



Softwire WG                                                 T. Mrugalski
Internet-Draft                                                       ISC
Intended status: Standards Track                                O. Troan
Expires: September 10, 2015                                        Cisco
                                                               I. Farrer
                                                     Deutsche Telekom AG
                                                            S. Perreault
                                                                Viagenie
                                                                  W. Dec
                                                                   Cisco
                                                                  C. Bao
                                                     Tsinghua University
                                                                  L. Yeh
                                                                   CNNIC
                                                                 X. Deng

                                                          March 09, 2015


  DHCPv6 Options for configuration of Softwire Address and Port Mapped
                                Clients
                    draft-ietf-softwire-map-dhcp-12

Abstract

   This document specifies DHCPv6 options, termed Softwire46 options,
   for the provisioning of Softwire46 Customer Edge (CE) devices.
   Softwire46 is a collective term used to refer to architectures based
   on the notion of IPv4 Address+Port (A+P) for providing IPv4
   connectivity across an IPv6 network.

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 10, 2015.




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Copyright Notice

   Copyright (c) 2015 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.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Softwire46 Overview . . . . . . . . . . . . . . . . . . . . .   3
   4.  Common Softwire46 DHCPv6 Options  . . . . . . . . . . . . . .   4
     4.1.  S46 Rule Option . . . . . . . . . . . . . . . . . . . . .   5
     4.2.  S46 BR Option . . . . . . . . . . . . . . . . . . . . . .   7
     4.3.  S46 DMR Option  . . . . . . . . . . . . . . . . . . . . .   7
     4.4.  S46 IPv4/IPv6 Address Binding Option  . . . . . . . . . .   8
     4.5.  S46 Port Parameters Option  . . . . . . . . . . . . . . .   9
   5.  Softwire46 Containers . . . . . . . . . . . . . . . . . . . .  10
     5.1.  Softwire46 MAP-E Container Option . . . . . . . . . . . .  10
     5.2.  Softwire46 MAP-T Container Option . . . . . . . . . . . .  11
     5.3.  Softwire46 LightWeight 46 Container Option  . . . . . . .  11
   6.  Softwire46 Options Formatting . . . . . . . . . . . . . . . .  12
   7.  DHCPv6 Server Behavior  . . . . . . . . . . . . . . . . . . .  13
   8.  DHCPv6 Client Behavior  . . . . . . . . . . . . . . . . . . .  13
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .  14
   10. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  14
   11. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  15
   12. References  . . . . . . . . . . . . . . . . . . . . . . . . .  15
     12.1.  Normative References . . . . . . . . . . . . . . . . . .  15
     12.2.  Informative References . . . . . . . . . . . . . . . . .  15
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  16

1.  Introduction

   A number of architectural solution proposals discussed in the IETF
   Softwire Working Group use Address and Port (A+P) as their technology
   base for providing IPv4 connectivity to end users using CE devices
   across a Service Provider's IPv6 network, while allowing for shared
   or dedicated IPv4 addressing of CEs.



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   An example is Mapping of Address and Port (MAP) defined in
   [I-D.ietf-softwire-map].  The MAP solution consists of one or more
   MAP Border Relay (BR) routers, responsible for stateless forwarding
   between a MAP IPv6 domain and an IPv4 network, and one or more MAP
   Customer Edge (CE) routers, responsible for forwarding between a
   user's IPv4 network and the MAP IPv6 network domain.  Collectively,
   the MAP CE and BR form a domain when configured with common service
   parameters.  This characteristic is common to all of the Softwire46
   mechanisms.

   To function in such a domain, a CE needs to be provisioned with the
   appropriate A+P service parameters for that domain.  These consist
   primarily of the CE's IPv4 address and transport layer port-range(s).
   Furthermore, the IPv6 transport mode (i.e. encapsulation or
   translation) needs to be specified.  Provisioning of other IPv4
   configuration information not derived directly from the A+P service
   parameters is not covered in this document.  It is expected that
   provisioning of other IPv4 configuration will continue to use DHCPv4
   [RFC2131].

   This memo specifies a set of DHCPv6 [RFC3315] options to provision
   Softwire46 information to CE routers.  Although the focus is to
   deliver IPv4 service to an end-user network (such as a residential
   home network), it can equally be applied to an individual host acting
   as a CE.  Configuration of the BR is out of scope of this document.

