EXTENSIONS (FTP client and server) statement

Use the EXTENSIONS statement to enable FTP to support FTP extensions not described in RFC 959.

Parameters

AUTH_GSSAPI

Specifies that GSSAPI authentication is supported. The server supports receiving the AUTH command with GSSAPI. AUTH_GSSAPI is supported for IPv4 connections only.

Restriction: This parameter applies to the server only.

SIZE

Enables the FTP Server to respond to the SIZE command. SIZE is supported for z/OS® UNIX files only when the data transfer type is image, ASCII, or EBCDIC, the structure is file, and the data transfer mode is stream. If an FTP client requests MDTM or SIZE information for an MVS™ data set, or for any other unsupported file, the server returns an FTP reply code and error message instead of the requested information.

Restriction: This parameter applies to the server only.

MDTM

Enables the FTP Server to respond to the MDTM command. MDTM is supported for z/OS UNIX files only.

Restriction: This parameter applies to the server only.

UTF8

Enables the FTP server to respond to the LANG command, and to use UTF–8 encoding of pathnames on the control connection. The server ignores configuration options that direct it to use a specific code page on the control connection, as well as SITE commands that specify a specific code page on the control connection. The server initializes the control connection to use 7-bit ASCII until a LANG command from the client directs it to use UTF-8 encoding of pathnames. The only language supported by the server is United States English.

When the client has EXTENSIONS UTF8 encoded in FTP.DATA, the client has the language and subcommands available. Configuration options that direct the client to use a specific code page on the control connection, as well as LOCSITE commands that specify a specific code page on the control connection, are ignored. Initially the client uses 7-bit ASCII on the control connection. During client login, the client queries the server to determine whether it supports UTF-8 encoding. If so, it uses UTF-8 encoding of pathnames on the control connection.

Restriction: This parameter applies to both the client and the server.

REST_STREAM

Enables the FTP server to restart stream mode file transfers. The server ignores EXTENSIONS REST_STREAM unless EXTENSIONS SIZE is also coded, because stream restarts rely on the SIZE command.

Restriction: This parameter applies to the server only.

AUTH_TLS

Specifies that TLS authentication is supported. The server supports receiving the AUTH command with the following values:

• TLS: When the server successfully processes the AUTH TLS command and completes the handshake with the FTP client, the control connection is protected by TLS.
• TLS-C: When the server successfully processes the AUTH TLS-C command and completes the handshake with the FTP client, the control connection is protected by TLS.
• TLS-P: When the server successfully processes the AUTH TLS-P command and completes the handshake with the FTP client, the control connection is protected by TLS. The server also implicitly protects all data connections.
• SSL: When the server successfully processes the AUTH SSL command and completes the handshake with the FTP client, the control connection is protected by TLS.The server also implicitly protects all data connections.

Restriction: This parameter applies to the server only.

Results:

• This parameter also enables server support for the PROT and PBSZ commands.
• Server support for TLS-secured sessions is affected by the TLSRFCLEVEL setting.

Usage notes

• The EXTENSIONS statement has no default value.
• If you do not include an EXTENSIONS statement in FTP.DATA, no extensions to RFC 959 are recognized.
• Unlike other FTP.DATA statements, EXTENSIONS statements are cumulative. If you include an EXTENSIONS SIZE statement in FTP.DATA and also an EXTENSIONS MDTM statement, the FTP server receives both the SIZE and MDTM commands.
• The only way to disable an EXTENSIONS statement is to remove that statement from FTP.DATA. You can remove a statement by changing it to a comment or by deleting the statement.
• The SIZE and MDTM commands are not part of RFC 959. They are proposed commands described by an Internet-Draft published by the IETF (Internet Engineering Task Force). Because these commands are not part of an RFC, the FTP server supports them only if FTP.DATA includes EXTENSIONS statements to explicitly enable them.

Related topics

• TLSRFCLEVEL (FTP client and server) statement
• See z/OS Communications Server: IP Configuration Guide for more information about customizing TLS and Kerberos.