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
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)
内容互联（CDI）模型
Status of this Memo
本备忘录的状况
This memo provides information for the Internet community. It does not specify an Internet standard of any kind. Distribution of this memo is unlimited.
本备忘录为互联网社区提供信息。它没有规定任何类型的互联网标准。本备忘录的分发不受限制。
Copyright Notice
版权公告
Copyright (C) The Internet Society (2003). All Rights Reserved.
版权所有（C）互联网协会（2003年）。版权所有。
Abstract
摘要
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.
内容（分发）互联（CDI）是用于互连内容网络的技术，有时以前称为“内容对等”或“CDN对等”。通用词汇表有助于讨论此类互连和互操作。本文档介绍内容网络和内容互联，并定义此类通用词汇表的元素。
Table of Contents
目录
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
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
9. Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 16
10. Full Copyright Statement . . . . . . . . . . . . . . . . . . 17
9. Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 16
10. Full Copyright Statement . . . . . . . . . . . . . . . . . . 17
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".
内容网络对于Web的整体架构越来越重要。本文档介绍了用于开发内容网络互连技术或“内容互联”技术的词汇表。
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.
互联内容网络技术的公认名称是“内容互联”。出于历史原因，我们使用首字母缩写CDI（来自“内容分发互联网络”）来缩写该术语。早期的名称依赖于IP网络的对等和互连；因此，我们有“内容对等”和“CDN对等”。所有这些其他名称现在都已弃用，我们已努力在IETF CDI组的所有文档中建立“内容互联”和“CDI”的一致使用。
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".
本文档中的术语源自RFC 3040[3]中以前的web缓存和复制分类法。特别是，我们试图避免使用通用术语“代理”或“缓存”，而使用该文档定义的更具体术语，如“缓存代理”。
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.
第2节介绍内容网络的背景。第3节介绍用于内容网络元素的术语，并解释如何使用这些术语。第4节提供了有关互联内容网络的其他背景知识，随后第5节介绍了其他术语，并解释了如何使用这些互联术语。
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.
过去几年，以“内容”为中心的技术不断发展。专门为内容的定位、下载和使用跟踪创建了协议、设备和整个市场。该领域的一些示例技术包括web缓存代理、内容管理工具、智能“web交换机”和高级日志分析工具。
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.
当这些工具一起使用时，就会形成新的网络类型，称为“内容网络”。传统上，网络基础设施在OSI堆栈的第1层到第3层处理信息，而内容网络包括存在于第4层到第7层的网络基础设施。下层网络基础设施以帧和数据包的路由、转发和交换为中心，而内容网络则处理内容请求和响应的路由和转发。内容网络中传输的数据单元（如图像、电影或歌曲）通常非常大，可能跨越数百或数千个数据包。
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.
或者，内容网络可以被视为OSI堆栈的一个新的虚拟覆盖层：“内容层”，以支持更丰富的服务，这些服务依赖于堆栈所有7层的底层元素。传统应用程序（如文件传输（FTP））依赖底层协议（如TCP/IP）进行传输，而内容网络中的覆盖服务则依赖第7层协议（如HTTP或RTSP）进行传输。
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.
内容网络和内容网络能力的激增引起了人们对互联内容网络和寻找不同内容网络合作的方式以获得更好的整体服务的兴趣。
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.
内容网络通常在解决“内容分发问题”方面发挥一定作用。抽象地说，解决这个问题的目标是在源服务器上的内容源和查看器的用户代理上的内容接收器之间安排集合。在一般情况下，集合机制是每个用户代理将每个请求直接发送到标识内容的URL的主机部分中指定的源服务器。
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.
随着内容源受众的增长，对源服务器的需求也在增长。可以通过多种方式修改平凡的系统以获得更好的性能。明显的单一逻辑服务器实际上可以实现为交换机后面的大型服务器机器“农场”。缓存代理和反向缓存代理都可以部署在客户端和服务器之间，因此可以通过某些缓存而不是服务器来满足请求。
For the sake of background, several sample content networks are described in the following sections that each attempt to address this problem.
出于背景考虑，以下各节介绍了几个示例内容网络，每个示例内容网络都试图解决此问题。
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.
