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Three optical and IP network architectures enable converged backbone

Merging IP and optical networks to create a "converged backbone" can be done using three network architecture models that start with IP-over-WDM and move on to port-level grooming and finally subport-level grooming, all of which are addressed byu Alcatel-Lucent solutions.

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To meet telecom operators' strategic initiatives and maximize network efficiencies, three architectural deployment models can address the converged backbone: lambda-level grooming, port-level grooming, and subport level grooming.

  1. Lambda-level grooming: This is most often known as the IP-over-WDM option, deployed today by operators that have already separated the router and transport groups to achieve low-cost options by integrating optical transponders into the router. This allows the router to generate the wavelength (lambda) rather than the transport equipment, reducing the number of transponders required in the network, thus lowering the cost per bit.

    With this method, there is no grooming within or below the lambda level, and although beneficial, it is the simplest approach to a short-distance, lower-cost transmission option. It can fall short when addressing long-haul or ultra-long-haul distances that require additional compensation to the transmit and receive transponders. This option is ideal for high volumes of hub-and-spoke traffic, where the traffic is largely homed onto a small number of routers for peering and content distribution.


  3. Port-level grooming: Conventional transmission connects the IP router with the optical platform, improving efficiencies, but traffic can be groomed at the router port onto higher speed optics for long distance transport. Port-level grooming maximizes wavelength utilization on high speed pipes because the traffic is already groomed at the port to fill the wavelength efficiently. Port-level grooming is best suited for network traffic that carries a mix of services and service delivery types. It does not interfere with the traditional management boundaries, so the separate networking groups can remain separate.

  5. Subport-level grooming:
  6. This is the highest form of flexibility, which provides increased granularity by enabling VLANs or pseudowires within a port to be logically or virtually mapped to an optical wavelength at rates as granular as 1 Gbps. This works by mapping individual VLANs in a port to different virtual containers and potentially to different outgoing ports, by using ODUflex and VLAN shaping.

    Previously, operators had to allocate all of the content of an incoming port to a virtual container in an outgoing port. This model optimizeds the network without affecting the internal operational segments of the staff. A key aspect of subport-level grooming is that it optimizes networks where the topology of traffic is more along the lines of any- to- any, like a Layer 2 network with a high volume of VLANs or pseudowires supporting business services, but it also supports hub-and-spoke traffic such as Internet access.

Alcatel-Lucent's router and optical platform solutions

The Alcatel-Lucent service routers and optical platforms incorporate support for tunable optics to deliver lambda-level grooming, port-level grooming, and subport-level grooming. In addition to these options, control plane integration assists in fault isolation and overall network resiliency. Integrated management also enhances visibility across the IP and optical domains while facilitating ease of provisioning.

Future outlook for the converged backbone

Optical platforms are optimized for high-bit-rate, circuit-oriented transmission, while IP platforms are optimized for packet traffic. We have discussed various strategies and models of deployment to assist in the integration and optimization of the IP and optical domains. These methods will also assist in offloading sites in core networks today, which do not need to be routing transit traffic.

Today's core routing infrastructure handles packet processing for a percentage of transit IP traffic, some of which ultimately could be offloaded to the lower transport layers. This reduces the strain on core routing sites, liberating ports that could be repurposed for revenue-generating traffic and Internet peering. It also offers an opportunity to lower cost in the core backbone and leverage the high-speed optical network. Alcatel-Lucent is on the right path in bringing these architectural options to market to address these issues.

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About the author: Eve Griliches is a program director in the IDC telecommunications equipment group. She provides in-depth insight and analysis on service provider routers and switches, as well as the optical networking market. Griliches also provides critical business intelligence on emerging technology trends and their impact on the overall telecom market space.


This was last published in September 2009

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