PR26 - Retransmission

[Matthew Lovett <MLOVETT@uk.ibm.com>]

Hi all,

The current proposal for PR26 reads as follows:

Add a new invariant:
While the Sequence is not closed or terminated, the RMS must retransmit 
any messages that are missing from the most recent acknowledgement 
message.

I don't think that is quite right. Using a lowercase must doesn't seem to 
help much, and an uppercase MUST would be too strong. (Consider a device 
with limited storage, they might be happy to retransmit messages up to 
some limit, but need to recover storage after that point. There are plenty 
of other impl choices that don't like this MUST too.)

How about the following alternative:

Add a new invariant:
While the Sequence is not closed or terminated, the RM Source SHOULD 
retransmit any messages that are missing from the most recent 
acknowledgement message.

The editors may wish to play with the trailing part of the sentence, to 
cope with the permutations of Acks/Nacks, and the definition of 'most 
recent', but I don't think that is the core of the issue. I think the 
SHOULD makes the common impl choice clear, without forcing implementers 
into a corner.

Note that this proposal basically matches the point that we got to on the 
last call. I hope that most people are able to accept it.

Thanks

Matt