
Date: Thu, 4 Mar 93 18:17:16 -0600

From: John Landwehr <jland@nwu.edu>

The Golden Splice:

Beginning a Global Digital Phone Network

December 1992

John Landwehr

Northwestern University

email: jland@nwu.edu

     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.


