MPLS Fast Reroute Gains Momentum
Riverstone is joining big names like Cisco Systems Inc. (Nasdaq: CSCO), Juniper Networks Inc. (Nasdaq: JNPR), and Avici Systems Inc. (Nasdaq: AVCI; Frankfurt: BVC7) that have also announced support. Cisco and Avici even demonstrated interoperability last month at Isocore, which runs an independent internetworking lab in McLean, Va.
Even though all these vendors are already shipping products with the technology baked into their systems, it has not been officially standardized. This is not surprising, considering that some implementations of MPLS such as RFC 2547, the draft that defines Layer 3 MPLS VPNs, has not been standardized yet either. Riverstone’s announcement, along with the support of the other major routing vendors, shows that the technology is clearly becoming the industry standard for MPLS resiliency with or without the blessing of the Internet Engineering Task Force (IETF).
“Fast Reroute definitely has the most traction in the vendor community and interest from service providers,” says Mark Bieberich, senior analyst at Yankee Group. “Fast Reroute brings service providers closer to the point where they can provide reliability over IP with the same attributes as TDM services like voice."
But Fast Reroute isn’t the only solution being considered by the IETF when it comes to MPLS resiliency, says Bijan Jabbari of Isocore. Protection switching is another proposal on the table. Unlike MPLS Fast Reroute, which detects an outage and simply routes traffic around it within 50 milliseconds, protection switching also identifies the outage and then signals the nodes so that packets are sent along a different path. Protection switching could potentially offer better network scaleability for resiliency.
“The difference is that fast reroute is a local protection, whereas protection switching takes the nodes into consideration,” says Jabbari.
Whether it's protection switching, fast reroute or a combination of both, adding some sort of resiliency to MPLS is important because it is one of the many reasons incumbent carriers have not deployed MPLS in a big way yet. They are afraid of losing the benefits of Sonet protection, which restores connectivity within 50 milliseconds. The problem with MPLS is that basic IP mechanisms can take several seconds to discover an outage, find an alternative path, and begin rerouting traffic. Fast Reroute supposedly can restore a link within 50 to 60 milliseconds.
But Fast Reroute is not without its problems. Some experts argue that for a large network, it’s difficult to scale and deploy a network based on it. Why? Fast Reroute requires alternate paths to be predefined so that when an outage occurs, traffic can switch over to another MPLS path. Last week, Cisco announced a tool that would automatically calculate these paths (see MPLS Fast Reroute Gets a Boost).
Fast Reroute will likely be a hot topic of discussion at this year’s MPLS 2002 conference in Washington, D.C., October 27 to 29th.
— Marguerite Reardon, Senior Editor, Light Reading
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