一种已经使用多年的内容网络类型是缓存代理部署。ISP通常可以使用这样的网络，以便用户通过拨号或电缆调制解调器访问Internet。
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.
为了提高性能和降低带宽利用率，缓存代理部署在用户附近。我们鼓励这些用户通过缓存发送web请求，而不是直接发送到源服务器，例如通过配置浏览器这样做。正确完成此配置后，用户的整个浏览会话将通过特定的缓存代理。因此，该缓存代理将包含该缓存代理的所有用户正在查看的所有Internet内容的“热集”。
When a request is being handled at a caching proxy on behalf of a user, other decisions may be made, such as:
当代表用户在缓存代理上处理请求时，可能会做出其他决定，例如：
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 在许多地理位置不同的位置部署缓存的提供商也可以部署区域父缓存，以进一步聚合用户请求和响应。这可以提供额外的性能改进和带宽节约。当包含父级时，这称为分层缓存。
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 使用丰富的父级协议，可以部署冗余父级，以便检测主父级中的故障，并使用备份。
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.
o 使用类似的父级协议，可以对请求进行分区，以便将特定内容域的请求发送到特定的主父级。这有助于最大限度地高效利用缓存代理资源。
The following diagram depicts a hierarchical cache deployment as described above:
下图描述了如上所述的分层缓存部署：
^ ^
| | 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|
--------
^ ^
| | 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.
请注意，此图仅显示了一种可能的配置，但许多其他配置也很有用。特别地，客户端可以直接与多个缓存代理通信。RFC 3040[3]包含如何使用多个缓存代理的其他示例。
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.
另一种广泛使用了几年的内容网络类型是服务器场。典型的服务器场使用所谓的“智能”或“内容”交换机（即使用OSI第4-7层中的信息的交换机）。交换机检查内容请求，并在一组（可能很大的）服务器之间发送它们。
Some of the goals of a server farm include:
服务器场的一些目标包括：
o Creating the impression that the group of servers is actually a single origin site.
o 给人的印象是服务器组实际上是一个单一的源站点。
o Load-balancing of requests across all servers in the group.
o 跨组中所有服务器的请求负载平衡。
o Automatic routing of requests away from servers that fail.
o 从失败的服务器自动路由请求。
o Routing all requests for a particular user agent's session to the same server, in order to preserve session state.
o 将特定用户代理会话的所有请求路由到同一服务器，以保留会话状态。
The following diagram depicts a simple server farm deployment:
下图描述了一个简单的服务器场部署：
--------- --------- --------- ---------
|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
--------- --------- --------- ---------
|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.
类似类型的内容网络（即，部署在服务器附近）可以使用代理[3]而不是交换机来构建。
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
分层缓存和服务器场都是有用的技术，但都有局限性。服务器场可以提高源服务器的可伸缩性。但是，由于多个服务器和其他元素通常部署在源服务器附近，因此它们对改善由于网络拥塞而导致的性能问题几乎没有作用。缓存代理可以改善由于网络拥塞（因为它们位于客户端附近）而导致的性能问题，但它们会根据客户端需求缓存对象。如果对给定对象的请求太多，而
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.)
聚合，分散在许多不同的缓存代理之间。（在最坏的情况下，一个对象可能会通过n个不同的缓存代理被请求n次，从而导致对源服务器的n个不同请求——或者与没有缓存代理的情况下发生的行为完全相同。）
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.
因此，拥有流行内容源的内容提供商可能会发现，它必须投资于大型服务器场、负载平衡和高带宽连接，以满足需求。即使有了这些投资，由于整个网络的拥塞，用户体验可能仍然相对较差。
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.
为了解决这些限制，另一种近年来部署的内容网络类型是CDN（内容分发网络或内容交付网络）。CDN本质上是将类似服务器场的配置移动到网络位置，这些位置通常由缓存代理所占据。CDN具有托管的每个内容项的多个副本。浏览器对单个内容项的请求被定向到“良好”副本，其中“良好”通常意味着与从源服务器获取该项所需的时间相比，该项被快速提供给客户端，具有适当的完整性和一致性。关于地理位置和网络连接的静态信息通常不足以很好地选择复制副本。相反，CDN通常包含有关网络状况和副本上负载的动态信息，指导请求以平衡负载。
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.
