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Authentication, Authorization and                              F. Alfano
Accounting                                                     P. McCann
Internet-Draft                                       Lucent Technologies
Expires: March 9, 2006                                     H. Tschofenig
                                                               T. Tsenov
                                                                 Siemens
                                                       September 5, 2005


                Diameter Quality of Service Application
                    draft-alfano-aaa-qosprot-04.txt

Status of this Memo

   By submitting this Internet-Draft, each author represents that any
   applicable patent or other IPR claims of which he or she is aware
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   This Internet-Draft will expire on March 9, 2006.

Copyright Notice

   Copyright (C) The Internet Society (2005).

Abstract

   This document describes a Diameter application that performs
   Authentication, Authorization, and Accounting for Quality of Service
   (QoS) reservations.  This protocol is used by elements along the path
   of a given application flow to authenticate a reservation request,
   ensure that the reservation is authorized, and to account for



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   resources consumed during the lifetime of the application flow.
   Clients that implement the Diameter QoS application contact an
   authorizing entity/application server that is located somewhere in
   the network, allowing for a wide variety of flexible deployment
   models.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  5
   3.  Framework  . . . . . . . . . . . . . . . . . . . . . . . . . .  6
     3.1.  Network element functional model . . . . . . . . . . . . .  7
     3.2.  Authorization models . . . . . . . . . . . . . . . . . . .  9
     3.3.  QoS authorization considerations . . . . . . . . . . . . . 12
   4.  Diameter QoS Authorization session establishment and
       management . . . . . . . . . . . . . . . . . . . . . . . . . . 15
     4.1.  Involved parties . . . . . . . . . . . . . . . . . . . . . 15
     4.2.  Initial QoS authorization (Diameter QoS authorization
           session establishment) . . . . . . . . . . . . . . . . . . 15
     4.3.  QoS authorization session re-authorization . . . . . . . . 18
       4.3.1.  Client-side initiated Re-Authorization . . . . . . . . 19
       4.3.2.  Server-side initiated Re-Authorization . . . . . . . . 20
     4.4.  Server-side initiated QoS parameter provisioning . . . . . 21
     4.5.  Session Termination  . . . . . . . . . . . . . . . . . . . 22
       4.5.1.  Client-side initiated session termination  . . . . . . 22
       4.5.2.  Server-side initiated session termination  . . . . . . 23
   5.  Accounting . . . . . . . . . . . . . . . . . . . . . . . . . . 25
   6.  Diameter QoS authorization application Messages  . . . . . . . 27
     6.1.  QoS-Authorization Request (QAR)  . . . . . . . . . . . . . 28
     6.2.  QoS-Authorization Answer (QAA) . . . . . . . . . . . . . . 28
     6.3.  QoS-Install Request (QIR)  . . . . . . . . . . . . . . . . 29
     6.4.  QoS-Install Answer (QAA) . . . . . . . . . . . . . . . . . 30
     6.5.  Accounting Request (ACR) . . . . . . . . . . . . . . . . . 30
     6.6.  Accounting Answer (ACA)  . . . . . . . . . . . . . . . . . 31
   7.  Diameter QoS Authorization Application AVPs  . . . . . . . . . 32
     7.1.  Diameter Base Protocol AVPs  . . . . . . . . . . . . . . . 32
     7.2.  Credit Control application AVPs  . . . . . . . . . . . . . 32
     7.3.  Accounting AVPs  . . . . . . . . . . . . . . . . . . . . . 33
     7.4.  Diameter QoS Application Defined AVPs  . . . . . . . . . . 33
   8.  Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
   9.  Security Considerations  . . . . . . . . . . . . . . . . . . . 40
   10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 41
   11. Open Issues  . . . . . . . . . . . . . . . . . . . . . . . . . 42
   12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 43
     12.1. Normative References . . . . . . . . . . . . . . . . . . . 43
     12.2. Informative References . . . . . . . . . . . . . . . . . . 43
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 45



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   Intellectual Property and Copyright Statements . . . . . . . . . . 46


















































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1.  Introduction

   To meet the Quality of Service needs of applications such as Voice-
   over-IP in a heavily loaded network, packets belonging to real-time
   application flows must be identified and segregated from other
   traffic to ensure that bandwidth, delay, and loss rate requirements
   are met.  In addition, new flows should not be added to the network
   when it is at or near capacity, which would result in degradation of
   quality for all flows carried by the network.

   In some cases, these goals can be achieved with mechanisms such as
   differentiated services and/or end-to-end congestion and admission
   control.  However, when bandwidth is scarce and must be carefully
   managed, such as in cellular networks, or when applications and
   transport protocols lack the capability to perform end-to-end
   congestion control, explicit reservation techniques are required.  In
   these cases, the endpoints will send reservation requests to edge
   and/or interior nodes along the communication path.  In addition to
   verifying whether resources are available, the recipient of a
   reservation request must also authenticate and authorize the request,
   especially in an environment where the endpoints are not trusted.  In
   addition, these nodes will generate accounting information about the
   resources used and attribute usage to the requesting endpoints.  This
   will enable the owner of the network element to generate usage-
   sensitive billing records and to understand how to allocate new
   network capacity.

   A variety of protocols could be used to make a QoS request, including
   RSVP [RFC2210], NSIS [I-D.ietf-nsis-qos-nslp], link-specific
   signaling or even SIP/SDP [RFC2327].  This document aims to be
   agnostic to the used QoS signaling protocol and to the signaled QoS
   model.



















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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].

   The following terms are used in this document:

   Application Server

      An application server is a network entity that exchanges signaling
      messages with an application endpoint.  It may be a source of
      authorization for QoS-enhanced application flows.  For example, a
      SIP server is one kind of application server.

   Application Endpoint

      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 will make a request for QoS from the
      network.  For example, a SIP User Agent is one kind of application
      endpoint.

   Authorizing Entity

      The authorizing entity is that entity responsible for authorizing
      QoS requests for a particular application flow or aggregate.  This
      may be a Diameter server (with a subscriber database) or an
      application server acting as a Diameter server.

   AAA Cloud

      A network of AAA proxy/broker arrangements.

   Network Element (NE)

      QoS aware router that acts as Diameter client that implements the
      Diameter QoS application in the context of this document.  For
      almost all scenarios this entity triggers the protocol interaction
      described in this document.  This entity corresponds to the Policy
      Enforcement Point (PEP) (see [RFC2753]) from a functionality point
      of view.








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3.  Framework

   The Diameter QoS application runs between a network element receiving
   QoS reservation requests (acting as a AAA client) and the resource
   authorizing entity (acting as a AAA server).  A high-level picture of
   the resulting architecture is shown in Figure 1.


