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rfc:rfc5866

Internet Engineering Task Force (IETF) D. Sun, Ed. Request for Comments: 5866 Alcatel-Lucent Category: Standards Track P. McCann ISSN: 2070-1721 Motorola Labs

                                                         H. Tschofenig
                                                Nokia Siemens Networks
                                                               T. Tsou
                                                                Huawei
                                                              A. Doria
                                        Lulea University of Technology
                                                          G. Zorn, Ed.
                                                           Network Zen
                                                              May 2010
              Diameter Quality-of-Service Application

Abstract

 This document describes the framework, messages, and procedures for
 the Diameter Quality-of-Service (QoS) application.  The Diameter QoS
 application allows network elements to interact with Diameter servers
 when allocating QoS resources in the network.  In particular, two
 modes of operation, namely "Pull" and "Push", are defined.

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/rfc5866.

Copyright Notice

 Copyright (c) 2010 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

Sun, et al. Standards Track [Page 1] RFC 5866 Diameter QoS Application May 2010

 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.

Table of Contents

 1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
 2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  3
 3.  Framework  . . . . . . . . . . . . . . . . . . . . . . . . . .  5
   3.1.  Network Element Functional Model . . . . . . . . . . . . .  7
   3.2.  Implications of Endpoint QoS Capabilities  . . . . . . . .  8
     3.2.1.  Endpoint Categories  . . . . . . . . . . . . . . . . .  8
     3.2.2.  Interaction Modes between the Authorizing Entity
             and Network Element  . . . . . . . . . . . . . . . . .  9
   3.3.  Authorization Schemes  . . . . . . . . . . . . . . . . . . 10
     3.3.1.  Pull Mode Schemes  . . . . . . . . . . . . . . . . . . 10
     3.3.2.  Push Mode Schemes  . . . . . . . . . . . . . . . . . . 13
   3.4.  QoS Application Requirements . . . . . . . . . . . . . . . 14
 4.  QoS Application Session Establishment and Management . . . . . 17
   4.1.  Parties Involved . . . . . . . . . . . . . . . . . . . . . 17
   4.2.  Session Establishment  . . . . . . . . . . . . . . . . . . 18
     4.2.1.  Session Establishment for Pull Mode  . . . . . . . . . 18
     4.2.2.  Session Establishment for Push Mode  . . . . . . . . . 21
     4.2.3.  Discovery and Selection of Peer Diameter QoS
             Application Node . . . . . . . . . . . . . . . . . . . 24
   4.3.  Session Re-Authorization . . . . . . . . . . . . . . . . . 24
     4.3.1.  Client-Side Initiated Re-Authorization . . . . . . . . 25
     4.3.2.  Server-Side Initiated Re-Authorization . . . . . . . . 26
   4.4.  Session Termination  . . . . . . . . . . . . . . . . . . . 28
     4.4.1.  Client-Side Initiated Session Termination  . . . . . . 28
     4.4.2.  Server-Side Initiated Session Termination  . . . . . . 28
 5.  QoS Application Messages . . . . . . . . . . . . . . . . . . . 29
   5.1.  QoS-Authorization Request (QAR)  . . . . . . . . . . . . . 30
   5.2.  QoS-Authorization-Answer (QAA) . . . . . . . . . . . . . . 31
   5.3.  QoS-Install Request (QIR)  . . . . . . . . . . . . . . . . 32
   5.4.  QoS-Install Answer (QIA) . . . . . . . . . . . . . . . . . 32
   5.5.  Re-Auth-Request (RAR)  . . . . . . . . . . . . . . . . . . 33
   5.6.  Re-Auth-Answer (RAA) . . . . . . . . . . . . . . . . . . . 34
 6.  QoS Application State Machine  . . . . . . . . . . . . . . . . 34
   6.1.  Supplemented States for Push Mode  . . . . . . . . . . . . 34
 7.  QoS Application AVPs . . . . . . . . . . . . . . . . . . . . . 35
   7.1.  Reused Base Protocol AVPs  . . . . . . . . . . . . . . . . 36
   7.2.  QoS Application-Defined AVPs . . . . . . . . . . . . . . . 36
 8.  Accounting . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Sun, et al. Standards Track [Page 2] RFC 5866 Diameter QoS Application May 2010

 9.  Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
   9.1.  Example Call Flow for Pull Mode (Success Case) . . . . . . 38
   9.2.  Example Call Flow for Pull Mode (Failure Case) . . . . . . 40
   9.3.  Example Call Flow for Push Mode  . . . . . . . . . . . . . 43
 10. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 45
   10.1. AVP Codes  . . . . . . . . . . . . . . . . . . . . . . . . 45
   10.2. Application IDs  . . . . . . . . . . . . . . . . . . . . . 45
   10.3. Command Codes  . . . . . . . . . . . . . . . . . . . . . . 46
 11. Security Considerations  . . . . . . . . . . . . . . . . . . . 46
 12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 47
 13. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 47
 14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 48
   14.1. Normative References . . . . . . . . . . . . . . . . . . . 48
   14.2. Informative References . . . . . . . . . . . . . . . . . . 48

1. Introduction

 This document describes the framework, messages, and procedures for
 the Diameter [RFC3588] Quality-of-Service (QoS) application.  The
 Diameter QoS application allows Network Elements (NEs) to interact
 with Diameter servers when allocating QoS resources in the network.
 Two modes of operation are defined.  In the first, called "Pull"
 mode, the network element requests QoS authorization from the
 Diameter server based on some trigger (such as a QoS signaling
 protocol) that arrives along the data path.  In the second, called
 "Push" mode, the Diameter server proactively sends a command to the
 network element(s) to install QoS authorization state.  This could be
 triggered, for instance, by off-path signaling, such as Session
 Initiation Protocol (SIP) [RFC3261] call control.
 A set of command codes is specified that allows a single Diameter QoS
 application server to support both Pull and Push modes based on the
 requirements of network technologies, deployment scenarios, and end-
 host capabilities.  In conjunction with Diameter Attribute Value
 Pairs (AVPs) defined in [RFC5777] and in [RFC5624], this document
 depicts basic call-flow procedures used to establish, modify, and
 terminate a Diameter QoS application session.
 This document defines a number of Diameter-encoded AVPs, which are
 described using a modified version of the Augmented Backus-Naur Form
 (ABNF), see [RFC3588].

2. Terminology

 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].

Sun, et al. Standards Track [Page 3] RFC 5866 Diameter QoS Application May 2010

 The following terms are used in this document:
 AAA Cloud
    An infrastructure of Authentication, Authorization, and Accounting
    (AAA) entities (clients, agents, servers) communicating via a AAA
    protocol over trusted, secure connections.  It offers
    authentication, authorization, and accounting services to
    applications in local and roaming scenarios.  Diameter and RADIUS
    [RFC2865] are both widely deployed AAA protocols.
 Application Endpoint (AppE)
    An Application Endpoint is an entity in an end-user device that
    exchanges signaling messages with Application Servers or directly
    with other Application Endpoints.  Based on the result of this
    signaling, the endpoint may make a request for QoS from the
    network.  For example, a SIP User Agent is one kind of Application
    Endpoint.
 Application Server (AppS)
    An Application Server is an entity that exchanges signaling
    messages with an Application Endpoint (see above).  It may be a
    source of authorization for QoS-enhanced application flows.  For
    example, a SIP server is one kind of Application Server.
 Authorizing Entity (AE)
    The Authorizing Entity is a Diameter server that supports the QoS
    application.  It is responsible for authorizing QoS requests for a
    particular application flow or aggregate.  The Authorizing Entity
    may be a standalone entity or may be integrated with an
    Application Server and may be co-located with a subscriber
    database.  This entity corresponds to the Policy Decision Point
    (PDP) [RFC2753].
 Network Element (NE)
    A QoS-aware router that acts as a Diameter client for the QoS
    application.  This entity triggers the protocol interaction for
    Pull mode, and it is the recipient of QoS information in Push
    mode.  The Diameter client at a Network Element corresponds to the
    Policy Enforcement Point (PEP) [RFC2753].
 Pull Mode
    In this mode, the QoS authorization process is invoked by the QoS
    reservation request received from the Application Endpoint.  The
    Network Element then requests the QoS authorization decision from
    the Authorizing Entity.

Sun, et al. Standards Track [Page 4] RFC 5866 Diameter QoS Application May 2010

 Push Mode
    In this mode, the QoS authorization process is invoked by the
    request from the Application Server or local policies in the
    Authorizing Entity.  The Authorizing Entity then installs the QoS
    authorization decision to the Network Element directly.
 Resource Requesting Entity (RRE)
    A Resource Requesting Entity is a logical entity that supports the
    protocol interaction for QoS resources.  The RRE resides in the
    end-host and is able to communicate with peer logical entities in
    an Authorizing Entity or a Network Element to trigger the QoS
    authorization process.

3. Framework

 The Diameter QoS application runs between an NE (acting as a Diameter
 client) and the resource AE (acting as a Diameter server).  A high-
 level picture of the resulting architecture is shown in Figure 1.
             +-------+---------+
             |   Authorizing   |
             |     Entity      |
             |(Diameter Server)|
             +-------+---------+
                     |
                     |
              /\-----+-----/\
          ////               \\\\
        ||       AAA Cloud       ||
       |   (Diameter application)  |
        ||                       ||
          \\\\               ////
              \-------+-----/
                      |
     +---+--+   +-----+----+   +---+--+
     |      |   |    NE    |   |      |    Media
     +  NE  +===+(Diameter +===+  NE  +=============>>
     |      |   |  Client) |   |      |    Flow
     +------+   +----------+   +------+
             Figure 1: An Architecture Supporting QoS-AAA
 Figure 1 depicts NEs through which media flows need to pass, a cloud
 of AAA servers, and an AE.  Note that there may be more than one
 router that needs to interact with the AAA cloud along the path of a
 given application flow, although the figure only depicts one for
 clarity.

Sun, et al. Standards Track [Page 5] RFC 5866 Diameter QoS Application May 2010

 In some deployment scenarios, NEs may request authorization through
 the AAA cloud based on an incoming QoS reservation request.  The NE
 will route the request to a designated AE.  The AE will return the
 result of the authorization decision.  In other deployment scenarios,
 the authorization will be initiated upon dynamic application state,
 so that the request must be authenticated and authorized based on
 information from one or more AppSs.  After receiving the
 authorization request from the AppS or the NE, the AE decides the
 appropriate mode (i.e., Push or Pull).  The usage of Push or Pull
 mode can be determined by the Authorizing Entity either statically or
 dynamically.  Static determination might be based on a configurable
 defined policy in the Authorizing Entity, while dynamic determination
 might be based on information received from an application server.
 For Push mode, the Authorizing Entity needs to identify the
 appropriate NE(s) to which QoS authorization information needs to be
 pushed.  It might determine this based on information received from
 the AppS, such as the IP addresses of media flows.
 In some deployment scenarios, there is a mapping between access
 network type and the service logic (e.g., selection of Push or Pull
 mode and other differentiated handling of the resource admission and
 control).  The access network type might be derived from the
 authorization request from the AppS or the NE, and in this case, the
 Authorizing Entity can identify the corresponding service logic based
 on the mapping.
 If the interface between the NEs and the AAA cloud is identical
 regardless of whether or not the AE communicates with an AppS,
 routers are insulated from the details of particular applications and
 need not know that Application Servers are involved.  Also, the AAA
 cloud may also encompass business relationships such as those between
 network operators and third-party application providers.  This
 enables flexible intra- or inter-domain authorization, accounting,
 and settlement.

