Content Distribution Interworking D. Gilletti
Working Group CacheFlow, Inc.
Internet-Draft R. Nair
Expires: December 12, 2002 Cisco Systems
J. Scharber
CacheFlow, Inc.
J. Guha
Apogee Networks
D. Frascone
Blackstorm Networks
June 13, 2002
Content Distribution Interworking (CDI) AAA Requirements
draft-ietf-cdi-aaa-reqs-01
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
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Copyright Notice
Copyright (C) The Internet Society (2002). All Rights Reserved.
Abstract
In developing a solution for CDN Internetworking it is necessary to
define and accommodate requirements for Authentication,
Authorization, and Accounting. Since the Authentication,
Authorization, and Accounting (AAA) working group is already focused
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on defining these requirements, this document attempts to leverage
that work. It contains the requirements that would have to be
supported by a AAA service to formulate a solution for CDN peering.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 4
1.1 Conventions used in this document . . . . . . . . . . . . 5
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 6
3. Overview of Accounting Peering System . . . . . . . . . . 8
4. Assumptions . . . . . . . . . . . . . . . . . . . . . . . 10
4.1 Firewalls . . . . . . . . . . . . . . . . . . . . . . . . 10
4.2 CDR Generation & Reception . . . . . . . . . . . . . . . . 10
4.3 Storage Requirements . . . . . . . . . . . . . . . . . . . 10
4.4 Authentication & Authorization . . . . . . . . . . . . . . 10
4.5 Measurement / Metering Systems . . . . . . . . . . . . . . 10
4.6 Inter-Domain Trust . . . . . . . . . . . . . . . . . . . . 11
4.7 Proxy CDN-I Account-Peering systems . . . . . . . . . . . 11
5. Accounting 'Works' . . . . . . . . . . . . . . . . . . . . 12
5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . 12
5.2 General Requirements . . . . . . . . . . . . . . . . . . . 12
5.2.1 Framework . . . . . . . . . . . . . . . . . . . . . . . . 12
5.2.2 Form-Factor of CDRs . . . . . . . . . . . . . . . . . . . 13
5.2.3 Timing Requirement of CDR exchange . . . . . . . . . . . . 13
5.2.4 Identifiers . . . . . . . . . . . . . . . . . . . . . . . 13
5.2.5 Measures . . . . . . . . . . . . . . . . . . . . . . . . . 13
5.2.6 Counters . . . . . . . . . . . . . . . . . . . . . . . . . 13
5.2.7 Name Space Convention (Distributed,Domained,Global) . . . 13
5.2.8 Security Requirements . . . . . . . . . . . . . . . . . . 14
5.3 Core Works Requirements . . . . . . . . . . . . . . . . . 14
5.3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . 14
5.3.1.1 List of Attributes . . . . . . . . . . . . . . . . . . . . 14
5.3.1.2 Encoding and Representation . . . . . . . . . . . . . . . 14
5.3.1.3 Use Case Model . . . . . . . . . . . . . . . . . . . . . . 14
5.3.1.4 Work Flow Model . . . . . . . . . . . . . . . . . . . . . 15
5.3.1.5 Work State Model . . . . . . . . . . . . . . . . . . . . . 15
5.3.2 ContentInjection Work . . . . . . . . . . . . . . . . . . 15
5.3.3 ContentDistribution Work . . . . . . . . . . . . . . . . . 16
5.3.4 ContentRequest Work . . . . . . . . . . . . . . . . . . . 16
5.3.5 ContentRetrieval Work . . . . . . . . . . . . . . . . . . 17
5.3.6 ContentServiceDelivery Work . . . . . . . . . . . . . . . 18
6. Data Exchange Mechanism / Protocol . . . . . . . . . . . . 20
6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . 20
6.2 General Requirements . . . . . . . . . . . . . . . . . . . 20
6.2.1 Separation of Exchange Protocol from CDR payload . . . . . 20
6.2.2 Transfer Capability Negotiation . . . . . . . . . . . . . 20
6.2.3 Singular, Batched, Flow, & RealTime Modes of Data Exchange 20
6.2.4 Efficient Encoding . . . . . . . . . . . . . . . . . . . . 20
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6.2.5 Transfer Flow & Rate Control . . . . . . . . . . . . . . . 20
6.2.6 Guaranteed Delivery . . . . . . . . . . . . . . . . . . . 20
6.2.7 CDR Relationship Identifiers . . . . . . . . . . . . . . . 21
6.2.8 Protocol State Machines . . . . . . . . . . . . . . . . . 21
6.2.9 Encryption . . . . . . . . . . . . . . . . . . . . . . . . 21
6.3 Authorization and Authentication . . . . . . . . . . . . . 21
