TFTP Windowsize Option
RFC 7440

Document Type RFC - Proposed Standard (January 2015; No errata)
Last updated 2015-10-14
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Internet Engineering Task Force (IETF)                        P. Masotta
Request for Comments: 7440                                         Serva
Category: Standards Track                                   January 2015
ISSN: 2070-1721

                         TFTP Windowsize Option

Abstract

   The "Trivial File Transfer Protocol" (RFC 1350) is a simple,
   lockstep, file transfer protocol that allows a client to get or put a
   file onto a remote host.  One of its primary uses is in the early
   stages of nodes booting from a Local Area Network (LAN).  TFTP has
   been used for this application because it is very simple to
   implement.  The employment of a lockstep scheme limits throughput
   when used on a LAN.

   This document describes a TFTP option that allows the client and
   server to negotiate a window size of consecutive blocks to send as an
   alternative for replacing the single-block lockstep schema.  The TFTP
   option mechanism employed is described in "TFTP Option Extension"
   (RFC 2347).

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc7440.

Masotta                      Standards Track                    [Page 1]
RFC 7440                 TFTP Windowsize Option             January 2015

Copyright Notice

   Copyright (c) 2015 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1. Introduction ....................................................2
   2. Conventions Used in This Document ...............................3
   3. Windowsize Option Specification .................................3
   4. Traffic Flow and Error Handling .................................4
   5. Proof of Concept and Windowsize Evaluation ......................6
   6. Congestion and Error Control ....................................7
   7. Security Considerations .........................................8
   8. References ......................................................9
      8.1. Normative References .......................................9
   Author's Address ...................................................9

1.  Introduction

   TFTP is virtually unused for Internet transfers today, TFTP is still
   massively used in network boot/installation scenarios including EFI
   (Extensible Firmware Interface).  TFTP's inherently low transfer rate
   has been, so far, partially mitigated by the use of the blocksize
   negotiated extension [RFC2348].  Using this method, the original
   limitation of 512-byte blocks are, in practice, replaced in Ethernet
   environments by blocks no larger than 1468 Bytes to avoid IP block
   fragmentation.  This strategy produces insufficient results when
   transferring big files, for example, the initial ramdisk of Linux
   distributions or the PE images used in network installations by
   Microsoft WDS/MDT/SCCM.  Considering TFTP looks far from extinction
   today, this document presents a negotiated extension, under the terms
   of the "TFTP Option Extension" [RFC2347], that produces TFTP transfer
   rates comparable to those achieved by modern file transfer protocols.

Masotta                      Standards Track                    [Page 2]
RFC 7440                 TFTP Windowsize Option             January 2015

2.  Conventions Used in This Document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
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