%% You should probably cite rfc6520 instead of this I-D.
@techreport{ietf-tls-dtls-heartbeat-04,
    number =    {draft-ietf-tls-dtls-heartbeat-04},
    type =      {Internet-Draft},
    institution =   {Internet Engineering Task Force},
    publisher = {Internet Engineering Task Force},
    note =      {Work in Progress},
    url =       {https://datatracker.ietf.org/doc/draft-ietf-tls-dtls-heartbeat/04/},
    author =    {Michael Williams and Michael Tüxen and Robin Seggelmann},
    title =     {{Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS) Heartbeat Extension}},
    pagetotal = 9,
    year =      2011,
    month =     dec,
    day =       2,
    abstract =  {This document describes the Heartbeat Extension for the Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS) protocols. The Heartbeat Extension provides a new protocol for TLS/DTLS allowing the usage of keep-alive functionality without performing a renegotiation and a basis for path MTU (PMTU) discovery for DTLS. {[}STANDARDS-TRACK{]}},
}