The MPLS-OPS Archive

[S Leung <eiei123us@yahoo.com>]

Hi,

I am trying to understand how admission control
should work in RSVP-TE, and would very much appreciate
if anyone can give me some feedbacks on the following
questions that I have.

Thanks,
S Leung.

> Hi,
> 
> I have a question on RSVP-TE admission control.
> My understanding is that the actual bandwidth
> reservation is done when the RESV message is
> received, and the bandwidth is reserved on the
> interface from which the RESV message is received.
> 
> However, in RFC 3209 Section 4.7.3 it indicates that
> admission control happens upon the receipt of the
> PATH message.
> 
> "When a new Path message is considered for
> admission,
> the bandwidth requested is compared with the
> bandwidth
> available at the priority specified in the Setup
> Prio.
> 
> If the requested bandwidth is not available a
> PathErr
> message is returned with an Error Code of 01, 
> Admission Control Failure, and an Error Value of
> 0x0002..."
> 
> As reservation takes place at the outbound interface
> of the Path message, in order to do admission
> control
> that means the outbound interface of the Path
> message
> needs to be determined before CAC can be applied, my
> question is that why don't we wait until the Resv
> message is received, considering that the bandwidth
> requested can be modified/decreased by the egress
> router?
> 
> Also, I assume that the bandwidth requested is
> compared with the bandwidth available on the
> outbound
> interface, and pre-emption should only affect the
> LSPs
> that are routed on the same outbound interface, is
> that correct?
> 
> Thanks very much for your reply in advance.
> 
> S. Leung


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