The Second Internet HTML version

2.1.2 – Network Software
Network software quickly evolved once Ethernet and Token Ring hardware became available. One of the
main goals was to “hide” the differences between various hardware level technologies (Ethernet, Token
Ring, Wireless, etc) from the higher level software. This led to the multiple layers of the network stack.
The bottom layer is very hardware specific, and the upper layers introduce more and more hardware
independence, so that applications can be written once, and run over any hardware transport.
Digital Equipment was one of the first to create networking software with DECNET (1975). IBM had
System Network Architecture (SNA, 1974). Xerox created the PARC Universal Packet protocol (PUP, late
70’s) which eventually evolved into Xerox Network Services (XNS, early 80’s) at PARC (Palo Alto Research
Center). XNS was the basis for the later Banyan Vines Network OS, based on “Vines IP” (similar to but
incompatible with IPv4 from TCP/IP). Banyan Vines included the first network directory service, called
“StreetTalk”. XNS also was the basis for Novell Netware (IPX/SPX, 1983), which eventually added its own
Netware Directory Services (NDS, 1993). NetWare did not fully support TCP/IP until 1998, which allowed
Microsoft (who supported TCP/IP first) to take over leadership in personal computing networks.
Microsoft worked with 3com to create their own network OS, called LAN Manager. It used SMB (Server
Message Block) protocol on top of either NBF (NetBIOS Frames Protocol) or modified XNS. In 1990,
Microsoft added support for TCP/IP as an alternate protocol (LAN Manager 2.0). With the release of
Windows NT Advanced Server in 1993, Microsoft finally phased out LAN Manager. By Windows NT v3.51
(May 1995) Microsoft encouraged users to deploy only TCP/IP (four years ahead of Novell’s support for
TCP/IP). This lead time allowed Microsoft to take over leadership in personal computer networks from
Novell. Microsoft introduced their version of network directory services in Windows Server 2000, now
known as Active Directory. The SMB protocol still survives as Microsoft’s “File and Printer Sharing”
protocol (now layered on TCP/IP, instead of NetBIOS or XNS). An Open Source implementation of this is
available as SAMBA.
2.2 – The Beginnings of the Internet (ARPANET)
While all this commercial activity was going on, the U.S. Military (at their Advanced Research Projects
Agency, or ARPA), with the help of Bolt, Beranek and Newman (BBN) and Mitre, were designing a new,
decentralized communication system based on packet switching. Existing communication systems
(telephone, radio, etc) were centralized, and hence subject to being completely disabled due to the
failure or loss of a few central nodes. Packet switched networks were highly decentralized, and had a
fascinating new property, which is that you could lose large parts of a network, and the remaining parts
would still work (assuming at least some links connected the working parts).
The first network protocol developed as part of ARPANET was called the 1822 protocol (named after
BBN report 1822), and was implemented by a Network Control Program, so the protocol was often
referred to as NCP. The first e-mail was sent over NCP in 1971, and the File Transfer Protocol followed
in 1973. On Jan 1, 1983 (“flag day”), NCP was turned off officially, leaving only TCP/IPv4 on the Internet.
You might think of the NCP era as phase 1 of the First Internet, with the IPv4 era being phase 2 of the
First Internet. Otherwise the new Internet based on TCP/IPv6 will be THIRD Internet. Fortunately, there
is no need for a flag day to go from TCP/IPv4 to TCP/IPv6, as they can co-exist (and probably will for
perhaps 5 to 10 years).