RFC 2348 (rfc2348) - Page 2 of 5
TFTP Blocksize Option
Alternative Format: Original Text Document
RFC 2348 TFTP Blocksize Option May 1998
filename
The name of the file to be read or written, as defined in [1].
mode
The mode of the file transfer: "netascii", "octet", or "mail",
as defined in [1].
blksize
The Blocksize option, "blksize" (case in-sensitive).
#octets
The number of octets in a block, specified in ASCII. Valid
values range between "8" and "65464" octets, inclusive. The
blocksize refers to the number of data octets; it does not
include the four octets of TFTP header.
For example:
+-------+--------+---+--------+---+--------+---+--------+---+
| 1 | foobar | 0 | octet | 0 | blksize| 0 | 1428 | 0 |
+-------+--------+---+--------+---+--------+---+--------+---+
is a Read Request, for the file named "foobar", in octet (binary)
transfer mode, with a block size of 1428 octets (Ethernet MTU, less
the TFTP, 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 amount of data to be transfered, the first packet is
the final packet. If the 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.
Proof of Concept
Performance tests were run on the prototype implementation using a
variety of block sizes. The tests were run on a lightly loaded
Ethernet, between two HP-UX 9000, in "octet" mode, on 2.25MB files.
The average (5x) transfer times for paths with (g-time) and without
(n-time) a intermediate gateway are graphed as follows:
Malkin & Harkin Standards Track