Encoding Multipoint LDP (mLDP) Forwarding Equivalence Classes (FECs) in the NLRI of BGP MCAST-VPN Routes
This RFC 7441 was published in 2015
Many service providers offer "BGP/MPLS IP VPN" service to their customers.
Existing IETF standards specify the procedures and protocols that a service provider uses in order to offer this service to customers who have IP unicast and IP multicast traffic in their VPNs.
It is also desirable to be able to support customers who have MPLS multicast traffic in their VPNs.
This document specifies the procedures and protocol extensions that are needed to support customers who use the Multipoint LDP (mLDP) as the control protocol for their MPLS multicast traffic.
Existing standards do provide some support for customers who use mLDP, but only under a restrictive set of circumstances.
This document generalizes the existing support to include all cases where the customer uses mLDP, without any restrictions.
This document updates RFC 6514.
RFC 7441 introduction
Many service providers (SPs) offer BGP/MPLS IP VPN service to their customers.
When a customer has IP multicast traffic in its VPN, the service provider needs to signal the customer multicast states across the backbone.
A customer with IP multicast traffic is typically using PIM (Protocol Independent Multicast) [PIM] and/or IGMP (Internet Group Management Protocol) [IGMP] as the multicast control protocol in its VPN.
The IP multicast states of these protocols are commonly denoted as "(S,G)" and/or "(*,G)" states, where "S" is a multicast source address and "G" is a multicast group address.
[MVPN-BGP] specifies the way an SP may use BGP to signal a customer's IP multicast states across the SP backbone.
This is done by using Multiprotocol BGP Updates whose Subsequent Address Family Identifier (SAFI) values contain the codepoint for MCAST-VPN (as defined in [MVPN-BGP]).
The NLRI (Network Layer Reachability Information) field of these BGP Updates includes a customer Multicast Source field and a customer Multicast Group field, thus enabling the customer's (S,G) or (*,G) states to be encoded in the NLRI.
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