Subject: [MMUSIC] [mmusic] #10: Source and mirror clock synchronization

From: "mmusic issue tracker" <[email-masked]>
Date: Tue, 31 Jan 2012 18:00:11 -0000

#10: Source and mirror clock synchronization

 From Magnus:

 28. Section 7.1.2:
    The
    Receive timestamp MUST be based on the same clock used by the
    loopback-source.

 This is an impossibility. The two end-points can't have the same clock.
 The can have a common clock reference like NTP. But, they are still not
 the same clocks, but possibly synchronized well enough for your needs

 What I guess you are after is that the clock rate should be the same as
 for the packet encapsulated. The Timestamp in the outer header should
 also be corrected.

 I also think you should clarify that the receive timestamp and the
 timestamp in the header needs to be from the same clock in the mirror.
 Otherwise the time spent on the mirror for the packet is not useful. I
 think it might also be worth actually writing up the measurements that
 become possible by these two timestamps plus having the source logg
 transmission and arrival times. The fact that one can derive both one
 way delay and jitter for each loopback packet is kind of important.

 However, to have correct one way delays the mirror clock needs to be
 synchronized with the source clock, or at least the current offset.

-- 
--------------------------+------------------------------------------------
 Reporter:  hkaplan@…     |      Owner:  draft-ietf-mmusic-media-loopback@…
     Type:  defect        |     Status:  new
 Priority:  minor         |  Milestone:  milestone1
Component:  media-        |    Version:  1.0
  loopback                |   Keywords:
 Severity:  In WG Last    |
  Call                    |
--------------------------+------------------------------------------------

Ticket URL: <http://trac.tools.ietf.org/wg/mmusic/trac/ticket/10>
mmusic <http://tools.ietf.org/mmusic/>