by Abhijit S. Pandya; Ercan Sen CRC Press, CRC Press LLC
ISBN: 0849331390 Pub Date: 110198
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Chapter 3 Services Offered through ATM Networks
One of the key promises of ATM technology besides consolidation of current telecommunication technologies is to provide services, which are not easy or economical to provide with existing
technologies. Some of the key characteristics of these services are: high bandwidth demand, long service duration, bursty traffic patterns, varying quality of service requirements, and asymmetrical bandwidth
usage. In this chapter, we will investigate some of these services such as Internet, Video on Demand, Video Telephony, Distant LearningMedicine and Telecommuting, and explain how ATM can provide
these services economically.
Although some of these services we just mentioned are currently being offered through the existing public telephone network, they are too expensive to be afforded by the general public or there is not enough
bandwidth available to fully utilize these services. Additionally, these fairly new services put a significant burden on the current telephony network that was originally designed for carrying traditional voice traffic.
The voice traffic can be characterized as low bandwidth 64 Kbits, symmetrical, delay sensitive and short service duration, i.e., average 3-minute call duration. However, the new services require bandwidth in the
order of Mbits and the typical service time can be considered in hours. Due to the capacity limitation of the present telephony network, these services are offered either at a premium price or at a lower bandwidth
with substantially lower quality.
I. Internet Service
At the present time, Internet service is expanding rapidly. With the current growth rate it can be assumed that it will surpass the traditional voice service in the near future particularly in the United States.
Especially, with the possibility of offering very cheap voice over Internet service, the Internet poses a significant challenge for telephone network operators.
Figure 3-1 The traditional Internet Service Offering.
Telephone network operators are at a crossroad in terms of how to deal with the explosive growth of the Internet service. On the one hand, they have to invest in the infrastructure to deal with the bandwidth
demand created by Internet service while figuring out a way to deal with the competitive pressure the Internet is bearing on them for the voice service. The current Internet service offering via the traditional
telephone network is shown in Figure 3-1.
However, the cable-TV network is a shared medium. Hence, as the number of cable modem users increases, it will not be possible to sustain the same bandwidth allocation per user or the cable operators
have to limit the number of users to sustain the same bandwidth level per user. Possible Internet service offerings via cable modem are shown in Figure 3-2 and Figure 3-3. In Figure 3-2, the cable company
provides both the access and ISP service as a package bundled. In Figure 3-3, the access and ISP service are separated unbundled. The cable company charges an access fee while the ISP provider charges for
the content.
The second technology solution is the Asymmetrical Digital Subscriber ADSL technology to increase the bandwidth to telephone subscribers up to 6 Mbitsec range. The ADSL technology allows separation of
high bandwidth Internet traffic from the low bandwidth voice traffic at the central office interface. Hence, a telephone network operator can divert the bursty Internet traffic to another network such as Frame Relay
or ATM network. With this approach the telephone network operator can protect the quality of service for the traditional voice traffic.
Figure 3-2 Internet service offering via cable modem in which both the access and ISP service are
provided by the cable company.
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