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Versions: 00 01 draft-ietf-dime-diameter-qos

Diameter Maintanence and                                       F. Alfano
Extensions (DIME)                                              P. McCann
Internet-Draft                                       Lucent Technologies
Intended status: Informational                             H. Tschofenig
Expires: April 23, 2007                                          Siemens
                                                               T. Tsenov
                                                                 T. Tsou
                                                        October 20, 2006


                Diameter Quality of Service Application
               draft-tschofenig-dime-diameter-qos-01.txt

Status of this Memo

   By submitting this Internet-Draft, each author represents that any
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   This Internet-Draft will expire on April 23, 2007.

Copyright Notice

   Copyright (C) The Internet Society (2006).










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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
   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.







































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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 . . . . . . . . . . . . . 13
   4.  Diameter QoS Authorization session establishment and
       management . . . . . . . . . . . . . . . . . . . . . . . . . . 18
     4.1.  Parties involved . . . . . . . . . . . . . . . . . . . . . 18
     4.2.  Initial QoS authorization (Diameter QoS authorization
           session establishment) . . . . . . . . . . . . . . . . . . 18
     4.3.  QoS authorization session re-authorization . . . . . . . . 22
       4.3.1.  Client-side initiated Re-Authorization . . . . . . . . 22
       4.3.2.  Server-side initiated Re-Authorization . . . . . . . . 24
     4.4.  Server-side initiated QoS parameter provisioning . . . . . 24
     4.5.  Session Termination  . . . . . . . . . . . . . . . . . . . 25
       4.5.1.  Client-side initiated session termination  . . . . . . 25
       4.5.2.  Server-side initiated session termination  . . . . . . 26
   5.  Accounting . . . . . . . . . . . . . . . . . . . . . . . . . . 28
   6.  Diameter QoS authorization application Messages  . . . . . . . 30
     6.1.  QoS-Authorization Request (QAR)  . . . . . . . . . . . . . 31
     6.2.  QoS-Authorization Answer (QAA) . . . . . . . . . . . . . . 31
     6.3.  QoS-Install Request (QIR)  . . . . . . . . . . . . . . . . 32
     6.4.  QoS-Install Answer (QIA) . . . . . . . . . . . . . . . . . 33
     6.5.  Accounting Request (ACR) . . . . . . . . . . . . . . . . . 33
     6.6.  Accounting Answer (ACA)  . . . . . . . . . . . . . . . . . 34
   7.  Diameter QoS Authorization Application AVPs  . . . . . . . . . 35
     7.1.  Diameter Base Protocol AVPs  . . . . . . . . . . . . . . . 35
     7.2.  Credit Control application AVPs  . . . . . . . . . . . . . 35
     7.3.  Accounting AVPs  . . . . . . . . . . . . . . . . . . . . . 36
     7.4.  Diameter QoS Application Defined AVPs  . . . . . . . . . . 37
   8.  Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
   9.  Security Considerations  . . . . . . . . . . . . . . . . . . . 44
   10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 45
   11. Open Issues  . . . . . . . . . . . . . . . . . . . . . . . . . 46
   12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 47
     12.1. Normative References . . . . . . . . . . . . . . . . . . . 47
     12.2. Informative References . . . . . . . . . . . . . . . . . . 47
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 50
   Intellectual Property and Copyright Statements . . . . . . . . . . 51









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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 QoS signaling protocol used and to the QoS model to
   which the signaling is directed.



















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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

      An infrastructure of AAA entities (clients, proxies, servers)
      based on a AAA protocol, which provides trusted secure connections
      between them.  It offers authentication, authorization and
      accounting services to applications in flexible local and roaming
      scenarios.  Diameter [RFC3588] and RADIUS [RFC2865] and both
      widely deployed AAA protocols.

   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.  The AAA entities will route the
   request to a designated AAA authorizing entity, for example in the
   home domain.  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



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   know that application servers are involved at all.  Also, the AAA
   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
            +--------------+            +----------+
            |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.  The
   notation adopted here is in respect to the entity that performs the
   QoS authorization.  The authentication of the QoS requesting entity
   might be done at the network element as part of the QoS signaling
   protocol, or by an off-path protocol run (on the application layer or
   for network access authentication) or the authorizing entity might be
   contacted with request for authentication and authorization of the
   QoS requesting entity.  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 arrives
   at the Network Element is forwarded to the Authorizing Entity (e.g.,
   in 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 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 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].

