Re: [LOOPS] draft-li-tsvwg-loops-problem-opportunities-05 - why do traffic engineering at the overlay as well?

[Carsten Bormann <[e-mail]>]

> 
> Still this relies on endpoints to enable ECT(0) processing that might or might not be a hurdle to deploying something else. Do people see LOOPS brings benefit  if the endpoints do not support ECN?

Not the MVP (minimum viable protocol) we are targeting now — doing a one-to-one drop-to-drop signaling doesn’t give you a lot of recovery :-)

Since the issue really is what traffic can be directed to the LOOPS tunnel, it is somewhat trivial to provide benefit once we have better segment-to-path congestion signaling.

>>> As I think I understand, a path increases the workload in response to loss by adding FEC that recovers the loss but hides the increase in rate from the endpoints, instead setting ECN-CE marks to notify of congestion. If the endpoint reacts, then the load stabilizes. Do I need to worry whether the endpoint's reaction to ECN-CE marks is something that the network would also need to monitor, to confirm that CE-marking is actually causing a congestion reaction?
>> Do we do that without LOOPS?
> I think I am concerned enough to worry about this, unless I can see a lot more experience from ietf-tsvwg-tunnel-congestion-feedback.

How can we have any useful ECT traffic at all if we need to suspect that doesn’t react to CE marks?  I’m not sure I understand what the existence of the LOOPS tunnel adds to that (assuming there is some sane overhead limit, such as 20 % — I’m sure 10000 % wouldn’t be so great).

>> (We could add flow-specific circuit breakers, but that creates a lot of processing.)
> 
> Indeed and a circuit-breaker wouldn't be easy to realise (or perhaps appropiate) for short/chatty flows, and that makes me wonder really how much need there is to experimentally investigate what is needed.

A single unruly flow won’t influence a high-mux aggregate.
If there are many unruly flows, the aggregate circuit breaker will trip.
Is there anything interesting in between?

Grüße, Carsten