Port Control Protocol (PCP) Anycast Addresses
RFC 7723

Document Type RFC - Proposed Standard (January 2016; No errata)
Last updated 2016-01-22
Replaces draft-kiesel-pcp-ip-based-srv-disc, draft-cheshire-pcp-anycast
Stream IETF
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Stream WG state Submitted to IESG for Publication
Document shepherd Dave Thaler
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IESG IESG state RFC 7723 (Proposed Standard)
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Responsible AD Brian Haberman
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IANA IANA review state Version Changed - Review Needed
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Internet Engineering Task Force (IETF)                         S. Kiesel
Request for Comments: 7723                       University of Stuttgart
Category: Standards Track                                       R. Penno
ISSN: 2070-1721                                      Cisco Systems, Inc.
                                                            January 2016

             Port Control Protocol (PCP) Anycast Addresses

Abstract

   The Port Control Protocol (PCP) anycast addresses enable PCP clients
   to transmit signaling messages to their closest PCP-aware on-path
   NAT, firewall, or other middlebox without having to learn the IP
   address of that middlebox via some external channel.  This document
   establishes one well-known IPv4 address and one well-known IPv6
   address to be used as PCP anycast addresses.

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/rfc7723.

Copyright Notice

   Copyright (c) 2016 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.

Kiesel & Penno               Standards Track                    [Page 1]
RFC 7723                  PCP Anycast Addresses             January 2016

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  PCP Server Discovery Based on Well-Known IP Address . . . . .   3
     2.1.  PCP Discovery Client Behavior . . . . . . . . . . . . . .   3
     2.2.  PCP Discovery Server Behavior . . . . . . . . . . . . . .   3
   3.  Deployment Considerations . . . . . . . . . . . . . . . . . .   4
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
     4.1.  Registration of an IPv4 Special-Purpose Address . . . . .   5
     4.2.  Registration of an IPv6 Special-Purpose Address . . . . .   5
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
     5.1.  Information Leakage through Anycast . . . . . . . . . . .   6
     5.2.  Hijacking of PCP Messages Sent to Anycast Addresses . . .   6
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   7
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   7
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   The Port Control Protocol (PCP) [RFC6887] provides a mechanism to
   control how incoming packets are forwarded by upstream devices such
   as Network Address and Protocol Translation from IPv6 Clients to IPv4
   Servers (NAT64), Network Address Translation from IPv4 to IPv4
   (NAT44), and IPv6 and IPv4 firewall devices.  Furthermore, it
   provides a mechanism to reduce application keepalive traffic
   [PCP-OPTIMIZE].  The PCP base protocol document [RFC6887] specifies
   the message formats used, but the address to which a client sends its
   request is either assumed to be the default router (which is
   appropriate in a typical single-link residential network) or has to
   be configured otherwise via some external mechanism, such as a
   configuration file or a DHCP option [RFC7291].

   This document follows a different approach: it establishes two well-
   known anycast addresses for the PCP server, one IPv4 address and one
   IPv6 address.  PCP clients usually send PCP requests to these well-
   known addresses if no other PCP server addresses are known or after
   communication attempts to such other addresses have failed.  The
   anycast addresses are allocated from pools of special-purpose IP
   addresses (see Section 4), in accordance with Section 3.4 of
   [RFC4085].  Yet, a means to disable or override these well-known
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