Are these normal PPP speed rates thru serial ports?

Are these normal PPP speed rates thru serial ports?

Post by Spiliopoulos Chr » Sat, 26 Aug 1995 04:00:00



I tried to setup a PPP link through the serial ports of 2 Linux PC's
(connected with a null modem cable 1 m long). The link I got was very
nice and reliable; yet the speed and transfer rates were REALLY low...

This is what I got:

for 9600   PPP link -->  ping: 280ms   | ftp transfer rate: 0.87 Kbytes/s
for 19200  PPP link -->  ping: 100.3ms |
for 38400  PPP link -->  ping: 60ms    | ftp transfer rate: 2.0 Kbytes/s
for 57600  PPP link -->  ping: 1480ms  |
for 115200 PPP link -->  ping: 2219ms...
                              ...6000ms

Best ping times where obtained at 38400 (I didnt setserial in any of the above).

1) Are these times quite reasonable? (I wasnt expecting Ethernet speeds but
   nevertheless this was WAY slower than the transfer rates I got using
   same exact setup with DOS's 'interlink' utility.

   [Perhaps one explanation would be the different protocol layers the datagrams
   have to go through?]

2) The ping times via the 115200 PPP link were increasingly getting higher
   with time. They started at  2219 bps and about a minute later had reached
   6000ms...!

3) Has anyone tried PLIP with parallel ports?
   I compiled kernel with plip support but didnt see it showing up in the
   boot messages (althought the SLIP, PPP, and CSLIP that I also added in
   _did_ show...). Anybody know why?

Thanks a lot, looking forward to your feedback.
(Special thanks to Diep, Matt L. and Chris R. who wrote me)

Chris

--------

 
 
 

Are these normal PPP speed rates thru serial ports?

Post by Christer Olss » Tue, 29 Aug 1995 04:00:00


|> for 9600   PPP link -->  ping: 280ms   | ftp transfer rate: 0.87 Kbytes/s
|> for 19200  PPP link -->  ping: 100.3ms |
|> for 38400  PPP link -->  ping: 60ms    | ftp transfer rate: 2.0 Kbytes/s
|> for 57600  PPP link -->  ping: 1480ms  |
|> for 115200 PPP link -->  ping: 2219ms...
|>                               ...6000ms
|>
|>
|>
|> Best ping times where obtained at 38400 (I didnt setserial in any of the above).
|>
|> 1) Are these times quite reasonable? (I wasnt expecting Ethernet speeds but
|>    nevertheless this was WAY slower than the transfer rates I got using
|>    same exact setup with DOS's 'interlink' utility.

I don't think one of your machines has buffred UARTs like 16550. It seems your
machine cannot send/receive more than 2000 byte/sek, i.e near 19200 bps.

In 57600 and 115200, your machines drops so many packets and need resend them..
No wonder why you got so high pingtimes..

 
 
 

Are these normal PPP speed rates thru serial ports?

Post by Thomas J. Eva » Wed, 30 Aug 1995 04:00:00




|>
|> |> for 9600   PPP link -->  ping: 280ms   | ftp transfer rate: 0.87 Kbytes/s
|> |> for 19200  PPP link -->  ping: 100.3ms |
|> |> for 38400  PPP link -->  ping: 60ms    | ftp transfer rate: 2.0 Kbytes/s
|> |> for 57600  PPP link -->  ping: 1480ms  |
|> |> for 115200 PPP link -->  ping: 2219ms...
|> |>                               ...6000ms
|> |>
|> |>
|> |>
|> |> Best ping times where obtained at 38400 (I didnt setserial in any of the above).
|> |>
|> |> 1) Are these times quite reasonable? (I wasnt expecting Ethernet speeds but
|> |>    nevertheless this was WAY slower than the transfer rates I got using
|> |>    same exact setup with DOS's 'interlink' utility.
|>
|> I don't think one of your machines has buffred UARTs like 16550. It seems your
|> machine cannot send/receive more than 2000 byte/sek, i.e near 19200 bps.
|>
|> In 57600 and 115200, your machines drops so many packets and need resend them..
|> No wonder why you got so high pingtimes..
Ping packets aren't re-transmitted, if they are dropped, they are lost.
I gotta believe the speed of the link is not set correctly.

--
Tom Evans  TCP/IP Development

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