2.  Conventions

   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].

3.  Softwire46 Overview

   This document describes a set of common DHCPv6 options for
   configuring the MAP-E [I-D.ietf-softwire-map], MAP-T
   [I-D.ietf-softwire-map-t] and Lightweight 4over6
   [I-D.ietf-softwire-lw4over6] mechanisms.  For definition of the
   terminology used in this document please see the relevant terminology
   sections in the above references.

   MAP-E, MAP-T and Lightweight 4over6 are essentially providing the
   same functionality: IPv4 service to a CE router over an IPv6 only
   access network.  MAP-E and MAP-T may embed parts of the IPv4 address
   in IPv6 prefixes, thereby supporting many clients with a fixed set of
   mapping rules and mesh mode (direct CE to CE communication).  MAP-E
   and MAP-T CEs may also be provisioned in hub and spoke mode, and in
   1:1 mode (with no embedded address bits).  The difference between



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   MAP-E and MAP-T is that they use different means to connect to the
   IPv6 domain.  MAP-E uses [RFC2473] IPv4 over IPv6 tunnelling, while
   MAP-T uses NAT64 [RFC6145] based translation.  Lightweight 4over6 is
   a hub and spoke IPv4 over IPv6 tunneling mechanism, with complete
   independence of IPv4 and IPv6 addressing (zero embedded address
   bits).

   The DHCP options described here tie the provisioning parameters, and
   hence the IPv4 service itself, to the End-user IPv6 prefix lifetime.
   The validity of a Softwire46's IPv4 address, prefix or shared IPv4
   address, port set and any authorization and accounting are tied to
   the lifetime of its associated End-user IPv6 prefix.

   To support more than one mechanism at a time and to allow for a
   possibility of transition between them, the DHCPv6 Option Request
   Option [RFC3315] is used.  Each mechanism has a corresponding DHCPv6
   container option.  A DHCPv6 client can request a particular mechanism
   by including the option code for a particular container option in its
   ORO option.  The provisioning parameters for that mechanism are
   expressed by embedding the common format options within the
   respective container option.

   This approach implies that all of the provisioning options MUST
   appear only within the container options.  The client MUST NOT
   request any of the provisioning options directly within an ORO.  MAP-
   DHCP clients that receive provisioning options that are not
   encapsulated in container options MUST silently ignore these options.
   DHCP server administrators are advised to ensure that DHCP servers
   are configured to send these options in the proper encapsulation.

   The document is organized with the common sub-options described
   first, followed by the three container options.  Some sub-options are
   mandatory in some containers, some are optional and some are not
   permitted at all.  This is shown in Table 1.

4.  Common Softwire46 DHCPv6 Options

   The DHCPv6 protocol is used for Softwire46 CE provisioning following
   regular DHCPv6 notions, with the CE assuming the role of a DHCPv6
   client, and the DHCPv6 server providing options following DHCPv6
   server side policies.  The format and usage of the options are
   defined in the following sub-sections.

   Each CE needs to be provisioned with enough information to calculate
   its IPv4 address, IPv4 prefix or shared IPv4 address.  MAP-E and
   MAP-T use the OPTION_S46_RULE, while Lightweight 4over6 uses the
   OPTION_S46_V4V6BIND option.  A CE that needs to communicate outside
   of the A+P domain also needs the address or prefix of the BR.  MAP-E



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   and Lightweight 4over6 use the OPTION_S46_BR option to communicate
   the IPv6 address of the BR.  MAP-T forms an IPv6 destination address
   by embedding an IPv4 destination address into the BR's IPv6 prefix
   conveyed via the OPTION_S46_DMR option.  Optionally, all mechanisms
   can include OPTION_S46_PORTPARAMS to specify parameters and port sets
   for the port range algorithm.

   Softwire46 options use addresses rather than FQDNs.  For rationale
   behind this design choice, see Section 8 of [RFC7227].

4.1.  S46 Rule Option

   Figure 1 shows the format of the S46 Rule option (OPTION_S46_RULE)
   used for conveying the Basic Mapping Rule (BMR) and Forwarding
   Mapping Rule (FMR).

