[AG-TECH] IP Multicast address patterns??

Thomas D. Uram turam at mcs.anl.gov
Tue Sep 6 15:09:58 CDT 2005


See comments inline...

Many Ayromlou wrote:
> Hi,
> I just had a discussion with some of our Network guys and they have  
> asked me to see if there is a possible way to give them a list of IP  
> multicast addresses that AG venueservers use. They are trying to  modify 
> the rendevous point on our router based on Multicast addresse  ranges, 
> since a lot of these new "Ghost" like applications use  multicast to 
> mirror disks across networks with wrong ttl's and hard  coded IP 
> addresses that are not in the admin range.
> Anyways.....my question for the Venueserver Gurus :-).....Is there a  
> pattern to the way VV Servers allocate addresses??

By default, mcast addresses are allocated in the range, which you can see 
in the MulticastAddressAllocator.py code.  The Argonne venue servers use these defaults. 
You could query this range for a particular server using VenueServerIW.GetBaseAddress and 
VenueServerIW.GetAddressMask, but you would need to be an admin on the server for the 
calls to succeed.

.....I've noticed a
> lot of 224.x.x.x and 233.x.x.x and I've also seen the ncsa page that  
> keeps track of some of them (https://agschedule.ncsa.uiuc.edu:443/ 
> venues.asp). Or better yet is there some way of querying the info  from 
> the VV Server through some simple means?

You can query a venue programmatically for its multicast addresses using the 
VenueIW.GetStreams method.  I put together a script that does this here:


Given a venue address, it will print the mcast addresses assigned to the venue.  You could 
use this tool to crawl for mcast addresses; let me know if you're interested, since there 
are some authorization hurdles in the way of such crawling.

  I really don't want to
> dedicate one of my students to sit there and click every single Venue  
> on all the servers out there to make a list.
> Thanks,
> Many

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