6.4 CDR Receivers . . . . . . . . . . . . . . . . . . . . . . 21
6.5 CDR Generators : . . . . . . . . . . . . . . . . . . . . . 21
6.6 Fault-Tolerance . . . . . . . . . . . . . . . . . . . . . 21
7. Further Issues . . . . . . . . . . . . . . . . . . . . . . 23
8. Recommendations . . . . . . . . . . . . . . . . . . . . . 24
9. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . 25
References . . . . . . . . . . . . . . . . . . . . . . . . 26
Authors' Addresses . . . . . . . . . . . . . . . . . . . . 26
A. Acknowledgments . . . . . . . . . . . . . . . . . . . . . 28
Full Copyright Statement . . . . . . . . . . . . . . . . . 29
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1. Introduction
The initial model for the World Wide Web (WWW) was based on clients
interacting with origin servers to request and receive content or
services. As the Web increased in scale this model proved unwieldy
for several reasons and resulted in current industry efforts to build
and operate Content Distribution Networks or CDNs. The overall
purpose of these CDNs is to create a scalable service that can meet
aggregate client demand while improving the performance and quality
of delivery. With increased demand for CDN services a need has been
generated for a mechanism for interconnecting or peering these
systems.
A typical CDN has relationships with publishers and provides them
with accounting and access related information. This information is
typically provided in the form of aggregate or detailed log files.
In addition, these CDNs typically collect accounting information to
aid in operation, billing and SLA verification. Since all accounting
data is collected within the CDN's administrative domain there is no
requirement for generalized systems or protocols.
Peering or interconnecting these CDNs introduces the need to obtain
similar accounting data from a foreign domain. This requirement
means that customers of a peered CDN service (publishers, clients,
and CDNs) must now have a generalized or standard means of obtaining
accounting information to support current as well as planned business
models. For example, the desire to implement business models such as
"Pay Per View" may require that there exist a mechanism for
authenticating and authorizing clients at a delivery point that lies
in a foreign domain.
This document is focused on describing requirements for the
Accounting Peering System as described in [7]
This document frames the requirements for the Accounting Peering
System against the ongoing work of the AAA working group. This was
done because the authors realized that considerable effort has
already been expended in identifying inter-domain trust models and
accounting requirements within that working group. Therefore, a
conscious decision has been made to leverage that existing body of
work before making additional proposals. As such, this document
relies heavily on RFC 2904 [1], RFC 2975 [2], and RFC 2977 [3].
Since the concentration of this effort is to determine the
requirements for CDN internetworking / peering, the accounting
requirements within an individual CDN are largely ignored within this
document.
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The core actions and activities within the CDN-I domain is
essentially enumerated as Content Injection, Content Distribution,
Content Request, Content/Service Delivery, and Content Retrieval.
These are the primary activities that need to be tracked and
accounted. Please refer architectural diagrams in [5], [6], and [7].
This document focuses and details the requirements on the digital
representation of the above activities, along with the means and
mechanisms to exchange these representations between peering parties
which have participated in the activity, and/or any other component
in a secure and guaranteed manner.
Requirements for the remaining CDI architectural elements, the
Request Routing System, which is responsible for directing user
agents to the distributed content, and the Distribution Peering
Requirements for CDI, which is responsible for distributing content
between a CDN and the elements that it, are detailed in [8], [9].
1.1 Conventions used in this document
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 [4].
