[asterisk-users] Asterisk Transfers

Joshua C. Colp jcolp at digium.com
Thu Mar 28 16:20:41 CDT 2019

On Thu, Mar 28, 2019, at 4:56 PM, Dan Cropp wrote:
> 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
> and
> 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)?

I'll answer here too for anyone interested. The RFC[1] states that it should be present so that the remote endpoint knows whether or not it is supported. Removing it may effectively remove support. It depends on whether a remote endpoint takes it into account or not when issuing the REFER.

You also can't limit it at that level, because generally for most things you don't know if you are sending or receiving a REFER. The "norefersub" Supported occurs before it happens. You could only limit it globally.

[1] https://www.ietf.org/rfc/rfc4488.txt

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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