While many of us work with networks regularly, we may not be familiar with network ins and outs. Computer networks are essentially communications networks that exist to enhance the quantity, quality and speed of communications from one point to another or others. A greater understanding of communications networks -- including a little comparative history -- will increase understanding of modern computer networks and networking basics.
In a previous Government Technology article ["A Crash Course In Networks," March 1998], a number of basic definitions of the word "network" were presented. These might be summarized as: "an interconnected system of lines or channels existing to facilitate the exchange of communications." The key point here is communication.
Early Communications Networks
A predecessor to modern telephony and computer networks, Samuel Morse's telegraph presents some interesting comparisons with modern-day communications networks. The original telegraph used Morse code -- a system (dare we say protocol?) that utilized a series of dots and dashes to represent letters and other characters in order to transmit information across an electric wire. In addition to Morse code, the telegraph system required a sending device, a receiving device and a connection between devices -- i.e., telegraph lines. At the receiving end, a telegraph message had to be decoded by a human operator proficient in Morse code, otherwise the communication would be meaningless to its intended recipient.
The telegraph was greatly improved by French engineer Emile Baudot, who devised a method called multiplexing, which transmits up to eight messages on a single telegraph line (Morse's original system only allowed for the transmission of one message at a time). Baudot also developed a keyboard device, later called a teletypewriter, that transmitted electric pulses down the wire. His keyboard-generated pulses used binary numbers -- a series of zeros and ones -- to represent or encode the letters and other characters that made up the message. Further, Baudot's machines, in addition to being the first keyboard-oriented networking devices, did the encoding and decoding, effectively eliminating the need for human operators to decode received messages.
In this early system, we see the rudiments of present-day networks: Character-based keyboards were used to encode communications into electric pulses transmitted electronically across a wire. A receiving device using the same system automatically processed these pulses. Machines based on Baudot's teletypewriter, with its keyboard-based, character-entry system using binary code, were adopted by computer engineers as a method of moving information into and out of such early systems as ENIAC and UNIVAC. Further developments allowed several teletypewriters (or terminals) to be connected to one computer in order to enable multiple users of one machine.
"Mr. Watson, Come Here. I Want You."
Of course, the next major communications advance following the telegraph was the telephone. In what was no doubt the first communications network "install," telephone developers Alexander Graham Bell and Thomas Watson in 1876 strung telegraph cable around their Boston neighborhood and held a conversation over a two-mile distance.
The original telephone systems required that each telephone in the system be connected to a central switchboard. A human operator was needed to connect callers to recipients by physically inserting a plug into the switchboard. There were no phone numbers; human operators simply knew everyone who had a phone and which plug in their board represented which phones in the network.
One interesting development occurred following the expiration of Bell's patents in 1893 and 1894. New telephone companies sprung up all over the country eager to cash in on the new technology. Deployments were generally localized with little or no attention paid to standards. Neighboring communities, with telephone infrastructures installed by different vendors, found they could not connect their phone services to each other due to incompatibilities with their equipment. Any of this sounding familiar?
This particular problem was solved by intervention from the federal government. American Telephone and Telegraph was established as a regulated monopoly. The government demanded phone service be made universally available, including to rural areas, and encouraged interconnection between local systems. This essentially forced a standard on the telephone industry. Today's debate regarding Internet infrastructure and access becomes more intriguing when viewed in this historical context.
From this, we can see that telephone network architecture is quite similar to that of computer networks. A great bonus is that both systems are able to use the same infrastructure for interconnection: the existing system of telephone lines and switches. This, along with the invention of the modem, is a major reason behind the phenomenal acceptance and continued growth of the Internet. In fact, one could argue that the Internet -- with its heavy reliance on the existing system of telephone lines -- is the logical convergence between telephony and computer networks.
In the early days of computer networks, communication between physically separated machines was only possible via expensive, dedicated lines. Engineers at Bell Laboratories came up with a milestone breakthrough in the 1960s -- the modem.
Short for MOdulator-DEModulator, this device converts a computer's digital data into analog tones. The sending computer outputs digital information to the modem, the modem encodes it into analog pulses and forwards it to a receiving computer also equipped with a modem. The receiving computer's modem decodes the analog information, converting it back into digital data and passing it to the computer. Thus, computers equipped with modems can communicate over standard telephone lines.
This simple invention revolutionized communication networks and computer networking. Since the network of telephone lines could now be used to connect computers, any need to create a new infrastructure of digital lines was eliminated. The modems were relatively inexpensive and, at this point, have become commodities.
The stage was set for the rapid expansion of networks consisting of geographically diverse computers and computer networks. Everyone could now get in on the act, and they did. The 1970s and 1980s saw the birth and growth of wide and local area networks. Further developments allowed telephone-compatible lines with greater data-carrying capacity to be connected directly to local area networks. This expanded the reach and scope of computer networks.
Each network examined here fulfills the basic requirement understood by Morse, Baudot and Bell: moving a communication from point A to point B. Innovations and developments have been aimed at making this faster, easier and more accessible to a greater numbers of users. Despite differing technologies, the basic elements have remained the same: An originating communication is encoded with a sending device, which transmits the message through a connecting medium. The message is decoded with a receiving device, which delivers the original communication.
It seems unlikely that these basic principles will ever change. Modern networks exist for the same reason the telegraph was invented -- to get a message to its intended recipient faster. We are currently witnessing a great rush to increase the speed of network communications through bandwidth innovations, including such technologies as cable modem and Asynchronous Transfer Mode.
Lastly, we are witnessing the emergence of the Internet. While it shares many similarities with the birth of the telephone, its instrument of implementation -- currently the personal computer -- is quite a bit more expensive to manufacture than was the telephone handset. Further, the Internet requires a much more complex network installation and infrastructure. Some day, when the problems of connectivity, instrument and infrastructure are solved, we may see the Internet replace the telephone as the communications network of choice.
Until then, call first before sending an e-mail!
John Stanard is a senior consultant with webworld studios -- a Northern Virginia-based Web consulting and applications development company.
June Table of Contents
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