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2. Terminology
This section introduces new terminology not already defined in < RFC
2975 [2], RFC 2977 [3], or [5]
CDN Service: An action that is directly or indirectly related to the
act of moving content from publisher to consumer.
Customer: A billable entity (typically a publisher, client or peered
CDN) that agrees to exchange compensation for a CDN Service.
Entitlement: A right to access a given CDN Service or content object
typically provided to a customer by a provider.
Flat Rate: Indicates there is no limit on the amount of CDN Service
that a customer can consume during a Period.
Percentile: Indicates that a CDN Service will be billed at a rate
that is based on a multiplier (Usage Rate) times the Usage during
the Period.
Period: The duration for which the Usage counter or Entitlement is
active.
Provider: An entity that offers a CDN Service in exchange for
Compensation.
Unit Of Measure (UOM): Indicates how Usage should be tracked (i.e.
minutes, seconds, bytes, etc).
Usage: A counter that measures the access or use of a CDN Service by
the Customer.
Usage Rate: A per-unit cost associated with the Usage of a CDN
Service.
Pricing / Rating Tiers: Indicates the existence of a schedule against
which Usage of a given CDN Service is tracked and billed.
Work: This is the definition of an activity in which a CDN partakes
by providing a specific function, role or service. These
activities are restricted to only those which involve the
participation of peering entities outside the CDNs administrative
domain.
Tier: This is the conceptual enclosure of a specific function (such
as accounting, settlement, rating, billing, invoicing, payment,
provisioning etc) in the context of a layered / phased multi-
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function environment.
CDR (Content Detail Record): This is the digital entity which capture
the 'what', 'who', 'when', 'where', and 'how' of the work done.
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3. Overview of Accounting Peering System
The Accounting Peering system is responsible for the definition,
generation and exchange of usage / consumption data entities (CDRs)
which depict the activities and works performed, requested, and
completed between peering CDNs, and any component internetworking
with a CDN. These CDRs typically will contain 'what work was done',
'who did the work', 'when was the work done', 'how was the work
done', 'Resources Used' etc.
---------------------------------------------------------------------
* *
+---------------+ * * +---------------+
| Origin | * ==== ContentInjection =====> * | CDN X |
+---------------+ * <==== ContentRequest ======= * |...............|
* * | |
+---------------+ * <==== ContentDistribution ==> * |...............|
| Peering CDN | * <==== ContentRetrieve ======> * | |
+---------------+ * * |...............|
* * | |
+---------------+ * <==== ContentServiceDelivery= * | |
| Client | * =====ContentRequest =====> * | |
+ --------------+ * * +---------------+
* *
* *
Acct-CPG Acct-CPG
Figure 1: Accounting Peering System Components and Activities
---------------------------------------------------------------------
The above diagram (Figure 1) illustrates the architectural entities
which will internetwork with a CDN as well as the activities that
transpire between any two peering entities . Each activity is to be
considered as discrete accountable events in their own right. The
arrows indicate the parties and roles involved in each activity as
each activity has a source and destination role in the communications
exchange (note : the arrows do not indicate who is generating /
receiving the CDR )
The model above allows for complex chaining and sequencing of
activities which express the relationship of interoperations that a
typical CDN will encounter.
The core activities (as described above) that need to be accounted
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are ContentInjection, ContentDistribution, ContentRequest,
ContentRetrieval, and ContentServiceDelivery. The activities above
cannot span multiple internetworking hops.
Each independent piece of activity or work performed by/to a CDN,
can be transmitted and collected by any entity or instrumentation,
which implements the Accounting-Peering System Interface(Acct-CPG).
It is envisioned that each CDN would have an instrumentation platform
which would detect or be informed of the activities described above.
This platform or detection mechanism is not in-scope of Acct-CPG.
A transport protocol would be used to exchange CDRs between an entity
which generates a CDR, and an entity which receives a CDR.
Presumably, the entity which is capable of detecting the activity
will be the entity that generates the CDR to an entity interested in
receiving the CDR. The Acct-CPG interface will not specify which
entity can, must, or should implement the Acct-CPG interface.
Accounting systems in general will have to support the real-time
occurrence of the above mentioned activities. That is when the
activities do take place, the activity must be recorded and not lost.
