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INTERNET-DRAFT AAA Framework for Multicasting March 2007
MBONED WG Hiroaki Satou, NTT
Internet-Draft Hiroshi Ohta, NTT
Proposed Status: Informational Christian Jacquenet, France Telecom
Expires: September 2, 2007 Tsunemasa Hayashi, NTT
Haixiang He, Nortel Networks
March 4, 2007
AAA Framework for Multicasting
<draft-ietf-mboned-multiaaa-framework-03.txt>
Status of this Memo
By submitting this Internet-Draft, each author represents that any
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This Internet-Draft will expire on September 2, 2007.
Copyright Notice
Copyright (C) The IETF Trust (2007).
Satou, Ohta, Jacquenet, Hayashi, He [Page 1]
INTERNET-DRAFT AAA Framework for Multicasting March 2007
Abstract
IP multicast-based services, such as TV broadcasting or
videoconferencing raise the issue of making sure that potential
customers are fully entitled to access the corresponding
contents. There is indeed a need for service and content
providers to identify (if not authenticate, especially within the
context of enforcing electronic payment schemes) and to invoice
such customers in a reliable and efficient manner. This memo
describes the framework for specifying the Authorization,
Authentication and Accounting (AAA) capabilities that could be
activated within the context of the deployment and the operation
of IP multicast-based services. This framework addresses the
requirements presented in draft-ietf-mboned-maccnt-req-04.txt,
"Requirements for Accounting, Authentication and Authorization in
Well Managed IP Multicasting Services".
Satou, Ohta, Jacquenet, Hayashi, He [Page 2]
1. Introduction
1.1 Purpose and Background
IP multicasting is designed to serve cases of group communication
schemes of any kind, such as 1-to-n (case of TV broadcasting
services for example) or n-to-p (case of videoconferencing services,
for example).
In these environments, IP multicast provides a better resource
optimization than using a unicast transmission scheme, where data
need to be replicated as many times as there are receivers.
Activation of IP multicast capabilities in networks yields the
establishment and the maintenance of multicast distribution trees
that are receiver-initiated by nature: multicast-formatted data are
forwarded to receivers who explicitly request them.
IP multicast-based services, such as TV broadcasting or
videoconferencing raise the issue of making sure that potential
customers are fully entitled to access the corresponding contents.
There is indeed a need for service and content providers to identify
(if not authenticate, especially within the context of enforcing
electronic payment schemes) and to invoice such customers in a
reliable and efficient manner. This memo describes the framework for
specifying the Authorization, Authentication and Accounting (AAA)
capabilities that could be activated within the context of the
deployment and the operation of IP multicast-based services.
Specifically, this framework addresses the requirements
presented in draft-ietf-mboned-maccnt-req-04.txt, "Requirements for
Accounting, Authentication and Authorization in Well Managed IP
Multicasting Services" MACCNT-REQ-draft describes the requirements
in CDN services using IP multicast[1]. The requirements are derived
from:
- need for user tracking and billing capabilities
- need for network access control to satisfy the requirements
of the Network Service Provider (NSP) and/or content access control
to satisfy the requirements of the Content Provider (CP)
- methods for sharing information between the network service
provider and content provider to make it possible to fulfill the
above two requirements.
Detailed requirements are presented in MACCNT-REQ-draft. These
requirements include mechanisms for recording end-user requests and
provider responses for content-delivery, sharing user information
(possibly anonymously depending on the trust model) between content
provider and network service provider, and protecting resources
through the prevention of network and content access by unauthorized
users, as well as other AAA related requirements.
The purpose of this memo is to provide a generalized framework for
specifying multicast-inferred AAA capabilities that can meet these
requirements. This framework is to provide a basis for future work
of investigating the applicability of existing AAA protocols to
Hayashi, He, Satou, Ohta [Page 3]
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provide these AAA capabilities in IP multicast specific context
and/or if deemed necessary, the refining or defining of protocols to
provide these capabilities.
This draft's scope is limited to discussing SSM, 1-to-n IP
multicasting exclusively.
