[AG-TECH] IP Multicast address patterns??

[Thomas D. Uram]

Many:

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 224.2.128.0/17, 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:

http://www.mcs.anl.gov/~turam/AG/GetMcastAddresses.py

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,
> TTYL
> Many
> 
>