The SIP Parameter modification feature allow customers to add, remove, or modify the SIP parameters in the SIP messages going out of a border element. The SIP message is generated from the standard signaling stack, but runs the message through a parser which can add, delete or modify specific parameters. This allows interoperability with additional third party devices that require specific SIP message formats. All SIP methods and responses are supported, profiles can be added either in dial-peer level or global level. Basic Regular Expression support would be provided for modification of header values. SDP parameters can also be added, removed or modified.
This feature is applicable only for outgoing SIP messages. Changes to the messages are applied just before they are sent out, and the SIP SPI code does not remember the changes. Because there are no restrictions on the changes that can be applied, users must be careful when configuring this feature - for example, the call might fail if a regular expression to change the To tag value is configured.
In releases prior to Cisco IOS Release 15.1(3)S1, outgoing SIP messages used to have non-token characters in server and user-agent SIP headers. In Cisco IOS Release 15.1(3)S1 and later releases, server and user-agent SIP headers have only token characters. Token characters can be a alphanumeric character, hyphen (-), dot (.), exclamation mark (!), percent (%), asterisk (*), underscore (_), plus sign (+), grave (`), apostrophe ('), or a tilde (~).
The all keyword is used to apply rules on all requests and responses.