Version 2 P2P Encrypted Transport Protocol.

Lets nodes encrypt the traffic between them, making it harder for eavesdroppers to tell where a payment came from.

Nodes used to talk in plain, readable data. Someone watching every connection could link a payment to the node that first sent it, tamper with messages, or spot and block Bitcoin traffic. Version 2 encrypts the connection when both nodes support it and makes the data look random. It also saves a little bandwidth.