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Re: [partly OT]: in-between ISPs



On Mon, Aug 06, 2001, Oleg Goldshmidt wrote about "Re: [partly OT]: in-between ISPs":
> "Nadav Har'El" <nyh@math.technion.ac.il> writes:
> 
> > Could it be ADSL problems? For example, if your MTU is too high small
> > packets (like the authentication packets) will pass properly, but once
> > you try to send large packets (such as segments from the bulk of a message)
> > it may get stuck somewhere in ADSL limbo. Try setting your MTU (with ifconfig
> > on your RH7.1 computer) to something lower - say, try 1000. If it still
> > doesn't work, it's not MTU trouble.
> 
> Changed that. The first attempt was successful, but this does not mean
> much so far.

Well, it certainly is better than if the first attempt was unsuccessful :)
Try it again several times, compare it to a group of tests getting placebo
(i.e., the original MTU), and see if you have a statistically-meaningful
relationship between the broken-ness of your mail connection to your MTU.

> > Did you ever notice other types of network connections broken by your setup?
> > Say, bulk downloads using FTP, or HTTP?
> 
> Nothing noticeable so far.

Strange. I'm not sure why MTU problems should have a more serious effect on
POP3 than on other types of TCP connections. But the real question is, of
course, whether reducing the MTU fixes your POP3 troubles or not. If it
does, you can spend the entire week trying to figure out why that happened ;)
(there are all kinds of crazy possibilities, like your firewall blocking
ICMP UNREACH_NEEDFRAG messages unless they belong to known sessions,
a similar firewall at the POP3's site (did you try ftp or http to the
same computer with the POP3 server?), etc).

-- 
Nadav Har'El                        |          Monday, Aug  6 2001, 17 Av 5761
nyh@math.technion.ac.il             |-----------------------------------------
Phone: +972-53-245868, ICQ 13349191 |Just remember that if the world didn't
http://nadav.harel.org.il           |suck, we would all fall off.

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