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What is Anycast and how does it work?

The internet today has evolved both in structure and speed; it continually undergoes optimization to give the users the best and the fastest results they can get in their respective location. Technically, there are quite a number of processes that go into computer network requests, data sourcing and server response. The computer sends a request to the server that has the necessary data, the server – in that split second – filters through the billions of electronic data on the internet database to provide a list of responses that best match the requests. So, considering the number of checks, send and verification processes (due to the cyber security) your network request has to go through, how exactly do we get such fast responses?

One of the means to that end is a network protocol dubbed as “Anycast

What is Anycast and how does it work?

What is Anycast?

Anycast is a network protocol (it could also be called a process) that routes network packets/ incoming connection requests/ network traffic to different destinations (nodes). What this does is to reduce the load on a particular network node and by consequence reduce the lag time of server response and allow an overall smooth internet experience for users.

It is a method of addressing the network flow on the internet. The servers involved are made to share the same Internet protocol address, so that each of those servers is positioned to send in the necessary data to the computer closest to them. In essence, it leverages on the proximity of predetermined network topography to distribute requests and corresponding responses across servers and computers respectively.

what is Anycast

Why Use an Anycast Network?

Every server applies various limitations to its end-users and incoming requests in order to avoid intrusion and cyber attacks. So, if one system/server forwards multiple requests to the same origin server, its traffic may appear suspicious to the receipt server.

Multiple requests may overwhelm the server and affect the response time or responses your end-users will get for the next requests. There may be a time when all their requests are discarded, and they do not receive any response at all. The problem will persist for the genuine requests too.

Anycast networks can be useful when more of your genuine users are facing this issue.

This type of network spreads the requests among the currently-available datacenters and ensures that traffic is served smoothly. As the same user’s different requests are now being processed on different origin servers, the problem is solved.

All servers in an anycast network have the same processing capability and response speed, so the end-users won’t be able to differentiate between them.

Routing of this sort can prevent unnecessary interruptions for the end-users while balancing the workload for the network’s server machines.

How does Anycast Work?

Primarily, anycast is designed to address the issues of traffic overload and browsing latency. In simpler terms, it works on three main principles; grouping, positioning and priority.

Grouping – In an anycast network, different servers are made to share a single IP address. That way, all the requests sent are distributed between the different servers sharing that unique IP address.

Positioning – The network structure of an anycast protocol is designed in such a way that, different networks from different locations have separate servers positioned near them just in case of a connection request.

Priority – This is the fundamental underlying principle behind the anycast idea. The requests coming from the computers are assigned on the servers in the anycast network. However, the servers are chosen based on a system of priority. The key priority factor in server selection is computer – server proximity. The network sends the request to the nearest server (with a well-positioned network topography) to reduce the lag time in server response.  

Apart from the Anycast method, there are series of addressing methods that are employed on the internet. Let’s examine some of these methods and see the possible relationship they may share with Anycast method:

  1. Unicast Addressing Method

This is the most widely used addressing method on the internet today. The underlying principle of this is to establish a connection between a single computer and a single server. When a request is made, the unicast network connects the computer by sending the requests to a single server (or another computer) as the case may be and establishes a secure connection between them. A practical example would be when you make a phone call. Apart from when you intentionally design the call to be a conference call; there are only two ends to the connection: the caller and the receiver. Other very common examples of situations where the unicast method is employed include the Email dispatch system, downloading and uploading files directly to the internet (maybe to a website or cloud storage) etcetera.

Unicast Addressing Method

Just like in the case of the phone call, the unicast system works with specificity. Irrespective of the location or the kind of system you are sending your requests from, once you send a request to a specific address on a unicast network, the internet connects you directly to the specific server in question. It efficiently uses the IP addresses of the target server to route any connection requests directed at that specific address. This method is the best when it comes to maintaining the security of the data packet and the network routes. Its specificity makes it almost impenetrable to external influence. However, this method has a somewhat inherent down side; it is useless when it comes to sending data to multiple servers. It would end up consuming the whole network bandwidth if attempted.

  1. Multicast Addressing Method

As efficient as the unicasting method may seem (let’s say in the telephone context), think of the possibility of using the same method for a different end. In this case, the goal is to connect with multiple users (or let’s say computers) through a single source. Now imagine attempting to establish a one-to-one connection with each of the computers. Let’s attach a numerical value to that, let’s say hundred. The consequences of that are first; waste of time and second, possible exhaustion of the network bandwidth. This is where the Multicast system comes in.

Multicast Addressing Method

The multicast system is a network addressing method that routes connection requests to multiple servers simultaneously.  When a computer sends a request, the multicast system automatically routes it to the different servers .Think of it like some sort of streaming, but from devices to different servers instead. This method is the best when it comes to sending large packets of data to a specific group of servers or computers. On the flip side, it can be difficult to structure and it cannot be executed using the IPV4 addressing.  Due to its complexity, it is often time consuming to create a multicast network and select specific nodes.

