In a point-to-point topology, each router needs a single security zone and single Tx-SC for encryption and a single Rx-SC for decryption. Each SC has two SAs. In total for point-to-point topology, four SAs are needed, two RxSA for RxSC1 and two TXSA for TxSC1. See Figure 1.
Figure 1. Switch point to switch point topology
