CEWC Key Theme Viewpoint – Automation in the Packet World

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  1. Avatar Kevin Oemering 10/09/2009 @ 11:28 am

    Do the panel see the inclusion of photonic switches in the network to provide provisioning and restoration capabilities rather that using o-e-o at each point of flexibility?

    • Avatar John-Paul Hemingway 10/09/2009 @ 11:42 am

      Thanks for the question, Kevin. The short answer is yes, the evolution will occur from OEO to photonic switching within intelligently switched networks. From our perspective, the technology is available, but at a system level the business case is weak compared with todays OEO systems. Some operators have considered Packet Optical + ROADM to offer a similar capability, but discovered quickly that without a complete control plane, it does not scale terribly well, and software to manage it is not well understood. I guess thats a long way of saying intelligent photonic switched is the future, but my guess is that the market for such is still very immature.

  2. Avatar James Middleton 10/09/2009 @ 11:37 am

    Hi John-Paul, I’m wondering why we need OTN as part of the control plane? Isn’t SDH and Ethernet enough?

    • Avatar John-Paul Hemingway 10/09/2009 @ 12:03 pm

      The issue is that optical services are no longer just SDH & Ethernet, it spans even more enterprise optical services, including Ethernet, Storage and Video services. Part of the reason most new Metro Deployments are OTN based, is that it allows the services mix to to carry ANY optical service, while still supporting Ethernet and SDH with better management capability. One quick example is the fact that Ethernet over SDH restricts the max speed of Ethernet to 9.9 Gbps. With most new Ethernet interfaces using the 10G LAN PHY at 10.3 Gbps, services are forced to slow down something OTN carries transparently. There is more information on OTN here if you’re interested:

  3. Avatar Mike 10/09/2009 @ 11:50 am

    Can the panel explain what is the difference between a router based mesh network and an optical mesh? Don’t they do the same thing?

    • Avatar John-Paul Hemingway 10/09/2009 @ 1:12 pm

      Router based Mesh networks are fundamentally different because of the OSI layer they operate in. Routers operate in Layer 3 (IP) and utilize a Layer 3 control plane that determines how traffic gets from point A to Point B (across the mesh) utilizing various routing protocols including OSPF, ISIS, BGP, etc. It only looks at layer 3 issues, with the drawback being the amount of time it takes for the control plane to respond to network changes (including outages). In some cases it could take as long as 15 minutes for a router to respond to a single failure. MPLS has helped routers reduce restoration time by creating connection orientation and creating a Fast Reroute path in the event of equipment failure, giving it faster response time to link failures (not node failures). So even though a Router networks typically always operate in a MESH configuration, it doesn’t offer the full advantages of reliability of the mesh architecture.

      Optical Mesh networks, by contrast, operate at Layer 0/1 and utilize optical signalling protocols that carry network routing information across the mesh, but offer the advantage of restoration in 50ms or less, even in a multi-failure scenario.

      So in essence, the construct is the same, but they operate at different layers.

      I will add one thing, while they do different things, it is important to note that in addition to better reliability, the optical (Layer 0/1) MESH is cheaper to own and operate than a layer 3 Router mesh.

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