One document matched: draft-gilletti-cdnp-accounting-models-00.txt
Network Working Group D. Gilletti
Internet-Draft Entera
Expires: March 28, 2001 R. Nair
Cisco
J. Scharber
Entera
September 27, 2000
Accounting Models for CDN Peering
draft-gilletti-cdnp-accounting-models-00.txt
Status of this Memo
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Copyright Notice
Copyright (C) The Internet Society (2000). All Rights Reserved.
Abstract
This document presents several conceptual and logical models for
accounting activities between peered CDNs. This is a new piece of
work intended to enumerate the issues and provide additional detail
for use when deriving the ACCOUNTING PEERING SYSTEM for a CDN
peering model.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Accounting . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Key Assumptions . . . . . . . . . . . . . . . . . . . . . . . 6
4.1 Content Has Value . . . . . . . . . . . . . . . . . . . . . . 6
4.2 Distribution Has Value . . . . . . . . . . . . . . . . . . . . 6
4.3 Users Have Value . . . . . . . . . . . . . . . . . . . . . . . 6
5. Conceptual Accounting Models . . . . . . . . . . . . . . . . . 7
5.1 The Cable Model . . . . . . . . . . . . . . . . . . . . . . . 7
5.2 The Telco Model . . . . . . . . . . . . . . . . . . . . . . . 7
5.3 The Ticket Model . . . . . . . . . . . . . . . . . . . . . . . 8
5.4 The Calling Card Model . . . . . . . . . . . . . . . . . . . . 8
6. Logical Accounting Models . . . . . . . . . . . . . . . . . . 9
6.1 The Accounting Transaction Model . . . . . . . . . . . . . . . 9
6.2 Other Logical Accounting Models . . . . . . . . . . . . . . . 10
7. Accounting Issues . . . . . . . . . . . . . . . . . . . . . . 11
7.1 Collection Methods for Transactional Accounting . . . . . . . 11
7.2 Other Issues . . . . . . . . . . . . . . . . . . . . . . . . . 11
8. Recommendations . . . . . . . . . . . . . . . . . . . . . . . 12
9. Security Considerations . . . . . . . . . . . . . . . . . . . 14
10. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . 15
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 16
References . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 17
Full Copyright Statement . . . . . . . . . . . . . . . . . . . 19
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1. Introduction
In an effort to derive a solution for the interconnection or peering
of Content Delivery Networks (CDNs) an abstract system model was
created to provide an adequate frame of reference. This model, as
described in [3], identifies three basic elements:
1. REDIRECTION PEERING SYSTEM
2. DISTRIBUTION PEERING SYSTEM
3. ACCOUNTING PEERING SYSTEM
This document presents several conceptual and logical accounting
models which SHOULD be considered when deriving the ACCOUNTING
PEERING SYSTEM for a peered CDN model. It also provides a list of
additional considerations as well as some recommendations for
potential solutions.
The models set forth in this document assume that the BILLING CDN
(as defined in [1]) can either be a party actively involved in the
distribution exchange, or a third party who may provide various
levels of billing and transaction related functions (i.e. a
settlement entity).
These models are intended to indicate some of the high-level
relationships between various elements of the DISTRIBUTING CDN. And,
whenever possible, they also attempt to indicate the flows and the
nature of the requirements for access or statistical information by
the BILLING CDN as well as other parties involved in the
transaction. These models also recognize that there may be multiple
interested BILLING CDNS who require this information.
Since the concentration of this effort is to determine the
requirements for peering CDNs data produced and consumed within an
individual CDN is ignored within this document.
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2. Terminology
This section introduces new terminology not already defined in [1]:
CDN SERVICE: an action that is directly or indirectly related to the
act of moving CONTENT from PUBLISHER to CONSUMER;
PROVIDER: an entity that offers a CDN SERVICE in exchange for
COMPENSATION;
COMPENSATION: remuneration that flows from CUSTOMER to PROVIDER in
exchange for a CDN SERVICE;
CUSTOMER: a billable entity that agrees to exchange COMPENSATION for
a CDN SERVICE;
ENTITLEMENT: a right to access a given CDN SERVICE or CONTENT object
which is given to the CUSTOMER by the PROVIDER
USAGE: a counter that measures the access or use of a CDN SERVICE by
the CUSTOMER;
PERIOD: the duration for which the USAGE counter is active;
USAGE RATE: a per-unit cost associated with the USEAGE of a CDN
SERVICE;
UNIT OF MEASURE (UOM): indicates how USAGE should be tracked (i.e.
minutes, seconds, bytes, etc);
FLAT RATE: indicates there is no limit on the amount of CDN SERVICE
that a CUSTOMER can consume during a PERIOD;
TIERED: indicates the existence of a schedule against which USAGE of
a given CDN SERVICE is tracked and billed;
PERCENTILE: indicates that a CDN SERVICE will be billed cost that is
based on a multiplier (USAGE RATE) times the USAGE during the
PERIOD;
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3. Accounting
There are several concepts that are helpful to consider when
attempting to model the various accounting scenarios that can be
realized when peering CDNs. The most fundamental of these is the
assignment of value within the distribution exchange.
