|
Introduction
The Internet is placing ever-increasing burdens on existing
telecommunications equipment. New voice, data and video
conferencing applications are coexisting on circuit-switched
networks primarily designed for lower bandwidth voice
communications. In order to attain the performance required
by these applications, new wideband packetswitched networks
are supplementing the existing network to provide an
enhanced network infrastructure. The eventual outcome will
be flawless integration of dissimilar applications including
CD quality audio, Web browsing, e-mail, streaming video,
video on demand and telephony or VOIP (Voice Over IP). To
accomplish this feat, telephony, wireless, and fiber based
Internet systems will increase in complexity. Furthermore,
business uses will expand and expectations will rise based
on these higher performing systems. Consequently, service
providers and carriers will require that manufacturers
provide data communication products designed to minimize
downtime and the associated lost revenue. For example,
according to The Costs of Enterprise Downtime 2003 by
Infonetics Research1, San Jose, CA, a case study
of six large organizations across various industries shows
that these companies are losing up to $96,632 per hour of
network downtime. Or, if a financial network goes down, they
could lose several million dollars per minute. As a result,
future network systems that achieve anything less then
carrier class availability will become unacceptable, and
availability of these services will be an economic
necessity.
Carrier Class Availability
Carrier class availability depends on many factors,
including software, hardware, environment, equipment
operators and service-type. Users are now requiring a level
of availability performance from packet-switched
communications networks that matches the levels that have
continuously been provided on voice and private line or
"Carrier class" circuit switched networks. This availability
equates to service expectations as shown in Table 1
(Reference 2).
Today, many packet-switched systems have consistently
exceeded "Five Nines" availability and are on their way to
"Six Nines" as a way of defining carrier class availability.
Originally, the term "Six Nines" was used to measure
manufacturing defects. It is the number of times the number
9 appears when measuring defects as a percentage. For
example, communications networks currently operate at an
availability level that is greater than 10 DPM (Defects Per
Million, 99.999% availability or "Five Nines") and are
moving towards the "Six Nines" (99.9999%) level, or 1 DPM,
as newly designed communications equipment is integrated
into the network. In service terms, "Five Nines" means that
a web site is only unavailable, or "down" about five minutes
per year and "Six Nines" means it will be unavailable for
less then 31 seconds per year (Table 2). Whether this level
of availability is defined as 5-9s, 6-9s or "web-tone as
reliable as dial-tone", the goal is the same. If the network
goes down for any reason, it means lost revenue and unhappy
customers. The challenge is that the new routers, switches,
servers, base stations and other systems being designed now
to implement this new infrastructure require complex line
cards which all need proper power management and
environmental control.
|
