Table 3.1 (continued)
GUIDELINES AND
PRINCIPLES DESCRIPTION
The Myth of Five Nines The Internet can provide better than 99.999 percent
availability without depending on equipment with
“five nines” reliability.
DNS, for example, has never failed since its
introduction in 1986, though individual DNS servers
may have quite modest reliability.
The Internet has proven to provide better than PSTN
availability in all recent disasters in North America,
Europe, and Asia.
Outages are only partial and are mostly caused by
people or by disasters.
Simple Delivery Paths The quality of a path between users, or between
users and a service (server), is very sensitive to the
number and complexity of the elements in that
path.
Security is Enhanced by The simplicity principle is helpful for security, since
Simplicity security implications are easier to understand.You should compare the principles of the Internet architecture shown in
Table 3.1 with the telecom architectures exemplified with the IMS shown in
Figure 3.2. The differences are too many to be summarized by a simple bul-
leted list or table. Note the following, however:
■■ None of the Internet architecture documents referenced here have any
diagrams, although some Internet standards have some diagrams that
are simple enough to be drawn as stick drawings using simple text
symbols and lines.
■■ All Internet document authors are listed as individual contributors, and
many of them are well-known personalities from research and academia.
■■ Internet standards are driven by the desire for excellence in engineering
by its authors.
■■ Internet standards are not driven by marketing departments or by time-
to-market commercial interests, though the marketplace is considered
the ultimate arbiter for technology.Architectural Principles of the Internet 47