CDN Selection Tips

Which content delivery network is the best? There’s no short answer to that question, but here are some of our tips that will help you make a better decision.

Selecting the best CDN provider for your business completely depends on your needs. For us, the holy trinity in the world of content delivery consists out of performance, features and price. When choosing any CDN provider, it’s always a good idea to match your needs with their offering on those three variables.

Performance

No CDN inherently performs better than the other – rather, their networks are optimised in different ways, which can have different results depending on a customer’s filetype, the ISP of a user and the functioning of the nearest point-of-presence (PoP). Here are some tips from us to you, on what to look out for:

Optimising for latency is useful for customers who mainly serve small files. When the total transfer time is already quite low, any additional millisecond will have a huge impact on the total transfer time. Important here is to work with providers who handle small files well and have an optimal Round Trip Time (RTT) of an object.
Optimising for throughput is often done for large file delivery. A few extra milliseconds needed to establish the initial connection don’t matter much – here we focus on the total time it takes to deliver the complete file. A CDN will need to have the capacity to send the file as fast as possible, so fast even that the only limiting factor should be the user’s ISP. When it comes to large files, clogged pipes are your worst nightmare!
Availability of a CDN is easily taken for granted, also because we don’t often experience a full-blown global outage. The reality of availability or more nuanced than your site simply being online or offline, and we often see regional ‘hiccups’. Causes can include maintenance, capacity problems, disputes over peering agreements or state censorship. On a regional level, performance degradation and outages are a business concern. If availability is of the upmost importance, it’s advisable to consider a CDN provider with a 100% uptime guarantee or a multi-CDN provider.

Curious about how different CDNs compare on availability and latency? Have a look at the Cedexis country reports or on Cloudharmony’s Cloudsquare Service Status.

Features

Most CDN providers have way more to offer than just a bunch of PoPs! Depending on your core business, you may want to zoom in on dedicated products to fit your type of content and your integration needs. Here are a few features commonly offered by providers:

Video on Demand (VOD)
Live video streaming
Large file delivery
Small file delivery
Mobile acceleration
Cloud) storage
Security
Realtime) Analytics / statistics
Origin shield
Realtime) purge
SSL
SPDY and HTTP/2
Custom rules
API
Support

Depending on the provider, features might be free or will have to be paid for. You’ll find that the exact same features go by different names and have different branding per provider, so be sure to double-check.

Price

The four most commonly used pricing methods for CDNs are:

Data traffic
- Simply pay for the amount of Gigabytes transmitted.
- Possibility of committing to a certain amount of traffic per month will usually lower the price.
- In committing, there’s a risk of over-commitment where you use less than predicted but still have to pay for the committed amount.
- Usually, the amount of data below your commitment is not carried over to the next month.
Bucket of Bits
- You pay for an X amount of bits (for instance 1 PB) and you have 1 year to use it.
- Overages are often charged at the same rate.
- Mostly interesting for broadcasters of “spiky” events like a sports championship during the summer; you know a lot of data will be transferred but not exactly when.
Plan
- Some CDNs work with feature sets and put them into plans.
- Higher price tiers include more bang for your buck: you’ll “unlock” additional features (e.g. custom SSL certificates or security features) and often get a lower unit price.
- Some plans are essentially commits but packaged differently. These plans are recognisable when the features stay the same but the amount of data included increases and the price per GB lowers.
Bandwidth (95th percentile)
- Although common in the network world, this billing method is not that common in the CDN world. You’ll find this method mostly at CDN providers that also own large networks (network operators) and you’ll have the ability to combine their IP transit offer with usage of the CDN.
- This method can be beneficial for some traffic patterns but also lacks transparency in terms of costs for most customers.

Billing usually takes place upfront for committed amounts of traffic and in arrears for any overage, or burst, traffic.

Need help figuring out your CDN needs? Get in touch!

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