When choosing to buy CDN service there are a lot of factors which go into play. Obviously, you want the best service for the best price. Use the following as guide to help you when interviewing CDN service providers.
1. Bandwidth needs
What are your bandwidth needs? Are you going to use 50GB/month or 50TB/month? CDNs charge by GB transferred (in most cases). If you’re only delivering a small amount of traffic, it may not be necessary to purchase CDN service. You might be able to get away with upping your current web host provider from a shared environment to a dedicated environment. Maybe it’s time to move to a business class web host, instead of that $5/month provider you’re using now.
It doesn’t make sense to pay a Tier 1 CDN thousands of dollars a year to deliver 4 videos. If you’re having so much problems with your video or software downloads, then look at the root cause and fix it!
When you are delivering about 500GB/month it starts to make sense to off load that heavy lifting to a CDN. By now, you are getting several thousand requests per month or even per second and your single web server in 1 data center won’t be able to keep up with the traffic.
Certainly when you are doing over 1TB/month of static content delivery, you should use a CDN. This will ensure your videos, podcasts, music, images, documents, and software downloads are getting to your customers quickly and efficiently.
2. Network Performance
All CDNs big and small say they have the best network! There are basically 3 kinds of CDNs: Internet based, Peering/Private based, and Peer to Peer (P2P).
About the only Internet based CDN is Akamai. Akamai has thousands of servers all over the place. Then using some fancy algorithms, they route traffic from 1 PoP to the next getting your content onto the backbone of what ever ISP your end user is on. They then cache the content in that closest PoP so the next person in that region/ISP has the content already close to them. Obviously, this method works as Akamai is the biggest CDN on the globe and boasts the most customers.
A peering/private CDN is one who puts servers in regionalized PoPs around the world. Then in those PoPs they peer with, or directly connect with as many ISPs and backbones as they can. Then when someone requests a piece of content, the file is delivered directly from the CDN to the end user network and is able to by-pass the Internet all together, in most cases. Most other CDNs use this model. Limelight Networks is the most successful in this configuration. They have a private fiber backbone as well to move content from Origin Server to PoP. Other CDNs who follow this model are Panther, EdgeCast, Level3, CDNetworks, and others.
Finally, the idea of P2P is intriguing. Simply have all content viewers act as a PoP and replicate the content around the globe. There’s little or no infrastructure cost and theoretically you can get your content on to any ISP in the world. P2P has it’s place, but as a means to deliver mission critical and revenue generating content, this method should be avoided.
As a side note, there are Hybrid CDNs who employ P2P and Peering/Private methods. These are intriguing, however for secure delivery, using a P2P is less desirable as your content will end up on hundreds to thousands of individual computers with little or no control over who gets access to it.
Does your CDN support the technology you require? All CDNs will deliver content via HTTP Progressive download. But does your CDN support true Flash Streaming (RTMP), true Windows Media Streaming (MMS, RTSP), Quicktime or Real Media streaming? What about Flash Live or Windows Media Live? Can they do MP3 Live? Do they have a Token Based Authentication secure URL product? Can they do pseudo-Flash streaming? Do they have any special services for HD delivery? What about a mobile CDN platform? Is it easy to get content to the CDN?
Finally, what about their analytics? Do they offer quality analytics? Is it easy to use? Does it show number of request per object? Is there a content management piece? Do they offer Geo-Reporting? Can you get raw logs?
4. Other products and services
What else can your CDN of choice do for you? Do they have a professional services department? Can they help with monetization? Do they offer encoding/transcoding? What about digital rights management (DRM)? Do they offer a live event monitoring service? Is there a content management system or digital asset management system available? Does your service include embeddable media players? Can they cache whole web sites? Do they support e-Commerce or shopping carts?
What kind of support can your CDN offer? Ask for the number of the helpdesk and call it. How quickly did they answer? Did you get a person or just voice mail? Is there email support available? Do you have access to technical personnel during the integration phase? Who do you call if you have a question about your bill? Does your CDN even offer support? What happens if you call in the off hours? What does their Service Level Agreement look like? Most CDNs offer a 100% SLA, but what does that really mean and how do you get credit if they don’t meet their SLA?
Does your CDN require an annual contract? Do they offer a month-to-month contract? Are they asking you to commit to a minimum amount of money per month whether or not you use that much? What happens if you go over your commit, how much is that going to cost you? Can you pay with a credit card? Do you have to pay with a credit card?
How long has your CDN been in business? Are they funded by venture capital? Do they have huge amounts of outstanding debt? Are they facing an uncertain law suite by a competitor? How much cash do they have in the bank? Over the past 12 months there have been some major moves in the CDN industry. There have been a number of players who have all but disappeared. There have been some acquisitions and mergers, and some major players are bleeding cash so much that they may not be around in the next 12 months. Be careful about putting content on an iffy CDN. Research them independently and see if they have had any major complaints or severe outages.
Notice cost is at the bottom of the list? This is because cost should not be your number one concern. You will find huge differences in cost from CDN to CDN. Expect to pay anywhere from a few cents per GB up to over $1 per GB. There are a number of factors that will dictate what you pay. Don’t expect to get the same pricing that a big boy like Netflix will get when you are passing 200GB/month. Your price will be based on how much traffic you pass. The more you pass, the cheaper the price will be. Also, most of the other items mentioned above will factor in your cost.
If the CDN you decide to go with is too expensive or is asking for more of a commit than you want. Ask them if they have resellers you can go through. Usually these resellers can offer better terms. You may pay more per GB than going straight with the CDN, but you might only pay for what you use. Also beware that going with a reseller may limit you to support from that reseller. You might not be able to call up the CDN directly for support. You may also only get basic reporting with a reseller instead of the full blow analytics package offered by the CDN.
Consider all these factors when deciding which CDN to go with. The biggest factor is how much traffic are you going to pass. You may have fun driving that Lexus, but you can still get to work in your Toyota. Choose a CDN that meets your needs and fits your budget.