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Versions: (draft-bpw-pcp-dhcp) 00 01 02 03 04 05 06 07 08 09 10 11 12 13

PCP Working Group                                           M. Boucadair
Internet-Draft                                            France Telecom
Intended status: Standards Track                                R. Penno
Expires: September 28, 2013                                      D. Wing
                                                                   Cisco
                                                          March 27, 2013


            DHCP Options for the Port Control Protocol (PCP)
                         draft-ietf-pcp-dhcp-07

Abstract

   This document specifies DHCP (IPv4 and IPv6) options to configure
   hosts with Port Control Protocol (PCP) Server names.  The use of
   DHCPv4 or DHCPv6 depends on the PCP deployment scenario.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on September 28, 2013.

Copyright Notice

   Copyright (c) 2013 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



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   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.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  DHCPv6 PCP Server Option  . . . . . . . . . . . . . . . . . .   3
     3.1.  Format  . . . . . . . . . . . . . . . . . . . . . . . . .   3
     3.2.  Client Behavior . . . . . . . . . . . . . . . . . . . . .   4
   4.  DHCPv4 PCP Option . . . . . . . . . . . . . . . . . . . . . .   4
     4.1.  Format  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     4.2.  Client Behavior . . . . . . . . . . . . . . . . . . . . .   5
   5.  Use of PCP Server Names . . . . . . . . . . . . . . . . . . .   5
   6.  Dual-Stack Hosts  . . . . . . . . . . . . . . . . . . . . . .   5
   7.  Guidance to Administrators  . . . . . . . . . . . . . . . . .   5
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
     9.1.  DHCPv6 Option . . . . . . . . . . . . . . . . . . . . . .   6
     9.2.  DHCPv4 Option . . . . . . . . . . . . . . . . . . . . . .   6
   10. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   6
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     11.1.  Normative References . . . . . . . . . . . . . . . . . .   7
     11.2.  Informative References . . . . . . . . . . . . . . . . .   7
   Appendix A.  Rationale  . . . . . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   This document defines DHCPv4 [RFC2131] and DHCPv6 [RFC3315] options
   which can be used to provision PCP Server [I-D.ietf-pcp-base] names.
   Motivations for not expressing the PCP option as a 32 or 128-bit
   binary address are discussed in Appendix A.

   In order to make use of these options, this document assumes
   appropriate name resolution means (e.g., Section 6.1.1 of [RFC1123])
   are available on the host client.

   The use of DHCPv4 or DHCPv6 depends on the PCP deployment scenarios.

2.  Terminology

   This document makes use of the following terms:




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   o  PCP Server denotes a functional element which receives and
      processes PCP requests from a PCP Client.  A PCP Server can be co-
      located with or be separated from the function (e.g., NAT,
      Firewall) it controls.  Refer to [I-D.ietf-pcp-base].
   o  PCP Client denotes a PCP software instance responsible for issuing
      PCP requests to a PCP Server.  Refer to [I-D.ietf-pcp-base].
   o  DHCP refers to both DHCPv4 [RFC2131] and DHCPv6 [RFC3315].
   o  DHCP client (or client) denotes a node that initiates requests to
      obtain configuration parameters from one or more DHCP servers.
   o  DHCP server (or server) refers to a node that responds to requests
      from DHCP clients.
   o  Name is a domain name (as per Section 8 of [RFC3315]) that
      contains one or more labels.  In particular, a PCP name may be
      structured as DNS qualified name or be composed of strings such as
      can be passed to getaddrinfo (Section 6.1 of [RFC3493]), including
      address literals, etc.

3.  DHCPv6 PCP Server Option

   This DHCPv6 option conveys a name to be used to retrieve the IP
   addresses of PCP Server(s).  Appropriate name resolution queries
   should be issued to resolve the conveyed name.

3.1.  Format

   The format of the DHCPv6 PCP Server option is shown in Figure 1.