Reliability of recording accountable events/activities is required or
otherwise the accounting infrastructure will be compromised. However
the Acct-CPG will not specify the mechanism to record the activities
that have occurred, but will solely impress upon the necessity of
reliability and integrity in the process of activity detection, and
recording.
The nature of certain activities may also span a segment of time from
activity initiation to completion. Acct-CPG systems shall be able to
generate interim, and composite CDRs of each discrete activity which
depict the passage of time and states of an activity. Thus, the
Acct-CPG interface shall be charged with the responsibility of
support for interim and composite CDRs, and support for real time
and/or offline/batch exchange of accountable works / activities.
The Accounting data entities (CDRs) may be used by other downstream
functional tiers such as Rating & Billing, Capacity Planning,
Performance & Monitoring Analysis, Payment systems, Account
Management, Settlement Systems etc. These downstream tiers are
considered out-of-scope, but the solution should not be incompatible
with this functionality
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4. Assumptions
Certain assumptions/expectations of the operating environment are
detailed below. Should any of the assumptions change, there may be
material implications on the requirements of the CDN-I Accounting
Peering (Acct-CPG) systems.
4.1 Firewalls
There are no firewalls between the path of the Accounting Peering
Systems. Peering CDN-I Accounting systems can establish a
communication channel between themselves provided they have the
appropriate and valid trust credentials.
4.2 CDR Generation & Reception
Any entity (network element or service element) can be a CDR
Generator and/or a CDR Receiver as long as the entity is 'CDN-I Acct-
CPG' enabled.
4.3 Storage Requirements
The CDN-I Accounting Peering requirements shall not place any
constraints or restrictions on the storage of CDRs. CDR Storage is
essentially out of scope. However, to provide fail-over and recovery
in the data exchange protocol, there most likely will be storage
implications for an entity to be considered 'CDN-I Accounting
Peering' enabled.
4.4 Authentication & Authorization
The CDN-I Accounting Peering requirements shall only exchange
Authentication & Authorization Messages to enable the exchange of
CDRs. The policies, and mechanisms which influence these
Authentication and Authorizations messages are to be provided and
maintained by an external functional component or process, and are to
be considered out-of-scope, except to the extent that it influences
the requirements of accounting data exchange.
4.5 Measurement / Metering Systems
Instrumentation (hard and/or soft) exists on the CDN-I network which
can detect, recognize, and inform an Accounting-Peering System when a
ContentInjection, ContentDistribution, ContentRequest,
ContentRetrieval, and ContentServiceDelivery act / event has taken
place.
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4.6 Inter-Domain Trust
All systems are conformant with the AAA Authentication and
Authorization Framework for Inter-Domain trust. Refer [1]
4.7 Proxy CDN-I Account-Peering systems
If Accounting-Peering (Acct-CPG) system communicate through
intermediate Acct-CPG systems, it is necessary that the CDR payload
is secure between the originator Acct-CPG and target Acct-CPG server.
The security requirement may be end-to-end security, CDR payload
integrity, confidentiality, replay protection, and non-repudiation.
Refer [1].
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5. Accounting 'Works'
The objective of this section is to define the requirement of a
scalable framework for depicting all the various acts / services /
'works' performed by any entity which internetworks with a CDN, and
which needs to be accounted. It is envisioned that a finite (core)
set of works will need to be defined so as to achieve initial
adoption and traction. Thereafter the framework must accommodate
expansion of acts / services / work in the CDN Internetworking
domain.
5.1 Introduction
An expression of 'work' performed consists of a collection/sequence
of attributes which consist of identifiers, measures, and counters.
The attributes serve to answer the who, what, where, and how of these
elements of usage or acts of consumption (CDRs).
For the CDN peering/interconnection scenario, it is important to
construct the expressions/acts of consumption such that there is no
dispute and ambiguity in meaning between parties producing and
receiving these expressions. In each act of consumption, there is a
minimum set of attributes in which an act/expression of consumption/
usage is considered "complete and indisputable" and therefore able to
be used by any downstream tiers (ex : rating and billing).
