The figures below diagram the key protocol stacks on Uu, S1, and X2 interfaces for both C-plane and U-plane messaging.
Figure 1 : C-plane Protocol Stack: Uu (UE/eNB) and S1-C (eNB/MME)
Figure 2 : C-plane Protocol Stack: X2-C (eNB/eNB)
Figure 3 : U-plane Protocol Stack: Uu (UE/eNB) and S1-U (eNB/S-GW)
Figure 4 : U-plane Protocol Stack: X2-U (eNB/eNB)