与在单个数据中心中使用服务器和代理相比，CDN是一个相对复杂的系统，包含多个存在点，位置可能相距很远。运营CDN对内容提供商来说并不容易，因为内容提供商希望将其资源集中于开发高价值内容，而不是管理网络基础设施。相反，更典型的安排是网络服务提供商构建并操作CDN，向多个内容提供商提供内容分发服务。
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
CDN使服务提供商能够代表内容提供商向来自多个不同位置的客户端提供源服务器内容的副本。位置数量和多样性的增加旨在提高下载时间，从而改善用户体验。CDN由内容交付基础设施、请求路由基础设施、分发基础设施和记帐基础设施组成。内容交付基础架构由一组“代理”服务器[3]组成，这些服务器将内容副本交付给多组用户。请求路由基础结构由将客户端移动到客户端的机制组成
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.
和代理约会。分发基础结构由将内容从源服务器移动到代理服务器的机制组成。最后，会计基础设施跟踪并收集CDN内请求路由、分发和交付功能的数据。
The following diagram depicts a simple CDN as described above:
下图描述了如上所述的简单CDN：
---------- ----------
|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
---------- ----------
|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
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.
CDN的第一个重要用途是分发大量请求的图形文件（例如流行服务器主页上的GIF文件）。然而，无论是在原则上还是在实践中，CDN都可以支持任何数字内容的交付，包括各种形式的流媒体。对于流媒体CDN（或媒体分发网络或MDN），代理可以作为拆分器操作（提供流的多个副本）。拆分器功能可以代替缓存代理，也可以作为缓存代理的补充。然而，该模型中定义的基本元素仍然适用于分发流媒体的内容网络的互连。
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
有两个基本要素赋予CDN价值：外包基础设施和改进的内容交付。CDN允许多个代理服务器代表源服务器进行操作，因此可以将内容从集中式站点传递到多个服务器
(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".
（通常）高度分布的站点。我们将增加的基础设施总规模称为“规模”。此外，CDN可以使用靠近最终用户的内容副本构建，从而克服网络大小、网络拥塞和网络故障等问题。我们将内容位置的多样性增加称为“覆盖”。
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.
在典型（非互联）CDN中，单个服务提供商操作请求路由器、代理和内容分发服务器。此外，该服务提供商与内容发布商建立（业务）关系，并代表其原始站点提供分布式交付系统。CDN对内容提供商的价值是其规模和覆盖范围的组合。
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.
本节包括许多术语的定义，这些术语用于指内容网络中涉及的角色、参与者和对象。尽管以下使用了许多基于RFC 2616[1]或RFC 3040[3]中使用的术语，但没有必要连接到HTTP或web缓存技术。内容互联和此词汇表适用于其他协议和内容交付样式。
Phrases in upper-case refer to other defined terms.
大写的短语指其他定义的术语。
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.
分销和交付活动的会计计量和记录，尤其是当记录的信息最终用作后续资金、货物或义务转移的基础时。
ACCOUNTING SYSTEM A collection of CONTENT NETWORK ELEMENTS that supports ACCOUNTING for a single CONTENT NETWORK.
记帐系统支持单个内容网络记帐的内容网络元素的集合。
AUTHORITATIVE REQUEST-ROUTING SYSTEM The REQUEST-ROUTING SYSTEM that is the correct/final authority for a particular item of CONTENT.
权威请求路由系统是特定内容项的正确/最终权限的请求路由系统。
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.
CDN内容交付网络或内容分发网络。一种内容网络类型，其中内容网络元素被布置为更有效地向客户端传送内容。通常，CDN由请求路由系统、代理、分发系统和记帐系统组成。
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.)
客户端发送内容请求并接收相应内容响应的程序。（注：这与RFC 2616[1]中的定义类似，但我们不要求建立连接。）
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.
内容任何形式的数字数据，内容大致对应于RFC 2616[1]中所称的“实体”。对分发和交付有额外限制的内容的一种重要形式是连续媒体。
CONTENT NETWORK An arrangement of CONTENT NETWORK ELEMENTS, controlled by a common management in some fashion.