5.2 General Requirements
5.2.1 Framework
A framework which can accommodate the scalable definition of CDRs is
required. This framework shall be able to introduce new CDRs and
their associated schemas at a later time frame.
The framework must ensure that 'Context' of the CDR payload is
available to any party such that domains / scope of CDR and attribute
applicability / validity is defined. 'Context' will mean roles of
participating entities, domain, and scope. There shall be no
overloading of attribute meanings. Every measure and counter must
have have units, minima and maxima, and incrementals defined. Every
identifier must be persistent within a defined domain and time frame.
Decisions on in-band or out-of-band context embedding will be needed
and shall be defined in the framework. The framework shall support
self-description of the usage attributes.
This framework shall NOT define any actions, rules, constraints and
context with regards to the processing of CDRs.
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XML technology should be considered as a vehicle to achieve the above
framework. Other strategies can also be considered if the end-value
is achievable.
5.2.2 Form-Factor of CDRs
The representation and form-factor of the CDRs must also be
addressed. Binary based and character based form factors need to be
supported.
5.2.3 Timing Requirement of CDR exchange
Certain CDRTypes will have delivery requirements which meet timing
constraints. For each independent operating scenario and 'work'
(CDR) type, requirements on CDR transport exchange and timings need
to be assessed. It will be required to specify timing constraints
for certain CDR Types, and will be used by the data exchange protocol
during the channel setup phase.
5.2.4 Identifiers
An identifier is an attribute which associates a name convention to
an entity. Examples of identifies are OrganizationName, EndUserName,
Name of Movie, ContentID etc These identifiers can and do have
properties and characteristics such as persistence, scope & domain,
time-to-live etc. In the accounting context, these identifiers must
be resolvable, unambiguous, recoverable and unique in the applicable
domain.
5.2.5 Measures
Measures are attributes that help to describe 'how' a certain piece
of work was performed, delivered or consumed. Typical examples are
QoS, JitterDelay, etc. Measures need to be defined completely and
without ambiguity by defining known minima, maxima, unit of
increments etc. The definition of measures must remain persistent
and consistent within its scope and domain.
5.2.6 Counters
Counters are attributes that help to describe the quantity of
resources consumed by a singular accountable act / work. Typically
Counters must be defined by its units, minima and maxima and the
mathematical operations that are permissible on a counter.
5.2.7 Name Space Convention (Distributed,Domained,Global)
In a distributed environment, a domain consistent way of naming
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entities such as a customer, ContentID, ContentType etc is required,
so that any member participating in the CDN Internetworking
activities can be consistently identified. The scope / domain of
applicability of every identifier must be referenceable by any party
participating in the work represented by the specific CDR, and / or
by any party involved in the exchange of the specific CDR.
Likewise, the framework must also provision a Name Space mechanism
for naming a specific content within the federation. For example, a
specific movie or song might need to be named in the same way in all
of the different points of the federation, independently of the
domain that is delivering the specific content. This SHOULD follow a
standard that can be interpreted by every member of the federation.
5.2.8 Security Requirements
This document assumes that the solutions suggested within this
document will be compliant with the trust model given in RFC 2904
[1].
5.3 Core Works Requirements
This section defines those 'work' items that form the initial core
set of 'works' that must be supported by any 'CDN-I Accounting'
enabled entity. The objective here is to achieve consensus around a
set of accountable works which are deemed sufficiently important such
that its definition and support is warranted.
5.3.1 Introduction
For each of the accountable works defined below in the subsections,
the following must be defined :
5.3.1.1 List of Attributes
Each attribute must define its name, its meaning, whether it is a
required / optional / conditional attribute, its data type (int,
string, complex etc)
5.3.1.2 Encoding and Representation
The encoding and representation format of each attribute inside the
CDR must be defined.
5.3.1.3 Use Case Model
Generally describes the involved entities in the creation of the CDR.
The 'Context' of the CDR will most likely be defined here as well.
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5.3.1.4 Work Flow Model
Details the sequencing of events of the involved entities which
generates the CDR and where the CDR has to be sent.
