All things related to multicast

[Joel Jaeggli <>]

On Thu, 13 May 2004, Hugh LaMaster wrote:

> 
> On Thu, 13 May 2004, John Zwiebel wrote:
> 
> > I agree with Tom that multicast isn't going to take off until
> > there are high-BW applications.
> 
> Agreed.  We had a high-BW imaging application demonstrated 
> in 1999 and did HDTV in 2001.  You need multicast to do this,
> but, most people are not going to have 19-50 Mbps to the home
> for a while.

in the US... 23Mb/s yahoo broadband in japan is $30month 100Mb/s from usen 
is around $80.

>  If we have to wait for high-BW to the home
> for multicast to be useful, we're going to keep waiting
> for a while.

perhaps the US broadband consumer isn't the target audience.

> > Moving on, those high-BW applications are -NOT- going to use
> > ASM.
>
> 
> Our high-BW applications *did* use ASM, and although 
> they didn't work with PIM-DM, they did work with PIM-SM/MSDP.
> 
> ASM/sdr will not scale to billions of home users, but, 
> since few are going to have high-BW to the home anyway,
> I'm not certain that is a barrier.

There's aren't billions of home users anyway.

> My biggest question is, "What is impeding multicast on college/
> university/research park campuses?"  Most of the objections to
> doing high-BW multicast don't apply there, but, success has still
> been limited.  Perhaps even grad students are too busy producing
> PowerPoint slides to watch IETF and NANOG broadcasts.

the sames reasons the cable msos and telco's don't do it. aging wiring
plant, no capital expendititures for things that don't book additional
revenue immediatly, no business plan, lack of vision.

> > So, the barriers to multicast are:
> >    -- last-mile
> >     Where is AMT or how do we break the monopoly that the
> >     home providers have.
> 
> This is going to take the longest to solve.
> 
> >    -- no source discovery protocol that doesn't depend on multicast
> >     (ie, sdr doesn't scale to an interdomain environment and
> >     continued attempts to make it do so will not work.  Storing
> >     this information "in the network" by pushing it out via multicast
> >     is OK in a dense environment, but the Internet is not a dense
> >     environment.)  This has to be an application level protocol
> >     like DNS (ie, putting the SDP file on a web page, although not
> >     elegant, does work.  Perhaps a discussion of why this isn't
> >     "good enough" is in order?)
> 
> I'm at a loss for why this hasn't taken off more.
> 
> >    -- MLDv2 and IGMPv3.  Its in KAME so "soon" will be in FreeBSD and
> >     therefore OSX (I hope).  Perhaps a little lobbying of the FreeBSD
> >     folks to incorporate the KAME IGMPv3 and MLDv2 would be in order?
> >     (I don't know the process)
> > 
> > This forum has been wondering about the sasser attacks on MSDP.  SSM
> > would eliminate this kind of an attack.  SSM does open up for a 
> > "reverse"
> > attack where a "evil-doer" could join every IP address in the world 
> > causing
> > creation of lots of state.
> 
> This is going to be a major issue.  Routers should have  
> relatively small defaults for the number of groups 
> allowable by default, and folks who need more can configure
> it upward.  Something like 64 groups/512 routes by default
> on an interface would be a nice limit.  Increase it if you
> need to.  If the default is low, it would limit the damage
> from a compromised host or incorrect network scan or whatever.
> 
> In the long run, this is going to be a big enough issue that
> real management tools are going to have to exist.  We're going
> to need more than a router log entry to understand if the
> need for more groups is legitimate or just the result of a 
> worm downstream.
> 
> 
> > I'm often accused of being unrealistic because I keep saying "kill asm" 
> > and
> > "Kill MSDP".  Perhaps I should change my mantra to "allow it to wither".
> > I keep seeing efforts (I think) wasted on making ASM better because we 
> > have
> > to support all those legacy hosts that don't support IGMPv3 so can't do
> > SSM.  Yet, I sure don't see the explosion of multicast that was suppose 
> > to
> > happen because we maintained that backward capability.
> 
> 
> We seem to have already saw the explosion, which peaked during 
> 2000-2001, and traffic and sources have declined severely since then.  
> 
> 
> 
> ==============================================================================
>  Hugh LaMaster, M/S 233-21,   Mail: 
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Joel Jaeggli           Unix Consulting         

    
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