Connection-oriented Ethernet - Achieving The Promise of Carrier-grade Ethernet

Achieving The Promise of Carrier-grade Ethernet

Services in the data network are typically classified into 2 major categories: Committed Information Rate (CIR) and Excess Information Rate (EIR). A CIR service guarantees its user a fixed amount of bandwidth, whereas an EIR service offers best-effort only transport. Both types of services share a single capacity-constrained infrastructure. Both are further defined by additional parameters.

A carrier's return on investment is directly related to its ability to transport more service instances over a fixed capacity-constrained infrastructure, keeping Quality of Service high. It is further associated with its ability to offer a broad range of added-value services, such as IPTV, Voice, and VPN, whose requirements can widely vary and pose technical difficulties when sharing the same infrastructure.

With the above in mind, the carrier's objective is to offer a maximum amount of best-effort EIR services over its network while reliably serving its committed CIR services. To achieve this PBB/PBT and T-MPLS approaches largely under-provision network resources, in order to avoid a situation where a burst in best-effort traffic would jeopardize the ability to serve committed traffic, leading to costly penalties. An additional issue with best-effort access on data networks is fair allocation among clients. With PBB/PBT and T-MPLS, the amount of bandwidth available to a particular client greatly depends on the client's location and the prevailing traffic conditions. This limits the value customers attach to EIR services and undercuts carriers' opportunities to offer differentiated access to its excess capacity.

Performing traffic engineering in real-time is thus key to next-generation Ethernet transport. Additional qualities are required to make Ethernet a carrier-grade technology:

• Rich OAM: capacity optimization, path calculation and configuration, iterative optimization.
• Path protection: sub-50ms failover.
• Support for next-generation services: efficient provisioning of point-to-multipoint and multipoint-to-multipoint services.

Multi-vendor support, the ability to support a variety of Ethernet switches in the core, is a desirable attribute as it allows carriers to use inexpensive switches to build their metro transport network. Vendors such as Tejas Networks, Ethos Networks, and Nortel offer solutions which meet the above requirements, yet preserve Ethernet's simplicity and flexibility.