[Discuss] peer to peer software

[tmetro+blu at gmail.com (Tom Metro)]

Stephen Adler wrote:
> I also realize that from the discussion, the internet is now broken.
> The way p2p is obviously supposed to work is sending out a broadcast
> udp message querying "the internet" for peers. Back in 1990, that may
> have worked, but now?... no way.

I don't think it worked then either. If you think about it,
Internet-wide broadcast messages wouldn't scale. Pretty quickly your WAN
link would be saturated with a steady background of broadcasts.

The more applicable technology would be multicast, but it has scaling
problems too:

http://en.wikipedia.org/wiki/Multicast#IP_multicast

  No mechanism has yet been demonstrated that would allow the IP
  multicast model to scale to millions of senders and millions of
  multicast groups and, thus, it is not yet possible to make fully
  general multicast applications practical. For these reasons, and also
  reasons of economics, IP multicast is not, in general, used in
  commercial Internet backbones.


> So its all about seeding peer discovery through tricks and gimmicks.
> uploading an initial list of peers to an irc chat room...

That's because IRC is a convenient, already existing application-layer
multicast network:
http://en.wikipedia.org/wiki/Multicast#Application_layer_multicast

  Notably the Internet Relay Chat (IRC), which is more pragmatic and
  scales better for large numbers of small groups. IRC implements a
  single spanning tree across its overlay network for all conference
  groups.


> ...a web site, dynamic dns etc.

You could publish a small list of "supernodes" via a CDN. That way you
leverage existing distributed infrastructure, DNS, and anycast
(http://en.wikipedia.org/wiki/Anycast).


> I get this feeling that with all the firewalls spewed through the
> internet, the only port one can use is 80, and everything has to be
> proxyed through that port...

I think that's "old school" corporate firewall. Consumer routers
wouldn't offer any preferential treatment for port 80 outbound. And even
in the corporate environment, using port 80 doesn't get you an inbound
UDP connection.

I'd be curious to know what percentage of - say the Fortune 1000 - block
all outbound connections except for a few select ports.

 -Tom

-- 
Tom Metro
The Perl Shop, Newton, MA, USA
"Predictable On-demand Perl Consulting."
http://www.theperlshop.com/