1. Timeout Interval Option Specification

   The TFTP Read Request or Write Request packet is modified to include
   the timeout option as follows:

      +-------+---~~---+---+---~~---+---+---~~---+---+---~~---+---+
      |  opc  |filename| 0 |  mode  | 0 | timeout| 0 |  #secs | 0 |
      +-------+---~~---+---+---~~---+---+---~~---+---+---~~---+---+

      opc
         The opcode field contains either a 1, for Read Requests, or 2,
         for Write Requests, as defined in [1].

      filename
         The name of the file to be read or written, as defined in [1].
         This is a NULL-terminated field.

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

      timeout
         The Timeout Interval option, "timeout" (case insensitive).
         This is a NULL-terminated field.

      #secs
         The number of seconds to wait before retransmitting, specified
         in ASCII.  Valid values range between "1" and "255" octets,
         inclusive.  This is a NULL-terminated field.

   For example:

      +-------+--------+---+--------+---+--------+---+--------+---+
      |   1   | foobar | 0 | binary | 0 | timeout| 0 |    1   | 0 |
      +-------+--------+---+--------+---+--------+---+--------+---+

   is a Read Request, for the file named "foobar", in binary transfer
   mode, with a timeout interval of 1 second.

   If the server is willing to accept the timeout option, it sends an
   Option Acknowledgment (OACK) to the client.  The specified timeout
   value must match the value specified by the client.