[Users] mediaproxy error (SDP message)

[unplug]

Hi,

  Recently, I noticed there is an error from the log for a particular user.
May  8 12:34:08 o01 /usr/local/sbin/openser[25451]: error:
mediaproxy/getSDPMessage(): SDP message has zero length
May  8 12:34:08 o01 /usr/local/sbin/openser[25451]: error:
use_media_proxy(): failed to get the SDP message

It seems that mediaproxy can't get the SDP message and the user failed
to make/receive call in such error occurred.  As the user is using
ipphone behine NAT, I wonder if it is related to the router problem. 
Any suggestion for this error?

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