    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      OPTION_PCP_SERVER        |         Option-length         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   :                    PCP Server Domain Name(s)                  :
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                  Figure 1: PCP Server Name DHCPv6 Option

   The fields of the option shown in Figure 1 are as follows:

   o  Option-code: OPTION_PCP_SERVER (TBA, see Section 9.1)
   o  Option-length: Length of the 'PCP Server Domain Name' field in
      octets.
   o  PCP Server Domain Name(s): The domain name (s) of the PCP Server
      to be used by the PCP Client.  The OPTION_PCP_SERVER option can
      include multiple PCP Server Domain Names; each name is treated as
      a separate PCP Server.  The domain name is encoded as specified in
      Section 8 of [RFC3315].



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3.2.  Client Behavior

   To discover a PCP Server [I-D.ietf-pcp-base], the DHCPv6 client MUST
   include an Option Request Option (ORO) requesting the DHCPv6 PCP
   Server Name option as described in Section 22.7 of [RFC3315] (i.e.,
   include OPTION_PCP_SERVER on its OPTION_ORO).

   If the DHCPv6 client receives an OPTION_PCP_SERVER option from the
   DHCPv6 server, it extracts the name(s) conveyed in the
   OPTION_PCP_SERVER option and proceeds to validate it.  The DHCPv6
   client MUST verify the name(s) is properly encoded as detailed in
   Section 8 of [RFC3315].

   Once each name conveyed in the OPTION_PCP_SERVER option is validated,
   the DHCPv6 client MUST follow the procedure specified in Section 5.

4.  DHCPv4 PCP Option

4.1.  Format

   The PCP Server Name DHCPv4 option can be used to configure a name to
   be used by the PCP Client to contact a PCP Server.  The format of
   this option is illustrated in Figure 2.

          Code  Length   PCP Server Domain Name
         +-----+-----+-----+-----+-----+-----+-----+--
         | TBA |  n  |  s1 |  s2 |  s3 |  s4 | s5  |  ...
         +-----+-----+-----+-----+-----+-----+-----+--


                  Figure 2: PCP Server Name DHCPv4 Option

   The description of the fields is as follows:

   o  Code: OPTION_PCP_SERVER (TBA, see Section 9.2);
   o  Length: Includes the length of the "PCP Server Domain Name" field
      in octets; The maximum length is 255 octets.
   o  PCP Server Domain Name(s): The domain name(s) of the PCP Server to
      be used by the PCP Client when issuing PCP messages.  The
      OPTION_PCP_SERVER option can include multiple PCP Server Domain
      Names; each name is treated as a separate PCP Server.  The
      encoding of the domain name is described in Section 8 of
      [RFC3315].

   The OPTION_PCP_SERVER DHCPv4 option is a concatenation-requiring
   option.  As such, the mechanism specified in [RFC3396] MUST be used
   if the PCP Server Name option exceeds the maximum DHCPv4 option size
   of 255 octets.



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4.2.  Client Behavior

   DHCPv4 client expresses the intent to get OPTION_PCP_SERVER by
   specifying it in Parameter Request List Option [RFC2132].

   If the DHCPv4 client receives an OPTION_PCP_SERVER option from the
   DHCPv4 server, it extracts the name(s) conveyed in the option and
   proceeds to validate it.  The DHCPv4 client MUST verify the name(s)
   is properly encoded as detailed in Section 8 of [RFC3315].

   Once each name conveyed in the OPTION_PCP_SERVER option is validated,
   the DHCPv4 client MUST follow the procedure specified in Section 5.

5.  Use of PCP Server Names

   If the OPTION_PCP_SERVER option conveys IP address literals, the
   trailing dot MUST be removed.

   Each configured PCP Server Name is passed to the name resolution
   library (e.g., Section 6.1.1 of [RFC1123] or [RFC6055]) to retrieve
   the corresponding IP address(es) (IPv4 or IPv6).  It is out of scope
   of this document to specify how the PCP Client selects the PCP
   Server(s) to contact.

