@misc{rfc9170,
    series =    {Request for Comments},
    number =    9170,
    howpublished =  {RFC 9170},
    publisher = {RFC Editor},
    doi =       {10.17487/RFC9170},
    url =       {https://www.rfc-editor.org/info/rfc9170},
    author =    {Martin Thomson and Tommy Pauly},
    title =     {{Long-Term Viability of Protocol Extension Mechanisms}},
    pagetotal = 17,
    year =      2021,
    month =     dec,
    abstract =  {The ability to change protocols depends on exercising the extension and version-negotiation mechanisms that support change. This document explores how regular use of new protocol features can ensure that it remains possible to deploy changes to a protocol. Examples are given where lack of use caused changes to be more difficult or costly.},
}