Communication between network devices can occur in different ways. In this video, you’ll learn the difference between unicasts, multicasts, anycasts, and broadcasts.
A unicast is one of the more popular ways of sending information across the network. It is when one station sends information directly to another station. This is a one-to-one relationship and nothing within that conversation is ever sent to anyone else on the network. If you need two devices to be able to send information to each other and no other device on the network will be involved with that conversation, then you’re probably using a unicast. So any time you’re connecting to a website, you’re transferring files, or you’re checking your email, it’s probably all taking place with a unicast communication.
This one-to-one relationship is also one of the disadvantages of unicast, especially if you need to send information to many people simultaneously. With unicast, you would have to build separate one-to-one communications with all of those individuals and you would have to send separate data for each individual device. But for single communication between you and another device, whether using IPv4 or IPv6, you’re probably going to use unicast.
To be able to efficiently send data to multiple devices at the same time, then you’ll probably want to use multicast. Unicast is a one-to-many-of-many communication. So when you send information out, it is sent to multiple recipients all simultaneously. These recipients are usually subscribing to your multicast feed. So if someone is trying to receive multimedia, they’re receiving stock exchange information, or maybe a device is sending out routing updates, it can send those out via multicast addresses.
Multicast is relatively specialized and it requires that equipment understand and recognize how to deal with multicast communication. This is why we don’t use multicast when we’re sending information across to a different network or even within a very large network. But we do use multicast quite a bit with IPv4 four and IPv6. And in the right environment, it can be a very efficient way to send and receive traffic.
Multicast is used where one device needs to send to many devices. Anycast is used when one device needs to send to one of many devices. This is where a single destination IP address may be sent to one of many different devices that are on the network. And it’s something that you’ll commonly find with both IPv4 and IPv6.
In this scenario, the devices that are receiving the anycast communication are all configured in very similar ways. This allows the originating device to simply send data to the unicast address and whatever device is closest is going to receive that traffic. A good use case for anycast would be something like anycast DNS, where a DNS query can be sent out on the network and the closest data center will be able to respond to that anycast DNS request.
And if you want to send a frame to everyone who’s on your network, then you’ll want to send a broadcast. This is a one-to-all relationship where a single packet is sent out and everyone on the network receives that single packet. Fortunately, the scope of this is limited to your local broadcast domain. So there’s no way to send a broadcast frame from your local network and somehow have that frame appear everywhere else on the internet.
This is a type of communication that’s best fit for something like routing updates or ARP requests. And although this is something that you will commonly find with IPv4, we decided with IPv6 to remove broadcast completely and go to a multicast form of communication instead.