Telnet Options

Last Updated: 2022-03-16
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Registries included below

Telnet Options

Registration Procedure(s)

IETF Review

Reference

[RFC855]

Note

The Telnet Protocol has a number of options that may be negotiated.
These options are listed here.  "Internet Official Protocol Standards"
(STD 1) provides more detailed information.

Available Formats

CSV

Options	Name	Reference
0	Binary Transmission	[RFC856]
1	Echo	[RFC857]
2	Reconnection	[NIC 15391 of 1973]
3	Suppress Go Ahead	[RFC858]
4	Approx Message Size Negotiation	[NIC 15393 of 1973]
5	Status	[RFC859]
6	Timing Mark	[RFC860]
7	Remote Controlled Trans and Echo	[RFC726]
8	Output Line Width	[NIC 20196 of August 1978]
9	Output Page Size	[NIC 20197 of August 1978]
10	Output Carriage-Return Disposition	[RFC652]
11	Output Horizontal Tab Stops	[RFC653]
12	Output Horizontal Tab Disposition	[RFC654]
13	Output Formfeed Disposition	[RFC655]
14	Output Vertical Tabstops	[RFC656]
15	Output Vertical Tab Disposition	[RFC657]
16	Output Linefeed Disposition	[RFC658]
17	Extended ASCII	[RFC698]
18	Logout	[RFC727]
19	Byte Macro	[RFC735]
20	Data Entry Terminal	[RFC1043][RFC732]
21	SUPDUP	[RFC736][RFC734]
22	SUPDUP Output	[RFC749]
23	Send Location	[RFC779]
24	Terminal Type	[RFC1091]
25	End of Record	[RFC885]
26	TACACS User Identification	[RFC927]
27	Output Marking	[RFC933]
28	Terminal Location Number	[RFC946]
29	Telnet 3270 Regime	[RFC1041]
30	X.3 PAD	[RFC1053]
31	Negotiate About Window Size	[RFC1073]
32	Terminal Speed	[RFC1079]
33	Remote Flow Control	[RFC1372]
34	Linemode	[RFC1184]
35	X Display Location	[RFC1096]
36	Environment Option	[RFC1408]
37	Authentication Option	[RFC2941]
38	Encryption Option	[RFC2946]
39	New Environment Option	[RFC1572]
40	TN3270E	[RFC2355]
41	XAUTH	[Rob_Earhart]
42	CHARSET	[RFC2066]
43	Telnet Remote Serial Port (RSP)	[Robert_Barnes]
44	Com Port Control Option	[RFC2217]
45	Telnet Suppress Local Echo	[Wirt_Atmar]
46	Telnet Start TLS	[Michael_Boe]
47	KERMIT	[RFC2840]
48	SEND-URL	[David_Croft]
49	FORWARD_X	[Jeffrey_Altman]
50-137	Unassigned	[IANA]
138	TELOPT PRAGMA LOGON	[Steve_McGregory]
139	TELOPT SSPI LOGON	[Steve_McGregory]
140	TELOPT PRAGMA HEARTBEAT	[Steve_McGregory]
141-254	Unassigned
255	Extended-Options-List	[RFC861]

Telnet Authentication Types (Option 37)

Registration Procedure(s)

First Come First Served

Reference

[RFC2941]

Command

Registration Procedure(s)

First Come First Served

Reference

[RFC2941]

Available Formats

CSV

Command	Description	Reference
0	IS	[RFC2941]
1	SEND	[RFC2941]
2	REPLY	[RFC2941]
3	NAME	[RFC2941]

Types

Registration Procedure(s)

First Come First Served

Reference

[RFC2941]

Available Formats

CSV

Type	Description	Reference
0	NULL	[RFC2941]
1	KERBEROS_V4	[RFC2941]
2	KERBEROS_V5	[RFC2942]
3	SPX	[RFC2941][1]
4	MINK	[RFC2941][1]
5	SRP	[RFC2944]
6	RSA (also used by SRA)	[RFC2941]
7	SSL	[RFC2941]
8-9	Unassigned	[IANA]
10	LOKI	[RFC2941][1]
11	SSA	[Steven_Schoch]
12	KEA_SJ	[RFC2951]
13	KEA_SJ_INTEG	[RFC2951]
14	DSS	[RFC2943]
15	NTLM	[Louis_Kahn][1]

KERBEROS_V4 Telnet Authentication Type (Type 1)

Registration Procedure(s)

First Come First Served

Reference

[RFC1411]

