All things related to multicast

[Hugh LaMaster <>]

On Wed, 28 Jun 2000, Alan Crosswell wrote:

> Date: Wed, 28 Jun 2000 14:47:10 EDT
> From: Alan Crosswell 
> <>
> To: Ted Hanss 
> <>
> Cc: 
> 
> Subject: Re: Multicast uses other than video
> 
> > Is anyone using multicast for an application other than video 
> > distribution? 
> > At the last Internet2 member meeting I asked that question and there were 
> > some campuses using multicast to distribute OS images to workstations, 
> > but 
> > I didn't write down any of the names of the schools. There are corporate 
> > networks that use multicast for data distribution, but we're seeking 
> > examples from higher education.
> > 
> > I'm asking as George Brett is putting together a NLANR-supported workshop 
> > and he wants to include examples other than video from our community. So, 
> > please pass any pointers on to me or George 
> > ().
> > 
> > Thanks.
> > 
> 
> We use Ghost for software distribution in our computer labs.

There was a discussion earlier on the year on this mailing
list regarding PowerQuest DriveImage.  (Norton Ghost
was mentioned in passing as well.  Apparently both
products do something similar.)

Does anyone know what group(s)/port(s)/TTL(s) are used
by Norton Ghost?  Has DriveImage changed at all in the
last 6 months?

At the time of the previous discussion, it was demonstrated
(via tcpdump) that DriveImage (mistakenly IMHO) uses multicast 
group 230.0.0.1 (maps to (01-00-5e-00-00-01) at (mistakenly IMHO) 
TTL 255 for its operation (using port 2222 for data, or is this
dynamically assigned? -- and possibly port 12000 for announcements).  
This means that:

a) it will be forwarded out all interfaces on a switch even 
if the switch is running CGMP or IGMP snooping, and, that 
hosts actually listening to "all systems" may have to drop 
5000 pps in the NIC driver, (it would have been better to use
a group which wouldn't be forwarded in switches by default),

b) within an AS, if multiple groups are using it, hosts intending
to listen to one server may end up listening to all active servers
(since the traffic is sent out at TTL 255), (does anyone know
what kind of security/data integrity is in place on these
two packages?) and,

c) under some circumstances, you may even get sharing across AS's


Someone please correct me if I am wrong on any point!
Can anyone confirm the above information wrt DriveImage,
and, can someone tcpdump the equivalent information from
Ghost?



If the above is all correct, then, while I laud the use of multicast
(industry testimonials are very positive about the value of multicast
in speeding up distribution of software from a single server to many 
clients), I think these packages probably need some modifications
before they are really compatible with Internet2 global multicast.


Comments/confirmations/refutations welcome!


--
 Hugh LaMaster, M/S 233-21,    Email: 

 NASA Ames Research Center     Or:    

 Moffett Field, CA 94035-1000  Or:    

 Phone: 650/604-1056           Disc:  Unofficial, personal *opinion*.