Tier 1 - Computer Definition
(1) See Tier 1 network.
(2) The top level. A Tier 1 city is one of the major metropolitan areas in a country. A Tier 1 vendor is one of the largest and most well-known in its field. However, the term can sometimes refer to the bottom level or first floor. For example, the U.S. government labeled Tier 1 Y2K compliance as the bottom level.