   This option follows behavior described in Sections 17.1.1 and 18.1.1
   of [RFC3315].  Clients can insert those options with specific values
   as hints for the server.  Depending on the server configuration and
   policy, it may accept or ignore the hints.  Client MUST be able to
   process received values that are different than the hints it sent
   earlier.

      0                   1                   2                   3
      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_S46_RULE        |         option-length         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |     flags     |     ea-len    |  prefix4-len  | ipv4-prefix   |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                  (continued)                  |  prefix6-len  |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                           ipv6-prefix                         |
     |                       (variable length)                       |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     .                        S46_RULE-options                       .
     .                                                               .
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                         Figure 1: S46 Rule Option

   o  option-code: OPTION_S46_RULE (TBD1)

   o  option-length: length of the option, excluding option-code and
      option-length fields, including length of all encapsulated
      options, expressed in bytes.




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   o  flags: 8 bits long field carrying flags applicable to the rule.
      The meaning of specific bits are explained in Figure 2.

   o  ea-len: 8 bits long field that specifies the Embedded-Address (EA)
      bit length.  Allowed values range from 0 to 48.

   o  prefix4-len: 8 bits long field expressing the prefix length of the
      IPv4 prefix specified in the rule-ipv4-prefix field.  Valid values
      0 to 32.

   o  ipv4-prefix: a fixed length 32 bit field that specifies the IPv4
      prefix for the S46 rule.  The bits in the prefix after prefix4-len
      number of bits are reserved and MUST be initialized to zero by the
      sender and ignored by the receiver.

   o  prefix6-len: 8 bits long field expressing the length of the IPv6
      prefix specified in the rule-ipv6-prefix field.

   o  ipv6-prefix: a variable length field that specifies the IPv6
      domain prefix for the S46 rule.  The field is padded on the right
      with zero bits up to the nearest octet boundary when prefix6-len
      is not evenly divisible by 8.

   o  S46_RULE-options: a variable field that may contain zero or more
      options that specify additional parameters for this S46 rule.
      This document specifies one such option, OPTION_S46_PORTPARAMS.

   The Format of the S46 Rule Flags field is:

                              0 1 2 3 4 5 6 7
                             +-+-+-+-+-+-+-+-+
                             |Reserved     |F|
                             +-+-+-+-+-+-+-+-+

                         Figure 2: S46 Rule Flags

   o  Reserved: 7-bits reserved for future use as flags.

   o  F-Flag: 1 bit field that specifies whether the rule is to be used
      for forwarding (FMR).  If set, this rule is used as a FMR, if not
      set this rule is a BMR only and MUST NOT be used for forwarding.
      Note: A BMR can also be used as an FMR for forwarding if the
      F-flag is set.  The BMR rule is determined by a longest-prefix
      match of the Rule-IPv6-prefix against the End-User IPv6
      prefix(es).






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   It is expected that in a typical mesh deployment scenario, there will
   be a single BMR, which could also be designated as an FMR using the
   F-Flag.

4.2.  S46 BR Option

   The S46 BR Option (OPTION_S46_BR) is used to convey the IPv6 address
   of the Border Relay.  Figure 4 shows the format of the OPTION_S46_BR
   option.

      0                   1                   2                   3
      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_S46_BR         |         option-length         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                      br-ipv6-address                          |
     |                                                               |
     |                                                               |
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                          Figure 3: S46 BR Option

   o  option-code: OPTION_S46_BR (TBD2)

   o  option-length: 16

   o  br-ipv6-address: a fixed length field of 16 octets that specifies
      the IPv6 address for the S46 BR.

   BR redundancy can be implemented by using an anycast address for the
   BR IPv6 address.  Multiple OPTION_S46_BR options MAY be included in
   the container; this document does not further explore the use of
   multiple BR IPv6 addresses.

4.3.  S46 DMR Option

   The S46 DMR Option (OPTION_S46_DMR) is used to convey values for the
   Default Mapping Rule (DMR).  Figure 4 shows the format of the
   OPTION_S46_DMR option used for conveying a DMR.

