Network addresses are chosen such that they are unique on the internetwork in question.
IDP has no notion of subnetworks any new collection of hosts requires another network address to be assigned. Routers were devices that switched datagrams between two or more separate IDP networks. The addressing scheme used a combination of a 4-byte IDP network address (which was uniquely assigned to each Ethernet LAN segment), and the 6-byte node address (the address of the NIC card). The datagrams of an XNS network were individually addressed. There were two primary networking protocols involved: the Internet Datagram Protocol (IDP), which provided a connectionless and unreliable transport of datagrams from one host to another, and the Sequenced Packet Protocol (SPP), which was a modified form of IDP that was connection-based and reliable.
The Xerox Network Specification described a series of protocols designed for general purpose internetworking, with a strong emphasis on the use of local area networks. In the late 1970s, the Xerox Corporation developed and published an open standard called the Xerox Network Specification (XNS). Xerox, Novell, and Historyįirst, let's look at where the protocols came from and what they look like.
We'll provide a brief description of the protocols themselves in this chapter, but we focus on how to configure and use free software to allow Linux to interoperate with Novell products. Linux has both free and commercial software offerings to provide support for integration with the Novell products. These protocols are distant cousins of TCP/IP, and while they perform similar sorts of functions, they differ in a number of ways and are unfortunately incompatible. Linux supports not only the TCP/IP protocols, but also the suite of protocols used by the Novell Corporation's NetWare operating system. Novell and NetWare are trademarks of the Novell Corporation. Many of these corporate users still have legacy networks using these protocols and want to integrate this support with their new TCP/IP support. Long before Microsoft learned about networking, and even before the Internet was known outside academic circles, corporate environments shared files and printers using file and print servers based on the Novell NetWare operating system and associated protocols. Linux Network Administrator's Guide, 2nd Edition Linux Network Administrator's Guide, 2nd Edition: Chapter 15: IPX and the NCP Filesystem