RFC 1783 (rfc1783) - Page 2 of 5

TFTP Blocksize Option

RFC 1783                 TFTP Blocksize Option                March 1995


      mode
         The mode of the file transfer: "netascii", "octet", or "mail",
         as defined in [1].  This is a NULL-terminated field.

      blksize
         The Blocksize option, "blksize" (case insensitive).  This is a
         NULL-terminated field.

      #octets
         The number of octets in a block, specified in ASCII.  Valid
         values range between "8" and "65464" octets, inclusive.  This
         is a NULL-terminated field.

   For example:

      +-------+--------+---+--------+---+--------+---+--------+---+
      |   1   | foobar | 0 | binary | 0 | blksize| 0 |  1432  | 0 |
      +-------+--------+---+--------+---+--------+---+--------+---+

   is a Read Request, for the file named "foobar", in binary transfer
   mode, with a block size of 1432 bytes (Ethernet MTU, less the UDP and
   IP header lengths).

   If the server is willing to accept the blocksize option, it sends an
   Option Acknowledgment (OACK) to the client.  The specified value must
   be less than or equal to the value specified by the client.  The
   client must then either use the size specified in the OACK, or send
   an ERROR packet, with error code 8, to terminate the transfer.

   The rules for determining the final packet are unchanged from [1].
   The reception of a data packet with a data length less than the
   negotiated blocksize is the final packet.  If the blocksize is
   greater than the size of the packet, the first packet is the final
   packet.  If amount of data to be transfered is an integral multiple
   of the blocksize, an extra data packet containing no data is sent to
   end the transfer.















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