Modem stops sending IP packets after few minutes


I’m using a Fastrack supreme 20 (firmware 6.63) connected to a device (XSCALE based, with proprietary OS and PPP stack).
I’ve always used the modem only for sending blocks of data (about 100KB) through TCP connection, now I want to send UDP/RTP data continuously, but after some time, the modem stops sending data.

I’ve set up a simple test:

  1. start PPP connection
  2. then I send UDP data (1450bytes, all zeros) from the device to a static IP address (my PC), in a loop at about 4kbyte/s.
  3. the PC receives the data(in the meanwhile I use wireshark to check if data are arriving).
    It happens that after some time (usually a few minutes) data stops arriving to the PC.
    I’ve checked that UDP packets are sent to the modem, and the LCP echo command keeps returning ok. GPRS coverage seems ok. There’s no hardware flow control “stop” signal from the modem. It seems like he lost/changed the IP, but there’s no “NO CARRIER” or other AT messages (or I don’t know how to detect it).
    Then, if I reboot the modem (+++, AT+CFUN) and reconnect the PPP, all starts working well for some time, then happens the same.

Anyone has an idea about what’s happening?
Livio Bonisoli

l.bonisoli AT

ps: here’s the modem details:
Hardware Version 4.20
Production Date (W/Y): 21/2008
663c00gg.FSU002 1961896 122407 14:45