Hi, I would say the RLCMAC side looks fine. It looks like the SGSN is rejecting the ATTACH REQUEST. You may have a misconfiguration in the encryption config of osmo-sgsn? Unfortuantely, your pcap doesn't contain the contents of the Gb interface ("gprs-ns" filter in wireshark), so it's difficult to say what's going on. Please share a pcap containing gprs-ns (PCU<->SGSN) and gtp (SGSN<->GGSN) packets in order to find out what's going on. Share also a log file of osmo-sgsn (or use gsmtap log) with debug enabled to find out why is the SGSN rejecting it. Regards, Pau -- - Pau Espin Pedrol <pespin@sysmocom.de> http://www.sysmocom.de/ ======================================================================= * sysmocom - systems for mobile communications GmbH * Alt-Moabit 93 * 10559 Berlin, Germany * Sitz / Registered office: Berlin, HRB 134158 B * Geschaeftsfuehrer / Managing Director: Harald Welte