Subject: Query regarding Source IP check mentioned in RFC 5884

From: Kesavan <[email-masked]>
Date: Thu, 25 Nov 2010 22:26:13 +0530

Hello draft authors

Need clarification regarding Section 7 in RFC 5884 which mentions

   “This implies that an LSR MUST
   ignore BFD packets for a given session, demultiplexed using the
   received Your Discriminator field, if the session is in UP state and
   if the My Discriminator or the Source IP address fields of the
   received packet do not match the values associated with the session.”

A router receiving the BFD control packet over an LSP/tunnel could do
the validation of the
received source IP address against the source tunnel interface IP
address maintained by it or the peer router’s (BFD session peer from
whom the packet is received) ip address.
Is it required that the validation could be done against any of these
addresses or has to be
done against the tunnel interface IP only, to qualify it as a valid BFD packet.

Regards,
Kesavan

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From: Dave Katz <[email-masked]>
Date: Fri, 26 Nov 2010 11:48:34 -0600

The point is that, whatever IP addresses are used, they must not change during the life of the session.  This is not a matter of "validating" the source address against some non-BFD content, but simply ensuring that the *same* IP address is received in all subsequent BFD packets after the first.  The rules for choosing the first are elsewhere in the document.

--Dave