      0                   1                   2                   3
      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_S46_DMR         |         option-length         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |dmr-prefix6-len|            dmr-ipv6-prefix                    |
     +-+-+-+-+-+-+-+-+           (variable length)                   |



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     .                                                               .
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                         Figure 4: S46 DMR Option

   o  option-code: OPTION_S46_DMR (TBD3)

   o  option-length: 1 + length of dmr-ipv6-prefix specified in bytes.

   o  dmr-prefix6-len: 8 bits long field expressing the bit mask length
      of the IPv6 prefix specified in the dmr-ipv6-prefix field.

   o  dmr-ipv6-prefix: a variable length field specifying the IPv6
      prefix or address for the BR.  This field is right padded with
      zeros to the nearest octet boundary when dmr-prefix6-len is not
      divisible by 8.

4.4.  S46 IPv4/IPv6 Address Binding Option

   The IPv4 address Option (OPTION_S46_V4V6BIND) MAY be used to specify
   the full or shared IPv4 address of the CE.  The IPv6 prefix field is
   used by the CE to identify the correct prefix to use for the tunnel
   source.

      0                   1                   2                   3
      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_S46_V4V6BIND      |         option-length         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                         ipv4-address                          |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |bindprefix6-len|             bind-ipv6-prefix                  |
     +-+-+-+-+-+-+-+-+             (variable length)                 |
     .                                                               .
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     .                      S46_V4V6BIND-options                     .
     .                                                               .
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

              Figure 5: S46 IPv4/IPv6 Address Binding Option

   o  option-code: OPTION_S46_V4V6BIND (TBD4)

   o  option-length: length of the option, excluding option-code and
      option-length fields, including length of all encapsulated
      options, expressed in bytes.




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   o  ipv4-address: A fixed field of 4 octets specifying an IPv4
      address.

   o  bindprefix6-len: 8 bits long field expressing the bit mask length
      of the IPv6 prefix specified in the bind-ipv6-prefix field.

   o  bind-ipv6-prefix: a variable length field specifying the IPv6
      prefix or address for the S46 CE.  This field is right padded with
      zeros to the nearest octet boundary when bindprefix6-len is not
      divisible by 8.

   o  S46_V4V6BIND-options: a variable field that may contain zero or
      more options that specify additional parameters.  This document
      specifies one such option, OPTION_S46_PORTPARAMS.

4.5.  S46 Port Parameters Option

   The Port Parameters Option (OPTION_S46_PORTPARAMS) specifies optional
   Port Set information that MAY be provided to CEs.

   See [I-D.ietf-softwire-map], Section 5.1 for a description of MAP
   algorithm, explaining all of the parameters in detail.

      0                   1                   2                   3
      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_S46_PORTPARAMS     |         option-length         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |   offset      |    PSID-len   |              PSID             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                   Figure 6: S46 Port Parameters Option

   o  option-code: OPTION_S46_PORTPARAMS (TBD5)

   o  option-length: 4

   o  offset: (PSID offset) 8 bits long field that specifies the numeric
      value for the S46 algorithm's excluded port range/offset bits
      (a-bits), as per section 5.1.1 of [I-D.ietf-softwire-map].
      Allowed values are between 0 and 15.  Default values for this
      field are specific to the softwire mechanism being implemented and
      are defined in the relevant specification document.

   o  PSID-len: Bit length value of the number of significant bits in
      the PSID field. (also known as 'k').  When set to 0, the PSID
      field is to be ignored.  After the first 'a' bits, there are k
      bits in the port number representing the value of the Port Set



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      Identifier (PSID).  Consequently, the address sharing ratio would
      be 2^k.

   o  PSID: Explicit 16-bit (unsigned word) PSID value.  The PSID value
      algorithmically identifies a set of ports assigned to a CE.  The
      first k bits on the left of this field contain the PSID value.
      The remaining (16-k) bits on the right are padding zeros.

   When receiving the OPTION_S46_PORTPARAMS option with an explicit
   PSID, the client MUST use this explicit PSID in configuring its
   softwire interface.  The OPTION_S46_PORTPARAMS option with an
   explicit PSID MUST be discarded if the S46 CE isn't configured with a
   full IPv4 address (e.g. IPv4 prefix).

   The OPTION_S46_PORTPARAMS option with an explicit PSID MUST be
   discarded if the S46 CE isn't configured with a full IPv4 address
   (e.g. IPv4 prefix).