  1. Broadcast Addressing Method

Broadcast addressing method is the less specific, more general method of connection routing.  It uses the same principles as multicast addressing method; the only difference between these methods is that the broadcast addressing method is not specific. It is structured in such a way that, all available nodes in a network has access to the data packets sent from any device within the range of the same network. The disadvantage of this method is that it places unnecessary burden on a network route. Also, this method makes it easy for attackers to perpetrate a volumetric distributed denial of service attack. However, when it comes to getting datagram across to different servers or computers, the broadcast addressing method is the best. Finally, it is the easiest tom implement among all the network addressing methods.

Broadcast Addressing Method

Broadcast addressing methods are of two types: limited and direct. Limited broadcasting methods are designed to route connection to the servers/computers within a predetermined network. The Direct broadcast addressing method is not restricted to any set of network or server.

What Are The Differences Between Anycast And Unicast Addressing Method

When we consider specificity and safety, anycast and unicast addressing methods are the two most promising addressing methods. There are quite a number of differences between these structures. They are very distinct by the number of servers in use, the mode of operation and the purpose of usage. Let’s consider some of the differences between them.

  1. SERVER SPECIFICITY – The unicast system routes a connection request to a predetermined specific server or computer. What this implies is that, no other server has the capability of receiving the datagram for the other. The anycast addressing method on the other hand does not have a specific server structured to receive the connection requests. It is designed to choose server based on traffic, network topography and proximity especially.
  1. SUSCEPTIBILTY TO ATTACK - Both anycast and unicast methods are safe and resistant to attacks. Unicast attacks are very useful when it comes to data security and privacy. However, they may inherently pose a problem to other servers in the same network as they are very prone to a volumetric distributed denial of service attack. The anycast method on the other hand is the perfect against DDOS attacks because it automatically finds alternative servers for connection requests. That implies that, servers are less likely to be victims of attacks from an influx of request.
  1. EASE OF SETUP – Due to the extra step of finding a proximal server, an anycast structure may be more complex to setup than the unicast method. The unicast method is very straightforward; it is directly from the computer to the server.  
The Differences Between Anycast And Unicast

However, on the flip side, they are a number of similarities between these two network addressing methods than the rest.  Both methods route to the connection requests to just one server instead of multiple servers (like the broadcast and multicast methods). Furthermore, both systems save more time and reduce lag periods in server method. The unicast method does this by addressing the requests to a specific server, the anycast method, by quickly finding an alternate server. Either way, lesser time is spent than in then multicast and unicast system.

What Do You Need The Anycast Method

Compared to the other methods of addressing network, Anycast has huge comparative advantages.  Essentially, it is the way forward out of the technical quagmire that unicast, multicast and broadcast systems may put the users, the server or the whole network into. Let’s consider some of the reason why you should consider using the anycast method;

  1. This method allows faster internet use when compared to others – Due to the mode of operation of the anycast system; it increases the response rate of the server (or the destination computer) faster than any network addressing system available. For instance, the multicast system may prove to be slower because of huge traffic that may flow on a single route. The unicast system on the other hand has to find and secure one connection despite the distance.
  1. Lesser susceptibility to a distributed denial of service attack – The anycast method (like we have discussed earlier) makes a network-server connection more resilient to the attempts of cyber criminals to render it non-functional.  A brief look into the details would explain better. The design of the multicast and the broadcast system is meant to support transmission of data packets to multiple servers at the same time. Cyber attackers often take advantage of this open to hijack the connection route and over flood the server with illegitimate connection requests (or datagram). This consequently puts the server out of service. It is known as a volumetric DDOS attack. The anycast system provides immediate alternatives to the overloaded server and allows over ones to solve the same problem within the same time frame. This relieves all server of comparatively large work load and makes them more resistant to DDOS attacks. On the same note, the Unicast method – though designed for a single computer and a single server – may place an unnecessary burden of requests on other server in the network. This may cause them to cave in to pressure and become nonfunctional.
  1. It can deflect route hijack attacks – The unicast system offers a relatively safe and straight forward structure of connectivity. However, nothing is fool proof. Once the security is broken and the route has been hijacked, the attackers can manipulate the connection at will; conduct various one-to-one transmissions with the sole goal of bandwidth exhaustion.  The quick ability to seek an alternative puts the anycast method at a huge advantage in this case. One route doesn’t affect the other; it is made to find another one that is nearer and more efficient to carry out the network issued command.
  1. It is relatively easier to setup – The anycast system is comparatively easier to set up. This is particularly true when we consider the types of the multicast and broadcast systems, and the corresponding complexity.
all method


The anycast method reflects the solid principle of division of labor. Not just that, efficient division of labor – let the best server carry it out. It is the most viable method for users (when it comes to speed and safety), and the servers (when it comes to workload efficiency).  It is important that any professional considering a network setup of any sorts adopts this method, or puts it into the list of the most feasible alternatives.



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February 26, 2024
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