Re: "connection timed out" problem

ibuprofin@painkiller.example.tld (Moe Trin) wrote in
news:slrne30963.j5v.ibuprofin@compton.phx.az.us:

<Snipola>
> An MTU of 576 was set back in the old days of 19200 BPS modems to allow
> a command echo at a reasonable rate - think "telnet" where what you
> typed as commands were actually echoed back to your screen from the
> remote server. The "reasonable time" is around a quarter second. Your
> modem is undoubtedly faster than 19.2, and most ppp implementations
> default to an MTU of 1500. Setting the MTU (actually the MRU - Received)
> can cause problems where ICMP is blocked between you and the server. See
> RFC2923 - briefly, the server tries to send large (1500 byte) packets
> with a Don't Fragment flag set in the headers (for speed). When that
> packet reaches a pipe with a smaller MTU, the router tries to send back
> an error message to the server (ICMP Type 3 Code 4 - "ten pounds don't
> fit in a five pound bag"). If that error message gets dropped, the
> server never gets the word to reduce the packet size, and the connection
> is broken.
>
> Old guy

So, do you recommend getting rid of this setting? I do have a 56k
modem. Would have DSL if I wasn't so far from the switch.

As an aside, I went back to my older modem as I can use a command
string to set its max connect speed. My newer modem is missing those
commands and therefore it connects too fast for the line noise, and
therefore it kept dropping connections.

If it weren't for my days BBSing I wouldn't have even known about
those settings.

Brian

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