Although IP packets flow end-to-end, an IP network is made up terminals and routers and links between them. These links need to be engineered and sized to meet the expected demand.
Originally Ethernet was a transport protocol for linking computers, servers, printers and routers that make up Local Area Networks (LANs). However the technology can be used to form wide area networks connecting LANS together. We've been delivering Ethernet services to customers for almost twenty years and offer a full range of services today. They include BT GigeStream - a low cost, point-to-point Ethernet private circuit service available nationally at speeds of between 250Mbit/s and 1Gbit/s - and BT EVLAN, a VPLS-based metro any-to-any Ethernet LAN service.
Ethernet's ubiquity, simplicity and low cost make it attractive for the links between the nodes in BT's 21CN. As a first step, the backhaul links between the MSANs and the metro nodes will be Ethernet-based. Arguably Ethernet today does not have all the characteristics to make it a general purpose link layer protocol. Currently BT is working with equipment suppliers and standards bodies to ensure it is. BT believes that truly carrier class Ethernet needs to be able to offer the same level of security and resilience, and the same end-to-end fault and performance monitoring, simple and quick error location and remote configuration, as traditional telecoms technologies offer. In 21CN, Ethernet has to be able to offer these characteristics across multi-vendor environments.
When BT completes the development of 21CN, it will represent one of the largest installations of Ethernet in any carrier's network, anywhere in the world.