[Asterisk-Users] Asterisk not conforming to the RFC?/Aastra phonedelay issue

[dbruce]

I don't believe that this issue is with Asterisk. The issue is that the phone does not set up the RTP stream until it receives the "200 OK". Asterisk sets up the RTP stream when it receives, or sends, the message with SDP (either INVITE message, 180 response or 183 response), as per the RFC.

The firmware for the 91XXi phones were branched from the 480i version back in late 2004. Since this branching, the 480i firmware has been fixed, and the phone now sets up the "early media".

The following is from the "KNOWN ISSUES" section of the 480i release notes from November 2004, v1.0.0.50.

>    2.6 FAILURE TO PROCESS "REMOTE RINGBACK"
>        A device may send an invitation that includes an SDP message. When the terminator responds with an alert message, it many also contain SDP message. This is known as "early media" or "remote ring-back" and indicates that >        the terminator will provide ring-back tone.  The originating device should provide this tone to the originating user.  Currently, the firmware does not process this remote ringback.
>        Currently under investigation.

I would suspect that the 91XXi firmware was never updated to correct this problem.

Also, The Asterisk voicemail application will answer the channel if it hasn't already been answered, before playing any prompts. Answering the channel send a "200 OK" message to the phone. The phone will then set up the RTP voice stream for the call. So, if the phone is "clipping" the begining of the voice prompts, it is an indication that the phone is taking a long time to set up the RTP after receiving the "200 OK" message.

This behaviour is not seen on the other call servers that Aastra test the phone against, due to the fact that this issue was known a long time ago, and these call servers have incorporated a workaround to deal with it.

Fortunately, there is a workaround for Asterisk as well. In your dialplan, issue an "Answer" and "wait(1)" berfore sending the call to voicemail.

Regards,

Derek

  ----- Original Message ----- 
  From: Franklin Webb 
  To: Asterisk-Users at lists.digium.com 
  Sent: Friday, August 19, 2005 12:49 PM
  Subject: [Asterisk-Users] Asterisk not conforming to the RFC?/Aastra phonedelay issue


  Fellow list members,

  I have run into an issue where I encounter a delay at the beginning of a phone conversation when I make outgoing calls through Asterisk with an Aastra 9133i hardphone.  This is most noticable when I call a voicemail system with the Aasta and then with a land line or other VoIP phone.  The first word or two of the voicemail message is generally cut off.

  According to Aastra's engineering this is because Asterisk does not confromt o the RFC, setting FTP voice stream before getting the ACK.  They have not seen this with other call servers besides Asterisk.

  Has anyone else seen this sort of behaviour or is aware of this?

  Right now we are in the process of switching over the business edition, and we are wondering if we will see a difference in this problem.

  Thanks,

  Franklin Webb


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