All things related to multicast

[Bill Owens <>]

On Fri, Jun 27, 2008 at 03:14:02PM +0100, Tim Chown wrote:
> On Thu, Jun 19, 2008 at 09:51:13AM -0400, Bill Owens wrote:
> 
> > Since this has become a recurring problem I'm going to approach it 
> > through education; telling people not to leave a SAP listener running on 
> > their desktop, and getting them to disable sap listen on their routers. 
> > Hopefully that will be enough. But I wonder whether it is time to start 
> > down the road towards deprecation. . .
> 
> ... which leads to the question of a viable alternative.
> 
> I'm hoping to have a project student working on the general area next
> semester.   I'd be interested in references to projects that are
> monitoring existing SAP traffic, with a view to redistributing the 
> information via other means (perhaps RSS-a-like).   In our case, we
> would include IPv6 SAP also.

I vaguely recall such things being discussed several times, but I've always 
paid them little attention because SAP:
 - already works
 - is built into every important client and server application
 - isn't all that useful anyway
 
To date, any replacement service would have the first two points as hurdles, 
and the third point as its only way to gain an advantage. Now we can add the 
threat of SAP storms to the list, but those only affect the network 
operators, not the end users (at least, not directly).

I suspect that there are some hidden hurdles to acceptance of a new solution 
as well. SAP was designed back in the golden days when everybody trusted each 
other and we were all friends - not like today :) Any replacement would be 
held to a higher standard for resistance against spoofing, DoS attacks (to 
the service as well as to the participants), protocol extensibility, 
internationalization, etc. And whatever buzzword compliance you decide on, 
somebody will prefer a different buzzword. At any rate, good luck and 
godspeed ;)

Of course, SAP would go away if we could ever kick our addiction to ASM. And 
I don't really think that it has any future at all in v6, except perhaps as a 
local-area service (ie. within the reach of a single PIM domain). Perhaps 
that's the way to push forward - we need something for the inevitable future 
when we're all running SSM/embedded-RP v6 multicast.

Bill.