Network Working Group M. Day
Request for Comments: 3466 Cisco
Category: Informational B. Cain
Storigen
G. Tomlinson
Tomlinson Group
P. Rzewski
Media Publisher, Inc.
February 2003
A Model for Content Internetworking (CDI)
Status of this Memo
This memo provides information for the Internet community. It does
not specify an Internet standard of any kind. Distribution of this
memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract
Content (distribution) internetworking (CDI) is the technology for
interconnecting content networks, sometimes previously called
"content peering" or "CDN peering". A common vocabulary helps the
process of discussing such interconnection and interoperation. This
document introduces content networks and content internetworking, and
defines elements for such a common vocabulary.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Content Networks . . . . . . . . . . . . . . . . . . . . . . 2
2.1 Problem Description . . . . . . . . . . . . . . . . . 3
2.2 Caching Proxies. . . . . . . . . . . . . . . . . . . . 4
2.3 Server Farms . . . . . . . . . . . . . . . . . . . . . 5
2.4 Content Distribution Networks. . . . . . . . . . . . . 6
2.4.1 Historic Evolution of CDNs . . . . . . . . . . . 8
2.4.2 Describing CDN Value: Scale and Reach. . . . . . 8
3. Content Network Model Terms . . . . . . . . . . . . . . . . 9
4. Content Internetworking . . . . . . . . . . . . . . . . . . 12
5. Content Internetworking Model Terms . . . . . . . . . . . . 12
6. Security Considerations . . . . . . . . . . . . . . . . . . 15
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 15
8. Normative References . . . . . . . . . . . . . . . . . . . . 16
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9. Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 16
10. Full Copyright Statement . . . . . . . . . . . . . . . . . . 17
1. Introduction
Content networks are of increasing importance to the overall
architecture of the Web. This document presents a vocabulary for use
in developing technology for interconnecting content networks, or
"content internetworking".
The accepted name for the technology of interconnecting content
networks is "content internetworking". For historical reasons, we
abbreviate this term using the acronym CDI (from "content
distribution internetworking"). Earlier names relied on analogy with
peering and interconnection of IP networks; thus we had "content
peering" and "CDN peering". All of these other names are now
deprecated, and we have worked to establish consistent usage of
"content internetworking" and "CDI" throughout the documents of the
IETF CDI group.
The terminology in this document builds from the previous taxonomy of
web caching and replication in RFC 3040 [3]. In particular, we have
attempted to avoid the use of the common terms "proxies" or "caches"
in favor of more specific terms defined by that document, such as
"caching proxy".
Section 2 provides background on content networks. Section 3
introduces the terms used for elements of a content network and
explains how those terms are used. Section 4 provides additional
background on interconnecting content networks, following which
Section 5 introduces additional terms and explains how those
internetworking terms are used.
2. Content Networks
The past several years have seen the evolution of technologies
centered around "content". Protocols, appliances, and entire markets
have been created exclusively for the location, download, and usage
tracking of content. Some sample technologies in this area have
included web caching proxies, content management tools, intelligent
"web switches", and advanced log analysis tools.
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When used together, these tools form new types of networks, dubbed
"content networks". Whereas network infrastructures have
traditionally processed information at layers 1 through 3 of the OSI
stack, content networks include network infrastructure that exists in
layers 4 through 7. Whereas lower-layer network infrastructures
centered on the routing, forwarding, and switching of frames and
packets, content networks deal with the routing and forwarding of
requests and responses for content. The units of transported data in
content networks, such as images, movies, or songs, are often very
large and may span hundreds or thousands of packets.
Alternately, content networks can be seen as a new virtual overlay to
the OSI stack: a "content layer", to enable richer services that rely
on underlying elements from all 7 layers of the stack. Whereas
traditional applications, such as file transfer (FTP), relied on
underlying protocols such as TCP/IP for transport, overlay services
in content networks rely on layer 7 protocols such as HTTP or RTSP
for transport.
