                                     ISDN
                     Integrated Services Digital Network
                                 by Dan Mertz
                                  72470,1676


ISDN, four big letters holding little insight to meaning or potential. 
Created in the 1980's, ISDN is actually a standard for digitizing all
telephone company services.  


Since the days of Alexander Graham Bell, voice communications have been
carried in analog form.  In the 1950's telephone companies realized the
benefits of digital signals and began the process of converting their
cross-country lines.  The last piece in the conversion process is the local
loop.  


After much hype following introduction of the ISDN standards in the mid-
1980's, potential users suggested that ISDN stood for "Innovations
Subscribers Don't Need."  Early in the 1990's users still found little use
for the new standards, mockingly changing the implied meaning of ISDN to
"It Still Does Nothing."


However, recent developments bring new meaning to ISDN.  In the ISDN Forum
on Compuserve, a user hawking value added re-seller services for ISDN
suggest a new definition -- "I Smell Dollars Nearby."  And, the May 8, 1995
issue of Multichannel News, suggests this more recent meaning for the
acronym:
               It Starts Delivering Now

This paper will briefly discuss the technical specifications for ISDN, its
history, and some of the implementation issues.  Somewhat more in-depth
coverage of current implementation issues and current uses of ISDN will be
provided.

         
                                  TECHNICAL                       SPECIFICATIONS


ISDN contains the standards for digitizing switched communications (data,
video, and other types in addition to voice) from the local telephone
company switching hub into user (premises) equipment.

One advantage the standard supplies is the ability to transmit over the
already installed twisted-pair copper wire now used for voice(and other
analog) communications.  Each channel can carry 64Kbps per second.  The
data, or bearer channel is called the B-channel.  Also, another channel,
called the D channel (D=delta)is used for signaling.

There are two types of ISDN service.  They are basic rate interface
(BRI)and primary rate interface (PRI).  The BRI service provides two 64
Kbps bearer channels and one D channel.  BRI is also referred to as 2B + D. 
The primary rate interface, PRI, provides 23 bearer channels and one D
channel, and is also known as 23B + D.



At the user premises, proceeding from the wall outlet to the device
(computer, phone, fax, etc), the service is connected to what's known as an
NT-1.  From the NT-1 the digitized signal travels through the ISDN Terminal
Adapter.  In early implementation's, these two devices were separate
pieces of hardware that had be purchased from different sources.  Even
today, one must be an informed buyer.  


However, as the technology blossoms, manufacturers are beginning to build
the NT-1 and the ISDN Terminal Adapter into one package.  In computer
applications, like with most add-ons, the package can be implemented as an
external device connected to the computer through a serial port.  An RJ-11
phone jack is built into the external device forconnection to the incoming
ISDN line. The hardware can be also be added internally, as a card placed
in an available expansion slot.



The NT-1, Network Terminating Device, serves as the interface between the
premises equipment and the local phone company network.  The terminal
adapter is where the two (or more) channels are integrated into one data
stream.  It is here that the two 64Kbps bearer channels are combined to
create a total thru-put of 128Kbps.



There is no special software required to implement ISDN.  The standard,
commercial communications packages like Crosstalk,Procom,and PC Anywhere
work straight from the box.  The special applications like video
conferencing come with software required to operate the application.



                                  A BRIEF HI                          STORY

                                  
                                  Since the beginning days, telephone service has been referred to as POTS --
Plain Old Telephone Service.  Voice communication was analog.  But, by the
1950's national providers were beginning to understand and deploy digital
service.


By the 1970's inter-exchange carriers recognized the full benefit of
digital transmission.  Digital transmission provided the ability to
regenerate the signal without increasing noise levels at repeater sites. By
the end of the 1970's an all digital backbone had been deployed on key
routes across the United States.


In the United States, by the early 1980's the entire telephone
infrastructure, except for the local loop and the telephone itself, had
been digitized.


A global goal being fostered (both then and now) by the United Nations is
total digitization of all telephone systems, world-wide.  Such an
infrastructure will allow international data exchange.  


The International Telephone & Telegraph Consultation Committee (CCITT) was
the United Nations Committee responsible for establishing and publishing
the standards for digital data communications -- ISDN, Integrated Services
Digital Networks.  The standards were published and presented in 1984.


From there, as Communications Week Executive Editor Chris Roeckl puts it,
"In the 1980's ISDN was long on hype and short on implementation."
However, recent developments have placed ISDN at the cutting edge.  Roeckl
continues, "But now organizations are flocking to ISDN to improve
communications with branch locations and telecommuters."



