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 This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on March 28, 2001. 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. Gilletti, et. al. Expires March 28, 2001 [Page 1] Internet-Draft CDNPBE September 2000 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 Gilletti, et. al. Expires March 28, 2001 [Page 2] Internet-Draft CDNPBE September 2000 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. Gilletti, et. al. Expires March 28, 2001 [Page 3] Internet-Draft CDNPBE September 2000 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; Gilletti, et. al. Expires March 28, 2001 [Page 4] Internet-Draft CDNPBE September 2000 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. Gilletti, et. al. Expires March 28, 2001 [Page 5] Internet-Draft CDNPBE September 2000 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. Gilletti, et. al. Expires March 28, 2001 [Page 6] Internet-Draft CDNPBE September 2000 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. Gilletti, et. al. Expires March 28, 2001 [Page 7] Internet-Draft CDNPBE September 2000 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. Gilletti, et. al. Expires March 28, 2001 [Page 8] Internet-Draft CDNPBE September 2000 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 Gilletti, et. al. Expires March 28, 2001 [Page 9] Internet-Draft CDNPBE September 2000 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. Gilletti, et. al. Expires March 28, 2001 [Page 10] Internet-Draft CDNPBE September 2000 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. Gilletti, et. al. Expires March 28, 2001 [Page 11] Internet-Draft CDNPBE September 2000 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 Gilletti, et. al. Expires March 28, 2001 [Page 12] Internet-Draft CDNPBE September 2000 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. Gilletti, et. al. Expires March 28, 2001 [Page 13] Internet-Draft CDNPBE September 2000 9. Security Considerations This document assumes that the solutions suggested within this document will be compliant with the trust model given in [4]. Gilletti, et. al. Expires March 28, 2001 [Page 14] Internet-Draft CDNPBE September 2000 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. Gilletti, et. al. Expires March 28, 2001 [Page 15] Internet-Draft CDNPBE September 2000 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). Gilletti, et. al. Expires March 28, 2001 [Page 16] Internet-Draft CDNPBE September 2000 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, . [2] Day, M. and D. Gilletti, "Content Distribution Network Peering Scenarios", draft-day-cdnp-scenarios-00.txt, (work in progress), September 2000, . [3] Green, M., Cain, B. and G. Tomlinson, "Content Distribution Network Peering Framework", draft-green-cdnp-framework-00.txt, (work in progress), September 2000, . [4] Aboba, B., Arkko, J. and D. Harrington, "Introduction to Accounting Management", draft-ietf-aaa-acct-06.txt (work in progress), June 2000, . 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 Gilletti, et. al. Expires March 28, 2001 [Page 17] Internet-Draft CDNPBE September 2000 John Scharber Entera, Inc. 40971 Encyclopedia Circle Fremont, CA 94538 US Phone: +1 510 770 5201 EMail: john@entera.com Gilletti, et. al. Expires March 28, 2001 [Page 18] Internet-Draft CDNPBE September 2000 Full Copyright Statement Copyright (C) The Internet Society (2000). All Rights Reserved. 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