Telecom/1996-04-telecom-walnutcreek.iso/technical/isdn.paper

Text File | 1993-03-11 | 20KB | 414 lines

Date: Thu, 4 Mar 93 18:17:16 -0600
From: John Landwehr <[e-mail]>

The Golden Splice:
Beginning a Global Digital Phone Network

December 1992

John Landwehr
Northwestern University
email: [e-mail]


     On Monday November 16, 1992 the nation's first multi-services
all-digital telephone network was launched.  The phrase "Golden
Splice" was coined on that day to recall the first transcontinental
rail system in 1869, which was completed with the pounding of the
infamous golden spike.  But unlike the rail system, the telephone
system's "tracks" have been in place for years.  With today's
technology, the information sent across the wires is changing.  The
transition is from analog signals to digital, using technology called
ISDN.  This paper will discuss the beginnings of ISDN and how the
world will benefit by communicating in binary numbers.


What is ISDN?

     ISDN, which stands for integrated services digital network, is a
system of digitizing phone networks which has been in the works for
over a decade.  This system allows audio, video, and text data to be
transmitted simultaneously across the world using end-to-end digital
connectivity.

     The original telephone system used analog signals to transmit
a signal across telephone wires.  The voice was carried by modulating
an electric current with a waveform from a microphone.  The receiving
end would then vibrate a speaker coil for the sound to travel back to
the ear through the air.  Most telephones today still use this method.

    Computers, however, are digital machines.  All information
stored on them is represented by a bit, representing a zero or a one.
Multiple bits are used to represent characters, which then can
represent words, numbers, programs, etc.

    The analog signals are just varying voltages sent across the wires
over time.  The digital signals are represented as a positive or
negative voltage changing over time.

    The modem was certainly a big breakthrough in computer
technology.  It allowed computers to communicate with each other by
converting their digital communications into an analog format to
travel through the public phone network.  But there is a limit to the
amount of information that a common analog telephone line can hold.
Currently, it is about 56 kbps.

    ISDN allows multiple digital channels to be operated
simultaneously through the same regular phone jack in a home or
office.  The change comes about when the telephone company's switches
are upgraded to handle digital calls.  Therefore, the same wiring can
be used, but a different signal is transmitted across the line.

    Previously, it was necessary to have a phone line for each
device you wished to use simultaneously.  For example, one line each
for the phone, fax, computer, and live video conference.  Transferring
a file to someone while talking on the phone, and seeing their live
picture on a video screen would require several expensive phone lines.

    Using multiplexing (a method of combining separate data
signals together on one channel such that they may be decoded again at
the destination), it is possible to combine many different digital
data sources and have the information routed to the proper
destination.  Since the line is digital, it is easier to keep the
noise and interference out while combining these signals.

    ISDN technically refers to a specific set of services provided
through a limited and standardized set of interfaces.  This
architecture provides a number of integrated services currently
provided by separate networks.

    ISDN adds capabilities not found in standard phone service.
The main feature is that instead of the phone company sending a ring
voltage signal to ring the bell in your phone, it sends a digital
package that tells who is calling (if available), what type of call it
is (data/voice), and what number was dialed (if multiple numbers are
used for a single line).  ISDN phone equipment is then capable of
making intelligent decisions on how to answer the call.  In the case
of a data call, baud rate and protocol information is also sent,
making the connection instantaneous.


History of ISDN:

     A standards movement was started by the International Telephone
and Telegraph Consultative Committee (CCITT), a United Nations
organization that coordinates international telecommunications.  U.S.
representation to this committee is housed in the Department of State.
The primary objective of CCITT is to standardize telecommunications
globally. Original recommendations of ISDN were in CCITT
Recommendation I.120(1984) which described some initial guidelines for
implementing ISDN. #1

    Local phone networks, especially the regional Bell operating
companies, have long hailed the system, but they have been criticized
in recent years for being slow to implement ISDN.  One good reason for
the delay is the fact that the two major switch-makers, Northern
Telecom, and AT&T selected different ways to implement the CCITT
standards.  These standards didn't always interoperate.  Dick
Notebaert, president of Ameritech Services, compared this situation to
that of earlier 19th century railroading.  "People had different
gauges, different tracks... nothing worked well."#2

    In early 1991, an industry-wide effort began to establish a
specific implementation for ISDN in the U.S.  Members of the industry
agreed to create National ISDN 1 so service users would not have to
know the brand of switch they are connected to in order to buy
equipment and software compatible with it.