Sun, et al. Standards Track [Page 6] RFC 5866 Diameter QoS Application May 2010

3.1. Network Element Functional Model

 Figure 2 depicts a logical operational model of resource management
 in a router.
             +-------------------------------------------------------+
             | DIAMETER Client                                       |
             | Functionality                                         |
             | +---------------++-----------------++---------------+ |
             | | User          || QoS Application || Accounting    | |
             | | Authentication|| Client          || Client (e.g., | |
             | | Client        || (Authorization  ||for QoS Traffic| |
             | +---------------+| of QoS Requests)|+---------------+ |
             |                  +-----------------+                  |
             +-------------------------------------------------------+
                                            ^
                                            v
          +--------------+            +----------+
          |QoS Signaling |            | Resource |
          |Msg Processing|<<<<<>>>>>>>|Management|
          +--------------+            +----------+
               .  ^   |              *      ^
               |  v   .            *        ^
          +-------------+        *          ^
          |Signaling msg|       *           ^
          | Processing  |       *           V
          +-------------+       *           V
               |      |         *           V
   ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
               .      .         *           V
               |      |         *     .............................
               .      .         *     .   Traffic Control         .
               |      |         *     .                +---------+.
               .      .         *     .                |Admission|.
               |      |         *     .                | Control |.
     +----------+    +------------+   .                +---------+.
 <.->|  Input   |    | Outgoing   |<.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.->
     |  Packet  |    | Interface  |   .+----------+    +---------+.
 ===>|Processing|====| Selection  |===.|  Packet  |====| Packet  |.=>
     |          |    |(Forwarding)|   .|Classifier|     Scheduler|.
     +----------+    +------------+   .+----------+    +---------+.
                                      .............................
         <.-.-> = signaling flow
         =====> = data flow (sender --> receiver)
         <<<>>> = control and configuration operations
         ****** = routing table manipulation
              Figure 2: Network Element Functional Model

Sun, et al. Standards Track [Page 7] RFC 5866 Diameter QoS Application May 2010

 The processing of incoming QoS reservation requests includes three
 actions: admission control, authorization, and resource reservation.
 The admission control function provides information about available
 resources and determines whether there are enough resources to
 fulfill the request.  Authorization is performed by the Diameter
 client, which involves contacting an authorization entity through the
 AAA cloud shown in Section 3.  If both checks are successful, the
 authorized QoS parameters are set in the packet classifier and the
 packet scheduler.  Note that the parameters passed to the Traffic
 Control function may be different from the ones that requested QoS
 (depending on the authorization decision).  Once the requested
 resource is granted, the Resource Management function provides
 accounting information to the AE via the Diameter client.

3.2. Implications of Endpoint QoS Capabilities

3.2.1. Endpoint Categories

 The QoS capabilities of Application Endpoints are varied, and can be
 categorized as follows:
 Category 1
    A Category 1 Application Endpoint has no QoS capability at either
    the application or the network level.  This type of AppE may set
    up a connection through application signaling, but it is incapable
    of specifying resource/QoS requirements through either
    application- or network-level signaling.
 Category 2
    A Category 2 Application Endpoint only has QoS capability at the
    application level.  This type of AppE is able to set up a
    connection through application signaling with certain resource/QoS
    requirements (e.g., application attributes), but it is unable to
    signal any resource/QoS requirements at the network level.
 Category 3
    A Category 3 Application Endpoint has QoS capability at the
    network level.  This type of AppE may set up a connection through
    application signaling, translate service characteristics into
    network resource/QoS requirements (e.g., network QoS class)
    locally, and request the resources through network signaling,
    e.g., Resource ReSerVation Protocol (RSVP) [RFC2205] or Next Steps
    in Signaling (NSIS) [NSIS-QOS].

Sun, et al. Standards Track [Page 8] RFC 5866 Diameter QoS Application May 2010

3.2.2. Interaction Modes between the Authorizing Entity and Network

      Element
 Different QoS mechanisms are employed in packet networks.  Those QoS
 mechanisms can be categorized into two schemes: IntServ [RFC2211]
 [RFC2212] and Diffserv [RFC2474].  In the IntServ scheme, network
 signaling (e.g., RSVP, NSIS, or link-specific signaling) is commonly
 used to initiate a request from an AppE for the desired QoS resource.
 In the Diffserv scheme, QoS resources are provisioned based upon some
 predefined QoS service classes rather than AppE-initiated, flow-based
 QoS requests.
 It is obvious that the eligible QoS scheme is correlated to the
 AppE's capability in the context of QoS authorization.  Since
 Category 1 and 2 AppEs cannot initiate the QoS resource requests by
 means of network signaling, using the current mechanism of the
 IntServ model to signal QoS information across the network is not
 applicable to them in general.  Depending on network technology and
 operator requirements, a Category 3 AppE may either make use of
 network signaling for resource requests or not.
 The diversity of QoS capabilities of endpoints and QoS schemes of
 network technology leads to the distinction on the interaction mode
 between the QoS authorization system and underlying NEs.  When the
 IntServ scheme is employed by a Category 3 endpoint, the
 authorization process is typically initiated by an NE when a trigger
 is received from the endpoint such as network QoS signaling.  In the
 Diffserv scheme, since the NE is unable to request the resource
 authorization on its own initiative, the authorization process is
 typically triggered by either the request of AppSs or policies
 defined by the operator.
 As a consequence, two interaction modes are needed in support of
 different combinations of QoS schemes and endpoint's QoS
 capabilities: Push mode and Pull mode.
 Push mode
    The QoS authorization process is triggered by AppSs or local
    network conditions (e.g., time of day on resource usage and QoS
    classes), and the authorization decisions are installed by the AE
    to the network element on its own initiative without explicit
    request.  In order to support Push mode, the AE (i.e., Diameter
    server) should be able to initiate a Diameter authorization
    session to communicate with the NE (i.e., Diameter client) without
    any preestablished connection from the network element.

Sun, et al. Standards Track [Page 9] RFC 5866 Diameter QoS Application May 2010

 Pull mode
    The QoS authorization process is triggered by the network
    signaling received from end-user equipment or by a local event in
    the NE according to pre-configured policies, and authorization
    decisions are produced upon the request of the NE.  In order to
    support Pull mode, the NE (i.e., Diameter client) will initiate a
    Diameter authorization session to communicate with the Authorizing
    Entity (i.e., Diameter server).
 For Category 1 and 2 Application Endpoints, Push mode is REQUIRED.
 For a Category 3 AppE, either Push mode or Pull mode MAY be used.
 Push mode is applicable to certain networks, for example, Cable
 network, DSL, Ethernet, and Diffserv-enabled IP/MPLS.  Pull mode is
 more appropriate to IntServ-enabled IP networks or certain wireless
 networks such as the General Packet Radio Service (GPRS) networks
 defined by the Third Generation Partnership Project (3GPP).  Some
 networks (for example, Worldwide Interoperability for Microwave
 Access (WiMAX)) may require both Push and Pull modes.

3.3. Authorization Schemes

3.3.1. Pull Mode Schemes

 Three types of basic authorization schemes for Pull mode exist: one
 type of two-party scheme and two types of three-party schemes.  The
 notation adopted here is in respect to the entity that performs the
 QoS authorization (QoS Authz).  The authentication of the QoS
 requesting entity might be done at the NE as part of the QoS
 signaling protocol, or by an off-path protocol (on the application
 layer or for network access authentication) or the AE might be
 contacted with a request for authentication and authorization of the
 QoS requesting entity.  From the Diameter QoS application's point of
 view, these schemes differ in type of information that need to be
 carried.  Here we focus on the "Basic Three-Party Scheme" (see
 Figure 3) and the "Token-Based Three-Party Scheme" (see Figure 4).
 In the "Two-Party Scheme", the QoS RRE is authenticated by the NE and
 the authorization decision is made either locally at the NE itself or
 offloaded to a trusted entity (most likely within the same
 administrative domain).  In the two-party case, no Diameter QoS
 protocol interaction is required.

Sun, et al. Standards Track [Page 10] RFC 5866 Diameter QoS Application May 2010

                                      +--------------+
                                      | Authorizing  |
                                      | Entity       |
                                      | authorizing  | <......+
                                      | resource     |        .
                                      | request      |        .
                                      +------------+-+        .
                                      --^----------|--   .    .
                                 /////  |          |  \\\\\   .
                               //       |          |       \\ .
                              |     QoS | QoS AAA  | QoS     |.
                              |    authz| protocol |authz    |.
                              |     req.|          | res.    |.
                               \\       |          |       // .
                                 \\\\\  |          |  /////   .
                        QoS           --|----------v--   .    .
     +-------------+    request       +-+------------+        .
     |  Entity     |----------------->| NE           |        .
     |  requesting |                  | performing   |        .
     |  resource   |granted / rejected| QoS          |  <.....+
     |             |<-----------------| reservation  | financial
     +-------------+                  +--------------+ settlement
                     Figure 3: Three-Party Scheme
 In the "Basic Three-Party Scheme", a QoS reservation request that
 arrives at the NE is forwarded to the Authorizing Entity (e.g., in
 the user's home network), where the authorization decision is made.
 As shown, financial settlement -- a business relationship, such as a
 roaming agreement -- between the visited network and the home network
 ensures that the visited network is compensated for the resources
 consumed by the user via the home network.

Sun, et al. Standards Track [Page 11] RFC 5866 Diameter QoS Application May 2010

                             financial settlement
                              ...........................+
    Authorization             V             -------      .
    Token Request   +--------------+      / QoS AAA \    .
    +-------------->|              |     /  protocol \   .
    |               | Authorizing  +--------------+   \  .
    |               | Entity       |   |          |    | .
    |        +------+              |<--+----+     |    | .
    |        |      +--------------+  |QoS  |     |QoS  |.
    |        |                        |authz|     |authz|.
    |        |Authorization           |req.+|     |res. |.
    |        |Token                   |Token|     |     |.
    |        |                         |    |     | .  | .
    |        |                          \   |     | . /  .
    |        |                            \ |     | /    .
    |        |      QoS request             |-----V .    .
  +-------------+ + Authz  Token   +--------+-----+      .
  |  Entity     |----------------->| NE           |      .
  |  requesting |                  | performing   |      .
  |  resource   |granted / rejected| QoS          | <....+
  |             |<-----------------| reservation  |
  +-------------+                  +--------------+
               Figure 4: Token-Based Three-Party Scheme
 The "Token-Based Three-Party Scheme" is applicable to environments
 where a previous protocol interaction is used to request
 authorization tokens to assist the authorization process at the NE or
 the AE [RFC3521].
 The QoS RRE may be involved in an application-layer protocol
 interaction, for example, using SIP [RFC3313], with the AE.  As part
 of this interaction, authentication and authorization at the
 application layer might take place.  As a result of a successful
 authorization decision, which might involve the user's home AAA
 server, an authorization token is generated by the AE (e.g., the SIP
 proxy and an entity trusted by the SIP proxy) and returned to the
 end-host for inclusion into the QoS signaling protocol.  The
 authorization token will be used by an NE that receives the QoS
 signaling message to authorize the QoS request.  Alternatively, the
 Diameter QoS application will be used to forward the authorization
 token to the user's home network.  The authorization token allows for
 the authorization decision performed at the application layer to be
 associated with a corresponding QoS signaling session.  Note that the
 authorization token might either refer to established state
 concerning the authorization decision or the token might itself carry
 the authorized parameters (protected by a digital signature or a
 keyed message digest to prevent tampering).  In the latter case, the

Sun, et al. Standards Track [Page 12] RFC 5866 Diameter QoS Application May 2010

 authorization token may contain several pieces of information
 pertaining to the authorized application session, but at minimum it
 should contain:
 o  An identifier for the AE (for example, an AppS) that issued the
    authorization token;
 o  An identifier referring to a specific application protocol session
    for which the token was issued; and
 o  A keyed message digest or digital signature protecting the content
    of the authorization token.
 A possible structure for the authorization token and the policy
 element carrying it are proposed in the context of RSVP [RFC3520].
 In the scenario mentioned above, where the QoS resource requesting
 entity is involved in an application-layer protocol interaction with
 the AE, it may be worthwhile to consider a token-less binding
 mechanism also.  The application-layer protocol interaction may have
 indicated the transport port numbers at the QoS RRE where it might
 receive media streams (for example, in SIP/SDP [RFC4566] signaling,
 these port numbers are advertised).  The QoS RRE may also use these
 port numbers in some IP filter indications to the NE performing QoS
 reservation so that it may properly tunnel the inbound packets.  The
 NE performing QoS reservation will forward the QoS resource
 requesting entity's IP address and the IP filter indications to the
 AE in the QoS authorization request.  The AE will use the QoS RRE's
 IP address and the port numbers in the IP filter indication, which
 will match the port numbers advertised in the earlier application-
 layer protocol interaction, to identify the right piece of policy
 information to be sent to the NE performing the QoS reservation in
 the QoS Authorization response.

