PPP Dialin server

[Stefan Saliba]

I have configured my linux box for dialin PPP access using pppd & mgetty. Well it works fine the only problem is that I cannot connect with a speed better then 33600. I set all deamons to connect to 115200 i.e. pppd and mgetty. I also set the serial port to spd_hi using the setserial command.

it seems like the modems are only negotiating V.34 speed. how can I go to V90 speed. both modems btw are 56K modems.


stefan

[Kofi ARTHIABAH]

Stefan:

The problem seems to be the initialisation strings for your modems. Both modems must have their initialisation strings (with the at commands) configured to attempt V90 before falling back.

The speeds you talk about only refer to the serial port to modem speed and not modem to modem speed. For modem to modem speed, a number of factors are involved - how good are the phone lines; how your modems are configured to negotiate etc.

you will find a line in your mgetty.config for initialising your modem - something like:
init-chat "" \d\d\d+++\d\d\dAT&FS2=255 OK ATN3S0=0S13.2=1 OK
you have to look up your modems documentation for information on which AT commands make the modem negotiate at v90.

Good luck

[Marco Paganini]

Hello Stefan,

Most modems have two speeds: The speed it connects to the other modem (max = 53k by FCC regulations, aka 56k) and the speed it connects to your computer (good idea to have this set higher than the modem max speed. A good candidate is 57600).

First, you have to find the command to put your modem in 'fixed speed mode'. If you don't do that, it will try to 'adjust' the serial speed to the connection speed. After you do that, just set your modem and serial to (say) 115200 or 57600 and you should be done.

Also, you can use PPPd itself to set the port speed (you don't need setserial).

Regards,
Paga

[Stefan Saliba]

Thanks for your help. I did play around with the init strings but to no avail.

But I think I found a conclusion to the problem. Well since I am trying to connect via two analouge land lines then I will never reach past V34 speed. Accroding to the V90 protocol to reach 56K the downstream is sent as PCM bits hence avoiding the D/A conversion at the telephone exchange and converted at the modem. Upstream is still V34 even in 56K. To send the PCM bits you need to have a special connection with the telephone exchange something which is digital like ISDN, E1,T1 or BRI. ISP's have these kind of connections but not me :(

Well I'll have to stick to v34

Thanks just the same

Stefan