The proliferation of content networks and content networking
capabilities gives rise to interest in interconnecting content
networks and finding ways for distinct content networks to cooperate
for better overall service.
2.1 Problem Description
Content networks typically play some role in solving the "content
distribution problem". Abstractly, the goal in solving this problem
is to arrange a rendezvous between a content source at an origin
server and a content sink at a viewer's user agent. In the trivial
case, the rendezvous mechanism is that every user agent sends every
request directly to the origin server named in the host part of the
URL identifying the content.
As the audience for the content source grows, so do the demands on
the origin server. There are a variety of ways in which the trivial
system can be modified for better performance. The apparent single
logical server may in fact be implemented as a large "farm" of server
machines behind a switch. Both caching proxies and reverse caching
proxies can be deployed between the client and server, so that
requests can be satisfied by some cache instead of by the server.
For the sake of background, several sample content networks are
described in the following sections that each attempt to address this
problem.
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2.2 Caching Proxies
A type of content network that has been in use for several years is a
caching proxy deployment. Such a network might typically be employed
by an ISP for the benefit of users accessing the Internet, such as
through dial or cable modem.
In the interest of improving performance and reducing bandwidth
utilization, caching proxies are deployed close to the users. These
users are encouraged to send their web requests through the caches
rather than directly to origin servers, such as by configuring their
browsers to do so. When this configuration is properly done, the
user's entire browsing session goes through a specific caching proxy.
That caching proxy will therefore contain the "hot set" of all
Internet content being viewed by all of the users of that caching
proxy.
When a request is being handled at a caching proxy on behalf of a
user, other decisions may be made, such as:
o A provider that deploys caches in many geographically diverse
locations may also deploy regional parent caches to further
aggregate user requests and responses. This may provide
additional performance improvement and bandwidth savings. When
parents are included, this is known as hierarchical caching.
o Using rich parenting protocols, redundant parents may be deployed
such that a failure in a primary parent is detected and a backup
is used instead.
o Using similar parenting protocols, requests may be partitioned
such that requests for certain content domains are sent to a
specific primary parent. This can help to maximize the efficient
use of caching proxy resources.
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The following diagram depicts a hierarchical cache deployment as
described above:
^ ^
| | requests to
| | origin servers
| |
-------- --------
|parent| |parent|
|cache | |cache |
|proxy | |proxy |
-------- --------
^ ^
requests for \ / requests for
foo.com \ / bar.com
content \ / content
\ /
------- ------- ------- -------
|edge | |edge | |edge | |edge |
|cache| |cache| |cache| |cache|
|proxy| |proxy| |proxy| |proxy|
------- ------- ------- -------
^
| all content
| requests
| for this
| client
|
--------
|client|
--------
Note that this diagram shows only one possible configuration, but
many others are also useful. In particular, the client may be able
to communicate directly with multiple caching proxies. RFC 3040 [3]
contains additional examples of how multiple caching proxies may be
used.
2.3 Server Farms
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
so-called "intelligent" or "content" switch (i.e., one that uses
information in OSI layers 4-7). The switch examines content requests
and dispatches them among a (potentially large) group of servers.
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Some of the goals of a server farm include:
o Creating the impression that the group of servers is actually a
single origin site.
o Load-balancing of requests across all servers in the group.
o Automatic routing of requests away from servers that fail.
o Routing all requests for a particular user agent's session to the
same server, in order to preserve session state.
The following diagram depicts a simple server farm deployment:
--------- --------- --------- ---------
|content| |content| |content| |content|
|server | |server | |server | |server |
| | | | | | | |
--------- --------- --------- ---------
^ ^
request from \ / request from
client A \ / client B
\ /
-------------
| L4-L7 |
| switch |
-------------
^ ^
/ \
/ \
/ \
request from request from
client A client B
A similar style of content network (that is, deployed close to
servers) may be constructed with surrogates [3] instead of a switch.
