Subject: [mobile-ip] NAT/PT

From: "Michael R. Cole" <[email-masked]>
Date: Tue, 24 Jun 2003 05:53:25 -0400

Dear Pascal,

Thanks for letting me know that there are TCP only firewalls, which also means that there is the possibility of a TCP only NAT box. Come to think of it, Zonealarm mainains one set of firewall rules for TCP and another set for UDP. This means that ports can be selectively TCP, UDP, TCP + UDP, or closed.

Perhaps one way to save bits in a translation format is to have a flag that tells us if the SLA is really used as an SLA or is used for another purpose such as encoding a second port number.

By the way, how do I subscribe to [email-masked]?

I am also thinking that so called stationary internet users would benefit from a mobile protocol when they are logged in at a place other than their home. Essentially, they would be doing a slow version of roaming. Changing internet providers is also in a sense a form of roaming - call it super slow roaming. Come to think about it, if someone starts a 2-hour download at home and then goes to the library and uses one of their terminals, then they would be at two places at the same time which most ISPs prohibit. (There are enough cheapie ISPs around to bypass this problem.)

The reason why I have suggested that a timesharing system a.k.a. a terminal server could be classified as a NAT-like device is that if a timesharing system has one global address then the port number would be used to identify users. The same thing happens when a supposedly single-user workstation is running jobs for other people in a distributed computing environment such as folding@home. Today's computers are powerful enough that timesharing does make sense again, especially if you want to contribute unused CPU cycles to a worthy cause.

Looking at it one way, a NAT box theoretically causes a LAN to pretend to be a single timesharing machine with a single global address. How well that virtual machine works in actuality is another matter.

Mike Cole, [email-masked]