TFTP Server Address Option for DHCPv4
RFC 5859

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Internet Engineering Task Force (IETF)                        R. Johnson
Request for Comments: 5859                           Cisco Systems, Inc.
Category: Informational                                        June 2010
ISSN: 2070-1721

                 TFTP Server Address Option for DHCPv4

Abstract

   This memo documents existing usage for the "TFTP Server Address"
   option.  The option number currently in use is 150.  This memo
   documents the current usage of the option in agreement with RFC 3942,
   which declares that any pre-existing usages of option numbers in the
   range 128-223 should be documented, and the Dynamic Host
   Configuration working group will try to officially assign those
   numbers to those options.  The option is defined for DHCPv4 and works
   only with IPv4 addresses.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   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).  Not all documents
   approved by the IESG are a candidate for any level of Internet
   Standard; see 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/rfc5859.

Johnson                       Informational                     [Page 1]
RFC 5859                   TFTP Server Address                 June 2010

Copyright Notice

   Copyright (c) 2010 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   than English.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . 3
   3.  TFTP Server Address Option Definition . . . . . . . . . . . . . 4
   4.  Security Considerations . . . . . . . . . . . . . . . . . . . . 5
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 5
     6.1.  Normative References  . . . . . . . . . . . . . . . . . . . 5
     6.2.  Informative References  . . . . . . . . . . . . . . . . . . 6

Johnson                       Informational                     [Page 2]
RFC 5859                   TFTP Server Address                 June 2010

1.  Introduction

   Voice over IP (VoIP) devices, such as IP phones, have a need to
   download their configuration from a configuration server on the
   network.  There are two commonly accepted methods to discover this
   server via DHCP; the "sname" field in the DHCP header [RFC2131] and
   the "TFTP Server Name" option (66) [RFC2132].  Both of these sources
   of information, however, contain the TFTP server's hostname.  That
   hostname must then be translated to an IP address.  The usual method
   to accomplish this would be DNS [RFC1034].  This means the firmware
   in a VoIP device (with possibly limited flash, memory, and/or
   processing resources) would need to implement the DNS protocol in
   order to perform this translation.  This would also introduce an
   additional unnecessary point of failure whereby the device is
   dependent on the DNS server infrastructure in order to boot up and
   communicate with its call agent.

   In order to eliminate DNS as a point of failure and to keep the
   firmware in such a VoIP device to a minimum, the "VoIP Configuration
   Server Address" option (150) was introduced.  This option allows the