Network Working Group G. Zorn, Ed.
Internet-Draft Cisco Systems
Intended status: Standards Track P. McCann
Expires: January 10, 2008 Motorola Labs
H. Tschofenig
Nokia Siemens Networks
T. Tsou
Huawei
A. Doria
Lulea University of Technology
D. Sun
Bell Labs/Alcatel-Lucent
July 9, 2007
Diameter Quality of Service Application
draft-ietf-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 . . . . . . . . . . . . . . . . . . . . . . . . . 5
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6
3. Framework . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.1. Network element functional model . . . . . . . . . . . . . 9
3.2. Implications of endpoint QoS capabilities . . . . . . . . 11
3.2.1. Category of endpoint QoS capabilities . . . . . . . . 11
3.2.2. Interaction modes between authorizing entity and
network element . . . . . . . . . . . . . . . . . . . 11
3.3. Authorization schemes . . . . . . . . . . . . . . . . . . 13
3.3.1. Authorization schemes for pull mode . . . . . . . . . 13
3.3.2. Authorization schemes for push mode . . . . . . . . . 16
3.4. QoS Authorization Requirements . . . . . . . . . . . . . . 17
4. Diameter QoS Authorization Session Establishment and
Management . . . . . . . . . . . . . . . . . . . . . . . . . . 22
4.1. Parties involved . . . . . . . . . . . . . . . . . . . . . 22
4.2. Diameter QoS Authorization Session Establishment . . . . . 22
4.3. QoS authorization session re-authorization . . . . . . . . 26
4.3.1. Client-Side Initiated Re-Authorization . . . . . . . . 26
4.3.2. Server-Side Initiated Re-Authorization . . . . . . . . 28
4.4. Server-Side Initiated QoS Parameter Provisioning . . . . . 28
4.5. Session Termination . . . . . . . . . . . . . . . . . . . 29
4.5.1. Client-Side Initiated Session Termination . . . . . . 29
4.5.2. Server-Side Initiated Session Termination . . . . . . 30
5. Accounting . . . . . . . . . . . . . . . . . . . . . . . . . . 32
6. Diameter QoS Authorization Application Messages . . . . . . . 33
6.1. QoS-Authorization Request (QAR) . . . . . . . . . . . . . 34
6.2. QoS-Authorization Answer (QAA) . . . . . . . . . . . . . . 34
6.3. QoS-Install Request (QIR) . . . . . . . . . . . . . . . . 35
6.4. QoS-Install Answer (QIA) . . . . . . . . . . . . . . . . . 36
6.5. Accounting Request (ACR) . . . . . . . . . . . . . . . . . 36
6.6. Accounting Answer (ACA) . . . . . . . . . . . . . . . . . 37
7. Diameter QoS Authorization Application AVPs . . . . . . . . . 38
7.1. Diameter Base Protocol AVPs . . . . . . . . . . . . . . . 38
7.2. Credit Control Application AVPs . . . . . . . . . . . . . 38
7.3. Accounting AVPs . . . . . . . . . . . . . . . . . . . . . 39
7.4. Diameter QoS Application Defined AVPs . . . . . . . . . . 39
8. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 44
10. Security Considerations . . . . . . . . . . . . . . . . . . . 45
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 46
12. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 47
13. Open Issues . . . . . . . . . . . . . . . . . . . . . . . . . 48
14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 49
14.1. Normative References . . . . . . . . . . . . . . . . . . . 49
14.2. Informative References . . . . . . . . . . . . . . . . . . 49
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 51
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Intellectual Property and Copyright Statements . . . . . . . . . . 53
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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 [RFC4566]. 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 may 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 acts as a Diameter server (and may
collocate with a subscriber database) responsible for authorizing
QoS requests for a particular application flow or aggregate. It
may be a standalone entity or integrated with an application
server. This entity corresponds to the Policy Decision Point
(PDP) (see [RFC2753]).
AAA Cloud
An infrastructure of AAA entities (clients, agents, 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] are 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
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Enforcement Point (PEP) (see [RFC2753]).
Pull Mode
In this mode, the QoS authorization process is invoked by the QoS
reservation request received from the endpoint. The Network
Element then requests the QoS authorization decision from the
Authorizing entity.
Push Mode
In this mode, the QoS authorization process is invoked by the
request from Application Server or local policies in the
Authorizing Entity. The Authorizing Entity then installs the QoS
authorization decision to the Network Element initiatively.
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3. Framework
The Diameter QoS application runs between a network element (acting
as a Diameter client) and the resource authorizing entity (acting as
a Diameter server). A high-level picture of the resulting
architecture is shown in Figure 1.
