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From Robbie Gemmell <robbie.gemm...@gmail.com>
Subject Re: [proton-j] handling of link-credit
Date Thu, 02 Mar 2017 11:51:33 GMT
On 1 March 2017 at 17:49, Gordon Sim <gsim@redhat.com> wrote:
> On 01/03/17 17:19, Robbie Gemmell wrote:
>>
>> How did you know they had actually stopped or that it was then safe to
>> flow them new credit, just waiting for a while?
>>
>> If you flow new credit before the link is actually stopped you need to
>> cope with that fairly specifically in case they hadnt really stopped.
>
>>
>>
>> There is scope for things to get out of whack otherwise, on both ends,
>> as they need to carefully handle the delivery-count and credit based
>> on what occurs and whether they have already exceeded the previous
>> allowances or not when the updates get sent/arrive.
>
>
> The link credit is an absolute value. Setting it to 0 then to some other
> value should be no different that e.g. setting it to 100, then resetting it
> to 200 before the first flow is known to have been processed by the sender.
> The latest value indicated by the receiver is the valid value.
>

Link credit is an absolute value, but its effect is relative to
another absolute value, delivery-count, which both ends track
semi-independently and reconcile the two at points, which is where the
complexity comes in with reducing credit after it is already granted
and potentially used but not yet known to be used or not used,
something I'm not sure proton currently accounts for, or at least not
in a way an application might expect.

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