Section: 5.5.1.2.3 EMM common procedure initiation
Content: The network may initiate EMM common procedures, e.g. the identification, authentication and security mode control procedures during the attach procedure, depending on the information received in the ATTACH REQUEST message (e.g. IMSI, GUTI and KSI). If the network receives an ATTACH REQUEST message containing the Old GUTI type IE and the EPS mobile identity IE with type of identity indicating "GUTI", and the network does not follow the use of the most significant bit of the < group id> as specified in 3GPP TS 23.003[ Numbering, addressing and identification ]  [2], clause 2.8.2.2.2, the network shall use the Old GUTI type IE to determine whether the mobile identity included in the EPS mobile identity IE is a native GUTI or a mapped GUTI. During an attach for emergency bearer services or an attach for access to RLOS, the MME may choose to skip the authentication procedure even if no EPS security context is available and proceed directly to the execution of the security mode control procedure as specified in clause 5.4.3.