Every Telnet implementation MUST support the Binary option [TELNET:3] and the Suppress Go Ahead option [TELNET:5], and SHOULD support the Echo [TELNET:4], Status [TELNET:6], End-of- Record [TELNET:9], and Extended Options List [TELNET:8] options.
A User or Server Telnet SHOULD support the Window Size Option [TELNET:12] if the local operating system provides the corresponding capability.
Note that the End-of-Record option only signifies that a Telnet can receive a Telnet EOR without crashing; therefore, every Telnet ought to be willing to accept negotiation of the End-of-Record option. See also the discussion in Section 3.2.3.