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
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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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[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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