Holger Hans Peter Freyther wrote:
* there is no indication to the SGSN for dropped
frames/octets?
* can't the DL-TBF be re-associated/updated after the assignment
is done again?
hi holger,
there is one issue about failed downlink TBF: the PCU does not do any
retry. when the assignment is sent to the phone and it fails, there is
no retry according to the specs. i assume that this is a task for the
SGSN. osmo-sgsn/openggsn does not resend any LLC frame in case of
LLC-DISCARDED message, if i look at the source code of libosmogb.
(LLC-DISCARDED is forwarded at bssgp_rx_llc_disc() of gprs_bssgp.c, but
i don't see where it is handled.)
what actually happens is that TCP layer will do the resend, but this is
a problem, especially at the border of coverage where many downlink
assignments get lost.
i have once enabled the debugging at ipaccess BTS and saw that the PCU
itself does the retry of lost downlink assignments (4 or 5 times).
regards,
andreas