Internet DRAFT - draft-mrugalski-softwire-dhcpv4-over-v6-option
draft-mrugalski-softwire-dhcpv4-over-v6-option
Dynamic Host Configuration WG T. Mrugalski
Internet-Draft ISC
Intended status: Standards Track P. Wu
Expires: March 30, 2013 Tsinghua University
September 26, 2012
Dynamic Host Configuration Protocol for IPv6 (DHCPv6) Option for DHCPv4
over IPv6 Endpoint
draft-mrugalski-softwire-dhcpv4-over-v6-option-01
Abstract
[I-D.ietf-dhc-dhcpv4-over-ipv6] defines a way for communication
between legacy DHCPv4 clients with DHCPv4 servers over IPv6-only
transport. It requires deployment of Client Relay Agent (CRA) that
transmits messages to IPv6-Transport Server (TSV) or IPv6-Transport
Relay Agent (TRA). Deployed CRA must know an address of TSV or TRA
to forward incoming client's messages. This document defines a
DHCPv6 option that may be used to provision TSV or TRA location to
CRAs.
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 March 30, 2013.
Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
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carefully, as they describe your rights and restrictions with respect
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Table of Contents
1. Requirements Language . . . . . . . . . . . . . . . . . . . . . 3
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. The DHCPv4-Over-IPv6 Endpoint DHCPv6 Option . . . . . . . . . . 3
4. DHCPv6 Server Behavior . . . . . . . . . . . . . . . . . . . . 4
5. DHCPv6 Client Behavior . . . . . . . . . . . . . . . . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . . 5
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6
9.1. Normative References . . . . . . . . . . . . . . . . . . . 6
9.2. Informative References . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7
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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 RFC 2119 [RFC2119].
2. Introduction
[I-D.ietf-dhc-dhcpv4-over-ipv6] defines a way for communication
between legacy DHCPv4 clients with DHCPv4 servers (defined in
[RFC2131]) over IPv6-only transport. It requires deployment of
Client Relay Agent (CRA) that transmits messages to IPv6-Transport
Server (TSV) or IPv6-Transport Relay Agent (TRA). Although there are
several scenarios envisaged, all of them assume that CRA needs to
know the recipient address of the DHCPv4-over-IPv6 traffic. In a
typical deployment as [I-D.cui-softwire-b4-translated-ds-lite] or
[I-D.ietf-softwire-public-4over6], CRA functionality will be a part
of a Lightweight B4 element (Basic Bridging BroadBand element)
implementation.
Depending on the scenario discussed, the DHCPv4 over IPv6 transport
endpoint could be either an IPv6-Transport Server (TSV) or an IPv6-
Transport Relay Agent (TRA). Both cases are indistinguishable from
CRA perspective. CRA needs to know TSV's or TRA's IPv6 address in
advance to relay traffic. Again, the typical envisaged use would be
the Lightweight 4over6 architecture, where TSV or TRA could be part
of Lightweight AFTR implementation.
As CRA uplink is IPv6-only (otherwise there would be no need to
deploy DHCPv4 over IPv6), the only feasible way to provision
information to CRA is over DHCPv6. Therefore this document specifies
a DHCPv6 option that conveys necessary information.
To provide the conveyance of the configuration information, a single
DHCPv6 [RFC3315] option is used, expressing the TRA's or TSV's IPv6
address to the CRA.
3. The DHCPv4-Over-IPv6 Endpoint DHCPv6 Option
The DHCPv4-over-IPv6 option is a DHCPv6 option. It consists of an
option-code and option-len fields (as all DHCPv6 options have), and a
fixed-length dhcpv4-over-ipv6-endpoint-addr field containing an IPv6
address that refers to the DHCPv4 over IPv6 transport endpoint to
which the CRA MAY transport DHCPv4 traffic. This address represents
TRA or TSV, depending on deployment scenario.
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The DHCPv4-over-IPv6 option SHOULD NOT appear in any other than the
following DHCPv6 messages: Solicit, Advertise, Request, Renew,
Rebind, Information-Request and Reply.
The format of the DHCPv4 over IPv6 option is shown in the following
figure:
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_DHCP4_OVER_V6: (TBD) | option-len |
+-------------------------------+-------------------------------+
| |
| dhcpv4-over-ipv6-endpoint-addr |
| |
+---------------------------------------------------------------+
OPTION_DHCP4_OVER_V6: (TBD)
option-len: 16
dhcpv4-over-ipv6-endpoint-addr: An IPv6 address of the
DHCPv4-over-IPv6 transport endpoint.
