Airport: What is the Multicast Rate?

   Posted August 25, 2008 by David Kirk in Apple Mac

Scanning through the wireless options, many users wonder what the “multicast rate” setting is. For once, higher is not necessarily better. Keep reading to learn what your multicast rate should be.

Multicast Rate options include 1 Mbps, 2 Mbps, 5.5 Mbps, and 11 Mbps. The default is 2 Mbps. What is the best multicast rate?

First, a little background. Wireless efficiency is all about signal strength to noise ratios. More signal and less noise is best. Even if you have kicking high signal if there is a great deal of wireless noise, your connection still may be poor. Wireless noise is often increased by other electronic devices such as wireless phones and microwaves. The higher the noise the slower the communication between your wifi device and your wireless router. If these communications are slower, your wifi speed will be slower.

Tweaking your multicast rate is unlikely to improve your signal to noise ratio.

The multicast rate is the baseline level that a wifi device must be able to deliver in order to connect to the router. Lower multicast rates mean weaker, farther signals are allowed to connection. Higher multicast rates mean that only close, strong signals are allowed. Multicast is basically asking what’s the minimum quality that is needed to allow a device and your wifi router to maintain a connection.

Thus, turning up your multicast rate will decrease the effective range of your wifi network.

Typically, the default settings work well here. If you are in a very high device environment, you can increase this setting (to 5.5 or 11 Mbps) to decrease the range in which these devices will talk to your router.

If you are trying to increase the range of your router, decreasing the multicast rate (1 Mbps) will help. Just realize that at the edge of your range, the effective wifi speeds may be very slow because of the low signal to noise ratio.

In case you are having trouble finding this setting. Open your AirPort Utility. Click Manual Setup. With the Airport tab selected, next select the Wireless section tab. Then click the Wireless Options… button.


About David Kirk

David Kirk is one of the original founders of tech-recipes and is currently serving as editor-in-chief. Not only has he been crafting tutorials for over ten years, but in his other life he also enjoys taking care of critically ill patients as an ICU physician.
View more articles by David Kirk

The Conversation

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  • anonymous

    This article is a load of BS. Please dont misguide people.

  • Dan Moulding

    I have to wonder if you even know what multicast means. Multicast is a special category of data stream. The multicast rate option in Apple Airports only affects whether the Airport base station transmits *multicast streams*, given the data rate that currently connected clients support. If *no* connected client can maintain the selected data rate, then the base station simply does not transmit multicast streams. It has nothing to do with making, maintaining, or breaking the wireless connection, and in particular it has no effect on non-multicast traffic (i.e. the vast majority of data that flows over the typical wireless LAN). Telling people that lowering this value will increase their effective range is very misleading.

  • brenwah

    I’ll admit that I don’t know what multicast means. That said, this article is remarkably similar to what apple states multicast is. Here is what the airport manual states about multicast:

    “Multicast rate: Choose a multicast rate from the pop-up menu. If you set the
    multicast rate high, only clients on the network that are within range and can
    achieve the speed you set will receive transmissions.”

    Thus, it seems like the author does know what he/she is talking about.

    • Anonymous

      @brenwah: The Apple doc you refer to is unfortunately a little ambiguous. You need to keep in mind that the context of this doc is “Controlling the quality of audio and video streaming”. What do audio and video have to do with multicast? Those types of data transmissions often use multicast, instead of the more common unicast, in order to conserve overall available network bandwidth. When the Apple doc says “… only clients on the network that are within range and can achieve the speed you set will receive transmissions”, the transmissions its referring to are *multicast* (i.e. said audio and/or video) transmissions. Unicast transmissions (non-audio, non-video, i.e. just about *everything* else) will be transmitted regardless of the multicast rate setting.

      • Kmurray

        So do you think you could actually be degrading a wireless network, by setting multicast rates high? If you were trying to deter streaming audio/video traffic, isn’t it possible that your network experience might improve if you set the multicast rate at say 2MB?