“Production software begins its life in a testing or research
environment. These environments sometimes consist of actual labs on
a private network, isolated from the rest of the environment in
almost every way (partly as a security measure). Inside the lab are
machines that act as representative parts of the production network
environment. For example, there may be a machine running Apache,
MySQL, DNS, and NTP; another machine on the other side of a router
running sendmail and an ‘internal’ DNS server. There will be client
machines, of course, and printers, wireless access points, and
NIS/NIS+/LDAP servers, which may be acting upon live data…”