ISDN Applications
Although ISDN has a relatively broad range of functionality, its utility comes largely from the data communications applications that it enables. This section provides a few examples of how ISDN technology is being used today.
1) LAN
to LAN Connectivity
One of the
most common ISDN applications will be for on-demand LAN-to-LAN connectivity.
Today's corporations may have dozens or hundreds of branch offices requiring
connections to the corporate backbone. Typically, these connections are
not required all the time, so a leased line or Frame Relay service may
not be cost-effective. Moreover, to protect against failures, there must
be some degree of redundancy, a costly proposition with a permanent connection.
Although analog telephone lines have occasionally been used for LAN-to-LAN
connections, the bandwidth supplied is insufficient for most applications,
while the slow call-setup lends further inefficiency to this solution.ISDN
is an ideal alternative, as it enables high speed, cost-effective on-demand
networks to be set up. Although no permanent connections exist, branch
office routers can be configured to connect to other offices as the need
arises, ensuring that usage fees are incurred only when the link is used.
In addition, ISDN's bandwidth-on-demand functionality (adding B-channels
as necessary) ensures that communications capacity will not be restricted
to the preset bandwidth of a leased line. Moreover, ISDN's on-demand nature
enables fault-protection without additional expense, as alternative ISDN
numbers can be dialed should primary links fail.
2) Communication
Link Backup
Instead of
a full migration to ISDN, many corporations are using ISDN as a backup
link to leased or Frame Relay connections, providing a cost effective means
to provide fault-tolerant connections between offices. Backup links can
be set up very quickly, and if needed can even provide backup access line
to a downed access line into a Frame Relay or X.25 packet-switched network.
Perhaps one of the most significant benefits of ISDN in this capacity is
that it can protect against equipment failures (not just line failures)
at intermediate routing nodes by enabling alternative destinations to be
dialed. As corporations become more dependent on their data communications
networks, ISDN provides a reliable means of establishing critical backup
connections. Some corporations have attempted to use standard phone lines
and modems to back up their leased lines, but at a tremendous sacrifice
of bandwidth. ISDN can be used as an affordable backup link rapidly setting
up high bandwidth pipes whenever they are needed.
3) Telecommuting
Applications
Telecommuting
is the natural product of traffic congestion, legislation limiting commuting
by car, demands from workers for a better quality of life, and corporate
requirements for increased productivity. ISDN enables this new way of working
which has already been implemented on a wide scale by many companies.ISDN
gives workers their office tools at home. Through a single BRI connection,
users are able to access the office LAN, e-mail, the office telephone network,
and on-line database services. Rather than wasting time commuting, telecommuting
enables users to accomplish more, within a less stressful environment.
This logic is bolstered by studies at Bell Northern Research which have
demonstrated increases in productivity on the order of 20% to 50%, with
workers spending an average of 20% more time doing productive work.
In order to fully gain these increases in productivity, ISDN equipment must not only leverage the performance of ISDN technology, but must also be able to interoperate with the analog equipment that is still prevalent throughout the corporate world. Thus remote users should also be able to connect to V.32bis and V.34 modems as well as standard Group 3 fax equipment.
4) Internet
and Online Services
Anyone who
has recently used the Internet's World Wide Web (WWW) or any commercial
online service can appreciate that analog connections are inadequate for
present data communications requirements. With standard phone lines, users
spend more time waiting for information than using it. ISDN provides a
means to productively access online information, by reducing both waiting
time and communications costs with bandwidth that far exceeds that of an
analog modem. Compression is less important than the raw bandwidth that
ISDN offers since most WWW traffic is pre-compressed and because compression
is unlikely to interoperate with service providers' ISDN equipment. Internet
service providers are already aggressively pursuing this market, as companies
such as PSI, CompuServe and MCI are implementing plans which enable ISDN
access on many of their North American points of presence.
5) Application
Connectivity
ISDN technology
allows corporations to tightly integrate applications with the WAN via
application programming interfaces (APIs) which allow applications to directly
control ISDN connections. The Common ISDN API (CAPI 1.1), one such API,
has played a significant role in ISDN's success in Germany, as it allows
vendors to sell ISDN applications which can be used with any CAPI-compliant
ISDN hardware. Prior to the popularization of CAPI, users were bound to
purchase both applications and hardware from the same vendor. Although
CAPI 1.1 was primarily a German standard, CAPI 2.0 has begun to emerge
as a worldwide standard, supported in Europe by ETSI and worldwide by manufacturers
and application developers such as Novell and Microsoft. Several alternative
specifications have been put forward, but none have the application support
and corporate backing which CAPI 2.0 presently enjoys.Another API likely
to significantly influence the acceptance of ISDN on the desktop is TAPI,
a Microsoft API which facilitates the integration of telephony devices
on Windows desktops. Thus, aside from enabling high speed data connectivity,
ISDN will ease the integration of telephony and data applications. A TAPI-compliant
application could, for instance, communicate to a remote telemarketer the
customer details that would increase the overall likelihood of a successful
sale. Applications such as this, and others yet unimagined, will change
the dynamics of customer service as we know it today.
6) Videoconferencing
Although
videoconferencing can be accomplished using alternative technology such
as leased lines, ISDN is the first technology that enables low-cost, on-demand
videoconferences. Low-cost videoconferencing solutions, using just two
B-channels on a BRI connection, are already commonplace as business adopts
this method of dramatically reducing travel expenses. For better video
and audio quality, solutions which provide television-quality transmission
through six B-channels are available. Standards-based solutions follow
H.320 specifications, and today, this is can be can be implemented in software,
without requiring the use of specialized videoconferencing hardware. The
T.120 specification further stretches the usefulness of this technology
by facilitating multipoint workgroup collaboration, so that many users
can simultaneously share video and data. It appears that this single application
of ISDN, with its immediate cost savings, may alone propel the technology
to the forefront of the corporate world.
7) Voice
In addition
to the myriad of data communications applications, ISDN also supports the
voice applications which today, form the basis of a large segment of everyday
business. ISDN improves upon existing voice technologies by providing clearer
sound, and a host of features such as caller identification and conferencing
which were previously available on a region by region basis only. Although
voice is unlikely to drive ISDN's implementation, voice networks will be
a significant beneficiary of the accelerated convergence between voice
and data networks brought about by ISDN. The development of this technology
is already visible in the form of handsets that integrate directly with
PC-based ISDN adapters.