PCP Working Group                                           M. Boucadair
Internet-Draft                                            France Telecom
Intended status: Standards Track                                R. Penno
Expires: May 28, 2012                                   Juniper Networks
                                                                 D. Wing
                                                                   Cisco
                                                       November 25, 2011


            DHCP Options for the Port Control Protocol (PCP)
                         draft-ietf-pcp-dhcp-01

Abstract

   This document specifies DHCP (IPv4 and IPv6) options to configure
   hosts with Port Control Protocol (PCP) Server addresses.  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 May 28, 2012.

Copyright Notice

   Copyright (c) 2011 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



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   (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  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
   3.  Rationale . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
   4.  Consistent NAT and PCP Configuration  . . . . . . . . . . . . . 4
   5.  DHCPv6 PCP Server Option  . . . . . . . . . . . . . . . . . . . 5
     5.1.  Format  . . . . . . . . . . . . . . . . . . . . . . . . . . 5
     5.2.  Client Behaviour  . . . . . . . . . . . . . . . . . . . . . 5
   6.  DHCPv4 PCP Option . . . . . . . . . . . . . . . . . . . . . . . 6
     6.1.  Format  . . . . . . . . . . . . . . . . . . . . . . . . . . 6
     6.2.  Client Behaviour  . . . . . . . . . . . . . . . . . . . . . 7
   7.  Dual-Stack Hosts  . . . . . . . . . . . . . . . . . . . . . . . 7
   8.  Security Considerations . . . . . . . . . . . . . . . . . . . . 7
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 8
     9.1.  DHCPv6 Option . . . . . . . . . . . . . . . . . . . . . . . 8
     9.2.  DHCPv4 Option . . . . . . . . . . . . . . . . . . . . . . . 8
   10. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 8
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . . . 8
     11.1. Normative References  . . . . . . . . . . . . . . . . . . . 8
     11.2. Informative References  . . . . . . . . . . . . . . . . . . 9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 9




















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1.  Introduction

   This document defines IPv4 DHCP [RFC2131] and DHCPv6 [RFC3315]
   options which can be used to provision PCP Server [I-D.ietf-pcp-base]
   reachability information; more precisely it defines DHCP options to
   convey a Fully Qualified Domain Name (FQDN, as per Section 3.1 of
   [RFC1035]) of PCP Server(s).  In order to make use of these options,
   this document assumes appropriate name resolution means (see Section
   6.1.1 of [RFC1123]) are available on the host client.

   The use of IPv4 DHCP or DHCPv6 depends on the PCP deployment
   scenarios.


2.  Terminology

   This document makes use of the following terms:

   o  PCP Server: 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: a PCP software instance responsible for issuing PCP
      requests to a PCP Server.  Refer to [I-D.ietf-pcp-base].

   o  DHCPv4 refers to IPv4 DHCP [RFC2131].

   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
      [RFC3315].

   o  DHCP server (or server) refers to a node that responds to requests
      from DHCP clients [RFC3315].


3.  Rationale

   Both IP Address and Name DHCP options have been defined in previous
   versions of this document.  This flexibility aims to let service
   providers to make their own engineering choices and use the
   convenient option according to their deployment context.
   Nevertheless, DHC WG's position is this flexibility have some
   drawbacks such as inducing errors.  Therefore, only the Name option
   is maintained within this document.




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   This choice of defining the PCP Name option rather than the IP
   address is motivated by operational considerations: In particular,
   some Service Providers are considering two levels of redirection: (1)
   The first level is national-wise is undertaken by DHCP: a regional-
   specific FQDN will be returned; (2) The second level is done during
   the resolution of the regional-specific FQDN to redirect the customer
   to a regional PCP Servers 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 of customer
   base.  Operations related to the introduction of these 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 FQDN 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 FQDN would be more convenient.

   If the PCP Server is located in a LAN, a simple FQDN such as "pcp-
   server.local" can be used.


4.  Consistent NAT and PCP Configuration

   The PCP Server discovered through DHCP must be able to install
   mappings on the appropriate upstream PCP-controlled device that will
   be crossed by packets transmitted by the host or any terminal
   belonging to the same realm (e.g., DHCP client is embedded in a CP
   router).  In case this prerequisite is not met, customers would
   experience service troubles and their service(s) won't be delivered
   appropriately.

   Note that this constraint is implicitly met in scenarios where only
   one single PCP-controlled device is deployed in the network.




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5.  DHCPv6 PCP Server Option

   This DHCPv6 option conveys a domain 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.  For instance, in the
   context of a DS-Lite architecture [RFC6333], the retrieved address
   may be an IPv4 address or an IPv4-mapped IPv6 address [RFC4291], and
   in the case of NAT64 [RFC6146] an IPv6 address can be retrieved.

5.1.  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                     :
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                  Figure 1: PCP Server FQDN 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: The domain name of the PCP Server to be
      used by the PCP Client.  The domain name is encoded as specified
      in Section 8 of [RFC3315].