3.3.2. Push Mode Schemes

 Push mode can be further divided into two types: endpoint-initiated
 and network-initiated.  In the former case, the authorization process
 is triggered by AppS in response to an explicit QoS request from an
 endpoint through application signaling, e.g., SIP; in the latter
 case, the authorization process is triggered by the AppS without an
 explicit QoS request from an endpoint.
 In the endpoint-initiated scheme, the QoS RRE (i.e., the AppE)
 determines the required application-level QoS and sends a QoS request
 through an application signaling message.  The AppS will extract
 application-level QoS information and trigger the authorization
 process to the AE.  In the network-initiated scheme, the AE and/or

Sun, et al. Standards Track [Page 13] RFC 5866 Diameter QoS Application May 2010

 AppS should derive and determine the QoS requirements according to
 application attribute, subscription, and endpoint capability when the
 endpoint does not explicitly indicate the QoS attributes.  The AE
 makes an authorization decision based on application-level QoS
 information, network policies, end-user subscription, network
 resource availability, etc., and installs the decision to the NE
 directly.
 A Category 1 AppE requires network-initiated Push mode and a Category
 2 AppE may use either type of Push Mode.
                             financial settlement
                              ...........................+
    Application               V             -------      .
    signaling msg   +--------------+      / QoS AAA \    .
    +-------------->|              |     /  protocol \   .
    |               | Authorizing  +--------------+   \  .
    |               | Entity       |   |          |    | .
    |               +              |<--+----+     |    | .
    |               +--------------+  |QoS  |     |QoS  |.
    |                                install|     |install
    |                                 |rsp. |     |req. |.
    |                                 |     |     |     |.
    |                                  |    |     | .  | .
    |                                   \   |     | . /  .
    |                                     \ |     | /    .
    V                                       |-----V .    .
  +-------------+                  +--------+-----+      .
  |  Entity     |                  | NE           |      .
  |  requesting |                  | performing   |      .
  |  resource   |QoS rsrc granted  | QoS          | <....+
  |             |<-----------------| reservation  |
  +-------------+                  +--------------+
                    Figure 5: Scheme for Push Mode

3.4. QoS Application Requirements

 A QoS application must meet a number of requirements applicable to a
 diverse set of networking environments and services.  It should be
 compatible with different deployment scenarios having specific QoS
 signaling models and security issues.  Satisfying the requirements
 listed below while interworking with QoS signaling protocols, a
 Diameter QoS application should accommodate the capabilities of the
 QoS signaling protocols rather than introduce functional requirements
 on them.  A list of requirements for a QoS authorization application
 is provided here:

Sun, et al. Standards Track [Page 14] RFC 5866 Diameter QoS Application May 2010

 Identity-based Routing
    The Diameter QoS application MUST route AAA requests to the
    Authorizing Entity, based on the provided identity of the QoS
    requesting entity or the identity of the AE encoded in the
    provided authorization token.
 Flexible Authentication Support
    The Diameter QoS application MUST support a variety of different
    authentication protocols for verification of authentication
    information present in QoS signaling messages.  The support for
    these protocols MAY be provided indirectly by tying the signaling
    communication for QoS to a previous authentication protocol
    exchange (e.g., using network access authentication).
 Making an Authorization Decision
    The Diameter QoS application MUST exchange sufficient information
    between the AE and the enforcing entity (and vice versa) to
    compute an authorization decision and to execute this decision.
 Triggering an Authorization Process
    The Diameter QoS application MUST allow periodic and event-
    triggered execution of the authorization process, originated at
    the enforcing entity or even at the AE.
 Associating QoS Reservations and Application State
    The Diameter QoS application MUST carry information sufficient for
    an AppS to identify the appropriate application session and
    associate it with a particular QoS reservation.
 Dynamic Authorization
    It MUST be possible for the Diameter QoS application to push
    updates towards the NE(s) from Authorizing Entities.
 Bearer Gating
    The Diameter QoS application MUST allow the AE to gate (i.e.,
    enable/disable) authorized application flows based on, e.g.,
    application state transitions.
 Accounting Records
    The Diameter QoS application MAY define QoS accounting records
    containing duration, volume (byte count) usage information, and a
    description of the QoS attributes (e.g., bandwidth, delay, loss
    rate) that were supported for the flow.
 Sending Accounting Records
    The NE SHOULD be able to send accounting records for a particular
    QoS reservation state to an accounting entity.

Sun, et al. Standards Track [Page 15] RFC 5866 Diameter QoS Application May 2010

 Failure Notification
    The Diameter QoS application MUST allow the NE to report failures,
    such as loss of connectivity due to movement of a mobile node or
    other reasons for packet loss, to the Authorizing Entity.
 Accounting Correlation
    The Diameter QoS application MAY support the exchange of
    sufficient information to allow for correlation between accounting
    records generated by the NEs and accounting records generated by
    an AppS.
 Interaction with Other AAA Applications
    Interaction with other AAA applications, such as the Diameter
    Network Access Server Application [RFC4005], may be required for
    exchange of authorization, authentication, and accounting
    information.
 In deployment scenarios where authentication of the QoS reservation
 requesting entity (e.g., the user) is done by means outside the
 Diameter QoS application protocol interaction, the AE is contacted
 only with a request for QoS authorization.  Authentication might have
 taken place already via the interaction with the Diameter application
 [RFC4005] or as part of the QoS signaling protocol (e.g., Transport
 Layer Security (TLS) [RFC5246] in the General Internet Signaling
 Transport (GIST) protocol [NSIS-NTLP]).
 Authentication of the QoS reservation requesting entity to the AE is
 necessary if a particular Diameter QoS application protocol cannot be
 related (or if there is no intention to relate it) to a prior
 authentication.  In this case, the AE MUST authenticate the QoS
 reservation requesting entity in order to authorize the QoS request
 as part of the Diameter QoS protocol interaction.
 This document refers to three types of sessions that need to be
 properly correlated.
 QoS Signaling Session
    The time period during which a QoS signaling protocol establishes,
    maintains, and deletes a QoS reservation state at the QoS network
    element is referred to as a QoS signaling session.  Different QoS
    signaling protocols use different ways to identify QoS signaling
    sessions.  The same applies to different usage environments.
    Currently, this document supports three types of QoS session
    identifiers, namely a signaling session id (e.g., the Session
    Identifier used by the NSIS protocol suite), a flow id (e.g.,
    identifier assigned by an application to a certain flow as used in
    the 3GPP), and a flow description based on the IP parameters of
    the flow's endpoints.

Sun, et al. Standards Track [Page 16] RFC 5866 Diameter QoS Application May 2010

 Diameter Authorization Session
    The time period for which a Diameter server authorizes a requested
    service (i.e., QoS resource reservation) is referred to as a
    Diameter authorization session.  It is identified by a Session-Id
    included in all Diameter messages used for management of the
    authorized service (initial authorization, re-authorization,
    termination), see [RFC3588].
 Application-Layer Session
    The application-layer session identifies the duration of an
    application-layer service that requires provision of a certain
    QoS.  An application-layer session identifier is provided by the
    QoS requesting entity in the QoS signaling messages, for example
    as part of the authorization token.  In general, the application
    session identifier is opaque to the QoS-aware NEs.  It is included
    in the authorization request message sent to the AE and helps it
    to correlate the QoS authorization request to the application
    session state information.
 Correlating these sessions is done at each of the three involved
 entities: The QoS requesting entity correlates the application with
 the QoS signaling sessions.  The QoS NE correlates the QoS signaling
 session with the Diameter authorization sessions.  The AE SHOULD bind
 the information about the three sessions together.  Note that in
 certain scenarios, not all of the sessions are present.  For example,
 the application session might not be visible to the QoS signaling
 protocol directly if there is no binding between the application
 session and the QoS requesting entity using the QoS signaling
 protocol.

4. QoS Application Session Establishment and Management

4.1. Parties Involved

 Authorization models supported by this application include three
 parties:
 o  Resource Requesting Entity
 o  Network Elements (Diameter QoS application (DQA) client)
 o  Authorizing Entity (Diameter QoS application (DQA) server)
 Note that the QoS RRE is only indirectly involved in the message
 exchange.  This entity provides the trigger to initiate the Diameter
 QoS protocol interaction by transmitting QoS signaling messages.  The
 Diameter QoS application is only executed between the Network Element
 (i.e., DQA client) and the Authorizing Entity (i.e., DQA server).

Sun, et al. Standards Track [Page 17] RFC 5866 Diameter QoS Application May 2010

 The QoS RRE may communicate with the AE using application-layer
 signaling for the negotiation of service parameters.  As part of this
 application-layer protocol interaction, for example using SIP,
 authentication and authorization might take place.  This message
 exchange is, however, outside the scope of this document.  The
 protocol communication between the QoS resource requesting entity and
 the QoS NE might be accomplished using the NSIS protocol suite, RSVP,
 or a link-layer signaling protocol.  A description of these protocols
 is also outside the scope of this document.

4.2. Session Establishment

 Pull and Push modes use a different set of command codes for session
 establishment.  For other operations, such as session modification
 and termination, they use the same set of command codes.
 The selection of Pull mode or Push mode operation is based on the
 trigger of the QoS authorization session.  When a QoS-Authorization-
 Request (QAR, see Section 5.1) message with a new Session-Id is
 received, the AE operates in Pull mode; when other triggers are
 received, the AE operates in Push mode.  Similarly, when a QoS-
 Install-Request (QIR, see Section 5.3} with a new Session-Id is
 received, the NE operates in Push mode; when other triggers are
 received, the NE operates in Pull mode.
 The QoS authorization session is typically established per subscriber
 base (i.e., all requests with the same User-ID), but it is also
 possible to be established on a per node or per request base.  The
 concurrent sessions between an NE and an AE are identified by
 different Session-Ids.

4.2.1. Session Establishment for Pull Mode

 A request for a QoS reservation or local events received by an NE can
 trigger the initiation of a Diameter QoS authorization session.  The
 NE converts the required objects from the QoS signaling message to
 Diameter AVPs and generates a QAR message.
 Figure 6 shows the protocol interaction between a Resource Requesting
 Entity, a Network Element, and the Authorizing Entity.
 The AE's identity, information about the application session and/or
 identity and credentials of the QoS RRE, requested QoS parameters,
 and the signaling session identifier and/or QoS-enabled data flows
 identifiers MAY be encapsulated into respective Diameter AVPs and
 included in the Diameter message sent to the AE.  The QAR is sent to
 a Diameter server that can be either the home server of the QoS
 requesting entity or an AppS.

