6 Appendix A: Product Behavior
The information in this specification is applicable to the following Microsoft products or supplemental software. References to product versions include updates to those products.
Windows 2000 operating system
Windows XP operating system
Windows Server 2003 operating system
Windows Vista operating system
Windows Home Server server software
Windows Server 2008 operating system
Windows 7 operating system
Windows Server 2008 R2 operating system
Windows 8 operating system
Windows Server 2012 operating system
Windows 8.1 operating system
Windows Server 2012 R2 operating system
Windows 10 operating system
Windows Server 2016 operating system
Windows Server operating system
Windows Server 2019 operating system
Windows Server 2022 operating system
Windows 11 operating system
Windows Server 2025 operating system
Exceptions, if any, are noted in this section. If an update version, service pack or Knowledge Base (KB) number appears with a product name, the behavior changed in that update. The new behavior also applies to subsequent updates unless otherwise specified. If a product edition appears with the product version, behavior is different in that product edition.
Unless otherwise specified, any statement of optional behavior in this specification that is prescribed using the terms "SHOULD" or "SHOULD NOT" implies product behavior in accordance with the SHOULD or SHOULD NOT prescription. Unless otherwise specified, the term "MAY" implies that the product does not follow the prescription.
<1> Section 1.5: Windows Telnet server and Telnet client use Security Support Provider Interface (SSPI) to obtain and process NTLM messages. For more information about SSPI, see [SSPI].
<2> Section 2.2.2: Though the Telnet: NTLM Authentication Protocol does not specify why or how the NTLM_BufferType field is processed, Microsoft Windows Telnet server and client use the value of this field to fill the BufferType field of the SecBuffer structure. For more information on BufferType and the SecBuffer structure, see [SSPI]. The value 0x00000002 corresponds to SECBUFFER_TOKEN buffer type. The Microsoft Windows Telnet client and Telnet server implementations set the NTLM_BufferType field to 0x00000002.
<3> Section 3.1.5.2: When a Microsoft Windows Telnet client encounters this error condition, it sends an IS command message with the AuthenticationType field set to 0x00, which corresponds to AuthenticationType NULL. Such an IS packet indicates to the server that Telnet Authentication Option (as specified in [RFC2941]) cannot be used.
<4> Section 3.1.5.3.1.1: When the Microsoft Windows Telnet client encounters this error condition, it ignores the message packet and takes no action.
<5> Section 3.1.5.3.1.2: When the Microsoft Windows Telnet client encounters this error condition, it sends an IS packet with the AuthenticationType field set to 0x00, which corresponds to AuthenticationType NULL. This IS packet indicates to the server that the Telnet Authentication Option cannot be used.
<6> Section 3.1.5.3.2: When the Microsoft Windows Telnet client encounters this error condition, it processes the message as it would if the message arrived in proper sequence.
<7> Section 3.1.5.3.3: The Microsoft Windows Telnet server follows the REPLY command [NTLM_CommandCode = NTLM_REJECT] with Telnet data that contains a string describing the reason for NTLM authentication failure followed by a string for password authentication. Details about how to handle Telnet data are specified in [RFC854].
<8> Section 3.1.5.3.3: When the Microsoft Windows Telnet client encounters this error condition, it processes the message as it would if the message arrived in proper sequence.