Subject: [AVT] V.8 bis events in draft-ietf-avt-2833bisdata-xx

From: Tom Taylor <[email-masked]>
Date: Mon, 27 Jun 2005 19:05:35 -0400

I've modified draft-ietf-avt-2833bisdata-xx as previously agreed on the 
list, but have hesitated over what to say about congestion handling.  A 
proper analysis requires that I go over each of the various modem 
protocols and figure out how vulnerable it is to playout gaps.  It would 
be much easier if I had expert advice to help me.  I may seek such 
advice from Study Group 16 next week.

I have another issue: the current V.8 bis events don't make sense to me. 
  The problem is that V.8 bis signals start with a 400 ms initial 
segment that doesn't select which event will be reported, only whether 
this is an initiating or a responding signal.  So it is only 400+ ms 
into the signal that the sender can decide what event to report.  That's 
quite a buffer lag.

The lag may make sense if the gateway is using V.150.1 modem relay, 
since in that case the sender is supposed to block V.8 bis signals from 
appearing in-band on the IP side of the gateway.  I'm not sure if it 
makes sense in other applications.

What would make sense is to add two more events to indicate detection of 
a V.8 bis initiating signal or responding signal respectively.

I suspect V.8 bis is a bit of an orphan and not widely implemented.  Am 
I fussing too much or do the additional events make sense?

Tom Taylor

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