Self Prepared material when i didn't find one. It covers basics of communication network evolution and also covers the Key factors in communication network evolution.

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.

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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