All things related to multicast

["Marshall Eubanks" <>]

On Tue, 25 Oct 2005 06:01:25 -0700
 Russ Hobby 
<>
 wrote:
> Hi All,
> 
> I have been asked a question from a researcher who's project has been 
> trying to use multicast for some time with many problems, and she asked me 
> "Are we trying to do the impossible?"
> 
> Their particular use of multicast relies on multiple multicast connections 
> and for them to be set up in a timely fashion.  It is the setup time for a 
> connection with which they have been having trouble.  Connections can take 
> up to several minutes to be established.  They have worked the problem out 
> with a couple of campuses and a gigapop to get it to work (which had to 
> wait for new router codes to be installed in several places).  However 
> every time they go to a new site, they are likely to have the problem again 
> and they have to work it through those network engineers.
> 
> So the researcher is asking if they should give up on multicast and 
> redesign their application.  What do you think?

I think that you are not giving enough information to get a useful answer.

What exactly are they trying to do ? How many connections ? One to many or
many to many ? ASM or SSM ?

Why, exactly, is it taking so long ? What code (to do what) has to be changed 
?

The long-term problems that  I have seen with multicast tend to be along the 
lines
of having some sites silently black-holed, not excessive delays. 
Minute-duration set up times seem very  strange (unless the packet loss is in 
the  50% range, in
which case you have other problems). Multicast setup should be in the one 
second or less range,
generally comparable to or less than player buffers and other systemic delays.

But, no, based on the information given, this does not seem usual.

Regards
Marshall Eubanks

> 
> Russ
>