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rfc:rfc7598

Internet Engineering Task Force (IETF) T. Mrugalski Request for Comments: 7598 ISC Category: Standards Track O. Troan ISSN: 2070-1721 Cisco Systems

                                                             I. Farrer
                                                   Deutsche Telekom AG
                                                          S. Perreault
                                                   Jive Communications
                                                                W. Dec
                                                         Cisco Systems
                                                                C. Bao
                                                   Tsinghua University
                                                                L. Yeh
                                               Freelancer Technologies
                                                               X. Deng
                                     The University of New South Wales
                                                             July 2015
        DHCPv6 Options for Configuration of Softwire Address
                      and Port-Mapped Clients

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 plus Port (A+P) for providing IPv4
 connectivity across an IPv6 network.

Status of This Memo

 This is an Internet Standards Track document.
 This document is a product of the Internet Engineering Task Force
 (IETF).  It represents the consensus of the IETF community.  It has
 received public review and has been approved for publication by the
 Internet Engineering Steering Group (IESG).  Further information on
 Internet Standards is available in Section 2 of RFC 5741.
 Information about the current status of this document, any errata,
 and how to provide feedback on it may be obtained at
 http://www.rfc-editor.org/info/rfc7598.

Mrugalski, et al. Standards Track [Page 1] RFC 7598 DHCPv6 for Softwire 46 CEs July 2015

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 ....................................................3
 2. Conventions .....................................................3
 3. Softwire46 Overview .............................................4
 4. Common Softwire46 DHCPv6 Options ................................5
    4.1. S46 Rule Option ............................................5
    4.2. S46 BR Option ..............................................7
    4.3. S46 DMR Option .............................................8
    4.4. S46 IPv4/IPv6 Address Binding Option .......................9
    4.5. S46 Port Parameters Option ................................10
 5. Softwire46 Containers ..........................................11
    5.1. S46 MAP-E Container Option ................................11
    5.2. S46 MAP-T Container Option ................................12
    5.3. S46 Lightweight 4over6 Container Option ...................13
 6. Softwire46 Options Encapsulation ...............................14
 7. DHCPv6 Server Behavior .........................................14
 8. DHCPv6 Client Behavior .........................................14
 9. Security Considerations ........................................15
 10. IANA Considerations ...........................................16
 11. References ....................................................16
    11.1. Normative References .....................................16
    11.2. Informative References ...................................17
 Acknowledgements ..................................................18
 Authors' Addresses ................................................19

Mrugalski, et al. Standards Track [Page 2] RFC 7598 DHCPv6 for Softwire 46 CEs July 2015

1. Introduction

 A number of architectural solution proposals discussed in the IETF
 Softwire Working Group use Address plus Port (A+P) [RFC6346] as their
 technology base for providing IPv4 connectivity to end users using
 Customer Edge (CE) devices across a service provider's IPv6 network,
 while allowing for shared or dedicated IPv4 addressing of CEs.
 An example is Mapping of Address and Port with Encapsulation (MAP-E)
 as defined in [RFC7597].  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 information will continue to
 use DHCPv4 [RFC2131].
 This memo specifies a set of DHCPv6 [RFC3315] options to provision
 Softwire46 configuration 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 for
 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].

Mrugalski, et al. Standards Track [Page 3] RFC 7598 DHCPv6 for Softwire 46 CEs July 2015

3. Softwire46 Overview

 This document describes a set of common DHCPv6 options for
 configuring the Mapping of Address and Port with Encapsulation
 (MAP-E) [RFC7597], Mapping of Address and Port using Translation
 (MAP-T) [RFC7599], and Lightweight 4over6 [RFC7596] mechanisms.  For
 definitions of the terminology used in this document, please see the
 relevant terminology sections in [RFC7597], [RFC7599], and [RFC7596].
 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
 MAP-E and MAP-T is that they use different means to connect to the
 IPv6 domain.  MAP-E uses IPv4-over-IPv6 tunneling [RFC2473], while
 MAP-T uses IPv4-to-IPv6 translation based on [RFC6145].  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 DHCPv6 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 (ORO) [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.  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 appear
 only within the container options.  Softwire46 DHCPv6 clients that
 receive provisioning options that are not encapsulated in container
 options MUST silently ignore these options.  DHCPv6 server
 administrators are advised to ensure that DHCPv6 servers are
 configured to send these options in the proper encapsulation.

Mrugalski, et al. Standards Track [Page 4] RFC 7598 DHCPv6 for Softwire 46 CEs July 2015

 This document is organized with the common encapsulated options
 described first (Section 4), followed by the three container options
 (Section 5).  Some encapsulated options are mandatory in some
 containers, some are optional, and some are not permitted.  This is
 shown in Table 1 (Section 6).

