Exactly. So what is the problem within this thread which you claim that
clients may "risk of inconsistent path selection" ?
R.
This is standard BGP if the IGP metrics are equal.
--
Jakob Heitz.
-----Original Message-----
From: Robert Raszuk [mailto:[email protected]]
Sent: Sunday, March 27, 2011 3:17 PM
To: Jakob Heitz
Cc: [email protected]; IETF IDR
Subject: Re: [GROW] draft-ietf-grow-diverse-bgp-path-dist:
risk of inconsistent path selection
Jakob,
> To prevent clients in different clusters from choosing
> different bestpaths based on tie breaker (f):
Can you restate what is the problem with the above ?
Today clients would chose different best paths when IGP metric to one
next hop is closest on one to NH1 and closest on the other to
NH2. And
this check happens well above step (f).
How is this at all related to the diverse path draft like the subject
could indicate ?
Thx,
R.
Route selection tie breakers in RFC 4271 state:
f) Remove from consideration all routes other than
the route that
was advertised by the BGP speaker with the lowest BGP
Identifier value.
g) Prefer the route received from the lowest peer address.
Suppose RR Planes use different BGP Identifier values.
If they use the same BGP Identifier, a similar argument
can be made for peer address.
To prevent clients in different clusters from choosing
different bestpaths based on tie breaker (f):
The RR Plane that advertises the best path MUST be configured
with a BGP Identifier higher than that of the RR Plane that
advertises the 2nd best. This must be higher than that of
the Plane that advertises the 3rd best and so on.
I'm not sure if this rule completely solves the problem.
If not, then the "Edge_Discriminator attribute" proposed
by draft-pmohapat-idr-fast-conn-restore may be required.
Also, this would need to be applied before rule (f).
--
Jakob Heitz.
_______________________________________________
GROW mailing list
[email protected]
https://www.ietf.org/mailman/listinfo/grow
_______________________________________________
GROW mailing list
[email protected]
https://www.ietf.org/mailman/listinfo/grow
