10 Data Transfer related issues

Contents of this section

10.1 The ftp transfers seems to die when I do a `put' operation. They will work correctly if I `get' a file. Why?

Do you have the flow control enabled? Flow control is set by the pppd option crtscts for RTS/CTS and xonxoff for XON/XOFF. If you don't enable the flow control then you will probably overrun the modem's buffers and this will prove to be disastrous with vj header compression.

10.2 How do I use XON/XOFF for flow control?

The better flow control is CTS/RTS. However, if you can not do the hardware flow control with the signals CTS and RTS, then use XON/XOFF. The following three steps need to be performed.

10.3 The modem seems to always connect at a strange rate. When I use minicom, the modem will always use 14400. However, PPP is using 9600 or 7200 or even 2400. How do I fix this?

Put the desired rate as an option to the pppd process. If you don't put the rate, then pppd process will use whatever rate is set currently at the time. Not all programs will restore all of the parameters to the previous settings properly upon exit. This may lead to strange rates configured for the serial device.

10.4 The ftp transfers seems to be very slow when I do a `get' operation. The `put' operation is much faster. Why?

Did you specify the option:

asyncmap 0

when you ran pppd? If you forgot the option, the peer must quote (double) all of the control characters in the range from 00 to 1F (hex). This will result in a statistical loss of about 12.5% in speed for all of the data which you receive.

Did you configure the remote system? If so, did you forget flow control on its modem?

10.5 The proxyarp function fails to find the hardware address.

Use the ppp-2.1.2d.tar.gz package. The pppd process was erroneously compiled with the 1.1.8 kernel and it used Net-3 rather than Net-2 definitions.

Additionally, you should refer to the proxy-ARP mini-HOWTO about the requirements for using proxy-ARP.

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