Computer Networks

Spokes of the wheel network - Client and server
Internet - a world-wide network of networks, but no central control

How the Internet Began -

The Internet had its origins in the ARPANET, which was a network connecting large mainframe computers at a small number of universities and research laboratories, beginning around 1969.  The description in Perry & Schneider in my view overstates the military nature of this network, and leave out several points:

Perry & Schneider p. 1.7 - DoD became very concerned about the possible effects of nuclear attack on its computing facilities.  DoD realized that the weapons of the future would require powerful computers for coordination and control.   The powerful computers were all large mainframe computers so DoD began to explore ways to connect these computers to each other and also to weapons installations that were distributed all over the world.   DARPA researchers soon became concerned about computer networks' vulnerability to attack and worked hard to eliminate the need for network communications to rely on a central control function.

1.8 - The original purpose of the ARPANET was to connect computers in the field that were controlling a wide range of diverse weapon systems, so the ARPANET could not force its protocol or structure onto those individual component networks.

1.9 - Although the goals of the ARPANET were still to control weapon systems and transfer files ...

This description leaves out several points:

• ARPA was probably the major agency funding computer science research at universities and at labs associated with universities (Stanford Research Institute, MIT Lincoln Labs).  (Later the National Science Foundation probably became the primary funding source.)   As the primary government funding source for these computers, ARPA had an interest in having these computers be connected in a network quite apart from any application of networks to weapon systems, command and control, etc.  Benefits would include:

  -colloboration among geographically-dispersed researchers
  -more effective utilization of scarce computer resources -- researcher could utilize a computer located in another part of the country
  

• ARPA was funding relatively basic research.   Although ARPA probably would cite the military benefits of this work, I do not believe that military requirements were foremost in the minds of those at universities and research labs who were doing the work.

Growth of the Internet During the 1990s

• Commercialization - NSF prohibited commercial traffic, so businesses had turned to commercial email services.  In 1989, NSF permitted 2 commercial e-mail services, MCI Mail and Compuserve to establish connections to Internet to exchange email messages with the members of the academic and research communities
• World wide web - hypertext and graphical user interfaces come to the Internet
• Faster modems, color monitors

 Definition of Web Site

p. 15 - The number of web sites, which are computers connected to the internet that store HTML documents ,,, Each web site might have hundreds, or even thousands, of individual Web pages ...

I find this terminology confusing.  I think of a web site as a collection of web pages that are logically related to each other and this is in fact the definition they use on p. 3.5.  Thus I have done a web site for the two courses I am teaching.  My web site is hosted by Erols, which means my HTML documents reside on their server, which can be accessed by clients through the internet.  What they are calling  web sites in chapter 1 I would call servers.

Figure 1.10 - Bandwidths for Various Types of Internet Connections

 DSL, cable modems, and satellite missing from table

Choice of ISP's

(1) Some ISPs (e.g. AOL, MSN, Prodigy, Compuserve) are national where others are regional (Erols) or local.  The standard pricing now for national ISPs (AOL, MSN, Prodigy, Compuserve) is a flat rate of about $20-22/month for unlimited use whereas local and regional ISPs are around $15.  If you want to access your ISP from other sections of the country when you travel, check with your regional and local ISPs about use of 800 numbers and dial-in through ISPs in other parts of the country.

(2) Some plans (e.g., AOL and Mindspring) in addition offer plans that offer a certain number of hours for a smaller dollar fee and then an hourly charge when you go over that.

(3) AOL offers content only available to AOL members plus Internet access whereas most every body else just offers internet access.

4) E-mail programs - With AOL you must use their proprietary email program, with other ISPs, you can use a variety of email programs (see Chapter 2).

Connecting VIA Satellite

1.22 - Satellite connection is downlink only, so you must have another connection through ISP that uses telephone lines to handle the uplink half of the connection -- I would think that wireless telephony would be another option here.