joe wrote:
> I'm new to linux and i was wondering why my conn. is
> so slow,.i havent played with ppp at all, just set it up through the
> network configuration.
There are several possibilities I can think of:
1. An overly pessimistic ASYNCMAP setting. Check your /etc/ppp/options
file(s) for the asyncmap parameters. If not set, it defaults to all ones
(ffffffff) which will escape all 32 control characters.
2. Poor choice of baud rate, perhaps automatically determined by the setup
script if you have an older serial interface (UART chip). If the kernel's
bootup messages report your serial ships as 16450 instead of 16550(A) or
later, this could be your problem.
3. Serial stream errors, usually caused by lost bytes due to some device
holding interrupts disabled for too long. To check it, while ppp is
connected, use the "ifconfig" command to show you the stats on the various
interfaces. Look for frame/crc/overrun errors on the receive and transmit
streams of the ppp0 device. If you see them, then this is the cause. The
usual culprit here is an IDE disk drive that operates with interrupts disabled
(sadly the default). Try "hdparm /dev/hda" to show your hard drive's
parameters, and try "hdparm /dev/hda -u 1" to enable "interrupt unmasking" -
most likely safe unless you have a really old hard drive. Obviously, change
/dev/hda to whatever is the device name of the IDE drive that has your Linux
partition on it. (Of course, warning/disclaimer: if you enable interrupt
unmasking, test it with "hdparm -t" to make sure your drive is compatible,
else you could suffer massive filesystem damage!!!)
4. Another possibility is the linux 2.2 kernel, which has a tendency of
omitting packets every so often, resulting in long delays until the sending
side realizes what has happened and resyncs. This one has stumped me
somewhat; I have reported it to the network developers, who seem to give up.
To diagnose this one, you need to be savvy enough to know how to use "tcpdump"
to capture the packets going across your network,and verify (on the senders
side) that the sender has forgotten the packets.
Kris
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