Figure 1: AFTR-Name DHCPv6 Option Format
The option is validated by confirming that all of the following
conditions are met:
1. the option-len is exactly 16;
2. the dhcpv4-over-ipv6-endpoint-addr contains valid unicast
address. In particular any address (::), multicast (ff::/8) or
IPv4-mapped IPv6 address is invalid and MUST be rejected.
4. DHCPv6 Server Behavior
A DHCPv6 server SHOULD NOT send more than one DHCPv4-over-IPv6
option. It SHOULD NOT permit the configuration of multiple addresses
within one DHCPv4-over-IPv6 option. Both of these conditions are
handled as errors by the client, so an operator using software that
does not perform these validations should be careful not to configure
multiple addresses.
RFC 3315 Section 17.2.2 [RFC3315] describes how a DHCPv6 client and
server negotiate configuration values using the Option Request Option
(OPTION_ORO). As a convenience to the reader, we mention here that a
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server will not reply with a DHCPv4-over-IPv6 option if the client
has not explicitly enumerated it on its Option Request Option. In
other words, server SHOULD send this option only if client explicitly
requested it in ORO.
5. DHCPv6 Client Behavior
A client that supports the DHCPv4 over IPv6 functionality of and
conforms to this specification MUST include OPTION_DHCP4_OVER_V6 on
its OPTION_ORO.
If the client receives the DHCPv4-over-IPv6 option, it MUST verify
the option contents as described in Section 3.
If the CRA entity receives more than one DHCPv4-over-IPv6 option, it
MUST use only one instance of that option.
If the DHCPv4-over-IPv6 option contains more than one address, the
CRA entity system MUST ignore the option. It SHOULD warn its
operator about such condition.
Note that a CRA system may have multiple network interfaces, and
these interfaces may be configured differently; some may be connected
to networks that call for DHCPv4-over-IPv6, and some may be connected
to networks that are using normal dual stack or other means. The CRA
entity should approach this specification on an interface-by-
interface basis. For example, if the CRA entity is attached to
multiple networks that provide the DHCPv4-over-IPv6 option, then the
CRA entity MUST configure a DHCPv4 over IPv6 transport for each
interface separately as each transport provides IPv4 connectivity for
each distinct interface.
6. Security Considerations
This document does not present any new security issues, but as with
all DHCPv6-derived configuration state, it is completely possible
that the configuration is being delivered by a third party (Man In
The Middle). As such, there is no basis to trust that the access the
DHCPv4-over-IPv6 connection provides can be trusted. It should be
protected by available security mechanisms such as IP firewalls.
It should be noted that DHCPv4 over IPv6 traffic may bypass existing
firewalls that are typically configured to drop incoming outside
DHCPv4 over IPv4 and DHCPv6 over IPv6 traffic.
RFC 3315 [RFC3315] discusses DHCPv6-related security issues.
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[I-D.ietf-dhc-dhcpv4-over-ipv6] discusses DHCPv4-over-IPv6 related
security issues.
7. IANA Considerations
IANA is kindly requested to allocate DHCPv6 option code TBD to the
OPTION_DHCP4_OVER_V6. The value should be added to the DHCPv6 option
code space defined in Section 24.3 of [RFC3315].
8. Acknowledgements
Authors would like to thank nobody so far, as we have not received
any comments yet.
This work has been partially supported by the Polish Ministry of
Science and Higher Education under the European Regional Development
Fund, Grant No. POIG.01.01.02-00-045/09-00 (Future Internet
Engineering Project).
9. References
9.1. Normative References
[I-D.ietf-dhc-dhcpv4-over-ipv6]
Cui, Y., Wu, P., Wu, J., and T. Lemon, "DHCPv4 over IPv6
Transport", draft-ietf-dhc-dhcpv4-over-ipv6-05 (work in
progress), September 2012.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[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.
9.2. Informative References
[I-D.cui-softwire-b4-translated-ds-lite]
Cui, Y., Sun, Q., Boucadair, M., Tsou, T., Lee, Y., and I.
Farrer, "Lightweight 4over6: An Extension to the DS-Lite
Architecture", draft-cui-softwire-b4-translated-ds-lite-08
(work in progress), September 2012.
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[I-D.ietf-softwire-public-4over6]
Cui, Y., Wu, J., Wu, P., Vautrin, O., and Y. Lee, "Public
IPv4 over IPv6 Access Network",
draft-ietf-softwire-public-4over6-03 (work in progress),
August 2012.
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
Peng Wu
Tsinghua University
Beijing 100084
P.R.China
Email: pengwu.thu@gmail.com
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