Internet Engineering Task Force C. Zhou
Internet-Draft Huawei Technologies
Intended status: Standards Track T. Taylor
Expires: January 22, 2015 PT Taylor Consulting
Q. Sun
China Telecom
M. Boucadair
France Telecom
July 21, 2014

Attribute-Value Pairs For Provisioning Customer Equipment Supporting IPv4-Over-IPv6 Transitional Solutions
draft-zhou-dime-4over6-provisioning-03

Abstract

During the transition from IPv4 to IPv6, customer equipment may have to support one of the various transition methods that have been or are currently being defined for carrying IPv4 packets over IPv6. Work is currently in progress to enumerate the information that needs to be provisioned on a customer edge router to support a list of transition techniques based on tunneling IPv4 in IPv6, with a view to defining reusable components for a reasonable transition path between these techniques. To the extent that the provisioning is done dynamically, AAA support is needed to provide the information to the network server responsible for passing the information to the customer equipment. This document specifies Diameter attribute-value pairs to be used for that purpose.

Status of This Memo

This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.

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This Internet-Draft will expire on January 22, 2015.

Copyright Notice

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Table of Contents

1. Introduction

A number of transition technologies have been or are being defined to allow IPv4 packets to pass between hosts and IPv4 networks over an intervening IPv6 network while minimizing the number of public IPv4 addresses that need to be consumed by the hosts. Different operators will deploy different technologies, and sometimes one operator will use more than one technology, depending on what is supported by the available equipment and upon other factors both technical and economic.

Each technique requires the provisioning of some subscriber-specific information on the customer edge device. The provisioning may be by DHCP or by some other method. This document is indifferent to the specific provisioning technique used, but assumes a deployment in which that information is managed by AAA (Authentication, Authorization, and Accounting) servers. It further assumes that this information is delivered to intermediate network nodes for onward provisioning using the Diameter protocol [RFC6733].

As described below, in the particular case where the Light Weight IPv4 Over IPv6 (LW4o6) [I-D.ietf-softwire-lw4over6] transition method has been deployed, per-subscriber-site information almost identical to that passed to the subscriber site [I-D.ietf-softwire-map-dhcp] or collected from it [I-D.fsc-softwire-dhcp4o6-saddr-opt] also needs to be delivered to the border router serving that site. The Diameter protocol may be used for this purpose too.

This document analyzes the information required to configure the customer edge equipment for the following set of transition methods:

On the basis of that analysis it specifies a number of attribute-value pairs (AVPs) to allow the necessary subscriber-site-specific configuration information to be carried in Diameter.

This document is intended to be complementary to documents such as [RFC6519], [I-D.sun-softwire-lw4over6-radext], and [I-D.ietf-softwire-map-radius] which provide RADIUS attributes to carry similar configuration information for the respective transition methods. Reconciliation of the present document with these other documents is a work in progress.

1.1. 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 [RFC2119].

The abbreviation "CE" denotes the equipment at the customer edge that terminates the customer end of an IPv6 transitional tunnel. This will usually be a router, but could be a host directly connected to the network.

The term "tunnel source address" is used to denote the IPv6 source address used in the outer header of packets sent from the CE through an LW4over6 transitional tunnel to the border router.

2. Description of the Parameters Required By Each Transition Method

This section reviews the parameters that need to be provisioned for each of the transition methods listed above. This enumeration provides the justification for the AVPs defined in the next section. Since two of the three transition methods dealt with here are works in progress, this section is subject to modification in future versions.

A means is required to indicate which transition method(s) a given subscriber is allowed to use. The approach taken in this document is to specify grouped AVPs specific to LW4over6 and MAP-E. The operator can control which of these two transition methods a given subscriber uses by ensuring that AAA passes only the grouped AVP relevant to that method. A grouped AVP is unnecessary for Dual-Stack Lite, since (as the next section indicates) AAA has to provide only one parameter. Hence the absence of either of the grouped AVPs indicates that the subscriber equipment will use Dual-Stack Lite.

2.1. Parameters For Dual-Stack Lite

Dual-Stack Lite is documented in [RFC6333]. The Basic Bridging BroadBand (B4) element at the customer premises needs to be provisioned with the IPv6 address of the AFTR (border router). Optionally, it could also be configured with the IPv4 address of the B4 interface facing the tunnel, where the default value in the absence of provisioning is 192.0.0.2 and valid values are 192.0.0.2 through 192.0.0.7. Provisioning this information through AAA is problematic because it is most likely used in a case where multiple B4 instances occupy the same device. This document therefore assumes that the B4 interface address is determined by other means (implementation-dependent or static assignment).

