draft-ietf-cdi-model-02.txt   rfc3466.txt 
Network Working Group M. Day Network Working Group M. Day
Internet-Draft Cisco Request for Comments: 3466 Cisco
Expires: November 1, 2002 B. Cain Category: Informational B. Cain
Storigen Storigen
G. Tomlinson G. Tomlinson
CacheFlow Tomlinson Group
P. Rzewski P. Rzewski
Inktomi Media Publisher, Inc.
May 3, 2002 February 2003
A Model for Content Internetworking (CDI) A Model for Content Internetworking (CDI)
draft-ietf-cdi-model-02.txt
Status of this Memo Status of this Memo
This document is an Internet-Draft and is in full conformance with This memo provides information for the Internet community. It does
all provisions of Section 10 of RFC2026. not specify an Internet standard of any kind. Distribution of this
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This Internet-Draft will expire on November 1, 2002.
Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2002). All Rights Reserved. Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract Abstract
Content [distribution] internetworking (CDI) is the technology for Content (distribution) internetworking (CDI) is the technology for
interconnecting content networks, sometimes previously called interconnecting content networks, sometimes previously called
"content peering" or "CDN peering." A common vocabulary helps the "content peering" or "CDN peering". A common vocabulary helps the
process of discussing such interconnection and interoperation. This process of discussing such interconnection and interoperation. This
document introduces content networks and content internetworking, and document introduces content networks and content internetworking, and
defines elements for such a common vocabulary. defines elements for such a common vocabulary.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Content Networks . . . . . . . . . . . . . . . . . . . . . . 4 2. Content Networks . . . . . . . . . . . . . . . . . . . . . . 2
2.1 Problem Description . . . . . . . . . . . . . . . . . . . . 4 2.1 Problem Description . . . . . . . . . . . . . . . . . 3
2.2 Caching Proxies . . . . . . . . . . . . . . . . . . . . . . 5 2.2 Caching Proxies. . . . . . . . . . . . . . . . . . . . 4
2.3 Server Farms . . . . . . . . . . . . . . . . . . . . . . . . 6 2.3 Server Farms . . . . . . . . . . . . . . . . . . . . . 5
2.4 Content Distribution Networks . . . . . . . . . . . . . . . 7 2.4 Content Distribution Networks. . . . . . . . . . . . . 6
2.4.1 Historic Evolution of CDNs . . . . . . . . . . . . . . . . . 9 2.4.1 Historic Evolution of CDNs . . . . . . . . . . . 8
2.4.2 Describing CDN Value: Scale and Reach . . . . . . . . . . . 9 2.4.2 Describing CDN Value: Scale and Reach. . . . . . 8
3. Content Network Model Terms . . . . . . . . . . . . . . . . 11 3. Content Network Model Terms . . . . . . . . . . . . . . . . 9
4. Content Internetworking . . . . . . . . . . . . . . . . . . 14 4. Content Internetworking . . . . . . . . . . . . . . . . . . 12
5. Content Internetworking Model Terms . . . . . . . . . . . . 15 5. Content Internetworking Model Terms . . . . . . . . . . . . 12
6. Security Considerations . . . . . . . . . . . . . . . . . . 18 6. Security Considerations . . . . . . . . . . . . . . . . . . 15
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 19 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 15
References . . . . . . . . . . . . . . . . . . . . . . . . . 20 8. Normative References . . . . . . . . . . . . . . . . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 21 9. Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 16
Full Copyright Statement . . . . . . . . . . . . . . . . . . 22 10. Full Copyright Statement . . . . . . . . . . . . . . . . . . 17
1. Introduction 1. Introduction
Content networks are of increasing importance to the overall Content networks are of increasing importance to the overall
architecture of the Web. This document presents a vocabulary for use architecture of the Web. This document presents a vocabulary for use
in developing technology for interconnecting content networks, or in developing technology for interconnecting content networks, or
"content internetworking." "content internetworking".
