Softwire WG I. Farrer
Internet-Draft Deutsche Telekom AG
Intended status: Standards Track Q. Sun
Expires: April 3, 2015 Y. Cui
Tsinghua University
September 30, 2014
DHCPv4 over DHCPv6 Source Address Option
draft-fsc-softwire-dhcp4o6-saddr-opt-01
Abstract
DHCPv4 over DHCPv6 [RFC7341] describes a mechanism for dynamically
configuring IPv4 over an IPv6-only network. For DHCPv4 over DHCPv6
to function with some IPv4-over-IPv6 softwire mechanisms, the
operator must obtain information about the IPv4 address and Port Set
ID allocated to the DHCP 4o6 client, as well as the /128 IPv6 prefix
that the client will use as the source of IPv4-in-IPv6 tunnel. This
memo defines a DHCPv6 container option and two DHCPv6 sub-options
used to communicate the source tunnel IPv6 address between the DHCP
4o6 client and server. It is designed to work in conjunction with
the IPv4 address allocation process.
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
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 3, 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
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3
3. Solution Overview . . . . . . . . . . . . . . . . . . . . . . 3
4. IPv6/IPv4 Binding Message Flow . . . . . . . . . . . . . . . 4
5. DHCPv6 Options . . . . . . . . . . . . . . . . . . . . . . . 6
5.1. DHCPv4 over DHCPv6 Source Address Hint Option . . . . . . 6
5.2. DHCPv4 over DHCPv6 Source Address Option . . . . . . . . 6
5.3. DHCPv4 over DHCPv6 Softwire Container Option . . . . . . 7
6. Security Considerations . . . . . . . . . . . . . . . . . . . 7
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
9.1. Normative References . . . . . . . . . . . . . . . . . . 7
9.2. Informative References . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
Deterministic IPv4-over-IPv6 transition technologies are prescriptive
in the location of the tunnel endpoint within the home network. The
tunnel endpoint should usually be configured on either the home
gateway device, or sourced from a specific IPv6 tunnel prefix
allocated to the home network (and in some cases, both).
[I-D.ietf-softwire-map-dhcp] describes a DHCPv6 based mechanism for
provisioning such deterministic softwires.
This document describes a mechanism for informing the service
provider of the binding between the dynamically allocated IPv4
address and Port Set ID (learnt through DHCPv4 over DHCPv6) and the
IPv6 address that the Softwire Initiator will use for accessing IPv4-
over-IPv6 services. It is used with DHCPv4 over DHCPv6 [RFC7341]
message flows to communicate the binding over the IPv6-only network.
The service provider can then use this binding information to
provision other functional elements in their network accordingly,
e.g. using the client's binding information to synchronise the
binding table in the border router.
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The mechanism allows much more flexibility in the location of the
IPv4-over-IPv6 tunnel endpoint, as the IPv6 address is dynamically
signalled back to the service provider. The DHCP 4o6 client and
tunnel client could be run on end devices attached to any routable
IPv6 prefix allocated to an end-user, located anywhere within an
arbitrary home network topology.
This memo describes extensions to [I-D.ietf-softwire-map-dhcp] to
enable the provisioning and tunnel management of softwire initiators
configured through DHCPv4 over DHCPv6.
Current mechanisms suitable for extending to incorporate DHCPv4 over
DHCPv6 with dynamic IPv4 address leasing include
[I-D.ietf-softwire-map] and [I-D.ietf-softwire-lw4over6].
2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
3. Solution Overview
The solution in this document extends the Softwire46 container
approach described in [I-D.ietf-softwire-map-dhcp] by defining a new
container type: OPTION_S46_CONT_DHCP4O6. The container is used to
carry the sub-options necessary for softwire configuration. A client
can indicate its support for dynamic softwire configuration by
including the OPTION_S46_CONT_DHCP4O6 option code within the Option
Request Option.
Two new DHCPv6 sub-options are also defined in this memo:
OPTION_DHCP4O6_SADDR_HINT and OPTION_DHCP4O6_SADDR. They are
intended to be used alongside the normal DHCPv4 IPv4 address
allocation message flow in the context of DHCPv4 over DHCPv6
[RFC7341].
