[BCP69]    Best Current Practice 69,
              <https://www.rfc-editor.org/info/bcp69>.
              At the time of writing, this BCP comprises the following:

              Balakrishnan, H., Padmanabhan, V., Fairhurst, G., and M.
              Sooriyabandara, "TCP Performance Implications of Network
              Path Asymmetry", BCP 69, RFC 3449, DOI 10.17487/RFC3449,
              December 2002, <https://www.rfc-editor.org/info/rfc3449>.