2.4 Content Distribution Networks
Both hierarchical caching and server farms are useful techniques, but
have limits. Server farms can improve the scalability of the origin
server. However, since the multiple servers and other elements are
typically deployed near the origin server, they do little to improve
performance problems that are due to network congestion. Caching
proxies can improve performance problems due to network congestion
(since they are situated near the clients) but they cache objects
based on client demand. Caching based on client demand performs
poorly if the requests for a given object, while numerous in
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aggregate, are spread thinly among many different caching proxies.
(In the worst case, an object could be requested n times via n
distinct caching proxies, causing n distinct requests to the origin
server -- or exactly the same behavior that would occur without any
caching proxies in place.)
Thus, a content provider with a popular content source can find that
it has to invest in large server farms, load balancing, and high-
bandwidth connections to keep up with demand. Even with those
investments, the user experience may still be relatively poor due to
congestion in the network as a whole.
To address these limitations, another type of content network that
has been deployed in increasing numbers in recent years is the CDN
(Content Distribution Network or Content Delivery Network). A CDN
essentially moves server-farm-like configurations out into network
locations more typically occupied by caching proxies. A CDN has
multiple replicas of each content item being hosted. A request from
a browser for a single content item is directed to a "good" replica,
where "good" usually means that the item is served to the client
quickly compared to the time it would take fetch it from the origin
server, with appropriate integrity and consistency. Static
information about geographic locations and network connectivity is
usually not sufficient to do a good job of choosing a replica.
Instead, a CDN typically incorporates dynamic information about
network conditions and load on the replicas, directing requests so as
to balance the load.
Compared to using servers and surrogates in a single data center, a
CDN is a relatively complex system encompassing multiple points of
presence, in locations that may be geographically far apart.
Operating a CDN is not easy for a content provider, since a content
provider wants to focus its resources on developing high-value
content, not on managing network infrastructure. Instead, a more
typical arrangement is that a network service provider builds and
operates a CDN, offering a content distribution service to a number
of content providers.
A CDN enables a service provider to act on behalf of the content
provider to deliver copies of origin server content to clients from
multiple diverse locations. The increase in number and diversity of
location is intended to improve download times and thus improve the
user experience. A CDN has some combination of a content-delivery
infrastructure, a request-routing infrastructure, a distribution
infrastructure, and an accounting infrastructure. The content-
delivery infrastructure consists of a set of "surrogate" servers [3]
that deliver copies of content to sets of users. The request-routing
infrastructure consists of mechanisms that move a client toward a
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rendezvous with a surrogate. The distribution infrastructure
consists of mechanisms that move content from the origin server to
the surrogates. Finally, the accounting infrastructure tracks and
collects data on request-routing, distribution, and delivery
functions within the CDN.
The following diagram depicts a simple CDN as described above:
---------- ----------
|request-| |request-|
|routing | |routing |
| system | | system |
---------- ----------
^ |
(1) client's | | (2) response
content | | indicating
request | | location of -----------
| | content |surrogate|
| | -----------
----------- | |
|surrogate| | | -----------
----------- | | |surrogate|
| | -----------
| | ^
| v / (3) client opens
client--- connection to
retrieve content
2.4.1 Historic Evolution of CDNs
The first important use of CDNs was for the distribution of heavily-
requested graphic files (such as GIF files on the home pages of
popular servers). However, both in principle and increasingly in
practice, a CDN can support the delivery of any digital content --
including various forms of streaming media. For a streaming media
CDN (or media distribution network or MDN), the surrogates may be
operating as splitters (serving out multiple copies of a stream).
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
are still intended to apply to the interconnection of content
networks that are distributing streaming media.
