Browse Prior Art Database

DHCPv6 Prefix-Length Hint Issues (RFC8168) Disclosure Number: IPCOM000250105D
Original Publication Date: 2017-May-01
Included in the Prior Art Database: 2017-Jun-01
Document File: 18 page(s) / 22K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

T. Li: AUTHOR [+3]


DHCPv6 Prefix Delegation [RFC3633] allows a client to include a prefix-length hint value in the message sent to the server to indicate a preference for the size of the prefix to be delegated. A prefix-length hint is communicated by a client to the server by including an IA_PD Prefix Option (IAPREFIX option), encapsulated in an IA_PD option, with the "IPv6 prefix" field set to zero and the "prefix-length" field set to a non-zero value. The servers are free to ignore the prefix-length hint values depending on server policy. However, some clients may not be able to function (or only in a degraded state) when they're provided with a prefix whose length is different from what they requested. For example, if the client is asking for a /56 and the server returns a /64, the functionality of the client might be limited because it might not be able to split the prefix for all its interfaces. For other hints, such as requesting for an explicit address, this might be less critical, as it just helps a client that wishes to continue using what it used last time. The prefix-length hint directly impacts the operational capability of the client; thus, it should be given more consideration.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 13% of the total text.

Internet Engineering Task Force (IETF)                             T. Li Request for Comments: 8168                                        C. Liu Category: Standards Track                                         Y. Cui ISSN: 2070-1721                                      Tsinghua University                                                                 May 2017

                     DHCPv6 Prefix-Length Hint Issues


   DHCPv6 Prefix Delegation allows a client to include a prefix-length    hint value in the IA_PD option to indicate a preference for the size    of the prefix to be delegated, but it is unclear about how the client    and server should act in different situations involving the prefix-    length hint.  This document provides a summary of the existing    problems with the prefix-length hint and guidance on what the client    and server could do in different situations.

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 7841.

   Information about the current status of this document, any errata,    and how to provide feedback on it may be obtained at

Copyright Notice

   Copyright (c) 2017 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    ( 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.

 Li, et al.                   Standards Track                    [Page 1]
 RFC 8168            DHCPv6 Prefix-Length Hint Issues            May 2017

 Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2

   2.  Requirements Language . . . . . . . . . . . . . . . . . . . .   3

   3.  Problem Description and Proposed Solutions  . . . . . . . . .   3

     3.1.  Creation of Solicit Message . . ....