Re: [Ice] Eric Rescorla's No Objection on draft-ietf-ice-trickle-18: (with COMMENT)

[Peter Saint-Andre <[e-mail]>]

On 4/4/18 10:45 AM, Peter Saint-Andre wrote:
> On 4/3/18 9:38 AM, Peter Saint-Andre wrote:
>> On 4/2/18 11:13 PM, Christer Holmberg wrote:
>>> Hi,
>>>
>>> A couple of comments:
>>>
>>>>>    agent SHOULD follow a policy of keeping the higher priority candidate
>>>>>    unless it is peer reflexive.
>>>>>
>>>>> IMPORTANT: This section is confusing wrt how pruning works. AIUI, you 
>>>>> follow ordinary 5245 pruning procedures at the beginning of the 
>>>>> connection for whatever candidates you have. Is that incorrect?
>>>>
>>>> Right, there's no reason to override normal pruning procedures.
>>> ...
>>>>> Why are you discarding before you check for redundancy?
>>>>> This seems like it evicts the wrong pair.
>>>>
>>>> Hmm, it could. Checking the max-pair rule after the redundancy check would indeed make more sense.
>>>
>>> What if the pruning would result in a pair that e.g., is already in the Succeeded state to be removed? Is that what you want to do?
>>
>> I don't think so. I'm on a call right now but will reply again.
> 
> That was a long call. ;-)
> 
> It seems to me that when a new candidate pair is received, we'd want to
> remove a duplicate pair only if it is in the Waiting or Frozen state.
> 

Specifically, I suggest the following revised text for Section 8.1:

###

8.1.  Pairing Newly Learned Candidates and Updating Check Lists

   Forming candidate pairs works as described in the ICE specification
   [rfc5245bis].  However, adding the new pair to a check list happens
   according to the following rules:

   1.  If the new pair's local candidate is server reflexive, the agent
       MUST replace the candidate with its base before completing the
       redundancy check in step 2.

   2.  The agent eliminates redundant pairs by following the rules in
       Section 5.1.3 of [rfc5245bis], but only if the old pair has a
       state of Waiting or Frozen (thus avoiding removal of pairs for
       which connectivity checks are in flight or for which connectivity
       checks have already yielded a definitive result).

   3.  If after the foregoing redundancy test the check list where the
       pair is to be added already contains the maximum number of
       candidate pairs (100 by default as per [rfc5245bis]), the agent
       SHOULD discard any pairs in the Failed state to make room for the
       new pair.  If there are no such pairs, the agent SHOULD discard
       the new pair.

   4.  Otherwise, add the new pair to the check list.

###

Peter