Telnet Options
2022-03-16
Telnet Options
IETF Review
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.
0
Binary Transmission
1
Echo
2
Reconnection
NIC 15391 of 1973
3
Suppress Go Ahead
4
Approx Message Size Negotiation
NIC 15393 of 1973
5
Status
6
Timing Mark
7
Remote Controlled Trans and Echo
8
Output Line Width
NIC 20196 of August 1978
9
Output Page Size
NIC 20197 of August 1978
10
Output Carriage-Return Disposition
11
Output Horizontal Tab Stops
12
Output Horizontal Tab Disposition
13
Output Formfeed Disposition
14
Output Vertical Tabstops
15
Output Vertical Tab Disposition
16
Output Linefeed Disposition
17
Extended ASCII
18
Logout
19
Byte Macro
20
Data Entry Terminal
21
SUPDUP
22
SUPDUP Output
23
Send Location
24
Terminal Type
25
End of Record
26
TACACS User Identification
27
Output Marking
28
Terminal Location Number
29
Telnet 3270 Regime
30
X.3 PAD
31
Negotiate About Window Size
32
Terminal Speed
33
Remote Flow Control
34
Linemode
35
X Display Location
36
Environment Option
37
Authentication Option
38
Encryption Option
39
New Environment Option
40
TN3270E
41
XAUTH
42
CHARSET
43
Telnet Remote Serial Port (RSP)
44
Com Port Control Option
45
Telnet Suppress Local Echo
46
Telnet Start TLS
47
KERMIT
48
SEND-URL
49
FORWARD_X
50-137
Unassigned
138
TELOPT PRAGMA LOGON
139
TELOPT SSPI LOGON
140
TELOPT PRAGMA HEARTBEAT
141-254
Unassigned
255
Extended-Options-List
Telnet Authentication Types (Option 37)
First Come First Served
Command
First Come First Served
0
IS
1
SEND
2
REPLY
3
NAME
Types
First Come First Served
0
NULL
1
KERBEROS_V4
2
KERBEROS_V5
3
SPX
4
MINK
5
SRP
6
RSA (also used by SRA)
7
SSL
8-9
Unassigned
10
LOKI
11
SSA
12
KEA_SJ
13
KEA_SJ_INTEG
14
DSS
15
NTLM
Authentication types never submitted to the IETF for consideration as an Internet standard.
KERBEROS_V4 Telnet Authentication Type (Type 1)
First Come First Served
0
AUTH
1
REJECT
2
ACCEPT
3
CHALLENGE
4
RESPONSE
5
FORWARD
6
FORWARD-ACCEPT
7
FORWARD-REJECT
8
EXP
9
PARAMS
KERBEROS_V5 Telnet Authentication Type (Type 2)
Specification Required
Unassigned
0
AUTH
1
REJECT
2
ACCEPT
3
RESPONSE
4
FORWARD
5
FORWARD_ACCEPT
6
FORWARD-REJECT
SRP Telnet Authentication Type (Type 5)
Specification Required
Unassigned
0
AUTH
1
REJECT
2
ACCEPT
3
CHALLENGE
4
RESPONSE
5-7
Unassigned
8
EXP
9
PARAMS
KEA_SJ (Type 12) and KEA_SJ_INTEG (Type 13) Authentication Types
Specification Required
Unassigned
1
KEA_CERTA_RA
2
KEA_CERTB_RB_IVB_NONCEB
3
KEA_IVA_RESPONSEB_NONCEA
4
KEA_RESPONSEA
DSS Authentication Type (Type 14)
Specification Required
Unassigned
1
DSS_INITIALIZE
2
DSS_TOKENBA
3
DSS_CERTA_TOKENAB
4
DSS_CERTB_TOKENBA2
Telnet Encryption Types (Option 38)
First Come First Served
In the Telnet Encryption commands and types 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
First Come First Served
0
IS
1
SUPPORT
2
REPLY
3
START
4
END
5
REQUEST-START
6
REQUEST-END
7
ENC_KEYID
8
DEC_KEYID
Types
First Come First Served
0
NULL
1
DES_CFB64
2
DES_OFB64
3
DES3_CFB64
4
DES3_OFB64
5-7
Unassigned
8
CAST5_40_CFB64
9
CAST5_40_OFB64
10
CAST128_CFB64
11
CAST128_OFB64
12
AES_CCM
DES_CFB64 Telnet Encryption Type (Type 1)
First Come First Served
1
CFB64_IV
2
CFB64_IV_OK
3
CFB64_IV_BAD
DES_OFB64 Telnet Encryption Type (Type 2)
First Come First Served
1
OFB64_IV
2
OFB64_IV_OK
3
OFB64_IV_BAD
DES3_CFB64 Telnet Encryption Type (Type 3)
First Come First Served
1
CFB64_IV
2
CFB64_IV_OK
3
CFB64_IV_BAD
DES3_OFB64 Telnet Encryption Type (Type 4)
First Come First Served
1
OFB64_IV
2
OFB64_IV_OK
3
OFB64_IV_BAD
CAST5_40_CFB64 (Type 8) and CAST128_CFB64 (Type 10) Telnet Encryption Types
First Come First Served
1
CFB64_IV
2
CFB64_IV_OK
3
CFB64_IV_BAD
CAST5_40_OFB64 (Type 9) and CAST128_OFB64 (Type 11) Telnet Encryption Types
First Come First Served
1
OFB64_IV
2
OFB64_IV_OK
3
OFB64_IV_BAD
David Croft
mailto:david&infotrek.co.uk
1998-09
Derrick Brashear
mailto:shadow&dementia.org
1995-01
Internet Assigned Numbers Authority
mailto:iana&iana.org
2012-08
Jeffrey Altman
mailto:jaltman&watsun.cc.columbia.edu
2000-01
Louis Kahn
mailto:louiskµsoft.com
1998-10
Michael Boe
mailto:mboe&cisco.com
1998-06
Rob Earhart
mailto:earhart+&cmu.edu
1995-04
Robert Barnes
mailto:rab&stallion.oz.au
1997-07
S. Josefsson
mailto:jas&extundo.com
http://josefsson.org/shishi/shishi.html#Telnet%20encryption%20with%20AES-CCM
2003-11
Steve McGregory
mailto:stevemc&pragmasys.com
1998-12
Steven Schoch
mailto:schoch&sheba.arc.nasa.gov
1995-01
Thomas Wu
mailto:tjw&stanford.edu
1998-09
Wirt Atmar
mailto:atmar&aics-research.com
1998-06