Ethernet Virtual Connection (EVC) is a Cisco carrier Ethernet equipment function dedicated to service providers and large enterprises. It provides a fine granularity to select and treat the inbound workflows known as service instances, under the same or different ports, based on flexible frame matching.
Ethernet Virtual Connection
One of benefits of EVC is the ability to address independent Ethernet encapsulation on the same physical interface with a mix of different services such as dot1q trunk, dot1q tunneling, EoMPLS Xconnect, VPLS attachment circuit, routing, and Integrated Routing and Bridging (IRB). Each service instance can match a unique identifier or a range of identifiers (i.e. a VLAN tag deployed mainly in the context of DCI).
Another important feature is the ability to aggregate multiple service instances into the same transport virtual instance. For example, EVC can multiplex multiple VLANs into the same Bridge Domain (BD) connected to a Virtual Forwarding Instance (VFI) of a VPLS.
Multiplexing Multiple VLANS
Another important element for a multi-tenancy environment is the ability for each service instance to change the VLAN tag using a new identifier, which allows dynamic VLAN ID translation.
In addition, the flexibility of the service mapping of EVC allows improving the scalability in terms of service instances, VLAN per Bridge Domain or per EoMPLS Xconnect or per VFI.
Under the same or different physical interface, multiple service instances can be mapped into the same bridge-domain to provide L2 local bridging between physical interfaces and leverage the usage of VPLS to bridge L2 frames across the MPLS core.
If we leverage the concept of EVC in the public cloud context, a customer service is an EVC. This EVC is identified by the encapsulation of the customer VLANs within an Ethernet island or Bridge Domain, and is identified by a globally unique service ID. A customer service can be point-to-point or multipoint-to-multipoint.
The next drawing shows two customer services: Service Green is point to point; Service Red is multipoint to multipoint.