               +-----------------+
               |   Authorizing   |
               |     Entity      |
               |(Diameter Server)|
               +-------+---------+
                       |
                       |
                /\-----+-----/\
            ////               \\\\
          ||       AAA Cloud       ||
         |   (Diameter application)  |
          ||                       ||
            \\\\               ////
                \-------+-----/
                        |
       +---+--+   +-----+----+   +---+--+
       |      |   |    NE    |   |      | Application
       +  NE  +===+(Diameter +===+  NE  +=============>>
       |      |   |  Client) |   |      |    Flow
       +------+   +----------+   +------+

   Figure 1: An Architecture supporting QoS-AAA

   Figure 1 depicts network elements through which application flows
   need to pass, a cloud of AAA servers, and an authorizing entity.
   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.  QoS aware network
   elements will request authorization from the AAA cloud based on an
   incoming QoS reservation request, which will route the request, for
   example, to the home network where the home authorizing entity will
   return the result of the authorization decision.

   In more complex deployment models, the authorization will be based on
   dynamic application state, so that the request must be authenticated
   and authorized based on information from one or more application
   servers.  If defined properly, the interface between the routers and
   AAA cloud would be identical in both cases.  Routers are therefore
   insulated from the details of particular applications and need not
   know that application servers are involved at all.  Also, the AAA



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   cloud would naturally encompass business relationships such as those
   between network operators and third-party application providers,
   enabling flexible intra- or inter-domain authorization, accounting,
   and settlement.

3.1.  Network element functional model

   Figure 2 depicts a logical operational model of resource management
   in a router.










































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          +-----------------------------------------------------+
          | DIAMETER Client                                     |
          | Functionality                                       |
          | +---------------++---------------++---------------+ |
          | | User          || Authorization || Accounting    | |
          | | Authentication|| of QoS        || for QoS       | |
          | +---------------+| Requests      || Traffic       | |
          |                  +---------------++---------------+ |
          +-----------------------------------------------------+
                 ^                            ^
                 v                            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

   Processing of incoming QoS reservation requests includes three
   actions: admission control, authorization and resource reservation.

   The admission control function provides information for available
   resources and determines whether there are enough resources to



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   fulfill the request.  Authorization is performed by the Diameter
   client function 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 requested QoS
   (depending on the authorization decision).  Once the requested
   resource is granted, the Resource Management function provides
   accounting information to the Authorizing entity using the Diameter
   client function.

3.2.  Authorization models

   Three fundamental models for authorizing QoS reservations exist: one
   two-party and two three party models.  See [I-D.tschofenig-nsis-aaa-
   issues] and in [I-D.tschofenig-nsis-qos-authz-issues] for a more
   detailed discussion of authorization models and the impact for QoS
   reservations.  From the Diameter QoS application's point of view
   these models differ in type of information that need to be carried.
   Here we focus on the 'Three party model' (Figure 3) and the Token
   based three party model' (Figure 4).  With the 'Two party model' the
   QoS resource requesting entity is authenticated by the Network
   Element and the authorization decision is made either locally at the
   Network Element itself or offloaded to a trusted entity (most likely
   within the same administrative domain).  In the former case no
   Diameter QoS protocol interaction is required.

























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                                        +--------------+
                                        | 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 Model

   With the 'Three party model' a QoS reservation request that hits the
   Network Element is forwarded to the Authorizing Entity (e.g., the
   user's home network), where the authorization decision is made.  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 consumed resources of 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 Model

   The 'Token based Three Party model' is applicable to environments
   where a previous protocol interaction is used to request
   authorization tokens to assist the authorization process at the
   Network Element or the Authorizing Entity.

   The QoS resource requesting entity may be involved in an application
   layer protocol interaction, for example using SIP, with the
   Authorizing Entity.  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
   Authorizing Entity (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 a
   Network Element 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 the authorization decision performed
   at the application layer protocol run 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



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   digest to prevent tampering).  In the latter case the authorization
   token may contain several pieces of information pertaining to the
   authorized application session, but at minimum it should contain:
   o  An identifier of the Authorizing Entity (for example, of an
      application server) 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 context of RSVP [RFC3520], with
   the OSP [ETSI-OSP] or as outlined in [I-D.ietf-sipping-trait-authz]
   and [I-D.tschofenig-sip-saml].

3.3.   QoS authorization considerations

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

      In particular, users may roam outside their home network, leading
      to a situation where the network element and authorizing entity
      are in different administrative domains.

   Identity-based Routing

      The QoS AAA protocol MUST route AAA requests to the Authorizing
      Entity.

   Flexible Authentication Support

      The QoS AAA protocol 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).






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   Making an Authorization Decision

      The QoS AAA protocol MUST exchange sufficient information between
      the authorizing entity and the enforcing entity (and vice versa)
      to compute an authorization decision and to execute this decision.

   Triggering an Authorization Process

      The QoS AAA protocol MUST allow periodic and event triggered
      execution of the authorization process, originated at the
      enforcing entity or even at the authorizing entity.

   Associating QoS Reservations and Application State

      The QoS AAA protocol MUST carry information sufficient for an
      application server to identify the appropriate application session
      and associate it with a particular QoS reservation.

   Dynamic Authorization

      It MUST be possible for the QoS AAA protocol to push updates
      towards the network element(s) from authorizing entities.

   Bearer Gating

      The QoS AAA protocol MUST allow the authorizing entity to gate
      (i.e., enable/disable) authorized application flows based on e.g.,
      application state transitions.

   Accounting Records

      The QoS AAA protocol MUST define QoS accounting records containing
      duration, volume (byte count) usage information and description of
      the QoS attributes (e.g., bandwidth, delay, loss rate) that were
      supported for the flow.

   Sending Accounting Records

      The network element MUST send accounting records for a particular
      application flow to the authorizing entity for that flow or to
      another entity identified by the authorizing entity.

   Failure Notification

      The QoS AAA protocol MUST allow the network element 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.




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   Accounting Correlation

      The QoS AAA protocol MUST support the exchange of sufficient
      information to allow for correlation between accounting records
      generated by the network elements and accounting records generated
      by an application server.

   Interaction with other AAA Applications
      Interaction with other AAA applications such as Diameter NASREQ
      [RFC4005] is 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 Authorizing Entity
   is contacted only with a request for QoS authorization.
   Authentication might have taken place already via the interaction
   with the Diameter NASREQ application or as part of the QoS signaling
   protocol (e.g., TLS handshake in GIST [I-D.ietf-nsis-ntlp]).

