xml-dev - Re: what Napster means for XML

[David Megginson <david@megginson.com>]

W. E. Perry writes:

 > I don't take this as a blanket dismissal at all. In fact, it seems
 > to me that you validate my argument. What does scalability mean
 > except adequate supply to meet actual demand?

I agree that that's the great advantage of a Napster-like approach
(though in Napster's case, there's still a central server managing
connections, and that can act as a single point of congestion).

The problem is that you're sacrificing availability of lower-demand
items.  Let's say that 100 people/month want a copy of thing A, and
100,000,000 people/month want a copy of thing B.  With a client/server
approach, things A and B will both usually be available, but providing
thing B is costly (it requires expensive hardware, a complex system of
mirrors, or both).  

With a peer-to-peer approach, thing B can be provided for a much lower
up-front cost to the initial supplier (though, perhaps, a higher
overall cost), but it will be difficult to find (requiring some sort
of central server or ad-hoc contact); thing A will usually not be
available at all, at least not at the time of the user's choosing.

Clearly, both approaches can work, but I don't think it's very
responsible to push either as The Solution To Every Problem.
Basically, a peer-to-peer system can make high-demand items available
more easily by spreading the cost of distribution among more users,
while a client-server system can make all items available predictably
and in an easily-referenced location.  Look at the kind of information
you're publishing, and make the choice.


All the best,


David

-- 
David Megginson                 david@megginson.com
           http://www.megginson.com/

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