内容网络内容网络元素的一种安排，以某种方式由公共管理层控制。
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.
内容网元通过检查网络消息的内容相关部分来执行至少部分处理的网络设备。在基于IP的网络中，内容网元是其处理依赖于检查IP分组体中包含的信息的设备；网络元件（如RFC3040中所定义）仅检查IP数据包的报头。请注意，许多内容网络元素不检查甚至看不到单个IP数据包，而是接收一个或多个数据包的主体，这些数据包被组装成某个更高级协议的消息。
CONTENT REQUEST A message identifying a particular item of CONTENT to be delivered.
内容请求标识要交付的特定内容项的消息。
CONTENT RESPONSE A message containing a particular item of CONTENT, identified in a previous CONTENT REQUEST.
内容响应包含特定内容项的消息，在以前的内容请求中标识。
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.
内容信号通过分发系统发送的消息，指定有关内容项的信息。例如，内容信号可以指示源具有某一内容的新版本。
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
源和汇之间存在定时关系的连续媒体内容；也就是说，接收器必须重现源处存在的定时关系。连续媒体最常见的例子是音频和动态视频。连续媒体可以是实时的（交互式的），在这种情况下有一个“紧”的时间
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]]
源和接收器之间的关系，或流（播放），其中关系不太严格。[注：此定义与[2]中连续介质的定义基本相同]
DELIVERY The activity of providing a PUBLISHER's CONTENT, via CONTENT RESPONSES, to a CLIENT. Contrast with DISTRIBUTION and REQUEST-ROUTING.
交付通过内容响应向客户端提供发布者内容的活动。与分发和请求路由形成对比。
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.
分发将发布者的内容从其来源移动到一个或多个代理的活动。分发可以在代理接收请求（预定位）的预期中发生，也可以在代理接收请求（按需获取）的响应中发生。与交付和请求路由形成对比。
DISTRIBUTION SYSTEM A collection of CONTENT NETWORK ELEMENTS that support DISTRIBUTION for a single CONTENT NETWORK. The DISTRIBUTION SYSTEM also propagates CONTENT SIGNALs.
分发系统支持单个内容网络分发的内容网络元素的集合。分发系统还传播内容信号。
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.)
源内容首次进入分发系统的点。任何内容项的来源都是位于发行版“核心”的服务器或服务器集，其中包含该内容的“主”或“权威”副本。（注：我们认为该定义与RFC 2616[1]中“原始服务器”的定义兼容，但包括对CDI有用的附加约束。）
PUBLISHER The party that ultimately controls the CONTENT and its distribution.
出版商最终控制内容及其发行的一方。
REACHABLE SURROGATES The collection of SURROGATES that can be contacted via a particular DISTRIBUTION SYSTEM or REQUEST-ROUTING SYSTEM.
可访问代理可通过特定分发系统或请求路由系统联系的代理集合。
REQUEST-ROUTING The activity of steering or directing a CONTENT REQUEST from a USER AGENT to a suitable SURROGATE.
请求路由将内容请求从用户代理引导或定向到合适代理的活动。
REQUEST-ROUTING SYSTEM A collection of CONTENT NETWORK ELEMENTS that support REQUEST-ROUTING for a single CONTENT NETWORK.
请求路由系统支持单个内容网络的请求路由的内容网络元素的集合。
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].]
服务器接受内容请求并通过发回内容响应为其提供服务的程序。任何给定的程序都可以既是客户机又是服务器；我们对这些术语的使用仅指由程序执行的角色。[注：这是根据RFC 2616[1]中的类似定义改编的。]
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.]
代理传递服务器，而不是源服务器。接收内容请求并发送相应的内容响应。[注：这与RFC 3040[3]中的定义不同，就我们的目的而言，这一定义似乎过于详细。“CDI代理”始终是“RFC 3040代理”；我们不确定反过来是否正确。]
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].]
用户代理发起请求的客户端。这些工具通常是浏览器、编辑器、爬行器（web遍历机器人）或其他最终用户工具。[注：此定义与RFC 2616[1]中的定义相同。]
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.
