Dear WG,
Just a follow up on the comments made against the residual bw draft:
(see minutes)
3.1<https://tools.ietf.org/wg/pce/minutes?item=minutes-99-pce-00.html#section-3.1>.
PCEP Extensions for Residual Bandwidth (Daniele Ceccarelli, 10 min)
[45/120]
draft-lazzeri-pce-residual-bw<http://tools.ietf.org/html?draft=draft-lazzeri-pce-residual-bw>
Jon: Clarification question for Daniele - Is this applicable for only
one
source requesting the LSP, so that reporting residual BW can be
used?
What happens if multiple PCCs are setting up LSPs and consuming
resources
separately?
Daniele Ceccarelli: We had considered single source (a single H-PCE),
and in
case of multiple, some synchronization between
them. Scope
was a single source.
Dhruv: Even if only single source node, the proposed mechanism will
only work
if there is no other path computation requests asking for
the same
resource. It is possible there should be a timing issue,
i.e., the
residual resource should only be valid for a duration of
time.
Shouldn't this be similar to delay metric, the delay at the
time of
path computation in a stateless PCRep message and receiving
delay
later via telemetry.
Daniele: In the worst case, you cannot get any advantage, but it
improves if
you are lucky.
Dhruv: Agree.
We were thinking of addressing the "race condition" issue as follows:
* Apply the concept only to stateful requests
* Define a flag in the path computation request that allows registering for
residual bandwidth updates (PCEP report). IN this way if the residual bw
changes due to LSP setup (either by other HPCE or by any other mean) the H-PCE
can receive a notification.
Please note:
1. This is applicable to black topologies
2. This is applicable also to white topologies in those cases where
TE-topology updates do not include path level residual bw.
3. It is still possible to have a number of stateless path computation
requests (used to e.g. define the domain sequence in multi-domain scenarios)
but then register for updates only when a stateful request is issued.
Thanks a lot
Daniele + co-authors
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