The Transport Layer (Layer 4) protocol in Novell NetWare for exchanging packets between LANs. Internetwork Packet Exchange (IPX) is the associated Network Layer (Layer 3) protocol in the IPX/SPX protocol suite. SPX is similar to the Transmission Control Protocol (TCP), but is not industry standard and has been overwhelmed by the TCP/IP protocol suite. See also IPX/SPX, LAN, Network Layer, protocol, protocol suite, TCP, and Transport Layer.