From Wikipedia, the free encyclopedia - View original article
The IPX/SPXM protocol stack is supported by Novell's NetWare network operating system. Because of Netware's popularity through the late 1980s into the mid-1990s, IPX became a popular internetworking protocol. Novell derived IPX from Xerox Network Systems' IDP.
A big advantage of IPX is an easy configuration of the client computers. However, IPX did not scale enough for large networks such as the internet and as such, IPX usage decreased as the boom of the Internet made TCP/IP nearly universal. Computers and networks can run multiple network protocols, so almost all IPX sites will be running TCP/IP as well to allow for Internet connectivity. It has also been possible to run Novell products without IPX for some time, as they have supported both IPX and TCP/IP since NetWare reached version 5 in late 1998.
A big advantage of IPX protocol is its little or no need for configuration. In the time, when protocols for dynamic assigning IP addresses did not exist and the bootp protocol for centralized assigning addresses was not common, the IPX network could be configured almost automatically. A client computer uses the MAC address of its network card as the node address, and learns the network number from the server or router. Network number is derived from MAC address of the server.
The administrator had to care only
Each IPX packet begins with a header with the following structure:
|2||Checksum (always 0xFFFF - no checksum)|
|2||Packet Length (including the IPX header)|
|1||Transport Control (hop count)|
The Packet Type values:
|1||RIP (Routing Information Protocol) (RFC 1582, RFC 2091)|
|4||PEP (Packet Exchange Protocol), used for SAP (Service Advertising Protocol)|
|5||SPX (Sequenced Packet Exchange)|
|17||NCP (NetWare Core Protocol)|
An IPX address has the following structure:
|0x0001-0x0BB8||Registered by Xerox|
|0x0001||Routing Information Packet|
|0x0002||Echo Protocol Packet|
|0x0003||Error Handling Packet|
|0x0451||Netware Core Protocol (NCP - used by Novell Netware servers)|
|0x0452||Service Advertising Protocol (SAP)|
|0x0453||Routing Information Protocol (RIP)|
|0x0457||Serialization Packet (used for NCP as well)|
|0x4000-0x4FFF||Dynamicly Assigned Socket Numbers|
|0x4003||used by Novell Netware Client|
|0x8000-0xFFFF||Staticly Assigned Socket Numbers|
|0x9091||TCP over IPXF|
|0x9092||UDP over IPXF|
|0x9093||IPXF, IPX Fragmentation Protocol|
The IPX network address is conceptually identical to the network part of the IP address (the parts with netmask bits set to 1); the node address then has the same meaning as the bits of IP address with netmask bits set to 0. As the node address is usually identical to the MAC address of the network adapter, the Address Resolution Protocol is not needed.
For routing, the entries in the IPX routing table are similar to IP routing tables; routing is done by network address, and for each network address a network:node of the next router is specified in a similar fashion an IP address/netmask is specified in IP routing tables.
IPX can be transmitted over Ethernet using one of the following 4 encapsulation types: