WiFi Multicast Benefits, Problems, and Mitigation Strategies

When a WiFi network uses multicast transmission it can send the same data to multiple client devices at the same time. This might sound like an obvious time-saver, but when too many devices are configured to send traffic this way, the network can become congested.

To avoid these problems, IT and network professionals need complete visibility into network performance and proactive alerts at the first sign of an issue.

Understanding WiFi Multicast

Multicast works with groups of devices. The sender of the data, such as an AP, won’t identify a unique device, but will instead send the traffic out to the multicast address, which consists of a certain group of recipient devices. If the devices are located along different network paths, the data is duplicated and forwarded along every necessary path. 

A few real-world use cases include:

• Audio/video streaming 
  • This includes everything from streaming during a conference, educational streaming in remote or hybrid classrooms, entertainment streaming, or an organization streaming security footage to multiple users at a time. 
• Advertising and discovering services on a network
• Performing large-scale system updates and management
• Providing real-time stock market updates
• Mobile commerce applications

The other communication options are unicast and broadcast. They differ from multicast in this way:

• Unicast is from one device on the network to another device
• Broadcast is from one device on the network to all devices on the network
• Multicast is from one network device to many other devices, but not all

Benefits of multicast for WiFi networks

Multicast has a few benefits including improved network efficiency and bandwidth utilization, and reduced network congestion. Together, this results in a network with overall improved performance and reliability,

How does multicast do this? Think of some of the real-world use cases mentioned above. If an organization needs to stream the same video content to ten or more devices, or update 500+ devices with the same upgrade, it has a few options:

1. Use unicast and send the same large data packets multiple times
2. Use broadcast and send the packets to all devices, including many that don’t want it or need it and will not be ready to receive it
3. Use multicast to send the data once to all relevant devices

You can see that multicast is the best option. Unicast and broadcast would see the network quickly overrun. Duplicate data packets would hog the bandwidth, congest the network, and lead to high latency and poor performance for all users.

Problems with multicast traffic

With that said, multicast isn’t problem free. Here are the problems that can arise when using it:

• Slower throughput: multicast traffic has to be sent at a data rate that works for all receiving devices. This can mean using a lower data rate, which slows down throughput.
• Less available bandwidth: multicast needs more airtime when transmitting, which leaves less bandwidth available for other clients
• Problems with “powersave” mode: if any multicast clients are in powersave mode when the data is transmitted, the AP will have to buffer the traffic. Buffered data is transmitted on a periodic interval known as the DTIM. This leads to bursts of traffic on the network. Buffered traffic is prioritized over all other traffic, so it essentially blocks everything else while it’s being sent.

9 possible mitigation strategies

There are a few different methods that can be used to resolve or remediate multicast issues. They are:

1. Make smaller broadcast domains
2. Use multicast to unicast conversion (if available with your AP vendor)
3. Increase the multicast transmit rate (use cautiously)
4. Use a dynamic multicast rate adjustment (if available with your AP vendor)
5. Dynamically adjust channel width for multicast transmissions (must be used in conjunction with #3 and #4, and depends on AP vendor)
6. Have AP implement Address Resolution Protocol (ARP) proxy and ARP suppression
7. Use Bonjour traffic suppression via Bonjour Gateway and/or an AP vendor-specific solution
8. Connect fixed devices using multicast-based discovery mechanism via wired networks
9. Disable peer-to-peer communication

Each of these methods helps prevent the network from being disrupted by too much multicast traffic. The right method will depend on a specific network’s configuration, AP vendors, and how much multicast traffic exists.

Wifi automation and how it can improve the efficiency of WiFi multicast

An AI-powered WiFi automation platform will automatically deliver complete network visibility 24/7, proactively alert IT to issues, and track performance and traffic trends over time. With this support, IT professionals have detailed insight into:

• How much multicast traffic is on their network
• How multicast affects network performance
• How performance changed after a mitigation strategy was implemented
• If a suppression method is necessary
• If the suppression method was successful
• What essential capacity planning must be done for the future

With these insights, organizations can design, implement, and maintain optimized, reliable networks now and into the future. For more information on AI-powered WiFi automation platforms, click here.