Re: Use of SAP in a PIM SSM Network

[Jon Crowcroft <J.Crowcroft@cs.ucl.ac.uk>]

In message <200011160217.SAA11212@cisco.com>, Toerless Eckert typed:

 >>> Maybe SSM is just a stepping stone to the full functionality that
 >>> shared-tree infrastructures provide.  But it will be a whole lot better
 >>> than what we have now, where multicast is virtually nowhere to be found.
 
 >>The whole point is that global source discovery in the network layer with
 >>a non-hierarchically managed address space has shown to be a non-scaling
 >>approach. There are things that sound cool in the first place and work

not clear - the GLOP and ipv6 ways of allocating multicast introduce
_some_ hierarchiy - in fact its relatively easy to impose all sorts if
you have _enough_ address space.....

 >>to a point but have some limits. Just because we learnt this about the
 >>IP Multicast model after 10 years doesn't mean that the model is bad or
 >>that we should force to make it work somehow, if there are much more
 >>easy alternatives to get to the same results by just putting tasks into
 >>different layers.

if yo uhave applications which genuijley have significant number of
sources  with dynamics, then the server solution does not scale - you
have just pushed the management problem to that of
1/ locating one of a set of servers (how)
2/ making servers fault tolerant (anyone for anycast? :-)
3/ managing the application state in an unnatural way
4/ putting performance (delay and procerssign) limits on the scale of
the application

ok so you could have a hierarchy of redundant servers....,and what
standard internet protocoos are you going to use to manage those?

no, i think we need to retain the deering multicast model and just
keep up the pressure on Large Router Vendors (this means you:-)
to be smart about scaling the routers up to meet the users
requirements rather than scaling the users expectations down to what
you want to do:-)


 cheers

   jon