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 subsections.
 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 option, 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 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 the OPTION_S46_PORTPARAMS option to
 specify parameters and port sets for the port-range algorithm.
 Softwire46 options use addresses rather than Fully Qualified Domain
 Names (FQDNs).  For the 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 send those options, encapsulated in their
 respective container options, with specific values as hints for the
 server.  See Section 5 for details.  Depending on the server
 configuration and policy, it may accept or ignore the hints.  Clients
 MUST be able to process received values that are different than the
 hints it sent earlier.

Mrugalski, et al. Standards Track [Page 5] RFC 7598 DHCPv6 for Softwire 46 CEs July 2015

    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 (89)
 o  option-length: length of the option, excluding option-code and
    option-length fields, including length of all encapsulated
    options; expressed in octets.
 o  flags: 8 bits long; carries flags applicable to the rule.  The
    meanings of the specific bits are explained in Figure 2.
 o  ea-len: 8 bits long; specifies the Embedded Address (EA) bit
    length.  Allowed values range from 0 to 48.
 o  prefix4-len: 8 bits long; expresses the prefix length of the
    Rule IPv4 prefix specified in the ipv4-prefix field.  Allowed
    values range from 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; expresses the length of the
    Rule IPv6 prefix specified in the ipv6-prefix field.  Allowed
    values range from 0 to 128.
 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.

Mrugalski, et al. Standards Track [Page 6] RFC 7598 DHCPv6 for Softwire 46 CEs July 2015

 o  S46_RULE-options: a variable-length 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 an 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 is determined by a longest-prefix match of
    the Rule IPv6 prefix against the End-user IPv6 prefix(es).
 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 3 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 (90)
 o  option-length: 16

Mrugalski, et al. Standards Track [Page 7] RFC 7598 DHCPv6 for Softwire 46 CEs July 2015

 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)                   |
   .                                                               .
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                       Figure 4: S46 DMR Option
 o  option-code: OPTION_S46_DMR (91)
 o  option-length: 1 + length of dmr-ipv6-prefix specified in octets.
 o  dmr-prefix6-len: 8 bits long; expresses the bitmask length of the
    IPv6 prefix specified in the dmr-ipv6-prefix field.  Allowed
    values range from 0 to 128.
 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.

Mrugalski, et al. Standards Track [Page 8] RFC 7598 DHCPv6 for Softwire 46 CEs July 2015

4.4. S46 IPv4/IPv6 Address Binding Option

 The S46 IPv4/IPv6 Address Binding 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 (92)
 o  option-length: length of the option, excluding option-code and
    option-length fields, including length of all encapsulated
    options; expressed in octets.
 o  ipv4-address: a fixed-length field of 4 octets specifying an IPv4
    address.
 o  bindprefix6-len: 8 bits long; expresses the bitmask length of the
    IPv6 prefix specified in the bind-ipv6-prefix field.  Allowed
    values range from 0 to 128.
 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-length field that may contain
    zero or more options that specify additional parameters.  This
    document specifies one such option: OPTION_S46_PORTPARAMS.

Mrugalski, et al. Standards Track [Page 9] RFC 7598 DHCPv6 for Softwire 46 CEs July 2015

4.5. S46 Port Parameters Option

 The S46 Port Parameters option (OPTION_S46_PORTPARAMS) specifies
 optional port set information that MAY be provided to CEs.
 See Section 5.1 of [RFC7597] for a description of the MAP algorithm
 and detailed explanation of all of the parameters.
    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 (93)
 o  option-length: 4
 o  offset: Port Set Identifier (PSID) offset.  8 bits long; specifies
    the numeric value for the S46 algorithm's excluded port range/
    offset bits (a-bits), as per Section 5.1 of [RFC7597].  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: 8 bits long; specifies 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 PSID.  Consequently,
    the address-sharing ratio would be 2^k.
 o  PSID: 16 bits long.  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 binary 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 when 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 is contained within an
 OPTION_S46_RULE option or an OPTION_S46_V4V6BIND option.

Mrugalski, et al. Standards Track [Page 10] RFC 7598 DHCPv6 for Softwire 46 CEs July 2015

5. Softwire46 Containers

5.1. S46 MAP-E Container Option

 The S46 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: S46 MAP-E Container Option
 o  option-code: OPTION_S46_CONT_MAPE (94)
 o  option-length: length of encapsulated options, expressed in
    octets.
 o  encapsulated-options: options associated with this Softwire46
    MAP-E domain.
 The encapsulated-options field conveys options specific to the
 OPTION_S46_CONT_MAPE option.  Currently, there are two encapsulated
 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
 DHCPv6 message MAY include multiple OPTION_S46_CONT_MAPE options
 (representing multiple domains).

Mrugalski, et al. Standards Track [Page 11] RFC 7598 DHCPv6 for Softwire 46 CEs July 2015

5.2. S46 MAP-T Container Option

 The S46 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: S46 MAP-T Container Option
 o  option-code: OPTION_S46_CONT_MAPT (95)
 o  option-length: length of encapsulated options, expressed in
    octets.
 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.

