Hello everyone！
Today, I want to give you a brief introduction to the attach procedure.
What is an attach procedure?
After the UE is powered on, the UE registers with a network. The process in which the UE registers with the network is called attach. During the attach process, the information about the UE is registered with the network entity. During the attach procedure, a default bearer is set up between the UE and the P-GW to ensure that the UE is always online and assigns an IP address to the UE. After the attach, the UE status changes from EMM-deregistered to EMM-registered, and from ECM-idle to ECM-connected.
During the attach procedure of the UE, one or more dedicated bearer establishment procedures may be triggered to help set up a bearer from the UE to the EPS. During the attach procedure, the UE requests an IP address. During the attach initialization process, the MME obtains a mobile equipment identity (ME ID) from the UE, and the MME checks the validity of the MEID through the EIR.
Functions of the attach procedure
1. The UE registers with the EPS network.
2. During network attach, a default EPS bearer is set up. The bearer provides a permanent IP connection.
3. The MM context and EPS bearer context of the UE are created on the MME and UE. The EPS bearer context of the subscriber is created on the S-GW and P-GW.
Figure 1 Attach procedure
The attach procedure is a phase of mobile phone network access, and I will share the EPS bearer in my next post.
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