The accepted name for the technology of interconnecting content The accepted name for the technology of interconnecting content
networks is "content internetworking." For historical reasons, we networks is "content internetworking". For historical reasons, we
abbreviate this term using the acronym CDI (from "content abbreviate this term using the acronym CDI (from "content
distribution internetworking"). Earlier names relied on analogy with distribution internetworking"). Earlier names relied on analogy with
peering and interconnection of IP networks; thus we had "content peering and interconnection of IP networks; thus we had "content
peering" and "CDN peering". All of these other names are now peering" and "CDN peering". All of these other names are now
deprecated, and we have worked to establish consistent usage of deprecated, and we have worked to establish consistent usage of
"content internetworking" and "CDI" throughout the drafts of the IETF "content internetworking" and "CDI" throughout the documents of the
CDI group. IETF CDI group.
The terminology in this document builds from the previous taxonomy of The terminology in this document builds from the previous taxonomy of
web caching and replication in RFC 3040 [3] . In particular, we have web caching and replication in RFC 3040 [3] . In particular, we have
attempted to avoid the use of the common terms "proxies" or "caches" attempted to avoid the use of the common terms "proxies" or "caches"
in favor of more specific terms defined by that document, such as in favor of more specific terms defined by that document, such as
"caching proxy." "caching proxy".
Section 2 provides background on content networks. Section 3 Section 2 provides background on content networks. Section 3
introduces the terms used for elements of a content network and introduces the terms used for elements of a content network and
explains how those terms are used. Section 4 provides additional explains how those terms are used. Section 4 provides additional
background on interconnecting content networks, following which background on interconnecting content networks, following which
Section 5 introduces additional terms and explains how those Section 5 introduces additional terms and explains how those
internetworking terms are used. internetworking terms are used.
[Note to RFC Editor: This entire paragraph may be deleted so as to
avoid references to internet-drafts in RFCs.] The IETF CDI effort has
produced a number of other documents related to content
internetworking. Other documents providing general information about
CDI are: "Content Internetworking Scenarios" [5], which enumerates
scenarios for content-internetworking-related interactions; "Content
Internetworking Architectural Overview" [4], which gives an overall
architecture of the elements for CDI; and "Known CDN Request-Routing
Mechanisms" [7], which summarizes known mechanisms for request-
routing. In addition, there are documents describing the
requirements for various aspects of CDI: "Request-Routing
Requirements for Content Internetworking" [8], "Distribution
Requirements for Content Internetworking" [9], and "Content
Internetworking (CDI) Authentication, Authorization, and Accounting
Requirements" [6]
2. Content Networks 2. Content Networks
The past several years have seen the evolution of technologies The past several years have seen the evolution of technologies
centered around "content." Protocols, appliances, and entire markets centered around "content". Protocols, appliances, and entire markets
have been created exclusively for the location, download, and usage have been created exclusively for the location, download, and usage
tracking of content. Some sample technologies in this area have tracking of content. Some sample technologies in this area have
included web caching proxies, content management tools, intelligent included web caching proxies, content management tools, intelligent
"web switches", and advanced log analysis tools. "web switches", and advanced log analysis tools.
When used together, these tools form new types of networks, dubbed When used together, these tools form new types of networks, dubbed
"content networks". Whereas network infrastructures have "content networks". Whereas network infrastructures have
traditionally processed information at layers 1 through 3 of the OSI traditionally processed information at layers 1 through 3 of the OSI
stack, content networks include network infrastructure that exists in stack, content networks include network infrastructure that exists in
layers 4 through 7. Whereas lower-layer network infrastructures layers 4 through 7. Whereas lower-layer network infrastructures
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Note that this diagram shows only one possible configuration, but Note that this diagram shows only one possible configuration, but
many others are also useful. In particular, the client may be able many others are also useful. In particular, the client may be able
to communicate directly with multiple caching proxies. RFC 3040 [3] to communicate directly with multiple caching proxies. RFC 3040 [3]
contains additional examples of how multiple caching proxies may be contains additional examples of how multiple caching proxies may be
used. used.
