Akamai CDN Implementation Guide: Benefits, How It Works, and What Changes After Deployment

What is Akamai?

Akamai is a general term for the group of services offered by Akamai Technologies, Inc., which provides one of the world’s largest content delivery networks (CDNs).

By utilizing the cache function of the edge servers provided by Akamai, it is possible to achieve high-speed delivery of web content and reduce system load. Although it is not very noticeable to general users, many companies have adopted Akamai and it is an important presence supporting modern web infrastructure.

In fact, when an Akamai failure occurs, it can have a wide-ranging impact, and a large-scale failure occurred in 2021. The system I am in charge of has also been affected by this experience, and I have once again realized the importance of understanding how Akamai works and its role.
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Flow of content distribution with cache data

When Akamai is deployed, content is cached on Akamai’s edge servers and delivered to users from the cache. This reduces the frequency of access to the origin server and significantly reduces server load.

Below is the access flow when content is cached on Akamai’s edge servers.

1. When a user accesses a URL to use a service, it sends a name resolution request to the local DNS server.
2. The local DNS server makes a name resolution request to a pre-configured DNS server (e.g. authoritative DNS).
3. This DNS server returns the CNAME record configured for Akamai.
   *The CNAME record for Akamai must be registered in DNS in advance.
4. The local DNS server sends a name resolution request to the Akamai DNS server specified by the CNAME.
5. The Akamai DNS server returns the IP address of the optimal Akamai edge server based on the location information and network conditions from the local DNS server (dynamic mapping function).
6. The local DNS server returns the IP address of the Akamai edge server it obtained to the user.
7. The user sends a request to the Akamai edge server.
8. If the edge server has cached the content, it returns the content to the user as is.

Flow of content distribution without cache data

Not all content is cached on Akamai’s edge servers. If there is no cache, the request is forwarded to the origin server (a server built on the system side) and the content must be obtained from there.

The following diagram illustrates the processing flow when there is no cache on the Akamai edge server. Steps 1 to 7 are the same as when there is a cache.

1. When a user accesses a URL to use a service, it sends a name resolution request to the local DNS server.
2. The local DNS server makes a name resolution request to a pre-configured DNS server (e.g. authoritative DNS).
3. This DNS server returns the CNAME record configured for Akamai.
   *The CNAME record for Akamai must be registered in DNS in advance.
4. The local DNS server sends a name resolution request to the Akamai DNS server specified by the CNAME.
5. The Akamai DNS server returns the IP address of the optimal Akamai edge server based on the location information and network conditions from the local DNS server (dynamic mapping function).
6. The local DNS server returns the IP address of the Akamai edge server it obtained to the user.
7. The user sends a request to the Akamai edge server.
8. If the Akamai Edge server does not have a cache of the content, it will send a name resolution request to the origin server (such as a web server provided by the system).
9. The DNS server returns the IP address of the origin server.
10. The Akamai Edge server sends a request to the origin server using the obtained IP address.
11. The origin server returns a response (content) to the request to the Akamai Edge server.
12. The Akamai Edge server delivers the content to the user.

Can Akamai Edge servers be fixed?

The Akamai edge server that a user accesses is automatically selected to be optimal depending on the user’s location. When Akamai is introduced, the DNS TTL (Time To Live) value can be set, and if the TTL is short, it is possible to maintain access to the same edge server for a certain period of time. However, the system must be designed with the assumption that the edge server accessed by the user will change.

On the other hand, from a security perspective, there are also systems that have requirements such as “limiting the edge servers that can access the origin server.” In such cases, by using Akamai’s SiteShield function, it is possible to fix the edge server that accesses the origin server for a certain period of time. However, please note that when the edge server is changed, it is necessary to update the access control settings such as firewalls.

Behavior when an Akamai Edge server fails

If an Akamai edge server fails, the server is automatically isolated and requests are diverted to another edge server that is operating normally. Akamai distributes edge servers around the world, achieving extremely high availability.

Behavior when a fault occurs between the Akamai Edge server and the origin server

If a communication failure occurs between the Akamai edge server and the origin server, users will be unable to access the origin server. In such a case, the Akamai edge server will fail over to the Akamai Storage Contents server and display alternative content (such as a Sorry page).

Summary

In summary, implementing Akamai CDN can significantly improve your website’s performance, scalability, and security. By offloading traffic to Edge servers and optimizing content delivery, Akamai ensures a faster and more reliable user experience. Understanding how it works and what changes occur post-deployment allows you to make the most of its capabilities. If you’re aiming for better speed, reduced latency, and enhanced resilience, Akamai CDN is a solid solution worth considering.