   The OPTION_S46_PORTPARAMS option is contained within an
   OPTION_S46_RULE option or an OPTION_S46_V4V6BIND option.

5.  Softwire46 Containers

5.1.  Softwire46 MAP-E Container Option

   The MAP-E Container Option (OPTION_S46_CONT_MAPE) specifies the
   container used to group all rules and optional port parameters for a
   specified domain.

      0                   1                   2                   3
      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_S46_CONT_MAPE   |         option-length         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     .            encapsulated-options (variable length)             .
     .                                                               .
     +---------------------------------------------------------------+

                     Figure 7: MAP-E Container Option

   o  option-code: OPTION_S46_CONT_MAPE (TBD6)

   o  option-length: Length of encapsulated options

   o  encapsulated-options: options associated with this Softwire46
      MAP-E domain.




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   The encapsulated options field conveys options specific to the
   OPTION_S46_CONT_MAPE.  Currently there are two sub-options specified,
   OPTION_S46_RULE and OPTION_S46_BR.  There MUST be at least one
   OPTION_S46_RULE option and at least one OPTION_S46_BR option.

   Other options applicable to a domain may be defined in the future.  A
   DHCP message MAY include multiple OPTION_S46_CONT_MAPE options
   (representing multiple domains).

5.2.  Softwire46 MAP-T Container Option

   The MAP-T Container option (OPTION_S46_CONT_MAPT) specifies the
   container used to group all rules and optional port parameters for a
   specified domain.

      0                   1                   2                   3
      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_S46_CONT_MAPT      |         option-length         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     .            encapsulated-options (variable length)             .
     .                                                               .
     +---------------------------------------------------------------+

                     Figure 8: MAP-E Container Option

   o  option-code: OPTION_S46_CONT_MAPT (TBD7)

   o  option-length: Length of encapsulated options

   o  encapsulated-options: options associated with this Softwire46
      MAP-T domain.

   The encapsulated options field conveys options specific to the
   OPTION_S46_CONT_MAPT option.  Currently there are two options
   specified, the OPTION_S46_RULE and OPTION_S46_DMR options.  There
   MUST be at least one OPTION_S46_RULE option and exactly one
   OPTION_S46_DMR option.

5.3.  Softwire46 LightWeight 46 Container Option

   The LW46 Container option (OPTION_S46_CONT_LW) specifies the
   container used to group all rules and optional port parameters for a
   specified domain.

      0                   1                   2                   3
      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



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     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |      OPTION_S46_CONT_LW       |         option-length         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     +            encapsulated-options (variable length)             .
     .                                                               .
     +---------------------------------------------------------------+

                      Figure 9: LW46 Container Option

   o  option-code: OPTION_S46_CONT_LW (TBD8)

   o  option-length: Length of encapsulated options

   o  encapsulated-options: options associated with this Softwire46
      domain.

   The encapsulated options field conveys options specific to the
   OPTION_S46_CONT_LW option.  Currently there are two options
   specified, OPTION_S46_V4V6BIND and OPTION_S46_BR.  There MUST be at
   most one OPTION_S46_V4V6BIND option and at least one OPTION_S46_BR
   option.

6.  Softwire46 Options Formatting

   The below table shows which sub-options are mandatory, optional or
   not permitted for each defined container option.

      +-----------------------+-------+-------+--------------------+
      | Option                | MAP-E | MAP-T | Lightweight 4over6 |
      +-----------------------+-------+-------+--------------------+
      | OPTION_S46_RULE       |   M   |   M   |        N/A         |
      |                       |       |       |                    |
      | OPTION_S46_BR         |   M   |  N/A  |         M          |
      |                       |       |       |                    |
      | OPTION_S46_PORTPARAMS |   O   |   O   |         O          |
      |                       |       |       |                    |
      | OPTION_S46_DMR        |  N/A  |   M   |        N/A         |
      |                       |       |       |                    |
      | OPTION_S46_V4V6BIND   |  N/A  |  N/A  |         O          |
      +-----------------------+-------+-------+--------------------+

             M - Mandatory, O - Optional, N/A - Not Applicable

                   Table 1: Option to Container Mappings

   MAP-DHCP clients that receive container options that violate any of
   the above rules MUST silently ignore such container options.



