OSP Token

Home \ OSP Toolkit \ OSP Token

OSP Token

Download file: draft-johnston-sip-osp-token-06.txt

Internet Engineering Task Force A. Johnston

Internet Draft D. Rawlins

Document: draft-johnston-sip-osp-token-06.txt H. Sinnreich

June 2004 MCI

Expires: December 2004 Stephen Thomas

Wave7 Optics

Richard Brennan

Telxxis LLC

Session Initiation Protocol Private Extension for an

OSP Authorization Token

Status of this Memo

By submitting this Internet-Draft, I certify that any applicable

patent or other IPR claims of which I am aware have been disclosed,

and any of which I become aware will be disclosed, in accordance with

RFC 3668.

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 are draft documents valid for a maximum of six 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 Shadow Directories can be accessed at

http://www.ietf.org/shadow.html.

Abstract

This document discusses 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 ?ember 2004 [Page 1]

Internet-Draft SIP Extension for OSP Auth Token June 2004

Table of Contents

1. Introduction...................................................2

2. Terminology....................................................3

3. Design Alternatives............................................3

4. Header Field Definition........................................4

5. Protocol Semantics.............................................5

5.1 User Agents................................................5

5.2 Proxies....................................................5

6. Example Message................................................5

7. 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

important problem being addressed using AAA protocols. The new

private SIP [1] header field 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 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.

This draft documents a proprietary SIP extension header field that

may be used to exchange open settlements protocol [4] information in

the context of a SIP session establishment. 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 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 ?ember 2004 [Page 2]

Internet-Draft SIP Extension for OSP Auth Token June 2004

Clearinghouse

+------+------+ +------+ +------+------+

|Policy| OSP | OSP | OSP | OSP | OSP |Policy|

+------+------+ +------+ +------+------+

| | | |

Domain 1 | +-----+ +----+ | Domain 2

| | | |

+-----+ | | +-----+

| PEP | | | | PEP |

+-----+ +-----+ | | +-----+ +-----+

| SIP |SIP | SIP | | | | SIP |SIP | SIP |

| UAC |<-->|Proxy|-------SIP INVITE with OSP Token-->|Proxy|<-->| UAS |

+-----+ +-----+ | | +-----+ +--+--+

| | |

SIP | | |

Phone +------+ +------+ +--+--+

| Host |<-------->| |<---------------->| |<---------->| |

+------+ +------+ +------+ +-----+

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 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 field per the SIP change process [5]. Note

that while RSVP [6] is shown, its use is not required by this

extension.

2. Terminology

In this document, the key words "MUST", "MUST NOT", "REQUIRED",

"SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",

and "OPTIONAL" are to be interpreted as described in RFC 2119 [2] and

indicate requirement levels for 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 ?ember 2004 [Page 3]

Internet-Draft SIP Extension for OSP Auth Token June 2004

need to have a multipart MIME message body. If either User Agents

do not support multipart MIME, the call will fail.

- The 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 header fields.

- Multipart MIME encoding/decoding adds more delay to an already

lengthy call setup procedure, as compared to header field

processing.

For these reasons, a new SIP header field 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 size

of X.509 certificates embedded in the CMS format. For this reason,

entities using this header field 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 field defined here.

where proxy ACK BYE CAN INV OPT REG

P-OSP-Auth-Token R ad - - - o - -

P-OSP-Auth-Token 18x,2xx ad - - - o - -

The "where" column describes the request and response types with

which the header field can be used. "R" indicates a request header

field, 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 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 *(SEMI osp-param)

osp-param = realm / generic-param

realm = "realm" EQUAL realm-value

realm-value = quoted-string

Johnston, et al. Expires ?ember 2004 [Page 4]

Internet-Draft SIP Extension for OSP Auth Token June 2004

5. Protocol Semantics

The OSP Token is always encoded per base64 and only allowed in INVITE

requests, 200 OK responses to INVITEs, and reliable provisional

responses to INVITEs.

5.1 User Agents

A UAC MAY include the header field an INVITE requesting QoS using

AAA.

If present in an INVITE, an AAA/QoS UAS MAY validate the token.

If it is absent or present in the INVITE, an AAA/QoS UAS MAY include

the header field in a reliable provisional response or 200 OK answer.

A UAC MAY validate the token received in a 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:+ This e-mail address is being protected from spambots. You need JavaScript enabled to view it. ;user=phone SIP/2.0

Via: SIP/2.0/TLS proxy.domain1.example.com:5061;branch=z9hG4bK3a5d3.1

Via: SIP/2.0/TLS phone1.domain1.example.com:5061;branch=z9hG4bK3a5654

;received=192.0.2.1

Max-Forward: 69

From: Alice <sips: This e-mail address is being protected from spambots. You need JavaScript enabled to view it. >;tag=3

To: <sips:+ This e-mail address is being protected from spambots. You need JavaScript enabled to view it. ;user=phone>

Call-ID: This e-mail address is being protected from spambots. You need JavaScript enabled to view it.