   Authentication of the QoS reservation requesting entity to the
   Authorizing Entity is necessary if a particular Diameter QoS
   application protocol run cannot be related (of if there is no
   intention to relate it) to a prior authentication.  In this case the
   Authorizing Entity MUST authenticate the QoS reservation requesting
   entity in order to authorize the QoS request as part of the Diameter
   QoS protocol interaction.























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4.  Diameter QoS Authorization session establishment and management

4.1.  Involved parties

   Authorization models supported by this application include three
   parties:
   o  Resource requesting entity
   o  Network Elements (Diameter QoS clients)
   o  Authorizing Entity (Diameter QoS server)
   Note that the QoS resource requesting entity 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., Diameter QoS client) and the
   Authorizing Entity (i.e., Diameter QoS server).

   The QoS resource requesting entity may communicate with the
   Authorizing Entity using application layer signaling for negotiation
   of service parameters.  As part of this application layer protocol
   interaction, for example using SIP, authentication and authorization
   might take place (see Figure 4).  This message exchange is, however,
   outside the scope of this document.  This protocol communication
   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 and a tight coupling with these
   protocols is not desired since this applications aims to be generic.

4.2.  Initial QoS authorization (Diameter QoS authorization session
      establishment)

   Figure 5 shows the protocol interaction between a resource requesting
   entity, a Network Element and the Authorizing Entity.

   A request for a QoS reservation received by a Network Element
   initiates a Diameter QoS authorization session.  The Network Element
   generates a QoS-Authorization-Request message (QAR) in which it maps
   required objects from the QoS signaling message to Diameter AVPs.
   Authorizing Entity's identity (Destination-Host AVP), pointer to the
   application session and/or identity and credentials of the QoS
   resource requesting entity (QoS-Authentication-Data, User-Name-ID
   AVPs), requested QoS parameters (QSPEC AVP), signaling session
   identifier and/or QoS enabled data flows identifiers (Signaling-
   Session-Id and Flows AVPs) MAY be encapsulated into respective
   Diameter AVPs and included into the Diameter message sent to the
   Authorizing Entity.  The QAR is sent to a Diameter server that can
   either be in the realm of the QoS requesting entity or also be an
   application server.




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   When the Diameter QoS server receives the QAR authorization
   processing starts.  Based on the information in the QoS-
   Authentication-Data, User-Name-ID and QoS-Authorized-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 authorization decision is then reflected in the
   response returned to the Diameter client with the QoS-Authorization-
   Answer message (QAA).









































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                                               Authorizing
     End-Host         Network Element             Entity
   requesting QoS      ( Diameter              ( Diameter
                        QoS Client)             QoS Server)
       |                   |                         |
       +---QoS-Reserve---->|                         |
       |                   +- - - - - QAR - - - - - >|
       |                   |(QoS-Resources,Cost,     |
       |                   |   QoS-Auth-Data,User-ID)|
       |                   |                +--------+--------------+
       |                   |                |  Authorize request    |
       |                   |                |  Keep session data    |
       |                   |                |/Authz-time,Session-Id/|
       |                   |                +--------+--------------+
       |                   |< - - - - QAA - - - - - -+
       |                   |(Result-Code,CC-Time,Cost|
       |                   |QoS-Resources,Authz-time)|
       |           +-------+---------+
       |           |Install QoS state|
       |           |       +         |
       |           | Authz. session  |
       |           | /Authz-time,    |
       |           |  CC-Time,Cost/  |
       |           +-------+---------+
       |                   +----------QoS-Reserve--------------->
       |                   |
       |                   |<---------QoS-Response---------------
       |<--QoS-Response----+
       |                   |
       |=====================Data Flow==========================>
       |                   |
       |                   +- - - - - ACR - - - - - >|
       |                   |(START,QoS-Resources,Cost|
       |                   |CC-Time,Acc-Multisess-id)|
       |                   |                +--------+--------------+
       |                   |                | Report for successful |
       |                   |                |   QoS reservation     |
       |                   |                |Update of reserved QoS |
       |                   |                |      resources        |
       |                   |                +--------+--------------+
       |                   |< - - - - ACA - - - - - -+
       |                   |                         |

   Figure 5: Initial QoS request authorization

   The Authorizing Entity keeps authorization session state and SHOULD
   save additional information for management of the session (e.g., Acc-
   Multi-Session-Id, Signaling-Session-Id, authentication data) as part



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   of the session state information.  A Signaling-session-Id (if
   present) SHOULD be used together with the generated Acc-Multi-
   Session-Id AVP for binding the authorization and the accounting
   session information in case of end host mobility (i.e., to correlate
   the Diameter sessions that are initiated for the same signaling
   session from different QoS NE).

   The final result of the authorization request is provided in the
   Result-Code AVP of the QAA message sent by the Authorizing Entity.
   In case of successful authorization (i.e., Result-Code =
   DIAMETER_LIMITED_SUCCESS), information about the authorized QoS
   resources and the status of the authorized flow (enabled/disabled) is
   provided in the QoS-Authorization-Resources AVP of the QAA message.
   The QoS information provided via the QAA is installed by the QoS
   Traffic Control function of the Network Element (see Figure 2).

   One important piece of information returned from the Authorizing
   Entity is the authorization lifetime (carried inside the QAA).  The
   authorization lifetime allows the Network Element 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 currently
   available credits at the user's account (see Section 5).  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 is discussed in Section 4.3,
   Section 4.5 and Section 5.

   The indication of a successful QoS reservation and activation of the
   data flow, is done by the transmission of an Accounting Request (ACR)
   message, which reports the parameters of the established QoS state:
   reserved resources, duration of the reservation, identification of
   the QoS enabled flow/QoS signaling session and accounting parameters.
   The Diameter QoS server acknowledges the reserved QoS resources with
   the Accounting Answer (ACA) message where the Result-Code is set to
   'DIAMETER_SUCCESS'.  Note that the reserved QoS resources reported in
   the ACR message MAY be less than those initially authorized with QAA
   message, due to the QoS signaling specific behavior (e.g., receiver-
   initiated reservations with One-Path-With-Advertisements) specific
   process of QoS negotiation along the data path.

4.3.  QoS authorization 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
   entity or result in specific actions in the QoS signaling protocol is



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   outside the scope of the Diameter QoS application.  It is directly
   dependent on the capabilities of the QoS signaling protocol.

