Restcomm provides an additional interface to communicate with an RCML/RVD application by means of custom SIP headers. The idea is that all custom SIP headers in a SIP message are detected and converted to HTTP parameters in the request to the RCML application using a convention. The RCML application can consume this parameters. Furthermore, RVD converts these parameters to RVD variables and makes them available to its modules.

RCML applications

The following conventions are followed:

  • Any SIP header starting with X- prefix is custom.

  • HTTP parameters are created out of each custom SIP header by adding the SipHeader_ prefix to its name.

Example mappings from SIP header names to HTTP parameter names:

X-My-Header -> SipHeader_X-My-Header

Thus the SipHeader_X-My-Header will be available as typical GET or POST parameter in the RCML application.

RVD applications

RVD will take the previous convention one step further and create an RVD variable out of the parameter. Thus, the mapping from a custom SIP header to an RVD variable will be the following:

X-My-Header -> $core_x_my_header

So, if X-My-Header SIP header arrives at Restcomm, RVD will have a variable named $core_x_my_header available in its modules. Note the following:

  • All characters are converted to lower case. This happens because although SIP headers are  not case insesitive while RVD variables are.

  • All non alpha numeric characters i.e. [^A-Za-z0-9_],  are converted to `_'  (underscore). That happens because RVD has some additional restrictions for naming variables. Here is the regular expression that is used for invalid characters to underscore: