ppp.conf "set speed" && UMTS

[Aleksandr Rybalko]

On Tue, 27 Dec 2011 13:22:51 +0100
Matthias Apitz <guru at unixarea.de> wrote:

>> 
>> Hello,
>> 
>> I'm using PPP with an USB UMTS stick (Huawei E1750). The speed for
>> upload and download can be measured with, for example, pages like:
>> http://www.speedtest.net/
>> the results vary of course a bit, but usually they are between
>> 1 and 4 Mbps;
>> 
>> how those values fit with the speed of the device /dev/cuaU0.0 which
>> I set in ppp.conf to the maximum value as 
>> 
>> set speed 921600
>> 
>> and as well in /usr/include/sys/_termios.h I don't see any higher
>> possible speed for the interface... do I miss something?
>> 

Hi Matthias,
IIRC "set speed" ignored for USB modems (only USB-to-serial or USB
dialup modems use it).

Some time ago I deal with that problem for linux based devices and
found that problem may be fixed by ignore reported USB endpoint
transfer size. Some devices report it with value 0x200 (512 bytes) but
works fine with 0x1000 (4096). And with last value give much bigger
throughput.

This is wMaxPacketSize value in `usbconfig -u 4 -a 2
dump_curr_config_desc` output.

u3g driver already set it to 2048, if your modem hooked by another
driver try to change it from 0 (use reported) to 2048/4096.

>> Thanks
>> 
>> 	matthias
>> -- 
>> Matthias Apitz
>> e <guru at unixarea.de> - w http://www.unixarea.de/
>> UNIX since V7 on PDP-11, UNIX on mainframe since ESER 1055 (IBM /370)
>> UNIX on x86 since SVR4.2 UnixWare 2.1.2, FreeBSD since 2.2.5
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-- 
Alexandr Rybalko <ray at dlink.ua> 
aka Alex RAY <ray at ddteam.net>