2.3 Server Farms 2.3 Server Farms
Another type of content network that has been in widespread use for Another type of content network that has been in widespread use for
several years is a server farm. A typical server farm makes use of a several years is a server farm. A typical server farm makes use of a
so-called "intelligent" or "content" switch (i.e. one that uses so-called "intelligent" or "content" switch (i.e., one that uses
information in OSI layers 4-7). The switch examines content requests information in OSI layers 4-7). The switch examines content requests
and dispatches them among a (potentially large) group of servers. and dispatches them among a (potentially large) group of servers.
Some of the goals of a server farm include: Some of the goals of a server farm include:
o Creating the impression that the group of servers is actually a o Creating the impression that the group of servers is actually a
single origin site. single origin site.
o Load-balancing of requests across all servers in the group. o Load-balancing of requests across all servers in the group.
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operating as splitters (serving out multiple copies of a stream). operating as splitters (serving out multiple copies of a stream).
The splitter function may be instead of, or in addition to, a role as The splitter function may be instead of, or in addition to, a role as
a caching proxy. However, the basic elements defined in this model a caching proxy. However, the basic elements defined in this model
are still intended to apply to the interconnection of content are still intended to apply to the interconnection of content
networks that are distributing streaming media. networks that are distributing streaming media.
2.4.2 Describing CDN Value: Scale and Reach 2.4.2 Describing CDN Value: Scale and Reach
There are two fundamental elements that give a CDN value: outsourcing There are two fundamental elements that give a CDN value: outsourcing
infrastructure and improved content delivery. A CDN allows multiple infrastructure and improved content delivery. A CDN allows multiple
surrogates to act on behalf of an orgin server, therefore removing surrogates to act on behalf of an origin server, therefore removing
the delivery of content from a centralized site to multiple and the delivery of content from a centralized site to multiple and
(usually) highly distributed sites. We refer to increased aggregate (usually) highly distributed sites. We refer to increased aggregate
infrastructure size as "scale." In addition, a CDN can be constructed infrastructure size as "scale". In addition, a CDN can be
with copies of content near to end users, overcoming issues of constructed with copies of content near to end users, overcoming
network size, network congestion, and network failures. We refer to issues of network size, network congestion, and network failures. We
increased diversity of content locations as "reach." refer to increased diversity of content locations as "reach".
In a typical (non-internetworked) CDN, a single service provider In a typical (non-internetworked) CDN, a single service provider
operates the request-routers, the surrogates, and the content operates the request-routers, the surrogates, and the content
distributors. In addition, that service provider establishes distributors. In addition, that service provider establishes
(business) relationships with content publishers and acts on behalf (business) relationships with content publishers and acts on behalf
of their origin sites to provide a distributed delivery system. The of their origin sites to provide a distributed delivery system. The
value of that CDN to a content provider is a combination of its scale value of that CDN to a content provider is a combination of its scale
and its reach. and its reach.
3. Content Network Model Terms 3. Content Network Model Terms
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CDN CDN
Content Delivery Network or Content Distribution Network. A type Content Delivery Network or Content Distribution Network. A type
of CONTENT NETWORK in which the CONTENT NETWORK ELEMENTS are of CONTENT NETWORK in which the CONTENT NETWORK ELEMENTS are
arranged for more effective delivery of CONTENT to CLIENTS. arranged for more effective delivery of CONTENT to CLIENTS.
Typically a CDN consists of a REQUEST-ROUTING SYSTEM, SURROGATES, Typically a CDN consists of a REQUEST-ROUTING SYSTEM, SURROGATES,
a DISTRIBUTION SYSTEM, and an ACCOUNTING SYSTEM. a DISTRIBUTION SYSTEM, and an ACCOUNTING SYSTEM.
CLIENT CLIENT
A program that sends CONTENT REQUESTS and receives corresponding A program that sends CONTENT REQUESTS and receives corresponding
CONTENT RESPONSES. [Note: this is similar to the definition in CONTENT RESPONSES. (Note: this is similar to the definition in
RFC 2616 [1] but we do not require establishment of a connection.] RFC 2616 [1] but we do not require establishment of a connection.)
