A sequentially assigned number to identify a command within a VNAC agent.
cmd-number is an alias to cmd-id and resolves to the same value.
In many VNAC messages, an individual command is uniquely identified by the concatenation #sess-number.cmd-index.cmd-number.
Other messages use the variable full-cmd-id, which concatenates sess-number.cmd-index.cmd-id and resolves to an identical value.