Bug #6333
closed
Describe UE/ePDG-initiated Detach Procedure
Added by pespin 4 months ago.
Updated 3 months ago.
Description
Related: 3GPP TS 23.402 section 7.4 "Detach and PDN Disconnection for S2b", and specifically section "7.4.3 UE/ePDG-initiated Detach Procedure and UE-Requested PDN
Disconnection with GTP on S2b".
That section explains (vaguely) that the UE can initiate a procedure to detach from ePDG. Sequence diagram Figure 7.4.3-1 refers to "Detach procedure as in Figure
7.4.1-1, before step (A)", which state: "IKEv2 tunnel release trigger".
lynxis can you clarify what does that exactly mean/involve at strongswan side between UE<->strongswan? Not sure if you already looked at / though about this scenario.
We probably also need to define messages between strongswan <> osmo-epdg to forward this.
Again, not sure if you need a response ePDG->strongswan you can answer the UE, please provide feedback here. According to Figure 7.4.1-1, we need a "6. Non-3GPP specific
resource release procedure".
Finally, once we figure the message type in CEAI, we have to implement in osmo-epdg:
- Tx DeleteSessionReq to PGW
- Rx DeleteSessionResp from PGW
lynxis can you clarify what does that exactly mean/involve at strongswan side between UE<->strongswan?
[UE] --closes IPsec tunnel-> [strongswan] --GSUP/Purge MS Request--> [osmo-epdg] --S2b/GTPv2/Delete Session Request-> [PGW]
[osmo-epdg] --SWx/ServerAssignment Type=User Deregistration--> [HSS]
TODO: check S6b
When the network decides to register:
[UE] <--closes IPSec tunnel-- [strongswan] <--GSUP/Cancel Location-- [osmo-epdg] <--SWx/Registration-Termination-Request-- [HSS]
[osmo-epdg] --S2b/GTPv2/Delete Session Request-> [PGW] (unsure if GTPv2 should be closed before or after IPSec)
TODO: check S6b
- Assignee changed from lynxis to pespin
We might also need to talk S6b.
- Status changed from Feedback to In Progress
lynxis Thanks I'll start implementing the 2 use cases above in TTCN3 and osmo-epdg tomorrow.
After a lot of code improvement and rework in osmo-epdg, I have a proper split between ePDG and AAA nodes (communication between them is now through erlang messages, but the messages are kinda similar to those in the specs, and handled mostly asynchronously). This allowed me, together with the FSMs, to implement the related messages to have UE-initiated detach implemented.
Other previous refactoring patches have already been merged in osmo-epdg.git master, the following I just submitted to gerrit:
https://gerrit.osmocom.org/c/erlang/osmo-epdg/+/35759 AAA-Server: Process S6b, SWx requests async through new aaa_ue_fsm [NEW]
https://gerrit.osmocom.org/c/erlang/osmo-epdg/+/35760 Send SAR to HSS when all sessions are terminated
TTCN3 test passing now showcasing the scenario:
https://gerrit.osmocom.org/c/osmo-ttcn3-hacks/+/35758 epdg: Test UE-initiated Detach Procedure
Once merged I think we can close this ticket.
- Status changed from Feedback to Resolved
pespin wrote in #note-7:
Once merged I think we can close this ticket.
they are merged, closing.
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