2.4.2 Describing CDN Value: Scale and Reach
There are two fundamental elements that give a CDN value: outsourcing
infrastructure and improved content delivery. A CDN allows multiple
surrogates to act on behalf of an origin server, therefore removing
the delivery of content from a centralized site to multiple and
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(usually) highly distributed sites. We refer to increased aggregate
infrastructure size as "scale". In addition, a CDN can be
constructed with copies of content near to end users, overcoming
issues of network size, network congestion, and network failures. We
refer to increased diversity of content locations as "reach".
In a typical (non-internetworked) CDN, a single service provider
operates the request-routers, the surrogates, and the content
distributors. In addition, that service provider establishes
(business) relationships with content publishers and acts on behalf
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
and its reach.
3. Content Network Model Terms
This section consists of the definitions of a number of terms used to
refer to roles, participants, and objects involved in content
networks. Although the following uses many terms that are based on
those used in RFC 2616 [1] or RFC 3040 [3], there is no necessary
connection to HTTP or web caching technology. Content
internetworking and this vocabulary are applicable to other protocols
and styles of content delivery.
Phrases in upper-case refer to other defined terms.
ACCOUNTING
Measurement and recording of DISTRIBUTION and DELIVERY activities,
especially when the information recorded is ultimately used as a
basis for the subsequent transfer of money, goods, or obligations.
ACCOUNTING SYSTEM
A collection of CONTENT NETWORK ELEMENTS that supports ACCOUNTING
for a single CONTENT NETWORK.
AUTHORITATIVE REQUEST-ROUTING SYSTEM
The REQUEST-ROUTING SYSTEM that is the correct/final authority for
a particular item of CONTENT.
CDN
Content Delivery Network or Content Distribution Network. A type
of CONTENT NETWORK in which the CONTENT NETWORK ELEMENTS are
arranged for more effective delivery of CONTENT to CLIENTS.
Typically a CDN consists of a REQUEST-ROUTING SYSTEM, SURROGATES,
a DISTRIBUTION SYSTEM, and an ACCOUNTING SYSTEM.
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CLIENT
A program that sends CONTENT REQUESTS and receives corresponding
CONTENT RESPONSES. (Note: this is similar to the definition in
RFC 2616 [1] but we do not require establishment of a connection.)
CONTENT
Any form of digital data, CONTENT approximately corresponds to
what is referred to as an "entity" in RFC 2616 [1]. One important
form of CONTENT with additional constraints on DISTRIBUTION and
DELIVERY is CONTINUOUS MEDIA.
CONTENT NETWORK
An arrangement of CONTENT NETWORK ELEMENTS, controlled by a common
management in some fashion.
CONTENT NETWORK ELEMENT
A network device that performs at least some of its processing by
examining CONTENT-related parts of network messages. In IP-based
networks, a CONTENT NETWORK ELEMENT is a device whose processing
depends on examining information contained in IP packet bodies;
network elements (as defined in RFC 3040) examine only the header
of an IP packet. Note that many CONTENT NETWORK ELEMENTS do not
examine or even see individual IP packets, instead receiving the
body of one or more packets assembled into a message of some
higher-level protocol.
CONTENT REQUEST
A message identifying a particular item of CONTENT to be
delivered.
CONTENT RESPONSE
A message containing a particular item of CONTENT, identified in a
previous CONTENT REQUEST.
CONTENT SIGNAL
A message delivered through a DISTRIBUTION SYSTEM that specifies
information about an item of CONTENT. For example, a CONTENT
SIGNAL can indicate that the ORIGIN has a new version of some
piece of CONTENT.
CONTINUOUS MEDIA
CONTENT where there is a timing relationship between source and
sink; that is, the sink must reproduce the timing relationship
that existed at the source. The most common examples of
CONTINUOUS MEDIA are audio and motion video. CONTINUOUS MEDIA can
be real-time (interactive), where there is a "tight" timing
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relationship between source and sink, or streaming (playback),
where the relationship is less strict. [Note: This definition is
essentially identical to the definition of continuous media in
[2]]
DELIVERY
The activity of providing a PUBLISHER's CONTENT, via CONTENT
RESPONSES, to a CLIENT. Contrast with DISTRIBUTION and REQUEST-
ROUTING.