2.2. Light Weight IPv4 Over IPv6 (LW4over6)

Light Weight IPv4 Over IPv6 (LW4over6) is documented in [I-D.ietf-softwire-lw4over6]. LW4over6 requires four parameters to be provisioned to the customer equipment:

As discussed in Section 4 of [I-D.ietf-softwire-lw4over6], it is necessary to synchronize this configuration with corresponding per-subscriber configuration at the border router. The border router information consists of the same public IPv4 address and port set parameters that are passed to the CE, bound together with the full /128 IPv6 address (not just the Binding Prefix) configured as the tunnel source address at the CE.

[I-D.fsc-softwire-dhcp4o6-saddr-opt] proposes a means whereby a DHCPv6 server can influence the choice of this address and collect it from the CE. Depending on the provisioning architecture deployed in a given network, it is possible that the tunnel source address is passed to AAA as an intermediate step before the binding information is passed on to the border router.

2.3. Mapping of Address and Port with Encapsulation (MAP-E)

Mapping of Address and Port with Encapsulation (MAP-E) is described in [I-D.ietf-softwire-map]. MAP-E requires the provisioning of the following per-subscriber information at the customer edge device:

As indicated in Section 5, bullet 1 of the MAP-E document, a MAP CE can be provisioned with multiple End-user IPv6 prefixes, each associated with its own Basic Mapping Rule. This does not change the basic requirement for representation of the corresponding information in the form of Diameter AVPs, but adds a potential requirement for multiple instances of both types of AVP to be present.

The border router needs to be configured with the superset of the Mapping Rules passed to the customer sites it serves. Since this requirement does not require direct coordination with CE configuration in the way LW4over6 does, it is out of scope of the present document.

2.4. Summary and Discussion

It appears that one item is common to the different transition methods and the corresponding AVP to carry it can be reused:

[RFC6519] sets a precedent for representation of the IPv6 address of a border router as an FQDN. This can be dereferenced to one or more IP addresses by the provisioning system before being passed to the customer equipment, or left as an FQDN as it is in [RFC6334].

The remaining requirements are transition-method-specific:

3. Derived AVP Data Formats: AddressOrPrefix

The above requirements involve IP addresses and prefixes in a number of contexts. To simplify specification of these attributes, this section defines a new derived AVP data format, AddressOrPrefix, according to the rules given in Section 4.3 of [RFC6733].

AddressOrPrefix

4. Attribute-Value Pair Definitions

This section provides the specifications for the AVPs needed to meet the requirements summarized in Section 2.4. Within the context of their usage, all of these AVPs MUST have the M bit set and the V bit cleared.

4.1. Border-Router-Name AVP

Following on the precedent set by [RFC6334] and [RFC6519], this document identifies a border router using an FQDN rather than an address. The Border-Router-Name AVP (AVP Code TBD01) is of type OctetString. The rules for encoding the FQDN are the same as those for the FQDN variant of the derived type DiameterIdentity (Section 4.3.1 of [RFC6733]).

4.2. Tunnel-Source-Pref-Or-Addr AVP

The Tunnel-Source-Pref-Or-Addr AVP (AVP Code TBD02) is of type AddressOrPrefix. It conveys either a prefix or a full address that is configured as the tunnel source address on the CE. Within the scope of application of this document it is intended for use to convey the LW4over6 Binding Prefix from AAA to the provisioning system or to carry a full IPv6 tunnel source address that has been collected from the CE, either from the provisioning system to AAA or from AAA to the border router. This AVP is defined separately from the LW4over6-Binding AVP (which includes it) to provide flexibility in the transport of the tunnel source address from the provisioning system to AAA.

The Tunnel-Endpoint-Pref-Or-Addr AVP

4.3. Port-Set-Identifier

The Port-Set-Identifier AVP (AVP Code TBD03) is a structured OctetString with four octets of data, hence a total AVP length of 12. The description of the structure which follows refers to quantities illustrated in Figure 9, Appendix B of [I-D.ietf-softwire-map]. The derivation of port numbers from these parameters is described in that appendix.

4.4. LW4over6-Binding

The LW4over6-Binding AVP (AVP Code TBD04) is of type Grouped. It contains the elements of configuration that constitute the binding between an LW4over6 tunnel and IPv4 packets sent through that tunnel.