+-------+---------+
| Authorizing |
| Entity |
|(Diameter Server)|
+-------+---------+
|
|
/\-----+-----/\
//// \\\\
|| AAA Cloud ||
| (Diameter application) |
|| ||
\\\\ ////
\-------+-----/
|
+---+--+ +-----+----+ +---+--+
| | | NE | | | Media
+ NE +===+(Diameter +===+ NE +=============>>
| | | Client) | | | Flow
+------+ +----------+ +------+
Figure 1: An Architecture supporting QoS-AAA
Figure 1 depicts network elements through which media 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.
In some deployment scenarios, QoS aware network elements may request
authorization through the AAA cloud based on an incoming QoS
reservation request. The network element will route the request to a
designated authorizing entity. The authorizing entity will return
the result of the authorization decision. In other deployment
scenarios, the authorization will be initiated upon dynamic
application state, so that the request must be authenticated and
authorized based on information from one or more application servers.
If defined properly, the interface between the routers and AAA cloud
would be identical in both cases. Routers are therefore insulated
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from the details of particular applications and need not 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. Implications of endpoint QoS capabilities
3.2.1. Category of endpoint QoS capabilities
The QoS capabilities of endpoints are varied, which can be
categorized as follows:
o Category 1 endpoint: Has no QoS capability at both application and
network levels. This type of endpoint may set up a connection
through application signaling, but it is unable to specify any
resource/QoS requirements either through application signaling
e.g. SIP or through network signaling e.g. RSVP or NSIS (or does
not support network signaling at all).
o Category 2 endpoint: Only has QoS capability at the application
level. This type of endpoint is able to set up a connection
through application signaling with certain resource/QoS
requirements (e.g. application attributes), but it is unable to
specify any network level resource/QoS requirements (e.g., network
QoS class) through network signaling e.g., RSVP or NSIS (or does
not support network layer signaling at all).
o Category 3: endpoint: Has QoS capability at the network level.
This type of endpoint may set up a connection through application
signaling and translate service characteristics into network
resource/QoS requirements (e.g. network QoS class) locally, and
request the resources through network signaling e.g. RSVP or
NSIS.
3.2.2. Interaction modes between authorizing entity and network element
Different QoS mechanisms are employed in packet networks. Those QoS
mechanisms can be categorized into two schemes: IntServ and DiffServ.
In the IntServ scheme, network signaling e.g RSVP, NSIS, or link
specific signaling is commonly used to initiate a request from
endpoint for desired QoS resource of media flow. In the DiffServ
scheme, the QoS resources are provisioned based on some predefined
QoS service classes instead of endpoint initiated per flow based QoS
request.
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It is obvious that the eligible QoS scheme is correlated to the
endpoint's capability in the context of QoS authorization. Since
category 1 and 2 endpoints cannot initiate the QoS resource requests
through the network signaling, the IntServ model is not applicable to
them in general. Depending on network technology and operator's
demand, a category 3 endpoint may either make use of the network
signaling for requesting the resource or not perform the request.
The diversity of QoS capabilities of endpoints and QoS schemes of
network technology leads to the distinction on the interaction mode
between QoS authorization system and underlying network elements.
When the IntServ scheme is employed by category 3 endpoint, the
authorization process is typically initiated by network element when
a trigger such as the network signaling is received from the
endpoint. In the DiffServ scheme, since the network element is
unable to request the resource authorization on its own initiative,
the authorization process is typically triggered upon either the
request of application servers or policies defined by the operator.
As a consequence, two interaction modes are needed in support of
different combinations of QoS schemes and endpoint's QoS
capabilities. Push mode and Pull mode.
o Push mode: The QoS authorization process is triggered by
application servers or local network conditions (e.g. time of day
on resource usage and QoS classes), and the authorization
decisions are installed by the authorzing entity to the network
element on its own initiative without explicit request. In order
to support the push mode, the authorizing entity (i.e. Diameter
server) should be able to initiate a Diameter authorization
session to communicate with the network element (i.e. Diameter
client) without any pre-established connection from the network
element.
o Pull mode: The QoS authorization process is triggered by the
network signaling received from end user equipments or by the
local event in the network element according to pre-configured
policies, and authorization decisions are produced upon the
request of the network element. In order to support the pull
mode, the network element (i.e. Diameter client) will initiate a
Diameter authorization session to communicate with authorizing
entity (i.e. Diameter server).
For category 1 and 2 endpoints, the Push mode is required, in
particular, category 1 endpoint requires network initiated push mode
and category 2 endpoint may use both them. For category 3 endpoint,
either push mode or pull mode is doable.
The Push mode is applicable to certain networks, for example, Cable
network, DSL, Ethernet, Diffserv enabled IP/MPLS as defined by other
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SDOs e.g. ETSI TISPAN and ITU-T. The Pull mode is more appropriate
to IntServ enabled IP networks or certain wireless networks such as
GPRS networks as defined by 3GPP/PP2. Some networks e.g. WiMAX may
require both Push and Pull modes.
