Appendix D. The Specification of Network Addresses

In the specification the following conventions are taken:

•variables (the fields to be substituted by concrete values) are enclosed in angle brackets and written in italic,

•permanent text (remains after substitutions) is written in bold,

•optional elements are enclosed in brackets,

•the defined notion is placed on the left of the ::= character string, and the definition is placed on the right (as in the Backus-Naur form).