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7.  DHCPv6 Server Behavior

   [RFC3315] Section 17.2.2 describes how a DHCPv6 client and server
   negotiate configuration values using the ORO.  As a convenience to
   the reader, we mention here that by default, a server will not reply
   with a Softwire46 Container Option if the client has not explicitly
   enumerated one in its Option Request Option.

   A CE router may support several (or all) of the mechanisms mentioned
   here.  In the case where a client requests multiple mechanisms in its
   ORO option, the server will reply with the corresponding Softwire46
   Container options for which it has configuration information.

8.  DHCPv6 Client Behavior

   An S46 CE acting as DHCPv6 client will request S46 configuration
   parameters from the DHCPv6 server located in the IPv6 network.  Such
   a client MUST request the S46 Container option(s) that it is
   configured for in its ORO in SOLICIT, REQUEST, RENEW, REBIND and
   INFORMATION-REQUEST messages.

   When processing received S46 container options the following
   behaviour is expected:

   o  A client MUST support processing multiple received OPTION_S46_RULE
      options in a container OPTION_S46_CONT_MAPE or
      OPTION_S46_CONT_MAPT option

   o  A client receiving an unsupported S46 option, or an invalid
      parameter value SHOULD discard that S46 Container option and log
      the event.

   The behavior of a client supporting multiple Softwire46 mechanisms,
   is out of scope of this document.  [I-D.ietf-softwire-unified-cpe]
   describes client behaviour for the prioritization and handling of
   multiple mechanisms simultaneously.

   Note that system implementing CE functionality may have multiple
   network interfaces, and these interfaces may be configured
   differently; some may be connected to networks using a Softwire46
   mechanism, and some may be connected to networks that are using
   normal dual stack or other means.  The CE should approach this
   specification on an interface-by-interface basis.  For example, if
   the CE system is MAP-E capable and is attached to multiple networks
   that provide the OPTION_S46_CONT_MAPE option, then the CE MUST
   configure MAP-E for each interface separately.





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   Failure modes are out of scope for this document.  Failure recovery
   mechanisms may be defined in the future.  See Section 5 of
   [I-D.ietf-softwire-map] for discussion on valid MAP rule
   combinations.  See Section 11 of [RFC7227], Sections 18.1.3, 18.1.4
   and 19.1 of [RFC3315] for parameters update mechanisms in DHCPv6 that
   can be leveraged to update configuration after a failure.

9.  Security Considerations

   Section 23 of [RFC3315] discusses DHCPv6-related security issues.

   As with all DHCPv6-derived configuration state, it is possible that
   configuration is actually being delivered by a third party (Man In
   The Middle).  As such, there is no basis on which access over MAP or
   lw4o6 can be trusted.  Therefore, softwires should not bypass any
   security mechanisms such as IP firewalls.

   In IPv6-only networks that lack any IPv4 firewalls, a device
   supporting MAP could be tricked into enabling its IPv4 stack and
   direct IPv4 traffic to the attacker, thus exposing itself to
   previously infeasible IPv4 attack vectors.

   Section 11 of [I-D.ietf-softwire-map] discusses security issues of
   the MAP mechanism.

   Readers concerned with security of MAP provisioning over DHCPv6 are
   encouraged to read [I-D.ietf-dhc-sedhcpv6].

10.  IANA Considerations

   IANA is kindly requested to allocate the following DHCPv6 option
   codes:

      TBD1 for OPTION_S46_RULE

      TBD2 for OPTION_S46_BR

      TBD3 for OPTION_S46_DMR

      TBD4 for OPTION_S46_V4V6BIND

      TBD5 for OPTION_S46_PORTPARAMS

      TBD6 for OPTION_S46_CONT_MAPE

      TBD7 for OPTION_S46_CONT_MAPT

      TBD8 for OPTION_S46_CONT_LW



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   All values should be added to the DHCPv6 option code space defined in
   Section 24.3 of [RFC3315].

