[ossig] multicast + linux ...

[Christopher DeMarco <cdemarco@fastmail.fm>]

Hey all...  I'm currently trying to grok multicast-as-a-protocol and the
specific implementation  in the Linux 2.4.x  kernel (iproute2).  Nothing
complicated, no multicast  routing, just a switched network  and a whole
lotta love... er, multicast traffic.  Here's my scenario:

I have  three boxes connected  to a switch  ( I know,  multicast doesn't
really make  sense for numbers <  4; bear with  me ).  All of  them have
modern network cards  and are running Red Hat 8 with  a 2.4.x kernel.  I
have multicast working - barely.   I can ping 224.0.0.1 and the expected
number  of hosts  respond; when  I say  ``ip maddr  add  224.0.0.224 dev
eth0'' I can then stream to a multicast group and the correct hosts will
see my video stream.  Here ends my success ;)

#1: I'd  like to be able  to see what  multicast groups a given  host is
 "listening" to; I'd  suspect that ``ip maddr show  eth0'' will do that;
 but all I get is a rather weird-looking list of MAC addresses - my math
 is  too poor  to convert  the hex  into decimal,  and a  cursory Google
 doesn't turn  up any  good MAC<->multicast calculators  (but I  found a
 whole boatload of MS-based ones >:|  ) Is this the right command to see
 what multicast groups I'm listening to?  How best to do the math?  (and
 yes, if somebody does want to sit  down with me and beat me on the head
 with a pencil and paper I'm willing to learn... ;)

#2: the meat  of the problem: My switch doesn't  have any fancy hardware
 to do IGMP snooping, nor do I have a Cisco router in the picture to use
 their  proprietary  CGMP  protocol.   Therefore the  switch  sends  ALL
 multicast datagrams to ALL ports  - pretty much cancelling the benefits
 of  multicast in the  first place,  since I'm  constrained to  a 10Mbps
 network and  I'm streaming video!.   I need to  be able to bind  my MAC
 addresses to IGMP  addresses, but I'm stuck with  the handicap outlined
 in #1  - I can't  do the  math :( And  anyway my IGMP  understanding is
 still pretty spotty.

Help?  Please!?

-- 
% YOU are in a maze of twisty passages, all alike.
  Christopher DeMarco
  cdemarco@fastmail.fm
  +6013 389 5658

------------------------------------------------------------
To unsubscribe: send mail to ossig-request@mncc.com.my
with "unsubscribe ossig" in the body of the message