4.3.1.  Client-side initiated Re-Authorization

   The Authorizing Entity provides the duration of the authorization
   session as part of the QoS-Authorization-Answer message (QAA).  At
   any time before expiration of this period, a new QoS-Authorization-
   Request message (QAR) MAY be sent to the Authorizing Entity.  The
   transmission of the QAR MAY be triggered when the Network Element
   receives a QoS signaling message with the semantic of modifying an
   ongoing authorized QoS session or when authorization lifetime expires
   or by an accounting event (see Section 5)(Figure 6)






































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                                               Authorizing
     End-Host         Network Element             Entity
   requesting QoS      ( Diameter              ( Diameter
                        QoS Client)             QoS Server)
       |                   |                         |
       |=====================Data Flow==========================>
       |                   |                         |
       |           +-------+----------+              |
       |           |Authz-time/CC-Time|              |
       |           |    expires       |              |
       |           +-------+----------+              |
       |                   +- - - - - QAR - - - - - >|
       |                   |(QoS-Resources,Cost,     |
       |                   |   QoS-Auth-Data,User-ID)|
                           |                +--------+--------------+
    NOTE:                  |                |  Authorize request    |
    Re-authorization       |                | Update session data   |
    is transparent to      |                |/Authz-time,Session-Id/|
    the End-Host           |                +--------+--------------+
                           |< - - - - QAA - - - - - -+
       |                   |(Result-Code,CC-Time,Cost|
       |                   |QoS-Resources,Authz-time)|
       |           +-------+---------+               |
       |           |Update QoS state |               |
       |           |       +         |               |
       |           | Authz. session  |               |
       |           | /Authz-time,    |               |
       |           |  CC-Time,Cost/  |               |
       |           +-------+---------+               |
       |                   |                         |
       |                   +- - - - - ACR - - - - - >|
       |                   |(INTRM,QoS-Resources,Cost|
       |                   |CC-Time,Acc-Multisess-id)|
       |                   |                +--------+--------------+
       |                   |                |  Update of used QoS   |
       |                   |                |resources/CC-Time,Cost/|
       |                   |                +--------+--------------+
       |                   |< - - - - ACA - - - - - -+
       |                   |                         |
       |=====================Data Flow==========================>
       |                   |

   Figure 6: QoS request re-authorization

4.3.2.  Server-side initiated Re-Authorization

   The Authorizing Entity MAY optionally initiate a QoS re-authorization
   by issuing a Re-Auth-Request message (RAR) as defined in the Diameter



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   base protocol [BASE].  A Network Element client that receives such a
   RAR message with Session-Id matching a currently active QoS session
   acknowledges the request by sending the Re-Auth-Answer (RAA) message
   and MUST initiate a QoS reservation re-authorization by sending a
   QoS-Authorization-Request (QAR) message towards the Authorizing
   entity.

4.4.  Server-side initiated QoS parameter provisioning

   The Authorizing Entity is enabled to update installed QoS parameters
   and flow state at the Network Element by sending a QoS-Install
   Request message (QIR).  Network Elements MUST apply the updates and
   respond with an QoS-Install Answer message (QIA).  This
   functionality, for example, allows to update already authorized flow
   status of an established QoS reservation due to a change at the
   application layer session (Figure 7).


                                               Authorizing
     End-Host         Network Element             Entity
   requesting QoS      ( Diameter              ( Diameter
                        QoS Client)             QoS Server)
       |                   |                         |
       +===================+=Data Flow==========================>
       |                   |                +--------+--------------+
       |                   |                |  Gate close event     |
       |                   |                +--------+--------------+
       |                   |< - - - - QIR - - - - - -+
       |                   |(QoS-Resources[QoS-Flow- |
       |                   | -State=CLOSE])          |
       |           +-------+---------+               |
       |           |Update QoS state |               |
       |           |       +         |               |
       |           | Authz. session  |               |
       |           |/QoS-Flow-State= |               |
       |           |     CLOSE/      |               |
       |           +-------+---------+               |
       +====Data Flow=====>X                         |
       |                   +- - - - - QAA - - - - - >|
       |                   |     (Result-Code)       |

   Figure 7: Server-side initiated QoS parameter provisioning

   The Authorizing Entity MAY initiate QoS authorization session
   establishment and QoS reservation state installation (prior to a
   request from a Network Element).  Such function requires that the
   Authorizing Entity has knowledge of specific information identifying
   the Network Element that should be contacted and the data flow for



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   which the QoS reservation should be established.

4.5.  Session Termination

4.5.1.  Client-side initiated session termination

   A QoS authorization session MAY be terminated by the Diameter client
   by sending a Session-Termination-Request message (STR) to the
   Diameter server.  This is a Base Diameter protocol functionality and
   it is defined in [RFC3588].  Session termination can be caused by a
   QoS signaling messaging requesting to delete an existing QoS
   reservation state or it can be caused as a result of a loss of bearer
   report.  After a successful termination of the authorization session,
   final accounting messages MUST be exchanged (Figure 8).





































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                                               Authorizing
     End-Host         Network Element             Entity
   requesting QoS      ( Diameter              ( Diameter
                        QoS Client)             QoS Server)
       |                   |                         |
       |==Data Flow==>X /Stop of the data flow/      |
       |                   |                         |
       +---QoS-Reserve---->|                         |
       |   (TearOn)        +- - - - - STR - - - - - >|
       |                   |                +--------+--------------+
       |<--QoS-Response----+                | Remove session state  |
       |                   |                +--------+--------------+
                           |< - - - - STA - - - - - -+
                   +-------+-----------+             |
                   |Tear down QoS state|
                   |   Report final    |
                   |  accounting data  |
                   +-------+-----------+
                           +----------QoS-Reserve--------------->
                           |           (TearOn)
                           |
                           +- - - - - ACR - - - - - >|
                           |(FINAL,QoS-Resources,Cost|
                           |CC-Time,Acc-Multisess-id)|
                           |                +--------+--------------+
                           |                | Report for successful |
                           |                |  end of QoS session   |
                           |                +--------+--------------+
                           |< - - - - ACA - - - - - -+
                           |
                           |
                           |<---------QoS-Response---------------
                           |

   Figure 8: Client-side initiated session termination

4.5.2.  Server-side initiated session termination

   At anytime during a session the Authorizing Entity MAY send an Abort-
   Session-Request message (ASR) to the Network Element.  This is a Base
   Diameter protocol functionality and it is defined in [RFC3588].
   Possible reasons for initiating the ASR message to the Network
   Element are insufficient credits or session termination at the
   application layer.  The ASR message results in termination of the
   authorized session, release of the reserved resources at the Network
   Element and transmission of an appropriate QoS signaling message
   indicating a notification to other Network Elements aware of the
   signaling session.  A final accounting message exchanges MUST be



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   triggered as a result of this ASR message exchange (Figure 9).


