内容交付网络买方指南2015

As the CDN world has become commoditized in terms of bandwidth pricing, I have begun to feel this annual Buyer’s Guide article has undergone much the same transformation. Reading back over previous years’ insights on the subject reveals little in the way of significant change. 人们想要分割的毛发总是特定于用例的, so I can only provide a broad narrative about the basic key performance indicators (KPIs) you want to explore and provide a starting point from which you can dig deeper.

CDNs increasingly differentiate themselves with value-added services that encompass almost the entire scope of the other Buyer’s Guides in the 原始资料, 从编码到发布模型和格式支持. That scope is certainly too wide to cover in a Buyer’s Guide that tries to help a generic CDN buyer.

While I see fundamental changes in the economic landscape and how CDN buyers are actually sold to, as well as some remarkably different technical methods to achieve the same content delivery goals, 我们几乎总是回到相同的核心基本kpi.

当然，cdn最初是一种商业解决方案. When transcontinental or intercontinental telecoms were sparse—particularly before 2002—there was a strong economic incentive to use proxy servers at each end of these premium long-haul links. 这就是1997年至2002年间CDN诞生的原因.

But as those fibres opened up and competition dragged the pricing down, the CDNs began to distinguish themselves by offering comprehensive support for occasional-use services that they ran on their servers. They were certainly among the first—if not the very first—SaaS providers.

在过去的15年里, 然而, 租用基础设施即服务已经成为可能, 部署利基市场, variable-use servers in response to demand from any enterprise, 很少或根本没有资本承诺.

This has meant that CDNs have had to focus more and more on why they are better than a DIY CDN that a publisher could create itself.

为此目的, CDNs now either compete by having differentiated ecosystems that can offer more of a turnkey solution to the larger enterprise, or they compete on hair-splitting differentiation about how their servers perform relative to the networks on which they provide services.

正如我上面提到的, the scope of what each CDN offers in its ecosystem is too broad for this article. But the core the network delivery hair-splitting at least has a number of fairly clear KPIs that give some grounds for comparison. 事实上, that comparison is becoming so formulaic that there is an emerging CDN brokerage marketplace on the rise, in which readings of these KPIs are collected in huge quantities and aggregated into data sets that publishers can mine in real time to make decisions about which CDN is best for a given user request.

Much like stock exchanges facilitate the rapid comparison of financial data to enable software-based transactional decisions, these CDN brokerages are akin to neutral “clubs” that it is in everyone’s benefit to join, 即使这会造成极端的竞争.

So long as the CDN is confident in its proposition and can “play the game,” then it stands to benefit from publically sharing the deep insight into its business that this shift requires.

由于CDN联盟在2008年至2013年之间出现, the issue of billing through your competition was never really addressed properly. The neutral brokerage model is much more logical; a publisher has multiple CDN provider accounts, and the brokerage works out which is the best for that publisher’s end users to be serviced by. The resulting bandwidth is sold directly to the publisher from each CDN, but the extent to which any one CDN gets used is determined by the broker—and that decision-making process is what I want to focus on, 因为它本质上是自动购买CDN.

分析聚合器简化流程

在过去的几年里，我推荐过你哪些地方, 作为出版商, 看看延迟, 吞吐量, 和地理位置的详细信息，当你选择你的CDN提供商, 这些经纪人现在为你做这些, 在你建立你的工作流程时，不仅仅是一次, but pretty much every time your users request a file or stream.

我和Pete Mastin谈过 Cedexis, who asserted that Cedexis is more akin to Google Analytics than to my analogy of a stock exchange. Cedexis aggregates data and makes it available to customers in near-real time to then underpin its own load balancing requirements. It just happens that this load balancing between multiple CDN providers has an effect just like the commercial exchange model I have highlighted.

这一主张有两个核心方面.

第一个是雷达.js, which is a small script that all those who sign up (for free) to Cedexis then embed in their webpages. Whenever a page is executed by a client browser it pulls a small (100KB) file to the client. 该文件测量往返时间, 延迟, 和吞吐量, 然后将结果传回给Cedexis. 雷达.js is executed billions of times a month in many millions of web browsers and creates an incredibly detailed picture of how both CDNs and ISPs are performing. 最近的一次来自Mastin的博客文章演示如何使用数据集. 对于极客来说 流媒体的 Dan Rayburn—who regularly cites Cedexis data in his blogs—and myself, this is an indulgent insight into the real state of content delivery over the internet.

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