Evolution Of Communication Networks
- 3. Samuel Morse Message Sending key
- 4. S J C E ... .--- -.-. .
- 5. Samuel F. B. Morse It worked by transmitting electrical signals over a wire laid between stations 1837 Washington, D.C., to Baltimore, the message said: "What hath God wrought?" The telegraph revolutionized long-distance communication.
- 6. Alexander Graham Bell, who patented the telephone in 1876. "Subject File: The Telephone-- Drawing of the Telephone, Bell's Original." Alexander Graham Bell Family Papers, Manuscript Division, Library of Congress.
- 7. Alexander Graham Bell Microphone converts voice pressure variation (sound) into analogous electrical signal Loudspeaker converts electrical signal back into sound 1876 "Mr. Watson – Come here – I want to see you," Bell said when first using the new invention, (In Boston, U.S) The drawback of the telegraph, however, was that it still required hand-delivery of messages between telegraph stations and recipients, and only one message could be transmitted at a time.
- 10. Technology is the not only factor in success of a new service Three factors considered in new telecom services TechnologyMarket Regulation Can it be implemented cost- effectively? Can there be demand for the service? Is the service allowed? New Service
- 11. Capabilities of various technologies have improved with reduced cost. Fundamental limitations (Ex: Speed of light) The capabilities of a given technology can be traced over a period of time and found to form a S-shaped curve. An example of this situation is the capability of copper wires to carry information measured in bits per second.
- 13. As the capabilities of a given technology approach saturation, innovations that provide the same capabilities but within a new technology class arise. For example, as copper wire transmission approached its fundamental limitation, the class of coaxial cable transmission emerged, which in turn was replaced by the class of optical fiber transmission. The optical fiber class has much higher fundamental limits in terms of achievable transmission rates and its S curve is now only in the early phase.
- 14. Initial class of invention: Copper wires Second type of invention : Coaxial cable Third type of invention : Optical fiber When the S curves for different classes of technologies are superimposed, they form a smooth S curve themselves, as shown:
- 15. Early telegraphy systems operated at a speed equivalent to tens of bits per second. Early digital telephone systems handled 24 voice channels per wire, equivalent to about 1,500,000 bits per second. In 1997 optical transmissions systems could handle about 500,000 simultaneous voice channels, equivalent to about 10^10 bits per second (10 gigabits per second)! In the year 2000 systems could operate at rates of 10^12 bits per second (1 terabit per second) and higher! These dramatic improvements in transmission capability have driven the evolution of networks from telegraphy messaging to voice telephony and currently to image and video communications.
- 16. 1.0E+03 1.0E+04 1.0E+05 1.0E+06 1.0E+07 1.0E+08 0 10 20 301972 1982 1992 2002 4004 8080 8086 8028 6 486 DX Pentium Pentium Pro Pentium III P4 Transistorcount Intel DX2 Pentium II States that the number of transistors on a chip doubles about every two years.
- 17. A number of other key technologies have participated in the development of communication networks. Processing technology: ◦ RAM: ◦ Digital signal processing: transmission, multiplexing, framing, error control, encryption ◦ Network processors: hardware for routing, switching, forwarding, and traffic management Software Technology • Greater functionality & more complex systems • Middleware to connect multiple applications • Adaptive distributed systems
- 18. Traditional communication services in the form of telephony and telegraphy have been government regulated. (Because of high cost in deploying the requisite infrastructure and the importance of controlling communications). Telephone service is now considered an essential "lifeline" service in many countries, and regulation plays a role in ensuring that access to a minimal level of service is available to everybody. In India : The telecommunications market is heavily regulated with the government retaining the exclusive right to provide telecom services and allowing third parties to provide services only after receiving a licence from it.
- 19. Data encryption translates data into another form, or code, so that only people with access to a secret key (formally called a decryption key) or password can read it. Encrypted data is commonly referred to as ciphertext, while unencrypted data is called plaintext. Currently, encryption is one of the most popular and effective data security methods used by organizations. The purpose of data encryption is to protect digital data confidentiality as it is stored on computer systems and transmitted using the internet or other computer networks.
- 20. There is less agreement on the degree to which information should be kept private when transmitted over a network. Should encryption be so secure that no one, not even the government in matters of national security, can decipher transmitted information? These questions are not easily answered. The point here is that regulation on these matters will provide a framework that determines what types of services and networks can be implemented.
- 21. The network effect: Usefulness of a service increases with size of community. ◦ Metcalfe's law states that the value of a telecommunications network(Usefulness) is proportional to the square of the number of connected users of the system (n2) ◦ Ex: Phone, fax, email, ICQ, … Economies of scale: The cost of a service generally decreases with the size of the subscriber base due to economies of scale, for example, the cost of terminal devices and their components.(per-user cost drops with increased volume) ◦ Cell phones, PDAs, PCs The challenge then is how to manage the deployment of a service to first address a critical mass and then to grow to large scale.
- 22. Ex 1:In the early 1970s a great amount of investment was made in the United States in developing the Picturephone service, which would provide audio-visual communications. The market for such a service did not materialize. Subsequent attempts have also failed, and only recently are we starting to see the availability of such a service piggybacking on the wide availability of personal computers.
- 23. Ex 2: We consider the deployment of cellular radio telephony.(Cellphone)The service, first introduced in the late 1970s, was initially deployed as a high-end service that would appeal to a relatively narrow segment of people who had to communicate while on the move. This deployment successfully established the initial market. The utility of being able to communicate while on the move had such broad appeal that the service mushroomed over a very short period of time.
- 24. Standards are basically agreements, with industrywide, national, and possibly international scope, that allow equipment manufactured by different vendors to be interoperable. The primary reason for standards is to ensure that hardware and software produced by different vendors can work together. Without networking standards, it would be difficult—if not impossible—to develop networks that easily share information. Standards also mean that customers are not locked into one vendor. They can buy hardware and software from any vendor whose equipment meets the standard. In this way, standards help to promote more competition and hold down prices.
- 25. There are two types of standards: formal and de facto. A formal standard(Official standard) is developed by an official industry or government body. Web browsers (e.g., HTTP, HTML), for network layer software (e.g., IP), data link layer software (e.g., Ethernet IEEE 802.3), and physical hardware (e.g., V.90 modems). De facto standards(public standard) arise when a certain product, or class of products, becomes dominant in a market. For example, personal computers based on Intel microprocessors and the Microsoft Windows operating system are a standard in this sense.
- 26. 1) The specification stage consists of developing a nomenclature and identifying the problems to be addressed. 2) In the identification of choices stage, those working on the standard identify the various solutions and choose the optimum solution from among the alternatives. 3) Acceptance, which is the most difficult stage, consists of defining the solution and getting recognized industry leaders to agree on a single, uniform solution.
- 27. Three factors considered in new telecom services TechnologyMarket Regulation Can it be implemented cost effectively? Can there be demand for the service? Is the service allowed? New Service