                                               Authorizing
     End-Host         Network Element             Entity
   requesting QoS      ( Diameter              ( Diameter
                        QoS Client)             QoS Server)
       |                   |                         |
       |=====================Data Flow==========================>
       |                   |
       |                   |< - - - - ASR - - - - - -+
       |                   |                         |
       |====Data Flow=====>X                         |
       |                   |                         |
       |<--QoS-Notify------+----------QoS-Reserve--------------->
       |                   |           (TearOn)      |
                   +-------+-----------+             |
                   |Tear down QoS state|             |
                   |   Report final    |             |
                   |  accounting data  |             |
                   +-------+-----------+             |
                           +- - - - - ASA - - - - - >|
                           |                +--------+--------------+
                           |                | Remove session state  |
                           |                +--------+--------------+
                           +- - - - - ACR - - - - - >|
                           |(FINAL,QoS-Resources,Cost|
                           |CC-Time,Acc-Multisess-id)|
                           |                +--------+--------------+
                           |                | Report for successful |
                           |                |  end of QoS session   |
                           |                +--------+--------------+
                           |< - - - - ACA - - - - - -+
                           |
                           |
                           |<---------QoS-Response---------------
                           |

   Figure 9: Server-side initiated session termination












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5.  Accounting

   The Diameter QoS application provides accounting for usage of
   reserved QoS resources.  Diameter QoS accounting has built-in support
   for online, duration based accounting.  This accounting is based on
   the notion that the routers making the QoS Authorization Request
   (Diameter QoS clients) are in the best position to determine the cost
   of those resources.  This cost represents the financial settlement
   that will be ultimately demanded by the router if the Resource
   Authorizing Entity authorizes the reservation.

   In the Diameter QoS application, the router MAY send a Cost-
   Information AVP ([RFC4006]) in the QAR.  If the Cost-Information AVP
   includes a Cost-Unit AVP ([RFC4006]) then the Cost-Unit SHOULD be
   "minute".  The Cost-Information AVPs represent the cost to allocate
   the resources requested in the QoS-Authorization-Resources AVP
   included in the same QAR message.  The QAR MAY optionally contain a
   Tariff-Time-Change AVP ([RFC4006]) which is the time at which the
   cost will change, a second Cost-Information AVP, which is the cost of
   the reserved resources after the tariff time change, and a second
   Tariff-Time-Change, which is the time at which the tariff would
   change again.  Either all three or none of these AVPs MUST be present
   in the QAR.

   The Resource Authorizing Entity returns a CC-Time AVP ([RFC4006]) in
   the QAA message which is the total authorized gate-on time for the
   service.  If the QAR included two Tariff-Time-Change AVPs, the
   current time plus the CC-Time AVP returned in the QAA MUST NOT exceed
   the second Tariff-Time-Change AVP from the QAR.  Based on information
   in the Cost-Information AVPs, the Resource Authorizing Entity can use
   the CC-Time AVP to guarantee that the total cost of the session will
   not exceed a certain threshold, which allows, for example, support of
   prepaid users.

   Each ACR message contains a triplet of QoS-Authorization-Resources
   AVP, Cost-Information AVP, and CC-Time AVP.  This represents the
   total time consumed at the given cost for the given resources.  Note
   that an ACR message MUST be sent separately for each interval defined
   by the Tariff-Time-Change AVPs and the expiration of the CC-Time
   returned in the QAA (Figure 6).

   The Network Element starts an accounting session by sending an
   Accounting-Request message (ACR) after successful QoS reservation and
   activation of the data flow (Figure 5).  After every successful re-
   authorization procedure the Network element MUST initiate an interim
   accounting message exchange (Figure 6).  After successful session
   termination the Network element MUST initiate a final exchange of
   accounting messages for terminating of the accounting session and



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   reporting final records for the usage of reserved QoS resources
   (Figure 8).

















































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6.  Diameter QoS authorization application Messages

   The Diameter QoS Application requires the definition of new mandatory
   AVPs and Command-codes [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.


   Command-Name                  Abbrev.        Code      Reference
   QoS-Authz-Request              QAR           [TBD]     Section 6.1
   QoS-Authz-Answer               QAA           [TBD]     Section 6.2
   QoS-Install-Request            QIR           [TBD]     Section 6.3
   QoS-Install-Answer             QIA           [TBD]     Section 6.4

   In addition, the following Diameter Base protocol messages are used
   in the Diameter QoS application:


   Command-Name                  Abbrev.        Code      Reference
   Accounting-Request             ACR            271       RFC 3588
   Accounting-Request             ACR            271       RFC 3588
   Accounting-Answer              ACA            271       RFC 3588
   Re-Auth-Request                RAR            258       RFC 3588
   Re-Auth-Answer                 RAA            258       RFC 3588
   Abort-Session-Request          ASR            274       RFC 3588
   Abort-Session-Answer           ACA            274       RFC 3588
   Session-Term-Request           STR            275       RFC 3588
   Session-Term-Answer            STA            275       RFC 3588

   Diameter nodes conforming to this specification MAY advertise support
   by including the value of TBD (TBD) in the Auth-Application-Id or the
   Acct-Application-Id AVP of the Capabilities-Exchange-Request and
   Capabilities-Exchange-Answer commands [RFC3588].

   The value of TBD (TBD) MUST be used as the Application-Id in all QAR/
   QAA and QIR/QIA commands.

   The value of TBD (TBD) MUST be used as the Application-Id in all ACR/
   ACA commands, because this application defines new, mandatory AVPs
   for accounting.

   The value of zero (0) SHOULD be used as the Application-Id in all
   STR/STA, ASR/ASA, and RAR/RAA commands, because these commands are
   defined in the Diameter base protocol and no additional mandatory
   AVPs for those commands are defined in this document.






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6.1.  QoS-Authorization Request (QAR)

   The QoS-Authorization-Request message (QAR) indicated by the Command-
   Code field set to TDB (TBD) and 'R' bit set in the Command Flags
   field is used by Network elements to request quality of service
   related resource authorization for a given flow.

