Anycast is a network addressing and routing method in which incoming requests can be routed to various locations or “nodes.” In the context of a content delivery network
(CDN), anycast typically routes incoming traffic to the nearest data center with the capacity to process the request efficiently.
Anycast is a technique for distributing incoming traffic across multiple data centers within a CDN. When a user requests a website, the request is directed to the nearest data center that can efficiently process it. This selective routing ensures the content is delivered faster, reducing latency and improving the overall user experience.
In the context of CDNs, Anycast is particularly useful for handling high traffic volumes, network congestion, and DDoS attacks. By distributing traffic across multiple data centers, anycast ensures that no single server or data center becomes overwhelmed, preventing service interruptions and maintaining the availability of content.
Anycast routing operates by associating multiple data centers with a single IP address. When a request is received, the anycast network determines the optimal data center to process the request based on various factors, such as network latency and proximity. The goal is to choose the data center that is closest to the requester, minimizing the distance the data needs to travel.
Using an anycast network offers several benefits, especially in the context of CDNs. Here are some advantages:
Anycast routing improves performance and reduces latency. Directing traffic to the nearest data center minimizes the distance data needs to travel, resulting in faster content delivery. This is particularly important for websites and applications that require real-time data updates or have interactive elements.
Anycast enables load balancing across multiple data centers. Instead of overwhelming a single server or data center with high traffic volumes, requests can be distributed across available data centers, each equipped with servers capable of processing and responding to incoming requests. This load-balancing capability enhances scalability, ensuring that the network can handle increasing traffic demands without service interruptions.
One of the advantages of Anycast is its resilience against DDoS attacks. DDoS attacks involve overwhelming a target server or network with massive traffic, rendering it inaccessible to legitimate users. Anycast mitigates this risk by distributing the attack traffic across multiple data centers. Suppose the capacity of the anycast network exceeds the attack traffic. In that case, the attack can be effectively absorbed, ensuring the availability of services.
Read more: What is a DDoS attack?
DDoS attacks threaten online services, and CDNs are often targeted due to their function in content delivery. When a DDoS attack occurs, various mitigation tools filter out some of the attack traffic. Anycast then distributes the remaining attack traffic across multiple data centers, preventing any one location from becoming overwhelmed.
According to Cloudflare, “In most DDoS attacks, many compromised ‘zombie’ or ‘bot’ computers are used to form what is known as a botnet. These machines can be scattered around the web and generate so much traffic that they can overwhelm a typical Unicast-connected machine.
A properly Anycasted CDN increases the surface area of the receiving network so that the unfiltered denial-of-service traffic from a distributed botnet will be absorbed by each of the CDN’s data centers. As a result, as a network continues to grow in size and capacity it becomes harder and harder to launch an effective DDoS against anyone using the CDN.”
Related: What is a botnet?