitched as a less expensive, simpler option to MPLS-enabled routers. Cisco Architect Thomas Nadeau’s target was Transport MPLS (T-MPLS), an ITU-T proposal of an apparent MPLS variant designed to bring simplified connection oriented packet switched transport capabilities to next -eneration optical access switches.

“The requirements for T-MPLS can be achieved using existing MPLS and (pseudowire emulation edge-to-edge) technologies,” Nadeau said, while urging vendors and carriers in attendance to prevent the ITU from modifying MPLS or any of its established operations, administration and maintenance practices.

“This gets us further away from what we have today,” Nadeau said.

And in a rare display of Cisco/Juniper cooperation, Nadeau and Juniper Distinguished Engineer Yakov Rekhter -- co-designer of the Border Gateway Protocol and author of some 40 IETF documents on routing and MPLS -- tag teamed to shoot holes into Nortel’s arguments on why PBT should be considered a viable alternative to MPLS for certain metro applications.

“Ethernet is a better fit than MPLS” for Ethernet VLAN awareness and transport, said Don Fedyk, Nortel senior advisor and standards CTO.

But is it too little, too late?

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Copyright © 2007 IDG Communications, Inc.

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