3.3. Authorization schemes
3.3.1. Authorization schemes for pull mode
Three basic authorization schemes for pull mode exist: one two-party
and two three-party schemes. 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
schemes differ in type of information that need to be carried. Here
we focus on the 'Three party scheme' (Figure 3) and the Token-based
three party scheme' (Figure 4). With the 'Two party scheme' 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 Scheme
With the 'Three party scheme' 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 Scheme
The 'Token-based Three Party scheme' is applicable to environments
where a previous protocol interaction is used to request
authorization tokens to assist the authorization process at the
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].
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.
3.3.2. Authorization schemes for push mode
The push mode can be further divided into two types: endpoint
initiated and network initiated. In the former case, the
authorization process is triggered by application server upon
explicit QoS request from endpoints through application signaling,
e.g. SIP; in the latter case, the authorization process is triggered
by application server without explicit QoS request from endpoint.
In the endpoint initiated scheme, the QoS resource requesting entity
(i.e. endpoint) determines the required application level QoS and
sends the QoS request through application signaling message, the
Application Server will extract application level QoS information and
trigger the authorization process to Authorizing entity. In the
network initiated scheme, the Authorizing entity and/or Application
sever should derive and determine the QoS requirement according to
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application attribute, subscription and endpoint's capability when
the endpoint does not explicitly indicate the QoS attributes. The
authorizing entity makes authorization decision based on application
level QoS information, network policies, end user subscription and
network resource availability etc., and installs the decision to
network element directly.
financial settlement
...........................+
Application V ------- .
signaling msg +--------------+ / QoS AAA \ .
+-------------->| | / protocol \ .
| | Authorizing +--------------+ \ .
| | Entity | | | | .
| + |<--+----+ | | .
| +--------------+ |QoS | |QoS |.
| install| |install
| |rsp. | |req. |.
| | | | |.
| | | | . | .
| \ | | . / .
| \ | | / .
V |-----V . .
+-------------+ +--------+-----+ .
| Entity | | NE | .
| requesting | | performing | .
| resource |QoS rsrc granted | QoS | <....+
| |<-----------------| reservation |
+-------------+ +--------------+
Figure 5: Authorization Scheme for Push Mode
3.4. QoS Authorization Requirements
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
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:
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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 the
General Internet Signaling Transport (GIST) protocol, see
[I-D.ietf-nsis-ntlp]).
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Authentication of the QoS reservation requesting entity to the
Authorizing Entity is necessary if a particular Diameter QoS
application protocol run cannot be related (or 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) is referred to
as a Diameter authorization session. It is identified by a
Session-Id included in all Diameter messages used for management
of the authorized service (initial authorization, re-
authorization, termination), see [RFC3588].
Application layer session
The application layer session identifies the duration of an
application layer service 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.
Correlating these sessions is done at each of the three involved
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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
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. 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. 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.
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+----------------------------------+-------------------------------+
| QoS specific Input Data | Diameter QoS AVPs |
+----------------------------------+-------------------------------+
| Authorizing entity ID (e.g., | Destination-Host |
| taken from authorization token | Destination-Realm |
| or from Network Access ID (NAI) | |
| [RFC2486] of the QoS requesting | |
| entity) | |
+----------------------------------+-------------------------------+
| Authorization Token | QoS-Authz-Data |
| Credentials of | User-Name |
| the QoS requesting entity | |
+----------------------------------+-------------------------------+
| QoS parameters | QoS-Resources |
+----------------------------------+-------------------------------+
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. Based on the information in the QoS-
Authentication-Data, User-Name and QoS-Resources AVPs the server
determines the authorized QoS resources and flow state (enabled/
disabled) from locally available information (e.g., policy
information that may be previously established as part of an
application layer signaling exchange, or the user's subscription
profile). The 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-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 the QAA message, due to the QoS signaling
specific behavior (e.g., receiver-initiated reservations with One-
Path-With-Advertisements) or specific process of QoS negotiation
along the data path.
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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 a 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
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lifetime expires or by an accounting event, see Section 5 and
Figure 8).
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-Authz-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 (see 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
(see 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 (see 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 Diameter QoS clients are in the best position to
determine the cost of those resources.
In the Diameter QoS application, the router MAY send a Cost-
Information AVP (see [RFC4006]) in the QAR. If the Cost-Information
AVP includes a Cost-Unit AVP (see [RFC4006]) then the Cost-Unit
SHOULD be "minute". The Cost-Information AVPs represent the cost to
allocate the resources requested in the QoS-Resources AVP included in
the same QAR message. The QAR MAY optionally contain a Tariff-Time-
Change AVP (see [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 (see [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-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 (see 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 (see Figure 7). After every successful
re-authorization procedure the Network element MUST initiate an
interim accounting message exchange (see Figure 8). After successful
session termination the Network element MUST initiate a final
exchange of accounting messages for terminating of the accounting
session and reporting final records for the usage of the QoS
resources reserved (see 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 (see Section 3 of [RFC3588]). Four new
Diameter messages are defined along with Command-Codes whose values
MUST be supported by all Diameter implementations that conform to
this specification.
