Sequenced Packet Protocol (SPP) is a connection-oriented transport protocol for reliable, connection-oriented
and flow-controlled data packet transmissions to support client-server processes. The SPP protocol was developed by Xerox and is one of
the XNS protocols, Xerox NetworkSystem
(SPX) is one of the best known variants of the SPP protocol. The SPP protocol has flow control and supports applications with multiple transport connections. For connection control, SPP protocol uses destination address. Like other packet-oriented transport protocols, the SPP protocol uses sequence numbers to ensure the correct order of data packets at the receiving location. In addition, there are confirmation numbers to indicate the last data packet of a sequence and to ensure that the sequence was transmitted completely and without errors.