CDNs are intermediary servers that replicate read intensive data to provide better performance when user requests them. A close relative of CDNs is edge computing (e.g. gaming stations) where lots of computation is done directly close to the user.

Types of CDNs

Mainly three types of CDNs:

  • Highly distributed ones.
  • Database based ones.
  • Ad-hoc CDNs. Content Delivery Networks-20250403143719218

Advantages and disadvantages

The main reason we use CDNs is to lower the value of latency: we are in fact bringing the data closer to the user. We have much less data in length to be transmitted. Yet we have some disadvantages too:

  • They usually are not able to provide much storage
  • Difficult to manage and coordinate.

Cache Design

If you want to optimize for computer caches, see Cache Optimization.

Increase Hit Ratio

If we increase the cache hit ratio, we will have indeed better performance. There are some standard ways that are known in the academy:

  • Increase cache size
  • Design better algorithms Content Delivery Networks-20250403144237728

Lazy promotion and Quick Demotion

These are two design principles that have proven to work when designing efficient caches. Lazy promotion Retain popular objects with minimal effort

  • Improve throughput due to less computation
  • Improve efficiency due to more information at eviction

Quick Demotion: Remove unpopular objects fast, such as one-hit-wonders.

Sieve Caching

Load Balancing

Global Load Balancing

  • Avoid TCP set up delay (latency)
  • Use of DNS caching. AKAMAI uses a kind of iterative DNS discovery (see Livello applicazione e socket#Domain Name System). In this DNS type, it makes a request, and it tells you other DNS name system to contact to get the IP. When you go the IP, you can make the HTTP request to the akamai server for the resource. This server contacts the content provider if there is no copy available, else it does it correctly.

Anycast

Advantages • No extra round trips • Route to nearby server Disadvantages • Does not consider network or server load • Different packets may go to different servers • Used only for simple request-response apps

It uses consistent hashing (See Cloud Storage#Key-value stores) to know exactly what server to contact.