The Second Internet HTML version

Chapter 2 – History of Computer Networks Up to TCP/IPv4
A long time ago (in a Galaxy not too far away), people started connecting computers together. A few
brave souls tried to do this with dial-up 1200 baud modems over phone lines. Pioneers brought up
Bulletin Board Systems (message boards that one person at a time could dial into and exchange short
messages, and later small files, with each other). I brought up the 8th BBS in the world, in Atlanta, about
1977, using code from the original CBBS in Chicago (created by Ward Christensen and Randy Suess) and
a modem donated by my friend Dennis Hayes (of Hayes Microcomputer Products). Later there were
thousands of online Bulletin Board Systems, all over the world. Soon there followed commercial
“information utilities” like CompuServe and The Source, which were like giant BBS’es with many more
features. Tens of thousands of users could connect to these simultaneously. It was like the first crude
approximation to the Internet of today, based on circuit switched connections over telephone lines.
Everything was text oriented (non-graphical) and very slow. 1200 bits/sec was typical at first, although
later modems with speeds of 2400 bits/sec, 9600 bits/sec, 14.4KB/sec, 28.8KB/sec and finally 56KB/sec
were developed and came into widespread use. Later these modems were primarily used to dial into an
ISP to connect to the Internet, and some people are still using them this way.
2.1 – Real Computer Networking
While home computer users were playing around with modems and bulletin board systems, the big
computer companies were working on ways to connect “real” computers at higher speeds, and with
much more complex software.
2.1.1 – Ethernet and Token Ring
Much of this was based on Ethernet, which was created by a team at Xerox PARC led by Robert Metcalf
between 1973 and 1975. The first specification (1976) ran at 3 Mbit/sec. Metcalf left PARC in 1979 to
create 3com and create commercial products based on Ethernet. Working together with DEC, Intel and
Xerox (hence the “DIX” standard), 3com released the first commercial products running at 10 MBit/sec.
Ethernet was standardized in 1980 by the IEEE (Institute for Electrical and Electronic Engineers) as 802.3.
Early versions ran on 10base2 (a small diameter coax cable) or 10base5 (a larger diameter coax cable).
These used a “multidrop” architecture, which was subject to many reliability problems. With the
introduction of the simpler to deploy and manage “unshielded twisted pair” (actually 4 pair, or 8 wire)
cables (known as 10baseT, mid 1980s), and star architectures using “hubs” and later “switches”, local
area networks really took off. Today, virtually all Ethernet networks use twisted pair copper wire (up to
gigabit speed) or fiber optic cable (for higher speed and longer runs). I helped deploy a 10base2 coax
Ethernet network in Hong Kong in 1993. Trust me, twisted pair cabling is a lot easier.
IBM for many years pushed a competing physical layer network standard called “Token Ring” (later
standardized as IEEE 802.5). Token Ring was available in 4 Mbit/sec and 16 Mbit/sec versions. Later, a
100 Mbit/sec version was created, but by then Ethernet dominated the market and Token Ring quietly
disappeared. FDDI (Fiber Distributed Data Interface) still in use today is based on the token ring concept.