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rfc:rfc6735

Internet Engineering Task Force (IETF) K. Carlberg, Ed. Request for Comments: 6735 G11 Category: Standards Track T. Taylor ISSN: 2070-1721 PT Taylor Consulting

                                                          October 2012
              Diameter Priority Attribute-Value Pairs

Abstract

 This document defines Attribute-Value Pair (AVP) containers for
 various priority parameters for use with Diameter and the
 Authentication, Authorization, and Accounting (AAA) framework.  The
 parameters themselves are defined in several different protocols that
 operate at either the network or application layer.

Status of This Memo

 This is an Internet Standards Track document.
 This document is a product of the Internet Engineering Task Force
 (IETF).  It represents the consensus of the IETF community.  It has
 received public review and has been approved for publication by
 the Internet Engineering Steering Group (IESG).  Further
 information on Internet Standards is available in Section 2 of
 RFC 5741.
 Information about the current status of this document, any
 errata, and how to provide feedback on it may be obtained at
 http://www.rfc-editor.org/info/rfc6735.

Copyright Notice

 Copyright (c) 2012 IETF Trust and the persons identified as the
 document authors.  All rights reserved.
 This document is subject to BCP 78 and the IETF Trust's Legal
 Provisions Relating to IETF Documents
 (http://trustee.ietf.org/license-info) in effect on the date of
 publication of this document.  Please review these documents
 carefully, as they describe your rights and restrictions with respect
 to this document.  Code Components extracted from this document must
 include Simplified BSD License text as described in Section 4.e of
 the Trust Legal Provisions and are provided without warranty as
 described in the Simplified BSD License.

Carlberg & Taylor Standards Track [Page 1] RFC 6735 Resource Priorities AVPs October 2012

 This document may contain material from IETF Documents or IETF
 Contributions published or made publicly available before November
 10, 2008.  The person(s) controlling the copyright in some of this
 material may not have granted the IETF Trust the right to allow
 modifications of such material outside the IETF Standards Process.
 Without obtaining an adequate license from the person(s) controlling
 the copyright in such materials, this document may not be modified
 outside the IETF Standards Process, and derivative works of it may
 not be created outside the IETF Standards Process, except to format
 it for publication as an RFC or to translate it into languages other
 than English.

1. Introduction

 This document defines a number of Attribute-Value Pairs (AVP) that
 can be used within the Diameter protocol [RFC6733] to convey a
 specific set of priority parameters.  These parameters are specified
 in other documents, but are briefly described below.  The
 corresponding AVPs defined in Section 3 are extensions to those
 defined in [RFC5866].  We note that all the priority fields
 associated with the AVPs defined in this document are extensible and
 allow for additional values beyond what may have already been defined
 or registered with IANA.
 Priority influences the distribution of resources and, in turn, the
 QoS associated with that resource.  This influence may be
 probabilistic, ranging between (but not including) 0% and 100%, or it
 may be in the form of a guarantee to either receive or not receive
 the resource.
 Another example of how prioritization can be realized is articulated
 in Appendix A.3 (the Priority Bypass Model) of [RFC6401].  In this
 case, prioritized flows may gain access to resources that are never
 shared with non-prioritized flows.

1.1. Other Priority-Related AVPs

 The 3rd Generation Partnership Project (3GPP) has defined several
 Diameter AVPs that support prioritization of sessions.  The following
 AVPs are intended to be used for priority services (e.g., Multimedia
 Priority Service):
  1. Reservation-Priority AVP as defined in [ETSI]
  2. MPS-Identifier AVP as defined in [3GPPa]
  3. Priority-Level AVP (as part of the Allocation Retention

Priority AVP) as defined in [3GPPb]

  1. Session-Priority AVP as defined in [3GPPc] and [3GPPd]

Carlberg & Taylor Standards Track [Page 2] RFC 6735 Resource Priorities AVPs October 2012

 Both the Reservation-Priority AVP and the Priority-Level AVP can
 carry priority levels associated with a session initiated by a user.
 We note that these AVPs are defined from the allotment set aside for
 3GPP for Diameter-based interfaces, and they are particularly aimed
 at IP Multimedia Subsystem (IMS) deployment environments.  The above
 AVPs defined by 3GPP are to be viewed as private implementations
 operating within a walled garden.  In contrast, the priority-related
 AVPs defined below in Section 3 are not constrained to IMS
 environments.  The potential applicability or use-case scenarios that
 involve coexistence between the above 3GPP-defined priority-related
 AVPs and those defined below in Section 3 is for further study.

2. Terminology and Abbreviations

 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
 document are to be interpreted as described in RFC 2119 [RFC2119].

