An Ethernet virtual circuit (EVC) as defined by the Metro Ethernet Forum is a port-level point-to-point or multipoint-to-multipoint
Layer 2 circuit. It is an end-to-end representation of a single instance of a Layer 2 service being offered by a provider
to a customer. An EVC contains the different parameters on which the service is being offered. A service instance is the instantiation
of an EVC on a specified port.
Service instances are configured under a port channel. The traffic carried by the service instance is load balanced across
member links. Service instances under a port channel are grouped and each group is associated with one member link. Ingress
traffic for a single EVC can arrive on any member of the bundle. All egress traffic for a service instance uses only one of
the member links. Load balancing is achieved by grouping service instances and assigning them to a member link.
Ethernet virtual connection services (EVCS) uses the EVCs and service instances to provide Layer 2 switched Ethernet services.
EVC status can be used by a customer edge (CE) device either to find an alternative path to the service provider network or
in some cases, to fall back to a backup path over Ethernet or over another alternative service such as ATM.
For information about the Metro Ethernet Forum standards, see the Standards table in the “Additional References” section.