Sun, et al. Standards Track [Page 18] RFC 5866 Diameter QoS Application May 2010

 +------------------------------------------+------------------------+
 | QoS-Specific Input Data                  | Diameter AVPs          |
 +------------------------------------------+------------------------+
 | Authorizing Entity ID (e.g.,             | Destination-Host       |
 | Destination-Host taken from              | Destination-Realm      |
 | authorization token, Destination-Realm,  |                        |
 | or derived from the Network Access       |                        |
 | Identifier (NAI) of the QoS requesting   |                        |
 | entity)                                  |                        |
 | Authorization Token Credentials of the   | QoS-Authorization-Data |
 | QoS requesting entity                    | User-Name              |
 | QoS-Resources (including QoS parameters) |                        |
 +------------------------------------------+------------------------+
         Table 1: Mapping Input Data to QoS AVPs -- Pull Mode
 Authorization processing starts at the Diameter QoS server when it
 receives the QAR.  Based on the information in the QoS-
 Authentication-Data, User-Name, and QoS-Resources AVPs, the server
 determines the authorized QoS resources and flow state (enabled/
 disabled) from locally available information (e.g., policy
 information that may be previously established as part of an
 application-layer signaling exchange or the user's subscription
 profile).  The QoS-Resources AVP is defined in [RFC5777].  The
 authorization decision is then reflected in the response returned to
 the Diameter client with the QoS-Authorization-Answer (QAA) message.

Sun, et al. Standards Track [Page 19] RFC 5866 Diameter QoS Application May 2010

                                             Authorizing
   End-Host         Network Element             Entity
 requesting QoS       (Diameter               (Diameter
                      QoS Client)             QoS Server)
     |                   |                         |
     +---QoS-Reserve---->|                         |
     |                   +- - - - - QAR - - - - - >|
     |                   |(QoS-Resources,          |
     |                   |   QoS-Auth-Data,User-ID)|
     |                   |                +--------+--------------+
     |                   |                |  Authorize request    |
     |                   |                |  Keep session data    |
     |                   |                |/Authz-time,Session-Id/|
     |                   |                +--------+--------------+
     |                   |< - - - - QAA - - - - - -+
     |                   |(Result-Code,            |
     |                   |QoS-Resources,Authz-time)|
     |           +-------+---------+
     |           |Install QoS state|
     |           |       +         |
     |           | Authz  session  |
     |           | /Authz-time/    |                QoS Responder
     |           |                 |                    Node
     |           +-------+---------+                      |
     |                   +----------QoS-Reserve---....--->|
     |                   |                                |
     |                   |<---------QoS-Response--....----|
     |<--QoS-Response----+                                |
     |                   |                                |
     |=====================Data Flow==============....===>|
       Figure 6: Initial QoS Request Authorization for Pull Mode
 The Authorizing Entity keeps authorization session state and SHOULD
 save additional information for management of the session (e.g.,
 Signaling-Session-Id, authentication data) as part of the session
 state information.
 The final result of the authorization request is provided in the
 Result-Code AVP of the QAA message sent by the Authorizing Entity.
 In the case of successful authorization (i.e., Result-Code =
 DIAMETER_LIMITED_SUCCESS (see Section 7.1)), information about the
 authorized QoS resources and the status of the authorized flow
 (enabled/disabled) is provided in the QoS-Resources AVP of the QAA
 message.  The QoS information provided via the QAA is installed by
 the QoS Traffic Control function of the NE.  The value

Sun, et al. Standards Track [Page 20] RFC 5866 Diameter QoS Application May 2010

 DIAMETER_LIMITED_SUCCESS indicates that the AE expects confirmation
 via another QAR message for successful QoS resource reservation and
 for final reserved QoS resources (see below).
 One important piece of information returned from the Authorizing
 Entity is the authorization lifetime (carried inside the QAA).  The
 authorization lifetime allows the NE to determine how long the
 authorization decision is valid for this particular QoS reservation.
 A number of factors may influence the authorized session duration,
 such as the user's subscription plan or the currently available
 credits at the user's account (see Section 8).  The authorization
 duration is time-based, as specified in [RFC3588].  For an extension
 of the authorization period, a new QoS-Authorization-Request/Answer
 message exchange SHOULD be initiated.  Further aspects of QoS
 authorization session maintenance are discussed in Sections 4.3, 4.4,
 and 8.
 The indication of a successful QoS reservation and activation of the
 data flow is provided by the transmission of a QAR message, which
 reports the parameters of the established QoS state: reserved
 resources, duration of the reservation, and identification of the QoS
 enabled flow/QoS signaling session.  The Diameter QoS server
 acknowledges the reserved QoS resources with the QA Answer (QAA)
 message where the Result-Code is set to 'DIAMETER_SUCCESS'.  Note
 that the reserved QoS resources reported in this QAR message MAY be
 different than those authorized with the initial QAA message, due to
 the QoS-signaling-specific behavior (e.g., receiver-initiated
 reservations with One-Path-With-Advertisements) or specific process
 of QoS negotiation along the data path.

4.2.2. Session Establishment for Push Mode

 The Diameter QoS server in the AE initiates a Diameter QoS
 authorization session upon the request for a QoS reservation
 triggered by application-layer signaling or by local events, and
 generates a QoS-Install-Request (QIR) message to the Diameter QoS
 client in the NE in which it maps required objects to Diameter
 payload objects.
 Figure 7 shows the protocol interaction between the AE, a Network
 Element, and an RRE.
 The NE's identity, information about the application session and/or
 identity and credentials of the QoS resource requesting entity,
 requested QoS parameters, and signaling session identifier and/or QoS
 enabled data flows identifiers MAY be encapsulated into respective
 Diameter AVPs and included in the Diameter message sent from a
 Diameter QoS server in the Authorizing Entity to a Diameter QoS

Sun, et al. Standards Track [Page 21] RFC 5866 Diameter QoS Application May 2010

 client in the NE.  This requires that the AE has knowledge of
 specific information for allocating and identifying the NE that
 should be contacted and the data flow for which the QoS reservation
 should be established.  This information can be statically configured
 or dynamically discovered, see Section 4.2.3 for details.
 +-----------------------------------------+-------------------------+
 | QoS-Specific Input Data                 | Diameter AVPs           |
 +-----------------------------------------+-------------------------+
 | Network Element ID                      | Destination-Host        |
 |                                         | Destination-Realm       |
 | Authorization Token Credentials of the  | QoS-Authorization-Data  |
 | QoS requesting entity                   | User-Name               |
 | QoS-Resources (including QoS            |                         |
 | parameters)                             |                         |
 +-----------------------------------------+-------------------------+
         Table 2: Mapping Input Data to QoS AVPs -- Push Mode
 Authorization processing starts at the Diameter QoS server when it
 receives a request from an RRE through an AppS (e.g., SIP Invite) or
 is triggered by a local event (e.g., a pre-configured timer).  Based
 on the received information, the server determines the authorized QoS
 resources and flow state (enabled/disabled) from locally available
 information (e.g., policy information that may be previously
 established as part of an application-layer signaling exchange, or
 the user's subscription profile).  The authorization decision is then
 reflected in the QoS-Install-Request (QIR) message to the Diameter
 QoS client.

Sun, et al. Standards Track [Page 22] RFC 5866 Diameter QoS Application May 2010

                                             Authorizing
   End-Host         Network Element             Entity
 requesting QoS       (Diameter               (Diameter
                      QoS Client)             QoS Server)
     |                   |                          |
     |                   |                          |<-- Trigger --
     |                   |                 +--------+--------------+
     |                   |                 |  Authorize request    |
     |                   |                 |  Keep session data    |
     |                   |                 |/Authz-time,Session-Id/|
     |                   |                 +--------+--------------+
     |                   |                          |
     |                   |<-- - -- - QIR - - - - - -+
     |                   |(Initial Request,Decision |
     |                   |(QoS-Resources,Authz-time)|
     |           +-------+---------+
     |           |Install QoS state|
     |           |       +         |
     |           | Authz  session  |
     |           | /Authz-time/    |
     |           |                 |
     |           +-------+---------+
     |                   + - - - - QIA - - - - - ->|
     |                   |    (Result-Code,        |
     |                   |     QoS-Resources)      |
     |                   |                +--------+--------------+
     |                   |                | Report for successful |
     |                   |                |   QoS reservation     |
     |                   |                |Update of reserved QoS |
     |                   |                |      resources        |
     |                   |                +--------+--------------+
     |                   |                         QoS Responder
     |                   |                               Node
     |                   |                                |
     |=====================Data Flow==============....===>|
       Figure 7: Initial QoS Request Authorization for Push Mode
 The AE keeps authorization session state and SHOULD save additional
 information for management of the session (e.g.,
 Signaling-Session-Id, authentication data) as part of the session
 state information.
 The final result of the authorization decision is provided in the
 QoS-Resources AVP of the QIR message sent by the AE.  The QoS
 information provided via the QIR is installed by the QoS Traffic
 Control function of the NE.

Sun, et al. Standards Track [Page 23] RFC 5866 Diameter QoS Application May 2010

 One important piece of information from the AE is the authorization
 lifetime (carried inside the QIR).  The authorization lifetime allows
 the NE to determine how long the authorization decision is valid for
 this particular QoS reservation.  A number of factors may influence
 the authorized session duration, such as the user's subscription plan
 or the currently available credits at the user's account (see
 Section 8).  The authorization duration is time-based as specified in
 [RFC3588].  For an extension of the authorization period, a new QoS-
 Install-Request/Answer message or QoS-Authorization-Request/Answer
 message exchange SHOULD be initiated.  Further aspects of QoS
 authorization session maintenance are discussed in Sections 4.3, 4.4,
 and 8.
 The indication of QoS reservation and activation of the data flow can
 be provided by the QoS-Install-Answer message immediately.  In the
 case of successful enforcement, the Result-Code (= DIAMETER_SUCCESS,
 (see Section 7.1)) information is provided in the QIA message.  Note
 that the reserved QoS resources reported in the QIA message may be
 different than those initially authorized with the QIR message, due
 to the QoS signaling-specific behavior (e.g., receiver-initiated
 reservations with One-Path-With-Advertisements) or specific process
 of QoS negotiation along the data path.  In the case that Multiple
 AEs control the same NE, the NE should make the selection on the
 authorization decision to be enforced based on the priority of the
 request.

4.2.3. Discovery and Selection of Peer Diameter QoS Application Node

 The Diameter QoS application node may obtain information of its peer
 nodes (e.g., Fully-Qualified Domain Name (FQDN), IP address) through
 static configuration or dynamic discovery as described in Section 5.2
 of [RFC3588].  In particular, the NE shall perform the relevant
 operation for Pull mode; the AE shall perform the relevant operations
 for Push mode.
 Upon receipt of a trigger to initiate a new Diameter QoS
 authorization session, the Diameter QoS application node selects and
 retrieves the location information of the peer node that is
 associated with the affected user based on some index information
 provided by the RRE.  For instance, it can be the Authorization
 Entity's ID stored in the authorization token, the end-user identity
 (e.g., NAI [RFC4282]), or a globally routable IP address.