CONTENT CONTENT
Any form of digital data, CONTENT approximately corresponds to Any form of digital data, CONTENT approximately corresponds to
what is referred to as an "entity" in RFC 2616 [1]. One important what is referred to as an "entity" in RFC 2616 [1]. One important
form of CONTENT with additional constraints on DISTRIBUTION and form of CONTENT with additional constraints on DISTRIBUTION and
DELIVERY is CONTINUOUS MEDIA. DELIVERY is CONTINUOUS MEDIA.
CONTENT NETWORK CONTENT NETWORK
An arrangement of CONTENT NETWORK ELEMENTS, controlled by a common An arrangement of CONTENT NETWORK ELEMENTS, controlled by a common
management in some fashion. management in some fashion.
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DISTRIBUTION SYSTEM DISTRIBUTION SYSTEM
A collection of CONTENT NETWORK ELEMENTS that support DISTRIBUTION A collection of CONTENT NETWORK ELEMENTS that support DISTRIBUTION
for a single CONTENT NETWORK. The DISTRIBUTION SYSTEM also for a single CONTENT NETWORK. The DISTRIBUTION SYSTEM also
propagates CONTENT SIGNALs. propagates CONTENT SIGNALs.
ORIGIN ORIGIN
The point at which CONTENT first enters a DISTRIBUTION SYSTEM. The point at which CONTENT first enters a DISTRIBUTION SYSTEM.
The ORIGIN for any item of CONTENT is the server or set of servers The ORIGIN for any item of CONTENT is the server or set of servers
at the "core" of the distribution, holding the "master" or at the "core" of the distribution, holding the "master" or
"authoritative" copy of that CONTENT. [Note: We believe this "authoritative" copy of that CONTENT. (Note: We believe this
definition is compatible with that for "origin server" in RFC 2616 definition is compatible with that for "origin server" in RFC 2616
[1] but includes additional constraints useful for CDI.] [1] but includes additional constraints useful for CDI.)
PUBLISHER PUBLISHER
The party that ultimately controls the CONTENT and its The party that ultimately controls the CONTENT and its
distribution. distribution.
REACHABLE SURROGATES REACHABLE SURROGATES
The collection of SURROGATES that can be contacted via a The collection of SURROGATES that can be contacted via a
particular DISTRIBUTION SYSTEM or REQUEST-ROUTING SYSTEM. particular DISTRIBUTION SYSTEM or REQUEST-ROUTING SYSTEM.
REQUEST-ROUTING REQUEST-ROUTING
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USER AGENT USER AGENT
The CLIENT which initiates a REQUEST. These are often browsers, The CLIENT which initiates a REQUEST. These are often browsers,
editors, spiders (web-traversing robots), or other end user tools. editors, spiders (web-traversing robots), or other end user tools.
[Note: this definition is identical to the one in RFC 2616 [1].] [Note: this definition is identical to the one in RFC 2616 [1].]
4. Content Internetworking 4. Content Internetworking
There are limits to how large any one network's scale and reach can There are limits to how large any one network's scale and reach can
be. Increasing either scale or reach is ultimately limited by the be. Increasing either scale or reach is ultimately limited by the
cost of equipment, the space available for deploying equipment, and/ cost of equipment, the space available for deploying equipment,
or the demand for that scale/reach of infrastructure. Sometimes a and/or the demand for that scale/reach of infrastructure. Sometimes
particular audience is tied to a single service provider or a small a particular audience is tied to a single service provider or a small
set of providers by constraints of technology, economics, or law. set of providers by constraints of technology, economics, or law.
Other times, a network provider may be able to manage surrogates and Other times, a network provider may be able to manage surrogates and
a distribution system, but may have no direct relationship with a distribution system, but may have no direct relationship with
content providers. Such a provider wants to have a means of content providers. Such a provider wants to have a means of
affiliating their delivery and distribution infrastructure with other affiliating their delivery and distribution infrastructure with other
parties who have content to distribute. parties who have content to distribute.
