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The Different Forms of Streaming

Unicast v Multicast

Over the last decade, “streaming” has become a household term. We stream TV and movies from Netflix, all sorts of videos from YouTube, we even stream training at work and lectures at school. For most people all streaming is the same but behind the scenes a different story, starring unicast, multicast and broadcast unfolds. Each “character” in this streaming story provides similar results but the way they achieve those results is different.


Broadcast has been around for ages and isn’t usually associated with “streaming”. When we think streaming we generally think of the internet and when we think of broadcast we generally think of older technology, such as TV and Radio. Broadcast is more of the grandfather to unicast and multicast streaming and the way it works is quite simple. A broadcast is just what it sounds like, the signal reaches far and wide and is available to everyone. If you turn on the radio you are receiving a broadcast, if you get your TV over the air, via an antenna you are receiving a broadcast. You can broadcast within a private IP network as well and the result is quite similar. If your company broadcasts a town hall style meeting, every IP address on the network will receive the same meeting without having to “opt-in” to view it. This is a bit different than unicast and multicast.

Multicast sounds similar to broadcast in that there are multiple targets of the cast, or stream but there are differences. The main difference between multicast and broadcast is whether or not a user needs to opt-in to receive the stream; in broadcast there is no opt-in but in multicast there is. If the same town hall meeting mentioned above were streamed in a multicast environment users would have to click a link, or register to gain access to it. The registration tells the network that you are interested and have opted-in to view the stream. In a multicast environment the sender of the stream only sends one stream regardless of the number of interested users who have opted-in, this method of transmission is very cost effective from a bandwidth perspective when compared to unicast streaming. One drawback of multicast is that it can only be effectively utilized within a private network, making it far less popular than unicast.

Unicast streaming is undoubtedly the method of streaming you are most familiar with. Video on demand services such as Netflix, Amazon Prime, YouTube, etc. all utilize the unicast method of streaming. All networks within the internet support the unicast method of transmission which is why it is so popular. Unicast is defined by a single sender and a single receiver. Unicast can be extremely expensive from a bandwidth perspective because a unique stream is created by the sender for every unique receiver. If 10 people are watching a 1Mb stream in a unicast environment, the total cost of bandwidth is 10Mb, whereas if 10 people are watching a 1Mb stream in a multicast environment the total cost of bandwidth is just 1Mb.


So how can you use this knowledge to help your company? Generally speaking, it depends on how you want to use video. If you want to live stream training sessions or town hall meetings, multicast is the way to go. If you want to record training and allow employees to watch at their own pace you are going to use unicast. As long as you stay within the constraints of your bandwidth, your audience will never know the difference and that is what’s important. If you’ve been thinking about increasing your use of video or implementing a new system to handle video across your organization give us a shout, we love questions.

P.S.
Imagine how much bandwidth Google must have at their disposal to satisfy all of the unicast streaming through YouTube!


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