From the p2p-hackers mailing list, discussion of the effectiveness of "hole-punching", e.g. sending a useless UDP packet to your peer, even though you know that your peer's NAT will discard it, in order to prime *your* NAT to accept incoming UDP packets from your peer. See this new paper by Bryan Ford et al.:


Peer-to-Peer Communication Across Network Address Translators, Bryan Ford,
Pyda Srisuresh, and Dan Kegel. USENIX Annual Technical Conference, April 2005.
(PDF) http://www.brynosaurus.com/pub/net/p2pnat.pdf
(HTML) http://www.brynosaurus.com/pub/net/p2pnat/


--Z

Begin forwarded message:

From: Alex Pankratov <[EMAIL PROTECTED]>
Date: 2005, February 19, 16:13:24 AST
To: "Peer-to-peer development." <[EMAIL PROTECTED]>
Subject: Re: [p2p-hackers] Final version of "P2P over NAT" paper available


Well, based on same stats it looks like 'hole punching' as it's
described in p2pnat paper succeeds in ~84% of the cases. Our
proggy is a bit more complex than that so our success rate is
about 97%.

Alex

David Barrett wrote:

Heh, great validation of the results.
So if what's the latest values for the following chart:
NAT'd Firewalled
+---------+-------------
% Able to hole punch | 82.2% | 50-60% *
% of total internet | ?? | ??
+---------+-------------
% Benefiting | ?? | ??
* http://zgp.org/pipermail/p2p-hackers/2004-December/002215.html
Basically, I'd like to get a better understanding of what fraction of all
internet users might benefit from these techniques, estimated as the product
of the above rows.
-david
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On
Behalf Of Alex Pankratov
Sent: Friday, February 18, 2005 11:04 PM
To: Peer-to-peer development.
Subject: Re: [p2p-hackers] Final version of "P2P over NAT" paper available


Bryan,

Quoting your paper -

> .. we find that about 82% of the NATs tested support hole punching
> for UDP.
> ..

The NAT Check data we gathered consists of 380 reported data points

> ..

I happened to have statistics for more than 16000 'data poits', and
check this out - the rate of 'identity preserving' NAT devices suitable
for hole punching works out to be 82.2%. *UDP* hole punching that is.


Alex

Bryan Ford wrote:


Hi folks,

For those interested in P2P-over-NAT issues, I just wanted to announce

that

the final version of the following paper, to appear in USENIX '05, is

now

available:

Peer-to-Peer Communication Across Network Address Translators, Bryan

Ford,

Pyda Srisuresh, and Dan Kegel. USENIX Annual Technical Conference, April
2005.
(PDF) http://www.brynosaurus.com/pub/net/p2pnat.pdf
(HTML) http://www.brynosaurus.com/pub/net/p2pnat/


An earlier draft of this paper was announced on this list a few months

ago.

The final version includes, among other minor revisions, new "NAT Check"
testing results based on almost twice the number of data points as the
original draft.


Cheers,
Bryan

---

Abstract:

Network Address Translation (NAT) causes well-known difficulties for
peer-to-peer (P2P) communication, since the peers involved may not be
reachable at any globally valid IP address. Several NAT traversal

techniques

are known, but their documentation is slim, and data about their

robustness

or relative merits is slimmer. This paper documents and analyzes one of

the

simplest but most robust and practical NAT traversal techniques,

commonly

known as ``hole punching.'' Hole punching is moderately well-understood

for

UDP communication, but we show how it can be reliably used to set up
peer-to-peer TCP streams as well. After gathering data on the

reliability of

this technique on a wide variety of deployed NATs, we find that about

82% of

the NATs tested support hole punching for UDP, and about 64% support

hole

punching for TCP streams. As NAT vendors become increasingly conscious

of the

needs of important P2P applications such as Voice over IP and online

gaming

protocols, support for hole punching is likely to increase in the

future.

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