Presently, the baby Bell's are providing about 300,000 ISDN lines.  That's
four times as many as there were in 1993.  Dataquest, a consultancy, expect
the number of ISDN lines in america to triple by 1998.  Bellcore expects 13
million ISDN lines to be in service by the year 2000.

IMPLEMENTATION ISSUES

The literature explores many reasons for ISDN's early failures, but there
were two seemed to be two main problems that spawmed many others.  The
first issue revolved around the manufacture of switching equipment.  While
standards were in place, the interpretations and implementation of those
standards differed.  The two main switch makers, AT&T and Northern Telecom
developed equipment that would not inter-operate.


As a result, the local service providers were hesitant to launch ISDN.  In
a letter to the editor (Communications Week, June 19, 1995) Tom Bader, an
ISDN planner at Ameritech explains.  He says that Ameritech didn't
seriously consider offering ISDN because of a lack of standard switching. 
Their view was that the big demand for ISDN would occur through different
switches, but the switching equipment was proprietary.  He finishes by
noting that vendors are now supplying switches manufactured to common
standards, making full scale deployment of the service possible.



The standardization process was led by Bellcore in 1991.  The result

was NISDN-1.  Three key elements were:

     - Standardization of equipment and services
     - Standardization of telephone company procedures for operations
     - Standardization of procedures for communications between             
  central offices


The second early issue concerned the Federal Communications Commission's
ruling on how local telephone companies must charge for the service.  When
the Baby Bell's began operation in the mid 1980's, the FCC said charges
must be sufficient to recover the cost of the local loop's operation.  The
procedure was to mandate a per channel charge.


In effect, a residential subscriber had one channel of communication in the
sense that only one phone call could be handle at a time.  ISDN is a multi
channel service.  As was described above, basic rate interface (BRI) offers
two channels, allowing for data transfer one one channel and voice
communications on the other.


As a result, the FCC ruled that the user of BRI must be two subscriber line
charges, effectively doubling the cost of the service.  Earlier this year,
Bell Atlantic's "Emergency Petition for Waiver" (2/10/95) asked for relief
from the double charge situation.



Relief was granted, and the FCC published "Notice of Proposed Rulemaking"
(FCC Document 95-212).  The process is one of requesting comment on how to
charge for ISDN service.  The initial section of the document notes that
when subscriber line charges (SLC's) were implemented in the mid-1980's
ISDN was not even considered.  In the request the FCC suggest five general
alternatives with a total of 14 options (for determining ISDN charges)
offered.  The cut off date for comments was July 14, 1995.  Given the move
for a deregulated environment, it appears that the FCC will rule favorably
for moderate charges, allowing both residential and business users
affordable connection rates.



TODAY'S IMPLEMENTATION ISSUES
                      

To be sure, ISDN is in the early stage of adoption, and many implementation
issues remain to be solved.  It is not yet as simple as plug and play. In a
recent survey of network managers using ISDN, 43.2% said the biggest
disadvantage of the service is availability.

At the local phone company level, availability of ISDN to customers ranges
from a low of 18% for GTE customers to a high of 90% for Bell Atlantic
subscribers.


At the end of Bell Atlantic's recently ended second quarter (6/30/95) the
local telephone company's number of ISDN lines totaled 120,000 up 75% from
year earlier levels.  Southwest Bell will be spending $300 million over
the next five years to make ISDN service universally available in its
service area.  The company notes increasing demand as the force driving the
conversion-spending.



While demand is on the rise, some feel that usage will not sweep the nation
until implementation gets easier.  The issue of standards was discussed
previously.  But, there are still issues of interpretation that apparently
need to be addressed.  For example, videoconferencing needs a lot of speed
and bandwidth.  ISDN is ideal for the purpose.  However, it is difficult to
connect unlike equipment (i.e.- from different manufacturers).  The
standard exists.  For videoconferencing the standards are found in H.320. 
But, early in the implementation phase, the interpretations and
implementations of the standards vary.



Communications Week recently offered these ISDN implementation
procedures:
     
     -Take control of the process from the beginning.  Don't assume        
vendors are all-knowledgeable.
     -Study and understand ISDN the ISDN technology.
     -Make sure the vendors understand ISDN technology (even the local     
phone company representatives)
     -Choose applications & equipment before ordering ISDN service.
     -Don't let inexperienced installers install your ISDN service.        
ISDN lines do need to be configured and conditioned before        using.


Finally, cost still appears to be an issue although its relevance is
fading.  In the recent past West Virginia University installed 1,700 Basic
Rate Interface (BRI) circuits, but as of 6/5/95 had not deployed them
because of cost.  As was noted earlier, the Federal Communications
Commission is now determining how Subscriber Line Charges (SLC's) should be
determined for ISDN users.  Presumably, the ruling will favor users with
lower charges.



