Take the 2-minute tour ×
Network Engineering Stack Exchange is a question and answer site for network engineers. It's 100% free, no registration required.

I have an Cisco AP 1242AG autonomous AP connected to L2 switches.

Let's say I have 100 wired devices each sending 2 broadcast UDP packets per second.

Obviously these packets will reach the Access Point switch port, but will the AP actually send these packets (200 pps) into the air?

Thanks

share|improve this question
1  
Please don't cross post –  Mike Pennington Apr 6 at 14:22

1 Answer 1

up vote 5 down vote accepted

(non-cisco specific answer)

Yes, unless you disable it.

The broadcast frames will be sent at the multicast base rate, which is typically low (1 Mbps most of the time), and only every DTIM * beacom interval if there are powersaving stations. And the packet loss rate for those will be quite high.

However, if there are no clients associated to the AP, then the AP will typically be smart and not send them.

200 broadcast packets per second, assuming a 8192 bit packet size and a 1 mbps multicast rate, will just Not Work, since the multicast traffic will be more than 1 mbps, and the AP will typically allocate much less capacity and buffers for broadcast, so the limit is actually much less than 1 mbps.


Anyway, broadcast is so 1990, if you can use multicast instead, and enable MLD/IGMP snooping on the AP, then the AP may be smarter and only deliver the multicast frames if clients actually subscribe to the multicast address. And depending on the client capabilities and the AP configuration, the multicast frames may even be sent as unicast, at higher data rates and with less packet loss.

IPv6 has no broadcast anyway.

share|improve this answer
    
BtachyX, thanks! Actually, these wired devices are from 90's and by design will send 2 UDP pps to 255.255.255.255. I noticed my 2.4 GHz channel duty-cycle is decent when no clients are associated, but skyrockets when at least one of them connects to the AP. Would disabling the low data rates on the AP help keep my duty-cycle low? –  atomicluis Apr 6 at 11:42
    
Yes. But if your clients don't need to receive the broadcast packets, I would suggest to filter them or disable multicast forwarding on the AP. Even at 6 mbps, 200 packets per second is quite a lot. –  BatchyX Apr 6 at 13:20

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.