IP Multicast problem

IP Multicast problem

Post by Martin Stran » Wed, 01 Mar 1995 03:29:01

I have a PCnet/PCI ethercard, running with a 1.1.92 kernel. I'd really like
to do a bit of multicast IP (e.g run nv etc.) to get a feel for the
performance, but it seems that when ever a program attempts to use a multicast
address, the ethernet driver does something which screws up normal networking.

I guess it is trying to set up the multicast filter on the card, and has to
stop the card to do it. Unfortunately it doesnt seem to bring it back up
again (or if it does, then *everything* is being filtered out...)

Before I have a go at hacking the driver into shape, am I missing something
obvious ? In particular, if anyone has successfully enabled multicast on
a PCnet/PCI could you let me know so that I know the driver is OK.



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1. IP Multicast problem


I've written an IP multicast server/client on windows that works fine.

For some time now, I'm working on Linux, ported the program and works
fine... except for following behavior:

It seems when I send IP multicast data, that there's sometimes a big delay
in sending the data and receiving (user-space application, using sockets)
The data comming from the recv-function is sometimes much delayed (couple
of 100 ms). When I stop serving data for a while, and restart again, delay
is gone (1 ms).
Is there a buffering of UDP multicast packets in the kernel (2.4.7-10) when
client is on high load, that I should know about?
The multicasting has about 500k - 1Mbit/s transfer rate.

Correct me if I'm wrong, but is should the data not be lost when the client
is too busy working on something than retrieving data from the network?
I have no problem with losing the data, do have a problem with

Anyone had the same problem?
Is there a cause/solution?

Thanks in advance,

Dewilde Andy

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