Mrugalski, et al. Standards Track [Page 12] RFC 7598 DHCPv6 for Softwire 46 CEs July 2015

5.3. S46 Lightweight 4over6 Container Option

 The S46 Lightweight 4over6 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      OPTION_S46_CONT_LW       |         option-length         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   +            encapsulated-options (variable length)             .
   .                                                               .
   +---------------------------------------------------------------+
           Figure 9: S46 Lightweight 4over6 Container Option
 o  option-code: OPTION_S46_CONT_LW (96)
 o  option-length: length of encapsulated options, expressed in
    octets.
 o  encapsulated-options: options associated with this Softwire46
    Lightweight 4over6 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.

Mrugalski, et al. Standards Track [Page 13] RFC 7598 DHCPv6 for Softwire 46 CEs July 2015

6. Softwire46 Options Encapsulation

 The table below shows which encapsulated 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/P         |
    | OPTION_S46_BR         |   M   |  N/P  |         M          |
    | OPTION_S46_PORTPARAMS |   O   |   O   |         O          |
    | OPTION_S46_DMR        |  N/P  |   M   |        N/P         |
    | OPTION_S46_V4V6BIND   |  N/P  |  N/P  |         O          |
    +-----------------------+-------+-------+--------------------+
           M - Mandatory, O - Optional, N/P - Not Permitted
                Table 1: Options for Container Mappings
 Softwire46 DHCPv6 clients that receive container options that violate
 any of the above rules MUST silently ignore such container options.

7. DHCPv6 Server Behavior

 Section 17.2.2 of [RFC3315] describes how a DHCPv6 client and server
 negotiate configuration values using the ORO.  As a convenience for
 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 ORO.
 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, 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 a 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.

Mrugalski, et al. Standards Track [Page 14] RFC 7598 DHCPv6 for Softwire 46 CEs July 2015

 When processing received S46 container options, the following
 behavior 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 that supports multiple Softwire46 mechanisms
 is out of scope for this document.  [Unified-v4-in-v6] describes
 client behavior for the prioritization and handling of multiple
 mechanisms simultaneously.
 Note that a 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.
 Failure modes are out of scope for this document.  Failure recovery
 mechanisms may be defined in the future.  See Section 5 of [RFC7597]
 for a discussion of valid MAP Rule combinations.  See Section 11 of
 [RFC7227] and Sections 18.1.3, 18.1.4, and 19.1 of [RFC3315] for
 parameter-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 states, 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
 Lightweight 4over6 can be trusted.  Therefore, softwires should not
 bypass any security mechanisms such as IP firewalls.
 In IPv6-only networks that lack IPv4 firewalls, a device that
 supports MAP could be tricked into enabling its IPv4 stack and
 directing IPv4 traffic to the attacker, thus exposing itself to
 previously infeasible IPv4 attack vectors.

Mrugalski, et al. Standards Track [Page 15] RFC 7598 DHCPv6 for Softwire 46 CEs July 2015

 Section 10 of [RFC7597] discusses security issues related to the
 MAP-E mechanism, Section 9 of [RFC7596] discusses security issues
 related to the Lightweight 4over6 mechanism, and Section 13 of
 [RFC7599] discusses security issues related to the MAP-T mechanism.
 Readers concerned with the security of Softwire46 provisioning over
 DHCPv6 are encouraged to read [Secure-DHCPv6].

10. IANA Considerations

 IANA has allocated the following DHCPv6 option codes:
    89 for OPTION_S46_RULE
    90 for OPTION_S46_BR
    91 for OPTION_S46_DMR
    92 for OPTION_S46_V4V6BIND
    93 for OPTION_S46_PORTPARAMS
    94 for OPTION_S46_CONT_MAPE
    95 for OPTION_S46_CONT_MAPT
    96 for OPTION_S46_CONT_LW
 All values have been added to the "Dynamic Host Configuration
 Protocol for IPv6 (DHCPv6)" option code space defined in Section 24.3
 of [RFC3315].

11. References

11.1. Normative References

 [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
            Requirement Levels", BCP 14, RFC 2119,
            DOI 10.17487/RFC2119, March 1997,
            <http://www.rfc-editor.org/info/rfc2119>.
 [RFC3315]  Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins,
            C., and M. Carney, "Dynamic Host Configuration Protocol
            for IPv6 (DHCPv6)", RFC 3315, DOI 10.17487/RFC3315,
            July 2003, <http://www.rfc-editor.org/info/rfc3315>.

