Editing Keepalive (section)

==Keepalive on higher layers==

Since TCP keepalive is optional, various protocols (e.g.
SMB<ref>{{cite journal|url=https://tools.ietf.org/html/rfc1001#page-54|journal=IETF|title=Protocol Standard for a NetBIOS Service on a TCP/UDP Transport: Concepts and Methods|date=March 1987|doi=10.17487/RFC1001 |accessdate=June 18, 2015<!-- |last2=Board |first2=Internet Activities |last3=Force |first3=End-to-End Services Task --> |url-access=subscription}}</ref>
and TLS<ref>{{cite journal|url=https://tools.ietf.org/html/rfc6520|journal=IETF|title=Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS) Heartbeat Extension|date=February 2012|accessdate=June 18, 2015|last1=Williams|first1=Michael|last2=Tüxen|first2=Michael|last3=Seggelmann|first3=Robin|doi=10.17487/RFC6520 |url-access=subscription}}</ref>)
implement their own keep-alive feature on top of TCP. It is also common for protocols which maintain a session over a connectionless protocol, e.g. OpenVPN over UDP,<ref>{{cite web|url=https://community.openvpn.net/openvpn/wiki/Openvpn23ManPage|title=OpenVPN manual page|accessdate=June 18, 2015}}</ref> to implement their own keep-alive.