Also, the local telephone companies are realizing elasticity of demand. 
Price reductions do lead to increased usage that generates greater revenues
for the local telecos.  Early in June (1995) Bell Atlantic announced a 60%
drop in ISDN charges.  For Basic Rate Interface Service, the per-minute,
per-channel charge for business use dropped from five cents a minute to two
cents a minute.  A Bell Atlantic directors explained the drop by saying,
"One of the most significant barriers to widespread acceptance of this
technology was price." 



UBS securities analyst Linda Metzler, responding to Bell Atlantic's 1995
second quarter results said she was struck by the (financial) contribution
of Bell Atlantic 's integrated services digital network and other enhanced
vertical services.  Analysts expected second quarter earnings per share to
be $1.00.  The actual result was $1.02 compared to 95-cents in the second
quarter of 1994.



CURRENT AND FUTURE USES
                      

What ISDN provides is an economical means for creating an the WAN portion
of an enterprise network.  Prior to ISDN, interconnection could be achieved
through rental of expensive, dedicated T1 lines, or, by using the existing
analog telephone service via a comparatively slow modem.

Increasingly, there is demand for transmission of graphics, motion, and
sound in addition to text and data.  Bandwidth is essential for all of
these purposes.  For example, Schindler Elevator Corp. maintains a
centralized image database.  Service people equipped with portable PC's can
access this "multimedia" information to obtain pictures of known equipment
problems and suggestions for elevator service, complete with a supervisor
walking them through simple and complicated repairs. ISDN is the medium
over which these images (voice, video, and data) are transmitted.

ISDN is also providing locally administered, cash strapped, schools with
the ability to interconnect for the first time.  In Cincinnati, ISDN has
been deployed for the purpose of implementing a supporting administrative
network.  ISDN will be used this fall to connect 83 schools (PC's, mini's,
and servers).  Local administration explains that ISDN was selected because
it provide the most bandwidth at the best price.  

The implementation will replace a manual system for tracking enrollment,
daily attendance, student records, and accounting & purchasing information. 
Also, in-classroom applications, distance learning, videoconferencing, and
any client/server architecture will be supported by the new ISDN-based
service.

In San Diego, the Technical Museum of Innovation will be connected to San
Diego State University via ISDN service.  This test will provided needed
experience for the museum to offer connection to other schools, allowing
students access to the museums resources without the need for costly time
away from the local school.

AT&T and MCI recently announced an ISDN based multi-media service that
allows customers to place interactive voice and data calls.  the service
can be used for remote LAN access, videoconferencing, and customer support. 
Also, both companies envision that the service will allow buyers to browse
on-line catalogs.  Also, it will enhance interactive support and desktop
collaborations.  

The on-line service Lexis-Nexis is testing the AT&T WorldWork 800 service. 
The provider is training new users in use of its on-line service through
interactive, multi-media means.  Previously, new users went to one of 50
training centers, or, a trainer went to the customer's site.


The laundry list of uses of ISDN includes:

     -Videoconferencing
     -LAN to LAN Connections
     -LAN to Host Connections
     -Telecommuting
     -Internet Hook-Up
     -Remote Backup
     -Fast fax
     -Commercial On-Line Services
     -Remote Systems Management

Compuserve and Prodigy are playing with it.  Recently, Compuserve announced
that it would roll-out ISDN connection by means of a 1-800 number.  The
service expects local ISDN service to be available in 10 cities by the end
of August (1995).


ISDN almost seems essential for collecting visual images from the World
Wide Web.  Pacific Bell is pushing ISDN as an efficient means for Internet
access.


Our local newspaper, the Richmond Times-Dispatch, is using ISDN to receive
ads directly from advertisers on a system supplied by ImageNet,
Bernardsville, New Jersey.



At the moment the ISDN service is fragmented.  A potential user is saddled
with the responsibility of selecting the applications, securing the
necessary premises hardware, and selecting the correct ISDN service from
the local provider.  Pacific Bell is working hard to simplify the process
by providing turnkey solutions.  Currently, PacBell is cooperating with
Microsoft and CompUSA to provide a package solution for Windows 95 and
Microsoft NT.


But, the full capabilities and the applications that use those capabilities
probably remain uncovered.  As the service is adopted, creativity and
ingenuity will spawn new and more productive uses. One telecommunications
recently summed-up the possibilities by saying, "People are putting in ISDN
lines for one thing and now they're finding other uses for it.  That's the
sign of a mature technology."


Let the bits fly!