There are two independent categorization of protocols. The first is the "maturity level" or STATE of standardization, one of "standard", "draft standard", "proposed standard", "experimental", "informational" or "historic". The second is the "requirement level" or STATUS of this protocol, one of "required", "recommended", "elective", "limited use", or "not recommended".
The status or requirement level is difficult to portray in a one word label. These status labels should be considered only as an indication, and a further description, or applicability statement, should be consulted.
When a protocol is advanced to proposed standard or draft standard, it is labeled with a current status.
At any given time a protocol occupies a cell of the following matrix. Protocols are likely to be in cells in about the following proportions (indicated by the relative number of Xs). A new protocol is most likely to start in the (proposed standard, elective) cell, or the (experimental, limited use) cell.
S T A T U S
Req Rec Ele Lim Not
+-----+-----+-----+-----+-----+
Std | X | XXX | XXX | | |
S +-----+-----+-----+-----+-----+
Draft | X | X | XXX | | |
T +-----+-----+-----+-----+-----+
Prop | | X | XXX | | |
A +-----+-----+-----+-----+-----+
Info | | | | | |
T +-----+-----+-----+-----+-----+
Expr | | | | XXX | |
E +-----+-----+-----+-----+-----+
Hist | | | | | XXX |
+-----+-----+-----+-----+-----+
What is a "system"?
Some protocols are particular to hosts and some to gateways; a few
protocols are used in both. The definitions of the terms below
will refer to a "system" which is either a host or a gateway (or
both). It should be clear from the context of the particular
protocol which types of systems are intended.