In any distribution system revenue will generally flow in the
direction of value. In order to insure that this revenue flows
accurately, it is necessary to provide accurate statistical and
access related information to one or more BILLING CDNS. In general
it can be assumed that accounting information originates at the
DISTRIBUTION SYSTEMS and flows towards the BILLING CDNS. However it
is entirely appropriate to consider that this data may flow through
one or more aggregation points. In fact the ability to aggregate
statistical and access related information is essential to allow for
scalability within the proposed solution.
It should be noted that value exists at many points in a peered
DISTRIBUTION SYSTEM. To fully consider this problem one should
assume that, in general, any element of the DISTRIBUTION SYSTEM can
have an assigned value associated with its use. This raises some
obvious questions about settlement which are outside the scope of
this document. For the purposes of this effort it is sufficient to
insure that the appropriate accounting data is capable of being
transferred from the measurement point to the ACCOUNTING SYSTEM.
The authors of this document also recognize the fact that it is
impossible, at present, to fully capture all of the current and
future requirements for accounting and statistical information.
Instead, this document contains some fundamental known concepts and
requirements and proposes an extensible framework for the carriage
of accounting information through a peered DISTRIBUTION SYSTEM.
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4. Key Assumptions
The distribution of accounting information, like the distribution of
content, is greatly affected by the following concepts.
4.1 Content Has Value
This concept assumes that the content has intrinsic value and that
the revenue (and accounting information) flows from the CONSUMER to
the CONTENT PROVIDER. A CONSUMER, as defined in this relationship,
is the entity which consumes data. Therefore the CONSUMER may be a
CLIENT or a SURROGATE.
An example of this concept would include services such as Video On
Demand (VOD).
4.2 Distribution Has Value
This concept describes the situation where the value is located
within the SERVICE PROVIDER. In this case the revenue as well as the
statistical and access information flow toward the SERVICE PROVIDER.
When considering this case, it is a reasonable assumption to
consider that the majority of the necessary statistical and access
information would be produced and consumed within the SERVICE
PROVIDER's domain and is therefore not important to consider.
However, it is not reasonable to assume that all such information is
obtained in this manner. The latter is especially true when a
third-party BILLING CDN or complex peering arrangements are in place.
An example of this case is where a SERVICE PROVIDER has an
aggregated CLIENT population which is of sufficient interest to one
or more CONTENT PROVIDERS. In this case the CONTENT PROVIDERs are
willing to pay to access the CLIENTs of the SERVICE PROVIDER and
revenue flows from the CONTENT PROVIDER to the SERVICE PROVIDER.
4.3 Users Have Value
This concept describes the fact that an aggregation of users or
CLIENTS may also represent significant value in the DISTRIBUTION
chain.
The same example as above applies to this case.
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5. Conceptual Accounting Models
There are four basic conceptual accounting models that SHOULD be
considered when describing the requirements for the peering of
accounting events between peered distribution entities:[Editor's
Note: Other models suitable for realtime provisioning may be added
to this proposal over time.]
o Flat Rate Accounting Model - (aka "The Cable Model)
o Metered Accounting Model - (aka "The Telco Model")
o Prepay Event Accounting Model - (aka "The Ticket Model")
o Prepay Metered Accounting Model - (aka "The Calling Card Model")
These models are described in the following sections.
5.1 The Cable Model
In this model there is a "subscription" fee associated with the
reception of CONTENT. In its primary mode it consists of a CLIENT
entering into a transaction, either directly with the CONTENT
PROVIDER or through some third party, for the purposes of obtaining
access to one or more CONTENT OBJECTs. Once the transaction has been
approved the CLIENT receives an entitlement to access the requested
CONTENT for the duration of the subscription interval.
An extension to this model is the case where a given DISTRIBUTION
CDN enters into a redistribution agreement with a CONTENT PROVIDER.
In this scenario, the scope of the transaction is between the
CONTENT PROVIDER and the specific DISTRIBUTION CDN. Once the
transaction is successful, the DISTRIBUTION CDN obtains the right to
redistribute that content in some mutually agreed upon manner. The
manner of redistribution can range from unlimited to highly
restricted.
