[icnrg] Further comments on draft-anilj-icnrg-dnc-qos-icn-00.txt
"David R. Oran" <daveoran@orandom.net> Fri, 29 March 2019 11:49 UTC
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From: "David R. Oran" <daveoran@orandom.net>
To: Anil Jangam <anjangam@cisco.com>, ICNRG <icnrg@irtf.org>
Date: Fri, 29 Mar 2019 12:49:31 +0100
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Subject: [icnrg] Further comments on draft-anilj-icnrg-dnc-qos-icn-00.txt
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In listening to the talk and reflecting on my first set of comment, I have two more things for us to think about - In addition to figuring out the ordering of the QoS treatments and how it interacts with PIT aggregation, there’s also interaction with Interest Lifetime. Let’s say there are two consumers, one with a realtime deadline who sets “low latency” QoS and a corresponding short Interest Lifetime, and another with a “background” QoS and a corresponding long Interest lifetime. This raises two questions, first, what should the interest lifetime be on the forwarded Interest? If it is arrival-order dependent weird denial-of-service behavior can happen to the user asking for background treatment for example if the Interest lifetime is cut back to that of the “low latency” user. Second, if you keep the longer interest lifetime as the only value in the PIT, the “low latency” user will have useless data returned if the answer comes back late based on the longer interest lifetime. This means we may need to (a) forward interest with longer interest lifetime even if it has “lower” QoS, and (b) record Interested lifetime per-arrival face so old useless data is not returned to the “low latency” user. - I made a comment on the draft that we may need a stack of markers rather than doing rewriting in order to preserve QoS information across domain boundaries. That was wrong; on further consideration I think we don’t actually need this and can do simple re-writing at domain boundaries. The reason is that the RPF state in the PIT actually keeps all the state necessary to handle the return traffic right. The one case not covered is if some upstream domain entry wants to “recover” the QoS marking from a downstream domain that is not its downstream neighbor. I’ve never seen anybody wanting to do this in practice, so it may be a good tradeoff. DaveO
- [icnrg] Further comments on draft-anilj-icnrg-dnc… David R. Oran