   In the scenario mentioned above, where the QoS resource requesting
   entity is involved in an application layer protocol interaction with
   the Authorizing entity, 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 resource
   requesting entity where it might receive media streams, for example
   in SIP/SDP signalling these port numbers are advertised.  The QoS
   resource requesting entity 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 Authorizing entity in
   the QoS authz. request.  The Authorizing entity will use the QoS
   resource requesting entity'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 authz. response.

   A Three party model based on "push" - where the Authorizing entity,
   subsequent to a successful application layer authorization, will send
   the policy information unsolicited to the NE performing QoS
   reservation is shown below.













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                               financial settlement
                                ...........................+
      Application Layer         V             -------      .
      Protocol        +--------------+      / 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: Three Party Push Model

   In the three party QoS model where the QoS resource requesting entity
   is involved in an application layer protocol interaction with the
   Authorizing entity, the Authorizing entity may be considered as two
   separate functional entities - an Application function (AF)and a
   Policy Decision function (PDF).  The AF and PDF interact using the
   QoS AAA protocol.  The AF will pass dynamic QoS-related application
   information with the PDF.  The PDF will choose the right piece of
   policy information to be applied at the Policy Enforcement Point
   (PEP) in the NE performing QoS reservation.

   The policy information may be pushed to the PEP or may be requested/
   pulled by the NE performing QoS reservation.  The first message of
   the QoS AAA session between the AF and the PDF may include an
   indication on whether to use the push or the pull mode.

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 while interworking with QoS signaling
   protocols, a Diameter QoS application should accommodate the



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   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, based on the provided identity of the QoS requesting
      entity or the identity of the Authorizing entity encoded in the
      provided authorization token.

   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).

   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.




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   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 SHOULD send accounting records for a
      particular QoS reservation state to the authorizing entity, which
      plays the role of an accounting 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.

   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 Network
      Access (NASREQ) application [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., Transport Layer Security (TLS) handshake in General
   Internet Signaling Transport (GIST) [I-D.ietf-nsis-ntlp]).

   Authentication of the QoS reservation requesting entity to the



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   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.

   The 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 as 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 end points).  The details can be found in Section 7.4.

   Diameter authorization session

      The time period, for which a Diameter server authorizes a
      requested service (i.e., QoS resource reservation).  It is
      identified by a Session-Id included in all Diameter messages used
      for management of the authorized service (initial authorization,
      re-authorization, termination)[RFC3588].

   Application layer session

      The application layer session identifies the duration of an
      application layer service which requires provision of 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 network elements.
      It is included in the authorization request message sent to the
      Authorizing entity and helps it to correlate the QoS authorization
      request to the application session state information. (see
      Figure 4).

   Correlation of 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 network element correlates the
   QoS signaling session with the Diameter authorization sessions.  The



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   Authorizing entity 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 QoS signaling protocol directly if there is no binding
   between the application session and the QoS requesting entity using
   the QoS signaling protocol.













































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4.  Diameter QoS Authorization session establishment and management

4.1.  Parties involved

   Authorization models supported by this application include three
   parties:
   o  Resource requesting entity
   o  Network Elements (Diameter QoS 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.  The protocol communication
   between the the QoS resource requesting entity and the QoS Network
   Element 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 desirable since this applications aims to be
   generic.

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

   Figure 7 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 (QAR) message in which it maps
   required objects from the QoS signaling message to Diameter payload
   objects - Attribute Value Pairs (AVPs, [RFC3588]).











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   +----------------------------------+-------------------------------+
   | QoS authorization data           | Diameter QoS AVPs (Section 7) |
   +----------------------------------+-------------------------------+
   | Authorizing entity ID (e.g.,     | Destination-Host              |
   |taken from authorization token or | Destination-Realm             |
   |from Network Access ID(NAI),      |                               |
   |[RFC2486] of the QoS requesting   |                               |
   |entity)                           |                               |
   +----------------------------------+-------------------------------+
   | Application session Id (authori- | QoS-Authorization-Data        |
   | zation token) / credentials of   | User-Name                     |
   | the QoS requesting entity        |                               |
   +----------------------------------+-------------------------------+
   | QoS parameters                   | QSPEC                         |
   +----------------------------------+-------------------------------+
   | Signaling session Id / Flow(s) Id| Signaling-session             |
   |                                  | Flows                         |
   +----------------------------------+-------------------------------+

   The Authorizing Entity's identity, information about the application
   session and/or identity and credentials of the QoS resource
   requesting entity, requested QoS parameters, signaling session
   identifier and/or QoS enabled data flows identifiers 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 the home server of the QoS
   requesting entity or an application server.