TRIP '92 and NISDN-1:

    In November 1992, the Corporation for Open Systems
International (COS) and the North American ISDN Users' Forum (NIUF)
joined forces to create a trade show, called Transcontinental ISDN
Project 1992 (TRIP '92) - the first multicarrier ISDN event in the
U.S.  This exposition, held in Reston, Virginia, featured exhibits of
ISDN products and services as well as the "Golden Splice" event which
marked the commencement of transcontinental ISDN service.#3

    The main purpose of TRIP '92 was for telephone companies and
vendors to prove that standardized ISDN service is available, and that
there are applications to support it.  It was also the true test of
the NISDN-1 agreement to implement specific existing standards to
ensure interoperability among carriers.  Many vendors showed their
products operating in situations such as videoconferencing.

NISDN-1 was created to address 3 major areas:#4
    4 standardizing equipment and services
    4 standardizing telephone company procedures for operation
    4 standardizing communication among central offices

    However, there still might be problems agreeing on this
standard.  In fact, many of the states west of the Mississippi River
will not be able to get NISDN-1 specifications.  Both Southwestern
Bell Corp.  and U.S. West Inc. said that they do not plan to deploy
NISDN-1 software in their central office switches.  They claim that
this will cause incompatibilities with their existing ISDN networks.
This creates problems for many large corporations in the U.S. who wish
to connect their regional offices with ISDN technology.#5

Specifics of ISDN:

     With ISDN, voice and data are carried by bearer channels (B
channel) occupying a bandwidth of 64 kbps each.  A delta channel (D
channel) handles signalling at 16 kbps or 64 kbps.  H channels are
provided for user information at higher bit rates.

      There are three types of ISDN service: Basic Rate ISDN (BRI),
Primary Rate ISDN (PRI), and Broadband ISDN (B-ISDN).

BRI: consists of two 64 kbps B channels and one 16 kbps D channel for
a total of 144 kbps.  The basic service is intended to meet the needs
of most individual users. NISDN-1 focused primarily on making basic
services deployed immediately.

PRI: intended for users with greater capacity requirements.  Typically
the channel structure is 23 B channels plus one 64 kbps D channel for
a total of 1.544 Mbps.  H channels can also be implemented: H0=384
kbps, H11=1536 kbps, H12=1920 kbps.  NISDN-2 will address this
protocol in depth during 1993.

B-ISDN: still in development and will support as much as 150 Mbps, but
will be dependent on a complete optical fiber network.  This could be
a medium for future high definition television (HDTV) projects.

    To access the BRI service, it is necessary for the customer to
subscribe to an ISDN phone line.  Residential customers will also need
to use a device called a Network Terminator 1 (NT1).  The NT1 performs
the multiplexing and converts the 2-wire teleco line to the 4 wire
ISDN signal.

    Many business customers have phone systems that are already
digital.  In this case, connecting to ISDN lines may or may not
require additional hardware, depending on the system.

    Many computer workstations are now being shipped with ISDN
capabilities.  These units connect directly to the NT1, and will
integrate voice/data communications through the system software.  But
most computers require a Terminal Adapter (TA).  This unit converts
ISDN to the serial (RS-232) interface on most computers.  But serial
connections are usually limited to 19.2 Kbps, therefore the TA does
not utilize the entire ISDN bandwidth.

Pricing & Availability:

    More than 56% (115 million lines) of the regional Bell
operating companies will have ISDN network access by late 1994.#6 In
Chicago, Ameritech officials say that 37% of the market, 1.2 million
lines, will be ISDN by year-end 1992, and the entire metropolitan area
of 4.5 million lines, by April 1993.  Most of the 5 state Ameritech
service region and major U.S. cities should be wired for ISDN by 1994.

    Bellcore has set up a national ISDN information clearing house
hotline at 800-992-4736 for information about ISDN availability.