2. Definitions and Abbreviations
2.1 Definitions
For the purpose of this memo the following definitions apply:
Accounting: The set of capabilities that allow the retrieval of a
set of statistical data that can be defined on a per customer and/or
a per service basis, within the context of the deployment of
multicast-based services. Such data are retrieved for billing
purposes, and can be retrieved on a regular basis or upon
unsolicited requests. Such data include (but are not necessarily
limited to) the volume of multicast-formatted data that have been
forwarded to the receiver over a given period of time, the volume of
multicast-formatted data that have been exchanged between a receiver
(or set of) and a given source over a given period of time (e.g. the
duration of a multicast session), etc.
Authentication: action for identifying a user as a genuine one.
Authorization: The set of capabilities that need to be activated to
make sure a given requesting customer is (1) what he claims to be
(identification purposes), and (2) is fully entitled to access a set
of services (authentication purposes).
Receiver: an end-host or end-client which receives content. A
receiver may be identified by a network ID such as MAC address or IP
address.
User: a human with a user account. A user may possibly use multiple
reception devices. Multiple users may use the same reception
device.
Note: The definition of a receiver (device) and a user (human)
should not be confused.
2.2 Abbreviations
For the purpose of this draft the following abbreviations apply:
ACL: Access Control List
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CDN: Content Delivery Network
CDS: Content Delivery Services
CP: Content Provider
NSP: Network Service Provider
TP: Transit Provider
Satou, Ohta, Jacquenet, Hayashi, He [Page 5]
3. Common use models and network architecture implications
In some cases a single entity may design and be responsible for a
system that covers the various common high-level requirements of a
multicasting system such as 1) content serving, 2) the
infrastructure to multicast it, 3) network and content access
control mechanisms. In many cases however the content provision and
network provision roles are divided between separate entities. The
MACCNT-REQ-draft provides more detail of the multiple versus single
entity CDS network models.
As such it should not be assumed that the entity responsible for the
multicasting structure and the entity responsible for content
serving are the same. Indeed because the infrastructure for
multicasting is expensive and many content holders are not likely to
be competent at building and maintaining complicated infrastructures
necessary for multicasting, many content holders would prefer to
purchase transport and management services from a network service
provider and thus share the infrastructure costs with other content
holders.
Similarly network service providers in many cases do not specialize
in providing content and are unlikely to build and maintain such a
resource-intensive system without a certain level of demand from
content holders.
The use model of a single NSP providing multicasting services to
multiple CPs the following general requirements from MACCNT-REQ-
draft apply:
-Need for user tracking and billing capabilities
-Need for network access control and/or content access control
satisfactory to the requirements of the CP
-Methods for sharing information between the NSP and CP to make
the above two possible
When the NSP and CP are the same single entity the general
requirements are as follows.
-Need for user tracking and user-billing capabilities
-Need for access control and/or content protection at level the
entity deems appropriate
4. Framework and Roles of Entities
4.1 Framework for multicast AAA
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A general high-level framework can be represented as follows.
+------------------------------+
| user |
| |
+------------------------------+
| Access ^ Response
| Request | & Multicast Data
V |
+------------------------------+
| NSP |
| |
+------------------------------+
| Access ^ Response
| Request | (Success)
v |
+------------------------------+
| CP |
| |
+------------------------------+
For the sake of simplicity, the above diagram portrays a case where
there is a single NSP entity and a single CP entity, but multiple
CPs can be connected to the same NSP. It is also possible for the
same CP to be connected to multiple NSP networks (e.g. network
selection). In other words the relationship of NSP:CP can be
described as 1:1, 1:N or M:N. Furthermore it is possible that the
NSP and CP could be the same entity.
Description of Roles:
The user (or the user's device) selects a CP and a NSP when the user
requests content. The NSP may be automatically selected by a user
terminal: e.g. a fixed line NSP for STB or a mobile NSP for mobile
phone. In some usage cases it is possible that the NSP used by the
user terminal will not always be the same. For example a user may
have contracted with different NSPs for fixed line or mobile roaming
access.
The CP is responsible for Authentication and Authorization of users'
access to content that the CP manages. The CP hopes to collect
accounting information related to the access of their content. The
CP may choose to authenticate and authorize NSPs which are eligible
to provide users access to its contents. When the CP cannot (e.g.
error or resource issues) or decides not (e.g. policy issues) to
deliver content, the CP is responsible for notifying the NSP of the
reason. It is up to the NSP how to relay or translate the messages
to the user.
