Sequenced Packet Exchange
(SPX) A transport layer protocol built on top of IPX. SPX is used in Novell NetWare systems for communications in client/server application programs, e.g. BTRIEVE (ISAM manager).
SPX is not used for connections to the file server itself; this uses NCP. It has been extended as SPX-II. SPX/IPX perform equivalent functions to TCP/IP.