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100 Chapter 4

Why the Hype?

The use of SDH affords significant benefits to the carrier, as well as
to the end user. Clearly, any technology that is used in the infra-
structure of the network must offer benefit to the end user and car-
rier alike. Otherwise, the user will not take advantage of the
potential share of the services. When we first introduced digital net-
working to the network, many users wanted to access the digital cir-
cuits. Bear in mind that the carriers installed digital services in the
1960s. Yet 1984 was the first time they tariffed use of the digital
architecture to the customer’s door. Mind you, certain exceptions
existed. I personally installed a special assembly in the mid-1970s
using a T-1 from Boston to California. This special arrangement was
both expensive and difficult to work with because of its newness to
end users. However, the carriers had the services in place and con-
verted the backbone networks (wide-area) to all-digital standards-
based infrastructures.They needed to operate in this fashion to meet
the demand for higher-speed communications, reliability expecta-
tions, and cost ratios.
Unfortunately, with the introduction of their networks and stan-
dards, problems still existed. The North American carriers installed
standards-based equipment in their networks, whereas the Euro-
pean carriers installed their own standards-based equipment. The
major problem was that the two did not “speak” with each other. To
solve the problem, gateways were required to interface between the
different pieces of equipment. However, when the SDH and SONET
standards were completed, a new beginning was possible. The inten-
tion of both standards was to enable interoperability and trans-
parency between systems. SDH brings the following advantages:

High-speed transmission rates of up to 10 Gbps in today’s
backbone. SDH is suitable for the overall carrier networks,
which are the information superhighways of today.
Simplified process for add-drop multiplexing. When compared
with the older systems, the PDH networks were extremely
complicated. PDH required that we demultiplex an entire DS-3,
for example, in order to get at an individual DS-0. It is now much