Available Formats

CSV

Suboption	Command	Reference
0	AUTH	[RFC1411]
1	REJECT	[RFC1411]
2	ACCEPT	[RFC1411]
3	CHALLENGE	[RFC1411]
4	RESPONSE	[RFC1411]
5	FORWARD	[Derrick_Brashear]
6	FORWARD-ACCEPT	[Derrick_Brashear]
7	FORWARD-REJECT	[Derrick_Brashear]
8	EXP	[Thomas_Wu]
9	PARAMS	[Thomas_Wu]

KERBEROS_V5 Telnet Authentication Type (Type 2)

Registration Procedure(s)

Specification Required

Expert(s)

Unassigned

Reference

[RFC2942]

Available Formats

CSV

Suboption	Command	Reference
0	AUTH	[RFC2942]
1	REJECT	[RFC2942]
2	ACCEPT	[RFC2942]
3	RESPONSE	[RFC2942]
4	FORWARD	[RFC2942]
5	FORWARD_ACCEPT	[RFC2942]
6	FORWARD-REJECT	[RFC2942]

SRP Telnet Authentication Type (Type 5)

Registration Procedure(s)

Specification Required

Expert(s)

Unassigned

Reference

[RFC2944]

Available Formats

CSV

Suboption	Command	Reference
0	AUTH	[RFC2944]
1	REJECT	[RFC2944]
2	ACCEPT	[RFC2944]
3	CHALLENGE	[RFC2944]
4	RESPONSE	[RFC2944]
5-7	Unassigned	[RFC2944]
8	EXP	[RFC2944]
9	PARAMS	[RFC2944]

KEA_SJ (Type 12) and KEA_SJ_INTEG (Type 13) Authentication Types

Registration Procedure(s)

Specification Required

Expert(s)

Unassigned

Reference

[RFC2951]

Available Formats

CSV

Suboption	Command	Reference
1	KEA_CERTA_RA	[RFC2951]
2	KEA_CERTB_RB_IVB_NONCEB	[RFC2951]
3	KEA_IVA_RESPONSEB_NONCEA	[RFC2951]
4	KEA_RESPONSEA	[RFC2951]

DSS Authentication Type (Type 14)

Registration Procedure(s)

Specification Required

Expert(s)

Unassigned

Reference

[RFC2943]

Available Formats

CSV

Suboption	Command	Reference
1	DSS_INITIALIZE	[RFC2943]
2	DSS_TOKENBA	[RFC2943]
3	DSS_CERTA_TOKENAB	[RFC2943]
4	DSS_CERTB_TOKENBA2	[RFC2943]

Telnet Encryption Types (Option 38)

Registration Procedure(s)

First Come First Served

Reference

[RFC2946]

Note

In the Telnet Encryption commands and types [RFC2946] there have been
various implementations in several widely distributed versions of
Telnet (e.g., at MIT, Stanford, and Columbia).  Originally, only two
encryption types were specified.  Additional encryption types have
been defined and are listed below.  Additions to the list are
registered by the IANA and documented here.

Command

Registration Procedure(s)

First Come First Served

Reference

[RFC2946]

Available Formats

CSV

Command	Description	Reference
0	IS	[RFC2946]
1	SUPPORT	[RFC2946]
2	REPLY	[RFC2946]
3	START	[RFC2946]
4	END	[RFC2946]
5	REQUEST-START	[RFC2946]
6	REQUEST-END	[RFC2946]
7	ENC_KEYID	[RFC2946]
8	DEC_KEYID	[RFC2946]

Types

Registration Procedure(s)

First Come First Served

Reference

[RFC2946]

Available Formats

CSV

Type	Description	Reference
0	NULL	[RFC2946]
1	DES_CFB64	[RFC2946]
2	DES_OFB64	[RFC2946]
3	DES3_CFB64	[RFC2946]
4	DES3_OFB64	[RFC2946]
5-7	Unassigned	[IANA]
8	CAST5_40_CFB64	[RFC2946]
9	CAST5_40_OFB64	[RFC2946]
10	CAST128_CFB64	[RFC2946]
11	CAST128_OFB64	[RFC2946]
12	AES_CCM	[S_Josefsson]

DES_CFB64 Telnet Encryption Type (Type 1)

Registration Procedure(s)

First Come First Served

Reference

[RFC2952]

Available Formats

CSV

Suboption	Command	Reference
1	CFB64_IV	[RFC2952]
2	CFB64_IV_OK	[RFC2952]
3	CFB64_IV_BAD	[RFC2952]

