[H-GEN] PPP problems

[Byron Ellacott]

[ Humbug *General* list - semi-serious discussions about Humbug and ]
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On Wed, 19 Jan 2000, Michael Anthon wrote:

> Pretty much most modem connections established these days would (I guess..
> no hard facts to support me here) be using error correction on the modem
> connection itself.  In this situation, setting the MTU/MRU to a lower value

[ben carlyle's explanation is correct, and useful, but not complete]

Most modem connections do use error detection and/or correction, although
it is turned off occasionally to try and improve performance.  However,
even when it is on, it is no guarantee that you will not have errors in a
modem bitstream.  Modem error detection/correction uses relatively few
bits, and has an entropy high enough that errors can slip through.  These
errors are usually detected by the next networking layer, but there is a
(much smaller) chance that errors could slip there, which is why the
TCP/IP protocol suite have checksums on every layer (physical, IP, TCP or
UDP).

Some of them are only header checksums, but I forget which.
The RFCs are, of course, the second most reliable source, the most
reliable being the code for whichever stack you're using.

What this means is retransmission can occur on modern modems, especially
on noisy lines, and especially when your init string drops error
correction, which is often done by online gamers.

--
bje


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