Azure Front Door or Azure CDN — What Solution Will You Choose for Your High Availability Sites
Microsoft Azure provides a wide suite of services to make your sites and services highly available across geographic regions. Since Azure Front Door became Generally Available, there is often a question around what would be the right choice between Azure Front Door and Azure CDN delivery of your highly availability sites and content.
Azure Front Door
Microsoft developed Front Door several years ago to enhance the performance of their signature services such as Office 365 and Bing search.
It was originally developed as an interface into the Microsoft’s internal WAN (Wide Area Network) deployed across globally distributed edge locations. When you use a service supported by Front Door, it is served via this WAN through your closest edge site leveraging a split TCP method. From there, you connect to the closest available copy of the service or content.
Going by the success of this internal architecture solution that Microsoft utilized to serve their major services like Office 365 and Bing search, Microsoft opened Front Door up via its Azure Cloud offering to its entire consumer base to utilize.
Capabilities of Azure Front Door
Azure offers delivery of your sites and services through a CDN of Microsoft WAN Edges and in the process enhances the performance of your services in addition to providing high availability.
Azure Front Door routes incoming requests to a primary region. If the application running that region becomes unavailable, Front Door can fail over to the secondary region.
When you are requesting a large document, Azure Front Door uses object chunking method to request the document in smaller chunks and caches it. This process continues until the entire file is downloaded (if requested), all byte ranges are available (if requested), or the client terminates the connection.
If you have regional sites like — us.yoursite.com, india.yoursite.com, aus.yoursite.com — Azure Front Door will use split TCP logic to redirect to your nearest POP (Point of Presence) via the Microsoft WAN Edges and begin caching and delivering files from that POP location.
What is Azure CDN
Azure Content Delivery Network has been around for a while. A content delivery network (CDN) is a globally distributed network of servers that can deliver content to consumers. CDNs store cached content on the edge servers’ POP locations that are close to consuming users, thereby minimizing network latency.
Azure CDN has 24 POP locations in North America, 4 in South America, 26 in Europe, 5 in Africa, 2 in the Middle East, 4 in India, 22 in rest of Asia, 5 in Australia & New Zealand. This is far more than several other providers and more than Front Door powering Microsoft’s WAN itself.
Capabilities of Azure CDN
Such enormously distributed POP edge locations, along with added capabilities like Site acceleration, Video streaming optimization, Adaptive image compression, Azure CDN can provide very large scale, highly available delivery of complex content. When you think of scenarios like Netflix-scale content, delivering videos to your globally distributed consumer base via their nearest edge location, Azure CDN would be an indispensable solution.
While both Azure Front Door and Azure CDN offer their own unique high availability capabilities — there are several scenarios where you might end up using both in your architecture. You can use Azure Front Door for delivering your sites, services and APIs, and use Azure CDN for delivering static content like Videos, Images and PDFs — this would provide the optimal solution which would incorporate the best capabilities of both options.