The resultant accounting information for this model consists of a
single transaction which is associated with a specific CONSUMER.
5.2 The Telco Model
This model associates a finite value with the access or consumption
of one or more CONTENT OBJECTs and attempts to fully control and/or
account for access to these OBJECTs.
The resultant accounting information for this model is a set of
detailed or summary accounting records associated with a specific
CLIENT.
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5.3 The Ticket Model
In this model the CLIENT obtains a ticket (or entitlement) in
advance of accessing the CONTENT. This is accomplished by a
transaction between the CLIENT and the CONTENT PROVIDER or their
agent(s). The ticket is a one-time ENTITLEMENT which expires upon
use.
5.4 The Calling Card Model
In this model a consumer prepays and receives an ENTITLEMENT to
access a set of CONTENT OBJECTS up to some pre-specified value
level. The total value of the ENTITLEMENT is determined at the time
of purchase and its value is decremented each time the CUSTOMER
accesses the CDN SERVICE. The amount of the decrement will be
specific to the CDN SERVICE being accessed. The CUSTOMER is able to
continue to access the CDN SERVICE until the ENTITLEMENT is fully
depleted.
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6. Logical Accounting Models
This section describes the logical accounting models that SHOULD be
considered when deriving ACCOUNTING ELEMENTS for a peered CDN model.
6.1 The Accounting Transaction Model
There are four separate components required to create a flexible
accounting transaction model for a Content Distribution Network
(CDN);
METHOD
ESTABLISHMENT
MEASUREMENT
PAYMENT.
A METHOD is used to define the UNIT OF MEASURE (UOM), ALGORITHM and
PERIOD used to calculate USAGE FEE for a BILLABLE EVENT. The
ALGORITHM indicates how the UOM should be applied. Primitive
ALGORITHM types include; FLAT RATE, TIERED, PERCENTILE although more
complex applications may be constructed. The PERIOD specifies the
duration for which the METHOD is valid. A METHOD may be applied on
a per unit basis or a METHOD may also be applied over a time periods
such as a day or a month.
A TRANSACTION is CUSTOMER initiated action requesting access to a
specific CDN SERVICE being offered by the PROVIDER.
A CDN SERVICE has a specified METHOD for accounting purposes.
The ESTABLISHMENT SYSTEM ensures that the requestor is AUTHORIZED
and includes the appropriate STATE and METHOD to allow accurate
measurement for the current request. The ESTABLISHMENT system will
communicate with the ACCOUNTING system to determine the state
information that is required and could include such information as
ENTITLEMENTs. The ESTABLISHMENT system also ensures that DIGITAL
RIGHTS of a requestor are consistent with its ENTITLEMENTS.
The MEASUREMENT SYSTEM provides a means of tracking and reporting
utilization or ACCOUNTING EVENTS back to a ACCOUNTING SYSTEM. The
MEASUREMENT SYSTEM may also aggregate responses to the accounting
system based on the METHOD applied to a given request and the STATE
information returned from the ESTABLISHMENT system.
The ACCOUNTING SYSTEM provides for REAL TIME or OFFLINE PROCESSING
of ACCOUNTING EVENTs and tracks USER, STATE and METHOD information
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that are applied to a specified TRANSACTION type. The payment
system allows for the definition of USER, CDN SERVICE records.
6.2 Other Logical Accounting Models
Other logical accounting models will be included here.
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7. Accounting Issues
This section lists some additional issues that SHOULD be considered
in order to have a complete solution for accounting across peered
CDNs.
7.1 Collection Methods for Transactional Accounting
In a Layer 3 network, the most granular entity is a flow whereas in
a layer 5 network, the most granular entity is a CONTENT request.
Observations have shown that many web sites will use a single TCP
connection for upwards of 20 content requests.
This would imply that a simple log at the CONTENT level would result
in at least 20 times the log volume of a layer 3 log. Moreover, at
the CDN level the problem becomes worse because we could be required
to transmit logs from all the CDN nodes back to the BILLING CDN. The
issue here is not simply one of available bandwidth for
transmission. Rather, it is the problem of processing large volumes
of logs.
Thus, it becomes important to aggregate at the granularity of
billable events whose definition is perhaps left open.
One way to reduce this information is to be able to aggregate the
logs by Domain Names or URL-sets (i.e., wildcards or ranges) and
transport these aggregates across the CDNs.
It would be extremely advantageous to implement the ability for
involved parties to define, via an open interface, the billable
events that the CDN would like to use, (i.e., Domain Name, URL-set,
etc). This interface SHOULD have an XML vocabulary that is used to
describe these events.
