Subject: Re: Question on initial sequence numbers

From: Vernon Schryver <[email-masked]>
Date: Tue, 5 Jan 1999 12:44:59 -0700 (MST)

> From: "Eric A. Hall" <[email-masked]>

> > Accepting new connections immediately after a quick reboot
> > would be 'breaking' that rule.
>
> Almost every OS that I've ever tested breaks this rule, unfortunately.

That rule is not broken if the system cannot be started in less than 2*MSL.
Only systems that can do a genuine quick reboot are able to break that
rule.  If the system is quiet for 120 seconds after being told to reboot
and until the first user process runs, then the system cannot and does
not break that rule.

Which systems have you tested that break that rule?

I can't think of a operating system that I've seen in recent years that
could break that rule if it wanted to, because they boot soooo sloooowly.
Windows 95, Windows 98, Windows NT Workstation 4.0, IRIX of all versions
since it was renamed from "UNIX" in about 1987, all versions of SunOS and
Solaris I've seen (albeit none newer ~1994), Linux in Redhat 5.1 and 5.2,
NetBSD as of a few years ago, and FreeBSD through 2.2.7 are unable to
break that rule unless you insist on the official, full MSL instead of
the common BSD short value.  Some of those systems could break that rule
even with the full 120 second MSL of RFC 793.  SHEESH!--Some could not
break that rule even if the MSL were significantly longer than 120 seconds.

Vernon Schryver    [email-masked]

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From: Rick Jones <[email-masked]>
Date: Tue, 05 Jan 1999 12:22:37 -0800

All it really takes is switching an IP address from one system to
another in the event of failure. Then instead of being a question of how
long it takes for a system to reboot, it becomes a question of how long
it takes for the system failure to be detected and the IP address
(identity) be assumed by the back-up system (and of course, whether or
not the backup system was being kept up-to-date wrt TIME_WAIT.

Given the pressures on HA in certain markets, I think there is pressure
to have this detection and failover happen in << TIME_WAIT. I am
reasonably confident that modulo icky things like DB recovery the
switchovers are happening < 60 seconds today on a number of platforms.
Probably much less.

rick jones
-- 
these opinions are mine, all mine; HP might not want them anyway... :)
feel free to email, or post, but please do not do both...
my email address is raj in the cup.hp.com domain...

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From: rames <[email-masked]>
Date: Tue, 05 Jan 1999 13:15:01 -0800

> Which systems have you tested that break that rule?

Embedded systems with TCP/IP stacks in ROM are up in a matter of
seconds. See, for example, the AMD Net186 Network Appliance demo board
at

http://www.amd.com/products/lpd/186es/21780a.html

When running a TCP/IP stack, this board is up in seconds.

Richard Ames
U S Software
[email-masked]

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From: "Eric A. Hall" <[email-masked]>
Date: Tue, 05 Jan 1999 13:22:40 -0800

> Which systems have you tested that break that rule?

I can get Linux and NT to boot in less than 120 seconds by thinning down
the number of services in use and using fast gear. I could probably boot
a Sun box in that same time frame if I tried hard enough. Big systems
(VMS, MPE) take longer, but that's mostly due to hardware. Even Compaq
systems (with their overzealous POST tests) running DOS can take longer
than two minutes, but the OS doesn't care.

-- 
Eric A. Hall                                            [email-masked]
+1-650-685-0557                                    http://www.ehsco.com