4.3. Session Re-Authorization

 Client- and server-side initiated re-authorizations are considered in
 the design of the Diameter QoS application.  Whether the
 re-authorization events are transparent for the resource requesting

Sun, et al. Standards Track [Page 24] RFC 5866 Diameter QoS Application May 2010

 entity or result in specific actions in the QoS signaling protocol is
 outside the scope of the Diameter QoS application.  It is directly
 dependent on the capabilities of the QoS signaling protocol.
 There are a number of options for policy rules according to which the
 NE (AAA client) contacts the AE for re-authorization.  These rules
 depend on the semantics and contents of the QAA message sent by the
 AE:
 a.  The QAA message contains the authorized parameters of the flow
     and its QoS and sets their limits (presumably upper).  With these
     parameters, the AE specifies the services that the NE can provide
     and for which it will be financially compensated.  Therefore, any
     change or request for change of the parameters of the flow and
     its QoS that do not conform to the authorized limits requires
     contacting the AE for authorization.
 b.  The QAA message contains authorized parameters of the flow and
     its QoS.  The rules that determine whether parameters' changes
     require re-authorization are agreed out of band, based on a
     Service Level Agreement (SLA) between the domains of the NE and
     the AE.
 c.  The QAA message contains the authorized parameters of the flow
     and its QoS.  Any change or request for change of these
     parameters requires contacting the AE for re-authorization.
 d.  In addition to the authorized parameters of the flow and its QoS,
     the QAA message contains policy rules that determine the NEs
     actions in case of a change or a request for change in authorized
     parameters.
 Provided options are not exhaustive.  Elaborating on any of the
 listed approaches is deployment/solution specific and is not
 considered in the current document.
 In addition, the AE may use an RAR (Re-Authorization-Request) to
 perform re-authorization with the authorized parameters directly when
 the re-authorization is triggered by service request or local events/
 policy rules.

4.3.1. Client-Side Initiated Re-Authorization

 The AE provides the duration of the authorization session as part of
 the QoS-Authorization-Answer (QAA) message.  At any time before the
 expiration of this period, a new QoS-Authorization-Request (QAR)
 message MAY be sent to the AE.  The transmission of the QAR MAY be
 triggered when the NE receives a QoS signaling message that requires

Sun, et al. Standards Track [Page 25] RFC 5866 Diameter QoS Application May 2010

 modification of the authorized parameters of an ongoing QoS session,
 or authorization lifetime expires.
                                             Authorizing
   End-Host         Network Element             Entity
 requesting QoS       (Diameter               (Diameter
                      QoS Client)             QoS Server)
     |                   |                         |
     |=====================Data Flow==========================>
     |                   |                         |
     |           +-------+----------+              |
     |           |Authz-time/CC-Time|              |
     |           |    expires       |              |
     |           +-------+----------+              |
     |                   +- - - - - QAR - - - - - >|
     |                   |(QoS-Resources,          |
     |                   | QoS-Authorization-Data,User-ID) |
                         |                +--------+--------------+
  NOTE:                  |                |  Authorize request    |
  Re-authorization       |                | Update session data   |
  is transparent to      |                |/Authz-time,Session-Id/|
  the End-Host           |                +--------+--------------+
                         |< - - - - QAA - - - - - -+
     |                   |(Result-Code,            |
     |                   |QoS-Resources,Authz-time)|
     |           +-------+---------+               |
     |           |Update QoS state |               |
     |           |       +         |               |
     |           | Authz  session  |               |
     |           | /Authz-time/    |               |
     |           |                 |               |
     |           +-------+---------+               |
     |                   |                         |
     |=====================Data Flow==========================>
     |                   |
         Figure 8: Client-side Initiated QoS Re-Authorization

4.3.2. Server-Side Initiated Re-Authorization

 The AE MAY initiate a QoS re-authorization by issuing a
 Re-Authorization-Request (RAR) message as defined in the Diameter
 base protocol [RFC3588], which may include the parameters of the
 re-authorized QoS state: reserved resources, duration of the
 reservation, identification of the QoS-enabled flow/QoS signaling
 session for re-installation of the resource state by the QoS Traffic
 Control function of the NE.

Sun, et al. Standards Track [Page 26] RFC 5866 Diameter QoS Application May 2010

 An NE that receives such an RAR message with Session-Id matching a
 currently active QoS session acknowledges the request by sending the
 Re-Auth-Answer (RAA) message towards the AE.
 If the RAR does not include any parameters of the re-authorized QoS
 state, the NE MUST initiate a QoS re-authorization by sending a
 QoS-Authorization-Request (QAR) message towards the AE.
                                             Authorizing
   End-Host         Network Element             Entity
 requesting QoS       (Diameter               (Diameter
                      QoS Client)             QoS Server)
     |                   |                          |
     |                   |                          |<-- Trigger --
     |                   |                 +--------+--------------+
     |                   |                 |  Authorize request    |
     |                   |                 |  Keep session data    |
     |                   |                 |/Authz-time,Session-Id/|
     |                   |                 +--------+--------------+
     |                   |                          |
     |                   |<-- - -- - RAR - - - - - -+
     |                   |(Request,Decision         |
     |                   |(QoS-Resources,Authz-time)|
     |           +-------+---------+
     |           |Install QoS state|
     |           |       +         |
     |           | Authz  session  |
     |           | /Authz-time/    |
     |           |                 |
     |           +-------+---------+
     |                   + - - - - RAA - - - - - ->|
     |                   |    (Result-Code,        |
     |                   |     QoS-Resources)      |
     |                   |                +--------+--------------+
     |                   |                | Report for successful |
     |                   |                |   QoS reservation     |
     |                   |                |Update of reserved QoS |
     |                   |                |      resources        |
     |                   |                +--------+--------------+
     |                   |                         |
         Figure 9: Server-Side Initiated QoS Re-Authorization

Sun, et al. Standards Track [Page 27] RFC 5866 Diameter QoS Application May 2010

4.4. Session Termination

4.4.1. Client-Side Initiated Session Termination

 The authorization session for an installed QoS reservation state MAY
 be terminated by the Diameter client by sending a Session-
 Termination-Request (STR) message to the Diameter server with a
 response Session-Termination-Acknowledgement (STA) message.  This is
 a Diameter base protocol function and it is defined in [RFC3588].
 Session termination can be caused by a QoS signaling message
 requesting deletion of the existing QoS reservation state, or it can
 be caused as a result of a soft-state expiration of the QoS
 reservation state.
                                             Authorizing
   End-Host         Network Element             Entity
 requesting QoS       (Diameter               (Diameter
                      QoS Client)             QoS Server)
     |                   |                         |
     |==Data Flow==>X /Stop of the data flow/      |
     |                   |                         |
     +---QoS-Reserve---->|                         |
     |  (Delete QoS      +- - - - - STR - - - - - >|
     |   reservation)    |                +--------+--------------+
     |                   |                | Remove authorization  |
     |                   |                | session state         |
     |                   |                +--------+--------------+
     |                   |< - - - - STA - - - - - -+
     |           +-------+--------+                |
     |           |Delete QoS state|
     |           +-------+--------+                   QoS Responder
     |                   |                                Node
     |                   +----------QoS-Reserve-----....--->|
     |                   |         (Delete QoS              |
     |                   |          reservation)            |
     |                   |<---------QoS-Response----....----+
     |<--QoS-Response----+                                  |
         Figure 10: Client-Side Initiated Session Termination

4.4.2. Server-Side Initiated Session Termination

 At any time during a session, the AE MAY send an Abort-Session-
 Request (ASR) message to the NE.  This is a Diameter base protocol
 function and it is defined in [RFC3588].  Possible reasons for
 initiating the ASR message to the NE are insufficient credits or
 session termination at the application layer.  The ASR message
 results in termination of the authorized session, release of the

Sun, et al. Standards Track [Page 28] RFC 5866 Diameter QoS Application May 2010

 reserved resources at the NE, and transmission of an appropriate QoS
 signaling message indicating a notification to other Network Elements
 aware of the signaling session.
                                             Authorizing
   End-Host         Network Element             Entity
 requesting QoS       (Diameter               (Diameter
                      QoS Client)             QoS Server)
     |                   |                         |
     |=====================Data Flow==========================>
     |                   |
     |                   |< - - - - ASR - - - - - -+
     |                   |                         |
     |====Data Flow=====>X                         |  QoS Responder
     |                   |                         |      Node
     |<--QoS-Notify------+----------QoS-Reserve-----....--->|
     |                   |         (Delete QoS     |        |
                         |          reservation)   |
                 +-------+--------+                |
                 |Delete QoS state|                |
                 +-------+--------+                |
                         +- - - - - ASA - - - - - >|
                         |                +--------+--------------+
                         |                | Remove authorization  |
                         |                |     session state     |
                         |                +--------+--------------+
                         |                            QoS Responder
                         |                                Node
                         |<---------QoS-Response----....----+
                         |                                  |
         Figure 11: Server-Side Initiated Session Termination

5. QoS Application Messages

 The Diameter QoS application requires the definition of new mandatory
 AVPs and Command-Codes (see Section 3 of [RFC3588]).  Four new
 Diameter messages are defined along with Command-Codes whose values
 MUST be supported by all Diameter implementations that conform to
 this specification.

Sun, et al. Standards Track [Page 29] RFC 5866 Diameter QoS Application May 2010

     +---------------------------+---------+------+-------------+
     | Command Name              | Abbrev. | Code | Reference   |
     +---------------------------+---------+------+-------------+
     | QoS-Authorization-Request |   QAR   |  326 | Section 5.1 |
     | QoS-Authorization-Answer  |   QAA   |  326 | Section 5.2 |
     | QoS-Install-Request       |   QIR   |  327 | Section 5.3 |
     | QoS-Install-Answer        |   QIA   |  327 | Section 5.4 |
     +---------------------------+---------+------+-------------+
                    Table 3: Diameter QoS Commands
 In addition, the following Diameter base protocol messages are used
 in the Diameter QoS application:
        +-----------------------+---------+------+-----------+
        | Command-Name          | Abbrev. | Code | Reference |
        +-----------------------+---------+------+-----------+
        | Re-Auth-Request       |   RAR   |  258 | [RFC3588] |
        | Re-Auth-Answer        |   RAA   |  258 | [RFC3588] |
        | Abort-Session-Request |   ASR   |  274 | [RFC3588] |
        | Abort-Session-Answer  |   ASA   |  274 | [RFC3588] |
        | Session-Term-Request  |   STR   |  275 | [RFC3588] |
        | Session-Term-Answer   |   STA   |  275 | [RFC3588] |
        +-----------------------+---------+------+-----------+
                    Table 4: Diameter Base Commands
 Diameter nodes conforming to this specification MAY advertise support
 for the Diameter QoS application by including the value of 9 in the
 Auth-Application-Id or the Acct-Application-Id AVP of the
 Capabilities-Exchange-Request and Capabilities-Exchange-Answer
 commands, see [RFC3588].
 The value of 9 MUST be used as the Application-Id in all QAR/QAA and
 QIR/QIA commands.
 The value of zero (0) SHOULD be used as the Application-Id in all
 STR/STA, ASR/ASA, and RAR/RAA commands.

5.1. QoS-Authorization Request (QAR)

 The QoS-Authorization-Request (QAR) message, indicated by the
 Command-Code field (see Section 3 of [RFC3588]) being set to 326 and
 the 'R' bit being set in the Command Flags field, is used by NEs to
 request quality of service related resource authorization for a given
 flow.

