[asterisk-users] Asterisk Transfers

Dan Cropp dan at amtelco.com
Thu Mar 28 14:55:43 CDT 2019

Hi Joshua,

Unfortunately, I tried including the Refer-Sub true and also false in the REFER packet and Cisco seems to ignore them.

Refer-Sub: false
Refer-Sub: true

The only thing that seems to work properly with the Cisco switch is to remove the norefersub from Supported

Joshua, is it correct that the norefersub has to be in res_pjsip_refer.c for Asterisk to be able to process incoming REFER requests?

If I were willing to write code, how difficult would it be to make the norefersub optional or used for incoming (allowing phones to REFER), but not for outgoing (not send to Cisco)?

-----Original Message-----
From: Dan Cropp 
Sent: Thursday, March 28, 2019 12:55 PM
To: asterisk-users at lists.digium.com
Subject: RE: [asterisk-users] Asterisk Transfers

Thank you Joshua.

We're trying to run more tests.
We believe Cisco may not be adhering to the specification.  Unfortunately, we're also stuck with having to make it work.

An interesting test, I commented out the norefersub from the res_pjsip_refer.c code just for a test.  Without this, Cisco does sent the NOTIFY packets to let Asterisk know the status (Trying, Ringing, OK, 486 Busy Here, ...)

Would it make sense for me to try including the Refer-Sub in the REFER packet Asterisk sends to Cisco?  Perhaps Cisco sees the norefersub, but not the Refer-Sub header.  It may interpret the lack of a Refer-Sub header in the REFER incorrectly?


-----Original Message-----
From: asterisk-users <asterisk-users-bounces at lists.digium.com> On Behalf Of Joshua C. Colp
Sent: Thursday, March 28, 2019 9:18 AM
To: asterisk-users at lists.digium.com
Subject: Re: [asterisk-users] Asterisk Transfers

On Thu, Mar 28, 2019, at 11:10 AM, Dan Cropp wrote:
> Is there no one who knows if there is a way to turn off the norefersub setting?
> Supported: norefersub
> This happens in the TRYing, OK, and other commands in response to the INVITE.
> For chan_sip, I noticed it does not send the norefersub. As a result, 
> Cisco then sends NOTIFY packets with TRYing, Ringing, OK inside them.
> This basically gives the chan_sip code the ability to know if the 
> (Transfer) is succeeding or not.

There is no way to configure it. It would have to be removed from res_pjsip_refer's code itself. The presence of "norefersub" in Supported also isn't supposed to enable it. It's just for stating it is supported. It's supposed to be enabled by the presence of the "Refer-Sub" header in the REFER itself. I don't believe we set that on the REFER we produce, we only care if we receive a REFER with it in place.

Joshua C. Colp
Digium - A Sangoma Company | Senior Software Developer
445 Jan Davis Drive NW - Huntsville, AL 35806 - US Check us out at: www.digium.com & www.asterisk.org

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