low throughput on PPP link

[Gregory Guthrie <guthrie@mum.edu>]

Currently we are building two Debian boxes(2.0.30) running as routers with a
PPP link in between. Things are mostly going fine except the link throughput.
56kbps is the best it gets while we are expecting over 100kbps since we are
using the 16550A UART serial cards, trying for 115K..

Here's the details:
====== serial port settings =====================
/dev/ttyS0, Line 0, UART: 16550A, Port: 0x03f8, IRQ: 4
        Baud_base: 115200, close_delay: 50, divisor: 0
        closing_wait: 3000, closing_wait2: infinte
        Flags: spd_vhi skip_test session_lockout


====== ppp link settings ========================
pppd persist passive proxyarp /dev/ttyS0 57600 &        (local)
pppd persist passive defaultroute /dev/ttyS0 57600 &    (remote)


The reason why we didn't set the speed up to 115200 in pppd is that it
will bring the link down! (while using Slackware doesn't have this situation)

We were acknowledged that a combination of 
"setserial -b /dev/ttyS0 spd_vhi"    and 
"pppd persist passive proxyarp /dev/ttyS0 38400 &" 
   should achieve the full speed
of 115200, yet the testing result we have is just slower that using 57600.

Not any clue in Robert Hart's Linux PPP HOWTO, nor in "The Linux Serial HOWTO
by Greg Hankins". Any pointer?
Thanks in advance.

Xiangyang Ha


--------------------------------------------------------
Xiangyang Ha		
xha@cs.mum.edu          
Computer Science Department
College of Science and Technology
Maharishi University of Management
(Maharishi International University 1971-1995)
--------------------------------------------------------



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