[SIPForum-discussion] Issue with Silence Suppression

Ashoke Kumar Ghosh ashoke.k.ghosh at gmail.com
Fri Jan 15 15:08:45 UTC 2010

I have some problem with Silence Suppression on from Application Server.


The Appl Server works as B2BUA. It first establishes a session with media
server after receiving an INVITE message from Softswitch for playing
announcement & taking digits from user.


Thereafter, it puts the A party on hold using Re-INVITE (The IP address for
RTP is given as and initiates another session with B party.


Once 180 Ringing/183 Session Progress is received with B party SDP, Appl
Server sends the A party resume using Re-INVITE and B party SDP with Silence
Suppression on.


This call flow is working for more than 3 yrs now. I have seen some old
traces & found the same thing. But now we are getting complaints from
carriers who claim that this is causing problem at their end.


My queries


1.       What is the purpose of Silence Suppression & when it should be

2.       Which is the RFC I can refer to know more on Silence Suppression.

3.       Can Silence Suppression create a problem for proxies as claimed by
the carrier If yes what can be problem


Hope to get a quick response from experts.




Ashoke Ghosh


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