   Authorization processing starts at the Diameter QoS server when it
   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,    |                QoS Responder
       |           |  CC-Time,Cost/  |                    Node
       |           +-------+---------+                      |
       |                   +----------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 7: 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 (see Section 7.3) 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, (see Section 7.1)), 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).  The value DIAMETER_LIMITED_SUCCESS indicates that
   the Authorizing entity expects confirmation via an accounting message
   for successful QoS resource reservation and for final reserved QoS
   resources (see bellow).

   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 provided 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 different 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.





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

   In addition, there are number of options for policy rules according
   to which the NE (AAA client) contacts the Authorizing Entity for re-
   authorization.  These rules depend on the semantics and contents of
   the QAA message sent by the Authorizing Entity:
   a.  The QAA message contains the authorized parameters of the flow
       and its QoS and sets their limits (presumably upper).  With these
       parameters the Authorizing Entity specifies the services that the
       NE can provide and will be financially compensated for.
       Therefore, any change or request for change of the parameters of
       the flow and its QoS that do not conform to the authorized limits
       requires contacting the Authorizing Entity for authorization.
   b.  The QAA message contains authorized parameters of the flow and
       its QoS.  The rules that determine whether parameters' changes
       require re-authorization are agreed out of band, based on a
       Service Level Agreement (SLA) between the domains of the NE and
       the Authorizing Entity.
   c.  The QAA message contains the authorized parameters of the flow
       and its QoS.  Any change or request for change of these
       parameters requires contacting the Authorizing entity for re-
       authorization.
   d.  In addition to the authorized parameters of the flow and its QoS,
       the QAA message contains policy rules that determine the NEs
       actions in case of change or request for change in authorized
       parameters.

   Provided options are not exhaustive.  Elaborating on any of the
   listed approaches is deployment /solution specific and is not
   considered in the current document.

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 that requires modification of the
   authorized parameters of an ongoing QoS session, when authorization
   lifetime expires or by an accounting event. (see Section 5)(Figure 8)



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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 QoS resources|
       |                   |                |/CC-Time,Cost/ used    |
       |                   |                +--------+--------------+
       |                   |< - - - - ACA - - - - - -+
       |                   |                         |
       |=====================Data Flow==========================>
       |                   |

                  Figure 8: QoS request re-authorization








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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
   base protocol [RFC3588].  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

   In certain deployment scenarios (mostly applicable for local QoS
   provision) an active control over the QoS resource and QoS enabled
   data flows from the network side is required.  Therefore, 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 the update of already authorized flow status of an
   established QoS reservation due to a change at the application layer
   session (Figure 9).


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




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        Figure 9: Server-side initiated QoS parameter provisioning

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

4.5.  Session Termination

4.5.1.  Client-side initiated session termination

   The authorization session for an installed QoS reservation state MAY
   be terminated by the Diameter client by sending a Session-
   Termination-Request message (STR) to the Diameter server.  This is a
   Diameter base protocol function and it is defined in [RFC3588].
   Session termination can be caused by a QoS signaling messaging
   requesting deletion of the existing QoS reservation state or it can
   be caused as a result of a soft-state expiration of the QoS
   reservation state.  After a successful termination of the
   authorization session, final accounting messages MUST be exchanged
   (Figure 10).  It should be noted that the two sessions (authorization
   and accounting) have independent management by the Diameter base
   protocol, which allows for finalizing the accounting session after
   the end of the authorization session.
























