When MME assigns New GUTI to UE

Question

When MME decides to assign New GUTI to UE, based on this condition optional message(TAU Complete message) flows during TAU procedure

Answer 1

When a UE attaches to a network for the first time, it uses its IMSI to request access to the network and obtains a GUTI in Attach Accept message allocated by the MME. The UE thereafter uses the GUTI, instead of IMSI, when it attaches again to the network.

Comments

Thank you  Bhaskar Kalaria.. One more question,After completion of attach,in any case MME assign GUTI to UE..

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Hi Mohanraj,
After completion of attach, in any case MME assign GUTI to UE...??
Yes, during TAU process(in TAU Accept message) MME can also change/assign GUTI compared to previously obtained value during attach procedure. Though network remembers the new GUTI value it has allocated to the UE, and thus can recognize the UE even when it requests access using the modified/new GUTI

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Hi Bhaskar Kalaria,
Yes during TAU procedure MME may change/assign GUTI, but when and why MME decides to assign(new GUTI)/change GUTI is my question.