    Many companies are using ISDN where service is not yet
available.  This is possible by using other digital communications
methods at the local level.  A common method is to use a T1 line, or a
fractional T1 line to connect the computing facility to a switch that
does provide ISDN access.  A T1 line multiplexes twenty-four 64 kbps
channels together over a single line.  A fractional T1 line is simply
a chosen portion of the full T1 circuit.

    Pricing still seems to be the least standardized part of ISDN.
Installation charges generally run from $200-$400 for BRI service.
Monthly charges are often in the $15-$45 range, plus usage charges.
NT1 prices are $200-$300, and TAs are $600-$1200.  Eventually, pricing
is expected to be only slightly more than standard analog service.

Other digital services:

    Switched 56: Unlike ISDN, this service is already offered by
most carriers.  It creates a virtual network over existing public
phone lines with a 56 Kbps data rate.  This service is cheap, but
slow; therefore, it is ideal for intermittent data swapping between
WANs.

    SMDS (Switched Multi-megabit Data Services): Using a
connectionless networking plan, each SMDS packet has its own address
and does not require a virtual circuit.  Proposed speeds are from 1.5
Mbps to 45 Mbps using a fixed-length packet of 53 KB.  Many regional
carriers are beginning to offer this service for local traffic.

    ATM (Asynchronous Transfer Mode): Using the same 53 KB packets
as SMDS, ATM uses virtual circuits to transfer data at speeds of 34
Mbps to multiple gigabits per second.  The CCITT has decided on ATM as
the transport standard for broadband ISDN when it becomes available.
ATM is expected to be fully supported by the phone networks in 1995 or
1996.

Applications of ISDN:

    Businesses have the potential to be the biggest winners in the
future of ISDN services.  It will be cost effective for companies to
replace numerous existing analog lines with fewer ISDN lines that can
handle multiple applications simultaneously.  But for the average
residential user, there are also many benefits.

    One of the most talked about ISDN applications is
videoconferencing.  Previously, systems cost well over $100,000.  Now
the concept of personal, desktop videoconferencing is available using
common personal computers and workstations.  One channel is used for
voice, and the other channel is used for the display of moving video
pictures.  The price for videoconferencing is dropping so quickly,
that it is expected to be affordable to most businesses by late 1993.

    Along similar lines, is a shared electronic chalk board.
Users can talk in a conference arrangement and also illustrate written
ideas to remote locations.  Slide presentations could also be given in
this manner.

    Everyone appreciates the simple fact that is it possible to
have the single phone jack do more than one task.  The modem no longer
needs to tie up the phone line.  It is even possible to troubleshoot
computers remotely by simultaneously talking to the computer operator
and logging into that system remotely with the same ISDN line.  But
there are certainly far more exciting uses for this technology.

ISDN in education:

    John Mayo, AT&T Bell Laboratories president stated that, "The
new telecommunications technology that will impact education the most
over the next five years, will be ISDN."#7 The classroom will no
longer have physical boundaries.  Ideas of collaborative learning to
gain outside expertise will be easier to implement over the existing
telephone lines.  Students will be able to communicate with schools
across the city, or across the world.

    The most exciting possibilities involve the video
capabilities. Videoconferences can be used for instruction videos, or
transmitting a school play.  Students can see far away lands for the
first time, or speak with a pen-pal halfway around the world.

    Exposing children to computers and networking at an early age
seems to be the trend.  ISDN allows the students' computers to access
more resources and will teach them how to collaborate during their
learning process.  The current generation of children will certainly
be expected to use the computer as a powerful tool much like the
calculator and typewriter were used.

Telecommuting:

    Telecommuting is a new term used to describe the modern way of
working from home.  There certainly is some motivation to avoid the
daily commute if all of the work can be done from home.  It will take
managers a while to get used to this idea, and it certainly does
require some self motivation.  But with current technology, it is
possible to have the remote computer respond as if there were
expensive network cable running the whole way.

    NeXT Computer, Inc. has started bundling the new release of
their system software with tools for maintaining ISDN links.  The
software is perfect for telecommuting.  It allows the home computer to
connect to the office via an ISDN line and mount all file systems and
network resources.  Any work that could be done on the office computer
can be performed on the home computer.  Although NeXT doesn't have
ISDN jacks on the system, Hayes Corporation has engineered a device
that connects the Digital Signal Processor (DSP) port of the NeXT to
an NT1.  This allows the full use of ISDN bandwidth, whereas a
terminal adapter connected to the serial port severely limits
bandwidth.

