{+Internet Engineering Task Force A. Johnston Internet Draft D. Rawlins Document: draft-johnston-sip-osp-token-04.txt H. Sinnreich February 2003 WorldCom Expires: August 2003 Stephen Thomas Wave7 Optics Richard Brennan Telxxis LLC Session Initiation Protocol Private Extension for an OSP Authorization Token Status of this Memo+} This {+document is an+} Internet-Draft [-has been deleted. Unrevised documents placed-] {+and is+} in {+full conformance with all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of+} the {+Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts.+} Internet-Drafts [-directories have-] {+are draft documents valid for+} a maximum [-life-] of six [-months. After that time, they are deleted. This-] {+months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of+} Internet-Draft [-was not published-] {+Shadow Directories can be accessed at http://www.ietf.org/shadow.html. Abstract This draft proposes a private extension to the Session Initiation Protocol (SIP) for carrying OSP (Open Settlements Protocol) authorization tokens in applications such+} as {+clearinghouses. Johnston, et al. Expires - August 2003 [Page 1] Internet-Draft SIP Extension for OSP Auth Token February 2003 Table of Contents 1. Introduction...................................................2 2. Terminology....................................................3 3. Design Alternatives............................................3 4. Header Field Definition........................................4 5. Protocol Semantics.............................................4 5.1 User Agents................................................5 5.2 Proxies....................................................5 6. Example Message................................................5 IANA Considerations...............................................6 Security Considerations...........................................6 Normative References..............................................6 Informative References............................................7 Authors' Addresses................................................7 1. Introduction The problem of interdomain IP telephony calls with QoS is+} an [-RFC. Internet-Drafts-] {+important problem being addressed using AAA protocols. The new private SIP [1] header proposed here is part of an approach to solving this problem, which is summarized briefly here. Interdomain IP telephony is accomplished today using clearinghouse services and a mix of proprietary and standard AAA protocols. Making calls with AAA support between service providers that+} are [-not-] {+affiliated to different clearinghouses is a difficult problem. Beyond IP telephony it is also desirable to have a consistent AAA approach for all applications on the Internet. Work on a general architecture for AAA is proceeding in the IETF AAAarch research group. A framework and examples have been developed for various Internet applications. At the same time, Internet telephone calls can be set up with QoS and security. Since QoS is a valuable network resource, it requires AAA and possibly payments. We propose to use existing IETF protocols and proposals in Internet Drafts for interdomain IP telephony calls with QoS as a first step toward a uniform AAA approach. The approach outlined here may be useful later for developing a uniform AAA architecture and protocols for other application layer services. Figure 1 shows the model for+} an [-archival document series,-] {+interdomain phone call across the Internet with the various entities having business relationships, but not necessarily trust relationships with their correspondents: Johnston, et al. Expires - August 2003 [Page 2] Internet-Draft SIP Extension for OSP Auth Token February 2003 Clearinghouse +------+------+ +------+ +------+------+ |Policy| OSP | OSP | OSP | OSP | OSP |Policy| |Server|Client|<--->|Server|<--->|Client|Server| +------+------+ +------+ +------+------+ | | | | Domain 1 | +-----+ +----+ | Domain 2 | | | | +-----+ | | +-----+ | PEP | | | | PEP | +-----+ +-----+ | | +-----+ +-----+ | SIP |SIP | SIP | | | | SIP |SIP | SIP | | UAC |<-->|Proxy|-------SIP INVITE with OSP Token-->|Proxy|<-->| UAS | +-----+ +-----+ | | +-----+ +--+--+ | | | | | | SIP | | | Phone +------+ +------+ +--+--+ +------+ | Edge | RSVP | Edge | | | | RSVP | RSVP |Router| tunnel |Router| RSVP | MG | | Host |<-------->| |<---------------->| |<---------->| | +------+ +------+ Transit Nets +------+ +-----+ Figure 1: Model for interdomain QoS phone call While this approach to interdomain authorization is not a complete one, it is currently used today by IP telephony carriers+} and [-expired drafts,-] {+is useful in limited applications+} such as {+in a clearinghouse. As such, it is appropriate for the header field extension to SIP be registered as a private SIP header per the SIP change process [3]. 2. Terminology In+} this [-one,-] {+document, the key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL"+} are [-not available; please do not ask-] {+to be interpreted as described in RFC 2119 [2] and indicate requirement levels+} for [-copies... they-] {+compliant SIP caller preferences implementations. 3. Design Alternatives The OSP Token is an opaque string to SIP which must be carried in the INVITE passed between domains. As such, the Token could be carried as a MIME attachment. However, there+} are {+three issues with this: - Since the Token must be carried with the SDP, the INVITE would Johnston, et al. Expires - August 2003 [Page 3] Internet-Draft SIP Extension for OSP Auth Token February 2003 need to have a multipart MIME message body. If either User Agents do+} not [-available.-] {+support multipart MIME, the call will fail. -+} The [-Secretariat does not-] {+Token is used by both proxies and User Agents. As such, the proxy would+} have {+to decode the multipart MIME message body to extract the token. The general design of SIP is for message bodies to contain information of interest to end-points only, with+} information {+needed by proxies contained in headers. - Multipart MIME encoding/decoding adds more delay to an already lengthy call setup procedure,+} as {+compared+} to [-future plans-] {+header processing. For these reasons, a new SIP header is proposed instead+} of {+a new MIME type for OSP authorization tokens. Note that since OSP tokens are commonly constructed according to Cryptographic Message Syntax [3], their size may depend on+} the [-authors or working groups WRT-] {+size of X.509 certificates embedded in+} the [-deleted Internet-Draft.-] {+CMS format.+} For [-more information-] {+this reason, entities using this header MUST NOT use UDP for transport. Instead TLS SHOULD be used. In addition, it is recommended that systems use the abbreviated token format described in Annex D of [4]. 4. Header Field Definition The table below specifies an extension of Table 2 in RFC 3261 [1] for the new header defined here. where proxy ACK BYE CAN INV OPT REG P-OSP-Auth-Token R ad - - - o - - P-OSP-Auth-Token 2xx ad - - - o - - The "where" column describes the request and response types with which the header filed can be used. "R" indicates a request header, a numeric value in the "where" column indicates the status code the header field is used with. The "proxy" column describes whether this message header field MAY be added, "a",+} or {+deleted, "d", by+} a [-copy-] {+proxy server. In the method columns, "o" means optional and "-" means not applicable. The Augmented BNF for the header field (using the form and definitions in Section 25+} of {+RFC 3261) is: P-OSP-Auth-Token = "P-OSP-Auth-Token" HCOLON token 5. Protocol Semantics The OSP Token is always encoded per base64 and only allowed in INVITE requests and 200 OK responses to INVITEs. Johnston, et al. Expires - August 2003 [Page 4] Internet-Draft SIP Extension for OSP Auth Token February 2003 5.1 User Agents A UAC MAY include+} the [-document, contact-] {+header an INVITE requesting QoS using AAA. If present in an INVITE, an AAA/QoS UAS MAY validate+} the [-author directly. Draft Author(s):-] {+token. If it is absent or present in the INVITE, an AAA/QoS UAS MAY include the header field in a 200 OK answer. A UAC MAY validate the token received in a 200 OK response to an INVITE. 