What Is Multicasting?

Date First Published: 30th May 2022

Topic: Computer Networking

Subtopic: Data Transmission Technologies

Article Type: Computer Terms & Definitions

Difficulty Level: 5/10

Learn more about what multicasting in this article.

Multicasting is the sending of data across a network to multiple recipients or hosts at the same time across a LAN or WAN. It can be a one-to-many or many-to-many type of communication as one sender may send data to multiple recipients at the same time or multiple recipients may send data to multiple recipients. It is helpful for reducing the data frame of a network.

Note:

Sending an email to a mailing list is an example of multicasting, since mailing lists are a single email address that automatically forwards the email to all the addresses on the list.

IP multicasts describe multicasts that occur over the internet. This is because they make use of the Internet Protocol to send data. Multicast trees are created by IP multicasts since the single transmission branches out to multiple users. IP multicasting combines the features of the Internet Group Management Protocol (IGMP) and the Protocol Independent Stream (PIM). The Internet Group Management Protocol creates multicast trees and is used by routers. The Protocol Independent Stream is used to route the data to the correct system when a router receives a request to join a stream through IGMP.

Advantages and Disadvantages Of Multicasting

• It eliminates the need for data to be separately sent from the source to every recipient.
• It reduces the load on the network infrastructure.
• It uses bandwidth more efficiently. Since individual copies of data do not have to be sent to users at a time, it greatly reduces the required amount of bandwidth.

• It is incompatible with existing encryption. By default, multicasting does not use encryption. However, an alternative in multicast encryption is the use of symmetric key encryption. Data is decoded through the use of a traffic encryption key. Every time a member joins or leaves a group, the traffic encryption key is modified and it is not recommended for large groups. It is necessary for users to stay connected to obtain new keys. Asymmetric keys can be used to encrypt data. It is where a private key is shared asymmetrically. One member is given a share and one of them is passed to every group member. The message can be viewed if a member has a valid share of the key.
• It is not always reliable. Even though it is more reliable than unicasting, if one of the individual streams of data fails, multicasting will still fail. If one of the users on the network disconnects, the stream of data will not exist for the multicast group.
• There are limitations in terms of scalability. Multicasting can become inefficient when there are a large number of users connected. This is because more connected users will lead to less bandwidth for each user.

Differences Between Multicasting, Broadcasting, and Unicasting

Multicasting is different from broadcasting or unicasting. Broadcasting refers to the practice of sending messages to every host on a network without knowing their individual IP addresses. However, multicasting only sends data to a selected number of recipients or hosts at the same time and there is no defined number of them. Unicasting only sends data to a single recipient or host on a network. It has only one sender and recipient and is simpler than broadcasting or multicasting.