Subject: [bess] DF election rule in EVPN MH, for untagged interface - reg

From: Jaikumar Somasundaram <[email-masked]>
Date: Fri, 5 Apr 2019 04:15:31 +0000

Hi All,

RFC7432, section 8.5, talks about DF election algorithm (service carving algorithm)

only for <ES, VLAN> for VLAN-based service or <ES, VLAN bundle> for VLAN-(aware)
bundle service.

But there wont be any vlan id for untagged interface and so I wonder
how the service carving algorithm can be applied to elect the DF.
Also, should I use the lower VLAN ID even in the case of VLAN-bundle
service, for electing the DF?

Could some one help me to understand this please?

==========<snip from RFC 7432, section 8.5>===============
8.5<https://tools.ietf.org/html/rfc7432#section-8.5>.  Designated Forwarder Election

...

   The default procedure for DF election at the granularity of <ES,

   VLAN> for VLAN-based service or <ES, VLAN bundle> for VLAN-(aware)

   bundle service is referred to as "service carving".
...

      Assuming a redundancy group of N PE nodes, for VLAN-based service,

      the PE with ordinal i is the DF for an <ES, VLAN V> when (V mod N)

      = i.  In the case of VLAN-(aware) bundle service, then the

      numerically lowest VLAN value in that bundle on that ES MUST be

      used in the modulo function.
...
=========<snip end>======================================

Thanks & Regards
Jaikumar S