Re: low throughput on PPP link
Gregory Guthrie wrote:
> At 09:35 AM 6/2/98 -0500, Jens B. Jorgensen wrote:
> >> > >Well, you need to pass the speed to pppd as 115200, not 57600. You
> see, the
> >> > >set_serial spd_vhi flag sets what speed will be used if 38400 is
> selected.
> >> > >However, pppd can set the speed to 115200 just fine if you specify
> it. You're
> >> > >specifying 57600 and that's what you're getting.
> -- Does this mean;
>
> 1) setting 115200 is independent of any setting of {normal,hi,vhi}, or s
> there an interaction, and thus only certain valid pairs.
it is independant and is not affected by the normal, hi, vhi flags. These come
into affect when the program tries to set the speed to 38400.
> 2) Is the report of Baud-base rate from "seterial -a" the bottom line, it
> says 115200 and normal.
> lrouter# setserial -a /dev/ttyS0
> /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_normal skip_test session_lockout
>
> But, "stty -a < /dev/ttyS0" says baud = 57600.
>
> If so, I still wonder why we are only getting ~< 56K throughput..
baud_base refers to the clock attached to the 16550A. You see, the 16550A can
actually do much higher than 115200 but it is limited by the clock which is
included by the manufacturer. Some faster speed boards just have a regular 16550A
(or clone) but include a faster clock. You can then use these cards by changing
the baud_base and divisor. (I've not done this so I may be confusing the details
of which are set for what, but you get the gist of it.)
--
Jens B. Jorgensen
jjorgens@bdsinc.com
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