[asterisk-dev] IAX internet draft (draft-guy-iax-00)

[Steve Kann]

Adrian Sietsma wrote:

> Steve Kann wrote:
>
>>>>
>>>> but if we get 1,2,4,5,3 then it is 4
>>>>
>>
>> Here's what happens for each frame:
>>
>> 1: OK, acked
>> 2: OK, acked
>> 4: this is out-of-order, ignored (vnak could be sent, but it doesn't 
>> really matter)
>> 5: same as 4.
>> 3: This is OK, and gets acked.
>>
>> ...
>>
>>>
>>> If that is so,then how do frames 4 & 5 ever get acked ?
>>
>>
>>
>> They would be retransmitted, because they are not acked the first 
>> time they're sent, and eventually, the retransmits would be acked.
>>
> Ok, got it.
> This would imply that _all_ frames received subsequently would be 
> ignored, until frame #4 re-arrives, and resets the sequence ?


That's correct.  That's how it works presently, and the way it would 
have to work, unless the receiver stored out-of-order frames (which 
would be a worthwhile optimization to make for the lossy link case, as 
you note below).  I think that such an "out-of-order" reciever store 
could be done without changing the specs, though -- as long as it 
doesn't _act_ on frames out-of-order, it could probably defer processing 
them until it got the missing frame.


>
> I have noticed that iaxclint goes into a "retry frenzy" if hammered 
> with too many full frames (text) too quickly, over a lossy (wireless) 
> link. Ethereal reports blocks of packets being retried, despite being 
> recieved ok.
>
> Adrian
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