Mrugalski, et al. Standards Track [Page 16] RFC 7598 DHCPv6 for Softwire 46 CEs July 2015

11.2. Informative References

 [RFC2131]  Droms, R., "Dynamic Host Configuration Protocol",
            RFC 2131, DOI 10.17487/RFC2131, March 1997,
            <http://www.rfc-editor.org/info/rfc2131>.
 [RFC2473]  Conta, A. and S. Deering, "Generic Packet Tunneling in
            IPv6 Specification", RFC 2473, DOI 10.17487/RFC2473,
            December 1998, <http://www.rfc-editor.org/info/rfc2473>.
 [RFC6145]  Li, X., Bao, C., and F. Baker, "IP/ICMP Translation
            Algorithm", RFC 6145, DOI 10.17487/RFC6145, April 2011,
            <http://www.rfc-editor.org/info/rfc6145>.
 [RFC6346]  Bush, R., Ed., "The Address plus Port (A+P) Approach to
            the IPv4 Address Shortage", RFC 6346,
            DOI 10.17487/RFC6346, August 2011,
            <http://www.rfc-editor.org/info/rfc6346>.
 [RFC7227]  Hankins, D., Mrugalski, T., Siodelski, M., Jiang, S., and
            S. Krishnan, "Guidelines for Creating New DHCPv6 Options",
            BCP 187, RFC 7227, DOI 10.17487/RFC7227, May 2014,
            <http://www.rfc-editor.org/info/rfc7227>.
 [RFC7596]  Cui, Y., Sun, Q., Boucadair, M., Tsou, T., Lee, Y., and
            I. Farrer, "Lightweight 4over6: An Extension to the
            Dual-Stack Lite Architecture", RFC 7596,
            DOI 10.17487/RFC7596, July 2015,
            <http://www.rfc-editor.org/info/rfc7596>.
 [RFC7597]  Troan, O., Ed., Dec, W., Li, X., Bao, C., Matsushima, S.,
            Murakami, T., and T. Taylor, Ed., "Mapping of Address and
            Port with Encapsulation (MAP-E)", RFC 7597,
            DOI 10.17487/RFC7597, July 2015,
            <http://www.rfc-editor.org/info/rfc7597>.
 [RFC7599]  Li, X., Bao, C., Dec, W., Ed., Troan, O., Matsushima, S.,
            and T. Murakami, "Mapping of Address and Port using
            Translation (MAP-T)", RFC 7599, DOI 10.17487/RFC7599,
            July 2015, <http://www.rfc-editor.org/info/rfc7599>.

Mrugalski, et al. Standards Track [Page 17] RFC 7598 DHCPv6 for Softwire 46 CEs July 2015

 [Secure-DHCPv6]
            Jiang, S., Ed., Shen, S., Zhang, D., and T. Jinmei,
            "Secure DHCPv6", Work in Progress,
            draft-ietf-dhc-sedhcpv6-08, June 2015.
 [Unified-v4-in-v6]
            Boucadair, M., Farrer, I., Perreault, S., Ed., and S.
            Sivakumar, Ed., "Unified IPv4-in-IPv6 Softwire CPE", Work
            in Progress, draft-ietf-softwire-unified-cpe-01, May 2013.

Acknowledgements

 This document was created as a product of a MAP design team.  The
 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, Tomek 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.

Mrugalski, et al. Standards Track [Page 18] RFC 7598 DHCPv6 for Softwire 46 CEs July 2015

Authors' Addresses

 Tomek Mrugalski
 Internet Systems Consortium, Inc.
 950 Charter Street
 Redwood City, CA  94063
 United States
 Phone: +1 650 423 1345
 Email: tomasz.mrugalski@gmail.com
 URI:   http://www.isc.org/
 Ole Troan
 Cisco Systems
 Philip Pedersens vei 1
 Lysaker  1366
 Norway
 Email: ot@cisco.com
 Ian Farrer
 Deutsche Telekom AG
 CTO-ATI, Landgrabenweg 151
 Bonn, NRW  53227
 Germany
 Email: ian.farrer@telekom.de
 Simon Perreault
 Jive Communications
 Quebec, QC
 Canada
 Email: sperreault@jive.com
 Wojciech Dec
 Cisco Systems, Inc.
 The Netherlands
 Email: wdec@cisco.com
 URI:   http://cisco.com

Mrugalski, et al. Standards Track [Page 19] RFC 7598 DHCPv6 for Softwire 46 CEs July 2015

 Congxiao Bao
 CERNET Center/Tsinghua University
 Room 225, Main Building, Tsinghua University
 Beijing  100084
 China
 Phone: +86 10-62785983
 Email: congxiao@cernet.edu.cn
 Leaf Y. Yeh
 Freelancer Technologies
 China
 Email: leaf.y.yeh@hotmail.com
 Xiaohong Deng
 The University of New South Wales
 Sydney  NSW 2052
 Australia
 Email: dxhbupt@gmail.com
 URI:   https://www.unsw.edu.au/

Mrugalski, et al. Standards Track [Page 20]

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