This raises an interesting issue - should optimization of p2p traffic (P4P) be based on "static" network information, or "dynamic" network information. It's certainly easier for ISP's to provide a simple network map that real-time network condition data, but the real-time data might be much more effective. Or even if it's not real-time, perhaps there could be "static" network maps reflecting conditions at different times of day?
Since P4P came up, I'd like to mention that the P4P Working Group is putting together another field test, where we can quantify issues like the tradeoff between static and dynamic network data, and we would love to hear from any ISP's that would be interested in participating in that test. If you'd like the details of what it would take to participate, and what data you would get out of it, please email me.
Of course, independently of the test, if you're interested in participating in the P4P Working Group, we'd love to hear from you!
- Laird Popkin, CTO, Pando Networks
email: laird@pando.com
mobile: 646/465-0570
100% solution + 100% more complexity vs 80% solution ?
It strikes me that often just doing a reverse lookup on the peer
address would be 'good enough' to keep things more 'local' in a
network sense. Something like:
1) prefer peers with PTR's like mine (perhaps get address from a
public-ish server - myipaddress.com/ipchicken.com/dshield.org)
2) prefer peers within my /24->/16 ?
This does depend on what you define as 'local' as well, 'stay off my
transit links' or 'stay off my last-mile' or 'stay off that godawful
expensive VZ link from CHI to NYC in my backhaul network...
P4P is an interesting move by Verizon, tin-hat-ness makes me think
it's a method to raise costs on the direct competitors to VZ (increase
usage on access-links where competitors mostly have shared
access-links) but I agree with Harrowell that it's sure nice to see VZ
participating in Internet things in a good way for the community.
(though see tin-hat perhaps it's short-term good and long-term
bad.../me puts away hat now)
-Chris
Well. here's your problem; depending on the architecture, the IP addressing
structure doesn't necessarily map to the network's cost structure. This is
why I prefer the P4P/DillTorrent announcement model.
Alex
sure 80/20 rule... less complexity in the clients and some benefit(s).
perhaps short term something like the above with longer term more
realtime info about locality.
For the applications, it's a lot less work to use a clean network map
from ISP's than it is to in effect derive one from lookups to ASN, /
24, /16, pings, traceroutes, etc. The main reason to spend the effort
to implement those tactics is that it's better than not doing
anything. 
Laird Popkin
CTO, Pando Networks
520 Broadway, 10th floor
New York, NY 10012
laird@pando.com
c) 646/465-0570
so.. 'not doing anything' may or may not be a good plan.. bittorrent
works fine today(tm). On the other hand, asking network folks to turn
over 'state secrets' (yes some folks, including doug's company)
believe that their network diagrams/designs/paths are in some way
'secret' or a 'competitive advantage', so that will be a blocking
factor. While, doing simple/easy things initially (most bittorrent
things I've seen have <50 peers certainly there are more in some
cases, but average? > or < than 100? so dns lookups or bit-wise
comparisons seem cheap and easy) that get the progress going seems
like a grand plan.
Being blocked for the 100% solution and not making
progress/showing-benefit seems bad 
-Chris
Well. here's your problem; depending on the architecture, the
IP addressing structure doesn't necessarily map to the
network's cost structure. This is why I prefer the
P4P/DillTorrent announcement model.
What's with these cute cryptic and ultimately meaningless names?
I used the term "topology guru" because I wanted something that
halfway describes what is going on. Coining a word with "torrent"
in it is wrong because this kind of topology guru can be used with
any P2P protocol. And P4P seems more like a brand name that tries
to leverage off the term P2P.
--Michael Dillon
needs to move lots o' bits around can use.
-brandon