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IP over DWDM (IPoDWDM)

Service Providers continue to look for the best economics for increasing network capacity to accommodate the continued growth in IP traffic driven by data, voice and primarily video traffic. The advantages of integration have already been witnessed at the transport layers through the integration of SONET/SDH and DWDM. This integration was realized in the form of native DWDM interfaces on SONET/SDH Add Drop Multiplexers (ADMs), cross connects and common management systems. Why IPoDWDM?The reason for integrating IP and DWDM are simply to deliver a significant reduction in capital expenditures and improve the operational efficiency of the network. The premise of IPoDWDM is to reduce the electrical transport layer as much as possible as this provides the highest bit-rate robustness, future protocol robustness and functional robustness. For example, moving an underlying SONET/SDH infrastructure from 10G to 40G requires significant redesign but using some novel modulation formats, accommodating 40G over existing 10G transmission infrastructure is possible. Additionally, modifying an electrical cross-connect from 10G SONET/SDH to Ethernet is not a simple task. Lastly, integration of the IP and DWDM layers can improve the overall reliability of the network by creating visibility of the optical layer into the IP layer enabling faster protection at Layer 3 instead of leaving un-used bandwidth in the network for protection as with SONET/SDH.What makes this possible?Given several advancements, the time has come for a level of integration between IP and DWDM elements to enable service providers to deploy cost effective, scalable networks. These include, but are not limited to:

  • Development of terabit capacity routers capable of supporting tens of gigabits per second interfaces on a single line card
  • Integration and form factor reduction of transponder technologies
  • G.709 or Digital Wrapper function for providing a framing function for monitoring, error correction etc.
  • Fast Re-Route (FRR) technology for MPLS and IP

The ApproachIntegrating IP and DWDM requires a much broader approach that must include:

  • Element Integration: integration of DWDM interfaces in core routers as well as integration of photonic switching into the DWDM layer, allowing bypassing of transit points optically when there’s no need of layer 3 processing
  • Management Integration: integration of management functions from both the IP and DWDM layer into a single streamlined solution -- still allowing different users to have views based on the role
  • Control Integration: integrating control plane functions building on existing standards approach and extending them to the DWDM layer

Cisco believes this technology is going to be all the more necessary as the customers need for more and more bandwidth continues its dramatic rise. As a result, we’ll continue to push innovative approaches of integrating IP and DWDM layers closer together introducing solutions that enable providers to scale their core networks at the best possible economics while providing efficient operations.

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