RE: [rohc] a dummy application protocol (DAP) for SigComp interop

["Surtees, Abigail" <abigail.surtees@roke.co.uk>]

Hi Zhigang, all,

Thanks for your hard work on DAP.  I think we have a good interoperable protocol.  I have a couple of questions about its behaviour though.

If the sender sets the need-response header field to TRUE but doesn't receive anything back within a certain time, what should it do?  Should it retransmit the message it just sent or carry on and transmit the next one it was planning to send anyway?

I think to answer this we have to look at the test scenarios.  I think the main one where the possibility of retransmission may be interesting is the case of dropped packets.

As this is not a huge issue I think that it would be good if we could configurably either retransmit or continue but that continuing with the next message is simplest, and sufficient if configurable isn't possible (dropped packet retransmission can be dealt with by duplicate messages).

A similar question is about compartments and repeatability of the test.  There are several possible behaviours for an endpoint sending a return message:
- send back what it received,
- send an arbitrary message,
- send a specific message

If I am a receiver and I have specific messages to send to separate compartments at the same remote endpoint, does it matter which I send to which compartment?  If it does (possibly for repeatability of the test?), then can this be agreed out of band e.g. configured compartment ids or must it be worked out (if so, how)?
Again I think we need to look at the scenarios we want to test, to see how much of an issue this is.
I think that automatically working this out, or sending the information to the receiver would require changes/enhancements to DAP so I suggest that we are able to configure compartment ids and exchange the information of what they are verbally.

Any thoughts/comments welcome.

Best regards,

Abbie


>Hi,
>
>Here is version 1c. Based on comments from Zacco and Abbie, I added 
>clarifications on returned uncompressed DAP messages and 
>"need-feedback"
>header field. 
>
>As planned, I would like to freeze this as the DAP version 1 for now.
>At least it's good enough for the first SigComp interop. 
>
>(Of course, any questions related to the understanding of the document
>are still welcome. I've been trying to be concise, but may not have
>covered every fine details ...)
>
>Thanks for Abbie, Adam and Zacco for their valuable comments.
>
>BR,
>Zhigang
>
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