· The purpose of the PDN Disconnect procedure is for a UE to request the network to disconnect from one PDN.
· The UE can initiate this procedure to disconnect from any PDN as long as it is connected to at least one other PDN.
· Successful completion of this procedure means that, all EPS bearer contexts established towards this PDN, including the default EPS bearer context, are released.
· In order to disconnect from the last PDN (the one and the only PDN to which the UE has the connection), the UE should not use PDN disconnect procedure. Instead, it shall use detach procedure
· In order to request PDN disconnection from a PDN, the UE shall send a PDN DISCONNECT REQUEST message to the MME and start the timer T3492.
· In this message, The UE shall set the value of Linked EPS Bearer Identity IE as the EPS Bearer Identity of default bearer associated with the PDN for which UE is sending the disconnect request.
· If the network accepts the PDN DISCONNECT REQUEST sent by the UE, then it shall send the DEACTIVATE EPS BEARER CONTEXT REQUEST message including the linked EPS bearer identity of the default bearer associated with the PDN to disconnect from.
· If the network doesn’t accept the PDN DISCONNECT REQUEST sent by the UE, the MME shall send a PDN DISCONNECT REJECT message to the UE which shall contain the PTI and an ESM cause IE indicating the cause for the rejection
· Upon receipt of the DEACTIVATE EPS BEARER CONTEXT REQUEST or PDN DISCONNECT REJECT message, the UE shall stop the timer T3492
· If there is no response received for the PDN DISCONNECT REQUEST before the expiry of the timer T3492, the UE shall resend the PDN DISCONNECT REQUEST and shall reset and restart timer T3492. This retransmission is repeated four times, i.e. on the fifth expiry of timer T3492, the UE shall abort the procedure and deactivate all EPS bearer contexts for this PDN connection locally without peer-to-peer signalling between the UE and the MME
Reference 3GPP TS 24.301
Example: PDN DISCONNECT REQUEST message
How would we know that PDN disconnect request is only for specific PDN?
ReplyDeleteUsing Linked EPS bearer identity, this IE will contain default EPS bearer id.
ReplyDeleteUE is connected to two PDNs(primary for internet and secondary for IMS). UE has triggered PDN disconnect request when we initiated switch off procedure on UE, will it wait for the network to deactivate the default IMS PDN or it will continue the switch off procedure?
ReplyDeleteThe UE will not wait, it will continue to switch off after 5 seconds.
DeleteThe network and the UE shall deactivate the EPS bearer context(s) for this UE locally without peer-to-peer signalling between the UE and the MME
Hello Kumar
DeleteMy understanding was UE will "deactivate the EPS bearer context(s) for this UE locally without peer-to-peer signalling between the UE and the MME" only after 5 retransmissions of PDN Disconnect Request.
Please advise.
Thanks,
Alex.
In case of device reselection to another RAT(eg 3g), does UE detach locally? is there any timer associated to wait before doing this detach in reselection case? if suppose there is ping pong of 3g to 4g reselections, i guess timer would help not to do detach for each reselection.
ReplyDeleteHi,
DeleteThe UE doesn't detach during reselection procedure between different RATs. Checkout section 6.2.3 from 36.523 for Inter-RAT reselection procedures.
hiii.
DeleteI had an doubt, can u plz clarify
device is L+L support.
both sum subslot I had put jio sim
if I disable one sim in sim setting, should pdn disconnect request will trigger or only DETATCH will trigger?
After ending an emergency IMS call(eg. 911 in North America), Should the UE disconnect from SOS PDN? Or just deactivate the dedicated bearer for call?
ReplyDeleteHi,
ReplyDeleteIn the attached screenshot, we have "EPS bearer identity" and "Linked EPS bearer identity". Can you please help in explaining the difference between them?
Thanks,
Dev