UMTS protocols are divided into two different strata (See Fig):
1. NAS (non access stratum)
2. AS (access stratum)
UE (User Equipment) and CN (Core Network, MSC for circuit switched service, SGSN for packet switched service) need to talk!
NAS protocols support the talk between UE and CN.
It does not care below access method (could be UTRAN, GSM/GPRS).
Some examples of NAS protocols:
control plane
1. Connection management (CM), Session management (SM) – taking care of establishment and release of connection and session
2. Mobility management (MM) and GPRS mobility management (GMM) – responsible for mobility
data plane
1. IP
2. CS service
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AS is a group of protocols that are specific to access network:
1. Uu (radio interface between UE and Node B)
2. Iub (between Node B and RNC)
3. Iu (between RNC and CN)