任何一个网络的规模和覆盖范围都是有限的。增加规模或覆盖范围最终受到设备成本、可用于部署设备的空间和/或对基础设施规模/覆盖范围的需求的限制。有时，由于技术、经济或法律的限制，特定的受众与单个服务提供商或一小部分提供商联系在一起。其他时候，网络提供商可能能够管理代理和分发系统，但可能与内容提供商没有直接关系。这样的提供商希望有一种方法将其交付和分发基础设施与具有内容分发的其他方连接起来。
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.
内容互联允许不同的内容网络共享资源，以便为每个参与者提供比其他方式更大的规模和/或覆盖范围。通过使用通常定义的内容互联协议，每个内容网络都可以将相邻的内容网络视为“黑匣子”，允许它们相互隐藏内部细节。
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.
本节包括许多术语的定义，这些术语用于指代互联网内容网络中涉及的角色、参与者和对象。本节的目的是确定常用术语并提供简短定义。
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.
会计网络两个或多个会计系统之间的互联，以实现它们之间的信息交换。所需的会计联网形式可能取决于对等方之间协商关系的性质，特别是预期经济交换的价值。
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.
关于其他内容网络可用资源的广告信息，通过内容互联网关交换。广告类型包括区域广告、内容广告和分销广告。
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.
来自内容网络的请求路由系统的关于内容网络的拓扑、地理位置和性能方面的区域广告。与内容广告、分销广告相比。
BILLING ORGANIZATION An entity that operates an ACCOUNTING SYSTEM to support billing within a NEGOTIATED RELATIONSHIP with a PUBLISHER.
计费组织运营会计系统的实体，以支持与发行商协商关系内的计费。
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
内容广告来自内容网络的请求路由系统的关于内容网络上一个或多个内容集合的可用性的广告。与区域广告、分销广告相比
CONTENT DESTINATION A CONTENT NETWORK or DISTRIBUTION SYSTEM that is accepting CONTENT from another such network or system. Contrast with CONTENT SOURCE.
内容目的地接收来自另一个此类网络或系统的内容的内容网络或分发系统。与内容源对比。
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.
内容互联网关（CIG）：一种可识别的元素或系统，通过它，内容网络可以与其他网络互连。CIG可以是分发互联网络、请求路由互联网络和/或计费互联网络的接触点，因此可以包括用于内容网络的一些或所有相应系统。
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.
内容复制将内容从内容源移动到内容目标。请注意，这是内容从一个网络到另一个网络的移动。在单个网络的分发系统中，可能存在类似或不同的机制来移动内容。
CONTENT SOURCE A CONTENT NETWORK or DISTRIBUTION SYSTEM that is distributing CONTENT to another such network or system. Contrast with CONTENT DESTINATION.
内容源向另一个这样的网络或系统分发内容的内容网络或分发系统。与内容目的地形成对比。
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.
分发广告从内容网络的分发系统到潜在内容源的广告，描述一个或多个内容目的地的功能。与区域广告、内容广告相比。
DISTRIBUTION INTERNETWORKING Interconnection of two or more DISTRIBUTION SYSTEMS so as to propagate CONTENT SIGNALS and copies of CONTENT to groups of SURROGATES.
分发网络互连两个或多个分发系统的互连，以便将内容信号和内容副本传播到代理组。
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.
登记描述了作为协商关系的一部分，已接受来自另一个内容网络的分发任务、已同意代表另一个内容网络执行请求路由或已同意向另一个内容网络提供记帐数据的内容网络。与原版相比。
INJECTION A "send-only" form of DISTRIBUTION INTERNETWORKING that takes place from an ORIGIN to a CONTENT DESTINATION.
注入从源站到内容目的地的“仅发送”形式的分发互联网络。
INTER-Describes activity that involves more than one CONTENT NETWORK (e.g., INTER-CDN). Contrast with INTRA-.
INTER描述涉及多个内容网络（例如INTER-CDN）的活动。与内部-形成对比。
INTRA-Describes activity within a single CONTENT NETWORK (e.g., INTRA-CDN). Contrast with INTER-.
INTRA描述单个内容网络（例如，INTRA-CDN）内的活动。与INTER-形成对比。
NEGOTIATED RELATIONSHIP A relationship whose terms and conditions are partially or completely established outside the context of CONTENT NETWORK internetworking protocols.
