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spec: Process Update_Location_HLR: bullet points + graph

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Oliver Smith 2020-04-07 14:30:07 +02:00
parent 8b68e4ec9e
commit 206a0fa9a1
1 changed files with 51 additions and 9 deletions
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docs/imsi-pseudo-spec.adoc
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@ -53,11 +53,10 @@ Location Updating procedure.
After the VLR found the authentication challenge, it authenticates the SIM, and
performs a Classmark Enquiry and Physical Channel Reconfiguration. Then the VLR
has the required information to finish the Location Updating, and continues
with an Update Location Request procedure with the HLR. Afterwards, the VLR
assigns a new TMSI with the Location Updating Accept, which is acknowledged by
the TMSI Reallocation Complete. In following Location Updates with the same
MSC, the ME sends the TMSI instead of the IMSI in the Location Updating
Request.
with Process Update_Location_HLR (3GPP TS 29.002). Afterwards, the VLR assigns
a new TMSI with the Location Updating Accept, which is acknowledged by the TMSI
Reallocation Complete. In following Location Updates with the same MSC, the ME
sends the TMSI instead of the IMSI in the Location Updating Request.
[[figure-imsi-regular]]
.Location Updating in 2G CS with IMSI
@ -100,10 +99,12 @@ msc {
BTS => BSC [label="Ciphering Mode Complete"];
BSC => MSC [label="Ciphering Mode Complete"];
--- [label="Process Update_Location_HLR (3GPP TS 29.002)"];
MSC => HLR [label="Update Location Request"];
MSC <= HLR [label="Insert Subscriber Data Request"];
MSC => HLR [label="Insert Subscriber Data Result"];
MSC <= HLR [label="Update Location Result"];
---;
BSC <= MSC [label="Location Updating Accept"];
BTS <= BSC [label="Location Updating Accept"];
@ -188,18 +189,59 @@ next SMS. Afterwards, the EF~IMSI~ changing procedure in 3GPP TS 11.14, Section
// FIXME: do we need to enforce the LU now, with an arbitrary CM Service
// Request, or would this only be necessary for Osmocom? (OS#4404)
=== Successful Location Update With Pseudonymous IMSI
=== Process Update_Location_HLR
// HLR may choose not to give out next IMSI if it is short on available IMSIs
All IMSI Pseudonymization related changes to Process Update_Location_HLR
(3GPP TS 29.002) are optional.
* HLR looks up subscriber by pseudonymous imsi in Update Location Request
* if two pseudo imsi found, and connected with new one: dealloc old entry
* if two pseudo imsi found and connected with old one: do not dealloc!
* after update location result: set new timer for sending next IMSI to random delay
==== Send Next Pseudonymous IMSI
* if subscriber has two pseudo IMSI, send the new one
* if subscriber has only one pseudo IMSI:
* abort if not enough IMSIs available
* generate new pseudo IMSI as described earlier
* set imsi_pseudo_i like last one + 1
* send SMS to subscriber's SIM
[[sms-format]]
==== Format of the SMS
==== SMS Format
* min_sleep_time
* imsi_pseudo
* imsi_pseudo_i
=== Next Pseudonymous IMSI Arrives Via SMS
[[figure-]]
.Process Update_Location_HLR with IMSI pseudonymization changes
["mscgen"]
----
msc {
hscale="1.75";
MSC [label="MSC/VLR"], SMSC [label="SMS-SC"], HLR [label="HLR"];
MSC => HLR [label="Update Location Request"];
HLR box HLR [label="\nDeallocate old Pseudonymous IMSI,\n if new Pseudonymous IMSI was used\n"];
MSC <= HLR [label="Insert Subscriber Data Request"];
MSC => HLR [label="Insert Subscriber Data Result"];
HLR box HLR [label="Start Next_Pseudo_IMSI_Timer"];
MSC <= HLR [label="Update Location Result"];
MSC box MSC [label="Finish Location Updating with ME"],
HLR box HLR [label="Wait for Next_Pseudo_IMSI_Timer expiry"];
|||;
...;
|||;
HLR box HLR [label="Next_Pseudo_IMSI_Timer expired"];
HLR box HLR [label="\nAllocate new Pseudonymous IMSI\nif subscriber only has one allocated\n"];
SMSC <= HLR [label="Next Pseudonymous IMSI SMS"];
SMSC box SMSC [label="Deliver SMS to ME"];
}
----
== Error Scenarios
=== Next Pseudonymous IMSI SMS is Lost