5.3.1.5 Work State Model
Details the state transition diagram of the 'Work' by defining the
triggers and the state of work from inception to completion. The
'State' of Work may or may not be distributed across one or more
elements in the federation.
5.3.2 ContentInjection Work
This 'work' is the event(CDR) that represents the act of a Host
Origin Server which successfully 'injects' a piece of 'content' into
a CDN for further distribution. An example scenario is where a
Content Provider or a Publisher wishes to distribute content. The
Publisher typically transfer the relevant content to a CDN Service
Provider. This transaction is referred to as Injection.
---------------------------------------------------------------------
A logical representation of this CDR is as below :
| CDRType | TimeStamp | ContentID | ContentType | OriginID | CDN_ID |
ContentByteSize | State | ErrorCode |
Attribute Name | Type | Description
----------------------------------------------------------------------------
CDRType | String| Type of CDR (Value = ContentInjection)
TimeStamp | Long | Time of Content Injection transaction (Start/End)
ContentURI | String| Unique identifier for the injected content
ContentType | String| Type of Content (WebPage, Movie, Song etc)
Origin ID | String| Unique Identifier for Content Source
CDN_ID | String| Unique Identifier for CDN ServiceProvider
ContentByteSize | Long | Size of Content Injected in Bytes
State | String| State of Injection (start,complete,error)
ErrorCode | String| UnAuthorized,UnAuthenticated,TimeOut,etc</t>
Figure 2: Content Injection CDR
---------------------------------------------------------------------
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5.3.3 ContentDistribution Work
This 'work' is the event (CDR) that represents the act where a CDN
'distributes' the 'content' to another peering CDN.
---------------------------------------------------------------------
A logical representation of this CDR is as below :
| CDRType | TimeStamp | Content_ID | ContentType | CDNSrcID | CDNDestID|
| ContentByteSize | State | ErrorCode |
Attribute Name | Type | Description
----------------------------------------------------------------------------
CDRType | String| Type of CDR (Value = ContentDistribution)
TimeStamp | Long | Time of Content Distribution transaction (start/end)
ContentURI | String| Unique identifier of content to be distributed
ContentType | String| Type of Content (WebPage, Movie, Song etc)
CDNSrcID | String| Unique Identifier of src distributing content
CDNDestID | String| Unique Identifier of dest receiving content
ContentByteSize | Long | Size of Content distributed in Bytes
State | String| Distribution State (start,complete,error)
ErrorCode | String| UnAuthorized,UnAuthenticated,TimeOut,etc</t>
Figure 3: Content Distribution CDR
---------------------------------------------------------------------
5.3.4 ContentRequest Work
This transaction is the event (CDR) that represents the act where an
end-user (EU) request access to a specific Content.
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---------------------------------------------------------------------
A logical representation of this CDR is as below :
| CDRType | TimeStamp | ContentURI | ContentType | ContentByteSize |
| RequesterID | ReceiverID | State | ErrorCode |
Attribute Name | Type | Description
------------------------------------------------------------------------------
CDRType |String| Type of CDR (Value = ContentRequest)
TimeStamp | Long | Time of content request transaction (start/end)
ContentURI |String| Unique identifier for the content to be distributed
ContentType |String| Type of Content (WebPage, Movie, Song etc)
RequesterID |String| Unique Identifier for entity requesting the content
ReceiverID |String| Unique Identifier for entity receiving request
ContentByteSize |Long | Size of Content distributed in Bytes
State |String| State of Request (start,complete,error)
ErrorCode |String| UnAuthorized,UnAuthenticated,TimeOut,etc</t>
Figure 4: Content Request CDR
---------------------------------------------------------------------
5.3.5 ContentRetrieval Work
This transaction is the event (CDR) that represents the act where
when a Content Request 'Miss' occurs, the 'content' is retrieved
from the origin server and delivered to the element (CDN / cache)
where the miss occurred.
