RE: [ssm] IPv6 Multicast Throughput problems in 802.11

"Tiago Sousa" <> Tue, 15 November 2005 16:21 UTC

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From: Tiago Sousa <>
To: 'Marshall Eubanks' <>
Subject: RE: [ssm] IPv6 Multicast Throughput problems in 802.11
Date: Tue, 15 Nov 2005 16:21:03 -0000
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Thanks for the reply.

Well, one cool thing about 802.11 is that you can generally see every

Have you  used tcpdump to see if the packets get placed into the air ?

Yes. I sniff the router outgoing interface where the AP is connect and I can
see the packets flying to air.

That should distinguish  between broken packets (they are there, but 
fragmented or
have some  other problem) and some filtering happening in the access point

It is true. The majority of times I see fragmented packets in the outgoing
interface. Do you think that AP is filtering this fragmented packets? Why?

If they aren't, you should be able to put a hub at the  AP or look on
the AP LAN and see if they are _reaching_ the AP. (You can join the
group on the AP LAN if it is not broadcasting multicast) If they are,
then it's an AP problem. If I had to guess,
I would suspect an AP problem, but it's good to know for sure.

I will find another AP and try. 


Tiago Sousa


On 11/14/05, Tiago Sousa <> wrote:
> Hello to all
> I am testing the PIM-SSM daemon (both freebsd and linux) and mrd6 (another
> IPv6 multicast routing daemon) in a wireless link.
> The problem I encountered with both pim6sd daemon and mrd6 is that I'm
> sending multicast traffic at 4 Mbps and the throughput in the mobile node
> (which is very near from de access point) rounds 40 kbps.
> I am using the mad-flute tool to send the multicast SSM traffic and the
> tcpdump plus trpr to analyze the data. I have also used IxChariot and the
> results are the same.
> Anyone knows why the throughput decreases so much in the wireless link?
> (The multicast TTL is well defined, I have experimented with several
> pci/pcmcia cards and drivers and several access points configurations
> (different channels and rates (801.11b and 802.11g)). The results are
> always the same).
> I would appreciate any help/hint that helps me to explain these results.
> Thanks.
> Tiago Sousa
> _______________________________________________
> ssm mailing list

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