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Azure CDN – Available features and functionality

Last week I had some interesting discussions around payload delivery and CDNs. I realize how easily people can misunderstand some features or functionality, thinking that it is normal or making the wrong assumption.
In this context, I will write 3 posts about Azure CDNs, focusing on what is available, what we can do and what we cannot do.

Let’s start with the first topic, and talk about features and functionality that is available now (Q3, 2016) on Azure CDNs.  You will find a lot of useful information on Azure page and I’m pretty sure that you already check it.
In comparison with the last few years, there was a big step that was done by Microsoft. They signed partnerships with Akamai and Verizon (both of them are one of the biggest CDNs providers in the world).

This was a smart choice, because developing and construction your own CDNs is not only expensive, but there is a lot of effort that is required. There are some things that doesn’t make sense to construct by yourself if you don’t need something additionally.
A nice thing here is that you don’t need a dedicated contract with each provider. You only need your Azure Subscription and no custom contract or invoice from Akamai or Verizon.

In general, the CDN features that are provided by them are similar with some small exceptions, that (not) might impact on your business.  Based on the features list, we could say that Akamai is the most basic one and Verizon has some additional features, but both of them are offering the base functionality that is required from a CDN.

The things that are available only on Azure CDN from Verizon are:
      1. Reports related to Bandwidth, Cache status, HTTP error codes and so on.
      2. Restrict access to the content, based on the country/area. Verizon allows you to specify a list of countries (DE, UK) or areas (EU, AP – Asia/Pacific) that can(not) access that content. The filtering is done based on the client IP and is per directory. It is good to remember that this rule is applicable recursive at folder level, there is no support for wildcards and you can specify one rule per folder that can contains multiple countries (areas). Being a recursive rule, if you define a rule one level down, only the rule defined on the sub-folder will apply – simple rule engine.
      3. You can pre-load content in cache. Normally, content is loaded in cache only when it is requested for the first time. Azure CDN from Verizon allows us to specify content that we want to pre-load. Don’t forget that you need to specify exactly the file that you want to pre-load and you can pre-load maximum 10 files per minutes (per profile).  There is a kind of support for regular expression, but each result from it needs to be a relative path to a file.

Now, that let’s see what are the features that are supported by Azure CDN from Akamai and Azure CDN from Verizon:
      1. HTTP support
      2. DDOS protection
      3. Dual Stack support (IPv4 and IPv6)
      4. Query String Cache – how content is cached, when the path is a query and not static. There are 3 options available that allows us to cache each unique query, ignore query string and not cache URLs that contain query strings. The last option is very useful.
      5. Fast purge – Allowing us to clean the cache, even if the TTL (Time To Live) of content didn’t expired yet. The purge can be done from Azure Portal, PowerShell or by REST API.
      6. REST API for CDN configuration (as for all other Azure Services)
      7. Custom domain name support
      8. Caching content from Azure Storage. Access to Azure Storage is done using REST API. In this way we can cache blobs and even Azure Tables (as long as we know that it is a static content).

Azure CDN from Verizon is available in two tires, Standard one and Premium. Of course, except the price there are features that are available only on Premium like:
      1. Real-time CDN Status – Is useful if you need real time data related to bandwidth, number of connection, errors codes and cache status. For CDN, normally, it is nice to have, but you do your job without this kind of information
      2. Advance Reports – Detailed geographical reports related to traffic and different views per day, hour, file, file type, directory and so on.
      3. Customizable HTTP behavior based on your own rule

As we can see, there are a lot of features available for Azure CDNs. For normal use cases, you can use without a problem.


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