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---------------------------------------------------------------------
A logical representation of this CDR is as below :
| CDRType | TimeStamp | ContentURI | ContentType | ContentByteSize |
| Origin_ID | Receiver_ID | State | ErrorCode |
Attribute Name | Type | Description
----------------------------------------------------------------------------
CDRType |String | Type of CDR (Value = ContentRetrieval)
TimeStamp | Long | Time of Content Retrieval transaction (start/end)
ContentURI |String | Unique identifier for the retrieved content
ContentType |String | Type of Content (WebPage, Movie, Song etc)
Origin ID |String | Unique Identifier for Content Source
Receiver_ID |String | Unique Identifier for receiver of content retrieved
ContentByteSize | Long | Size of Content Injected in Bytes
State |String | State of Injection (start,complete,error)
ErrorCode |String | UnAuthorized,UnAuthenticated,TimeOut,etc</t>
Figure 5: Content Retrieval CDR
---------------------------------------------------------------------
5.3.6 ContentServiceDelivery Work
This transaction is the event (CDR) that represents the act where a
CDN delivers the Content requested to the entity which requested the
content.
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---------------------------------------------------------------------
A logical representation of this CDR is as below :
| CDRType | TimeStamp | ContentServiceURI | ContentServiceType |
| ContentByteSize | DelivererID | ReceiverID | State | ErrorCode |
Attribute Name | Type | Description
----------------------------------------------------------------------------
CDRType |String | Type of CDR (Value = Content/Service Delivery)
TimeStamp |Long | Time of Content Delivery transaction (start/end)
Content/ServiceURI |String | Unique identifier the delivered content/service
Content/ServiceType|String | Type of Content/Service (WebPage, Movie, Song etc)
DeliveryMode |String | mode of delivery (stream, filetransfer, http, etc)
DelivererID |String | Unique Identifier of entity delivering the content
ReceiverID |String | Unique Identifier for entity receiving the content
ContentByteSize |Long | Size of Content Injected in Bytes
State |String | State of Delivery (start,complete,error)
ErrorCode |String | UnAuthorized,UnAuthenticated,TimeOut,etc
Figure 6: Content Service Delivery CDR
---------------------------------------------------------------------
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6. Data Exchange Mechanism / Protocol
6.1 Introduction
This objective of this section is to develop the requirements of a
transport mechanism which shall be responsible for the transfer /
exchange of a 'Work/Activity' (CDR) from one entity to another
entity.
6.2 General Requirements
This section details some of the general requirements of a transport
protocol.
6.2.1 Separation of Exchange Protocol from CDR payload
The transfer protocol must be cleanly decoupled from the CDR payloads
that it will transfer.
6.2.2 Transfer Capability Negotiation
Support for push, pull and poll transfers modes need to be supported.
6.2.3 Singular, Batched, Flow, & RealTime Modes of Data Exchange
The transport protocol shall support batch, flow, and real-time modes
of exchange of CDR payloads. Support for multiple channels of
transport must exist to accommodate multiple varying throughput rate
requirements, and/or multiple exchange modes between the accounting
peering parties which occur at the same time. A specific transport
channel shall be able to exchange multiple CDRs of a singular
CDRType. That is, mixed CDRTypes within a singular channel is not
supported.
6.2.4 Efficient Encoding
6.2.5 Transfer Flow & Rate Control
The transfer protocol shall support flow control mechanisms to
achieve sustainable delivery throughput between the two data exchange
peers.
6.2.6 Guaranteed Delivery
It is to be assumed that all works that are to be accounted for MUST
never be lost. Therefore all transfer modes must achieve reliable
and guaranteed delivery of CDR payloads. Unless there is a
compelling case for an non-guaranteed delivery requirement, this
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assumption and requirement shall stand.
6.2.7 CDR Relationship Identifiers
CDR EventIdentifiers (unique) may be required if relationships exist
across a set of CDRs. Situations where interim CDRs are generated,
it is necessary to track the sequencing of a related set to ensure
completeness, detect errors, and the retransmission of CDRs. If
relationships of a set of CDR spans a distributed domain, then a
distributed numbering strategy must exist.
6.2.8 Protocol State Machines
Clear visualization of transport protocol state machines in the
sender and receiver must be developed.
