Subject: [AVT] Handling lost marker packet in 2833bis

From: Tom Taylor <[email-masked]>
Date: Wed, 10 Nov 2004 16:35:08 -0500

Kevin Noll had asked for advice in 2833bis on what to do if the initial packet of 
an event report (with the 'M' bit set) got lost but subsequent packets were 
received.  I did incorporate some advice in rfc2833bis-05, but it's probably a 
good idea to put it out to the list for consideration.  Here's what was added to 
rfc2833bis-05:

    2.5.2.2  Playout of Tone Events
....
       If a receiver receives an event packet for an event which it is not
       currently playing out and the packet does not have the "M" bit set,
       earlier packets for that event have evidently been lost.  The
       receiver MAY determine on the basis of retained history and the
       timestamp and event code of the current packet that it corresponds to
       an event already played out and lapsed.  In that case further reports
       for the event MUST be ignored, as indicated in the previous
       paragraph.  If this is not so, the receiver MAY attempt to play the
       event out to the complete duration indicated in the event report.
       The appropriate behaviour will depend on the event type concerned,
       and requires consideration of the relationship of the event to audio
       media flows and whether correct event duration is essential to the
       correct operation of the media session.

-- 
Tom Taylor
Carrier VoIP Standards Development
Nortel Networks
Phone +1 613 763 1496  (ESN 393-1496)
E-mail: [email-masked]

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---

From: Stephen Casner <[email-masked]>
Date: Thu, 11 Nov 2004 15:02:34 -0800 (PST)

Tom,

The way that packet loss is detected is through the sequence number.
The missing M bit is another indication, but the primary indication is
the sequence number gap.

                                                        -- Steve