   The QAR message MUST carry information for signaling session
   identification, Authorizing Entity 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-Request> ::= < Diameter Header: XXX, REQ, PXY >
                         < Session-Id >
                         { Auth-Application-Id }
                         { Origin-Host }
                         { Origin-Realm }
                         { Destination-Realm }
                         { Auth-Request-Type }
                         [ Destination-Host ]
                         [ User-Name ]
                      *  [ QoS-Authorization-Resources ]
                         [ QoS-Authentication-Data ]
                         [ Cost-Information ]
                         [ Acc-Multisession-Id ]
                         [ Bound-Auth-Session-Id ]
                      *  [ AVP ]

6.2.  QoS-Authorization Answer (QAA)

   The QoS-Authorization-Answer message (QAA), indicated by the Command-
   Code field set to TBD (TBD) and 'R' bit cleared in the Command Flags
   field is sent in response to the QoS-Authorization-Request message
   (QAR).  If the QoS authorization request is successfully authorized,
   the response will include the AVPs to allow authorization of the QoS
   resources as well as accounting and transport plane gating
   information.

   The message format is defined as follows:







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    <QoS-Answer> ::= < Diameter Header: XXX, PXY >
                     < Session-Id >
                     { Auth-Application-Id }
                     { Auth-Request-Type }
                     { Result-Code }
                     { Origin-Host }
                     { Origin-Realm }
                  *  [ QoS-Authorization-Resources ]
                     [ CC-Time ]
                     [ Acc-Multisession-Id ]
                     [ Session-Timeout ]
                     [ Authz-Session-Lifetime ]
                     [ Authz-Grace-Period ]
                  *  [ AVP ]

6.3.  QoS-Install Request (QIR)

   The QoS-Install Request message (QIR), indicated by the Command-Code
   field set to TDB (TBD) and 'R' bit set in the Command Flags field is
   used by Authorizing entity 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: XXX, REQ, PXY >
                              < Session-Id >
                              { Auth-Application-Id }
                              { Origin-Host }
                              { Origin-Realm }
                              { Destination-Realm }
                              { Auth-Request-Type }
                              [ Destination-Host ]
                           *  [ QoS-Authorization-Resources ]
                              [ Session-Timeout ]
                              [ Authz-Session-Lifetime ]
                              [ Authz-Grace-Period ]
                              [ Authz-Session-Volume ]
                           *  [ AVP ]





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6.4.  QoS-Install Answer (QAA)

   The QoS-Install Answer message (QAA), indicated by the Command-Code
   field set to TBD (TBD) and 'R' bit cleared in the Command Flags field
   is sent in response to the QoS-Install Request message (QIR) 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: XXX, PXY >
                              < Session-Id >
                              { Auth-Application-Id }
                              { Origin-Host }
                              { Origin-Realm }
                              { Result-Code }
                           *  [ QoS-Authorization-Resources ]
                           *  [ AVP ]

6.5.  Accounting Request (ACR)

   The Accounting Request message (ACR), indicated by the Command-Code
   field set to 271 and 'R' bit set in the Command Flags field is used
   by Network Element to report parameters of the authorized and
   established QoS reservation.

   The message MUST carry accounting information authorized QoS
   resources and its usage, e.g., QoS-Authorized-Resources, CC-Time, CC-
   Cost, Acc-Multi-Session-Id.

   The message format is defined as follows:


     <Accounting-Request> ::= < Diameter Header: XXX, REQ, PXY >
                              < Session-Id >
                              { Acct-Application-Id }
                              { Destination-Realm }
                              [ Destination-Host ]
                              [ Accounting-Record-Type ]
                              [ Accounting-Record-Number ]
                            * [ QoS-Authorization-Resources ]
                              [ Cost-Information ]
                              [ CC-Time ]
                              [ Acc-Multi-Session-Id ]
                            * [ AVP ]





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6.6.  Accounting Answer (ACA)

   The Accounting Answer message (ACA), indicated by the Command-Code
   field set to 271 and 'R' bit cleared in the Command Flags field is
   sent in response to the Accounting Request message (ACR) as an
   acknowledgment of the ACR message and MAY carry additional management
   information for the accounting session, e.g.  Acc-Interim-Interval
   AVP.

   The message format is defined as follows:


      <Accounting-Answer> ::= < Diameter Header: XXX, PXY >
                              < Session-Id >
                              { Acct-Application-Id }
                              [ Result-Code ]
                              [ Accounting-Record-Type ]
                              [ Accounting-Record-Number ]
                              [ Acc-Multi-Session-Id ]
                            * [ AVP ]































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7.   Diameter QoS Authorization 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.

7.1.  Diameter Base Protocol AVPs

   The Diameter 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
   Authz-Lifetime                291             Section 8.9
   Authz-Grace-Period            276             Section 8.10
   Session-Timeout                27             Section 8.13
   User-Name                       1             Section 8.14
   QoS-Filter-Rule               407             Section 6.9 [RFC4005]

   Some of the listed AVPs require definition and assignment of
   additional values which is described here:

   Auth-Application-Id AVP

      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 TBD (TBD).


7.2.  Credit Control application AVPs

   The Diameter QoS application provides accounting for usage of
   reserved QoS resources.  Diameter QoS accounting has built-in support
   for online, duration based accounting.  For this purpose it re-uses a
   number of AVPs defined in Diameter Credit Control application.
   [RFC4006].







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   Attribute Name                AVP Code     Reference [RFC4006]
   Cost-Information AVP          423             Section 8.7
   Unit-Value AVP                445             Section 8.8
   Currency-Code AVP             425             Section 8.11
   Cost-Unit AVP                 424             Section 8.12
   CC-Time AVP                   420             Section 8.21
   Tariff-Time-Change AVP        451             Section 6.20

   Usage of the listed AVPs is described in Section 5

7.3.  Accounting AVPs

   The Diameter QoS application uses Diameter Accounting and accounting
   AVPs as defined in Section 9 of [RFC3588].  Additional description of
   the usage of some of them in QoS authorization context is provided:


   Attribute Name                AVP Code     Reference [RFC3588]
   Acct-Application-Id           259             Section 6.9
   Accounting-Record-Type        480             Section 9.8.1
   Accounting-Interim-Interval    85             Section 9.8.2
   Accounting-Record-Number      485             Section 9.8.3
   Accounting-Realtime-Required  483             Section 9.8.7
   Acc-Multi-Session-ID           50             Section 9.8.5

   The following AVP needs further explanation:

   Acct-Application-Id AVP

      The Acct-Application-Id AVP (AVP Code 259)is assigned by IANA to
      Diameter applications.  The value of the Acct-Application-Id for
      the Diameter QoS application is TBD (TBD).

   Acc-Multisession-ID

      Acc-Multi-Session-ID AVP (AVP Code 50) SHOULD be used to link
      multiple accounting sessions together, allowing the correlation of
      accounting information.  This AVP MAY be returned by the Diameter
      server in a QoS-Authorization-Answer message (QAA), and MUST be
      used in all accounting messages for the given session.

