[arin-ppml] IPv4 runout happens when the first ISP deploys CGN+IPv6*

William Herrin bill at herrin.us
Thu Dec 30 15:54:49 EST 2010

On Thu, Dec 30, 2010 at 3:31 PM, Lee Howard <spiffnolee at yahoo.com> wrote:
> Once ISPs can't get new IPv4 addresses, they may pay for transfers for
> hosted servers, but access customers will get CGN and hopefully IPv6.
> If one of those customers is a p2p seeder, or is your online gaming buddy
> (through any game console), he is unreachable via IPv4.


For about 6 months until some clever fellow decides to sell a gaming
service the crux of which is projecting listening ports out to a
shared server via a VPN from the game host behind his NAT. Give it
another two months before one ISP decides it can trump its main
competitor by buying this cheap tech and advertising its inclusion
with the service.

And give it one cycle of game software before the developers start
building with the assumption that box may be in the picture. Less than
that for the P2P software to catch up.

On Thu, Dec 30, 2010 at 3:44 PM, Matthew Kaufman <matthew at matthew.at> wrote:
> Only for peer-to-peer protocols that can't traverse a CGN.

Which right now is all of them. The NAT traversal hacks for P2P boil
down to two approaches:

1. Have a third party coordinate a connection in the opposite
direction (only one side is behind a NAT)
2. Rely on the typical preservation of the source and destination UDP
port numbers to trick the connection open on both ends (not valid with
CGNs which often won't be able to preserve port numbers and probably
won't try to).

Neither strategy is a winner when both sides of a P2P find themselves
behind a Carrier NAT.

Bill Herrin

William D. Herrin ................ herrin at dirtside.com  bill at herrin.us
3005 Crane Dr. ...................... Web: <http://bill.herrin.us/>
Falls Church, VA 22042-3004

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