Content internetworking allows different content networks to share Content internetworking allows different content networks to share
resources so as to provide larger scale and/or reach to each resources so as to provide larger scale and/or reach to each
participant than they could otherwise achieve. By using commonly participant than they could otherwise achieve. By using commonly
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CONTENT NETWORK, has agreed to perform REQUEST-ROUTING on behalf CONTENT NETWORK, has agreed to perform REQUEST-ROUTING on behalf
of another CONTENT NETWORK, or has agreed to provide ACCOUNTING of another CONTENT NETWORK, or has agreed to provide ACCOUNTING
data to another CONTENT NETWORK. Contrast with ORIGINATING. data to another CONTENT NETWORK. Contrast with ORIGINATING.
INJECTION INJECTION
A "send-only" form of DISTRIBUTION INTERNETWORKING that takes A "send-only" form of DISTRIBUTION INTERNETWORKING that takes
place from an ORIGIN to a CONTENT DESTINATION. place from an ORIGIN to a CONTENT DESTINATION.
INTER- INTER-
Describes activity that involves more than one CONTENT NETWORK Describes activity that involves more than one CONTENT NETWORK
(e.g. INTER-CDN). Contrast with INTRA-. (e.g., INTER-CDN). Contrast with INTRA-.
INTRA- INTRA-
Describes activity within a single CONTENT NETWORK (e.g. INTRA- Describes activity within a single CONTENT NETWORK (e.g., INTRA-
CDN). Contrast with INTER-. CDN). Contrast with INTER-.
NEGOTIATED RELATIONSHIP NEGOTIATED RELATIONSHIP
A relationship whose terms and conditions are partially or A relationship whose terms and conditions are partially or
completely established outside the context of CONTENT NETWORK completely established outside the context of CONTENT NETWORK
internetworking protocols. internetworking protocols.
ORIGINATING ORIGINATING
Describes a CONTENT NETWORK that, as part of a NEGOTIATED Describes a CONTENT NETWORK that, as part of a NEGOTIATED
RELATIONSHIP, submits a DISTRIBUTION task to another CONTENT RELATIONSHIP, submits a DISTRIBUTION task to another CONTENT
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corruption of ACCOUNTING data and similar meta-content. corruption of ACCOUNTING data and similar meta-content.
7. Acknowledgements 7. Acknowledgements
The authors acknowledge the contributions and comments of Fred The authors acknowledge the contributions and comments of Fred
Douglis (AT&T), Don Gilletti (CacheFlow), Markus Hoffmann (Lucent), Douglis (AT&T), Don Gilletti (CacheFlow), Markus Hoffmann (Lucent),
Barron Housel (Cisco), Barbara Liskov (Cisco), John Martin (Network Barron Housel (Cisco), Barbara Liskov (Cisco), John Martin (Network
Appliance), Nalin Mistry (Nortel Networks) Raj Nair (Cisco), Hilarie Appliance), Nalin Mistry (Nortel Networks) Raj Nair (Cisco), Hilarie
Orman (Volera), Doug Potter (Cisco), and Oliver Spatscheck (AT&T). Orman (Volera), Doug Potter (Cisco), and Oliver Spatscheck (AT&T).
[Note to RFC Editor: The last normative reference is [3], all 8. Normative References
subsequent references starting with [4] can be deleted.]
References
[1] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., Masinter, L., [1] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., Masinter, L.,
Leach, P. and T. Berners-Lee, "Hypertext Transfer Protocol -- Leach, P. and T. Berners-Lee, "Hypertext Transfer Protocol --
HTTP/1.1", RFC 2616, June 1999, <http://www.rfc-editor.org/rfc/ HTTP/1.1", RFC 2616, June 1999.
rfc2616.txt>.
[2] Schulzrinne, H., Rao, A. and R. Lanphier, "Real Time Streaming [2] Schulzrinne, H., Rao, A. and R. Lanphier, "Real Time Streaming
Protocol", RFC 2326, April 1998, <http://www.rfc-editor.org/rfc/ Protocol", RFC 2326, April 1998.
rfc2326.txt>.