DISTRIBUTION
The activity of moving a PUBLISHER's CONTENT from its ORIGIN to
one or more SURROGATEs. DISTRIBUTION can happen either in
anticipation of a SURROGATE receiving a REQUEST (pre-positioning)
or in response to a SURROGATE receiving a REQUEST (fetching on
demand). Contrast with DELIVERY and REQUEST-ROUTING.
DISTRIBUTION SYSTEM
A collection of CONTENT NETWORK ELEMENTS that support DISTRIBUTION
for a single CONTENT NETWORK. The DISTRIBUTION SYSTEM also
propagates CONTENT SIGNALs.
ORIGIN
The point at which CONTENT first enters a DISTRIBUTION SYSTEM.
The ORIGIN for any item of CONTENT is the server or set of servers
at the "core" of the distribution, holding the "master" or
"authoritative" copy of that CONTENT. (Note: We believe this
definition is compatible with that for "origin server" in RFC 2616
[1] but includes additional constraints useful for CDI.)
PUBLISHER
The party that ultimately controls the CONTENT and its
distribution.
REACHABLE SURROGATES
The collection of SURROGATES that can be contacted via a
particular DISTRIBUTION SYSTEM or REQUEST-ROUTING SYSTEM.
REQUEST-ROUTING
The activity of steering or directing a CONTENT REQUEST from a
USER AGENT to a suitable SURROGATE.
REQUEST-ROUTING SYSTEM
A collection of CONTENT NETWORK ELEMENTS that support REQUEST-
ROUTING for a single CONTENT NETWORK.
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SERVER
A program that accepts CONTENT REQUESTS and services them by
sending back CONTENT RESPONSES. Any given program may be capable
of being both a client and a server; our use of these terms refers
only to the role being performed by the program. [Note: this is
adapted from a similar definition in RFC 2616 [1].]
SURROGATE
A delivery server, other than the ORIGIN. Receives a CONTENT
REQUEST and delivers the corresponding CONTENT RESPONSE. [Note:
this is a different definition from that in RFC 3040 [3], which
appears overly elaborate for our purposes. A "CDI surrogate" is
always an "RFC 3040 surrogate"; we are not sure if the reverse is
true.]
USER AGENT
The CLIENT which initiates a REQUEST. These are often browsers,
editors, spiders (web-traversing robots), or other end user tools.
[Note: this definition is identical to the one in RFC 2616 [1].]
4. Content Internetworking
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
cost of equipment, the space available for deploying equipment,
and/or the demand for that scale/reach of infrastructure. Sometimes
a particular audience is tied to a single service provider or a small
set of providers by constraints of technology, economics, or law.
Other times, a network provider may be able to manage surrogates and
a distribution system, but may have no direct relationship with
content providers. Such a provider wants to have a means of
affiliating their delivery and distribution infrastructure with other
parties who have content to distribute.
Content internetworking allows different content networks to share
resources so as to provide larger scale and/or reach to each
participant than they could otherwise achieve. By using commonly
defined protocols for content internetworking, each content network
can treat neighboring content networks as "black boxes", allowing
them to hide internal details from each other.
5. Content Internetworking Model Terms
This section consists of the definitions of a number of terms used to
refer to roles, participants, and objects involved in internetworking
content networks. The purpose of this section is to identify common
terms and provide short definitions.
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ACCOUNTING INTERNETWORKING
Interconnection of two or more ACCOUNTING SYSTEMS so as to enable
the exchange of information between them. The form of ACCOUNTING
INTERNETWORKING required may depend on the nature of the
NEGOTIATED RELATIONSHIP between the peering parties -- in
particular, on the value of the economic exchanges anticipated.
