i have tried using standard 3g usb modems on ubuntu 11.04 has linux kernel version 2.38.8. on analyzing packet spacings of tcpdump capture, following pattern observed 8094 14 4 6 3 3985 see short packet spacing.
above spacings in microseconds 7 mbps 3g connection. on changing kernel 2.6.39 , short spacings in tens of microseconds no longer observed , replaced spacings in hundreds of microseconds. have identified changes brought in 2.6.39 rc 1 update. there many changes, difficult identify caused behavior.
so need information on part of linux kernel source code or drivers or modules used 3g usb modem. in locating code change appreciated.
you can find linux usb serial drivers in drivers/usb/serial, there's generic driver there (generic.c), you're using 1 of device specific ones (eg. option).
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