5.2 Proxies A proxy participating in the AAA exchange may add, delete, examine or validate the token. Otherwise, the header field is ignored. 6. Example Message This SIP INVITE message is an example exchange between the two domains as shown in Figure 1: INVITE sips:+1-972-555-5555@domain2.com;user=phone SIP/2.0 Via: SIP/2.0/TLS proxy.domain1.com:5061;branch=z9hG4bK3a56d3.1 Via: SIP/2.0/TLS phone1.domain1.com:5061;branch=z9hG4bK3a5654 ;received=192.0.2.1 Max-Forward: 69 From: Alice ;tag=3 To: Call-ID: 123456@domain1.com CSeq: 1 INVITE Contact: Record-Route: P-OSP-Auth-Token: "YT64VqpfyF467GhIGfHfYT6jH77n8HHGghyHhHUujhJh756t HGTrfvbnjn8HHGTrfvhJhjH776tbB9HG4VQbnj7567GhIGfH 6ghyHhHUujpfyF47GhIGfHfYT64VQbnj" Content-Type: application/sdp Content-Length: 184 v=0 o=alice 9735285123 9721273312 IN IP4 phone1.domain1.com s=- c=IN IP4 phone1.domain1.com t=0 0 m=audio 9876 RTP/AVP 0 a=rtpmap: 0 PCMU/8000 Johnston, et al. Expires - August 2003 [Page 5] Internet-Draft SIP Extension for OSP Auth Token February 2003 a=qos:mandatory recv confirm IANA Considerations Registration of "P-OSP-Auth-Token" SIP header field This document defines a new private SIP header field, "P-OSP-Auth- Token". As recommended by the policy of the Transport Area [3], this header should be registered by the IANA in the SIP header registry, using the RFC number of this document as its reference. Name of Header: P-OSP-Auth-Token Short form: None Registrant: Alan Johnston alan.johnston@wcom.com Normative description: This document Security Considerations The security and handling of OSP tokens is covered in [4] which includes encryption and the use of IPSec. The P-OSP-Auth-Token header field may be protected using standard SIP mechanisms such as TLS transport and/or S/MIME encryption as detailed in [1]. Normative References [1] J. Rosenberg,+} H. [-Sinnreich: henry.sinnreich@mci.com-] {+Schulzrinne, G. Camarillo, A. Johnston, J. Peterson, R. Sparks, M. Handley, and E. Schooler, "SIP: Session Initiation Protocol," Request for Comments (Proposed Standard) 3261, Internet Engineering Task Force, June 2002. [2] S. Bradner, "Key words for use in RFCs to indicate requirement levels," Request for Comments (Best Current Practice) 2119, Internet Engineering Task Force, March 1997. [3] R. Housley, "Cryptographic Message Syntax", RFC 2630, June 1999. [4] European Telecommunications Standards Institute. "Telecommunications and Internet Protocol Harmonization Over Networks (TIPHON); Open Settlement Protocol (OSP) for Inter- domain pricing, authorization, and usage exchange". Technical Specification 101 321. Version 2.1.0. Johnston, et al. Expires - August 2003 [Page 6] Internet-Draft SIP Extension for OSP Auth Token February 2003 Informative References [5]+} A. [-Johnston: alan@stallion.oz.au-] {+Mankin,+} S. [-Thomas: stephen.thomas@transnexus.com-] {+Bradner, R. Mahy,+} D. [-Rawlins: diana.rawlins@mci.com-] {+Willis, J. Ott, and B. Rosen, "Change Process for the Session Initiation Protocol (SIP),"IETF Internet-Draft, Work in Progress, August 2002. Authors' Addresses Alan Johnston WorldCom 100 S. 4th Street St. Louis, Missouri 63104 alan.johnston@wcom.com Henry Sinnreich WorldCom 400 International Parkway Richardson, Texas 75081 USA henry.sinnreich@wcom.com Diana Rawlins WorldCom 901 International Parkway Richardson, Texas 75081 USA diana.rawlins@wcom.com Stephen Thomas Wave7 Optics 1075 Windward Ridge Parkway Alpharetta, GA 30005 USA stephen.thomas@wave7optics.com Richard Brennan Telxxis LLC 1670 South Amphlett Blvd. Suite 214, No. 1018 San Mateo, CA 94402-2511 USA rbrennan@telxxis.com Intellectual Property Statement Johnston, et al. Expires - August 2003 [Page 7] Internet-Draft SIP Extension for OSP Auth Token February 2003 The IETF takes no position regarding the validity or scope of any intellectual property or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; neither does it represent that it has made any effort to identify any such rights. Information on the IETF's procedures with respect to rights in standards-track and standards-related documentation can be found in BCP-11. Copies of claims of