What’s the Difference between Multicast vs. Unicast?

Blog 5 min read | Oct 27, 2023 | JW Player


Whether it’s sending data packets across the internet or distributing information within a local network, two common communication methods are employed: multicast and unicast.

Both methods have their advantages and disadvantages, and choosing the right one depends on the specific use case and network requirements. This article focuses on the multicast vs. unicast debate, listing the characteristics, applications, and pros and cons of each.

Unicast communication

Unicast, or a one-to-one connection, is the most common method of data communication. It uses TCP (Transmission Control Protocol) to send data packets from one source to one specific destination. Think of it as a private phone call – the message goes directly to the intended recipient without broadcasting to multiple recipients.

Namely, when an OTT app broadcasts a live event, it uses an origin server to distribute content live to each individual viewer. Therefore, there is a single connection between each user’s device and the origin server. However, unicast streaming happens over the internet, which can cause interruptions while delivering large amounts of live streams. This is why broadcasters use content delivery networks (CDNs) for easier distribution over the internet.

Applications of unicast

  • Point-to-point communication: Unicast is ideal for scenarios where a single source needs to transmit data to a single receiver. This can include typical internet browsing, email exchanges, and video conferencing.
  • OTT: Unicast communication is optimal for VOD (video-on-demand) content. OTT (over-the-top) apps and streaming services use unicast to deliver video content to various devices.
  • Reliable data delivery: Unicast guarantees that the data reaches its intended destination. In cases where data integrity is crucial, such as financial transactions or critical system updates, unicast is preferred.

Pros of unicast

  • Precise targeting: Unicast is perfect for individualized communication, ensuring that the message reaches the exact recipient it was intended for.
  • Data reliability: Unicast communication is highly reliable since data packets are dedicated to a single recipient, reducing the risk of data loss or interference.
  • Scalability: Unicast can be efficiently used in small-scale networks or when one-to-one communication is necessary.

Cons of unicast

  • Inefficient for large-scale broadcasting: When the same data needs to be sent to multiple recipients, unicast becomes inefficient, as it would require duplicating data packets for each recipient.

Multicast communication

Unlike unicast, a multicast connection sends data to multiple recipients in one go. In a multicast system, a single source transmits data to a designated group of recipients, rather than sending separate copies to each individual, saving bandwidth and reducing network load.

Namely, multicast relies on UDP (User Datagram Protocol) to deliver a live stream across a local area network (LAN) or an IP service provider’s private network. Streaming live television using a multicast connection is also known as IPTV.

Basically, the sender only distributes a single stream, which the network nodes then send throughout the whole network. Multicast communication doesn’t overload the network with streams, so it is a go-to video streaming choice for large companies.

Applications of multicast

  • Live Streaming: Multicast is perfect for live streaming events, webinars, or video conferences to a large audience, as it enables efficient one-to-many communication.
  • Software Updates: When distributing software updates or patches to a group of devices within a network, multicast ensures efficient and faster delivery without overwhelming the network.

Pros of multicast

  • Network efficiency: Multicast conserves bandwidth and reduces network congestion, as data is transmitted once and received by multiple devices interested in that data stream.
  • Scalability: Multicast is highly scalable, making it suitable for large networks with a significant number of recipients.
  • Real-time communication: Multicast is the go-to choice for real-time applications, as it minimizes latency and ensures synchronized delivery to all recipients.

Cons of multicast

  • Limited internet support: Multicast isn’t widely supported on the public internet due to the complexity of routing and security concerns. It’s primarily used in local or private networks.
  • Requires special routing: To implement multicast, specialized routing protocols and network configurations are necessary, making it more complex to set up compared to unicast.

Multicast vs. Unicast vs. Broadcast

Multicast, unicast, and broadcast are three methods of data communication in networking, each with distinct characteristics and applications.

Unicast represents one-to-one communication, ensuring that data is sent from a single source to a specific recipient. It’s ideal for point-to-point exchanges where precision and reliability are paramount.

Contrastingly, multicast facilitates one-to-many communication by sending data from a single source to a group of recipients. This method preserves bandwidth, reduces network load, and finds use in live streaming, software updates, and real-time applications.

On the other hand, broadcast transmits data from one source to all devices on a network, similar to a public announcement. It’s used primarily in local networks to spread information widely, although it can lead to network congestion if not managed properly.

Ultimately, the choice between multicast, unicast, and broadcast depends on the specific use case and network requirements, with each method offering a unique solution to different communication needs.

Final Thoughts

The choice between multicast and unicast communication depends on the specific needs of your network and the intended use case. Unicast is the go-to method for one-to-one communication where reliability and precision are essential.

Conversely, multicast is the preferred choice for efficiently delivering data to multiple recipients in a one-to-many scenario, reducing network load and enabling real-time communication.

In practice, many networks use a combination of both unicast and multicast to meet their diverse communication requirements. The key is to understand the strengths and weaknesses of each method and implement them strategically to optimize network performance and resource utilization.