Diameter Priority Attribute-Value Pairs
Extracted elements (19)
SIP-Resource-Priority and ALRP AVPs convey the same priority semantics but with differing syntax: SIP-Resource-Priority uses alpha-numeric encoding from RFC 4412 namespaces, while ALRP is constrained to numeric-only values as assigned by RFC 6401. Both AVP sets are provided to serve different protocol environments.
The 3GPP-defined priority AVPs (Reservation-Priority, Priority-Level, Session-Priority) are aimed at IMS deployment environments and are considered private implementations within a walled garden. The priority AVPs defined in this RFC are explicitly not constrained to IMS environments.
The priority AVPs and the Diameter protocol do not 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. QoS realization is a separate concern.
The IANA table in Section 5.1 lists both ALRP-Namespace (AVP Code 616) and ALRP-Value (AVP Code 617) as type Unsigned32, while the body text in Sections 3.4.1 and 3.4.2 defines them as Unsigned16 and Unsigned8 respectively. This is an internal inconsistency in the RFC.
The potential coexistence or use-case scenarios involving 3GPP-defined priority AVPs (Reservation-Priority, MPS-Identifier, Priority-Level, Session-Priority) and the AVPs defined in this document is explicitly left for further study.
The priority AVPs defined here extend those defined in RFC 5866 (Diameter QoS Application) and continue the list from RFC 5624. All priority fields are extensible and allow for additional values beyond those already defined or registered with IANA.
Changes in integrity-protected priority AVP values SHOULD NOT be ignored, and appropriate protocol-specific error messages SHOULD be sent back upstream. The weaker 'SHOULD NOT' rather than 'MUST NOT' is used because local administrative domain policy acts as the final arbiter.
Use of the priority AVPs defined in this document MUST take into consideration the security issues and requirements of the Diameter base protocol as discussed in RFC 6733.
The Application-Level-Resource-Priority (ALRP) AVP (AVP Code 615) is a grouped AVP consisting of ALRP-Namespace (AVP Code 616) and ALRP-Value (AVP Code 617). It conveys the same priority semantics as SIP-Resource-Priority but uses numeric-only encoding rather than alpha-numeric.
The Dual-Priority AVP (AVP Code 608) is a grouped AVP consisting of Preemption-Priority and Defending-Priority AVPs, derived from the Signaled Preemption Priority Policy Element of RSVP (RFC 3181). It is used to convey RSVP preemption priority values within Diameter.
The SIP-Resource-Priority AVP (AVP Code 612) is a grouped AVP consisting of SIP-Resource-Priority-Namespace (AVP Code 613, UTF8String) and SIP-Resource-Priority-Value (AVP Code 614, UTF8String), derived from the corresponding optional header fields in RFC 4412.
IANA allocated a new value from the 'QoS Profiles' subregistry of the AAA Parameters registry (defined in RFC 5624). The new profile is named 'Resource priority parameters' with value 1.
IANA allocated AVP codes for ten new AVPs: Dual-Priority (608, Grouped), Preemption-Priority (609, Unsigned16), Defending-Priority (610, Unsigned16), Admission-Priority (611, Unsigned8), SIP-Resource-Priority (612, Grouped), SIP-Resource-Priority-Namespace (613, UTF8String), SIP-Resource-Priority-Value (614, UTF8String), Application-Level-Resource-Priority (615, Grouped), ALRP-Namespace (616), and ALRP-Value (617).
Integrity mechanisms SHOULD be used when mapping values from one protocol into Diameter priority AVPs. Examples include S/MIME with the SIP Resource Priority Header or an INTEGRITY object within a POLICY_DATA object in RSVP. Changes in priority values may result in allocation of additional or fewer resources.
The Admission-Priority AVP (AVP Code 611) is of type Unsigned8; higher values represent higher priority. It encodes the admission-priority parameter defined in Section 5.1 of RFC 6401 and is used to increase the probability of session establishment for selected RSVP flows.
The ALRP-Namespace AVP (AVP Code 616) is described as type Unsigned16 in Section 3.4.1, containing a numerical namespace identifier per RFC 6401. The ALRP-Value AVP (AVP Code 617) is described as type Unsigned8 in Section 3.4.2, containing the numeric priority value within the namespace.
The Defending-Priority AVP (AVP Code 610) is of type Unsigned16; higher values represent higher priority. It encodes the defending-priority value from the RSVP signaled preemption priority policy element (RFC 3181).
The Preemption-Priority AVP (AVP Code 609) is of type Unsigned16; higher values represent higher priority. The value encodes the same preemption-priority as used in the signaled preemption priority policy element of RFC 3181.
The SIP-Resource-Priority-Namespace AVP (AVP Code 613) is of type UTF8String and contains a string identifying a unique ordered set of priority values as described in RFC 4412. The SIP-Resource-Priority-Value AVP (AVP Code 614) is of type UTF8String and contains a namespace entry identifying a member of the priority value set.