   Multiple PCP Server Names may be configured to a PCP Client in some
   deployment contexts such as multi-homing.  It is out of scope of this
   document to enumerate all deployment scenarios which require multiple
   Names to be configured.

   A host may have multiple network interfaces (e.g, 3G, WiFi, etc.);
   each configured differently.  Each PCP Server learned MUST be
   associated with the interface via which it was learned.

6.  Dual-Stack Hosts

   In some deployment contexts, the PCP Server may be reachable with an
   IPv4 address but DHCPv6 is used to provision the PCP Client.  In such
   scenarios, a plain IPv4 address or an IPv4-mapped IPv6 address can be
   configured to reach the PCP Server.

   A Dual-Stack host may receive OPTION_PCP_SERVER via both DHCPv4 and
   DHCPv6.  The content of these OPTION_PCP_SERVER options may refer to
   the same or distinct PCP Servers.  This is deployment-specific and as
   such it is out of scope of this document.

7.  Guidance to Administrators





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   If IPv4 address literals are to be returned in the OPTION_PCP_SERVER
   option, administrators should not configure ambiguous strings such as
   "10.0.258", "0xA000001", and "012.0x102"; the strict form is
   recommended instead.  Refer to Section 3.1.1 and Section 3.1.2 of
   [I-D.iab-identifier-comparison] for a more generic discussion on IP
   address literals.

8.  Security Considerations

   The security considerations in [RFC2131], [RFC3315] and
   [I-D.ietf-pcp-base] are to be considered.

9.  IANA Considerations

9.1.  DHCPv6 Option

   IANA is requested to assign the following new DHCPv6 Option Code in
   the registry maintained in http://www.iana.org/assignments/
   dhcpv6-parameters:

                                Option Name Value
                          ----------------- -----
                          OPTION_PCP_SERVER TBA


9.2.  DHCPv4 Option

   IANA is requested to assign the following new DHCPv4 Option Code in
   the registry maintained in http://www.iana.org/assignments/bootp-
   dhcp-parameters/:

                                Option Name Value
                          ----------------- -----
                          OPTION_PCP_SERVER TBA


10.  Acknowledgements

   Many thanks to B.  Volz, C.  Jacquenet, R.  Maglione, D.  Thaler, T.
   Mrugalski, T.  Reddy, S.  Cheshire and M.  Wasserman for their review
   and comments.

   Special thanks to T.  Lemon for the review and his continuous effort
   to enhance this specification.

11.  References





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11.1.  Normative References

   [I-D.ietf-pcp-base]
              Wing, D., Cheshire, S., Boucadair, M., Penno, R., and P.
              Selkirk, "Port Control Protocol (PCP)", draft-ietf-pcp-
              base-29 (work in progress), November 2012.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2131]  Droms, R., "Dynamic Host Configuration Protocol", RFC
              2131, March 1997.

   [RFC2132]  Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor
              Extensions", RFC 2132, March 1997.

   [RFC3315]  Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C.,
              and M. Carney, "Dynamic Host Configuration Protocol for
              IPv6 (DHCPv6)", RFC 3315, July 2003.

   [RFC3396]  Lemon, T. and S. Cheshire, "Encoding Long Options in the
              Dynamic Host Configuration Protocol (DHCPv4)", RFC 3396,
              November 2002.

11.2.  Informative References

   [I-D.iab-identifier-comparison]
              Thaler, D., "Issues in Identifier Comparison for Security
              Purposes", draft-iab-identifier-comparison-03 (work in
              progress), July 2012.

   [I-D.ietf-behave-lsn-requirements]
              Perreault, S., Yamagata, I., Miyakawa, S., Nakagawa, A.,
              and H. Ashida, "Common requirements for Carrier Grade NATs
              (CGNs)", draft-ietf-behave-lsn-requirements-10 (work in
              progress), December 2012.

