Broadcast Repeat Count

Can someone please shed some light on this setting.  I understand it sends multiple packets in case any are lost do to errors but is it only referring to broadcast packets or is it every packet that is sent out. 

Is it worth changing at all in an ISP deployment or will this cause more problems then any actual gain of throughput.

From Sri: "For broadcast repeat count, leave it at 0 if you don’t have any BC/MC traffic to send to the SM. The repeat count is just to increase the chances of the broadcast traffic getting to the SMs."


Thank you :)

We use a 'true' broadcast channel on Canopy, and all registered SMs receive this VC. As broadcasts are not acknowledged, we cannot tell if an SM misses one. The repeat count lets you send multiple copies, improving the chances that every SM will get a clean copy. The tradeoff is that because the broadcast VC runs at 1X, repeats cause each broadcast to consume more of the RF channel bandwidth, and with a lot of broadcasts that can add up surprisingly quickly.
As Eric noted, setting the repeat count to 0 minimizes the cost of broadcast messages and is a good choice if you have minimal or no such traffic, or clean links. If you're running into trouble getting responses to ARP messages, or your SMs are missing other broadcast messages, you may wish to set the repeats to 1 or 2. The default (2) is the "most reliable" setting, but not the most efficient use of bandwidth if you have clean links to your subscribers.

On the AP, the effective broadcast CIR configured on the web page is multiplied by the total number of copies (including the original) being sent. At 0 repeats, this is the value shown. At 1 repeat, the real, actual CIR is double the amount shown, and at 2 repeats the actual CIR is triple the amount shown.

On the SM, broadcasts are handled differently. There is no uplink broadcast channel, so uplink broadcasts are sent on the regular data VC.

The separate Multicast VC (multicast is determined based on IP address) was added to let you minimize this cost if you're running multicast traffic such as a video stream. If you enable the multicast VC, you can choose to lock it to a higher rate, provided the SMs needing to get multicast can receive at that rate.

-- Josh