Is a packet transfer protocol used in wireless GPRS/HSDPA networks. When data has to be transmitted, it is broken down into similar structures of data before transmission, called packets, which are reassembled once they reach their destination. A packet is also called a datagram, a segment, a block, a cell or a frame, depending on the protocol used for the transmission of data. GPRS systems support both X.25 and IP network layer protocols. Therefore, PDP addresses can be X.25, IP, or both.