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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

atomicluis
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  • Good question. I'm assuming that since a WAP is a layer 2 device that it will behave the same as any other layer 2 device and will handle unicast, broadcast and multicast traffic just as any other layer 2 device would. – joeqwerty Apr 06 '14 at 04:24

1 Answers1

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The access point has to send some broadcast packets into the air, otherwise the network wouldn't work. As long as the wireless interface isn't congested, there is little reason not to send them all. In case of congestion it has to decide which packets goes through and which are dropped. At that point it may handle broadcast packets differently from other packets.

A switch has to transmit a broadcast packet on all ports except from the one it was received on. An access point should not have to send the packet once to every device associated with that access point. Instead it should be sufficient to send it once and have all devices simultaneously receive the packet being broadcast just once.

kasperd
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  • The issue with 802.11 is how this happens when the AP<->Client connections are separately encrypted which should (now) be the normal case. The "same" signal can't be broadcast, each client has to get a version encrypted just for it. So broadcasts become a set of unicasts. – Helvick Apr 06 '14 at 18:58
  • I don't know exactly how 802.11 implements it. But one way it could have been implemented would be to use one key for broadcast and a set of different keys for unicast. – kasperd Apr 06 '14 at 19:14
  • What if there is no associations to the AP? will the broadcast packets be sent then? I'm getting high duty-cycle values for the 2.4 GHz channel when a client is associated to the AP. If no clients are associated, the duty-cycle drops. It looks like the AP is smart enough to not send any data (except for management frames) when there is nothing associated to it. – atomicluis Apr 06 '14 at 19:28