Sun, et al. Standards Track [Page 30] RFC 5866 Diameter QoS Application May 2010

 The QAR message MUST carry information for signaling session
 identification, AE identification, information about the requested
 QoS, and the identity of the QoS requesting entity.  In addition,
 depending on the deployment scenario, an authorization token and
 credentials of the QoS requesting entity SHOULD be included.
 The message format is defined as follows:
  <QoS-Authorization-Request> ::= < Diameter Header: 326, REQ, PXY >
                                  < Session-Id >
                                  { Auth-Application-Id }
                                  { Origin-Host }
                                  { Origin-Realm }
                                  { Destination-Realm }
                                  { Auth-Request-Type }
                                  [ Destination-Host ]
                                  [ User-Name ]
                               *  [ QoS-Resources ]
                                  [ QoS-Authorization-Data ]
                                  [ Bound-Auth-Session-Id ]
                               *  [ AVP ]

5.2. QoS-Authorization-Answer (QAA)

 The QoS-Authorization-Answer (QAA) message, indicated by the Command-
 Code field being set to 326 and the 'R' bit being cleared in the
 Command Flags field, is sent in response to the QoS-Authorization-
 Request (QAR) message.  If the QoS authorization request is
 successfully authorized, the response will include the AVPs to allow
 authorization of the QoS resources and transport plane gating
 information.
 The message format is defined as follows:
  <QoS-Authorization-Answer> ::= < Diameter Header: 326, PXY >
                                 < Session-Id >
                                 { Auth-Application-Id }
                                 { Auth-Request-Type }
                                 { Result-Code }
                                 { Origin-Host }
                                 { Origin-Realm }
                              *  [ QoS-Resources ]
                                 [ Acct-Multisession-Id ]
                                 [ Session-Timeout ]
                                 [ Authorization-Session-Lifetime ]
                                 [ Authorization-Grace-Period ]
                              *  [ AVP ]

Sun, et al. Standards Track [Page 31] RFC 5866 Diameter QoS Application May 2010

5.3. QoS-Install Request (QIR)

 The QoS-Install Request (QIR) message, indicated by the Command-Code
 field being set to 327 and the 'R' bit being set in the Command Flags
 field, is used by the AE to install or update the QoS parameters and
 the flow state of an authorized flow at the transport plane element.
 The message MUST carry information for signaling-session
 identification or identification of the flow to which the provided
 QoS rules apply, identity of the transport plane element, description
 of provided QoS parameters, flow state, and duration of the provided
 authorization.
 The message format is defined as follows:
  <QoS-Install-Request> ::= < Diameter Header: 327, REQ, PXY >
                            < Session-Id >
                            { Auth-Application-Id }
                            { Origin-Host }
                            { Origin-Realm }
                            { Destination-Realm }
                            { Auth-Request-Type }
                            [ Destination-Host ]
                         *  [ QoS-Resources ]
                            [ Session-Timeout ]
                            [ Authorization-Session-Lifetime ]
                            [ Authorization-Grace-Period ]
                            [ Authorization-Session-Volume ]
                         *  [ AVP ]

5.4. QoS-Install Answer (QIA)

 The QoS-Install Answer (QIA) message, indicated by the Command-Code
 field being set to 327 and the 'R' bit being cleared in the Command
 Flags, field is sent in response to the QoS-Install Request (QIR)
 message for confirmation of the result of the installation of the
 provided QoS reservation instructions.
 The message format is defined as follows:
   <QoS-Install-Answer> ::= < Diameter Header: 327, PXY >
                            < Session-Id >
                            { Auth-Application-Id }
                            { Origin-Host }
                            { Origin-Realm }
                            { Result-Code }
                         *  [ QoS-Resources ]
                         *  [ AVP ]

Sun, et al. Standards Track [Page 32] RFC 5866 Diameter QoS Application May 2010

5.5. Re-Auth-Request (RAR)

 The Re-Auth-Request (RAR) message, indicated by the Command-Code
 field being set to 258 and the 'R' bit being set in the Command Flags
 field, is sent by the AE to the NE in order to initiate the QoS
 re-authorization from the DQA server side.
 If the RAR command is received by the NE without any parameters of
 the re-authorized QoS state, the NE MUST initiate a QoS
 re-authorization by sending a QoS-Authorization-Request (QAR) message
 towards the AE.
 The message format is defined as follows:
       <RAR>  ::= < Diameter Header: 258, REQ, PXY >
                  < Session-Id >
                  { Origin-Host }
                  { Origin-Realm }
                  { Destination-Realm }
                  { Destination-Host }
                  { Auth-Application-Id }
                  { Re-Auth-Request-Type }
                  [ User-Name ]
                  [ Origin-State-Id ]
                * [ Proxy-Info ]
                * [ Route-Record ]
                * [ QoS-Resources ]
                  [ Session-Timeout ]
                  [ Authorization-Session-Lifetime ]
                  [ Authorization-Grace-Period ]
                  [ Authorization-Session-Volume ]
                * [ AVP ]

Sun, et al. Standards Track [Page 33] RFC 5866 Diameter QoS Application May 2010

5.6. Re-Auth-Answer (RAA)

 The Re-Auth-Answer (RAA) message, indicated by the Command-Code field
 being set to 258 and the 'R' bit being cleared in the Command Flags
 field, is sent by the NE to the AE in response to the RAR command.
 The message format is defined as follows:
       <RAA>  ::= < Diameter Header: 258, PXY >
                  < Session-Id >
                  { Result-Code }
                  { Origin-Host }
                  { Origin-Realm }
                  [ User-Name ]
                  [ Origin-State-Id ]
                  [ Error-Message ]
                  [ Error-Reporting-Host ]
                * [ Failed-AVP ]
                * [ Redirect-Host ]
                  [ Redirect-Host-Usage ]
                  [ Redirect-Host-Max-Cache-Time ]
                * [ Proxy-Info ]
                * [ QoS-Resources ]
                * [ AVP ]

6. QoS Application State Machine

 The QoS application defines its own state machine that is based on
 the authorization state machine defined in Section 8.1 of the
 Diameter base protocol ([RFC3588]).  The QoS state machine uses its
 own messages, as defined in Section 5, and QoS AVPs, as defined in
 Section 7.

6.1. Supplemented States for Push Mode

 Using the Diameter base protocol state machine as a basis, the
 following states are supplemented to the first two state machines in
 which the session state is maintained on the server.  These MUST be
 supported in any QoS application implementations in support of
 server-initiated Push mode (see Section 4.2.2).

Sun, et al. Standards Track [Page 34] RFC 5866 Diameter QoS Application May 2010

 The following states are supplemented to the state machine on the
 server when state is maintained on the client, as defined in Section
 8.1 of the Diameter base protocol[RFC3588]:
                               SERVER, STATEFUL
       State     Event                          Action     New State
       -------------------------------------------------------------
       Idle      An application or local        Send        Pending
                 event triggers an initial      QIR initial
                 QoS request to the server      request
       Pending   Received QIA with a failed     Clean up    Idle
                 Result-Code
       Pending   Received QIA with Result-Code  Update      Open
                 = SUCCESS                      session
       Pending   Error in processing received   Send        Discon
                 QIA with Result-Code = SUCCESS ASR
 The following states are supplemented to the state machine on the
 client when state is maintained on the server, as defined in Section
 8.1 of the Diameter base protocol [RFC3588]:
                               CLIENT, STATEFUL
       State     Event                          Action     New State
       -------------------------------------------------------------
       Idle      QIR initial request            Send         Open
                 received and successfully      QIA initial
                 processed                      answer,
                                                reserve
                                                resources
       Idle      QIR initial request            Send         Idle
                 received but not               QIA initial
                 successfully processed         answer with
                                                Result-Code
                                                != SUCCESS

7. QoS Application AVPs

 Each of the AVPs identified in the QoS-Authorization-Request/Answer
 and QoS-Install-Request/Answer messages and the assignment of their
 value(s) is given in this section.

Sun, et al. Standards Track [Page 35] RFC 5866 Diameter QoS Application May 2010

7.1. Reused Base Protocol AVPs

 The QoS application uses a number of session management AVPs, defined
 in the base protocol ([RFC3588]).
 Attribute Name                AVP Code     Reference [RFC3588]
 Origin-Host                   264          Section 6.3
 Origin-Realm                  296          Section 6.4
 Destination-Host              293          Section 6.5
 Destination-Realm             283          Section 6.6
 Auth-Application-Id           258          Section 6.8
 Result-Code                   268          Section 7.1
 Auth-Request-Type             274          Section 8.7
 Session-Id                    263          Section 8.8
 Authorization-Lifetime        291          Section 8.9
 Auth-Grace-Period             276          Section 8.10
 Session-Timeout                27          Section 8.13
 User-Name                       1          Section 8.14
 The Auth-Application-Id AVP (AVP Code 258) is assigned by IANA to
 Diameter applications.  The value of the Auth-Application-Id for the
 Diameter QoS application is 9.

7.2. QoS Application-Defined AVPs

 This document reuses the AVPs defined in Section 4 of [RFC5777].
 This section lists the AVPs that are introduced specifically for the
 QoS application.  The following new AVPs are defined: Bound-Auth-
 Session-Id and the QoS-Authorization-Data AVP.
 The following table describes the Diameter AVPs newly defined in this
 document for use with the QoS Application, their AVP code values,
 types, possible flag values, and to determine whether the AVP may be
 encrypted.

Sun, et al. Standards Track [Page 36] RFC 5866 Diameter QoS Application May 2010

                                                +-------------------+
                                                |    AVP Flag rules |
 +----------------------------------------------|----+--------+-----+
 |                       AVP  Section           |    |    SHLD| MUST|
 | Attribute Name        Code Defined Data Type |MUST|     NOT|  NOT|
 +----------------------------------------------+----+--------+-----+
 |QoS-Authorization-Data 579    7.2  OctetString| M  |        |  V  |
 |Bound-Auth-Session-Id  580    7.2  UTF8String | M  |        |  V  |
 +----------------------------------------------+----+--------+-----+
 |M - Mandatory bit. An AVP with the "M" bit set and its value MUST |
 |    be supported and recognized by a Diameter entity in order for |
 |    the message, which carries this AVP, to be accepted.          |
 |V - Vendor-specific bit that indicates whether the AVP belongs to |
 |    an address space.                                              |
 +------------------------------------------------------------------+
 QoS-Authorization-Data
    The QoS-Authorization-Data AVP (AVP Code 579) is of type
    OctetString.  It is a container that carries application-session
    or user-specific data that has to be supplied to the AE as input
    to the computation of the authorization decision.
 Bound-Authentication-Session-Id
    The Bound-Authentication-Session AVP (AVP Code 580) is of type
    UTF8String.  It carries the ID of the Diameter authentication
    session that is used for the network access [RFC4005].  It is used
    to tie the QoS authorization request to a prior authentication of
    the end-host done by a co-located application for network access
    authentication ([RFC4005]) at the QoS NE.

8. Accounting

 An NE MAY start an accounting session by sending an Accounting-
 Request (ACR) message after successful QoS reservation and activation
 of the data flow (see Figures 6 and 7).  After every successful re-
 authorization procedure (see Figures 8 and 9), the NE MAY initiate an
 interim accounting message exchange.  After successful session
 termination (see Figures 10 and 11), the NE may initiate a final
 exchange of accounting messages for the termination of the accounting
 session and report final records for the use of the QoS resources
 reserved.  It should be noted that the two sessions (authorization
 and accounting) have independent management by the Diameter base
 protocol, which allows for finalizing the accounting session after
 the end of the authorization session.
 The detailed QoS accounting procedures are out of scope in this
 document.

