[BCP104]   Best Current Practice 104,
              <https://www.rfc-editor.org/info/bcp104>.
              At the time of writing, this BCP comprises the following:

              Klensin, J., "Terminology for Describing Internet
              Connectivity", BCP 104, RFC 4084, DOI 10.17487/RFC4084,
              May 2005, <https://www.rfc-editor.org/info/rfc4084>.