7.4.  Diameter QoS Application Defined AVPs

   This section defines the Quality of Service AVPs that are specific to
   the Diameter QoS application and MAY be included in the Diameter QoS
   application messages.  Unlike the approach followed with RSVP (see
   [RFC2749]), where the entire RSVP message is encapsulated into a COPS
   message, only the relevant fields SHOULD be included.  This approach



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   avoids a certain overhead of transmitting fields which are irrelevant
   for the AAA infrastructure.  It keeps implementations simpler and it
   allows the reuse of other Diameter AVPs.

   The following table describes the Diameter AVPs in the QoS
   Application, their AVP code values, types, possible flag values, and
   whether the AVP MAY be encrypted.


                                             |    AVP Flag rules      |
                                             |----+---+----+-----|----+
                      AVP  Section           |    |   |SHLD| MUST|    |
    Attribute Name    Code Defined Data Type |MUST|MAY| NOT|  NOT|Encr|
   ------------------------------------------+----+---+----+-----+----+
   Signaling-Session  TBD    7.4  Unsigned32 | M  | P |    |  V  | Y  |
     -Id                                     |    |   |    |     |    |
   Flow-ID            TBD    7.4  Unsigned32 | M  | P |    |  V  | Y  |
   SPI                TBD    7.4  Unsigned32 | M  | P |    |  V  | Y  |
   QoS-Flow-State     TBD    7.4  Enumerated | M  | P |    |  V  | Y  |
   IND-Flow           TBD    7.4  Grouped    | M  | P |    |  V  | Y  |
   Flows              TBD    7.4  Grouped    | M  | P |    |  V  | Y  |
   QSPEC              TBD    7.4  OctetString| M  | P |    |  V  | Y  |
   QoS-Auth           TBD    7.4  Grouped    | M  | P |    |  V  | Y  |
     -Resources                              |    |   |    |     |    |
   QoS-Auth-Data      TBD    7.4  Grouped    | M  | P |    |  V  | Y  |
   Bound-Auth                                |    |   |    |     |    |
     -Session-Id      TBD    7.4  UTF8String | M  | P |    |  V  | Y  |
   ------------------------------------------+----+---+----+-----+----+

   Signaling-Session-ID

      Signaling-Session-ID AVP (AVP Code TBD) is of type Unsigned32 and
      contains a copy of the QoS signaling session identifier, which is
      a unique identifier of the QoS signaling session that in NSIS case
      remains unchanged for the duration of the session.

   Flow-ID

      The Flow-ID AVP (AVP Code TBD) is of type Unsigned32 and contains
      identifier of an IP flow.

   SPI

      The SPI AVP (AVP Code TBD) is of type Unsigned32 and extends the
      QoS-Filter-Rule AVP to support IPsec protected traffic.






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   QoS-Flow-State

      The QoS-Flow-State AVP (AVP Code TBD) is of type Enumerated.  It
      gives an indication by the Authorizing entity how the flow MUST be
      treated.  When included in a QAA message, it is instructions to
      the QoS network element with regard to the state to which the flow
      should be set.  The supported values are:


   0  Open     - Enable the transport plane service, for which
                 the signaling is done
   1  Close    - Disable the transport plane service
   2  Maintain - Current state (enabled/disabled) of the transport
                 plane service is maintained


      The QoS-Flow-State is an optional AVP.  When not included in a QAA
      response, the default behaviour is to immediately allow the flow
      of packets (Open).


   IND-Flows

      The IND-Flows AVP (AVP Code TBD) is of type Grouped and specifies
      IP Flows via their flow identifiers and filter-rule.


   IND-Flows ::= <AVP Header>
                 [Flow-Id]
                 [QoS-Filter-Rule]
           [0-1] [SPI]
           [0-1] [QoS-Flow-State]

   Flows

      The Flows AVP (AVP Code TBD) is of type Grouped and contains all
      the individual flows that receive the same QoS specified in the
      included QSPEC.


   Flows    ::= < AVP Header: XXX >
          [1+]* [ IND-Flows ]

   QSPEC

      The QSPEC AVP (AVP Code TBD) is of type OctetString and contains
      QoS parameter information.  Description format is taken from QoS
      NSLP Qspec template, which is expected to cover all present QoS



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      description methods [I-D.ietf-nsis-qspec].


   QoS-Authorization-Resources

      The QoS-Auth-Resources AVP (AVP Code TBD) is of type Grouped and
      includes description of the resources that have been requested by
      the user or authorized by the application server for a particular
      QoS request.  More than one MAY be included into a message.


   QoS-Auth-Resources ::= < AVP Header: XXX >
                   [0-1]  [ Signaling-Session-ID ]
                   [0-1]* [ Flows ]
                     [1]  [ QSPEC ]
                   [0-1]  [ QoS-Flow-State ]


      Included QoS-Flow-State AVP SHOULD be overwritten by any included
      QoS-Flow-State AVPs specified for the individual flows.


   QoS-Authentication-Data

      The QoS-Authentication-Data AVP (AVP Code TBD) is of type
      OctetString.  It is a container that carries application session
      or user specific data that allows to the Authorizing entity in
      computation of the authorization decision.


   Bound-Authentication-Session-Id

      The Bound-Authentication-Session AVP (AVP Code TBD) is of type
      UTF8String.  It carries the id of the Diameter authentication
      session that is used for the network access authentication (NASREQ
      authentication session).  It is used to tie the QoS authorization
      request to a priory authentication of the end host done by a
      collocated NASREQ application at the QoS NE.













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8.  Examples

   This section presents an example of the interaction between the
   application layer signaling and the QoS signaling along the data
   path.  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                                 SIP Server  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-Auth-Data,        ++------------+ |
         |      >===========>QoS-Authz-Resources,  |Authorize    | |
         |                  |Cost-Info)            |QoS resources| |
         |                  |                      ++------------+ |
         |                  | QAA                   |              |
         |                  <- - - - -<<AAA>>- - - -+              |
         |                  |(Result-Code,          |              |
         |                  |QoS-Authz-Resources,   |              |
         |                  |CC-Time,               |              |
         |                  |Authz-Lifetime)        |              |



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         |        +---------+--------+              |              |
         |        |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 26: Example for a token-based QoS authorization

   The communication starts with SIP signaling between the two end
   points and the SIP server for negotiation and authorization of the
   requested service and its parameters (Figure 26).  As a part of the
   process, the SIP server verifies whether the user at Host A is
   authorized to use the requested service (and potentially the ability



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   to get 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
   authorizing entity (e.g., the SIP server) 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 Authorizing Entity (in our 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-Authentication AVP and the description of
   the QoS resources is included into QoS-Authorized-Resources AVP.  In
   addition, the NE rates the requested QoS resources and announces the
   charging rate into the Cost-Information AVP.  These AVPs are included
   into a QoS Authorization Request message, which is sent to the
   Authorizing entity.