DES_OFB64 Telnet Encryption Type (Type 2)

Registration Procedure(s)

First Come First Served

Reference

[RFC2953]

Available Formats

CSV

Suboption	Command	Reference
1	OFB64_IV	[RFC2953]
2	OFB64_IV_OK	[RFC2953]
3	OFB64_IV_BAD	[RFC2953]

DES3_CFB64 Telnet Encryption Type (Type 3)

Registration Procedure(s)

First Come First Served

Reference

[RFC2947]

Available Formats

CSV

Suboption	Command	Reference
1	CFB64_IV	[RFC2947]
2	CFB64_IV_OK	[RFC2947]
3	CFB64_IV_BAD	[RFC2947]

DES3_OFB64 Telnet Encryption Type (Type 4)

Registration Procedure(s)

First Come First Served

Reference

[RFC2948]

Available Formats

CSV

Suboption	Command	Reference
1	OFB64_IV	[RFC2948]
2	OFB64_IV_OK	[RFC2948]
3	OFB64_IV_BAD	[RFC2948]

CAST5_40_CFB64 (Type 8) and CAST128_CFB64 (Type 10) Telnet Encryption Types

Registration Procedure(s)

First Come First Served

Reference

[RFC2950]

Available Formats

CSV

Suboption	Command	Reference
1	CFB64_IV	[RFC2950]
2	CFB64_IV_OK	[RFC2950]
3	CFB64_IV_BAD	[RFC2950]

CAST5_40_OFB64 (Type 9) and CAST128_OFB64 (Type 11) Telnet Encryption Types

Registration Procedure(s)

First Come First Served

Reference

[RFC2949]

Available Formats

CSV

Suboption	Command	Reference
1	OFB64_IV	[RFC2949]
2	OFB64_IV_OK	[RFC2949]
3	OFB64_IV_BAD	[RFC2949]

Contact Information

ID	Name	Contact URI	Last Updated
[David_Croft]	David Croft	mailto:david&infotrek.co.uk	1998-09
[Derrick_Brashear]	Derrick Brashear	mailto:shadow&dementia.org	1995-01
[IANA]	Internet Assigned Numbers Authority	mailto:iana&iana.org	2012-08
[Jeffrey_Altman]	Jeffrey Altman	mailto:jaltman&watsun.cc.columbia.edu	2000-01
[Louis_Kahn]	Louis Kahn	mailto:louisk&microsoft.com	1998-10
[Michael_Boe]	Michael Boe	mailto:mboe&cisco.com	1998-06
[Rob_Earhart]	Rob Earhart	mailto:earhart+&cmu.edu	1995-04
[Robert_Barnes]	Robert Barnes	mailto:rab&stallion.oz.au	1997-07
[S_Josefsson]	S. Josefsson	mailto:jas&extundo.com http://josefsson.org/shishi/shishi.html#Telnet%20encryption%20with%20AES-CCM	2003-11
[Steve_McGregory]	Steve McGregory	mailto:stevemc&pragmasys.com	1998-12
[Steven_Schoch]	Steven Schoch	mailto:schoch&sheba.arc.nasa.gov	1995-01
[Thomas_Wu]	Thomas Wu	mailto:tjw&stanford.edu	1998-09
[Wirt_Atmar]	Wirt Atmar	mailto:atmar&aics-research.com	1998-06

Footnote

[1]	Authentication types never submitted to the IETF for consideration as an Internet standard.

Telnet Options

Telnet Options

Telnet Authentication Types (Option 37)

Command

Types

KERBEROS_V4 Telnet Authentication Type (Type 1)

KERBEROS_V5 Telnet Authentication Type (Type 2)

SRP Telnet Authentication Type (Type 5)

KEA_SJ (Type 12) and KEA_SJ_INTEG (Type 13) Authentication Types

DSS Authentication Type (Type 14)

Telnet Encryption Types (Option 38)

Command

Types

DES_CFB64 Telnet Encryption Type (Type 1)

DES_OFB64 Telnet Encryption Type (Type 2)

DES3_CFB64 Telnet Encryption Type (Type 3)

DES3_OFB64 Telnet Encryption Type (Type 4)

CAST5_40_CFB64 (Type 8) and CAST128_CFB64 (Type 10) Telnet Encryption Types

CAST5_40_OFB64 (Type 9) and CAST128_OFB64 (Type 11) Telnet Encryption Types

Contact Information

Footnote

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