Internet DRAFT - draft-ietf-dime-priority-avps
draft-ietf-dime-priority-avps
Diameter Maintenance and K. Carlberg, Ed.
Extensions (DIME) G11
Internet-Draft T. Taylor
Intended status: Standards Track PT Taylor Consulting
June 28, 2012
Diameter Priority Attribute Value Pairs
draft-ietf-dime-priority-avps-06.txt
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Abstract
This document defines Attribute-Value Pair (AVP) containers for various
priority parameters for use with Diameter and the AAA framework. The
parameters themselves are defined in several different protocols that
operate at either the network or application layer.
1. Introduction
This document defines a number of Attribute-Value Pairs (AVP) that can
be used within the Diameter protocol [I-D.ietf-dime-rfc3588bis] 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 an extension 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 by-pass 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
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):
- Reservation-Priority AVP as defined in [ETSI]
- MPS-Identifier AVP as defined in [3GPPa]
- Priority-Level AVP (as part of the Allocation Retention Priority
AVP) as defined in [3GPPb]
- Session-Priority AVP as defined in [3GPPc][3GPPd]
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 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
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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 coexistance 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 RFC2119 [RFC2119].
3. Priority Parameter Encoding
This section defines a set of AVPs that correlate 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 [I-D.ietf-dime-rfc3588bis]. 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 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 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
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.
Dual-Priority ::= < AVP Header: TBD >
{ Preemption-Priority }
{ Defending-Priority }
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3.1.1. Preemption-Priority AVP
The Preemption-Priority AVP (AVP Code TBD) 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 TBD) 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 TBD) 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 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: TBD >
{ SIP-Resource-Priority-Namespace }
{ SIP-Resource-Priority-Value }
3.3.1. SIP-Resource-Priority-Namespace AVP
The SIP-Resource-Priority-Namespace AVP (AVP Code TBD) is of type
UTF8String. This AVP contains a string that identifies a unique ordered
set of priority values as described in [rfc4412].
3.3.2 SIP-Resource-Priority-Value AVP
The SIP-Resource-Priority-Value AVP (AVP Code TBD) 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].
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3.4. Application-Level-Resource-Priority AVP
The Application-Level-Resource-Priority (ALRP) AVP is a grouped AVP
consisting of two AVPs, the ALRP-Namespace AVP and the ALRP-Value AVP.
Application-Level-Resource-Priority ::= < AVP Header: TBD >
{ 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] provided
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 TBD) 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 TBD) 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:
An 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
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application can be admitted. If the decision is positive, the NAS
forwards the authorized QoS values as objects in RSVP signalling. In
particular, the values in the Dual-Priority AVP would be carried in the
Signaled Preemption Priority Policy Element defined in [RFC3181], and so
on. 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:
- which value to take if both Admission-Priority and Application-Level-
Resource-Priority are present;
- what namespace or namespaces are recognized for use in
Application-Level-Resource-Priority;
- which resources are subject to pre-emption 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 would be accepted and what
the effect of a given priority level would be on the admission decision.
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.
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5. IANA Considerations
5.1. AVP Codes
IANA is requested to allocate AVP codes for the following AVPs that are
defined in this document.
+------------------------------------------------------------------+
| AVP Section |
|AVP Name Code Defined Data Type |
+------------------------------------------------------------------+
|Dual-Priority TBD 3.1 Grouped |
|Preemption-Priority TBD 3.1.1 Unsigned16 |
|Defending-Priority TBD 3.1.2 Unsigned16 |
|Admission-Priority TBD 3.2 Unsigned8 |
|SIP-Resource-Priority TBD 3.3 Grouped |
|SIP-Resource-Priority-Namespace TBD 3.3.1 UTF8String |
|SIP-Resource-Priority-Value TBD 3.3.2 UTF8String |
|Application-Level-Resource-Priority TBD 3.4 Grouped |
|ALRP-Namespace TBD 3.4.1 Unsigned32 |
|ALRP-Value TBD 3.4.2 Unsigned32 |
+------------------------------------------------------------------+
5.2. QoS Profile
IANA is requested to allocate a new value from the Authentication,
Authorization, and Accounting (AAA) Parameters/QoS Profile registry
defined in [RFC5624] for the QoS profile defined in this document. The
name of the profile is "Resource priority parameters".
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 draft, 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 would be use of S/MIME with
SIP 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 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
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a single administrative domain or "walled garden", and thus possible
changes in values would reflect policies of that administrative domain.
The security considerations of the Diameter protocol itself are discussed
in [I-D.ietf-dime-rfc3588bis]. 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 should 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 draft 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, and Magnus Westerlund, David
Harrington, Robert Sparks, and Dan Romascanu for their review and/or
comments on previous versions of the draft.
8. References
8.1. Normative References
[I-D.ietf-dime-rfc3588bis]
Fajardo, V., Arkko, J., Loughney, J., and G. Zorn,
"Diameter Base Protocol", draft-ietf-dime-rfc3588bis-26
(work in progress), January 2011.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2205] Braden, B., et. al., "Resource ReSerVation Protocol (RSVP)
-- Version 1 Functional Specification", RFC 2205, September
1997
[RFC3181] Herzog, S., "Signaled Preemption Priority Policy Element",
RFC 3181, October 2001.
[RFC4412] Schulzrinne, H. and J. Polk, "Communications Resource
Priority for the Session Initiation Protocol (SIP)",
RFC 4412, February 2006.
[RFC5624] Korhonen, J., Tschofenig, H., and E. Davies, "Quality of
Service Parameters for Usage with Diameter", RFC 5624,
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Aug 2009.
[RFC5866] Sun, D., et. al., "Diameter Quality-of-Service
Application", RFC 5866, May 2010.
[RFC6401] Faucheur, F., Polk, J., and K. Carlberg, "Resource
ReSerVation Protocol (RSVP) Extensions for Emergency
Services", RFC 6401, Oct 2011.
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
Authors' Addresses
Ken Carlberg (editor) Tom Taylor
G11 PT Taylor Consulting
1601 Clarendon Dr 1852 Lorraine Ave
Arlington, VA 22209 Ottawa
United States Canada
Email: carlberg@g11.org.uk Email: tom.taylor.stds@gmail.com
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