Carrier Ethernet Transport for Wholesale Services

Consider the challenges facing today’s carriers’ carrier. Ethernet services continue to grow in popularity, and are expected to reach $22.5 billion in revenue by 2009. In particular, gigabit Ethernet is becoming the predominant transport bearer, thanks in part to rising broadband access rates and its widespread adoption by devices such as IP DSLAMs, MSANs and WiMAX base stations. In an overwhelmingly competitive environment, carriers’ carriers must deliver end-to-end GigEs, while guaranteeing them with SLAs, as a table stakes requirement to successfully win business.

This capability has not been feasible in the past due to limitations in various technologies. Pure Ethernet offers the best economics for such services, thanks to the volume of Ethernet deployment in the market as a whole. However, Ethernet has suffered from a lack of end-to-end OAM and certain LAN-oriented characteristics of the protocol, making it undesirable for use in a carrier backbone network. Pure MPLS solutions also have struggled to adequately address the needs of large volumes of GigE services for carriers’ carriers on several fronts. MPLS solutions have focused on the use of “dumb” point-to-point optical connections between MPLS routers, resulting in many issues:

• The lack of integration between the optical layer and MPLS layer breaks up the service into segments, losing end-to-end OAM visibility and greatly complicating SLAs.
• The use of MPLS routers right to the edge of the network is expensive.
• MPLS is difficult to scale for large numbers of tunnels, especially in terms of provisioning complexity.
• It is inefficient to process full-rate GigEs through packet-based MPLS routers, wasting precious MPLS processor resources, when they can be transported at the optical layer much more efficiently and less expensively.

The introduction of Ethernet tunnel technologies such as provider backbone transport (PBT) and transport MPLS (T-MPLS) addresses these issues. Ethernet tunnels overcome the OAM limitations of Ethernet’s past by enabling connection-oriented Ethernet. A new architectural approach, carrier Ethernet transport (CET), has emerged that combines Ethernet tunnel switching, sub-wavelength switching and wavelength switching into a single WDM platform. By adding “just enough” Layer 2 processing to the optical domain, CET provides carriers’ carriers with three key advantages: fast provisioning times, reliability and scalability.

Fast Provisioning Times
The wholesale market is highly competitive, and provisioning new services faster than the competition is a metric that can make the difference between a satisfied customer and lost business. One of the cornerstones of CET is that it embraces a true networking approach through its embedded switching capability. CET platforms can switch at three levels of granularity: wavelength, sub-wavelength and Ethernet tunnels. The advantage of a switched architecture is that Ethernet path/connections can be aggregated and switched using the embedded software in the node, rather than costly, time-consuming manual switching with patch cords. As a result, deploying new services can be done entirely with software controls, helping to minimize truck rolls and greatly reducing travel, planning, provisioning and verification timelines.

A recent study compared the operational requirements for maintaining a network without a switched architecture (using patch cords) versus maintaining a network with a switched architecture. In the patch cord model, the aggregate time required to add a new service (including traveling to sites, planning, installing cards, provisioning services and verifying the service) was calculated to be 7.5 hours per site. By comparison, the aggregate time required to add a new service using the switched architecture model was determined to be less than one hour. From an operational prospective, CET helps ensure new services can be added, transitioned and, if applicable, re-allocated in a matter of hours rather than weeks.

Reliability
“Connection-orientated” Ethernet tunnels enable performance monitoring and management of the entire Ethernet path/connection across the entire network. By delivering end-to-end “connection-orientated” Ethernet paths/connections that are switched within the optical transport network, CET ensures the Ethernet paths/connections achieve low jitter, low latency and deterministic QoS. This makes it possible to guarantee the end-to-end service with SLAs from within the optical transport network infrastructure to support the SLA-assured wholesale services. Previous packet-layer-only solutions (e.g. using L2 switches) often meant that there was a loss of end-to-end path/connection visibility at the infrastructure level, which compromised or added complexity to guaranteed SLAs.

Scalability
As bandwidth demands continue to increase, carriers’ carriers must find new ways to scale their networks efficiently while still meeting ROI standards. Using WDM and the optical layer provides an unlimited platform for delivering high-bandwidth services.

One advantage of the architectural approach provided by CET is that there is a clear delineation between the service layer and the transport layer. As a result, each layer can scale separately, as there is no fixed correlation of service platforms/service layer to the underlying network infrastructure topology, ensuring that the carriers’ carriers can focus on the delivery of the service rather than on the underlying transport network.

Carrier Ethernet Transport Architecture

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This architectural diagram of carrier Ethernet transport shows the optical layer comprised of switching elements, which ensures end-to-end connection-oriented Ethernet paths, which can be provisioned remotely and rapidly, as well as guaranteed with SLAs. There is a clear separation between the service layer and transport layer to provide scalability.

In summary, the network switching capabilities (wavelength, sub-wavelength, Ethernet tunnels) ensure that Ethernet paths/connections can be switched ubiquitously across the optical transport network, with a range of Ethernet interconnect bandwidths, using a common service facilitation methodology.

“Connection-orientated” Ethernet provides the required end-to-end OAM of the Ethernet paths/connections across the entire network. This makes it possible to guarantee the end-to-end service with SLAs from within the optical transport network infrastructure, while minimizing the requirement to go back to client interfaces as the Ethernet path/connection traverses the network.

CET provides a scalable, reliable, converged optical WDM NGN transport infrastructure whose capabilities are ideal for carriers’ carriers.

Ken Davison is vice president of marketing and business development with Meriton Networks. He can be reached at ken.davison@meriton.com.

Meriton Networks www.meriton.com

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