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The NSP is responsible for managing its network resources. The NSP
may perform admission control. It is also responsible for relaying
the AAA messages from the CP whether the user is eligible to receive
content (authentication by proxy), and the NSPs relevant AAA server
will make the final decision of whether the connection can be
established. When the NSP cannot or decides not to multicast to
users, the NSP is responsible for notifying the users of the reason.
4.2 Multiple User IDs
Users may hold multiple user IDs: IDs which have been separately
assigned for each subscription they may have for various NSPs and
CPs. The NSPs and CPs control the user IDs for their respective
domains. The user IDs are only meaningful in the context of each
domain.
When the user wants to access content, the user registers the
corresponding user ID (including its CP domain information) with a
request for content, etc: web authentication is one possible method.
Each CP may identify users by the user IDs that it has issued to
them.
Terminal portability can be realized if the NSP authenticates a user
using a NSP-domained user ID. This allows the user to access the
content from various network access points.
The NSP and CP do not need to know the corresponding user id for the
same user in the other provider's domain, and it is not necessary
that there is a one to one relationship. It is quite possible for
one person to hold multiple user ids for the same provider.
The actual mapping rules for NSPs and CPs to map user IDs with the
IDs in other provider domains is a matter for the providers. A
solution should provide an API between the providers to flexibly
support various mapping methods.
4.3 Accounting
MACCNT-REQ-draft defines requirements for Accounting and Billing.
These include the requirement for the NSP to log user behavior such
as the join action and the leave action, as well as the result of
the access-control decision. (MACCNT-REQ-draft, 4.5) MACCNT-REQ-
draft also specifies that there should be a standardized format for
sharing with the CP the user behavior and content reception
information which the NSP is logging.(MACCNT-REQ-draft, 4.5.1)
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In order to provide the granularity of user-behavior and actual
content reception information as specified in MACCNT-REQ-draft, the
NSP should not manage multicast states on a subnet basis, but on a
user basis (see in MACCNT-REQ-draft, 4.1 "User identification")
because the NSP needs to be able to notify the CP of a user's start
and stop times for accounting purposes. This means that the NSP
sends to the CP AAA an indication for Join and Leave on a user
basis.
This framework specifies an accounting API provided by the NSP and
accessed by the CP to allow for sharing user-behavior and content-
reception information between the NSP AAA and CP AAA. This
accounting API should be configurable to allow the CP to request
only the logging information it actually requires. Such an API
would allow for realtime accounting information sharing by the NSP
to the CP. When logging information is shared through the accounting
API, it is important that the CP be able to match the user as
described in the database operated by the NSP to the user as
described in the database operated by the CP.
The NSP requires the capability to log both user and host
information for each join and leave, indicating the corresponding
multicast source for each action. When either a CP source stops
sending, or the NSP stops multicasting, in an unsolicited manner,
there is also a need to notify the AAA servers accordingly about the
users who are impacted by this event.
Also, intermittent logs between the join and leave would allow for
finer diagnostics and therefore could serve useful in billing
discrepancies, and provide for a better estimation of the time span
that content was multicasted in the even that users disconnect
without sending leave messages.
4.4 Access Control and CP selection by NSP
When a NSP receives an access request from a user, it is necessary
for the NSP to determine to which CP the request is to be directed.
It is necessary for the NSP to ensure that it is not spoofed by an
inappropriate CP or user.
4.5 API for Admission Control Information by NSP
After authorizing a user request, the NSP may have further
conditions for determining its admission control decision. MACCNT-
REQ-draft defines requirements for providing the network capability
to conduct admission control based on the network bandwidth usage
status and bandwidth management policy. (MACCNT-REQ-draft, 4.2.2,
Satou, Ohta, Jacquenet, Hayashi, He [Page 9]
INTERNET-DRAFT AAA Framework for Multicasting March 2007
4.2.3 & 4.9) Such QoS measurement and policy mechanisms themselves
are out of the scope of this memo. However the NSP's AAA Server
should be provided with an Admission control API that allows for
interfacing so that additional conditions can be added to the
admission control decision.
4.6 Access Control and Distinguishing of Users by CP
The user ID and authentication information are forwarded
transparently by the NSP so that the CP can distinguish the user, as
well as authenticate and authorize the request.
4.7 Caching of AAA results
An NSP should be able to cache AAA results based upon an agreement
between the NSP and a CP. The AAA cache would store information
about permissions of a specific user to receive multicast data from
specified channel(s) up to specified expiration date(s) and time(s).
