{"id":319942,"date":"2016-01-04T16:33:40","date_gmt":"2016-01-04T15:33:40","guid":{"rendered":"https:\/\/wp-rocket.me\/blog\/?p=684"},"modified":"2023-05-03T10:38:03","modified_gmt":"2023-05-03T08:38:03","slug":"difference-cdn-and-domain-sharding","status":"publish","type":"post","link":"https:\/\/wp-rocket.me\/blog\/difference-cdn-and-domain-sharding\/","title":{"rendered":"What Is the Difference between a CDN and Domain Sharding?"},"content":{"rendered":"

Nowadays we often hear people talk about CDNs. But there is another, less known term\u2014domain sharding<\/strong>\u2014which is confused with CDN very often, even though the two technologies are completely different.<\/p>

What is Domain Sharding ?<\/h2>

Too often we read tutorials about setting up a CDN where in fact domain sharding is described.<\/p>

History<\/h3>

Traditionally, browsers limit the number of simultaneous requests to a single domain. That restriction has been defined in the specifications of the HTTP\/1.1 protocol: the goal was to not overload the query servers.<\/p>

A website with many HTTP requests (images, CSS files, JavaScript, etc.) thus was penalised by that limit.<\/p>

Definition<\/h3>

Domain sharding has been set up to circumvent the allocation of static files (images, CSS, JS) on multiple subdomains. That way it is possible to multiply the number of simultaneous requests by the number of subdomains.<\/p>

Using domain sharding gives us the possibility to load content on cookie-free subdomains.<\/p>

However, this solution is not flawless. In fact, each subdomain adds additional DNS resolution which usually is significant in terms of performance. A DNS resolution is the correlation between the URL and the IP address associated with it. This request takes between 120 and 200 ms before being resolved.<\/p>

Just a few years ago, the practice of domain sharding was highly recommended. Today things have changed for many reasons.<\/p>

Browser Evolution<\/h3>

Internet browsers have evolved enormously. These days they perform 6 simultaneous requests per domain (when IE only allowed 2) on average. With a small number of HTTP requests, the establishment of domain sharding can be contra-productive.<\/p>

On Mobile<\/h3>

On mobile connections, DNS resolutions are much longer than with a conventional connection. An excessive use of domain sharding could be very expensive in terms of performance.<\/p>

Should We Still Use Domain Sharding?<\/h3>

There is no universal answer to this. Everything depends on your website and on the number of HTTP requests it realises. Generally, it is recommended to not use more than two subdomains.<\/p>

You should also note that the HTTP\/2.0 protocol will make this practice outdated. This is already the case for SPDY, the experimental protocol created by Google.<\/p>

If you\u2019d like to investigate the subject, we recommend these articles for reading:<\/p>