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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---->|                         |
       |  (Delete QoS      +- - - - - STR - - - - - >|
       |   reservation)    |                +--------+--------------+
       |                   |                | Remove authorization  |
       |<--QoS-Response----+                | session state         |
       |                   |                +--------+--------------+
                           |< - - - - STA - - - - - -+
                   +-------+--------+                |
                   |Delete QoS state|
                   |  Report final  |
                   | accounting data|                   QoS Responder
                   +-------+--------+                       Node
                           +----------QoS-Reserve-----....--->|
                           |         (Delete QoS              |
                           |          reservation)
                           |
                           +- - - - - ACR - - - - - >|
                           |(FINAL,QoS-Resources,Cost|
                           |CC-Time,Acc-Multisess-id)|
                           |                +--------+--------------+
                           |                | Report for successful |
                           |                |  end of QoS session   |
                           |                +--------+--------------+
                           |< - - - - ACA - - - - - -+
                           |
                           |                            QoS Responder
                           |                                Node
                           |<---------QoS-Response----....----+
                           |                                  |

           Figure 10: 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
   Diameter base protocol function 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



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   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 exchange MUST be
   triggered as a result of this ASR message exchange (Figure 11).


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

           Figure 11: 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 owner of 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 8).

   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 7).  After every successful re-
   authorization procedure the Network element MUST initiate an interim
   accounting message exchange (Figure 8).  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 the QoS resources reserved.
   (Figure 10).

















































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6.  Diameter QoS authorization application Messages

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


   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           ASA            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 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 MUST be used as the Application-Id in all QAR/QAA
   and QIR/QIA commands.

   The value of 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 (Section 3 of [RFC3588]) set to 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, presented in ABNF form [RFC2234], 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 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 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 (QIA)

   The QoS-Install Answer message (QIA), indicated by the Command-Code
   field set to 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]

   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.

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].


   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




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   Usage of the listed AVPs is described in Section 5

   Diameter QoS application is designed to independently provide credit
   control over the controlled QoS resources.  However, deployment
   scenarios, where Diameter QoS application is collocated with Diameter
   Credit Control application, are not excluded.  In such scenarios the
   credit control over the QoS resources might be managed by the Credit
   control application.  Possible interworking approach might be a usage
   of Credit-Control AVP (AVP Code 426) with a newly defined value.  It
   will indicate to the Diameter QoS entities that the credit control
   over the QoS resources would be handled in separate session by Credit
   Control application.  An active cooperation of both applications
   would be required but it is not elaborated further in this document.

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 the 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.






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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
   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|
   +----------------------------------------------+----+---+----+-----+
   |Signaling-Session-Id   TBD    7.4  Unsigned32 | M  | P |    |  V  |
   |Flow-ID                TBD    7.4  Unsigned32 | M  | P |    |  V  |
   |SPI                    TBD    7.4  Unsigned32 | M  | P |    |  V  |
   |QoS-Flow-State         TBD    7.4  Enumerated | M  | P |    |  V  |
   |IND-Flow               TBD    7.4  Grouped    | M  | P |    |  V  |
   |Flows                  TBD    7.4  Grouped    | M  | P |    |  V  |
   |QSPEC                  TBD    7.4  OctetString| M  | P |    |  V  |
   |QoS-Auth-Resources     TBD    7.4  Grouped    | M  | P |    |  V  |
   |QoS-Auth-Data          TBD    7.4  Grouped    | M  | P |    |  V  |
   |Bound-Auth-Session-Id  TBD    7.4  UTF8String | M  | P |    |  V  |
   +----------------------------------------------+----+---+----+-----+
   |M - Mandatory bit. An AVP with "M" bit set and its value MUST be  |
   |    supported and recognized by a Diameter entity in order the    |
   |    message, which carries this AVP, to be accepted.              |
   |P - Indicates the need for encryption for end-to-end security.    |
   |V - Vendor specific bit that indicates whether the AVP belongs to |
   |    a address space.                                              |
   +------------------------------------------------------------------+

   Signaling-Session-ID

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





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   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.

   QoS-Flow-State

      The QoS-Flow-State AVP (AVP Code TBD) is of type Enumerated.  It
      gives an indication by the Authorizing entity as to how the flow
      MUST be treated.  When included in a QAA message, it contains an
      action to be performed on the state of the flow to which the
      message applies.  The values supported are:


   0  Open     - Enable the transport plane service, for which
                 the signaling has been performed.
   1  Close    - Disable the transport plane service
   2  Maintain - Do not alter the current state (enabled/disabled)
                 of the transport plane service.

