Internet Standard
When an Internet Standard is updated, its STD number stays the same, now referring to a new RFC or set of RFCs. A given Internet Standard, STD "n", may be RFCs "x" and "y" at a given time, but later the same standard may be updated to be RFC "z" instead. For example, in 2007 RFC 3700 was an Internet Standard—STD 1—and in May 2008 it was replaced with RFC 5000, so RFC 3700 changed to "Historic", RFC 5000 became an Internet Standard, and STD 1 is RFC 5000. RFC 5000 is replaced by RFC 7100, updating RFC 2026 to no longer use STD 1.