Anycast is a network routing and addressing method where incoming requests can be routed to multiple locations or 'nodes'.

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Anycast, when utilized in CDN applications, typically directs traffic to the closest data center, leveraging its highly efficient request handling capabilities. The inclusion of selective routing ensures compatibility for any network incorporating Anycast, even during unforeseen traffic surges, network congestion, or DDoS attacks.

CDNs are large-scale networks that are incorporating Anycast worldwide. When providing a CDN service to local Internet service providers (ISPs), multiple access points are available for them to select the shortest path. Opting for shorter routes ensures quicker connection times for website visitors.

How does Anycast work?

Anycast's network routing capabilities allow for incoming connection requests to be sent through multiple data centers.

When requests are sent to a single IP address associated with an Anycast network, the network will distribute data based on prioritized methods. The selection process behind choosing a specific data center is typically optimized to minimize latency by selecting the data center with the shortest distance from the accessing requester.

Anycast is used as a specific one-to-one connection method by numerous network engineering associations, and is one of the five main connection methods used in the Internet protocol.

Why use Anycast?

If multiple access requests are made concurrently to the same cloud origin server, it may become overloaded with heavy traffic and be unable to effectively respond to subsequent additional requests.

With the assistance of Anycast, instead of the original cloud server alone bearing the traffic burden, this load can be distributed across other available data centers. Each cloud server will have supporting servers capable of processing and responding to incoming requests.

This routing method helps prevent the need for the cloud server to scale up, thereby avoiding service interruptions for customers requesting content from the cloud origin server.

The difference between Anycast and Unicast

Most networks on the Internet operate through a routing program called Unicast. In the Unicast protocol, every node on the network has a unique IP address. In home and office networks that use Unicast, when a computer is connected to a wireless network and receives a message stating that this IP address is already in use, an IP conflict occurs because another computer on the same Unicast network is already using that IP address. In most cases, this is not allowed to happen.

When a CDN uses Unicast addresses, the traffic is routed directly to specific nodes. This creates a vulnerable point when the network faces abnormal access traffic, such as during a DDoS attack.

Because the traffic is routed directly to a specific data center, location, or infrastructure, it can overload with this access traffic, leading to the risk of service denial for legitimate requests.

Meanwhile, using Anycast implies a highly flexible network. In this case, the access traffic will find the best path, and the entire data center can be taken offline while the access traffic automatically shifts to a nearby data center.

How Anycast reduces the risk of a DDoS attack

After other DDoS defense tools filter out some attack-oriented access traffic, Anycast distributes the remaining attack traffic across multiple data centers, preventing any specific location from being overwhelmed with access requests. If the capacity of the Anycast network can handle the attack traffic, the effectiveness of the DDoS attack is significantly minimized.

In most DDoS attacks, multiple compromised "zombie" or "bot" computers are used to form a botnet. These devices can be distributed across the web, generating a substantial amount of access traffic that can overwhelm a typical Unicast-based model.

A properly integrated Anycast-enabled CDN system increases the resilience of the receiving network, allowing unfiltered DDoS attack traffic, such as that from a botnet mentioned earlier, to be distributed across each data center of the CDN. As a result, as a CDN network continues to grow in size and capacity, it becomes highly resistant to DDoS attacks and minimizes damage.

It is not an easy task to establish a properly standardized Anycast-integrated network. Implementing the correct procedures requires the CDN provider to maintain their own network hardware, establish direct relationships with their upstream providers, and fine-tune network routes to ensure that access traffic does not "fluctuate" between different locations. VINADATA's CDN service is a safe and reliable choice, with a well-integrated Anycast implementation.