Framework for EVPN Designated Forwarder Election Extensibility
Nokia
Cisco
Cisco
Juniper
Nokia
Nokia
The Designated Forwarder (DF) in EVPN networks is the PE responsible for sending broadcast, unknown unicast and multicast (BUM) traffic to a multi-homed CE, on a given VLAN on a particular Ethernet Segment (ES). The DF is selected out of a list of candidate PEs that advertise the same Ethernet Segment Identifier (ESI) to the EVPN network. By default, EVPN uses a DF Election algorithm referred to as "Service Carving" and it is based on a modulus function (V mod N) that takes the number of PEs in the ES (N) and the VLAN value (V) as input. This default DF Election algorithm has some inefficiencies that this document addresses by defining a new DF Election algorithm and a capability to influence the DF Election result for a VLAN, depending on the state of the associated Attachment Circuit (AC). In addition, this document creates a registry with IANA, for future DF Election Algorithms and Capabilities. It also presents a formal definition and clarification of the DF Election Finite State Machine.