DHCPv6 Options for configuration of Softwire Address and Port Mapped Clients
draft-ietf-softwire-map-dhcp-09

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/.

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This Internet-Draft will expire on April 14, 2015.

Copyright Notice

Copyright (c) 2014 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. Conventions
• 3. Softwire46 Overview
• 4. Common Softwire46 DHCPv6 Options
• 4.1. S46 Rule Option
• 4.2. S46 BR Option
• 4.3. S46 DMR Option
• 4.4. S46 IPv4/IPv6 Address Binding Option
• 4.5. S46 Port Parameters Option
• 5. Softwire46 Containers
• 5.1. Softwire46 MAP-E Container Option
• 5.2. Softwire46 MAP-T Container Option
• 5.3. Softwire46 LightWeight 46 Container Option
• 6. Softwire46 Options Formatting
• 7. DHCPv6 Server Behavior
• 8. DHCPv6 Client Behavior
• 9. Security Considerations
• 10. IANA Considerations
• 11. Acknowledgements
• 12. References
• 12.1. Normative References
• 12.2. Informative References
• Authors' Addresses

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.

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 MAP-E and MAP-T is that they use different means to connect to the IPv6 domain. MAP-E uses RFC2473 [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 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.

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

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

 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                          |
|                                                               |
|                                                               |
|                                                               |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

 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)                   |
.                                                               .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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

 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             |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

 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)             .
.                                                               .
+---------------------------------------------------------------+
	

 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)             .
.                                                               .
+---------------------------------------------------------------+
	

 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)             .
.                                                               .
+---------------------------------------------------------------+