IPX/SPX
From Wikipedia, the free encyclopedia
IPX/SPX stands for Internetwork Packet Exchange/Sequenced Packet Exchange. It is a networking protocol used by the Novell NetWare operating systems. Like UDP, IPX is a datagram protocol used for connectionless communications. IPX and SPX are derived from Xerox Network Services' IDP and SPP protocols.
SPX is a transport layer protocol (layer 4 of the OSI Model) used in Novell Netware networks. The SPX layer sits on top of the IPX layer (layer 3 - the network layer) and provides connection-oriented services between two nodes on the network. SPX is used primarily by client/server applications.
IPX and SPX both provide connection services similar to TCP/IP, with the IPX protocol having similarities to IP, and SPX having similarities to TCP. IPX/SPX was primarily designed for local area networks (LANs), and is a very efficient protocol for this purpose (typically its performance exceeds that of TCP/IP on a LAN). TCP/IP has, however, become the de facto protocol. This is in part due to its superior performance over wide area networks and the Internet (which uses TCP/IP exclusively), and also because TCP/IP is a more mature protocol, designed specifically with this purpose in mind.
Novell is largely responsible for the use of IPX as a popular computer networking protocol due to their dominance in the network operating system software market (with Novell Netware) from the late 1980s through to the mid-1990s.
IPX usage has declined in recent years as the rise of the Internet has made TCP/IP ubiquitous. Novell Netware has also adapted and now comes with built in TCP/IP support.
One area where IPX remains useful is to sidestep VPNs that force all TCP/IP traffic to traverse the VPN, preventing any access to local resources such as printers and shared disks.