s of the EPS architectures - the GTP variant we described above, and the PMIP variant. We talk about variants because the EPS architecture shown in Figure 2.10 is valid for the both variants. The difference in the PMIP variant is in the S5/S8-interface, which uses PMIP [37] instead of GTP. Figure 2.17 shows the control plane protocol architecture. When comparing the PMIP-based control plane architecture with the GTP-based control plane architecture in Figure 2.12, the difference is apparent. Instead of using GTP to create, manage, and delete the tunnels between the SGW and the PGW, the PMIP protocol is used. The PMIP protocol is a technology defined by the IETF, whereas GTP is a technology specified by 3GPP. As the control plane protocol architecture is different in the PMIP-based EPS architec- ture, the procedures used are a little different as well. An example can be seen in the LTE attachment procedure described in Figure 2.18. When comparing to Figure 2.14, which we studied earlier, we can see an extra step (marked as 4b and 5b). We do not want to repeat the whole signaling flow explanation at this point, but the reader can refer to the explanation connected to Figure 2.14 in Section 2.3.1. The added step is described below. Basics of the 3GPP Technologies 4b Proxy Binding Update is created with the information that SGW obtained from the Create Session Request from the MME. The SGW creates a new entry in its bearer table, and sends the message to the PGW. 5b Proxy Binding Acknowledgement is a response to the Proxy Binding Update indicating the failure or success of the default bearer creation. In case of success, the PGW creates itself a bearer table entry and sends the Proxy Binding Acknowledgement message to the SGW. As can be seen from Figure 2.18, at this level abstraction of the difference between the GTP and the PMIP EPS architecture variants is in the control plane and the names of the messages over the S5/S8-interface. Obviously, there is more than meets the eye. However, for the purpose of the scope 