This media type is defined by the following information:
Media type name: application Media subtype name: ISUP Required parameters: version Optional parameters: base Encoding scheme: binary Security considerations: See section 5.
The ISUP message is encapsulated beginning with the Message Type Code (i.e., omitting Routing Label and Circuit ID Code).
The use of the 'version' parameter allows network administrators to identify specific versions of ISUP that will be exchanged on a bilateral basis. This enables a particular client such as a SoftSwitch/Media Gateway Controller to recognize and parse the message correctly, or (possibly) to reject the message if the specified ISUP version is not supported. This specification places no constraints on the values that may be used in 'version'; these are left to the discretion of the network administrator.
This 'version' could, for example, be used to identify a network- specific implementation of ISUP, e.g., X-NetxProprietaryISUPv3, or to identify a well-known standard version of ISUP, e.g., itu-t or ansi.
A 'base' parameter can optionally be included in some cases (e.g., if the receiver may not recognize the 'version' string) to specify that the encapsulated ISUP can also be processed using the identified 'base' specification. Table 1 provides a list of 'base' values supported by the 'application/ISUP' media type, including whether or not the forward compatibility mechanism defined in ITU-T 1992 ISUP is supported.
Table 1: ISUP 'base' values
base protocol compatibility
itu-t88 ITU-T Q.761-4 (1988) no
itu-t92+ ITU-T Q.761-4 (1992) yes
ansi88 ANSI T1.113-1988 no
ansi00 ANSI T1.113-2000 yes
etsi121 ETS 300 121 no
etsi356 ES 300 356 yes
gr317 BELLCORE GR-317 no
ttc87 JT-Q761-4(1987-1992) no
ttc93+ JT-Q761-4(1993-) yesThe Content-Disposition header [5] may be included to describe how the encapsulated ISUP is to be processed, and in particular what the handling should be if the received Content-Type is not recognized. The default disposition-type for an ISUP message body is "signal". This type indicates that the body part contains signaling information associated with the session, but does not describe the session.
Supplementing the description of the Content-Disposition header in [5], as well as any characterization of the Content-Disposition header in the SIP standard, is the following BNF describing disposition-types and disposition-params that may be used in the header of ISUP and QSIG MIME bodies.
Content-Disposition = "Content-Disposition" ":"
disposition-type *( ";" disposition-param )
disposition-type = "signal" | disp-extension-token
disposition-param = "handling" "="
( "optional" | "required" | other-handling )
| generic-param
other-handling = token
disp-extension-token = token; 編註: generic-param の定義は RFC 3204 にはなし。
A full definition of the use of the "handling" parameter is given in
the IANA Considerations section below. The following is how a
typical header would look ('base' may be omitted): Content-Type: application/ISUP; version=nxv3; base=etsi121
Content-Disposition: signal; handling=optionalThis document registers the "application/ISUP" and "application/QSIG" MIME media types.
Registrations for the 'version' symbols used within the ISUP and QSIG MIME types must specify a definitive specification reference, identifying a particular issue of the specification, to which the new symbol shall refer. Identifying a definite specification reference requires a review process; the authors recommend that a subject matter expert be designated as described in RFC 2434 [6] under Expert Review.
Note that where a specification is fully peer-to-peer backwards compatible with a previous issue (i.e., the compatibility mechanism is supported by both), then there is no need for separate symbols to be registered. The symbol for the original specification should be used to identify backwards-compatible upgrades of that specification as well.
Symbols beginning with the characters 'X-' are reserved for non- standard usage (e.g., cases in which a token other than a string representing an issue of an ISUP specification is appropriate for characterizing ISUP within an administrative domain). Such non- standard version can only be transmitted between administrative domains in accordance with a bilateral agreement. These symbols should be administered under the Private Use policy described in RFC 2434.
This document registers a new disposition-type for the Content- Disposition header, 'signal', to be used when a MIME body contains supplemental signaling information (ISUP and QSIG as MIME bodies being examples of this).
This document also defines a Content Disposition parameter, "handling". The handling parameter, handling-parm, describes how the UAS should react if it receives a message body whose content type or disposition type it does not understand. If the parameter has the value "optional", the UAS MUST ignore the message body; if it has the value "required", the UAS MUST return 415 (Unsupported Media Type). If the handling parameter is missing, the value "required" is to be assumed.