Why PoP Count Isn’t Everything with CDNs
May 14, 2015 | Robert Gibb
Choosing the right CDN depends on several factors, including the number of points of presence (PoPs) that comprise a provider’s network. As the last link between the CDN and users, PoPs are placed in key locations around the world to bring content closer to its destination.
Companies often look at PoP count as the top indicator of a CDN’s quality. After all, more PoPs means shorter distances between users and content. But while more PoPs can contribute to faster load times, an excessive amount can have a harmful impact.
This post explores why PoP count isn’t everything, and how relevant PoP placement can benefit your bottom line.
When More PoPs Matter
As the gateway between users and content, PoPs provide several key features for CDNs. They bring content closer to users, they provide load balancing, and they offer redundancy. Services that benefit the most from additional PoPs generally have a large global audience and bandwidth-intensive media like longer videos.
Companies expanding into other areas of the globe can also benefit from more PoPs. For instance, a company with a growing user base in Australia would benefit from multiple PoPs in that region. Users in Australia could fetch content from a local PoP rather than make a round trip to the U.S. or Europe.
Sample content delivery network map with PoP locations closely matching user demand.
The China Scenario
Some of our customers with a growing user base in China choose to load balance MaxCDN with China CDNs like ChinaCache or ChinaNetCenter. By doing so, they can continue to use the MaxCDN features they love: 24/7 engineering level support that helps with multi-CDN integration for instance.
While MaxCDN does have several Asian PoPs, sometimes a few aren’t enough. But instead of completely switching to a larger provider – and potentially paying for a bloated network – customers can load balance traffic intelligently by welcoming a relevant, targeted CDN into their content delivery mix
Why pay for an excessive amount of PoPs offered by one provider if they aren’t impacting your bottom line? As you’ll see below, Netflix asked this question. Because when a CDN’s architecture is too robust for what you require, you pay for what you don’t need.
Netflix Needed Smarter PoPs, Not More
Netflix, which delivers a third of peak Internet traffic, uses a network of PoPs through a home grown CDN and through peering agreements with ISPs. With this program called OpenConnect, Netflix can cache hundreds of terabytes of video in areas of high demand.
Before starting to create its own content delivery network, Netflix was load balancing multiple third party CDNs that probably weren’t entirely relevant. For instance, the PoPs could have been stacked on top of each other, offering too much redundancy to be cost-effective, or could have been located in areas where an insignificant amount of Netflix users were located.
Regardless of the specific reasons, as a growing company delivering mass amounts of traffic, developing a more relevant approach made “economic sense.”
While few companies match the bandwidth needs of Netflix and don’t require their own private CDN, all companies DO require a content delivery solution that’s relevant for their audience.
When More PoPs Mean Less
It’s not feasible or necessary for every company to produce a private CDN like Netflix. Plus, the majority of online services that companies offer don’t require such a degree of customization. For just about every digital endeavor, there’s a third party CDN – or combination of CDNs – that can handle traffic in a cost-effective, reliable manner.
Cost-effectiveness and reliability are the two most important factors when considering CDN architectures. And, as previously mentioned, what makes a network cost-effective is PoP relevancy, or where PoPs are located in relation to users.
Sample content delivery network map depicting inefficiencies of sheer PoP volume.
Density > Count
When dealing with the amount of PoPs, density matters most. For instance, if you have more users in Europe than Asia, you want more PoPs in Europe. This is basic knowledge, but also frequently overlooked. When people see how many PoPs a CDN has, they can quickly become blinded to what matters most:
- Relevance of PoPs based on audience
- Engineering support for fully leveraging PoPs
- Instant purging and provisioning
We’ll tell you straight up that you’re paying for the PoPs you don’t necessarily need. Even if you only require PoPs in the U.S. and Europe, what you pay on a monthly basis to your CDN provider is used to create PoPs elsewhere. Because even though you don’t need it, other customers do.
This is why it’s important to find a CDN solution that is as relevant as possible to you and your audience. This will ensure that your money is mostly going to building a network that will support you rather than other CDN customers.
PoPs owned by content delivery networks work best when delivering static content.
On the other hand, dynamic content is difficult to cache and users are redirected to the origin server more frequently. This limits the benefit of the CDN, and could actually cause wasted effort if the CDN tries to replicate the content across its various PoPs.
How PoP Density Affects Different Industries
When MaxCDN noticed its London PoP was handling a large percentage of traffic in Europe, our team saw a need to increase the density in that region with a second London PoP. This was decided after a careful analysis of how traffic was being routed, what file types the companies using that PoP had, and how we needed to scale to meet these needs.
While the single London PoP could flawlessly deliver smaller files on behalf of hundreds of companies, smaller files weren’t the only files being delivered. Large files like videos, games, and software were also being handled from this location. Additionally,our base of customers with European traffic was growing at a strong, steady rate.
For this reason, we had to increase the density of PoPs in this specific region.
The following chart breaks down PoP density requirements by industry, showing how a higher PoP count in a specific region could benefit a web service.
|Industry||File Types||Use Cases||PoP Density Required|
|Advertising||.jpg, .png, .gif, .swf||Static content, small files||No|
|Hosting||.html, .css, .js||Static and dynamic content, small files||No|
|Mobile||.html, .css, .js||Static and dynamic content, small files||No|
|Gaming (Downloads)||Varies||Static content, medium and large files||Maybe|
|Software Distribution||.exe, .dmg, .sh||Static content, medium and large files||Maybe|
|Media||.webm, .mp4, .avi||Static content, large files||Yes|
Moderate to high demand is assumed in all scenarios.
Services that benefit the most from PoP density are those that provide larger static files such as gaming downloads, software and media.
Because these files rarely change, the CDN can serve more cached content before having to hit the origin server. And since customers are more likely to be located near a PoP, they don’t have to wait nearly as long to finish the download.
On the other hand, services that provide more dynamic or personalized content would benefit less from high PoP density. If your content changes frequently, the CDN will either have to replicate your content across more locations when the cache becomes stale, or send users to your origin server.
Meanwhile, services that provide a mix of static and dynamic content could benefit from a high PoP count/density if the static content is in high demand.
Can You Benefit From More PoPs?
When it comes down to it, knowing your audience is key. If a large number of users are in a certain region, a CDN with a PoP in that region will do more for you than a CDN with several PoPs in nearby regions.
An analytics service such as Google Analytics, Clicky, or Open Web Analytics can tell you where your users are concentrated and how well your website is performing for them. From there, you can head over to CDN Planet to see which CDNs serve your areas.
Instead of jumping for a high PoP count, consider how extra bandwidth usage could impact your bottom line. Remember that you can often scale your CDN as your business grows, either by implementing a multi-CDN strategy or by signing up with a CDN that’s on the same growth track as you.