The communication of parameters between the client and server is two-
way: OPTION_DHCP4O6_SADDR_HINT can be (optionally) used by the DHCP
4o6 server to optionally indicate to the client a preferred IPv6
prefix for binding the received IPv4 configuration and sourcing
tunnel traffic. This may be necessary if there are multiple IPv6
prefixes in use in the customer network, or if the specific IPv4-
over-IPv6 transition mechanism requires the use of a particular
prefix for any reason. When the client has selected the IPv6 address
to bind the IPv4 configuration to, it passes the address back to the
DHCP 4o6 server through OPTION_DHCP4O6_SADDR.
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A softwire client also requires an address (or addresses) for the
Border Router (softwire tunnel concentrator). This is used as the
destination address for the client's IPv4-in-IPv6 encapsulated
traffic. Section 4.2 of [I-D.ietf-softwire-map-dhcp] describes the
OPTION_S46_BR option. This option SHOULD be included as an
encapsulated option within OPTION_S46_CONT_DHCP4O6.
This mechanism MUST be used with DHCPv4 over DHCPv6. The DHCP client
MUST request the 4o6 Server Address option first to get DHCPv4 over
DHCPv6 enabled, as in [RFC7341]. Then the OPTION_S46_CONT_DHCP4O6
MAY be included in DHCPv4-query and DHCPv4-response messages. If the
IPv6 source address of the client changes (such as IPv6 lease
expiration, etc.), the client follows the Section 9 of [RFC7341] to
reenable the DHCPv4-over-DHCPv6 function.
If OPTION_S46_CONT_DHCP4O6 is used, the option (as well as any
suboption(s) it contains) MUST be transported in the DHCPv4-query and
DHCPv4-response messages [RFC7341].
4. IPv6/IPv4 Binding Message Flow
The following diagram shows the client/server message flow and how
the OPTION_S46_CONT_DHCP4O6 container and its sub-options are used.
In each step, the relevant DHCPv4 message is given above the arrow
and the relevant options below the arrow. The DHCPv4 messages are
encapsulated in DHCPv4-query or DHCPv4-response message, and those
options are included in the 'options' field of the DHCPv4-query or
DHCPv4-response message.
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DHCP 4o6 DHCP 4o6
Client Server
| DHCPDISCOVER (DHCPv4) |
Step 1 |----------------------------------------------------->|
| ORO with OPTION_S46_CONT_DHCP4O6 (DHCPv6) |
| |
| DHCPOFFER (DHCPv4) |
Step 2 |<-----------------------------------------------------|
| OPTION_S46_CONT_DHCP4O6 containing OPTION_S46_BR, |
| OPTION_DHCP4O6_SADDR_HINT (cipv6-prefix-hint with |
| service provider's preferred prefix) (DHCPv6) |
| |
| DHCPREQUEST (DHCPv4) |
Step 3 |----------------------------------------------------->|
| OPTION_S46_CONT_DHCP4O6 containing OPTION_S46_BR, |
| OPTION_DHCP4O6_SADDR (cipv6-bound-prefix with |
| client's bound /128 IPv6 address) (DHCPv6) |
| |
| DHCPACK (DHCPv4) |
Step 4 |<-----------------------------------------------------|
| OPTION_S46_CONT_DHCP4O6 containing OPTION_S46_BR, |
| OPTION_DHCP4O6_SADDR (cipv6-bound-prefix with |
| client's bound /128 IPv6 prefix) (DHCPv6) |
| |
IPv6/IPv4 Binding Message Flow
The DHCP 4o6 Server and Client MAY implement the
OPTION_S46_CONT_DHCP4O6 option and its sub-options. A client that
intends to dynamically configure softwires SHOULD include the option
code for OPTION_S46_CONT_DHCP4O6 in the DHCPv6 ORO alongside the
DHCPv4 DHCPDISCOVER message. This container option MUST be present,
along with relevant sub-options, in all subsequent DHCPv4 over DHCPv6
transactions for the lifetime of the IPv4 address lease.
OPTION_S46_BR SHOULD also be included in the container.
When a DHCP 4o6 Server replies with a DHCPOFFER message, it SHOULD
include an OPTION_S46_CONT_DHCP4O6 option containing OPTION_S46_BR.