If such caching is implemented, a method must exist for the CP to
communicate this permission information to the NSP. The NSP refers
to the AAA cache and if the cache indicates that the user has
permission to receive multicast data from a specific channel at that
time, the NSP may forward the data without querying the CP.
It should be possible for a CP to send unsolicited requests to the
NSP to refresh or change the permissions for a user for specific
channel(s).
When a user is receiving multicast content and the permission is
about to expire, the NSP may send a notification to the user client
that his session is about to expire, and that he will need to re-
connect. The user will have to reestablish a connection. In the
case that the user still has permission to the content, they should
be able to continue to receive the content without interruption.
5. Network Connection Model and Functional Components
Section 3.1 introduces the high-level AAA framework for multicasting.
This section provides more detail on the network connection model
and constituent functional components.
5.1 Basic Connection Model
+-------------+
| user |
| |
+-------------+
^ Access & Resource
Satou, Ohta, Jacquenet, Hayashi, He [Page 10]
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| Request
v
+-------------+
| NSP= NAP |
| |
+-------------+
^ Access
| Request
v
+-------------+
| CP |
| |
+-------------+
In this case the NSP is the sole entity providing Network Service
Provision including Network Access Provision to the User. First a
user that requests content sends an Access request to an NSP which
then forwards it on to the appropriate CP for Authentication and
Authorization purposes. The CP responds with either "success" or
"failure". If "success", the NSP may forward a success response and
stream multicast data to the user.
In this model the user selects the NSP to which to send its content
request. Based on this request the NSP selects an appropriate CP to
which it forwards the request. The CP responds to the NSP's request:
it may not respond to another NSP in regards to the request.
In this model, as described in section 3.1, the relationship between
NSP and CP can be 1:1, 1:N or M:N. Users may connect to multiple
networks, and networks have multiple users.
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5.2 Transit Provision
The diagram below shows that Network Service Provision may include
both Network Access Provision to the User and also Transit Provision
(request relay) between the Network Access Provider (NAP) and the CP.
Transit Provision is the responsibility of the NSP which may or may
not contract out this service to a separate NSP that acts as the
Transit Provider. The existence of the Transit Provider is
transparent to the user.
+-------------+
| user |
| |
+-------------+
^ Access & Resource
| Request
v
+- - - - - - - - - - - - - - +
|+----------------+
| Network Access | |
|| Provision | Network Service
+----------------+ | Provision
| ^ Access & Resource
| Request |
| v
+-------------+ |
|| Transit |
| Provision | |
|+-------------+
+- - - - - - - - - - - - - - +
^ Access
| Request
v
+-------------+
| CP |
| |
+-------------+
For the sake of simplification the above diagram shows a 1-1
relationship between an NAP and a TP. However it is also possible
for a single NAP to connect to multiple TPs, and a single TP to
multiple NAPs.
A single TP may connect to one or more CPs. Similarly just as a
single CP may connect to multiple NAPs (as described in the general
high-level framework, section 3.1), a single CP may connect to one
or more TPs.
A solution will include a mechanism through which the NAPs know
which TP(s) are to be used to communicate with which CP(s), and CPs
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know which TP(s) to use for which NAP(s). When a TP receives an
access or resource request from an NAP or CP, it must relay the
request to the correct CP or NSP, respectively. Minimally, this
means that it must reconstruct the request with translated address
information. In this model therefore a TP must understand the
format and meaning of the requests.
There may be multiple TPs between a NAP and CP so that a TP is
actually receiving from and/or sending requests to another TP and
not directly from/to a NAP or CP.
5.3 Transit with Tunnels
In addition to the above model of request relaying, a TP may
communicate requests through tunneling based on the contract between
the TP and the NAP and/or between the TP and the CP. So in this
case the TP will not directly need to process the contents of the
access and resource request (such as, header information), but
instead pass the request directly to the correct NSP or CP, using a
separate protocol to wrap the original requests.
Below is a diagram, representing how a TP can provide tunneling
between NAP(s) and CP(s).