5.2.  Client Behaviour

   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).  A client MAY also
   include the OPTION_DNS_SERVERS option on its OPTION_ORO to retrieve a
   DNS servers list.

   If the DHCPv6 client receives more than one OPTION_PCP_SERVER option
   from the DHCPv6 server, only the first instance of that option MUST
   be used.




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   Upon receipt of an OPTION_PCP_SERVER option, the DHCPv6 client MUST
   verify that the option length does not exceed 255 octets [RFC1035]).
   The DHCPv6 client MUST verify the FQDN is a properly encoded as
   detailed in Section 8 of [RFC3315].

   Once the FQDN conveyed in a OPTION_PCP_SERVER option is validated,
   the included Name is passed to the name resolution library (see
   Section 6.1.1 of [RFC1123] or [RFC6055]) to retrieve the
   corresponding IP address (IPv4 or IPv6).  If more than one IPv6/IPv4
   address are retrieved, the PCP Client MUST use the procedure defined
   in [I-D.ietf-pcp-base] for address selection.

   It is RECOMMENDED to associate a TTL with any address resulting from
   resolving the Name conveyed in a OPTION_PCP_SERVER DHCPv6 option when
   stored in a local cache.  Considerations on how to flush out a local
   cache are out of the scope of this document.


6.  DHCPv4 PCP Option

6.1.  Format

   The PCP Server DHCPv4 option can be used to configure a FQDN 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  |  ...
         +-----+-----+-----+-----+-----+-----+-----+--


   The values s1, s2, s3, etc. represent the domain name labels in the
   domain name encoding.

                        Figure 2: DHCPv4 PCP 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: The domain name of the PCP Server to be
      used by the PCP Client when issuing PCP messages.  The encoding of
      the domain name is described in Section 3.1 of [RFC1035].



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6.2.  Client Behaviour

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

   If the DHCPv4 client receives more than one OPTION_PCP_SERVER option
   from the DHCPv4 server, only the first instance of that option MUST
   be used.  If the selected OPTION_PCP_SERVER includes more than one
   FQDN, only the first instance of that option MUST be used.

   The client invokes the underlying name resolution library (see
   Section 6.1.1 of [RFC1123] or [RFC6055]) to retrieve the IPv4
   address(es) of the PCP server(s).

   It is RECOMMENDED to associate a TTL with any address resulting from
   resolving the Name conveyed in a OPTION_PCP_SERVER DHCPv4 option when
   stored in a local cache.  Considerations on how to flush out a local
   cache are out of the scope of this document.


7.  Dual-Stack Hosts

   A PCP Server configured using OPTION_PCP_SERVER over DHCPv4 is likely
   to be resolved to IPv4 address(es).

   A PCP Server configured using OPTION_PCP_SERVER over DHCPv6 may be
   resolved to IPv4 address(es) (e.g., DS-Lite [RFC6333]) or IPv6
   address(es) (e.g., NAT64 [RFC6146], IPv6 firewall [RFC6092], NPTv6
   [RFC6296]).

   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.


8.  Security Considerations

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






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9.  IANA Considerations

9.1.  DHCPv6 Option

   Authors of this document request the following DHCPv6 option code:

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

9.2.  DHCPv4 Option

   Authors of this document request the following DHCPv4 option code:

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


10.  Acknowledgements

   Many thanks to B. Volz, C. Jacquenet, R. Maglione, D. Thaler, T.
   Mrugalski and T. Lemon for their review and comments.


11.  References

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-17 (work in progress), October 2011.

   [RFC1035]  Mockapetris, P., "Domain names - implementation and
              specification", STD 13, RFC 1035, November 1987.

   [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



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              IPv6 (DHCPv6)", RFC 3315, July 2003.

   [RFC4291]  Hinden, R. and S. Deering, "IP Version 6 Addressing
              Architecture", RFC 4291, February 2006.

11.2.  Informative References

   [I-D.ietf-behave-lsn-requirements]
              Perreault, S., Yamagata, I., Miyakawa, S., Nakagawa, A.,
              and H. Ashida, "Common requirements for Carrier Grade NAT
              (CGN)", draft-ietf-behave-lsn-requirements-04 (work in
              progress), October 2011.

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

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

   [RFC6092]  Woodyatt, J., "Recommended Simple Security Capabilities in
              Customer Premises Equipment (CPE) for Providing
              Residential IPv6 Internet Service", RFC 6092,
              January 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.

   [RFC6296]  Wasserman, M. and F. Baker, "IPv6-to-IPv6 Network Prefix
              Translation", RFC 6296, June 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.












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Authors' Addresses

   Mohamed Boucadair
   France Telecom
   Rennes,   35000
   France

   Email: mohamed.boucadair@orange.com


   Reinaldo Penno
   Juniper Networks
   1194 N Mathilda Avenue
   Sunnyvale, California  94089
   USA

   Email: rpenno@juniper.net


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

   Email: dwing@cisco.com

























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