Wednesday, May 3, 2017

Networking Explained - Second Edition - 2001

You say we measure data rate in bits per second. Isn't this the same as baud rate?

No. There is a difference. A baud is a unit of signaling speed, named after the French
engineer Jean Maurice Emile Baudot (1845-1903). It is another term used to express the
capacity of a channel, but it is, indeed, different from bits per second. The speed in baud is
equal to the number of times the line condition (i.e., frequency, amplitude, voltage, or
phase) changes each second. At low speeds (under 300 bps) data rate (measured in bps)
and baud rate are the same because signaling methods are relatively simple. As speed
increases, signaling methods become more complex. Baud rate then differs from data rate
because several bits are typically encoded per baud. That is, each signal can represent
more than one bit of information

63. What do you mean by this?
Consider the changes in modem technology. Within a 36-month period in the 1990s,
data transmission rates for modems increased from 9600 bits per second (bps) to 14,400
bps to 28,800 bps to 33,600 bps to 56,000 bps. The standards on which each new modem
technology was based were originally proprietary. Although users (in most cases) were
given vendor assurances that their modems would be compliant with the forthcoming de
jure standard, users still faced a purchasing dilemma: Should I invest in the newer technology now, even though it is proprietary, or should I wait for the technology to be approved
by a formal standards organization before I commit my resources?
64. That's a good question. What's the answer?
Unfortunately, there is no easy answer to this question. You should be cognizant of the
relatively short life cycle of technology and understand that technology will always experience different stages of maturity as it evolves. This situation, coupled with the lengthy
process of formal standardization, means we cannot rely solely on de jure standards to
achieve interoperability. The realistic approach to achieving interoperability will most
likely involve a combination of de jure, de facto, proprietary, and consortia standards.
63. What do you mean by this?
Consider the changes in modem technology. Within a 36-month period in the 1990s,
data transmission rates for modems increased from 9600 bits per second (bps) to 14,400
bps to 28,800 bps to 33,600 bps to 56,000 bps. The standards on which each new modem
technology was based were originally proprietary. Although users (in most cases) were
given vendor assurances that their modems would be compliant with the forthcoming de
jure standard, users still faced a purchasing dilemma: Should I invest in the newer technol-
ogy now, even though it is proprietary, or should I wait for the technology to be approved
by a formal standards organization before I commit my resources?
64. That's a good question. What's the answer?
Unfortunately, there is no easy answer to this question. You should be cognizant of the
relatively short life cycle of technology and understand that technology will always expe-
rience different stages of maturity as it evolves. This situation, coupled with the lengthy
process of formal standardization, means we cannot rely solely on de jure standards to
achieve interoperability. The realistic approach to achieving interoperability will most

likely involve a combination of de jure, de facto, proprietary, and consortia standards.



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