When the original FROM URI is stored into the message for later recovery, a FROM parameter is used for this purpose. There is no standard/recommendation, so whatever parameter name can be set or sticked to the default one.
This parameter is optional, its default value being "vsf".
When performing FROM altering, there are three available ways to restore it to the original value in the sequential messages:
NO RESTORE (0): the original FROM values will not be saved at all, so no restore will be possible; this mode can be safely used against SIP UA which do not include FROM URI in transaction matching;
AUTO RESTORE (1): the original FROM values are saved in the FROM parameter. All modifications (restoring/changing) of FROM URI being made automatically by the module. Exception makes the changing of the FROM values within the dialog requests (CANCEL, BYE, re-INVITE) generated by UA client. This must be done explicitly from script similarly as for the original request;
MANUAL RESTORE (2): the original FROM values are saved in the FROM parameter, but the script must explicitly handle the restoring and changing of FROM URI in all sequential messages (requests and replies). Exceptions are the internally generated requests (like ACK and CANCEL) which will be generated with the correct FROM values.
This parameter is optional, its default value being 0 - NO RESTORE. Anyhow, it is strongly recommended to use the AUTO RESTORE mode if you don't have much experience.
Contains the description of one set of credentials (username, domain and password) used to perform UAC authentication.
The parameter allow more than one set of credentials to be defined.
Syntax:
credential = username ":" realm ":" password
This parameter is optional.