协商关系其条款和条件部分或完全在内容网络互联协议的上下文之外建立的关系。
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.
发起描述了一种内容网络，作为协商关系的一部分，它向另一个内容网络提交分发任务，请求另一个内容网络代表其执行请求路由，或请求另一个内容网络提供记帐数据。与入伍相比。
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.
远程内容网络能够为特定请求提供内容的内容网络，该请求不是该请求的权威请求路由系统。
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.
请求路由互连两个或多个请求路由系统的互连，以增加至少一个互连系统的可到达代理的数量。
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.
本文档定义了内容互联的术语和概念。该术语本身没有引入任何与安全相关的问题。内容互联概念的实施确实会引发一些与安全相关的问题，我们将在下面的大类中确定这些问题。其他CDI文档将更详细地解决其特定的安全相关问题。
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.
安全关系建立：内容互联网关必须确保内容网络仅与预期的其他内容网络互联。必须能够防止未经授权的互联网络或欺骗另一个内容网络的身份。
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.
安全内容传输：内容互联网关必须支持内容网络机制，以确保内容的完整性以及分发和交付的完整性，即使涉及原始网络和登记网络。内容互联网关必须考虑防止内容被盗或损坏的机制。
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.
安全的元内容传输：内容互联网关必须支持内容网络之间准确、可靠、可审核的会计信息的移动。内容互联网关必须考虑防止会计数据和类似元内容转移或损坏的机制。
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).
作者感谢Fred Douglis（AT&T）、Don Gilletti（CacheFlow）、Markus Hoffmann（Lucent）、Barron House（Cisco）、Barbara Liskov（Cisco）、John Martin（Network Appliance）、Nalin Mistry（北电网络）、Raj Nair（Cisco）、Hilarie Orman（Volera）、Doug Potter（Cisco）和Oliver Spatscheck（AT&T）的贡献和评论。
[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.
[1] 菲尔丁，R.，盖蒂斯，J.，莫卧儿，J.，弗莱斯蒂克，H.，马斯特，L.，利奇，P.和T.伯纳斯李，“超文本传输协议——HTTP/1.1”，RFC2616，1999年6月。
[2] Schulzrinne, H., Rao, A. and R. Lanphier, "Real Time Streaming Protocol", RFC 2326, April 1998.
[2] Schulzrinne，H.，Rao，A.和R.Lanphier，“实时流协议”，RFC2326，1998年4月。
[3] Cooper, I., Melve, I. and G. Tomlinson, "Internet Web Replication and Caching Taxonomy", RFC 3040, June 2000.
[3] Cooper，I.，Melve，I.和G.Tomlinson，“互联网Web复制和缓存分类”，RFC3040，2000年6月。
Mark Stuart Day Cisco Systems 1414 Massachusetts Avenue Boxborough, MA 01719 US
美国马萨诸塞州伯斯堡马萨诸塞大道1414号马克·斯图尔特·戴思科系统公司01719
Phone: +1 978 936 1089
EMail: mday@alum.mit.edu
Phone: +1 978 936 1089
EMail: mday@alum.mit.edu
Brad Cain Storigen Systems 650 Suffolk Street Lowell, MA 01854 US
美国马萨诸塞州洛厄尔萨福克街650号Brad Cain Storigen Systems 01854
Phone: +1 978 323 4454
EMail: bcain@storigen.com
Phone: +1 978 323 4454
EMail: bcain@storigen.com
Gary Tomlinson Tomlinson Group 14324 227th Ave NE Woodinville, WA 98072
加里·汤姆林森·汤姆林森集团14324号，华盛顿州伍德维尔东北227大街，邮编：98072
Phone: +1 425 503 0881
EMail: gary@tomlinsongroup.net
Phone: +1 425 503 0881
EMail: gary@tomlinsongroup.net
Phil Rzewski 30 Jennifer Place San Francisco, CA 94107 US
Phil Rzewski 30珍妮佛CA旧金山94107美国
Phone: +1 650 303 3790
EMail: philrz@yahoo.com
Phone: +1 650 303 3790
EMail: philrz@yahoo.com
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