    Other systems can use popular protocols such as the Serial
Line Interface Protocol (SLIP) or the Point-to-Point Protocol (PPP).
The biggest advantage of using these protocols is actually being a
node of a remote network.  When you want access to resources not
available locally, you can automatically connect.  There is no longer
the limitation of simply transferring files using a modem and terminal
software. The computer will actually think it is connected to ethernet
over ISDN.#8

Possible problems with a digital phone network:

    One of the first problems that comes to mind is concerning
security.  This is actually not a problem for the user, because
digital transmissions are easily capable of being encrypted.  In fact,
an encryption key of 128 bits or more would prevent even the latest
supercomputers from decoding the transmission.

    The concern comes from the National Security Agency.  They are
worried about ISDN making wiretapping mo| computer industry to secure
a back door into encrypted messages.  They are also proposing new
legislation to the FCC that would make all digital transmissions
capable of being monitored by electronic surveillance.

    The director of the FBI, William S. Sessions, is quoted as
saying, "Terrorists, violent criminals, kidnappers, drug cartels and
other criminal organizations will be able to carry out their illegal
activities using the telecommunications system without detection."#9

    Finally, an example of the socio-political implications of
ISDN has been summed up by Leonard R.  Sussman, who predicted that
technology and globally linked networks would result in the breakdown
of censorious and suppressive political systems, meaning that
governments would have a difficult time hiding information from their
people because of the rapid methods of transferring information at a
global level.#10

The future:

    Computers are rapidly becoming connected together to help
people that want to communicate with each other, regardless of
location.  The trend is definitely toward a digital world.  Compact
Disc players, telephones, computers, and televisions are all beginning
to use digital technology.

    The problem with ISDN hasn't been the technology, it's the
politics.  The reason ISDN was so slow to catch on was that the
different telephone companies' equipment didn't work together.  Until
recently, it has not been possible to make an ISDN call from one
telephone service area to another.  As a result, users have been
isolated from each other.  With the advent of the National ISDN-1
network, standardized ISDN will become available over both local and
long-distance telephone networks.  When NISDN-2 kicks in by late 1993,
it will add PRI services capable of 1.5 Mbps transmissions.

    Pricing and local availability are now the key issues.  In
some areas, making an ISDN call is the same price as an analog call.
But other carriers are making ISDN prohibitively expensive.  While
most metropolitan areas will be ISDN capable in several months,
widespread residential use will not come as quickly.

    Settling these political issues will affect ISDN's success in
the U.S.  Many claim that competing technologies are already far ahead
of ISDN, but they are still facing many standardization and
availability issues that ISDN has already begun conquering.

    NISDN-1 is only the beginning.  It is the first step in
expanding the nation's phone network by making it digital.  Next, it
will be a matter of making those zeros and ones travel quicker as we
see and hear information from all over the world, instantaneously.


Sources Used:

#1 Stallings, William.  ISDN: An Introduction.  Collier Macmillan
Canada, Inc. 1989.

#2 Ibata, David.  "New information highway to the future." Chicago
Tribune. Pg. 17.  November 17, 1992.

#3 Johnson, Johna T.  "ISDN Goes Nationwide, but Will Users Want It?"
Data Communications.  November 1992.

#4 "National ISDN Network Launches New Era in Compatibility."
Communications Daily.  November 17, 1992.

#5 Sweeney, Terry.  "Two Bells Frustrate National ISDN Effort."
Communications Week.  November 23, 1992.

#6 "One Service for All."  Computerworld.  November 9, 1992.

#7 "Appalachian State University, Southern Bell and AT&T Unveil and
Demonstrate ISDN-driven Distance Network."  Business Wire.  October 6,
1992.

#8 Landwehr, John T.  "Taking your network home."
NeXT Support Bulletin. Summer 1992.

#9 "FBI Fear Phone Advances Will Hamper Wiretapping."  LA Times, March
7, 1992.

#10 Sussman, Leonard R. Power, The Press, & The Technology of Freedom,
The Coming Age of ISDN.  Freedom House. 1989.