Re: Friday Facts #99 - MP forwarding
Posted: Thu Aug 20, 2015 11:38 pm
I feel like you're throwing in the towel too soon on the NAT-not-NAT scenario. It's pretty easy to detect.
Assuming A and S are already connected.
1. B tries to connect to S. S handshakes with B and tells B about A and A about B.
2. A sends the handshake to B; at the same time, B sends the handshake to A.
3. B gets the handshake from A, but from S's IP on a different port. A doesn't get the handshake from B.
4. B retries the handshake to A with the address the packet actually came from.
5. A gets the handshake this time, and responds with a second handshake.
6. B gets the second handshake.
7. B forgets the address for A provided by S, and instead uses the address+port that A actually responded to. Setup now proceeds normally.
Given, there isn't a huge gain if they're just on a LAN but there's big gains to be had if there's a VPN involved or goofy firewall settings.
Assuming A and S are already connected.
1. B tries to connect to S. S handshakes with B and tells B about A and A about B.
2. A sends the handshake to B; at the same time, B sends the handshake to A.
3. B gets the handshake from A, but from S's IP on a different port. A doesn't get the handshake from B.
4. B retries the handshake to A with the address the packet actually came from.
5. A gets the handshake this time, and responds with a second handshake.
6. B gets the second handshake.
7. B forgets the address for A provided by S, and instead uses the address+port that A actually responded to. Setup now proceeds normally.
Given, there isn't a huge gain if they're just on a LAN but there's big gains to be had if there's a VPN involved or goofy firewall settings.