                 LW4over6-Binding  ::= < AVP Header: TBD04 >
                          { Tunnel-Source-Pref-Or-Addr }
                          { LW4over6-External-IPv4-Addr }
                          [ Port-Set-Identifier ]
                         *[ AVP ]
          

Figure 1

The Tunnel-Source-Pref-Or-Addr AVP is defined in Section 4.2 and provides either the Binding Prefix or the full IPv6 tunnel source address. This AVP MUST be present.

The LW4over6-External-IPv4-Addr AVP (AVP Code TBD05) is of type AddressOrPrefix. Within the LW4over6-Binding AVP, it provides the external IPv4 address used as the source address for packets outgoing from the CE through the LW4over6 tunnel associated with the given binding, or destination address for incoming packets. This AVP MUST be present.

The Port-Set-Identifier AVP is defined in Section 4.3. It identifies the specific set of ports assigned to the LW4over6 tunnel. This AVP MUST be present except when 1-1 mapping mode is being provisioned, when it MUST NOT be present.

4.5. MAP-E-Attributes

The MAP-E-Attributes AVP (AVP Code TBD06) is of type Grouped. It contains the configuration data identified in Section 2.3, for a single MAP domain. If a CE belongs to more than one MAP domain, AAA will have to provide an instance of the MAP-E-Attributes AVP for each domain.

                 MAP-E-Attributes  ::= < AVP Header: TBD06 >
                        1*{ Border-Router-Name }
                        1*{ MAP-Mapping-Rule }
                          [ MAP-Mesh-Mode ]
                          [ MAP-End-User-IPv6-Prefix ]
                         *[ AVP ]
          

Figure 2

The Border-Router-Name AVP is defined in Section 4.1. It provides the FQDN of a MAP border relay at the edge of the MAP domain to which the containing MAP-E-Attributes AVP relates. The provisioning system will typically resolve this FQDN into one or more IPv6 addresses before passing it to the CE. At least one instance of this AVP MUST be present.

The MAP-Mapping-Rule AVP is defined in Section 4.6. At least one instance of this AVP MUST be present. If the MAP-E domain supports mesh mode, additional MAP-Mapping-Rule instances MAY be present. If the MAP-E domain is operating in hub-and-spoke mode, additional MAP-Mapping-Rule instances MUST NOT be present.

The MAP-Mesh-Mode AVP (AVP Code TBD07) is of type OctetString but has no data. Hence the AVP length is always 8. The absence of the mesh mode indicator attribute indicates that the CE is required to operate in hub- and-spoke mode.

The MAP-End-User-IPv6-Prefix AVP (AVP Code TBD08) is of type AddressOrPrefix. Within the MAP-E-Attributes AVP, it provides the end- user IPv6 prefix assigned to the CE for the MAP domain to which the containing MAP-E-Attributes AVP relates. This attribute is optional because, depending on deployment, the end-user IPv6 prefix may be provided by AAA or by another support system.

4.6. MAP-Mapping-Rule

The MAP-Mapping-Rule AVP (AVP Code TBD09) is of type Grouped, and is used only in conjunction with MAP-based transition methods (MAP-E and potentially 4rd and MAP-T). Mapping rules are required both by the MAP border relay and by the CE. The components of the MAP-Mapping-Rule AVP provide the contents of a mapping rule as described in Section 2.3.

The syntax of the MAP-Mapping-Rule AVP is as follows:

         MAP-Mapping-Rule  ::= < AVP Header: TBD09 >
                          { Rule-IPv4-Addr-Or-Prefix }
                          { Rule-IPv6-Prefix    }
                          { EA-Field-Length     }
                          [ Port-Set-Identifier ]
                         *[ AVP ]
          

Figure 3

The Rule-IPv4-Addr-Or-Prefix AVP (AVP Code TBD10) is of type AddressOrPrefix. The prefix length can range from 0 to 32, based on the different cases identified in Section 5.2 of [I-D.ietf-softwire-map]. A prefix length of 0 indicates that the entire IPv4 address or prefix is coded in the Extended Address (EA) bits of the end-user IPv6 prefix rather than in the mapping rule. This AVP MUST be present.

The Rule-IPv6-Prefix AVP (AVP Code TBD11) is also of type AddressOrPrefix. The prefix length MUST be less than or equal to the length of the prefix in the MAP-End-User-IPv6-Prefix AVP contained in the same instance of the MAP-E-Attributes AVP as the MAP-Mapping-Rule AVP instance to which the Rule-IPv6-Prefix AVP belongs. The Rule-IPv6-Prefix AVP MUST be present.

