Subject: Re-Routing

From: "Mareline Sheldon" <[email-masked]>
Date: Mon, 10 Sep 2001 10:34:03 +0530

Suppose i have a LSP set up between a pair of LSRs. What happens when due to
some unexplained reason one of the intermediate LSRs reosurces get so tied
up that it is not able to deliver the gauranteed QoS it promised during the
setup phase when (i) RSVP is used and in the second case when (2) CR-LDP is
used ?

Would the guilty LSR try to re-route or would it bring down the whole LSP ?

A strictly specified explicit route cannot be re-routed except by the
ingress LSR and hence it has to be brought down .. however a loosely
specified portion of an explicitly routed LSP, or any part of the hop-by-hop
routed LSP may be re-routed.

Pl. explain as to what whould happen.

Regards,
Mary

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From: Eric Gray <[email-masked]>
Date: Mon, 10 Sep 2001 09:32:51 -0400

Mary,

    I don't think the signaling protocol is immediately relevant.  In neither
case is there a requirement that an LSR monitors its own performance
and takes any action as a result of degraded or non-performance.  Even
if an implementation does this (say, for certain high paying services), it
will most likely cease providing other services (an attempt to maximize
revenue) until it is again satisfying the degraded or non-performing high
paying service.

    In the meantime, packets will be dropped.  This may cause problems at
higher levels and will have to be dealt with there.

    Also, any application that absolutely depends on delivery to the extent
that a service disruption is better than a service degradation, should do
its own monitoring and control of involved LSPs.

--
Eric Gray

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From: "Mareline Sheldon" <[email-masked]>
Date: Mon, 10 Sep 2001 19:13:38 +0530

Isn't re-routing like saying .. "Hey i'm having a problem ! Choose this path
for all your data transfer !" ??
And will there be any packet losses when re-routing because we have this
concept of "make before break" ??

Mary

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From: Eric Gray <[email-masked]>
Date: Mon, 10 Sep 2001 18:03:50 -0400

Mary,

    I'm not sure what you're asking, but it's generally a bad idea to rely on
the component that is having trouble to bail itself out - particularly if it is
causing its own trouble in the first place.

--
Eric Gray