Internetwork Packet Exchange
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Internetwork Packet Exchange (IPX) is the network layer protocol in the IPX/SPX protocol suite. IPX is derived from Xerox Network Systems' IDP. It may act as a transport layer protocol as well.
The IPX/SPX protocol suite was very popular through the late 1980s into the mid-1990s because it was used by the Novell NetWare network operating system. Because of Novell Netware popularity the IPX became a prominent internetworking protocol.
A big advantage of IPX was a small memory footprint of the IPX driver, which was vital for MS-DOS and Microsoft Windows up to the version Windows 95 because of limited size of the conventional memory. Another IPX advantage is an easy configuration of the client computers. However, IPX does not scale well for large networks such as the Internet,[1] 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.[2] It is also possible to run later Novell products without IPX, with the beginning of full support for both IPX and TCP/IP by NetWare version 5Cite error: A <ref> tag is missing the closing </ref> (see the help page).
Frame formats
IPX can be transmitted over Ethernet using one of the following 4 frame formats or encapsulation types:
- 802.3 (raw) encapsulation comprises an IEEE 802.3 frame header (destination MAC, source MAC, length) immediately followed by IPX data. It is used in legacy systems, and can be distinguished by the first two bytes of the IPX header always containing a value of 0xFFFF, which cannot be interpreted as valid LLC Destination and Source Service Access Points in this location of the frame.
- 802.2 (LLC or Novell) comprises an IEEE 802.3 frame header (destination MAC, source MAC, length) followed by an LLC header (DSAP 0xE0, SSAP 0xE0, control 0x03) followed by IPX data. The 0xE0 fields of the LLC header indicate "NetWare".
- 802.2 (SNAP) comprises an IEEE 802.3 frame header, an LLC header (DSAP 0xAA, SSAP 0xAA, control 0x03), a SNAP header (OUI 0x000000, type 0x8137), and IPX data. The 0xAA fields of the LLC header indicate "SNAP", and the OUI 0x000000 in the SNAP header indicates an encapsulated EtherType.
- Ethernet II encapsulation comprises an Ethernet II frame header (destination MAC, source MAC, EtherType 0x8137) followed by IPX data.
In non-Ethernet networks only 802.2 and SNAP frame types are available.
References
- ^ Simson Garfinkel, Gene Spafford. Practical UNIX and Internet Security (2nd ed.). O'Reilly Media.
It does not scale well to large networks such as the Internet
- ^ "Do you still support IPX/SPX on your Windows servers?". TechRepublic. February 12, 2001. Archived from the original on 2012-07-10.