A typical service provider Metro Ethernet network

A typical service provider Metro Ethernet network is a collection of Layer 2 or/and Layer 3 switches or/and routers connected through optical fiber. The topology could be a ring, hub-and-spoke (star), or full or partial mesh.

The network will also have a hierarchy: core, distribution (aggregation) and access. The core in most cases is an existing IP/MPLS backbone, but may migrate to newer forms of Ethernet Transport in the form of 10Gbit/s, 40Gbit/s or 100Gbit/s speeds.

Ethernet on the MAN can be used as pure Ethernet, Ethernet over SDH, Ethernet over MPLS or Ethernet over DWDM. Pure Ethernet-based deployments are cheap but less reliable and scalable, and thus are usually limited to small scale or experimental deployments. SDH-based deployments are useful when there is an existing SDH infrastructure already in place, its main shortcoming being the loss of flexibility in bandwidth management due to the rigid hierarchy imposed by the SDH network. MPLS based deployments are costly but highly reliable and scalable, and are typically used by large service providers.

December 16, 2011

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