Solutions SHOULD allow the aggregation to be performed at the
Content Delivery Nodes, so that the DISTRIBUTION SYSTEM need only
deal with the transport of this aggregated information among the
peering CDNs.
It is worth noting that there are many events which aren't easy to
represent in standard log formats. These include things such as QoS
delivery to consumer, content mixing, target ad insertion and other
value added services.
7.2 Other Issues
Other noteworthy issues will be included here.
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8. Recommendations
One means of accommodating these types of services is to build off
of the ongoing work of the IETF AAA WG [4]. At present this work is
centered on the DIAMETER framework and protocol suite for both
provisioning and accounting. Early observations indicate that
DIAMETER has several characteristics that are desirable for
consideration in fulfilling these accounting requirements. The high
point characteristics are that it:
Has a model that supports either direct aggregation to home
provider 3rd party brokering.
Has well developed security and trust relationships.
Supports standardized, extensible accounting record format.
Is generally extensible via object oriented techniques.
The general model of extending DIAMETER is to define required
extensions to the protocol much like one would do to an abstract
base class in C++ via base class and subclassing.
Although its a bit premature to fully assess the suitability of
DIAMETER to meet these requirements, early observations indicate
that it sets forth a reasonable framework from which to develop a
base model for this effort.
Early observations have also identified the following issues with
the model that will likely create a need for the following
extensions to the base framework:
1. DIAMETER works on a request-by-request basis like pay-per-view.
While this model is okay for some applications, it will have to
be extended to support cases where a CDN pays at a larger
granularity (e.g., by a million content hits) and then resells
to its users or another CDN. This would apply to cases where a
CDN subscribes to a peered BILLING CDN or pays for distribution
in a peering CDN. Existing DIAMETER mechanisms could be used for
pay-per-view content inside a CDN but may need a higher level
protocol across CDNs for aggregate content programming. This
protocol SHOULD co-exist with DIAMETER message proxying. It can
borrow message routing models from DIAMETER (e.g. realm-based
routing).
2. DIAMETER uses end-to-end security. This may not work well across
CDN boundaries. As previously discussed, it may be necessary to
be flexible about the definition of the "end" to be the CDN
boundary. This will be consistent with the need for CDNs to
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serve as a content provisioning entity and makes it possible to
aggregate request traffic.
3. DIAMETER needs to be extended with AVPs specific to web-based
billable events.
More detailed analysis needs to be undertaken before these
conclusions can be validated.
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9. Security Considerations
This document assumes that the solutions suggested within this
document will be compliant with the trust model given in [4].
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10. Conclusion
This document presents four conceptual models as a starting point
for discussion on accounting for CDN peering. Some fundamental
issues are raised and potential solutions proposed. It is recognized
that this work will be progressed further within the IETF.
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11. Acknowledgements
The authors acknowledge the contributions and comments of Brad Cain
(Mirror Image), Mark Day (Cisco), Fred Douglis (AT&T), John Martin
(Network Appliance), Doug Potter (Cisco), Oliver Spatscheck (AT&T),
and Gary Tomlinson (Entera).
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References
[1] Day, M. and G. Tomlinson, "A Model for Content Distribution
Network Peering", draft-day-cdnp-model-00.txt, (work in
progress), September 2000,
<URL:http://www.ietf.org/internet-drafts/draft-day-cdnp-model-00
.txt>.
[2] Day, M. and D. Gilletti, "Content Distribution Network Peering
Scenarios", draft-day-cdnp-scenarios-00.txt, (work in
progress), September 2000,
<URL:http://www.ietf.org/internet-drafts/draft-day-cdnp-scenario
s-00.txt>.
[3] Green, M., Cain, B. and G. Tomlinson, "Content Distribution
Network Peering Framework", draft-green-cdnp-framework-00.txt,
(work in progress), September 2000,
<URL:http://www.ietf.org/internet-drafts/draft-green-cdnp-framew
ork-00.txt>.
[4] Aboba, B., Arkko, J. and D. Harrington, "Introduction to
Accounting Management", draft-ietf-aaa-acct-06.txt (work in
progress), June 2000,
<URL:http://www.ietf.org/internet-drafts/draft-ietf-aaa-acct-06.
txt>.
Authors' Addresses
Don Gilletti
Entera, Inc.
40971 Encyclopedia Circle
Fremont, CA 94538
US
Phone: +1 510 770 5281
EMail: don@entera.com
Raj Nair
Cisco Systems
50 Nagog Park
Acton, MA 01720
US
Phone: +1 978 206 3029
EMail: rnair@cisco.com
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John Scharber
Entera, Inc.
40971 Encyclopedia Circle
Fremont, CA 94538
US
Phone: +1 510 770 5201
EMail: john@entera.com
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