Re: [rtcweb] Consent Freshness: Some suggestions for editorial clarifications

Hi,
Based on feedback I receive from implementers, there are a couple of clarifications I think would be useful in the consent freshness draft.

Q1:
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As STUN binding requests for consent are sent unreliably, and are not re-transmitted, I think it would be useful to have some explicit text saying that individual requests (and/or their associated responses) may get lost in the network, and that a sender must be prepared that a response to such requestmay never arrive.

It may be obvious to us, but maybe not as clear to the first-time reader of the draft.

Q2:
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Section 4.1 says:

“That is, if a valid STUN binding response corresponding to one of the STUN requests sent in the last 30 seconds
                has not been received from the remote peer's Transport Address, the endpoint MUST cease transmission on that 5-tuple.”

First, I suggest the following clarification:

s/”to one of the STUN requests sent in the last 30 seconds”/”to one of the STUN requests (not necessarily the last one) sent in the last 30 seconds”.

Second, there is no explicit text on for how long the client keeps the STUN transaction alive, i.e. for how long it waits for the response.

I assume that, after 30 seconds, the client does not need to maintain state and wait for the response anymore.

My understanding is that the sender doesn't need remember the request for 30 sec, instead it needs to remember it only for RTT duration. If a matching response is received within that duration you have a 'hit'. If there is no 'hit' over the last 30 sec, consent expires.

I agree this isn't clear in the current version.

How do you calculate the RTT? Based on previous transactions? What if, for whatever reason, the roundtrip for a STUN binding request/response takes longer that previously? You would discard the response.

I think it is much more clear the specify a time. 30 seconds is a good value, because if it takes longer the response is “unvalid” anyway.

Regards,

Christer

I think it would be useful to explicitly indicate that, and also say that responses that are received after that time must be discarded.

Thanks!

Regards,

Christer

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