DHCP Options for the Port Control Protocol (PCP)
draft-ietf-pcp-dhcp-02

PCP Working Group                                           M. Boucadair
Internet-Draft                                            France Telecom
Intended status: Standards Track                                R. Penno
Expires: July 16, 2012                                  Juniper Networks
                                                                 D. Wing
                                                                   Cisco
                                                        January 13, 2012

            DHCP Options for the Port Control Protocol (PCP)
                         draft-ietf-pcp-dhcp-02

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
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   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 July 16, 2012.

Copyright Notice

   Copyright (c) 2012 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
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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  Rationale  . . . . . . . . . . . . . . . . . . . . . . . . . .  3
   4.  Consistent NAT and PCP Configuration . . . . . . . . . . . . .  4
   5.  IP Address Selection . . . . . . . . . . . . . . . . . . . . .  5
     5.1.  Serial Queries . . . . . . . . . . . . . . . . . . . . . .  5
     5.2.  Parallel Queries . . . . . . . . . . . . . . . . . . . . .  5
   6.  DHCPv6 PCP Server Option . . . . . . . . . . . . . . . . . . .  5
     6.1.  Format . . . . . . . . . . . . . . . . . . . . . . . . . .  6
     6.2.  Client Behaviour . . . . . . . . . . . . . . . . . . . . .  6
   7.  DHCPv4 PCP Option  . . . . . . . . . . . . . . . . . . . . . .  7
     7.1.  Format . . . . . . . . . . . . . . . . . . . . . . . . . .  7
     7.2.  Client Behaviour . . . . . . . . . . . . . . . . . . . . .  8
   8.  Dual-Stack Hosts . . . . . . . . . . . . . . . . . . . . . . .  8
   9.  Security Considerations  . . . . . . . . . . . . . . . . . . .  9
   10. IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  9
     10.1. DHCPv6 Option  . . . . . . . . . . . . . . . . . . . . . .  9
     10.2. DHCPv4 Option  . . . . . . . . . . . . . . . . . . . . . .  9
   11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . .  9
   12. References . . . . . . . . . . . . . . . . . . . . . . . . . .  9
     12.1. Normative References . . . . . . . . . . . . . . . . . . .  9
     12.2. Informative References . . . . . . . . . . . . . . . . . . 10
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11

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1.  Introduction

   This document defines DHCPv4 [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 name (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 (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:

   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  DHCPv4 refers to the Dynamic Host Configuration Protocol [RFC2131]
      for IPv4.
   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].
   o  Name is a domain name (as per Section 3.1 of [RFC1035]) 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.  Rationale

   Both IP Address and Name DHCP options have been considered in early
   stages of this specification.  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 document defines an option to carry a name rather than an IP
   address.  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 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 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
   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 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.

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.  IP Address Selection

   Resolving the Name conveyed in DHCP PCP Name options may return a
   list of IP addresses.  This section specifies the behavior to be
   followed by the PCP Client to contact its PCP Server.

   1.  If only one PCP Name option is returned in DHCP: the PCP Client
       follows the procedure specified in Section 5.1 if a list of IP
       addresses are returned as a result of resolving the name conveyed
       in the PCP Name DHCP option.
   2.  If several PCP Name options are returned in DHCP: the PCP Client
       contacts in parallel all PCP Servers as defined in Section 5.2.
       For each PCP Name option occurrence, the PCP Client resolves the
       conveyed name; if more than one IP address are returned, the PCP
       Client follows the procedure specified in Section 5.1.

