Framework for Ethernet VPN Designated Forwarder Election Extensibility

An alternative to the Default Designated Forwarder (DF) selection algorithm in Ethernet VPN (EVPN) networks is defined. The DF is the Provider Edge (PE) router responsible for sending broadcast, unknown unicast and multicast (BUM) traffic to multi-homed Customer Equipment (CE) on a particular Ethernet Segment (ES) within a VLAN. In addition, the capability to influence the DF election result for a VLAN based on the state of the associated Attachment Circuit (AC) is specified. This document clarifies the DF Election Finite State Machine in EVPN, therefore it updates the EVPN specification.