ADVERTISEMENT
Information about resources available to other CONTENT NETWORKS,
exchanged via CONTENT INTERNETWORKING GATEWAYS. Types of
ADVERTISEMENT include AREA ADVERTISEMENTS, CONTENT ADVERTISEMENTS,
and DISTRIBUTION ADVERTISEMENTS.
AREA ADVERTISEMENT
ADVERTISEMENT from a CONTENT NETWORK's REQUEST-ROUTING SYSTEM
about aspects of topology, geography and performance of a CONTENT
NETWORK. Contrast with CONTENT ADVERTISEMENT, DISTRIBUTION
ADVERTISEMENT.
BILLING ORGANIZATION
An entity that operates an ACCOUNTING SYSTEM to support billing
within a NEGOTIATED RELATIONSHIP with a PUBLISHER.
CONTENT ADVERTISEMENT
ADVERTISEMENT from a CONTENT NETWORK's REQUEST-ROUTING SYSTEM
about the availability of one or more collections of CONTENT on a
CONTENT NETWORK. Contrast with AREA ADVERTISEMENT, DISTRIBUTION
ADVERTISEMENT
CONTENT DESTINATION
A CONTENT NETWORK or DISTRIBUTION SYSTEM that is accepting CONTENT
from another such network or system. Contrast with CONTENT
SOURCE.
CONTENT INTERNETWORKING GATEWAY (CIG)
An identifiable element or system through which a CONTENT NETWORK
can be interconnected with others. A CIG may be the point of
contact for DISTRIBUTION INTERNETWORKING, REQUEST-ROUTING
INTERNETWORKING, and/or ACCOUNTING INTERNETWORKING, and thus may
incorporate some or all of the corresponding systems for the
CONTENT NETWORK.
CONTENT REPLICATION
The movement of CONTENT from a CONTENT SOURCE to a CONTENT
DESTINATION. Note that this is specifically the movement of
CONTENT from one network to another. There may be similar or
different mechanisms that move CONTENT around within a single
network's DISTRIBUTION SYSTEM.
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CONTENT SOURCE
A CONTENT NETWORK or DISTRIBUTION SYSTEM that is distributing
CONTENT to another such network or system. Contrast with CONTENT
DESTINATION.
DISTRIBUTION ADVERTISEMENT
An ADVERTISEMENT from a CONTENT NETWORK's DISTRIBUTION SYSTEM to
potential CONTENT SOURCES, describing the capabilities of one or
more CONTENT DESTINATIONS. Contrast with AREA ADVERTISEMENT,
CONTENT ADVERTISEMENT.
DISTRIBUTION INTERNETWORKING
Interconnection of two or more DISTRIBUTION SYSTEMS so as to
propagate CONTENT SIGNALS and copies of CONTENT to groups of
SURROGATES.
ENLISTED
Describes a CONTENT NETWORK that, as part of a NEGOTIATED
RELATIONSHIP, has accepted a DISTRIBUTION task from another
CONTENT NETWORK, has agreed to perform REQUEST-ROUTING on behalf
of another CONTENT NETWORK, or has agreed to provide ACCOUNTING
data to another CONTENT NETWORK. Contrast with ORIGINATING.
INJECTION
A "send-only" form of DISTRIBUTION INTERNETWORKING that takes
place from an ORIGIN to a CONTENT DESTINATION.
INTER-
Describes activity that involves more than one CONTENT NETWORK
(e.g., INTER-CDN). Contrast with INTRA-.
INTRA-
Describes activity within a single CONTENT NETWORK (e.g., INTRA-
CDN). Contrast with INTER-.
NEGOTIATED RELATIONSHIP
A relationship whose terms and conditions are partially or
completely established outside the context of CONTENT NETWORK
internetworking protocols.
ORIGINATING
Describes a CONTENT NETWORK that, as part of a NEGOTIATED
RELATIONSHIP, submits a DISTRIBUTION task to another CONTENT
NETWORK, asks another CONTENT NETWORK to perform REQUEST-ROUTING
on its behalf, or asks another CONTENT NETWORK to provide
ACCOUNTING data. Contrast with ENLISTED.