   [I-D.ietf-dhc-option-guidelines]
              Hankins, D., Mrugalski, T., Siodelski, M., Jiang, S., and
              S. Krishnan, "Guidelines for Creating New DHCPv6 Options",
              draft-ietf-dhc-option-guidelines-10 (work in progress),
              February 2013.

   [RFC1123]  Braden, R., "Requirements for Internet Hosts - Application
              and Support", STD 3, RFC 1123, October 1989.






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   [RFC3493]  Gilligan, R., Thomson, S., Bound, J., McCann, J., and W.
              Stevens, "Basic Socket Interface Extensions for IPv6", RFC
              3493, February 2003.

   [RFC6055]  Thaler, D., Klensin, J., and S. Cheshire, "IAB Thoughts on
              Encodings for Internationalized Domain Names", RFC 6055,
              February 2011.

   [RFC6146]  Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful
              NAT64: Network Address and Protocol Translation from IPv6
              Clients to IPv4 Servers", RFC 6146, April 2011.

   [RFC6333]  Durand, A., Droms, R., Woodyatt, J., and Y. Lee, "Dual-
              Stack Lite Broadband Deployments Following IPv4
              Exhaustion", RFC 6333, August 2011.

   [RFC6334]  Hankins, D. and T. Mrugalski, "Dynamic Host Configuration
              Protocol for IPv6 (DHCPv6) Option for Dual-Stack Lite",
              RFC 6334, August 2011.

Appendix A.  Rationale

   Distinct IP-Address and Name DHCP options have been considered in
   early stages of this specification.  This flexibility aims to let
   service providers make their own engineering choices and use the most
   convenient option according to their deployment context.
   Nevertheless, the DHC WG's position is this flexibility has some
   drawbacks such as inducing errors (See Section 7 of
   [I-D.ietf-dhc-option-guidelines]).  Therefore, only the Name option
   is maintained within this document.

   This choice is motivated by operational considerations: In
   particular, some Service Providers are considering two levels of
   redirection:

   (1)  The first level is national-wise and undertaken by DHCP: a
      regional-specific Name will be returned;
   (2)  The second level is done during the resolution of the regional-
      specific Name to redirect the customer to a regional PCP server
      among a pool deployed regionally.

   Distinct operational teams are responsible for each of the above
   mentioned levels.  A clear separation between the functional
   perimeter of each team is a sensitive task for the maintenance of the
   offered services.  Regional teams will require to introduce new
   resources (e.g., new PCP-controlled devices such as Carrier Grade
   NATs (CGNs, [I-D.ietf-behave-lsn-requirements])) to meet an increase
   in customer base.  Operations related to the introduction of these



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   new devices (e.g., addressing, redirection, etc.)  are implemented
   locally.  Having this regional separation provides flexibility to
   manage portions of network operated by dedicated teams.  This two-
   level redirection can not be met by the IP Address option.

   In addition to the operational considerations:

   o  The use of the Name for NAT64 [RFC6146] might be suitable for
      load-balancing purposes;
   o  For the DS-Lite case [RFC6333], if the encapsulation mode is used
      to send PCP messages, an IP address may be used since the AFTR
      selection is already done via the AFTR_NAME DHCPv6 option
      [RFC6334].  Of course, this assumes that the PCP Server is co-
      located with the AFTR function.  If these functions are not co-
      located, conveying the Name would be more convenient.

   Returning a Name requires the host to embed a name resolution
   service.  Some may present this as an argument against defining a
   Name option.  Nevertheless, this argument may be objected as
   implementing a name resolution library (e.g., embed a DNS resolver)
   is cheap and devices which don't embed DNS resolver are uncommon.

Authors' Addresses

   Mohamed Boucadair
   France Telecom
   Rennes  35000
   France

   Email: mohamed.boucadair@orange.com


   Reinaldo Penno
   Cisco
   USA

   Email: repenno@cisco.com


   Dan Wing
   Cisco Systems, Inc.
   170 West Tasman Drive
   San Jose, California  95134
   USA

   Email: dwing@cisco.com




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