11.  Acknowledgements

   This document was created as a product of a MAP design team.
   Following people were members of that team: Congxiao Bao, Mohamed
   Boucadair, Gang Chen, Maoke Chen, Wojciech Dec, Xiaohong Deng, Jouni
   Korhonen, Xing Li, Satoru Matsushima, Tomasz Mrugalski, Tetsuya
   Murakami, Jacni Qin, Necj Scoberne, Qiong Sun, Tina Tsou, Dan Wing,
   Leaf Yeh and Jan Zorz.

   The authors would like to thank Bernie Volz and Tom Taylor for their
   insightful comments and suggestions.

12.  References

12.1.  Normative References

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

12.2.  Informative References

   [I-D.ietf-dhc-sedhcpv6]
              Jiang, S., Shen, S., Zhang, D., and T. Jinmei, "Secure
              DHCPv6 with Public Key", draft-ietf-dhc-sedhcpv6-03 (work
              in progress), June 2014.

   [I-D.ietf-softwire-lw4over6]
              Cui, Y., Qiong, Q., Boucadair, M., Tsou, T., Lee, Y., and
              I. Farrer, "Lightweight 4over6: An Extension to the DS-
              Lite Architecture", draft-ietf-softwire-lw4over6-03 (work
              in progress), November 2013.

   [I-D.ietf-softwire-map-t]
              Li, X., Bao, C., Dec, W., Troan, O., Matsushima, S., and
              T. Murakami, "Mapping of Address and Port using
              Translation (MAP-T)", draft-ietf-softwire-map-t-04 (work
              in progress), September 2013.

   [I-D.ietf-softwire-map]
              Troan, O., Dec, W., Li, X., Bao, C., Matsushima, S.,
              Murakami, T., and T. Taylor, "Mapping of Address and Port



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              with Encapsulation (MAP)", draft-ietf-softwire-map-08
              (work in progress), August 2013.

   [I-D.ietf-softwire-unified-cpe]
              Boucadair, M., Farrer, I., Perreault, S., and S.
              Sivakumar, "Unified IPv4-in-IPv6 Softwire CPE", draft-
              ietf-softwire-unified-cpe-01 (work in progress), May 2013.

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

   [RFC2473]  Conta, A. and S. Deering, "Generic Packet Tunneling in
              IPv6 Specification", RFC 2473, December 1998.

   [RFC6145]  Li, X., Bao, C., and F. Baker, "IP/ICMP Translation
              Algorithm", RFC 6145, April 2011.

   [RFC7227]  Hankins, D., Mrugalski, T., Siodelski, M., Jiang, S., and
              S. Krishnan, "Guidelines for Creating New DHCPv6 Options",
              BCP 187, RFC 7227, May 2014.

Authors' Addresses

   Tomasz Mrugalski
   Internet Systems Consortium, Inc.
   950 Charter Street
   Redwood City, CA  94063
   USA

   Phone: +1 650 423 1345
   Email: tomasz.mrugalski@gmail.com
   URI:   http://www.isc.org/


   Ole Troan
   Cisco Systems, Inc.
   Philip Pedersens vei 1
   Lysaker  1366
   Norway

   Email: ot@cisco.com










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   Ian Farrer
   Deutsche Telekom AG
   CTO-ATI, Landgrabenweg 151
   Bonn, NRW  53227
   Germany

   Email: ian.farrer@telekom.de


   Simon Perreault
   Viagenie
   246 Aberdeen
   Quebec, QC  G1R 2E1
   Canada

   Phone: +1 418 656 9254
   Email: simon.perreault@viagenie.ca


   Wojciech Dec
   Cisco Systems, Inc.
   The Netherlands

   Email: wdec@cisco.com
   URI:   http://cisco.com


   Congxiao Bao
   CERNET Center/Tsinghua University
   Room 225, Main Building, Tsinghua University
   Beijing  100084
   CN

   Phone: +86 10-62785983
   Email: congxiao@cernet.edu.cn


   Leaf Y. Yeh
   CNNIC
   4, South 4th Street, Zhong_Guan_Cun
   Beijing  100190
   P. R. China

   Email: leaf.yeh.sdo@gmail.com







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   Xiaohong Deng
   6 Floor, C Block, DaCheng International Center Chaoyang District
   Beijing  100124
   China

   Phone: +61 3858 3128
   Email: dxhbupt@gmail.com












































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