- Mon Jun 11, 2007 6:14 am
#31144
Hi,
I've this setup: a GM862 connected to a PC port via level shitting hardware. Eveything seems to work fine: I have good communication with the modem, and I can launch a PPP session which succeeds. But then some problems arise:
- I can ping to a known IP address and it works, but with a >10% packet loss.
- I cannot resolve DNS names.
- Some TCP connections work. In particular, a wget http://www.whatismyip.org will work but an wget http://www.google.com won't.
That is, the problem SEEMS to be at the IP level, to which the modem should be transparent.
Has anyone faced this kind of problem before?.
ANY CLUE (really, ANY) WILL BE MUCH APPRECIATED-
Some thins I've ruled out to be the cause of the problem:
- Power supply: I use my own switching supply, but the problem is exactly the same if I use a 5A laboratory supply.
- Level shifting: I've tried several circuits and the problem doesn't change a bit.
- Operating system / pppd / whatever: tried another brand GPRS modem with the same software setup (and same SIM card) and everything worked fine.
- SIM: see above: used the very same SIM with another brand GPRS modem and problem disappears.
- Pigtail/antenna: I've tried three different pigtails and two different antennas. Plus the signal quality seems to be fine in all cases (AT+CSQ? = 18,7).
The ping/wget thing points to a packet loss problem, but then, DNS resolution should have worked at least ONE in the thousand times I've tried it. But even if it was a packet loss problem (at the GPRS level, which would show up at the TCP/IP level), I still wouldn't have a clue about the cause of the problem: the power supply is OK, and the RF part is OK too.
Again, any clues?
Regards.
I've this setup: a GM862 connected to a PC port via level shitting hardware. Eveything seems to work fine: I have good communication with the modem, and I can launch a PPP session which succeeds. But then some problems arise:
- I can ping to a known IP address and it works, but with a >10% packet loss.
- I cannot resolve DNS names.
- Some TCP connections work. In particular, a wget http://www.whatismyip.org will work but an wget http://www.google.com won't.
That is, the problem SEEMS to be at the IP level, to which the modem should be transparent.
Has anyone faced this kind of problem before?.
ANY CLUE (really, ANY) WILL BE MUCH APPRECIATED-
Some thins I've ruled out to be the cause of the problem:
- Power supply: I use my own switching supply, but the problem is exactly the same if I use a 5A laboratory supply.
- Level shifting: I've tried several circuits and the problem doesn't change a bit.
- Operating system / pppd / whatever: tried another brand GPRS modem with the same software setup (and same SIM card) and everything worked fine.
- SIM: see above: used the very same SIM with another brand GPRS modem and problem disappears.
- Pigtail/antenna: I've tried three different pigtails and two different antennas. Plus the signal quality seems to be fine in all cases (AT+CSQ? = 18,7).
The ping/wget thing points to a packet loss problem, but then, DNS resolution should have worked at least ONE in the thousand times I've tried it. But even if it was a packet loss problem (at the GPRS level, which would show up at the TCP/IP level), I still wouldn't have a clue about the cause of the problem: the power supply is OK, and the RF part is OK too.
Again, any clues?
Regards.