It MAY also include OPTION_DHCP4O6_SADDR_HINT. The
OPTION_DHCP4O6_SADDR_HINT is used by the server to indicate a
preferred prefix that the client should use to bind IPv4
configuration to. If this sub-option is received, the client MUST
perform a longest prefix match between cipv6-prefix-hint and all
configured prefixes on the device. If a match is found, then the
selected prefix MUST then be used to bind the received IPv4
configuration to. If the client doesn't receive the sub-option, or
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the matching fails, the client can select any valid /128 IPv6 prefix
to use.
OPTION_DHCP4O6_SADDR is used by the client to inform the DHCP 4o6
Server which IPv6 prefix the IPv4 configuration has been bound to.
The client MUST put the selected IPv6 address into this sub-option
and include OPTION_S46_CONT_DHCP4O6 in the DHCPv4-response message
when it sends the DHCPREQUEST message.
5. DHCPv6 Options
5.1. DHCPv4 over DHCPv6 Source Address Hint 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_DHCP4O6_SADDR_HINT | option-length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|cipv6-hintlen | |
+-+-+-+-+-+-+-+-+ cipv6-prefix-hint .
. (variable length) .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
o option-code: OPTION_DHCP4O6_SADDR_HINT (TBA1)
o option-length: 1 + length of cipv6-prefix-hint, specified in
bytes.
o cipv6-hintlen: 8-bit field expressing the bit mask length of the
IPv6 prefix specified in cipv6-prefix-hint.
o cipv6-prefix-hint: The IPv6 prefix indicating the preferred prefix
for the client to bind the received IPv4 configuration to.
5.2. DHCPv4 over DHCPv6 Source Address Option
The format of DHCPv4 over DHCPv6 Source address option is defined as
follows:
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_DHCP4O6_SADDR | option-length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ cipv6-src-address +
. (128 bits) .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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o option-code: OPTION_DHCP4O6_SADDR (TBA2)
o option-length: 16.
o cipv6-src-address: The IPv6 address that the client has bound the
allocated IPv4 configuration to.
5.3. DHCPv4 over DHCPv6 Softwire Container Option
The DHCP 4o6 Container option carries the relevant options and
parameters for configuring the client.
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_DHCP4O6 | option-length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| encapsulated-options (variable length) |
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
o option-code: OPTION_S46_CONT_DHCP4O6 (TBA3)
o option-length: length of encapsulated-options (specified in bytes)
o encapsulated-options: options for configuring the DHCP 4o6
Softwire client.
6. Security Considerations
TBD
7. IANA Considerations
IANA is requested to allocate the DHCPv6 option code:
OPTION_DHCP4O6_SADDR_HINT, OPTION_DHCP4O6_SADDR and
OPTION_S46_CONT_DHCP4O6.
8. Acknowledgements
9. References
9.1. Normative References
[I-D.ietf-softwire-map-dhcp]
Mrugalski, T., Troan, O., Farrer, I., Perreault, S., Dec,
W., Bao, C., leaf.yeh.sdo@gmail.com, l., and X. Deng,
"DHCPv6 Options for configuration of Softwire Address and
Port Mapped Clients", draft-ietf-softwire-map-dhcp-08
(work in progress), July 2014.
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[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC7341] Sun, Q., Cui, Y., Siodelski, M., Krishnan, S., and I.
Farrer, "DHCPv4-over-DHCPv6 (DHCP 4o6) Transport", RFC
7341, August 2014.
9.2. Informative References
[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-lw4over6-10 (work
in progress), June 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)", draft-ietf-softwire-map-10
(work in progress), January 2014.
[RFC2131] Droms, R., "Dynamic Host Configuration Protocol", RFC
2131, 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.
Authors' Addresses
Ian Farrer
Deutsche Telekom AG
CTO-ATI, Landgrabenweg 151
Bonn, NRW 53227
Germany
Email: ian.farrer@telekom.de
Qi Sun
Tsinghua University
Beijing 100084
P.R. China
Phone: +86-10-6278-5822
Email: sunqi@csnet1.cs.tsinghua.edu.cn
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Yong Cui
Tsinghua University
Beijing 100084
P.R. China
Phone: +86-10-6260-3059
Email: yong@csnet1.cs.tsinghua.edu.cn
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