[AMF] Implicit Network-initiated Deregistration
Two timers are introduced (both with duration of T3512 + 4 min):
-MOBILE_REACHABLE
-IMPLICIT_DEREGISTRATION
MOBILE_REACHABLE is set when NAS connection for the UE is released.
IMPLICIT_DEREGISTRATION is set when MOBILE_REACHABLE expires.
On MOBILE_REACHABLE expiry Paging is ignored.
On IMPLICIT_DEREGISTRATION expiry:
-UE's RM_State is set to DEREGISTERED
-UE is Nudm_SDM_Unsubscribed
-UE is Nudm_UECM_Deregistered
-PDU sessions are released
-AM policies are deleted
Existing flag amf_ue->network_initiated_de_reg is used.
Two timers are introduced (both with duration of T3512 + 4 min):
-MOBILE_REACHABLE
-IMPLICIT_DEREGISTRATION
MOBILE_REACHABLE is set when NAS connection for the UE is released.
IMPLICIT_DEREGISTRATION is set when MOBILE_REACHABLE expires.
On MOBILE_REACHABLE expiry Paging is ignored.
On IMPLICIT_DEREGISTRATION expiry:
-UE's RM_State is set to DEREGISTERED
-UE is Nudm_SDM_Unsubscribed
-UE is Nudm_UECM_Deregistered
-PDU sessions are released
-AM policies are deleted
Existing flag amf_ue->network_initiated_de_reg is used.
The current load percentage of the NF Service Consumer is provided
in the payload body of the PATCH request when periodically
contacting the NRF (heart-beat).
AMF: ratio between currently connected ran_ue and maximum number of them
SMF: ratio between current PDU sessions and maximum available
PCF: ratio between current AM+SM policy associations and maximum available
or ratio between currently connected UEs and maximum number of them
(the load which is higher)
AUSF, UDM: ratio between currently connected UE and maximum number of them
BSF: ratio between current sessions and maximum available
NSSF: ratio between currently used NSIs and maximum number of them
NRF currently doesn't determine that the NF Profile has changed.
Expose RM metrics with labels according to ETSI TS 128 552 V16.13.0 in
AMF by using hash.
The metrics are named respecting the rule:
<generation>_<measurement_object_class>_<measurement_family_name>_<metric_name_as_in_TS_128_552>
Since slice itself is not unique, the plmnid label is exposed in
addition to snssai.
RegInitFail is exposed as an alternative to RegInitReq and RegInitSucc
counters so cause label can be provided. It counts rejected registrations
and rejected authentications.
Rejected authentications are counted under label cause="0".
Exposed metrics example:
-standard gauge:
fivegs_amffunction_rm_registeredsubnbr{plmnid="00101",snssai="1000009"} 1
-nonstandard counter:
fivegs_amffunction_rm_reginitfail{cause="3"} 4
AMF subscribes to UDM for each registered UE.
At the moment, UDM does not send callback to AMF when any of the UE's
properties in the database changes.
At the moment, AMF does properly parse the ModificationNotification, but
does not do anything useful.
UDM may send a Deregistration Notification to AMF, to deregister
specific UE from the network - Network-Initiated Deregistration.
Deregistration procedure includes sending Deregistration Request to UE,
starting a timer T3522, releasing PDU sessions from SMF, releasing PCF
policies from PCF, and waiting for Deregistration Accept from UE.
Not yet implemented is:
- to prevent deregistration of UE in case it has any emergency sessions,
- page UE when UE is in IDLE mode.
During PDU Session Establishment,
if gNB sends PDUSessionResourceReleaseResponse,
AMF was crashed.
In this case, AMF/SMF remove Session Context and sends ErrorIndication.
Confirmation for non-cleartext IE should only be applied
to the initial NAS message. Registration requests and Service requests
with UplinkNASTransport do not have to.
1. DownlinkNASTransport
If AMF has not sent it previously, UE-AMBR is included in Registration
accept.
2. InitialContextSetupRequest
If PDUSessionResourceSetup is available, UE-AMBR is included
3. PDUSessionResourceSetupRequest
If AMF has not sent it previously, UE-AMBR is included
4. HandoverRequest
If PDUSessionResourceSetup is available, UE-AMBR is included
The AMF shall assign a new 5G-GUTI for a particular UE:
a) during a successful initial registration procedure;
b) during a successful registration procedure
for mobility registration update; and
c) after a successful service request procedure invoked as a response
to a paging request from the network and before the release
of the N1 NAS signalling connection as specified in subclause 5.4.4.1.
The AMF should assign a new 5G-GUTI for a particular UE
during a successful registration procedure
for periodic registration update. The AMF may assign a new 5G-GUTI
at any time for a particular UE by performing
the generic UE configuration update procedure.
If both Delete-Session-Request/Response and
UEContextReleaseCommand/UEContextReleaseComplete are failed at the same time,
UE cannot attach to the EPC infinitely.
So, I've add the protection code
if timer expires when MME does not receive Delete-Session-Response.
Most of the time, an application wants to perform some amount of data buffering
in addition to just responding to events. When we want to write data,
for example, the usual pattern runs something like:
1. Decide that we want to write some data to a connection;
put that data in a buffer.
2. Wait for the connection to become writable
3. Write as much of the data as we can
4. Remember how much we wrote, and if we still have more data to write,
wait for the connection to become writable again.
Now, Open5GS implements the above method by default when transmitting data
in a stream type socket.
In TS24.501 Ch 5.5.1.3.8 Abnormal cases on the network side
d) REGISTRATION REQUEST with 5GS registration type IE set to
"mobility registration updating" or "periodic registration updating"
received after the REGISTRATION ACCEPT message has been sent and
before the REGISTRATION COMPLETE message is received.
Since, we have to do this special case, it is desirable
to handle it directly inside the state(gmm-sm.c).