3. Priority Parameter Encoding

 This section defines a set of AVPs that correlates to priority fields
 defined in other protocols.  This set of priority-related AVPs is for
 use with the Diameter QoS application [RFC5866] and represents a
 continuation of the list of AVPs defined in [RFC5624].  The syntax
 notation used is that of [RFC6733].  We note that the following
 subsections describe the prioritization field of a given protocol as
 well as the structure of the AVP corresponding to that field.
 We stress that neither the priority-related AVPs, nor the Diameter
 protocol, perform or realize the QoS for a session or flow of
 packets.  Rather, these AVPs are part of a mechanism to determine
 validation of the priority value.

3.1. Dual-Priority AVP

 The Dual-Priority AVP (AVP Code 608) is a grouped AVP consisting of
 two AVPs, the Preemption-Priority and the Defending-Priority AVP.
 These AVPs are derived from the corresponding priority fields
 specified in the "Signaled Preemption Priority Policy Element"
 [RFC3181] of RSVP [RFC2205].
 In [RFC3181], the Defending-Priority value is set when the
 reservation has been admitted by the RSVP protocol.  The Preemption-
 Priority field (described in [RFC3181]) of a newly requested
 reservation is compared with the Defending-Priority value of a
 previously admitted flow.  The actions taken based upon the result of
 this comparison are a function of local policy.

Carlberg & Taylor Standards Track [Page 3] RFC 6735 Resource Priorities AVPs October 2012

   Dual-Priority  ::= < AVP Header: 608 >
               { Preemption-Priority }
               { Defending-Priority }

3.1.1. Preemption-Priority AVP

 The Preemption-Priority AVP (AVP Code 609) is of type Unsigned16.
 Higher values represent higher priority.  The value encoded in this
 AVP is the same as the preemption-priority value that would be
 encoded in the signaled preemption priority policy element.

3.1.2. Defending-Priority AVP

 The Defending-Priority AVP (AVP Code 610) is of type Unsigned16.
 Higher values represent higher priority.  The value encoded in this
 AVP is the same as the defending-priority value that would be encoded
 in the signaled preemption priority policy element.

3.2. Admission-Priority AVP

 The Admission-Priority AVP (AVP Code 611) is of type Unsigned8.  The
 admission priority associated with an RSVP flow is used to increase
 the probability of session establishment for selected RSVP flows.
 Higher values represent higher priority.  A given admission priority
 is encoded in this information element using the same value as when
 encoded in the admission-priority parameter defined in Section 5.1 of
 [RFC6401].

3.3. SIP-Resource-Priority AVP

 The SIP-Resource-Priority AVP (AVP Code 612) is a grouped AVP
 consisting of two AVPs, the SIP-Resource-Priority-Namespace and the
 SIP-Resource-Priority-Value AVP, which are derived from the
 corresponding optional header fields in [RFC4412].
   SIP-Resource-Priority ::= < AVP Header: 612 >
                  { SIP-Resource-Priority-Namespace }
                  { SIP-Resource-Priority-Value }

3.3.1. SIP-Resource-Priority-Namespace AVP

 The SIP-Resource-Priority-Namespace AVP (AVP Code 613) is of type
 UTF8String.  This AVP contains a string that identifies a unique
 ordered set of priority values as described in [RFC4412].

Carlberg & Taylor Standards Track [Page 4] RFC 6735 Resource Priorities AVPs October 2012

3.3.2. SIP-Resource-Priority-Value AVP

 The SIP-Resource-Priority-Value AVP (AVP Code 614) is of type
 UTF8String.  This AVP contains a string (i.e., a namespace entry)
 that identifies a member of a set of priority values unique to the
 namespace.  Examples of namespaces and corresponding sets of priority
 values are found in [RFC4412].

3.4. Application-Level-Resource-Priority AVP

 The Application-Level-Resource-Priority (ALRP) AVP (AVP Code 615) is
 a grouped AVP consisting of two AVPs, the ALRP-Namespace AVP and the
 ALRP-Value AVP.
   Application-Level-Resource-Priority  ::= < AVP Header: 615 >
                                   { ALRP-Namespace }
                                   { ALRP-Value }
 A description of the semantics of the parameter values can be found
 in [RFC4412] and in [RFC6401].  The registry set up by [RFC4412]
 provides string values for both the priority namespace and the
 priority values associated with that namespace.  [RFC6401] modifies
 that registry to assign numerical values to both the namespace
 identifiers and the priority values within them.  Consequently, SIP-
 Resource-Priority and Application-Level-Resource-Priority AVPs convey
 the same priority semantics, but with differing syntax.  In the
 former case, an alpha-numeric encoding is used, while the latter case
 is constrained to a numeric-only value.

3.4.1. ALRP-Namespace AVP

 The ALRP-Namespace AVP (AVP Code 616) is of type Unsigned16.  This
 AVP contains a numerical value identifying the namespace of the
 application-level resource priority as described in [RFC6401].

