The IESG has approved a request to register the "application/nss" MIME media type in the standards tree. This media type is a product of ITU-T Study Group 11. The IESG contact persons are Ted Hardie and Scott Hollenbeck. Type name: application Subtype name: nss Required parameters: none Optional parameters: charset Encoding considerations: binary (Note: Data is in US-ASCII range.) Security considerations: NSS has the potential to disclose private customer information and the potential for modification of NSS bodies during message transport to manipulate call setup, mid-call events, or call release. Modification means the addition of an NSS body where none existed, the removal of an NSS body where one existed, or the changing of contents of existing NSS bodies in messages. NSS can reveal information about telephone subscribers that is requested to remain private. Security mechanisms must be provided to meet privacy agreements and regulations. NSS can be deployed as an interdomain signaling mechanism and may be subject to trust relationships and agreements between administrative domains as well as legal requirements in various jurisdictions. NSS can affect routing of telephone calls and associated billing. Security mechanisms must be provided to control fraud, malicious intents, and unintended consequences. Such mechanisms include the ability to selectively filter or map and forward each information element within NSS upon entry or exit of an administrative domain. It is expected that nodes performing such functions will be User Agents, such as gateway nodes or IP-based Application servers acting on behalf of users. Note that RFC 3261 Section 16.6 says: "The proxy MUST NOT add to, modify, or remove the message body." That includes NSS bodies. All information from unauthenticated entities must be validated and authorized before being mapped and forwarded in subsequent signaling messages. Such checks are particularly needed when information is mapped to/from SIP headers. Note, however, that the intent of NSS is to carry data that would be mutually exclusive with the data capable of being carried in SIP headers. When encapsulated by SIP, the integrity and confidentiality of SIP messages containing NSS bodies must be addressed. SIP mandates that Transport Layer Security (TLS) must be supported. The Internet Protocol Security (IPSEC) mechanisms may be used as an alternative on signaling hops between nodes trusted to handle PSTN signaling. TLS and IPSEC are discussed in Section 26 of the Session Initiation Protocol RFC 3261. However, trusted nodes would need to specify and agree on the security suites to be used with IPSEC. See RFC 3324 for discussion on trust domains and related security requirements. When intermediate hops are not trusted, end-to-end integrity and confidentiality may be addressed using S/MIME: RFC 3850, "Secure/Multipurpose Internet Mail Extensions (S/MIME) Version 3.1 Certificate Handling", July 2004. RFC 3851, "Secure/Multipurpose Internet Mail Extensions (S/MIME) Version 3.1 Message Specification", July 2004. RFC 3852, "Cryptographic Message Syntax (CMS)", July 2004. RFC 3853, "S/MIME Advanced Encryption Standard (AES) Requirement for the Session Initiation Protocol (SIP)", July 2004. NSS MIME bodies should be secured using S/MIME to mitigate concerns with authentication of the sender, integrity protection during transit, and confidentiality protection from disclosure to unauthorized third parties. NSS endpoints must support S/MIME signatures and should support S/MIME encryption. For H.323-based encapsulation of NSS bodies, the security mechanisms of ITU-T Recommendation H.235, "Security and encryption for H-series (H.323 and other H.245-based) multimedia terminals", August 2003, must be used to provide integrity and confidentiality. NSS consists of well defined message types and parameters. Arbitrary content or directives within field values is not permitted. NSS does not employ "active content." NSS contains fields which instruct whether privacy data such as calling party's number is to be presented or restricted. NSS is used without and is silent about compression. Use of compression in conjunction with NSS does not present any security issues. Interoperability considerations: Compatibility mechanisms are defined in Q.1980.1. Published specification: ITU-T Recommendation Q.1980.1, "The Narrowband Signalling Syntax (NSS) - Syntax Definition", December 2004. Link: http://www.itu.int/rec/recommendation.asp?type=folders&lang=e&parent=T-REC-Q .1980.1 Applications which use this media type: Applications in PSTN Gateways and call control application servers. Additional Information: Magic numbers: None File Extensions: None Macintosh File Type Codes: None Object Identifiers: {itu-t(0) recommendation(0) q(17) 1980 1} (0.0.17.1980.1) See ITU-T Recommendation H.323 Annex M.4 "Tunneling of Narrowband Signalling Syntax (NSS) for H.323", December 2004. Person to contact for further information: Name: Michael Hammer E-Mail: mhammer@cisco.com Intended Usage: COMMON Restrictions on usage: None Author: ITU-T Study Group 11 Change controller: ITU-T Study Group 11 _______________________________________________ IETF-Announce@ietf.org https://www1.ietf.org/mailman/listinfo/ietf-announce
