[asterisk-users] Call drop on Aastra SIP phones

Bruno Rocha bruno at 3gnt.net
Mon Jul 14 11:12:18 CDT 2014

Hello everybody,

I'm having issues with calls being dropped on Aastra phones, when the 
call is on hold. Tested with models 6863i and 6867i.
I've figured that the call is dropped by Asterisk when it reaches the 
rtpholdtimeout limit.

I've reported the issue to Aastra, asking them to implement some kind of 
"RTP keep-alive" feature on their phones. Maybe the phone could send 
some RTCP frame (or an empty RTP frame) just to prove it is alive.
Unfortunately Aastra said the hold behaviour on the phone is correct, as 
per RFC 3264, section 8.4, 4th paragraph:

   Typically, when a user "presses" hold, the agent will generate an
   offer with all streams in the SDP indicating a direction of sendonly,
   and it will also locally mute, so that no media is sent to the far
   end, and no media is played out.

They can implement the "RTP keep-alive" feature only if there is some 
RFC describing that behaviour.

Is Aastra correct? Should I configure Asterisk with rtpholdtimeout=0 to 
solve this issue and make Asterisk RFC compliant?
Or should Asterisk rtpholdtimeout code take the phone RFC behaviour into 
account and don't drop the call?

Best regards,

Bruno Rocha

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