Core network Nb interface user plane protocols
The present document specifies the user plane protocol of the bearer used between two MGWs within the BICC-based CS core network, called the Nb UP protocol. The present document assumes the implementation of the split between call control and the bearer transport and control, as specified in 3GPP TS 23.205 [1], see figure 1. Note that the present document does not preclude an implementation of a combined MSC Server and MGW.
Figure 1: CS core network logical architecture