What is Multicast?

Multicast is a one-to-many and many-to-many communication protocol that reduces network traffic when transmitting large amounts of data. Bandwidth optimization occurs because it delivers one single version of a data file, such as a live video stream, to hundreds or thousands of users simultaneously.

In contrast, unicast is a one-to-one protocol that requires an individual copy of a data file be sent to each user. Unicast uses n times the amount of bandwidth as multicast, where n equals the number of users requesting the file.

In a multicast architecture, senders and receivers belonging to a group use a single destination IP address to communicate. The network, with multicast capabilities enabled on the routers and switches, is responsible for delivering packets from any sender in the group simultaneously to all the receivers.

Multicast has been around for more than 40 years. It’s  a proven technology and many enterprises continue to rely on it to efficiently distribute large amounts of data. With the demise of Adobe Flash as a preferred streaming video solution, the widespread availability of multicast clients that were part of Flash has also disappeared.

But as video rapidly displaces other forms of business communication, multicast enterprise content delivery networks (eCDN) are in high demand. Now more than ever, the future of multicast is strong. It’s the backbone of a number of modern and emerging real-time communication standards including WebRTC and HTTP/3.


In computer networking, multicast is group communication where data transmission is addressed to a group of destination computers simultaneously. Multicast can be one-to-many or many-to-many distribution.

Wikipedia

When to use a multicast eCDN

You might be asking yourself, “How do I know which eCDN is right for my enterprise?” Of course, you have a number of factors to consider when choosing an eCDN. Below are the prime use cases for a multicast eCDN.  

  • You have a multicast network
  • Live streaming events are a priority
  • Security is paramount
  • You want network stability and predictability
  • You rely on Wi-Fi

To learn more about the different types of eCDNs, read our guide to selecting the right eCDN.


How multicast works

When it comes to streaming video, the purpose of a multicast eCDN is to make video playable in a browser using the protocol. This process uses two software components to distribute video instead of using the HTTP transport layer.  

A sender sits on the network to retrieve live HLS or DASH video streams from the video source, encapsulate them in a multicast transport mechanism, and send them out over the multicast-enabled network.

Viewing devices on the network, such as personal computers, host a receiver client that is capable of tapping into the multicast broadcast. When the video reaches the viewing device, the receiver unencapsulates it and makes it available to the video player in the browser.

multicast architecture

What makes multicast so efficient

A multicast eCDN only sends traffic to subnets with active receivers (clients requesting the content). Therefore, in a very large network, the traffic does not traverse all network segments, but only the segments needed to ensure all group members receive the traffic.

In addition, multicast sends only one copy of the data on each network segment, and every multicast-enabled router and switch sends the traffic only to segments that have active multicast group members. Even if multiple receivers are on a segment, only one copy of the data is sent. All members receive and read that same copy.


Strengths and weaknesses

Multicast is a robust delivery option for live streaming. As a network protocol, it is highly deterministic, scales infinitely and is especially applicable for large enterprises. It is by far the most efficient and reliable eCDN available today.

Despite being a fundamental part of IP networks for decades, multicast may require some configuration on your network routers and switches, as well as Wi-Fi network. But given its ubiquity, this configuration is well understood and not complex. Today, you must install client software installed on the receiving devices. But modern communication technologies will soon integrate multicast capabilities into standard browsers. Finally, users may experience slightly slower start times for video than they will with either video caching or P2P because it is based on a push architecture.

multicast advantages

Ramp’s next-generation Multicast+

Ramp Multicast+ is a next-generation eCDN that overlays your existing network infrastructure to deliver high-quality, stable video to all your viewers. You can easily install our lightweight, software solution on existing infrastructure. So, you don’t need to upgrade your network or buy proprietary hardware.

Ramp Multicast+ is the only vendor-neutral solution for HLS and DASH video. Once deployed, you can use it to distribute video from any and all streaming platforms in use in your enterprise. And because it is deployed 100% behind the firewall, you have total control over your eCDN environment. In addition, we’ve built-in security controls to prevent unauthorized access to your videos and technologies like our patented forward error correction to create an optimal viewer experience.

  • Predictable, deterministic video delivery network
  • Supports any HTML5 browser-based video player
  • Only direct replacement for legacy solutions
  • Secure: Deploys 100% behind the firewall with end-to-end video encryption
  • Event simulations to silently test your network before live events
  • Best eCDN for live video over Wi-Fi
  • Patented forward error correction and bandwidth smoothing technologies
  • High-availability with heartbeat monitoring
  • Centralized management, monitoring and insightful event analytics
  • DVR capability allows users to pause and time slip video playback

You can learn more about Ramp Multicast+ by reading our solution brief and technical white paper.