Hardware developers familiar with the history of Ethernet in the enterprise may find themselves overwhelmed by the service diversity and complexity which must be addressed in applications for the local exchange carrier, long-haul or inter-exchange provider, and wireless operator. Analyze service complexity in a common Ethernet infrastructure article tasks Ethernet is called upon to perform in telecommunications operator environment seem almost unbelievably complex.
Network aggregation points must handle constantly changing mixes of voice, video, and data, requiring a steady packet-transport service along with circuit emulation and fault-tolerant protection switching. These diverse services would need to be supported regardless of the transport protocol, or regardless of whether carriers had switched to an all-packet infrastructure. The reason that those different services needs to be supported is that they are widely used (many telecommunications system rely on them) and they are core business for the operators (where the money comes in).
Read also Metro Ethernet article from Wikipedia and Explaining Where Ethernet Fits Into the Mobile Operator’sNetwork Evolution Plans slide set.