We currently only support one method of authentication:

IP Address authentication

Outbound calls are authenticated by the originating IP only. This should only be used where your SIP server, PBX or soft switch has a static IP address. 


Invites must be sent in E163 format, without the leading '+' (e.g. 44123456789).

For example:


Caller ID

Valid CLI must be presented on all calls on E164 format without the leading '+' (e.g. 44123456789). Failure to provide this information may result in your call being rejected without warning.

If you wish to 'withhold' the calling number (i.e. not display to the end user), you should set the 'From:' header to 'Anonymous' and ensure that a valid CLI is given in the P-Asserted-Identity header, for example:

From: "Anonymous" <sip:anonymous@anonymous.invalid>
P-Asserted-Identity: "442079460123" <>
Privacy: id

Or for systems that do not support P-Asserted-Identity, you may use the Remote-Party-ID header, e.g.:

From: "Anonymous" <sip:anonymous@anonymous.invalid>
Remote-Party-ID: <>;privacy=full;screen=yes;party=calling;



DTMF is only supported out-of-band as per RFC2833.


We currently support the following codecs:

  • G711a /A-law
  • G711u /μ-law