Sun, et al. Standards Track [Page 37] RFC 5866 Diameter QoS Application May 2010

9. Examples

9.1. Example Call Flow for Pull Mode (Success Case)

 This section presents an example of the interaction between the end-
 host and Diameter QoS application entities using Pull mode.  The
 application-layer signaling is, in this example, provided using SIP.
 Signaling for a QoS resource reservation is done using the QoS NSIS
 Signaling Layer Protocol (NSLP).  The authorization of the QoS
 reservation request is done by the Diameter QoS application (DQA).
   End-Host                                 SIP Proxy  Correspondent
 requesting QoS                            (DQA Server)        Node
       |                                          |              |
     ..|....Application-layer SIP signaling.......|..............|..
     . |  Invite (SDP)                            |              | .
     . +.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.->              | .
     . |  100 Trying                              |              | .
     . <.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-+  Invite (SDP)| .
     . |                                          +-.-.-.....-.-.> .
     . |                                          |  180 SDP'    | .
     . |                                          <-.-.-.....-.-.+ .
     . |                                 +--------+--------+     | .
     . |                                 |Authorize session|     | .
     . |                                 |   parameters    |     | .
     . | 180 (Session parameters)        +--------+--------+     | .
     . <.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-+              | .
     ..|..........................................|... ..........|..
       |                                          |              |
       |           +------------+                 |              |
       |           |     NE     |                 |              |
       |           |(DQA Client)|                 |              |
       |           +------+-----+                 |              |
       |                  |                       |              |
       |QoS NSLP Reserve  |                       |              |
       +------------------> QAR                   |              |
       | (POLICY_DATA>v   +- - - - -<<AAA>>- - - ->              |
       |  QSPEC)  v   >===>(Destination-Host,     |              |
       |      v   >=======>QoS-Authorization-Data++------------+ |
       |      >===========>QoS-Resources)        |Authorize    | |
       |                  |                      |QoS resources| |
       |                  |                      ++------------+ |
       |                  | QAA                   |              |
       |                  <- - - - -<<AAA>>- - - -+              |
       |                  |(Result-Code,          |              |
       |                  |QoS-Resources,         |              |
       |                  |Authorization-Lifetime)|              |

Sun, et al. Standards Track [Page 38] RFC 5866 Diameter QoS Application May 2010

       |        +---------+--------+              |              |
       |        |Install QoS state1|              |              |
       |        |+ Authz  session  |              |              |
       |        +---------+--------+              |              |
       |                  |QoS NSLP Reserve                      |
       |                  +---------------..............--------->
       |                  |                                      |
       |                  |                     QoS NSLP Response|
       |QoS NSLP Response <---------------..............---------+
       <------------------+                                      |
       |                  |                        QoS NSLP Query|
       |QoS NSLP Query    <---------------..............---------+
       <------------------+                                      |
       |QoS NSLP Reserve  |                                      |
       +------------------> QAR                   |              |
       |                  +- - - - -<<AAA>>- - - ->              |
       |                  |                   +---+---------+    |
       |                  |                   |Authorize    |    |
       |                  |                   |QoS resources|    |
       |                  | QAA               +---+---------+    |
       |                  <- - - - -<<AAA>>- - - -+              |
       |        +---------+--------+              |              |
       |        |Install QoS state2|                             |
       |        |+ Authz  session  |                             |
       |        +---------+--------+                             |
       |                  |  QoS NSLP Reserve                    |
       |                  +---------------..............--------->
       |                  |                     QoS NSLP Response|
       |QoS NSLP Response <---------------..............---------+
       <------------------+                                      |
       |                  |                                      |
       /------------------+--Data Flow---------------------------\
       \------------------+--------------------------------------/
       |                  |                                      |
       .-.-.-.-.  SIP signaling
       ---------  QoS NSLP signaling
       - - - - -  Diameter QoS Application messages
       =========  Mapping of objects between QoS and AAA protocol
           Figure 12: QoS Authorization Example - Pull Mode

Sun, et al. Standards Track [Page 39] RFC 5866 Diameter QoS Application May 2010

 The communication starts with SIP signaling between the two endpoints
 and the SIP proxy for negotiation and authorization of the requested
 service and its parameters (see Figure 12).  As a part of the
 process, the SIP proxy verifies whether the user at Host A is
 authorized to use the requested service (and potentially the ability
 to be charged for the service usage).  Negotiated session parameters
 are provided to the end-host.
 Subsequently, Host A initiates a QoS signaling message towards Host
 B. It sends a QoS NSLP Reserve message, in which it includes
 description of the required QoS (QSPEC object) and authorization data
 for negotiated service session (part of the POLICY_DATA object).
 Authorization data includes, as a minimum, the identity of the AE
 (e.g., the SIP proxy) and an identifier of the application-service
 session for which QoS resources are requested.
 A QoS NSLP reserve message is intercepted and processed by the first
 QoS-aware Network Element.  The NE uses the Diameter QoS application
 to request authorization for the received QoS reservation request.
 The identity of the AE (in this case, the SIP server that is co-
 located with a Diameter server) is put into the Destination-Host AVP,
 any additional session authorization data is encapsulated into the
 QoS-Authorization-Data AVP, and the description of the QoS resources
 is included into the QoS-Resources AVP.  These AVPs are included into
 a QoS Authorization Request message, which is sent to the AE.
 A QAR message will be routed through the AAA network to the AE.  The
 AE verifies the requested QoS against the QoS resources negotiated
 for the service session and replies with a QoS-Authorization-Answer
 (QAA) message.  It carries the authorization result (Result-Code AVP)
 and the description of the authorized QoS parameters (QoS-Resources
 AVP), as well as duration of the authorization session
 (Authorization-Lifetime AVP).
 The NE interacts with the Traffic Control function and installs the
 authorized QoS resources and forwards the QoS NSLP reserve message
 farther along the data path.  Moreover, the NE may serve as a
 signaling proxy and process the QoS signaling (e.g., initiation or
 termination of QoS signaling) based on the QoS decision received from
 the Authorizing Entity.

9.2. Example Call Flow for Pull Mode (Failure Case)

 This section repeats the scenario outlined in Section 9.1; however,
 in this case, we show a session authorization failure instead of
 success.  Failures can occur in various steps throughout the protocol
 execution, and in this example, we assume that the Diameter QAR
 request processed by the Diameter server leads to an unsuccessful

Sun, et al. Standards Track [Page 40] RFC 5866 Diameter QoS Application May 2010

 result.  The QAA message responds, in this example, with a permanent
 error "DIAMETER_AUTHORIZATION_REJECTED" (5003) set in the Result-Code
 AVP.  When the NE receives this response, it discontinues the QoS
 reservation signaling downstream and provides an error message back
 to the end-host that initiated the QoS signaling request.  The QoS
 NSLP response signaling message would in this case carry an INFO_SPEC
 object indicating the permanent failure as "Authorization failure"
 (0x02).

Sun, et al. Standards Track [Page 41] RFC 5866 Diameter QoS Application May 2010

   End-Host                                 SIP Proxy  Correspondent
 requesting QoS                            (DQA Server)        Node
       |                                          |              |
     ..|...................SIP Signaling..........|..............|..
     . |  Invite (SDP)                            |              | .
     . +.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.->              | .
     . |  100 Trying                              |              | .
     . <.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-+  Invite (SDP)| .
     . |                                          +-.-.-.....-.-.> .
     . |                                          |  180 SDP'    | .
     . |                                          <-.-.-.....-.-.+ .
     . |                                 +--------+--------+     | .
     . |                                 |Authorize session|     | .
     . |                                 |   parameters    |     | .
     . | 180 (Session parameters)        +--------+--------+     | .
     . <.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-+              | .
     ..|..........................................|... ..........|..
       |                                          |              |
       |           +------------+                 |              |
       |           |     NE     |                 |              |
       |           |(DQA Client)|                 |              |
       |           +------+-----+                 |              |
       |                  |                       |              |
       |QoS NSLP Reserve  |                       |              |
       +------------------> QAR                   |              |
       | (POLICY_DATA>v   +- - - - -<<AAA>>- - - ->              |
       |  QSPEC)  v   >===>(Destination-Host,     |              |
       |      v   >=======>QoS-Authorization-Data++------------+ |
       |      >===========>QoS-Resources)        |Authorize    | |
       |                  |                      |QoS resources| |
       |                  |                      ++------------+ |
       |                  | QAA                   |              |
       |                  <- - - - -<<AAA>>- - - -+              |
       |                  |(Result-Code = 5003)   |              |
       |                  |                       |              |
       |QoS NSLP Response |                       |              |
       |(with error 0x02) |                       |              |
       <------------------+                       |              |
       |                  |                       |              |
       |                  |                       |              |
       .-.-.-.-.  SIP signaling
       ---------  QoS NSLP signaling
       - - - - -  Diameter QoS Application messages
       =========  Mapping of objects between QoS and AAA protocol
    Figure 13: QoS Authorization Example - Pull Mode (Failure Case)

Sun, et al. Standards Track [Page 42] RFC 5866 Diameter QoS Application May 2010

9.3. Example Call Flow for Push Mode

 This section presents an example of the interaction between the end-
 host and Diameter QoS application entities using Push mode.  The
 application-layer signaling is, in this example, provided using SIP.
 Signaling for a QoS resource reservation is done using the QoS NSLP.
 The authorization of the QoS reservation request is done by the
 Diameter QoS application (DQA).
  End-Host              NE                  SIP Proxy  Correspondent
requesting QoS      (DQA Client)           (DQA Server)        Node
      |                  |                          |              |
    ..|..................|...SIP Signaling..........|..............|..
    . | Invite(SDP Offer)|                          |              | .
    . +.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.+-.-.-.-.-.-.->| .
    . |                  |                          |   180        | .
    . |<-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.+-.-.-.-.-.-.-.| .
    ..|.............................................|..............|..
      |                  |                +---------+-------------+|
      |                  |                |  Authorize Request    ||
      |                  |                |  Keep Session Data    ||
      |                  |                |/Authz-time,Session-Id/||
      |                  |                +---------+-------------+|
      |                  |                          |              |
      |                  |<-- - -- - QIR - -- - -- -+              |
      |                  |(Initial Request,Decision |              |
      |                  |(QoS-Resources,Authz-time)|              |
      |          +-------+---------+                |              |
      |          |Install QoS State|                |              |
      |          |       +         |                |              |
      |          | Authz  Session  |                |              |
      |          | /Authz-time/    |                |              |
      |          +-------+---------+                |              |
      |                  + - - -- - QIA - - - - - ->|              |
      |                  |     (Result-Code,        |              |
      |                  |      QoS-Resources)      |              |
      |                  |               +----------+------------+ |
      |                  |               |     Successful        | |
      |                  |               |     QoS Reservation   | |
      |                  |               +----------+------------+ |

Sun, et al. Standards Track [Page 43] RFC 5866 Diameter QoS Application May 2010

    ..|.............................................|..............|..
    . |                  |                          |              | .
    . |                  |                          |  200 OK (SDP)| .
    . |                  |                          <-.-.-.....-.-.+ .
    . |                  |                 +--------+-----------+  | .
    . |                  |                 |   Activate Session |  | .
    . |                  |                 |   Parameters       |  | .
    . |                  |                 +--------+-----------+  | .
    . | 200 (SDP)        |                          |              | .
    . <.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.+              | .
    ..|.............................................|..............|..
      |                  <- - - - - - RAR - - - - - +              |
      |        +---------+--------+                 |              |
      |        |Activate QoS State|                 |              |
      |        +---------+--------+                 |              |
      |                  +- - - - - - RAA - - - - - >              |
      |                  |                                         |
      /------------------+-----Data Flow---------------------------\
      \------------------+-----------------------------------------/
      |                  |                                         |
      .-.-.-.-.  SIP signaling
      - - - - -  Diameter QoS Application messages
           Figure 14: QoS Authorization Example - Push Mode
 The communication starts with SIP signaling between the two endpoints
 and the SIP proxy for negotiation and authorization of the requested
 service and its parameters (see Figure 14).  As a part of the
 process, the SIP proxy verifies whether the user at Host A is
 authorized to use the requested service (and potentially the ability
 to be charged for the service usage).
 A few implementation choices exist regarding the decision about when
 to initiate the QoS reservation.  [MMUSIC-MEDIA] discusses this
 aspect with a focus on firewalling.  In the example above, the DQA
 server is triggered to authorize the QoS request based on session
 parameters from the Session Description Protocol (SDP) payload.  It
 will use a QIR message to do so.  For this example message flow, we
 assume a two-stage commit, i.e., the SIP proxy interacts with the NE
 twice.  First, it only prepares the QoS reservation, and then, with
 the arrival of the 200 OK, the QoS reservation is activated.
 This example does not describe how the DQA server learns which DQA
 client to contact.  We assume pre-configuration in this example.  In
 any case, the address of the DQA client is put into the Destination-
 Host AVP, the description of the QoS resources is included into the

Sun, et al. Standards Track [Page 44] RFC 5866 Diameter QoS Application May 2010

 QoS-Resources AVP, and the duration of the authorization session is
 carried in the Authorization-Lifetime AVP.
 When the DQA client receives the QIR, it interacts with the Traffic
 Control function and reserves the authorized QoS resources
 accordingly.  At this point in time, the QoS reservation is not yet
 activated.
 When a 200 OK is returned, the DQA server may verify the accepted QoS
 against the pre-authorized QoS resources and send a Diameter RAR
 message to the DQA client in the NE for activating the installed
 policies and commit the resource allocation.