3.4.2. ALRP-Value AVP

 The ALRP-Value AVP (AVP Code 617) is of type Unsigned8.  This AVP
 contains the priority value within the ALRP-Namespace, as described
 in [RFC6401].

4. Examples of Usage

 Usage of the Dual-Priority, Admission-Priority, and Application-
 Level-Resource-Priority AVPs can all be illustrated by the same
 simple network scenario, although they would not all typically be
 used in the same network.  The scenario is as follows:

Carlberg & Taylor Standards Track [Page 5] RFC 6735 Resource Priorities AVPs October 2012

 A user with special authorization is authenticated by a Network
 Access Server (NAS), which acts as a client to a Diameter Server
 supporting the user's desired application.  Once the user has
 authenticated, the Diameter Server provides the NAS with information
 on the user's authorized QoS, including instances of the Dual-
 Priority, Admission-Priority, and/or Application-Level-Resource-
 Priority AVPs.
 Local policy governs the usage of the values conveyed by these AVPs
 at the NAS to decide whether the flow associated with the user's
 application can be admitted.  If the decision is positive, the NAS
 forwards the authorized QoS values as objects in RSVP signaling.  In
 particular, the values in the Dual-Priority AVP would be carried in
 the "Signaled Preemption Priority Policy Element" defined in
 [RFC3181], and the values contained in the Admission-Priority and
 Application-Level-Resource-Priority AVPs would be carried in the
 corresponding policy objects defined in [RFC6401].  Each subsequent
 node would make its own decision taking account of the authorized QoS
 objects including the priority-related objects, again governed by
 local policy.  The example assumes that the user session terminates
 on a host or server in the same administrative domain as the NAS to
 avoid complications due to the restricted applicability of [RFC3181]
 and [RFC6401].
 Local policy might for example indicate:
  1. which value to take if both Admission-Priority and Application-

Level-Resource-Priority are present;

  1. which namespace or namespaces are recognized for use in

Application-Level-Resource-Priority;

  1. which resources are subject to preemption if the values in

Dual-Priority are high enough to allow it.

 A scenario for the use of the SIP-Resource-Priority AVP will differ
 slightly from the previous one, in that the initial decision point
 would typically be a SIP proxy receiving a session initiation request
 containing a Resource-Priority header field and deciding whether to
 admit the session to the domain.  Like the NAS, the SIP proxy would
 serve as client to a Diameter Server during the process of user
 authentication, and upon successful authentication would receive back
 from the Diameter Server AVPs indicating authorized QoS.  Among these
 might be the SIP-Resource-Priority AVP, the contents of which would
 be compared with the contents of the Resource-Priority header field.
 Again, local policy would determine which namespaces to accept and
 the effect of a given priority level on the admission decision.

Carlberg & Taylor Standards Track [Page 6] RFC 6735 Resource Priorities AVPs October 2012

 For the sake of our example, suppose now that the SIP proxy signals
 using RSVP to the border router that will be admitting the media
 flows associated with the session.  (This, of course, makes a few
 assumptions on routing and knowledge of that routing at the proxy.)
 The SIP proxy can indicate authorized QoS using various objects.  In
 particular, it can map the values from the Resource-Priority header
 field to the corresponding numeric values as defined by [RFC6401] and
 send it using the Application-Level Resource Priority Policy Element.

5. IANA Considerations

5.1. AVP Codes

 IANA has allocated AVP codes for the following AVPs that are defined
 in this document.
  +------------------------------------------------------------------+
  |                                       AVP  Section               |
  |AVP Name                               Code Defined   Data Type   |
  +------------------------------------------------------------------+
  |Dual-Priority                          608  3.1       Grouped     |
  |Preemption-Priority                    609  3.1.1     Unsigned16  |
  |Defending-Priority                     610  3.1.2     Unsigned16  |
  |Admission-Priority                     611  3.2       Unsigned8   |
  |SIP-Resource-Priority                  612  3.3       Grouped     |
  |SIP-Resource-Priority-Namespace        613  3.3.1     UTF8String  |
  |SIP-Resource-Priority-Value            614  3.3.2     UTF8String  |
  |Application-Level-Resource-Priority    615  3.4       Grouped     |
  |ALRP-Namespace                         616  3.4.1     Unsigned32  |
  |ALRP-Value                             617  3.4.2     Unsigned32  |
  +------------------------------------------------------------------+

5.2. QoS Profile

 IANA has allocated a new value from the "QoS Profiles" subregistry of
 the "Authentication, Authorization, and Accounting (AAA) Parameters"
 defined in [RFC5624] for the QoS profile defined in this document.
 The name of the profile is "Resource priority parameters" (1).

