Carrier Ethernet boldly goes where no MPLS network has gone before

Multiprotocol label switching (MPLS) has become popular among carriers looking to converge numerous network streams onto a single backbone. But some people, including engineers at Nortel Networks, argue that MPLS isn't all it's cracked up to be. They say a new technology - Carrier Ethernet - provides a simpler, more effective solution when it comes to the metro area network. Is MPLS about to lose its crown?MPLS is at the core of most service provider networks and the carriers want to utilize those assets fully, according to John Beatty, a Boston MA-based senior product marketing manager at Nortel. The next logical step was extending the MPLS core out into the metro, but the service providers started running into a challenge, he said: stretching the MPLS hub to reach the metro introduced scalability issues and operational complexity. MPLS cores already have hundreds of nodes. When the cores are extended out into the metro, the node-count increases by an order of a magnitude, Beatty said. This leaves service providers having to manage thousands of nodes. Carrier Ethernet, on the other hand, makes quick work of node management, Beatty said.The QoS questionIn order to ensure quality of service (QoS), service providers need to know which customers are getting what traffic, when. "A service provider wants to provide bandwidth in a deterministic fashion," Beatty said, meaning carriers like to be able to predict traffic loads and flows. "That's where PBT (provider backbone transport) comes in. You know the path the traffic is going to flow."PBT and provider backbone bridging (PBB or 802.1ah) for inter-carrier connections are native Carrier Ethernet almost-standards that allow organizations to set up point-to-point Ethernet tunnels across the metro. The tunnels reserve bandwidth over a native carrier-class Ethernet connection, allowing companies to transport data, voice and video while guaranteeing QoS. In contrast, MPLS devices would have to do the work to set up the path, Beatty said, adding that the extra hardware is no fun to run."MPLS is theoretically scalable, but routers are more expensive," he said. They also require more processing and need more memory, driving up costs. "You're creating this mesh of networks all over your metro."Carrier Ethernet paths are manually provisioned by the network operations centre. Though this sounds labour intensive, Beatty said Nortel's service provider customers aren't concerned. "They'd manually go out and provision the paths over these switches. When we've discussed this with customers, this has not been an issue thus far." Management tools can help ease the impact, he said. "Even with the MPLS network, there's still a degree of provisioning that would need to be done on the network. Customers give very little objection or push back to that."However, MPLS services can ride over Carrier Ethernet tunnels, allowing service providers to fully utilize the core they've invested so much money into, Beatty said. "Nortel would be crazy to say, ‘Rip out your MPLS core.' That's not what we're saying. We propose PBT as an alternative to MPLS, but specifically for the metro."Industries located in the suburbs could benefit from the massive amounts of bandwidth provided by Carrier Ethernet networks, said Roberta Fox, a senior partner at Fox Group Telecom Consulting in Mount Albert ON.The health, entertainment and media, and manufacturing sectors - which all need to transfer large amounts of data and images - need lots of bandwidth, but they're often located in the suburbs. "If Carrier Ethernet is extended out where the need is, then it can be viable," she said. "My concern is if we can't get it to the points that need it, then the business case is questionable." However, the last mile could be wireless. "You don't have the Ethernet go right to the door," Fox said. "That's the part that makes it interesting."MPLS and Carrier Ethernet complement and compete with each other, Fox said. MPLS is like a spider web whereas Carrier Ethernet runs point-to-point. You could use multiple paths to get from one point to another with MPLS and run different protocols on it, but it might not always be the most efficient choice. In some cases, Carrier Ethernet's more direct approach is the right answer.Olaf Krahmer, VP of service providers for Cisco Canada in Toronto, said he believes MPLS and Carrier Ethernet play different roles. The technologies do different things: Carrier Ethernet is a service and MPLS, like asynchronous transfer mode (ATM), is an enabling technology, not sold as a service.Logical MPLS extensionCarrier Ethernet is the logical extension of the current core king. "MPLS is the most predominant technology in the backbone which enables a number of services such as Carrier Ethernet," Krahmer said.Marty Hess, director of marketing at Spokane Valley WA-based World Wide Packets Inc. - a Carrier Ethernet equipment vendor - agreed that Carrier Ethernet and MPLS complement each other. "Does Carrier Ethernet feed into the MPLS cloud? The answer is yes. It's too expensive to put a router out in every corner," he said. "The question is where does the handoff occur in the provider edge to the MPLS cloud?" There are customers who need a complete MPLS solution and those who just want a pipe - a PBB solution. The PBB aspect of Carrier Ethernet is very close to becoming a full-fledged standard, said Nortel's Beatty. It only has to go through a final vote. He predicted that the technology would become a standard sometime this year. PBT was introduced as a project last month and received its very own IEEE number: 802.1Qay. It also received a long title: provider backbone bridging-traffic engineering (PBB-TE).

Carrier Ethernet boldly goes where no MPLS network has gone before

News | April 5, 2007

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