IPX/SPX

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Internet protocol suite
5. Application layer

DHCPDNSFTPHTTPIMAP4IRCMIMEPOP3SIPSMTPSNMPSSHTELNETTLS/SSLRPCRTPSDPSOAP

4. Transport layer

TCPUDPRSVPDCCPSCTP

3. Network layer

IP (IPv4IPv6) • ARPBGPICMPIGMPIGPRARP

2. Data link layer

ATMBluetooth (PAN-Profile)EthernetFDDIFrame RelayGPRSModemsPPPWi-Fi

1. Physical layer

Bluetooth RFEthernet physical layerISDNModemsRS232SONET/SDHUSBWi-Fi

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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.

[edit] See also