TS24.501
8.2.11 DL NAS transport
8.2.11.4 5GMM cause
The AMF shall include this IE when the Payload container IE
contains an uplink payload which was not forwarded and
the Payload container type IE is not set to "Multiple payloads".
-0-
As such, this function 'nas_5gs_send_gsm_reject()' must be used
only when an N1 SM message has been forwarded to the SMF.
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.
All process will be forcely exited if it failed to encode the S1AP/NGAP/GTP/PFCP message. It is to make sure there was no problem with the encoding of open5gs.
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
1. If UE does not use a NAS container for Non-cleartext IEs,
Open5GS AMF will send Registration reject message.
2. If UE sends Non-cleartext IEs without Integrity-protected,
Open5GS AMF will send Registration reject message.
3. If UE does not send NAS container in Security mode complete message,
Open5GS AMF will send Registration reject message.
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.
1. UE sends PDU session establishment request to the AMF.
2. AMF initiates Release Due to Duplicate Session ID.
3. SMF cannot find the session by SM-Context-Ref.
For the above condition, AMF sends NGAP ErrorIndication to the UE.
If parameter.ignore_requsted_nssai is true,
AMF will ignore the UE Requested NSSAI and create an allowed-NSSAI
based on the Default S-NSSAI in the Subscription DB.
AMF checks whether it can serve all the S-NSSAI(s) from
the Requested NSSAI present in the Subscribed S-NSSAIs
(potentially using configuration for mapping S-NSSAI values
between HPLMN and Serving PLMN), or all the S-NSSAI(s) marked
as default in the Subscribed S-NSSAIs in the case that
no Requested NSSAI was provided or none of the S-NSSAIs
in the Requested NSSAI are permitted,
i.e. do not match any of the Subscribed S-NSSAIs or not available
at the current UE's Tracking Area (see clause 5.15.3).
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.
Previously, AMF would sends PDUSessionResourceSetupRequest
when the following conditions were met:
- gNB didn't send UE Context Request IE of InitialUEMessage
- AMF should send SMF generated TRANSFER message(PDU_RES_SETUP_REQ)
to the gNB
However, in issues #771, the gNB did not accept
PDUSessionResourceSetupRequest. Perhaps the gNB engineer thought
that if gNB needs to send data traffic to the UE, AMF should send
an InitialContextSetupRequest regardless of UE Context Request IE.
This is because gNB requires the kgNB security context
for data connection.
So, in this case, Open5GS-AMF decided to send
an InitialContexSetupRequest regardless of
whether it received UE Context Request IE of InitialUEMessage.
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).
o Tester
1. UE registered to 5GS and can connect to internet.
2. Turn off the UE and turn on the UE immediately
3. UE send PDU session request message
without sending registration complete
o Analysis Result
1. UE sends registration request with unknown GUTI
2. AMF send registration accept without GUTI
3. UE skips the registration complete
So, we need the handler UL NAS Transport in this state.
- Set the number of UEs in units of AMF/MME instead of gNB/eNB.
- See default value as shown below
Number of UEs per AMF/MME : 4,096
Number of gNB/eNB per AMF/MME : 32