[3] Cooper, I., Melve, I. and G. Tomlinson, "Internet Web [3] Cooper, I., Melve, I. and G. Tomlinson, "Internet Web
Replication and Caching Taxonomy", RFC 3040, June 2000, <http:// Replication and Caching Taxonomy", RFC 3040, June 2000.
www.rfc-editor.org/rfc/rfc3040.txt>.
[4] Green, M., Cain, B., Tomlinson, G., Thomas, S. and P. Rzewskip,
"Content Internetworking Architectural Overview", draft-ietf-
cdi-architecture-00.txt (work in progress), February 2002,
<http://www.ietf.org/internet-drafts/draft-ietf-cdi-
architecture-00.txt>.
[5] Day, M., Gilletti, D. and P. Rzewski, "Content Internetworking
Scenarios", draft-ietf-cdi-scenarios-00.txt (work in progress),
February 2002, <http://www.ietf.org/internet-drafts/draft-ietf-
cdi-scenarios-00.txt>.
[6] Gilletti, D., Nair, R., Scharber, J. and J. Guha, "Content
Internetworking (CDI) Authentication, Authorization, and
Accounting Requirements", draft-ietf-cdi-aaa-reqs-00.txt (work
in progress), Februrary 2002, <http://www.ietf.org/internet-
drafts/draft-ietf-cdi-aaa-reqs-00.txt>.
[7] Barbir, A., Cain, B., Douglis, F., Green, M., Hoffmann, M.,
Nair, R., Potter, D. and O. Spatscheck, "Known CDN Request-
Routing Mechanisms", draft-ietf-cdi-known-request-routing-00.txt
(work in progress), February 2002, <http://www.ietf.org/
internet-drafts/draft-ietf-cdi-known-request-routing-00.txt>.
[8] Cain, B., Spatscheck, O., May, M. and A. Barbir, "Request-
Routing Requirements for Content Internetworking", draft-ietf-
cdi-request-routing-reqs-00.txt (work in progress), February
2002, <http://www.ietf.org/internet-drafts/draft-ietf-cdi-
request-routing-reqs-00.txt>.
[9] Amini, L., Spatscheck, O. and S. Thomas, "Distribution
Requirements for Content Internetworking", draft-ietf-cdi-
distribution-reqs-00.txt (work in progress), February 2002,
<http://www.ietf.org/internet-drafts/draft-ietf-cdi-
distribution-reqs-00.txt>.
Authors' Addresses 9. Authors' Addresses
Mark Stuart Day Mark Stuart Day
Cisco Systems Cisco Systems
1414 Massachusetts Avenue 1414 Massachusetts Avenue
Boxborough, MA 01719 Boxborough, MA 01719
US US
Phone: +1 978 936 1089 Phone: +1 978 936 1089
EMail: markday@cisco.com EMail: mday@alum.mit.edu
Brad Cain Brad Cain
Storigen Systems Storigen Systems
650 Suffolk Street 650 Suffolk Street
Lowell, MA 01854 Lowell, MA 01854
US US
Phone: +1 978-323-4454 Phone: +1 978 323 4454
EMail: bcain@storigen.com EMail: bcain@storigen.com
Gary Tomlinson Gary Tomlinson
CacheFlow, Inc. Tomlinson Group
12034 134th Ct. NE Suite 201 14324 227th Ave NE
Redmond, WA 98052 Woodinville, WA 98072
US
Phone: +1 425 820 3009 Phone: +1 425 503 0881
EMail: garyt@cacheflow.com EMail: gary@tomlinsongroup.net
Phil Rzewski Phil Rzewski
Inktomi 30 Jennifer Place
4100 East Third Avenue, MS FC2-4 San Francisco, CA 94107
Foster City, CA 94404
US US
Phone: +1 650 653 2487 Phone: +1 650 303 3790
EMail: philr@inktomi.com EMail: philrz@yahoo.com
Full Copyright Statement 10. Full Copyright Statement
Copyright (C) The Internet Society (2002). All Rights Reserved. Copyright (C) The Internet Society (2003). All Rights Reserved.
This document and translations of it may be copied and furnished to This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of Internet organizations, except as needed for the purpose of
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