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This is a sub-selection from No Clue


knightmb
Everybody Lies

join:2003-12-01
Franklin, TN
reply to funchords

Re: No Clue

Everyone has to keep in mind, this is from the standpoint of a single IP address. When you sit behind a NAT router with multiple computers using the Internet from an access point of either DSL, T1, Cable, etc. then all of the problems you experience are the limitations of NAT.

Try this same experiment with two separate IP address on the same link and you'll notice the problem goes away. You can have a 1 MB/s Up and Down link (just for easy math reason) and if you have 1 IP address with a NAT sitting in front of it burning all the bandwidth available, then yes the issues of sharing come into play. But if the same link had 2 IP address in which they both shared that 1 MB/s pipe, and 1 IP address was maxing out the link with 1 or 100 connections, the other IP address would still get exactly half of the bandwidth for it's one single connection it had going. TCP/IP is suppose to work properly from IP address to IP address, not IP address to self.

The NAT router is no different that one computer with one IP address having to determine what takes priority over what. When you don't have any traffic shaping or QoS on the NAT, then yes it's first come first serve because that's the whole limitation of using NAT to share multiple computers behind the same IP address.

When they wrote the TCP/IP stuff decades ago, they didn't have to worry about NAT routers and how it changes the rules.



funchords
Hello
Premium,MVM
join:2001-03-11
Yarmouth Port, MA
kudos:6

said by knightmb:

But if the same link had 2 IP address in which they both shared that 1 MB/s pipe, and 1 IP address was maxing out the link with 1 or 100 connections, the other IP address would still get exactly half of the bandwidth for it's one single connection it had going.
What you are describing here is the proposal from Bob Briscoe and George Ou. I say proposal because it (reportedly) does not work as you are suggesting it does.

Are you saying that you've run a test that shows otherwise? If so, please describe your test environment (some stacks behave differently than others). Maybe we can figure out why the results came out like that.

said by knightmb:

TCP/IP is suppose to work properly from IP address to IP address, not IP address to self.
I don't understand this final line at all. Can you rephrase it?

said by knightmb:

When they wrote the TCP/IP stuff decades ago, they didn't have to worry about NAT routers and how it changes the rules.
Two responses to this:
1. TCP definitely has been revised since RFC 793. In so much as each revision changes the protocol somewhat (aka an "update"), it's not exactly fair to say that NAT hasn't been considered.

2. (And now to contradict myself,) NAT is not yet an Internet Standard. Various implementations of NAT to not play the same -- some do not play well together. So what NAT does, or what TCP does across a NAT device, probably varies.
--
Robb Topolski -= funchords.com =- Hillsboro, Oregon
"We don't throttle any traffic," -Charlie Douglas, Comcast spokesman, on this report.