Does Asterisk support SIP Outbound mechanism, RFC 5626

Hi there,

Basically subj, does Asterisk provide support for SIP Outbound mechanism as defined by RFC 5626 when Asterisk is acting as the Registrar?

What I’m seeing is when a UAC advertises header ‘Supported: outbound’ with ‘Contact: <; +sip.instance=xxxyyyzzzz’ in the REGISTER request, in reply Asterisk removes the ‘Supported: outbound’ header, which leads me to believe Asterisk does not support SIP Outbound?

Can someone confirm?


SIP outbound is not implemented in either chan_sip or chan_pjsip.

Thanks for confirming.

PJSIP datasheet shows support for SIP outbound.

Does Asterisk have a plan on implementing it in the near future?


Their SIP outbound support is in regards to their “pjsua” library which Asterisk does not use.

I know of noone actively working on any kind of outbound support.

Since Asterisk 17, thanks to ASTERISK-27971, SIP Outbound can be added to the Header Supported with support_outbound=yes. This is mentioned in the Wiki but not in the file pjsip.conf.sample (bug?). However, I am not sure if this is just a ‘fake’ support by adding the header without any functionality. Please, double-check.

Out of curiosity: Why are you asking exactly? UDP Double-CRLF-Refresh (not this ping pong from RFC 5626) is available since Asterisk 11. Is that not sufficient in your case?