multicastStreaming video is content that can be accessed by the viewer without having to wait for the entire video to download to a hard drive. The name comes from the fact that the video is sent in a “stream” that is played as it arrives at its destination. Long wait times while large videos download to a hard drive to be played are gone with streaming. At TikiLIVE, we provide streaming solutions for HD video.

Unicast and Multicast are two methods of streaming video over the Internet. Unicast is a point-to-point protocol where information is sent from one device to another. This is the primary method of sending files and information over Local Area Networks (LANs) and most of the Internet. It usually uses what is known as the Transmission Control Protocol (TCP). Device A sends the data directly to Device B. If Device C also wants the data, Device A will send the data directly to Device C, even if Device B is being sent the data separately at the same time.

Multicast is where information is sent once from a receiver to multiple delivery points and requires the User Datagram Protocol (UDP). UDP uses less overhead than TCP and transmits data faster. Device A sends the data out, typically to a switch. If Device B and C want the data, they “join” the switch to receive that single data stream coming from Device A. Device A does not send Device B and Device C their own signal, B and C tap into the one signal sent from A.

How Do They Work?

Unicast is easy to use and usually doesn’t require anything extra to be done to a network to function. It is a method that goes from one IP address to another, so it is based on where the content is going. It is a connection protocol. If the video to be streamed is going to go to a user, it goes from the sending device to that user. If another user wants to view that video, a separate iteration of that video is sent to the second user.

Multicasting is what is known as a connectionless protocol. It really doesn’t care where data is sent, or if it even gets to its destination. Multicasting may require some network configuration, as special addressing must be used. The end user has chosen to receive the video before it has been streamed. The video is sent one time from the sending device and all the devices that have been set to receive the stream also get the video. Devices that are not set to receive the stream do not get that traffic. In a way it is similar to cable TV. The signal is sent out from the head end and if you have the right cable package and tune into that channel, you can get the video. If you don’t have the proper package or are on a different channel, that signal isn’t delivered to you.

As a side note, broadcasting is similar to multicasting in that the packet is sent once to all devices in a given range, but it is sent to all the devices whether they want it or not. Your device has to determine if you want the packet or not for all the packets being broadcast. This obviously isn’t practical for the Internet as a whole and is usually limited to local subnets of a network, especially since most routers will block IP broadcast traffic by default.

Why Would You Use Unicast or Multicast?

For On Demand video or video that will be streamed at a user’s convenience, unicasting makes sense. It is easier to use, the user has control over the stream (e.g., bitrate and play-pause-stop), and is more reliable. YouTube is an example of a service that uses unicasting. Generally, there will not be so many users accessing a video at once that the system becomes overloaded from separate streams being sent to each viewer.

Unicast uses too much bandwidth for live events, or other events where a large number of users would be accessing the data. Every person that accesses the video would be getting a separate stream with its own bandwidth overhead. Multicasting takes care of that by streaming the video once to all the devices that have opted to receive the stream. Multicasting is very efficient in this regard. As previously mentioned, since it uses UDP, which is a simpler protocol, multicasting is delivered faster and it is better suited for streaming video.

What Are the Disadvantages of Multicasting and Unicast Streaming?

We alluded to one disadvantage of unicasting above. Unicasting does not scale well. If there are a large number of users accessing the stream at the same time, bandwidth becomes an issue. TCP sends data in the packets that ensures the data gets to where it is being sent. When data slows from traffic or from the signal being checked for error loss, buffering happens on the unicast stream. This is irritating when watching streaming content, but can ruin a conference call or a live event.

Multicasting handles bandwidth overhead very well, but with UDP there are no recovery options. Nor is there any guarantee that the packets will reach where they are intended. It is up to the receiving device to do any error checking. This can result in lost packets or dropout. Multicasting also requires routers and ISPs that support multitasking; not all do so. It is also more difficult to multicast over a large number of different networks, switches, and routers because of the complexity of delivering multicast streamed content.

Why does it Matter?

At TikiLIVE we have the software, encoding options, and infrastructure to provide the option that works best for you. As you can see, both unicasting and multicasting have advantages and disadvantages. If your video is not delivered reliably and with quality, your reputation and potential monetary bottom line can be affected.

We are committed to providing the answers and solutions you require. Our highly trained customer support staff can tailor the streaming method specifically to fit your needs. Please contact us today! You can also feel free to explore our knowledge base, open a support ticket, or chat online with one of our customer service experts. If you prefer, you can also call us at 305-289-4557.