Baseband behavior on IMSI change » History » Revision 5
Revision 4 (neels, 02/25/2020 07:40 PM) → Revision 5/9 (neels, 02/25/2020 11:49 PM)
h1. Baseband behavior on IMSI change h1. With "Proactive SIM" REFRESH command According to ETSI TS 101 267 / 3GPP TS 11.14 section 6.4.7.1 "EF IMSI changing procedure", after changing EF-IMSI, valid REFRESH qualifiers are * "SIM Initialization and File Change Notification" * "SIM Initialization and Full File Change Notification" * "SIM Reset" h2. ATT == 1 (Channel Description: Attach = yes) h3. Samsung Galaxy S4m * phone displays "Refreshing SIM" (notification bubble on display, probably annoying to the user) * immediate IMSI Detach * 15 seconds delay of being detached * Location Updating (IMSI Attach) with previous TMSI (!) * MSC has forgotten the TMSI due to IMSI detach (OsmoMSC peculiarity, usually an MSC should still have the TMSI) * Identity Request & Response yields new IMSI TODO h1. Without "Proactive SIM" REFRESH command | phone | chipset | behavior scheme | directly when writing new IMSI to SIM file | on CM Service Request | after periodical LU period | after flight mode / phone restart | on Identity Request | | Nokia | | (I) | no reaction | uses previous TMSI | uses previous TMSI | uses previous TMSI | returns new IMSI | | Samsung Galaxy S4m | | (I) | no reaction | uses previous TMSI | uses previous TMSI | uses previous TMSI | returns new IMSI | h1. Phones Keep the h2. (I) Keeps TMSI Even though the IMSI has changed, the Baseband remains actively attached. On contact with the core network, it uses the last TMSI, and hence looks as if it remained completely unchanged, keeps using the previous identity. After a power cycle, it also uses the last TMSI. When the MSC has forgotten the last TMSI (e.g. due to IMSI Detach), the Identity Request is answered with the new IMSI, and the phone has thus switched to the new identity. Needs to Needs: * make sure the MSC forgets forget the TMSI. TMSI * trigger baseband activity to cause a re-attach with the new IMSI