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

      The behavior of Close (0) for the QoS-Flow-State refers to the
      case where a QoS reservation exists but it is not activated and
      therefore not charged.  For time-based charging the time interval
      where the gate is closed will not be included of the chargeable
      time interval.  The QoS model might give some indication whether
      an established QoS reservation needs to be freed or needs to be
      removed only if not enough resources are available.


   IND-Flows

      The IND-Flows AVP (AVP Code TBD) is of type Grouped and specifies
      an IP flow via its flow identifier and/or filter-rule.  Note that
      more than one IP flow may be described if only QoS-Filter-Rule is
      used.







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

   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
      QPSEC AVP included in the QoS-Authorization-Resources AVP.


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

   QSPEC

      The QSPEC AVP (AVP Code TBD) is of type OctetString and contains
      QoS parameter information.  The description format is taken from
      QoS NSLP Qspec template, which is expected to cover all present
      QoS 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 >
                          [ Signaling-Session-ID ]
                          [ Flows ]
                          [ QSPEC ]
                          [ QoS-Flow-State ]

      The three types of identifiers for the QoS signaling session (i.e,
      Signaling-Session-ID, Flow-ID and OoSFilter-Rule with SPI) SHOULD
      be used separately when included in the QoS-Authorization-Request
      (QAR) messages.


   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 has to be supplied to the Authorizing



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      entity as input to the 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 prior authentication of the end host done by a co-
      located application for network access authentication (Diameter
      NASREQ) 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 28: 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 28).  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 be charged for the service usage).  Negotiated session parameters
   are provided to the end host.

   Subsequently, Host A initiates a QoS signaling message towards Host
   B. It sends a QoS NSLP Reserve message, in which it includes
   description of the required QoS (QSPEC object) and authorization data
   for negotiated service session (part of the POLICY_DATA object).
   Authorization data includes, as a minimum, the identity of the
   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 this case the SIP server
   that is co-located with a Diameter server) is put into the
   Destination-Host AVP, any additional session authorization data is
   encapsulated into the QoS-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.

   Note that the example above shows a sender-initiated reservation from
   the End-Host towards the corresponding node and a receiver-initiated
   reservation from the correspondent node towards the End-Host.











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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.  In September 2005 Robert Hancock,
   Jukka Manner, Cornelia Kappler, Xiaoming Fu, Georgios Karagiannis and
   Elwyn Davies provided a detailed review.  Robert also provided us
   with good feedback earlier in 2005.  Jerry Ash provided us review
   comments late 2005/early 2006.











































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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

   [I-D.ietf-nsis-qspec]
              Ash, J., "QoS NSLP QSPEC Template",
              draft-ietf-nsis-qspec-12 (work in progress), October 2006.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2234]  Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", RFC 2234, November 1997.

   [RFC3588]  Calhoun, P., Loughney, J., Guttman, E., Zorn, G., and J.
              Arkko, "Diameter Base Protocol", RFC 3588, September 2003.

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

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

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, "GIST: General Internet
              Signaling Transport", draft-ietf-nsis-ntlp-11 (work in
              progress), August 2006.

   [I-D.ietf-nsis-qos-nslp]
              Manner, J., "NSLP for Quality-of-Service Signaling",
              draft-ietf-nsis-qos-nslp-11 (work in progress), June 2006.

   [I-D.ietf-sipping-trait-authz]
              Peterson, J., "Trait-based Authorization Requirements for
              the Session Initiation Protocol  (SIP)",
              draft-ietf-sipping-trait-authz-02 (work in progress),
              January 2006.



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Internet-Draft          Diameter QoS Application            October 2006


   [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.

   [I-D.tschofenig-sip-saml]
              Tschofenig, H., "SIP SAML Profile and Binding",
              draft-tschofenig-sip-saml-05 (work in progress),
              March 2006.

   [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.

   [RFC2486]  Aboba, B. and M. Beadles, "The Network Access Identifier",
              RFC 2486, January 1999.

   [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.

   [RFC2865]  Rigney, C., Willens, S., Rubens, A., and W. Simpson,
              "Remote Authentication Dial In User Service (RADIUS)",
              RFC 2865, June 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.




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   [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
   Sofia,
   Bulgaria

   Email: tseno.tsenov@mytum.de


   Tina Tsou
   Shenzhen,
   P.R.C

   Email: tena@huawei.com







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Full Copyright Statement

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