6.2.9 Encryption
It is recommended that encryption works from other IETF standards be
leveraged to ensure data / CDR security.
6.3 Authorization and Authentication
Authorization and authentication mechanisms must exist in the data
exchange protocol to enable the initiation of data exchange. This
mechanism may be influenced by external (out-of-scope) policy and
control mechanisms / processes which precede the transfer / exchange
of CDRs.
6.4 CDR Receivers
Any entity that is 'CDN-I Accounting' enabled is eligible to receive
a CDR. To enable the delivery of CDRs, the CDR Receiver must contact
a CDR Generator and establish a channel. A channel must only be able
to transfer CDRs of a singular CDRType.
6.5 CDR Generators :
Only 1 CDR must be generated for a singular incidence of 'work'. Any
entity which is 'CDN-I Accounting' enabled, is eligible to generate
the CDR. The CDR Generator entity must be able to support the
delivery of a CDR stream to multiple recipients if a single channel
has been created between each recipient and the CDR Generator.
6.6 Fault-Tolerance
Fault Tolerance, fail-over, and recovery mechanism mechanisms are
required to insure against network failure, accounting peering
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component failure, packet loss, and/or device reboots.
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7. Further Issues
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8. Recommendations
[Editor's Note: This section is here only to record some ideas that
need to be discussed while this specification is being progressed.]
One means of accommodating these types of services is to build off of
the ongoing work of the IETF AAA working group [2]. 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.
Has hop-by-hop, as well as end-to-end encryption support.
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9. Conclusion
There is a considerable amount of work remaining in defining the
accounting requirements and relationships. As such, the authors
welcome additional input from interested parties.
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References
[1] "AAA Authorization Framework", August 2000, <ftp://ftp.isi.edu/
in-notes/rfc2904.txt>.
[2] "Introduction to Accounting Management", October 2000, <ftp://
ftp.isi.edu/in-notes/rfc2975.txt>.
[3] "Mobile IP Authentication, Authorization, and Accounting
Requirements", October 2000, <ftp://ftp.isi.edu/in-notes/
rfc2977.txt>.
[4] "Key words for use in RFCs to Indicate Requirement Levels",
March 1997, <ftp://ftp.isi.edu/in-notes/rfc2119.txt>.
[5] "A Model for Content Internetworking (CDI)", February 2002,
<http://www.ietf.org/internet-drafts/draft-ietf-cdi-model-
01.txt>.
[6] "Content Internetworking (CDI) Scenarios", February 2002,
<http://www.ietf.org/internet-drafts/draft-ietf-cdi-scenarios-
01.txt>.
[7] "Content Internetworking Architectural Overview", February 2002,
<http://www.ietf.org/internet-drafts/draft-ietf-cdi-
architecture-01.txt>.
[8] "Request-Routing Requirements for Content Internetworking",
February 2002, <http://www.ietf.org/internet-drafts/draft-ietf-
cdi-request-routing-reqs-00.txt>.
[9] "Distribution Requirements for Content Internetworking",
February 2002, <http://www.ietf.org/internet-drafts/draft-ietf-
cdi-distribution-reqs-00.txt>.
Authors' Addresses
Don Gilletti
CacheFlow, Inc.
551 Moffett Park Drive
Sunnyvale, CA 94089
USA
Phone: +1 408 543 0437
EMail: don@cacheflow.com
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Raj Nair
Cisco Systems
John Scharber
CacheFlow, Inc.
551 Moffett Park Drive
Sunnyvale, CA 94089
USA
EMail: john.scharber@cacheflow.com
Jay Guha
Apogee Networks
Park 80 West, Plaza II
Saddle Brook, NJ
USA
Phone: +1 201 368 8800
EMail: jayg@apogeenet.com
David Frascone
Blackstorm Networks
250 Cambridge Avenue, Suite 200
Palo Alto, CA 94306
USA
Phone: +1 972 524 6346
EMail: codemonkey@bstormnetworks.com
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Appendix A. Acknowledgments
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),
Gary Tomlinson (Entera), Lisa Amini (IBM) and Abhi Deskmukh (Apogee).
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