About MIME Rules

MIME rules (set up in the ACLI mime-rules configuration) operate much the same way that SIP header rules do. You can set parameters in the MIME rules that the Oracle® Enterprise Session Border Controller uses to match against specific SIP methods and message types. The system compares the search criteria against the body or body parts using the type of comparison you choose. Offering a variety of selection, you can pick kind of manipulation that suits your needs; the Oracle® Enterprise Session Border Controller then takes action with matching and new values to change the SIP message.

Note:

when you use the delete action on a multi-part MIME string that reduces a number of bodies down to one, the SIP message remains a multi-part MIME message with only one body part (and thereby avoids the header conflicting with the message itself).

You identify the MIMe rule by configuring a content type that refers to the specific body part on which to operate. For example, given a SIP Content-Type header with the value multipart/mixed;boundary=unique-boundary-1, you would enter a content-type value of application/sdp to manipulate specifically on the SDP portion of the SIP message. The Oracle® Enterprise Session Border Controller knows automatically if it is operating on SIP messages with single or multiple body parts, and the content-type setting applies to both kinds. And when making its comparison, the Oracle® Enterprise Session Border Controller matches the content-type of the body with regard to case (case insensitive), ignoring any header parameters.

Both for making comparisons against the body part and for new/replacement values, the Oracle® Enterprise Session Border Controller treats the match and new values you set for a MIME rule as ASCII strings. Therefor, a mime rule operating on a binary body part will yield an improper conversion of a new value with respect to the binary body part.

Within MIME rules, you configure MIME headers, which operate on the specific headers in the match body part of the SIP message. The Oracle® Enterprise Session Border Controller uses the MIME header name to run a string comparison to match the specific header in the message’s body part.

Using these rules, you can also manipulate the preamble—or the SIP message text that follows the headers but precedes the body separator. To do so, enter the keyword @preamble for the content type parameter in the MIME rule. Likewise you can manipulate the epilogue—or the text that follows the last body part after the last separator—using the keyword @epilogue.

Note that the ACLI limits character entries to 255 characters before the return character must be entered, but MIME parts can easily exceed this 255-character size. So you might need to enter a value larger that 255 characters. To do so, you start your entry (in the match-value or new-value parameters) with a plus sign (+). The plus sign instructs the system to add the string after it to the pre-existing match or new value. For the new-value parameter, the Oracle® Enterprise Session Border Controller checks the value immediately for validity. Be sure that when you are appending values to a new-value that the entire expression is valid at each point where strings are appended.