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non-RSVP routers.

  • From: David Charlap <David.Charlap@marconi.com>
  • Date: Mon, 04 Feb 2002 11:48:27 -0500

Subhakar K S wrote:
> 
> How does an intermediate router finds if its
> downstream router is RSVP aware or not.

RSVP does not provide a mechanism to detect a non-RSVP router
downstream.  Any such detection must be through means beyond the scope
of RSVP.

However, RSVP can detect one upstream.  RSVP's common header includes a
TTL field, which is assigned to match the IP header's TTL.  If an RSVP
message gets forwarded through a non-RSVP router, the IP TTL will be
decremented, and won't match the RSVP TTL.

In classical RSVP, the "adspec break" bit is set in the ADSPEC object to
inform nodes further downstream that there are non-RSVP routers along
the path.

In RSVP-TE, non-RSVP routers are not supported, so a PathErr would be
generated once the non-RSVP router was detected.

See RFC 2205 and RFC 3209.

-- David