# debug ppp connections & 3G modems?

## KarlisRepsons

I'd like someone, who has been doing it enough, to post the key ideas / links for debugging ppp connections and 3G modems...

It sounds broad, perhaps is too broad, but I've been struggling with ppp and it feels like I have too little debug output, too little feeling about what's going on. Some examples follow.

A bunch of problems might exist, last one I solved was like this: semi-accidentally I found a perl code fragment, which does small chat with modem and it turned out that "ATZ+CPIN" needs to be changed for "AT+CPIN". kppp didn't show anything to guess that PIN code entering failed... This time is different: if I just browse www, no problem, but as soon as I download some big file, speed grows fast until the connection is dropped /no, frozen, see below!/. Etc, etc -- I guess, one can have lots more of problems with these connections. But how to efficiently find out what's the real cause of them?Last edited by KarlisRepsons on Sun Jun 26, 2011 8:05 am; edited 1 time in total

----------

## BradN

Sometimes there is deliberate configuration by the ISP/mobile provider to discourage large file download on limited networking resources.  Unless you know that these limits don't occur on other setups (eg, windows), it's possible the ISP is doing it themselves.

A possible workaround might be limiting your bandwidth usage using iptables or whatever it is these days, or even with program configuration (for example, wget allows limiting download speed, and if that isn't enough, it allows resuming downloads).

----------

## KarlisRepsons

 *BradN wrote:*   

> Sometimes there is deliberate configuration by the ISP/mobile provider to discourage large file download on limited networking resources.

 

Doesn't seem anything like that... Ah, my mistake above: connection isn't really dropped (as it seems at least): pppd hangs and connection is rather frozen. The easiest way to recover is: unplug USB modem and plug in again... (at least I didn't find better)

 *BradN wrote:*   

> A possible workaround might be limiting your bandwidth usage using iptables or whatever it is these days, or even with program configuration (for example, wget allows limiting download speed, and if that isn't enough, it allows resuming downloads).

 

True, $(wget -c -T10 -t50 --limit-rate=70k URL) does the trick, but it's a disgust to do so...

----------