   A Diameter QAR message will be routed through the AAA network to the
   Authorizing Entity.  The Authorizing Entity verifies the requested
   QoS against the QoS resources negotiated for the service session and
   replies with QoS-Authorization answer (QAA) message.  It carries the
   authorization result (Result-Code AVP) and the description of the
   authorized QoS parameters (QoS-Authorized-Resources AVP), as well as
   duration of the authorization session (Authorization-Lifetime AVP)
   and duration of the time (CC-Time) for which the end-user should be
   charged with the rate announced in the QAR message.  The NE interacts
   with the traffic control function and installs the authorized QoS
   resources and forwards the QoS NSLP Reserve message further along the
   data path.

   If the data communication might be necessary in both directions, from
   Host A to Host B and vice versa, a separate QoS signaling
   communication is required for the reverse direction (with path-
   coupled signaling).  This message exchange is not shown in this
   example.









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9.  Security Considerations

   This document describes a mechanism for performing authorization of a
   QoS reservation at a third party entity.  Therefore, it is necessary
   the QoS signaling application to carry sufficient information that
   should be forwarded to the backend AAA server.  This functionality is
   particularly useful in roaming environments where the authorization
   decision is most likely provided at an entity where the user can be
   authorized, such as in the home realm.

   QoS signaling application MAY re-use the authenticated identities
   used for the establishment of the secured transport channel for the
   signaling messages, e.g., TLS or IPsec between the end host and the
   policy aware QoS NE.  In addition, a collocation of the QoS NE with,
   for example, the Diameter NASREQ application ([RFC4005]) may allow
   the QoS authorization to be based on the authenticated identity used
   during the network access authentication protocol run.  If a co-
   located deployment is not desired then special security protection is
   required to ensure that arbitrary nodes cannot reuse a previous
   authentication exchange to perform an authorization decision.

   Additionally, QoS authorization might be based on the usage of
   authorization tokens that are generated by the Authorizing Entity and
   provided to the end host via application layer signaling.

   The impact of the existence of different authorization models is
   (with respect to this Diameter QoS application) the ability to carry
   different authentication and authorization information.  Further
   discussions on the authorization handling for QoS signaling protocols
   is available with [I-D.tschofenig-nsis-aaa-issues] and
   [I-D.tschofenig-nsis-qos-authz-issues].




















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10.  Acknowledgements

   The authors would like to thank John Loughney and Allison Mankin for
   their input to this document.















































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11.  Open Issues

   Open issues related to this draft are listed at the issue tracker
   available at: http://www.tschofenig.com:8080/diameter-qos/















































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12.  References

12.1.  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.

12.2.  Informative References

   [ETSI-OSP]
              European Telecommunications Standards Institute,
              "Telecommunications and Internet Protocol Harmonization
              Over  Networks (TIPHON); Open Settlement Protocol (OSP)
              for Inter-domain  pricing, authorization, and usage
              exchange", TS 101 321.

   [I-D.ietf-nsis-ntlp]
              Schulzrinne, H. and R. Hancock, "GIMPS: General Internet
              Messaging Protocol for Signaling", draft-ietf-nsis-ntlp-07
              (work in progress), July 2005.

   [I-D.ietf-nsis-qos-nslp]
              Bosch, S., "NSLP for Quality-of-Service signalling",
              draft-ietf-nsis-qos-nslp-07 (work in progress), July 2005.

   [I-D.ietf-nsis-qspec]
              Ash, J., "QoS-NSLP QSPEC Template",
              draft-ietf-nsis-qspec-05 (work in progress), July 2005.

   [I-D.ietf-sipping-trait-authz]
              Peterson, J., "Trait-based Authorization Requirements for
              the Session Initiation Protocol  (SIP)",
              draft-ietf-sipping-trait-authz-01 (work in progress),
              February 2005.

   [I-D.tschofenig-nsis-aaa-issues]
              Tschofenig, H., "NSIS Authentication, Authorization and
              Accounting Issues", draft-tschofenig-nsis-aaa-issues-01
              (work in progress), March 2003.

   [I-D.tschofenig-nsis-qos-authz-issues]
              Tschofenig, H., "QoS NSLP Authorization Issues",
              draft-tschofenig-nsis-qos-authz-issues-00 (work in
              progress), June 2003.




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   [I-D.tschofenig-sip-saml]
              Tschofenig, H., "Using SAML for SIP",
              draft-tschofenig-sip-saml-04 (work in progress),
              July 2005.

   [RFC2210]  Wroclawski, J., "The Use of RSVP with IETF Integrated
              Services", RFC 2210, September 1997.

   [RFC2327]  Handley, M. and V. Jacobson, "SDP: Session Description
              Protocol", RFC 2327, April 1998.

   [RFC2749]  Herzog, S., Boyle, J., Cohen, R., Durham, D., Rajan, R.,
              and A. Sastry, "COPS usage for RSVP", RFC 2749,
              January 2000.

   [RFC2753]  Yavatkar, R., Pendarakis, D., and R. Guerin, "A Framework
              for Policy-based Admission Control", RFC 2753,
              January 2000.

   [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.

   [RFC4005]  Calhoun, P., Zorn, G., Spence, D., and D. Mitton,
              "Diameter Network Access Server Application", RFC 4005,
              August 2005.

   [RFC4006]  Hakala, H., Mattila, L., Koskinen, J-P., Stura, M., and J.
              Loughney, "Diameter Credit-Control Application", RFC 4006,
              August 2005.

   [RFC4027]  Josefsson, S., "Domain Name System Media Types", RFC 4027,
              April 2005.










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Authors' Addresses

   Frank M. Alfano
   Lucent Technologies
   1960 Lucent Lane
   Naperville, IL  60563
   USA

   Phone: +1 630 979 7209
   Email: falfano@lucent.com


   Peter J. McCann
   Lucent Technologies
   1960 Lucent Lane
   Naperville, IL  60563
   USA

   Phone: +1 630 713 9359
   Email: mccap@lucent.com


   Hannes Tschofenig
   Siemens
   Otto-Hahn-Ring 6
   Munich, Bavaria  81739
   Germany

   Email: Hannes.Tschofenig@siemens.com
   URI:   http://www.tschofenig.com


   Tseno Tsenov
   Siemens
   Otto-Hahn-Ring 6
   Munich, Bavaria  81739
   Germany

   Email: tseno.tsenov@mytum.de












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