[p2p-hackers] P2P or centralized

Salman Abdul Baset salman at cs.columbia.edu
Thu Aug 14 21:12:03 EDT 2008

>>>> Nodes need to connect to a central server to get their identity signed by a
>>>> central server. This must happen to prevent Sybil attacks. A bootstrap server
>>>> can be co-located with this authentication server.
>>> That's one thing that's bothered me with a lot of discussions of P2P.
>>> At the end of the day, real-world p2p systems utterly depend on
>>> reliable, realtime access to centralized components.  Successful systems
>>> recognize and exploit this.
>> BitTorrent, eMule, Skype are examples of successful distributed systems.
>> They may not be 'purely' distributed, but work reasonably well.
>>> Usability, security, decentralization.  Pick any two.
>> For Skype, can we pick all three? :)
> Skype isn't decentralized.  They have central bootstrapping, central
> authentication, central billing, etc.  If Skype says you don't talk, you
> don't talk.  If Skype blows up, you don't talk.  And as happened last
> year, if their pointless rendezvous mesh gets destablized due to massive
> reboots, you don't talk for a long time.

If MSN, or Yahoo says don't talk, then you don't talk either...

> AIM, ICQ, or MSN are all far bigger than Skype; have they *ever* gone
> down that long?
> Anyway, just pushing back on the religion that P2P has developed.  It's
> fun.  It's sexy.  It's really hard.  But it's often pointless.

The advantage of p2p is that it reduces cost of entry in a certain market 
space. No one denies that anything p2p cannot be done central. However, 
sometimes economics justify using p2p as a solution. And in Skype's case 
experience gained from Kazaa was no doubt helpful.

To completely rule out non-server p2p as a possible solution for a problem 
is also naive, and amounts to a no-p2p religion.

My point is that take a hard look at the problem and the economics, and 
pick a solution that has the best cost/benefit ratio. If the solution is 
p2p, so be it.


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