|
When we added the ability to send more than one RAMS-R message, we opened up a few design points that we now need to consider. We need to have some nomenclature for describing the "initial RMS-R" and "subsequent RMS-R", so I will start with using those words. Better words would be appreciated. The first design point I would like to address is what the RS is required to do when it receives an RAMS-R for a burst that is already in flow (aka "subsequent RMS-R"). We stated that the least it could do was "ignore it". Does this imply that there is no requirement to send an RMS-I in response to RMS-R messages referencing an in-progress flow? If so, we should add clarifying text in the document that cautions the RR not to assume the RAMS-R was dropped. I briefly considered requiring the RS to send a RAMS-I for each received RAMS-R. Unfortunately, this then leads to another set of corner cases, and may result in a chatty exchange of messages. We also need to consider how to deterministically differentiate between the initial RMS-R message and subsequent RMS-R messages, particularly in the event of packet loss or (unlikely) re-ordering. This probably leads us to including a monotonically increasing sequence number on the RMS-R. Dropped RMS-R messages should not be a protocol problem, as the first one received will trigger the burst. Subsequent RMS-R messages either change the burst shape or they do not, and they do not trigger additional messages. Similarly, if the initial RMS-I is dropped it will probably trigger an additional RMS-R message. Subsequent RMS-I messages will either be received by the RR or they will not, and they will not trigger additional messages. So, has anybody considered these design points in detail? I have started to go down this path, but it gets complicated quickly. In order to limit the complexity, I suggest that we state that the first received RMS-R triggers a RMS-I. Further RMS-R messages may flow. Further RMS-I messages may also flow, but there is no explicit requirement to send an RMS-I in response to a subsequent RMS-R.
Bill VerSteeg |