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RFC 5866

Diameter Quality-of-Service Application

Pages: 51
Proposed Standard
Part 1 of 3 – Pages 1 to 17
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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
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   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
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   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].
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   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.
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   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.
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   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.
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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
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   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].
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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.
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   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.
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                                        +--------------+
                                        | 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.
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                               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
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   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
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   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:
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   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.
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   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.
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   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.



(page 17 continued on part 2)

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