The EA-Field-Length AVP (AVP Code TBD12) is of type Unsigned32. Valid values range from 0 to 48. See Section 5.2 of [I-D.ietf-softwire-map] for a description of the use of this parameter in deriving IPv4 address and port number configuration. This AVP MUST be present.

The Port-Set-Identifier AVP is defined in Section 4.3. It MUST be present if the value of EA-Field-Length AVP is 0, and is redundant (SHOULD NOT be present) otherwise.

5. Acknowledgements

Tom Taylor performed work on earlier versions of this document with funding from Huawei Technologies.

6. IANA Considerations

This memo requests to IANA to register the following Diameter AVP codes:

Code Attribute Name Reference
TBD01 Border-Router-Name This document
TBD02 Tunnel-Source-Pref-Or-Addr This document
TBD03 Port-Set-Identifier This document
TBD04 LW4over6-Binding This document
TBD05 LW4over6-External-IPv4-Addr This document
TBD06 MAP-E-Attributes This document
TBD07 MAP-Mesh-Mode This document
TBD08 MAP-End-User-IPv6-Prefix This document
TBD09 MAP-Mapping-Rule This document
TBD10 Rule-IPv4-Addr-Or-Prefix This document
TBD11 Rule-IPv6-Prefix This document
TBD12 EA-Field-Length This document

7. Security Considerations

To come.

8. References

8.1. Normative References

[I-D.ietf-softwire-lw4over6] Cui, Y., Sun, Q., Boucadair, M., Tsou, T., Lee, Y. and I. Farrer, "Lightweight 4over6: An Extension to the DS-Lite Architecture (work in progress)", March 2014.
[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 with Encapsulation (MAP) (work in progress)", January 2014.
[IANAADFAM] , , "Address Family Numbers", .
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC6333] Durand, A., Droms, R., Woodyatt, J. and Y. Lee, "Dual-Stack Lite Broadband Deployments Following IPv4 Exhaustion", RFC 6333, August 2011.
[RFC6733] Fajardo, V., Arkko, J., Loughney, J. and G. Zorn, "Diameter Base Protocol", RFC 6733, October 2012.

8.2. Informative References

[I-D.fsc-softwire-dhcp4o6-saddr-opt] Farrer, I., Sun, Q. and Y. Cui, "DHCPv4 over DHCPv6 Source Address Option (Work in progress)", June 2014.
[I-D.ietf-softwire-map-dhcp] Mrugalski, T., Troan, O., Farrer, I., Perrault, S., Dec, W., Bao, C., Yeh, L. and X. Deng, "DHCPv6 Options for configuration of Softwire Address and Port Mapped Clients (Work in progress)", March 2014.
[I-D.ietf-softwire-map-radius] Jiang, S., Fu, Y., Liu, B. and P. Deacon, "RADIUS Attribute for MAP (Work in progress)", June 2014.
[I-D.sun-softwire-lw4over6-radext] Xie, C., Sun, Q., Sun, Q., Zhou, C., Tsou, T. and Z. Liu, "Radius Extension for Lightweight 4over6 (Work in progress)", March 2014.
[RFC2131] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131, March 1997.
[RFC2865] Rigney, C., Willens, S., Rubens, A. and W. Simpson, "Remote Authentication Dial In User Service (RADIUS)", RFC 2865, June 2000.
[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.
[RFC4607] Holbrook, H. and B. Cain, "Source-Specific Multicast for IP", RFC 4607, August 2006.
[RFC6052] Bao, C., Huitema, C., Bagnulo, M., Boucadair, M. and X. Li, "IPv6 Addressing of IPv4/IPv6 Translators", RFC 6052, October 2010.
[RFC6334] Hankins, D. and T. Mrugalski, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6) Option for Dual-Stack Lite", RFC 6334, August 2011.
[RFC6519] Maglione, R. and A. Durand, "RADIUS Extensions for Dual-Stack Lite", RFC 6519, February 2012.

Authors' Addresses

Cathy Zhou Huawei Technologies Bantian, Longgang District Shenzhen, 518129 P.R. China EMail: cathy.zhou@huawei.com
T. Taylor PT Taylor Consulting Ottawa, Canada EMail: tom.taylor.stds@gmail.com
Qiong Sun China Telecom P.R.China Phone: 86 10 58552936 EMail: sunqiong@ctbri.com.cn
M. Boucadair France Telecom Rennes, 35000 France EMail: mohamed.boucadair@orange.com