forked from acouzens/open5gs
Pau Espin
60691b02d2
In an Inter-RAT setup a UE could perform a TAU coming from a 2G/3G network.
In that case the UE/MS is unknown to the MME and it should request the
SGSN context (MM, PDP) from the old SGSN. This is done through the following
GTPv1C message exchange on the Gn interface of SGSN and MME:
SGSN <- MME: SGSN Context Request
SGSN -> MME: SGSN Context Response
SGSN <- MME: SGSN Context Acknowledge
Diagram with full set of steps can be found at 3GPP TS 23.401 D.3.6.
This commit doesn't aim to be a complete implementation of the mentioned
procedure, since it's quite a complex one, with lots of fields and logic
required. This so far only implements in general the minimally
successful case by filling as much as possible the required set of
fields.
This will allow for a base onto which do incremental improvements and
fixes while testing against UEs and SGSNs (such as osmo-sgsn, which
doesn't yet support this procedure but will potentially earn it soon).
The reverse direction, aka UE issuing cell reselection 4G->2G was
already implemented (same as here, initial non-complete implementation)
in open5gs-mmed in commit
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| amf | ||
| ausf | ||
| bsf | ||
| hss | ||
| mme | ||
| nrf | ||
| nssf | ||
| pcf | ||
| pcrf | ||
| scp | ||
| sepp | ||
| sgwc | ||
| sgwu | ||
| smf | ||
| udm | ||
| udr | ||
| upf | ||
| main.c | ||
| meson.build | ||