10. IANA Considerations

 This section contains the namespaces that have either been created in
 this specification or had their values assigned to existing
 namespaces managed by IANA.

10.1. AVP Codes

 IANA has allocated two AVP codes to the registry defined in
 [RFC3588]:
 Registry:
 AVP Code         AVP Name                      Reference
 -----------------------------------------------------------
   579        QoS-Authorization-Data           Section 7.2
   580        Bound-Auth-Session-Id            Section 7.2

10.2. Application IDs

 IANA has allocated the following application ID from the registry
 defined in [RFC3588] (using the next available value from the
 7-16777215 range).
 Registry:
 ID values           Name                         Reference
 -----------------------------------------------------------
   9           Diameter QoS application           Section 5

Sun, et al. Standards Track [Page 45] RFC 5866 Diameter QoS Application May 2010

10.3. Command Codes

 IANA has allocated command code values from the registry defined in
 [RFC3588].
 Registry:
 Code Value  Name                                Reference
 -----------------------------------------------------------
 326         QoS-Authorization-Request (QAR)     Section 5.1
 326         QoS-Authorization-Answer  (QAA)     Section 5.2
 327         QoS-Install-Request (QIR)           Section 5.3
 327         QoS-Install-Answer (QIA)            Section 5.4

11. Security Considerations

 This document describes a mechanism for performing authorization of a
 QoS reservation at a third-party entity.  The Authorizing Entity
 needs sufficient information to make such an authorization decision
 and this information may come from various sources, including the
 application-layer signaling, the Diameter protocol (with its security
 mechanisms), policy information stored available with a AAA server,
 and a QoS signaling protocol.
 Below there is a discussion about considerations for the Diameter QoS
 interaction between an Authorizing Entity and a Network Element.
 Security between the Authorizing Entity and the Network Element has a
 number of components: authentication, authorization, integrity, and
 confidentiality.
 Authentication refers to confirming the identity of an originator for
 all datagrams received from the originator.  Lack of authentication
 of Diameter messages between the Authorizing Entity and the Network
 Element can seriously jeopardize the fundamental service rendered by
 the Network Element.  A consequence of not authenticating the message
 sender by the Network Element would be that an attacker could spoof
 the identity of a "legitimate" Authorizing Entity in order to
 allocate resources, change resource assignments, or free resources.
 The adversary can also manipulate the state at the Network Element in
 such a way that it leads to a denial-of-service attack by, for
 example, setting the allowed bandwidth to zero or allocating the
 entire bandwidth available to a single flow.
 A consequence of not authenticating the Network Element to an
 Authorizing Entity is that an attacker could impact the policy-based
 admission control procedure operated by the Authorizing Entity that
 provides a wrong view of the resources used in the network.  Failing
 to provide the required credentials should be subject to logging.

Sun, et al. Standards Track [Page 46] RFC 5866 Diameter QoS Application May 2010

 Authorization refers to whether a particular Authorizing Entity is
 authorized to signal a Network Element with requests for one or more
 applications, adhering to a certain policy profile.  Failing the
 authorization process might indicate a resource theft attempt or
 failure due to administrative and/or credential deficiencies.  In
 either case, the Network Element should take the proper measures to
 log such attempts.
 Integrity is required to ensure that a Diameter message has not been
 maliciously altered.  The result of a lack of data integrity
 enforcement in an untrusted environment could be that an imposter
 will alter the messages exchanged between a Network Entity and an
 Authorizing Entity potentially causing a denial of service.
 Confidentiality protection of Diameter messages ensures that the
 signaling data is accessible only to the authorized entities.  When
 signaling messages from the Application Server (via the Authorizing
 Entity towards the Network Element) traverse untrusted networks, lack
 of confidentiality will allow eavesdropping and traffic analysis.
 Additionally, Diameter QoS messages may carry authorization tokens
 that require confidentiality protection.
 Diameter offers security mechanisms to deal with the functionality
 demanded in the paragraphs above.  In particular, Diameter offers
 communication security between neighboring Diameter peers using
 Transport Layer Security (TLS) or IPsec.  Authorization capabilities
 are application specific and part of the overall implementation.

12. Acknowledgements

 The authors would like to thank John Loughney and Allison Mankin for
 their input to this document.  In September 2005, Robert Hancock,
 Jukka Manner, Cornelia Kappler, Xiaoming Fu, Georgios Karagiannis,
 and Elwyn Davies provided a detailed review.  Robert also provided us
 with good feedback earlier in 2005.  Jerry Ash provided us review
 comments in late 2005/early 2006.  Rajith R provided some inputs to
 the document in early 2007.
 We would also like to thanks Alexey Melnikov, Adrian Farrel, and
 Robert Sparks for their IESG reviews.

13. Contributors

 The authors would like to thank Tseno Tsenov and Frank Alfano for
 starting the Diameter Quality of Service work within the IETF, for
 their significant contributions and for being the driving force for
 the first few draft versions.

Sun, et al. Standards Track [Page 47] RFC 5866 Diameter QoS Application May 2010

14. References

14.1. Normative References

 [RFC2119]       Bradner, S., "Key words for use in RFCs to Indicate
                 Requirement Levels", BCP 14, RFC 2119, March 1997.
 [RFC3588]       Calhoun, P., Loughney, J., Guttman, E., Zorn, G., and
                 J. Arkko, "Diameter Base Protocol", RFC 3588,
                 September 2003.
 [RFC4005]       Calhoun, P., Zorn, G., Spence, D., and D. Mitton,
                 "Diameter Network Access Server Application",
                 RFC 4005, August 2005.
 [RFC5624]       Korhonen, J., Tschofenig, H., and E. Davies, "Quality
                 of Service Parameters for Usage with Diameter",
                 RFC 5624, August 2009.
 [RFC5777]       Korhonen, J., Tschofenig, H., Arumaithurai, M.,
                 Jones, M., and A. Lior, "Traffic Classification and
                 Quality of Service (QoS) Attributes for Diameter",
                 RFC 5777, February 2010.

14.2. Informative References

 [MMUSIC-MEDIA]  Stucker, B. and H. Tschofenig, "Analysis of Middlebox
                 Interactions for Signaling Protocol Communication
                 along the Media Path", Work in Progress, March 2009.
 [NSIS-NTLP]     Schulzrinne, H. and M. Stiemerling, "GIST: General
                 Internet Signalling Transport", Work in Progress,
                 June 2009.
 [NSIS-QOS]      Manner, J., Karagiannis, G., and A. McDonald, "NSLP
                 for Quality-of-Service Signaling", Work in Progress,
                 January 2010.
 [RFC2205]       Braden, B., Zhang, L., Berson, S., Herzog, S., and S.
                 Jamin, "Resource ReSerVation Protocol (RSVP) --
                 Version 1 Functional Specification", RFC 2205,
                 September 1997.
 [RFC2211]       Wroclawski, J., "Specification of the Controlled-Load
                 Network Element Service", RFC 2211, September 1997.

Sun, et al. Standards Track [Page 48] RFC 5866 Diameter QoS Application May 2010

 [RFC2212]       Shenker, S., Partridge, C., and R. Guerin,
                 "Specification of Guaranteed Quality of Service",
                 RFC 2212, September 1997.
 [RFC2474]       Nichols, K., Blake, S., Baker, F., and D. Black,
                 "Definition of the Differentiated Services Field (DS
                 Field) in the IPv4 and IPv6 Headers", RFC 2474,
                 December 1998.
 [RFC2753]       Yavatkar, R., Pendarakis, D., and R. Guerin, "A
                 Framework for Policy-based Admission Control",
                 RFC 2753, January 2000.
 [RFC2865]       Rigney, C., Willens, S., Rubens, A., and W. Simpson,
                 "Remote Authentication Dial In User Service
                 (RADIUS)", RFC 2865, June 2000.
 [RFC3261]       Rosenberg, J., Schulzrinne, H., Camarillo, G.,
                 Johnston, A., Peterson, J., Sparks, R., Handley, M.,
                 and E. Schooler, "SIP: Session Initiation Protocol",
                 RFC 3261, June 2002.
 [RFC3313]       Marshall, W., "Private Session Initiation Protocol
                 (SIP) Extensions for Media Authorization", RFC 3313,
                 January 2003.
 [RFC3520]       Hamer, L-N., Gage, B., Kosinski, B., and H. Shieh,
                 "Session Authorization Policy Element", RFC 3520,
                 April 2003.
 [RFC3521]       Hamer, L-N., Gage, B., and H. Shieh, "Framework for
                 Session Set-up with Media Authorization", RFC 3521,
                 April 2003.
 [RFC4282]       Aboba, B., Beadles, M., Arkko, J., and P. Eronen,
                 "The Network Access Identifier", RFC 4282,
                 December 2005.
 [RFC4566]       Handley, M., Jacobson, V., and C. Perkins, "SDP:
                 Session Description Protocol", RFC 4566, July 2006.
 [RFC5246]       Dierks, T. and E. Rescorla, "The Transport Layer
                 Security (TLS) Protocol Version 1.2", RFC 5246,
                 August 2008.

Sun, et al. Standards Track [Page 49] RFC 5866 Diameter QoS Application May 2010

Authors' Addresses

 Dong Sun (editor)
 Alcatel-Lucent
 600 Mountain Ave
 Murray Hill, NJ  07974
 USA
 Phone: +1 908 582 2617
 EMail: d.sun@alcatel-lucent.com
 Peter J. McCann
 Motorola Labs
 1301 E. Algonquin Rd
 Schaumburg, IL  60196
 USA
 Phone: +1 847 576 3440
 EMail: pete.mccann@motorola.com
 Hannes Tschofenig
 Nokia Siemens Networks
 Linnoitustie 6
 Espoo  02600
 Finland
 Phone: +358 (50) 4871445
 EMail: Hannes.Tschofenig@gmx.net
 URI:   http://www.tschofenig.priv.at
 Tina Tsou
 Huawei
 Shenzhen,
 P.R.C
 EMail: tena@huawei.com
 Avri Doria
 Lulea University of Technology
 Arbetsvetenskap
 Lulea,   SE-97187
 Sweden
 EMail: avri@ltu.se

Sun, et al. Standards Track [Page 50] RFC 5866 Diameter QoS Application May 2010

 Glen Zorn (editor)
 Network Zen
 1310 East Thomas Street
 #306
 Seattle, Washington  98102
 USA
 Phone: +1 (206) 377-9035
 EMail: gwz@net-zen.net

Sun, et al. Standards Track [Page 51]

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