Revision 206a0fa9
Added by osmith about 4 years ago
| docs/imsi-pseudo-spec.adoc | ||
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After the VLR found the authentication challenge, it authenticates the SIM, and |
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performs a Classmark Enquiry and Physical Channel Reconfiguration. Then the VLR |
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has the required information to finish the Location Updating, and continues |
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with an Update Location Request procedure with the HLR. Afterwards, the VLR |
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assigns a new TMSI with the Location Updating Accept, which is acknowledged by |
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the TMSI Reallocation Complete. In following Location Updates with the same |
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MSC, the ME sends the TMSI instead of the IMSI in the Location Updating |
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Request. |
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with Process Update_Location_HLR (3GPP TS 29.002). Afterwards, the VLR assigns |
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a new TMSI with the Location Updating Accept, which is acknowledged by the TMSI |
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Reallocation Complete. In following Location Updates with the same MSC, the ME |
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sends the TMSI instead of the IMSI in the Location Updating Request. |
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[[figure-imsi-regular]] |
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.Location Updating in 2G CS with IMSI |
| ... | ... | |
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BTS => BSC [label="Ciphering Mode Complete"]; |
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BSC => MSC [label="Ciphering Mode Complete"]; |
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--- [label="Process Update_Location_HLR (3GPP TS 29.002)"]; |
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MSC => HLR [label="Update Location Request"]; |
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MSC <= HLR [label="Insert Subscriber Data Request"]; |
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MSC => HLR [label="Insert Subscriber Data Result"]; |
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MSC <= HLR [label="Update Location Result"]; |
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---; |
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BSC <= MSC [label="Location Updating Accept"]; |
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BTS <= BSC [label="Location Updating Accept"]; |
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// FIXME: do we need to enforce the LU now, with an arbitrary CM Service |
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// Request, or would this only be necessary for Osmocom? (OS#4404) |
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=== Successful Location Update With Pseudonymous IMSI |
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=== Process Update_Location_HLR |
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All IMSI Pseudonymization related changes to Process Update_Location_HLR |
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(3GPP TS 29.002) are optional. |
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* HLR looks up subscriber by pseudonymous imsi in Update Location Request |
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* if two pseudo imsi found, and connected with new one: dealloc old entry |
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* if two pseudo imsi found and connected with old one: do not dealloc! |
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// HLR may choose not to give out next IMSI if it is short on available IMSIs |
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* after update location result: set new timer for sending next IMSI to random delay |
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==== Send Next Pseudonymous IMSI |
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* if subscriber has two pseudo IMSI, send the new one |
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* if subscriber has only one pseudo IMSI: |
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* abort if not enough IMSIs available |
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* generate new pseudo IMSI as described earlier |
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* set imsi_pseudo_i like last one + 1 |
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* send SMS to subscriber's SIM |
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[[sms-format]] |
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==== Format of the SMS
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==== SMS Format
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* min_sleep_time |
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* imsi_pseudo |
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* imsi_pseudo_i |
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=== Next Pseudonymous IMSI Arrives Via SMS |
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[[figure-]] |
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.Process Update_Location_HLR with IMSI pseudonymization changes |
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["mscgen"] |
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---- |
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msc {
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hscale="1.75"; |
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MSC [label="MSC/VLR"], SMSC [label="SMS-SC"], HLR [label="HLR"]; |
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MSC => HLR [label="Update Location Request"]; |
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HLR box HLR [label="\nDeallocate old Pseudonymous IMSI,\n if new Pseudonymous IMSI was used\n"]; |
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MSC <= HLR [label="Insert Subscriber Data Request"]; |
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MSC => HLR [label="Insert Subscriber Data Result"]; |
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HLR box HLR [label="Start Next_Pseudo_IMSI_Timer"]; |
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MSC <= HLR [label="Update Location Result"]; |
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MSC box MSC [label="Finish Location Updating with ME"], |
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HLR box HLR [label="Wait for Next_Pseudo_IMSI_Timer expiry"]; |
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|||; |
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...; |
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|||; |
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HLR box HLR [label="Next_Pseudo_IMSI_Timer expired"]; |
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HLR box HLR [label="\nAllocate new Pseudonymous IMSI\nif subscriber only has one allocated\n"]; |
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SMSC <= HLR [label="Next Pseudonymous IMSI SMS"]; |
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SMSC box SMSC [label="Deliver SMS to ME"]; |
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} |
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---- |
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== Error Scenarios |
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=== Next Pseudonymous IMSI SMS is Lost |
Also available in: Unified diff
spec: Process Update_Location_HLR: bullet points + graph