All things related to multicast

["Richard Mavrogeanes" <>]

I've mentioned this to the group before.  Part of the problem is that
the default SAP address of the sender is global, but the multicast is
locally scoped.  If you are doing locally scoped (campus) video
streaming, you *should* change the SAP address to locally scoped too,
and then set the SAP listener to detect on that local address.  But
people don't know any better, hence you get advertisements that point to
streams that can't work. Add to this the difficulty to communicate with
potential viewers that they have to listen to a different address to get
their program announcements. I think it would be nice if the routers
could peek inside the SAP/SDP and only forward it if the multicast
address were within some specified range.  We solved this on our server
by filtering SAPs, but there are issues here too.

There are three SAPs that each VBrick device can send, and owners rarely
change the addresses, but they should in many cases :)

/rich




-----Original Message-----
From: Taylor, Scott J. 
[mailto:]
 
Sent: Thursday, June 19, 2008 11:54 AM
To: 

Cc: wg-multicast
Subject: RE: SAP storm from 145.19.1.183

> -----Original Message-----
> From: Bill Owens 
> [mailto:]
> Sent: Thursday, June 19, 2008 09:51
> To: Michael Lambert
> Cc: wg-multicast
> Subject: Re: SAP storm from 145.19.1.183
> 
> Looking at the display in VLC just now, I
> have 44 working streams (though that's being generous, at least 8 of
> them had no a/v content) and 51 non-working. I've long been in the
> habit of warning people who want to test multicast that they have no
> better than a 50/50 chance of picking a working stream at random.
> 
> Bill.

Please forgive the ignorance; isn't this mostly due to the multicast
groups being advertised by SAPs falling into the reserved or
administratively scoped space?  I know that here at CEN we advertise
some SAP's for mpeg2/4 streams that are configured in the 239/8 range
and can't be viewed outside of the CEN network.  I haven't had an
opportunity to verify if these can be seen past our network.  Do you
have any recommendations on best practice or etiquette that is generally
agreed upon in this regard?

-Scott