Hi Tony/Vishnu,

Would you really want to recompute your data plane TE of your choice only
because control plane propagation was delayed, say even a few hundreds of
ms ?

Thx,
R.


On Fri, Nov 8, 2024 at 10:57 AM Tony Li <[email protected]> wrote:

> Hi Bruno,
>
> I haven't seen a reply from Pavan, so let me jump in...
>
>>
>> I can give a simple distributed TE application example (there are
>> several, but this should give a general idea how this information can be
>> leveraged). In RSVP-TE networks, a TE path computed using a specific
>> snapshot of TED can get rejected during signaling by a transit node because
>> of bandwidth unavailability on a specific link (link bandwidth information
>> in the snapshot of TED used during computation cannot always be “current”).
>> When ingress gets notified of this “error” via RSVP signaling, the link in
>> question is avoided in the subsequent path computation and an alternate
>> path is sought. Most implementations tend to use a configurable “hold time”
>> to determine how long this link needs to be avoided. The awareness of the
>> distribution delay statistics can potentially be used by implementations to
>> dynamically determine an appropriate “hold time” for a given TE link
>> (instead of using a blanket topology-wide configuration).
>>
>>
>>
>> By « delay » do you mean the IS-IS flooding time across the flooding
>> domain or do you mean something else?
>>
>
> Yes, the flooding time across the area.
>
>
>> If this is the flooding time, what distribution delay statistics do you
>> have in mind?
>>
>
> Mean plus 2x std dev. would be a good guess at a cutoff. I reserve the
> right to update this based on future experience.
>
>
>> In current deployment and as a goal in order to neglect this flooding
>> time?
>>
>> e.g., if flooding time could be reduced to 50 ms would you still need
>> this timestamp?
>>
>
> We cannot guarantee that flooding time can be reduced to 50ms.  While fast
> flooding is of course a good thing, reality is a harsh mistress. Other
> implementations might be in the flooding path. Old software will be in the
> network for a very long time. So measuring reality would be helpful.
>
> T
>
>
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