6. Security Considerations

 This document describes an extension for conveying quality-of-service
 information, and therefore follows the same security considerations
 of the Diameter QoS Application [RFC5866].  The values placed in the
 AVPs are not changed by this document, nor are they changed in the
 Diameter QoS application.  We recommend the use of mechanisms to
 ensure integrity when exchanging information from one protocol to an
 associated DIAMETER AVP.  Examples of these integrity mechanisms

Carlberg & Taylor Standards Track [Page 7] RFC 6735 Resource Priorities AVPs October 2012

 would be use of S/MIME with the SIP Resource Priority Header (RPH),
 or an INTEGRITY object within a POLICY_DATA object within the context
 of RSVP.  The consequences of changing values in the Priority AVPs
 may result in an allocation of additional or less resources.
 Changes in integrity-protected values SHOULD NOT be ignored, and
 appropriate protocol-specific error messages SHOULD be sent back
 upstream.  Note that we do not use the term "MUST NOT be ignored"
 because the local policy of an administrative domain associated with
 other protocols acts as the final arbiter.  In addition, some
 protocols associated with the AVPs defined in this document may be
 deployed within a single administrative domain or "walled garden";
 thus, possible changes in values would reflect policies of that
 administrative domain.
 The security considerations of the Diameter protocol itself are
 discussed in [RFC6733].  Use of the AVPs defined in this document
 MUST take into consideration the security issues and requirements of
 the Diameter base protocol.
 The authors also recommend that readers familiarize themselves with
 the security considerations of the various protocols listed in the
 Normative References.  This is because values placed in the AVPs
 defined in this document are set/changed by other protocols.

7. Acknowledgements

 We would like to thank Lionel Morand, Janet Gunn, Piers O'Hanlon,
 Lars Eggert, Jan Engelhardt, Francois LeFaucheur, John Loughney, An
 Nguyen, Dave Oran, James Polk, Martin Stiemerling, Magnus Westerlund,
 David Harrington, Robert Sparks, and Dan Romascanu for their review
 and/or comments on previous draft versions of this document.

8. References

8.1. Normative References

 [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
            Requirement Levels", BCP 14, RFC 2119, March 1997.
 [RFC2205]  Braden, R., Ed., Zhang, L., Berson, S., Herzog, S., and S.
            Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1
            Functional Specification", RFC 2205, September 1997.
 [RFC3181]  Herzog, S., "Signaled Preemption Priority Policy Element",
            RFC 3181, October 2001.

Carlberg & Taylor Standards Track [Page 8] RFC 6735 Resource Priorities AVPs October 2012

 [RFC4412]  Schulzrinne, H. and J. Polk, "Communications Resource
            Priority for the Session Initiation Protocol (SIP)", RFC
            4412, February 2006.
 [RFC5624]  Korhonen, J., Ed., Tschofenig, H., and E. Davies, "Quality
            of Service Parameters for Usage with Diameter", RFC 5624,
            August 2009.
 [RFC5866]  Sun, D., Ed., McCann, P., Tschofenig, H., Tsou, T., Doria,
            A., and G. Zorn, Ed., "Diameter Quality-of-Service
            Application", RFC 5866, May 2010.
 [RFC6401]  Le Faucheur, F., Polk, J., and K. Carlberg, "RSVP
            Extensions for Admission Priority", RFC 6401, October
            2011.
 [RFC6733]  Fajardo, V., Ed., Arkko, J., Loughney, J., and G. Zorn,
            Ed., "Diameter Base Protocol", RFC 6733, October 2012.

8.2. Informative References

 [3GPPa]   "TS 29.214: Policy and charging control over Rx reference
            point", 3GPP, March, 2011
 [3GPPb]   "TS 29.212: Policy and charging control over Gx reference
            point", 3GPP, October, 2010
 [3GPPc]   "TS 29.229: Cx and Dx interfaces based on the Diameter
            protocol; Protocol details", 3GPP, September, 2010
 [3GPPd]   "TS 29.329: Sh interface based on the Diameter protocol;
            Protocol details", 3GPP, September, 2010
 [ETSI]    "TS 183 017: Telecommunications and Internet Converged
            Services and Protocols for Advanced Networking (TISPAN);
            Resource and Admission Control", ETSI

Carlberg & Taylor Standards Track [Page 9] RFC 6735 Resource Priorities AVPs October 2012

Authors' Addresses

 Ken Carlberg (editor)
 G11
 1601 Clarendon Dr
 Arlington, VA 22209
 United States
 EMail: carlberg@g11.org.uk
 Tom Taylor
 PT Taylor Consulting
 1852 Lorraine Ave
 Ottawa
 Canada
 EMail: tom.taylor.stds@gmail.com

Carlberg & Taylor Standards Track [Page 10]

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