CSeq: 1 INVITE

Contact: <sips: This e-mail address is being protected from spambots. You need JavaScript enabled to view it. >

Record-Route: <sips:proxy.domain1.example.com;lr>

P-OSP-Auth-Token: "YT64VqpfyF467GhIGfHfYT6jH77n8HHGghyHhHUujhJh756t

HGTrfvbnjn8HHGTrfvhJhjH776tbB9HG4VQbnj7567GhIGfH

6ghyHhHUujpfyF47GhIGfHfYT64VQbnj";realm="domain1.example.com" Content-Type: application/sdp Content-Length: 184 v=0 o=alice 9735285123 9721273312 IN IP4 phone1.domain1.example.com s=- Johnston, et al. Expires ?ember 2004 [Page 5] Internet-Draft SIP Extension for OSP Auth Token June 2004 c=IN IP4 phone1.domain1.example.com t=0 0 m=audio 9876 RTP/AVP 0 a=rtpmap: 0 PCMU/8000 a=qos:mandatory recv confirm 7. 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 [5], this

header field should be registered by the IANA in the SIP header field

registry, using the RFC number of this document as its reference.

Name of Header field: P-OSP-Auth-Token

Short form: None

Registrant: Alan Johnston

This e-mail address is being protected from spambots. You need JavaScript enabled to view it.

Normative description: This document

Security Considerations

The security and handling of OSP tokens is covered in [4] which

includes encryption and 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].

Since the threats analyzed in the OSP document include ones in which

the token is carried in plain text and available to an attacker,

carrying the token in SIP does not introduce any new attacks.

Normative References

[1] J. Rosenberg, H. 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.

Johnston, et al. Expires ?ember 2004 [Page 6]

Internet-Draft SIP Extension for OSP Auth Token June 2004

[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.

Informative References

[5] A. Mankin, S. Bradner, R. Mahy, D. Willis, J. Ott, and B. Rosen,

"Change Process for the Session Initiation Protocol (SIP),"

Request for Comments (Proposed Standard) 3427, Internet

Engineering Task Force, December 2002.

[6] R. Braden, Ed., L. Zhang, S. Berson, S. Herzog, S. Jamin,

"Resource ReSerVation Protocol (RSVP) -- Version 1 Functional

Specification," Request for Comments (Proposed Standard) 2205,

Internet Engineering Task Force, October 1997.

Authors' Addresses

Alan Johnston

MCI

100 S. 4th Street

St. Louis, Missouri 63102

USA

This e-mail address is being protected from spambots. You need JavaScript enabled to view it.

Henry Sinnreich

MCI

400 International Parkway

Richardson, Texas 75081

USA

This e-mail address is being protected from spambots. You need JavaScript enabled to view it.

Diana Rawlins

MCI

901 International Parkway

Richardson, Texas 75081

USA

This e-mail address is being protected from spambots. You need JavaScript enabled to view it.

Stephen Thomas

Wave7 Optics

1075 Windward Ridge Parkway

Alpharetta, GA 30005

USA

This e-mail address is being protected from spambots. You need JavaScript enabled to view it.

Richard Brennan

Johnston, et al. Expires ?ember 2004 [Page 7]

Internet-Draft SIP Extension for OSP Auth Token June 2004

Telxxis LLC

1670 South Amphlett Blvd.

Suite 214, No. 1018

San Mateo, CA 94402-2511

USA

This e-mail address is being protected from spambots. You need JavaScript enabled to view it.

Intellectual Property Statement

The IETF takes no position regarding the validity or scope of any

Intellectual Property Rights 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; nor does it represent that it has

made any independent effort to identify any such rights. Information

on the procedures with respect to rights in RFC documents can be

found in BCP 78 and BCP 79.

Copies of IPR disclosures made to the IETF Secretariat and any

assurances of licenses to be made available, or the result of an

attempt made to obtain a general license or permission for the use of

such proprietary rights by implementers or users of this

specification can be obtained from the IETF on-line IPR repository at

http://www.ietf.org/ipr.

The IETF invites any interested party to bring to its attention any

copyrights, patents or patent applications, or other proprietary

rights that may cover technology that may be required to implement

this standard. Please address the information to the IETF at

This e-mail address is being protected from spambots. You need JavaScript enabled to view it. .

Disclaimer of Validity

This document and the information contained herein are provided on an

"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS

OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET

ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,

INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE

INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED

WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

to the rights, licenses and restrictions contained in BCP 78, and

except as set forth therein, the authors retain all their rights.

Johnston, et al. Expires ?ember 2004 [Page 8]

Internet-Draft SIP Extension for OSP Auth Token June 2004

Acknowledgment

Funding for the RFC Editor function is currently provided by the

Internet Society.

Johnston, et al. Expires ?ember 2004 [Page 9]

TransNexus Resources

TransNexus, OSP Nexus, NexOSS, SDReporter, ClearIP, OSP Secured, NexTransit, Nex1, LookAhead Routing, PeeringHouse, Peering Engine, NexAudit, OSPrey, OSP Toolkit & RAMS are trademarks of TransNexus, Inc. Patents: US 6,426,955; AU 748468; SG 200001336-7; IL 135131; UK 1016261; US 6,665,271; US 6,205,211; US 6,751,652; US 6,426,955; US 6,996,093; CA 2,304,214; US 7,203,956; US 7,743,263