Introduction to Networking

Data communication (networking in the context of computer-computer) is important because computers that don't communicate with other computers aren't very useful or interesting. Networking provides the foundation upon which distributed systems are built. As Sun Microsystems likes to say, "The network is the computer."

The history of networking, like computers, is very short with amazingly rapid progress.

Computers have gotten faster, smaller, cheaper. But communication has improved more, and has more to go. A supercomputer has a clock cycle time of around 1ns today. 20 years ago it was around 100ns - 2 orders of magnitude improvement in 2 decades. The ARPANET of the 70s carried data at 56kbps. Today we have 622Mbps networks, a gain of 11,000 in 2 decades, or more than a factor of 100 per decade.

Clock cycle times on computers are approaching physical limits of heat dissipation and speed of light propogation time. The theoretical capacity of fiber in use today is 50,000 G bps.

History

1940 - Bell Labs performs data communication between 2 computers
1958 - first US communications satellite
1963 - MCI offers microwave link as AT&T alternative
1962 - Paul Baran, RAND: "On Distributed Communications Networks"
1968 - US court decision makes it legal to connect to phone network
1969 - ARPA sets up first four nodes of ARPAnet
1971 - ARPANET has 15 nodes (23 hosts): UCLA, SRI, UCSB, U of Utah, BBN, MIT, RAND, SDC,
1972 - Xerox develops Ethernet
1973 - First international connections to the ARPANET: England and Norway
1979 - USENET established using uucp between Duke and UNC by Tom Truscott and Steve Bellovin.
1982 - Berkeley releases 4.2BSD incorporating TCP/IP (:mpc:)
1984 - Domain Name Server (DNS) introduced.
1987 - number of hosts breaks 10,000
1989 - number of hosts breaks 100,000
1991 - WAIS and Gopher are created
1992 - number of hosts breaks 1,000,000; NSFNET backbone upgraded to T3 (44.736Mbps)
1993 - World Wide Web invented at CERN
1994 - Shopping malls arrive on the Internet
1995 - WWW records 20,000% growth for year

Hardware

The distance between communicating CPUs has a major impact on what is important in terms of data comm. There is a spectrum here with no discrete divisions. Same subjects, just different emphasis in which data comm aspects are most important.

interprocessor distance	system	classification
0.1m	circuit board	dataflow machine
1m	system box	multiprocessors, workstation/peripherals
10m	room	peripherals, LAN
100m	building	LAN
1000m	camus	LAN
10km	city	MAN
100km	country	WAN
1000km	contintent	WAN
10,000km	planet	Internet

Topology

properties to consider: number of hops apart, scalability, expense, vulnerability

logical versus physical topology: rings as starfish