Call Direction

Identification of non-originating SIP calls may differ from network to network. The N2IWF allows for these to be identified when an INVITE is received.

Call direction identification configuration consists of selector rules defined in the DIRECTION LogicApp service global variable.

<global name="DIRECTION" type="array">
    <rule direction="terminating" var="is_term" value="1" />
    <rule direction="forwarding" header.forwarding="!" forwarder_uri_header="forwarding" />
</global>

Each rule must specify the direction of a call. Rules are applied in the order listed until a match is made.

The direction provided must be one of:

• originating to treat as the originating leg of a call (A calls B, paid for by A)
• forwarding to treat as forwarded leg of a call (A calls B who redirects to C, paid for by B)
• terminating to treat as terminating leg of a call (A calls B, paid for by B)

For forwarding call legs, an additional optional parameter forwarder_uri_header may be provided specifying a SIP header name that carries the redirecting party’s URI. If not provided, or the specified header is not available, the default forwarder URI header will be used.

If no rule applies, or none are configured, the call will be considered to be originating.

Note that for obvious reasons these rules should not use the originating, forwarding, and terminating specific selectors, as they will never match. Similarly, as protocol initiation occurs before variable population, selectors using variables in any way will not match.