Technical Summary
Ethernet Virtual Private Network (EVPN) is commonly used with Network
Virtualization Overlay (NVO) tunnels, as well as MPLS and Segment
Routing tunnels. The multi-homing procedures in EVPN may vary based
on the type of tunnel used within the EVPN Broadcast Domain.
Specifically, there are two multi-homing Split Horizon procedures
designed to prevent looped frames on multi-homed Customer Edge (CE)
devices: the ESI Label-based procedure and the Local Bias procedure.
The ESI Label-based Split Horizon is applied to MPLS-based tunnels,
such as MPLSoUDP, while the Local Bias procedure is used for other
tunnels, such as VXLAN.
Current specifications do not allow operators to choose which Split
Horizon procedure to use for tunnel encapsulations that support both
methods. Examples of tunnels that may support both procedures
include MPLSoGRE, MPLSoUDP, GENEVE, and SRv6. This document updates
the EVPN multi-homing procedures described in RFC 8365 and RFC 7432,
enabling operators to select the appropriate Split Horizon procedure
for a given tunnel based on their specific requirements.
Working Group Summary
Was there anything in the WG process that is worth noting?
For example, was there controversy about particular points
or were there decisions where the consensus was
particularly rough?
Strong concurrence of a few active EVPN contributors.
It took a while for the AD review to complete.
Document Quality
Are there existing implementations of the protocol? Have a
significant number of vendors indicated their plan to
implement the specification? Are there any reviewers that
merit special mention as having done a thorough review,
e.g., one that resulted in important changes or a
conclusion that the document had no substantive issues? If
there was a MIB Doctor, Media Type, or other Expert Review,
what was its course (briefly)? In the case of a Media Type
Review, on what date was the request posted?
WG has probed for implementations (documented in the Shepherd writeup).
Current AD processed the document to enhance readability of the document and technical intent and procedures.
No requirement for MIB Doctor, YANG Doctor, media type, and URI type reviews. There is no yang model.
Personnel
The Document Shepherd for this document is Zhaohui (Jeffrey) Zhang. The
Responsible Area Director is Gunter Van de Velde.
IANA Note
This document creates a registry called "EVPN ESI Label Extended
Community Flags" for the 1-octet Flags field in the ESI Label
Extended Community [RFC7432]. Initial registrations are made for the
"Multihoming redundancy mode" field in bits 0 and 1, and the "Split
Horizon Type" field in bits 6 and 7, as follows:
+==============+=============================+===============+
| Bit Position | Name | Reference |
+==============+=============================+===============+
| 0-1 | Multihoming redundancy mode | [RFC7432] |
+--------------+-----------------------------+---------------+
| 2-5 | Unused | |
+--------------+-----------------------------+---------------+
| 6-7 | Split Horizon Type | This Document |
+--------------+-----------------------------+---------------+
Table 2
In addition, the "Multihoming redundancy mode" field is initialized
as follows:
+=======+=============================+
| Value | Multihoming redundancy mode |
+=======+=============================+
| 00 | All-Active mode |
+-------+-----------------------------+
| 01 | Single-Active mode |
+-------+-----------------------------+
| 10 | Unused |
+-------+-----------------------------+
| 11 | Unused |
+-------+-----------------------------+
Table 3
And the field "Split Horizon Type" is initialized as follows:
+=======+===========================+
| Value | Split Horizon Type value |
+=======+===========================+
| 00 | Default SHT |
+-------+---------------------------+
| 01 | Local Bias |
+-------+---------------------------+
| 10 | ESI Label based filtering |
+-------+---------------------------+
| 11 | Unused |
+-------+---------------------------+
Table 4
New registrations in the "EVPN ESI Label Extended Community Flags"
registry will be made through the "IETF Review" procedure defined in
[RFC8126]. This registry is located in the "Border Gateway Protocol
(BGP) Extended Communities" registry.