+-----------------+
| user |
| |
+-----------------+
^ Access & Resource
| Request
v
+ - - - - - - - - - - +
+------------------+
|| NAP | |
| |
|+------------------+ | Network
|^|
| |:| | Service
|:|
|+-|:|--------------+ | Provision
| |:| TP |
|| |:| | |
+-|:|--------------+
+ -|:|- - - - - - - - +
|:| Tunnel
|:|
|V|
+------------------+
| CP |
| |
Satou, Ohta, Jacquenet, Hayashi, He [Page 13]
INTERNET-DRAFT AAA Framework for Multicasting March 2007
+------------------+
In this model too, the relationship between NAP and TP and between
TP and CP can be 1:1, 1:N or M:N.
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5.4 Constituent Logical Functional Components of the fully enabled AAA
Framework
Section 3.1 introduces the high-level AAA framework for multicasting.
Below is a diagram of a fully enabled multicasting network with AAA,
including the logical components within the various entities.
+-------------------------------+
| user |
| |
+-------------------------------+
^
| Access & resource request
v
+-------------------------------+
| NSP |
| |
|+--------------+ +---------+|
||NR Management |<-->|AAA Proxy|| (NR= network resource)
|+--------------+ RR +---------+| (RR= resource request)
+-------------------------------+
^
| Access request
v
+------------------------------+
| CP |
| |
| +---------+ |
| | AAA | |
| +---------+ |
+------------------------------+
In the fully enabled model the NSP provides proxying of
authentication and authorization between the NSP and CP, as well as
user-based accounting. The AAA proxy server of the NSP communicates
with the CP's AAA server. Although not shown in the above diagram
for the sake of simplicity, in addition to direct proxying between a
NSP and CP, this proxying may be done through a TP. This means that
the transit provider is also cable of supporting AAA proxying.
In the fully enabled model the NSP also includes a component that
provides network resource management (e.g. QoS management), as
described in section 3.4, "Network Resource Management by NSP".
When a transit provider is used it may also provide Network Resource
management of its own resources.
5.5 Modularity of the framework
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In the interest of flexibility, this framework is modular so that it
is possible that partially enabled versions of the models are
supported. A AAA-enabled version provides AAA functionality without
Network Resource management. A Network-Resource-Management-enabled
(QoS-enabled) version provides Network Resource management without
AAA functionality. Similarly, the possibility of one or more layers
of transit provision between an NSP and CP is in the interest of
modularity and extendibility.
6. IANA considerations
This memo does not raise any IANA consideration issues.
7. Security considerations
Refer to section 3.3. Also the user information related to
authentication with the CP must be protected in some way.
Otherwise, this memo does not raise any new security issues which
are not already addressed by the original protocols. Enhancement of
multicast access control capabilities should enhance security
performance.
8. Conclusion
This memo provides a generalized framework for solution standards to
meet the requirements presented in MACCNT-REQ-draft. Further work
should be done to break down the content provider and network
service provider entities into their functional objects such as edge
devices, AAA servers, etc.
Normative References
[1] Hayashi, et. al., "Accounting, Authentication and Authorization
Issues in Well Managed IP Multicasting Services", draft-ietf-
mboned-maccnt-req-04.txt, February 2006, Work in Progress.
Authors' Addresses
Hiroaki Satou
NTT Network Service Systems Laboratories
3-9-11 Midoricho, Musashino-shi, Tokyo, 180-8585 Japan
Phone : +81 422 59 4683
Email : satou.hiroaki@lab.ntt.co.jp
Hiroshi Ohta
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NTT Network Service Systems Laboratories
3-9-11 Midoricho, Musashino-shi, Tokyo, 180-8585 Japan
Phone : +81 422 59 3617
Email: ohta.hiroshi@lab.ntt.co.jp
Christian Jacquenet
France Telecom
3, avenue Francois Chateau
CS 36901, 35069 Rennes Cedex, France
Phone: +33 2 99 87 63 31
Email: christian.jacquenet@francetelecom.com
Tsunemasa Hayashi
NTT Network Innovation Laboratories
1-1 Hikari-no-oka, Yokosuka-shi, Kanagawa, 239-0847 Japan
Phone: +81 46 859 8790
Email: tsunemasa@gmail.com
Haixiang He
Nortel
600 Technology Park Drive
Billerica, MA 01801, USA
Phone: +1 978 288 7482
Email: haixiang@nortel.com
Comments
Comments are solicited and should be addressed to the mboned working
group's mailing list at mboned@lists.uoregon.edu_and/or the authors.
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