Performance Testing News for March 27, 2014

Why Your CDN is Slow for Mobile Clients

When companies have an extension in the mobile area they find that their CDN is less effective for their mobile clients. With little to no improvements for mobile CDN, clients are considering disabling it entirely because they’re uncertain if it’s worth it. This has been a growing concern as more people are finally paying attention to performance and on their mobile sites.

Lets do a quick refresher about a CDN. The objective of a CDN is to move the bytes as close to the user as possible and to do so CDNs deploy cache servers within various data centers and peering points around the globe. As a result, CDN minimizes the propagation latency and if a static resource is served, also reduces the server response time by returning a cached asset. One strategy is to improve the end-to-end latency by moving the cache servers even closer to the client: instead of positioning them outside the ISPs network, could we move them inside? The solution is possible. However, in practice, this is a tricky problem.

First, the number of peering points is relatively small, which allows CDNs to deploy in dozens of well known locations around the globe to provide their service. Also, to do so, they don't have to do any special deals with individual ISPs: typically, the servers are deployed in shared data centers (peering points). By contrast, moving servers into the ISP network would require individual deals with each ISP - not impossible, but obviously a much harder operational and business problem.

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