The ideal telecommunication network has the following characteristics:
broadband, multi-media, multi-point, multi-rate and economical
implementation for a diversity of services (multi-services). The
Broadband Integrated Services Digital Network (B-ISDN) was planned to
provide these characteristics.
Asynchronous Transfer Mode
Asynchronous Transfer Mode (ATM) was
promoted as a target technology for meeting these requirements.
1 Communication services
2 Differences from old telephony
3 A single network for multiple services
3.1 Traditional networks
3.2 Benefits of a single network for multiple services
3.3 Fiber optics for broadband networks and MSO
4.2 Requirements of the types of traffic
5 See also
7 External links
Personal computing facilitated easy access, manipulation, storage, and
exchange of information, and required reliable data transmission.
Communicating documents by images and the use of high-resolution
graphics terminals provided a more natural and informative mode of
human interaction than do voice and data alone.
enhances group interaction at a distance. High-definition
entertainment video improves the quality of pictures, but requires
much higher transmission rates.
These new data transmission requirements may require new transmission
means other than the present overcrowded radio spectrum. A
modern telecommunications network (such as the broadband network) must
provide all these different services (multi-services) to the user.
Differences from old telephony
Conventional telephony communication used:
the voice medium only,
connected only two telephones per telephone call, and
used circuits of fixed bit-rates.
Modern services can be:
These aspects are examined individually in the following three
A multi-media call may communicate audio, data, still images, or
full-motion video, or any combination of these media. Each medium has
different demands for communication quality, such as:
signal latency within the network, and
signal fidelity upon delivery by the network.
The information content of each medium may affect the information
generated by other media. For example, voice could be transcribed into
data via voice recognition, and data commands may control the way
voice and video are presented. These interactions most often occur at
the communication terminals, but may also occur within the
Traditional voice calls are predominantly two party calls, requiring a
point-to-point connection using only the voice medium. To access
pictorial information in a remote database would require a
point-to-point connection that sends low bit-rate queries to the
database and high bit-rate video from the database. Entertainment
video applications are largely point-to-multi-point connections,
requiring one-way communication of full motion video and audio from
the program source to the viewers.
Video teleconferencing involves
connections among many parties, communicating voice, video, as well as
data. Offering future services thus requires flexible management of
the connection and media requests of a multi-point, multi-media
A multi-rate service network is one which flexibly allocates
transmission capacity to connections. A multi-media network has to
support a broad range of bit-rates demanded by connections, not only
because there are many communication media, but also because a
communication medium may be encoded by algorithms with different
bit-rates. For example, audio signals can be encoded with bit-rates
ranging from less than 1 kbit/s to hundreds of kbit/s, using different
encoding algorithms with a wide range of complexity and quality of
audio reproduction. Similarly, full motion video signals may be
encoded with bit-rates ranging from less than 1 Mbit/s to hundreds of
Mbit/s. Thus a network transporting both video and audio signals may
have to integrate traffic with a very broad range of bit-rates.
A single network for multiple services
Traditionally, the various services mentioned above were carried via
separate networks: voice on the telephone network, data on computer
networks such as local area networks, video teleconferencing on
private corporate networks, and television on broadcast radio or cable
These networks were largely engineered for a specific application and
are not suited to other applications. For example, the traditional
telephone network is too noisy and inefficient for bursty data
communication. On the other hand, data networks which store and
forward messages using computers had limited connectivity, usually did
not have sufficient bandwidth for digitised voice and video signals,
and suffer from unacceptable delays for the real-time signals.
Television networks using radio or cables were largely broadcast
networks with minimum switching facilities.
Benefits of a single network for multiple services
It was desirable to have a single network for providing all these
communication services to achieve the economy of sharing. This economy
motivates the general idea of an integrated services network.
Integration avoids the need for many overlaying networks, which
complicates network management and reduces flexibility in the
introduction and evolution of services. This integration was made
possible with advances in broadband technologies and high-speed
information processing of the 1990s.
Fiber optics for broadband networks and MSO
While multiple network structures were capable of supporting broadband
services, an ever-increasing percentage of broadband and MSO providers
opted for fibre-optic network structures to support both present and
future bandwidth requirements.
CATV (cable television),
HDTV (high definition television), VoIP
(voice over internet protocol), and broadband internet are some of the
most common applications now being supported by fibre optic networks,
in some cases directly to the home (FTTh – Fibre To The Home). These
types of fibre optic networks incorporate a wide variety of products
to support and distribute the signal from the central office to an
optic node, and ultimately to the subscriber (end-user).
Modern networks have to carry integrated traffic consisting of voice,
video and data. The
Broadband Integrated Services Digital Network
(B-ISDN) was designed for these needs. The types of traffic
supported by a broadband network can be classified according to three
Bandwidth is the amount of network capacity required to support a
Latency is the amount of delay associated with a connection.
Requesting low latency in the quality of service (QoS) profile means
that the cells need to travel quickly from one point in the network to
Cell-delay variation (CDV) is the range of delays experienced by each
group of associated cells. Low cell-delay variation means a group of
cells must travel through the network without getting too far apart
from one another.
Requirements of the types of traffic
The types of traffic found in a broadband network (with examples) and
their respective requirements are summarised in Table 1.
Table 1: Network traffic types and their requirements
Voice, guaranteed circuit emulation
Asynchronous Transfer Mode
Asynchronous Transfer Mode (ATM)
Teletraffic engineering in broadband networks
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Networks. Artech House. ISBN 0-89006-622-1.
^ a b c d e f Hui J. Switching and traffic theory for integrated
broadband networks. Kluwer Academic Publishers, 1990.
^ a b Sexton M.; Reid A. (1997).
Broadband Networking: ATM, SDH and
SONET. Boston, London: Artech House Inc.
^ a b Ferguson P.; Huston G. (1998). Quality of Service: Delivering
QoS on the Internet and in Corporate Networks. John Wiley & Sons,
Inc. ISBN 0-471-24358-2.
^ Jain, Raj (1996). "Congestion Control and Traffic Management in ATM
Networks". Invited submission to Computer Networks and ISDN Systems.
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original on 19 June 2004. Retrieved 7 March 2005.
^ a b Juliano, Mark. "ATM Traffic Control". Retrieved 3 March
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