5.1.  Serial Queries

   The PCP Client initializes its retransmission timer, RETRY_TIMER, to
   2 seconds.  The PCP Client sends its PCP message to the PCP Server
   and waits 2 seconds for a response.  If no response is received, it
   doubles the value of RETRY_TIMER, sends another (identical) PCP
   message and waits 2*RETRY_TIMER.  This procedure is repeated three
   (3) times, doubling the value of RETRY_TIMER each time.  If no
   response is received after four (4) attempts, the PCP Client tries
   with the next IP address in its list of PCP Servers.  If it has
   exhausted its list, the procedure is repeated every fifteen minutes
   until the PCP request is successfully answered.  If, when sending PCP
   requests the PCP Client receives an ICMP error (e.g., port
   unreachable, network unreachable) it SHOULD immediately try the next
   IP address in the list.  Once the PCP Client has successfully
   received a response from a PCP Server on that interface, it sends
   subsequent PCP requests to that same server until that PCP Server
   becomes non-responsive, which causes the PCP client to attempt to re-
   iterate the procedure starting with the first PCP Server on its list.

5.2.  Parallel Queries

   The PCP Client contacts in parallel all the PCP Servers in the IP
   addresses list.  For each IP address in the list, the PCP Client
   follows the procedure specified in Section 7.1 of
   [I-D.ietf-pcp-base].

6.  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

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   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.

6.1.  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 Name DHCPv6 Option

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

   o  Option-code: OPTION_PCP_SERVER (TBA, see Section 10.1)
   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].

6.2.  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, it extracts the Name conveyed in each
   OPTION_PCP_SERVER option and proceeds to validating it.  If more than
   one Name is included in a OPTION_PCP_SERVER option occurrence, only
   the first instance MUST be used.  Then, the DHCPv6 client MUST verify
   that the option length does not exceed 255 octets [RFC1035]).  The
   DHCPv6 client MUST verify the name is properly encoded as detailed in
   Section 8 of [RFC3315].

   Once the name conveyed in each OPTION_PCP_SERVER option is validated,

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   the included 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).

   The PCP Client MUST follow the procedure specified in Section 5 to
   contact its PCP Server(s).

   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.

   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.  When an
   application issues a PCP request to a PCP Server, the source address
   of the request MUST be among those assigned on the interface to which
   the destination PCP Server is bound.

7.  DHCPv4 PCP Option

7.1.  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  |  ...
         +-----+-----+-----+-----+-----+-----+-----+--

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

                  Figure 2: PCP Server Name DHCPv4 Option

   The description of the fields is as follows:
   o  Code: OPTION_PCP_SERVER (TBA, see Section 10.2);
   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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7.2.  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, it extracts the Name conveyed in each
   OPTION_PCP_SERVER option and proceeds to validating it.  If more than
   one Name is included in a OPTION_PCP_SERVER option occurrence, only
   the first instance MUST be used.  Then, the DHCPv4 client MUST verify
   that the option length does not exceed 255 octets [RFC1035]).

   Once the name conveyed in each OPTION_PCP_SERVER option is validated,
   the included Name is passed to the name resolution library (e.g.,
   Section 6.1.1 of [RFC1123] or [RFC6055]) to retrieve the
   corresponding IPv4 address(es).

   The PCP Client MUST follow the procedure specified in Section 5 to
   contact its 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.

   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.  When an
   application issues a PCP request to a PCP Server, the source address
   of the request MUST be among those assigned on the interface to which
   the destination PCP Server is bound.

8.  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.

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   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.

9.  Security Considerations

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

10.  IANA Considerations

10.1.  DHCPv6 Option

   Authors of this document request the following DHCPv6 option code:

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

10.2.  DHCPv4 Option

   Authors of this document request the following DHCPv4 option code:

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

11.  Acknowledgements

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

12.  References

12.1.  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-21 (work in progress), January 2012.

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

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   [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.

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

12.2.  Informative References

   [I-D.ietf-behave-lsn-requirements]
              Perreault, S., Yamagata, I., Miyakawa, S., Nakagawa, A.,
              and H. Ashida, "Common requirements for Carrier Grade NATs
              (CGNs)", draft-ietf-behave-lsn-requirements-05 (work in
              progress), November 2011.

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

   [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.

   [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-

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              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.

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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