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, see [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 (see 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-Resources ]
[ QoS-Authz-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-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-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-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-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-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
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
Usage of the listed AVPs is described in Section 5
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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 AVPs need further explanation:
Acct-Application-Id AVP
The Acct-Application-Id AVP (AVP Code 259)is assigned by IANA to
Diameter applications. The value of the Acct-Application-Id for
the Diameter QoS application is TBD (TBD).
Acc-Multisession-ID
Acc-Multi-Session-ID AVP (AVP Code 50) SHOULD be used to link
multiple accounting sessions together, allowing the correlation of
accounting information. This AVP MAY be returned by the Diameter
server in a QoS-Authorization-Answer message (QAA), and MUST be
used in all accounting messages for the given session.
7.4. Diameter QoS Application Defined AVPs
This document reuses the AVPs defined in Section 4 of
[I-D.ietf-dime-qos-attributes].
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This section lists the AVPs that are used by this specifispecific to
the Diameter QoS application.
Additionally, the followig new AVPs are defined:
Bound-Auth-Session-Id and the QoS-Authz-Data AVP
The following table describes the Diameter AVPs newly defined in this
document for usage with 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|
+----------------------------------------------+----+---+----+-----+
|QoS-Authz-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. |
+------------------------------------------------------------------+
QoS-Authz-Data
The QoS-Authz-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 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-Authz-Data ++------------+ |
| >===========>QoS-Resources, |Authorize | |
| |Cost-Info) |QoS resources| |
| | ++------------+ |
| | QAA | |
| <- - - - -<<AAA>>- - - -+ |
| |(Result-Code, | |
| |QoS-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 24: Token-based QoS Authorization Example
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 (see Figure 24). 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-Authz-Data AVP and the description of the
QoS resources is included into QoS-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-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. IANA Considerations
TBD
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10. Security Considerations
This document describes a mechanism for performing authorization of a
QoS reservation at a third party entity. Therefore, it is necessary
that 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 (see [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.
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11. 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. Rajith R provided some inputs to the
document early 2007
[Editor's Note: Acknowledgements need to be updated.]
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12. Contributors
The authors would like to thank Tseno Tsenov (tseno.tsenov@gmail.com)
and Frank Alfano (falfano@lucent.com) for starting the Diameter
Quality of Service work within the IETF, for your significant draft
contributions and for being the driving force for the first few draft
versions.
[Editor's Note: A bit of history needs to be included here.]
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13. 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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14. References
14.1. Normative References
[I-D.ietf-dime-qos-attributes]
Korhonen, J., "Quality of Service Attributes for Diameter
and RADIUS", draft-ietf-dime-qos-attributes-00 (work in
progress), July 2007.
[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.
14.2. Informative References
[I-D.ietf-nsis-ntlp]
Schulzrinne, H. and R. Hancock, "GIST: General Internet
Signalling Transport", draft-ietf-nsis-ntlp-13 (work in
progress), April 2007.
[I-D.ietf-nsis-qos-nslp]
Manner, J., "NSLP for Quality-of-Service Signaling",
draft-ietf-nsis-qos-nslp-14 (work in progress), June 2007.
[RFC2210] Wroclawski, J., "The Use of RSVP with IETF Integrated
Services", RFC 2210, September 1997.
[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
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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.
[RFC4027] Josefsson, S., "Domain Name System Media Types", RFC 4027,
April 2005.
[RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
Description Protocol", RFC 4566, July 2006.
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Authors' Addresses
Glen Zorn (editor)
Cisco Systems
2901 Third Avenue, Suite 600
SEA1/5/
Seattle, WA 98121
USA
Phone: +1 (425) 344 8113
Email: gwz@cisco.com
Peter J. McCann
Motorola Labs
1301 E. Algonquin Rd
Schaumburg, IL 60196
USA
Phone: +1 847 576 3440
Email: pete.mccann@motorola.com
Hannes Tschofenig
Nokia Siemens Networks
Otto-Hahn-Ring 6
Munich, Bavaria 81739
Germany
Email: Hannes.Tschofenig@nsn.com
URI: http://www.tschofenig.com
Tina Tsou
Huawei
Shenzhen,
P.R.C
Email: tena@huawei.com
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Avri Doria
Lulea University of Technology
Arbetsvetenskap
Lulea, SE-97187
Sweden
Email: avri@ltu.se
Dong Sun
Bell Labs/Alcatel-Lucent
101 Crawfords Corner Rd
Holmdel, NJ 07733
USA
Email: dongsun@alcatel-lucent.com
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Full Copyright Statement
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