not, and that if the data is retrieved once, it is
          never needed again.  If PERMISSION is "read-write",




 
RFC 2046                      Media Types                  November 1996


          this assumption is invalid, and any local copy must be
          considered no more than a cache.  "Read" and "Read-
          write" are the only defined values of permission.  This
          parameter may be used with ANY access-type and is
          ALWAYS optional.

   The precise semantics of the access-types defined here are described
   in the sections that follow.

5.2.3.2.  The 'ftp' and 'tftp' Access-Types

   An access-type of FTP or TFTP indicates that the message body is
   accessible as a file using the FTP [RFC-959] or TFTP [RFC- 783]
   protocols, respectively.  For these access-types, the following
   additional parameters are mandatory:

    (1)   NAME -- The name of the file that contains the actual
          body data.

    (2)   SITE -- A machine from which the file may be obtained,
          using the given protocol.  This must be a fully
          qualified domain name, not a nickname.

    (3)   Before any data are retrieved, using FTP, the user will
          generally need to be asked to provide a login id and a
          password for the machine named by the site parameter.
          For security reasons, such an id and password are not
          specified as content-type parameters, but must be
          obtained from the user.

   In addition, the following parameters are optional:

    (1)   DIRECTORY -- A directory from which the data named by
          NAME should be retrieved.

    (2)   MODE -- A case-insensitive string indicating the mode
          to be used when retrieving the information.  The valid
          values for access-type "TFTP" are "NETASCII", "OCTET",
          and "MAIL", as specified by the TFTP protocol [RFC-
          783].  The valid values for access-type "FTP" are
          "ASCII", "EBCDIC", "IMAGE", and "LOCALn" where "n" is a
          decimal integer, typically 8.  These correspond to the
          representation types "A" "E" "I" and "L n" as specified
          by the FTP protocol [RFC-959].  Note that "BINARY" and
          "TENEX" are not valid values for MODE and that "OCTET"
          or "IMAGE" or "LOCAL8" should be used instead.  IF MODE
          is not specified, the  default value is "NETASCII" for
          TFTP and "ASCII" otherwise.




 
RFC 2046                      Media Types                  November 1996


5.2.3.3.  The 'anon-ftp' Access-Type

   The "anon-ftp" access-type is identical to the "ftp" access type,
   except that the user need not be asked to provide a name and password
   for the specified site.  Instead, the ftp protocol will be used with
   login "anonymous" and a password that corresponds to the user's mail
   address.

5.2.3.4.  The 'local-file' Access-Type

   An access-type of "local-file" indicates that the actual body is
   accessible as a file on the local machine.  Two additional parameters
   are defined for this access type:

    (1)   NAME -- The name of the file that contains the actual
          body data.  This parameter is mandatory for the
          "local-file" access-type.

    (2)   SITE -- A domain specifier for a machine or set of
          machines that are known to have access to the data
          file.  This optional parameter is used to describe the
          locality of reference for the data, that is, the site
          or sites at which the file is expected to be visible.
          Asterisks may be used for wildcard matching to a part
          of a domain name, such as "*.bellcore.com", to indicate
          a set of machines on which the data should be directly
          visible, while a single asterisk may be used to
          indicate a file that is expected to be universally
          available, e.g., via a global file system.

5.2.3.5.  The 'mail-server' Access-Type

   The "mail-server" access-type indicates that the actual body is
   available from a mail server.  Two additional parameters are defined