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REMOTE CONTENT NETWORK
A CONTENT NETWORK able to deliver CONTENT for a particular REQUEST
that is not the AUTHORITATIVE REQUEST-ROUTING SYSTEM for that
REQUEST.
REQUEST-ROUTING INTERNETWORKING
Interconnection of two or more REQUEST-ROUTING SYSTEMS so as to
increase the number of REACHABLE SURROGATES for at least one of
the interconnected systems.
6. Security Considerations
This document defines terminology and concepts for content
internetworking. The terminology itself does not introduce any
security-related issues. The implementation of content
internetworking concepts does raise some security-related issues,
which we identify in broad categories below. Other CDI documents
will address their specific security-related issues in more detail.
Secure relationship establishment: CONTENT INTERNETWORKING GATEWAYS
must ensure that CONTENT NETWORKS are internetworking only with other
CONTENT NETWORKS as intended. It must be possible to prevent
unauthorized internetworking or spoofing of another CONTENT NETWORK's
identity.
Secure content transfer: CONTENT INTERNETWORKING GATEWAYS must
support CONTENT NETWORK mechanisms that ensure both the integrity of
CONTENT and the integrity of both DISTRIBUTION and DELIVERY, even
when both ORIGINATING and ENLISTED networks are involved. CONTENT
INTERNETWORKING GATEWAYS must allow for mechanisms to prevent theft
or corruption of CONTENT.
Secure meta-content transfer: CONTENT INTERNETWORKING GATEWAYS must
support the movement of accurate, reliable, auditable ACCOUNTING
information between CONTENT NETWORKS. CONTENT INTERNETWORKING
GATEWAYS must allow for mechanisms to prevent the diversion or
corruption of ACCOUNTING data and similar meta-content.
7. Acknowledgements
The authors acknowledge the contributions and comments of Fred
Douglis (AT&T), Don Gilletti (CacheFlow), Markus Hoffmann (Lucent),
Barron Housel (Cisco), Barbara Liskov (Cisco), John Martin (Network
Appliance), Nalin Mistry (Nortel Networks) Raj Nair (Cisco), Hilarie
Orman (Volera), Doug Potter (Cisco), and Oliver Spatscheck (AT&T).
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8. Normative References
[1] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., Masinter, L.,
Leach, P. and T. Berners-Lee, "Hypertext Transfer Protocol --
HTTP/1.1", RFC 2616, June 1999.
[2] Schulzrinne, H., Rao, A. and R. Lanphier, "Real Time Streaming
Protocol", RFC 2326, April 1998.
[3] Cooper, I., Melve, I. and G. Tomlinson, "Internet Web
Replication and Caching Taxonomy", RFC 3040, June 2000.
9. Authors' Addresses
Mark Stuart Day
Cisco Systems
1414 Massachusetts Avenue
Boxborough, MA 01719
US
Phone: +1 978 936 1089
EMail: mday@alum.mit.edu
Brad Cain
Storigen Systems
650 Suffolk Street
Lowell, MA 01854
US
Phone: +1 978 323 4454
EMail: bcain@storigen.com
Gary Tomlinson
Tomlinson Group
14324 227th Ave NE
Woodinville, WA 98072
Phone: +1 425 503 0881
EMail: gary@tomlinsongroup.net
Phil Rzewski
30 Jennifer Place
San Francisco, CA 94107
US
Phone: +1 650 303 3790
EMail: philrz@yahoo.com
Day, et al. Informational [Page 16]
RFC 3466 A Model for Content Internetworking (CDI) February 2003
10. Full Copyright Statement
Copyright (C) The Internet Society (2003). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Acknowledgement
Funding for the RFC Editor function is currently provided by the
Internet Society.
Day, et al. Informational [Page 17]