RFC 3204 (rfc3204) - Page 2 of 10

MIME media types for ISUP and QSIG Objects

RFC 3204               ISUP and QSIG MIME Objects          December 2001


   QSIG is the analogous signaling protocol used between private branch
   exchanges to support calls within private telephony networks.  There
   is a similar need to transport QSIG-encoded signaling information
   between SIP entities in some environments.

   This document is specific to this usage and would not apply to the
   transportation of ISUP or QSIG messages in other applications. These
   media types are intended for ISUP or QSIG application information
   that is used within the context of a SIP session, and not as general
   purpose transport of SCN signaling.

   The definition of media types for ISUP and QSIG application
   information does not address fully how the non-SIP and SIP entities
   exchanging messages determine or negotiate compatibility.  It is
   assumed that this is addressed by alternative means such as the
   configuration of the interworking functions.

   This is intended to be an IETF approved MIME type, and to be defined
   through an RFC.  NOTE: usage of Q.SIG within SIP is neither endorsed
   nor recommended as a result of this MIME registration.

3. Proposed new media types

   ISUP and QSIG messages are composed of arbitrary binary data that is
   transparent to SIP processing. The best way to encode these is to use
   binary encoding. This is in conformance with the restrictions imposed
   on the use of binary data for MIME (RFC 2045 [3]). It should be noted
   that the rules mentioned in the RFC 2045 apply to Internet mail
   messages and not to SIP  messages. Binary has been preferred over
   Base64 encoding because the latter would only result in adding bulk
   to the encoded messages and possibly be more costly in terms of
   processing power.

3.1 ISUP Media Type

   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).





Zimmerer, et al.            Standards Track