The service at the customer boundary
A subscriber hands Ethernet frames to the provider at a User Network Interface (UNI). An Ethernet Virtual Connection (EVC) defines the service endpoints and which endpoints can exchange service frames. The provider can build that connectivity over its own network topology.
A port-based service identifies the service from the handoff rather than the customer VLAN ID. A VLAN-based handoff can use customer VLAN tags to distinguish multiple services on one UNI.
E-Line, E-LAN and E-Tree
E-Line connects two endpoints in a point-to-point service. E-LAN gives all endpoints multipoint connectivity to one another. E-Tree assigns endpoints root or leaf roles. A root can exchange frames with roots and leaves, while a leaf can exchange frames only with roots.
For example, a chain of shops can use E-Tree to reach its headquarters while keeping the shop handoffs isolated from one another. The restriction applies to forwarding inside the Ethernet service. A router at headquarters could still route traffic between shops if configured to do so.
Try it in a lab
- On a lab platform that supports E-Tree, configure a headquarters endpoint as a root and two branch endpoints as leaves. Use hosts in the same IP subnet with no gateway to test the Ethernet service itself.
- Confirm each leaf can reach the root and the root can reach both leaves. Then test traffic directly between the two leaves and confirm it cannot traverse the service.
- Repeat the leaf-to-leaf test with the endpoints in an E-LAN. Expect it to pass if the same endpoint addressing and handoffs are in place.