RECONFIGURE Triggered by DHCPv6 Relay Agents
draft-ietf-dhc-triggered-reconfigure-01
The information below is for an old version of the document.
| Document | Type | Active Internet-Draft (dhc WG) | |
|---|---|---|---|
| Authors | Mohamed Boucadair , Xavier Pougnard | ||
| Last updated | 2012-09-28 | ||
| Stream | Internet Engineering Task Force (IETF) | ||
| Formats | plain text htmlized pdfized bibtex | ||
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draft-ietf-dhc-triggered-reconfigure-01
DHC Working Group M. Boucadair
Internet-Draft X. Pougnard
Updates: 3315, 6422 (if approved) France Telecom
Intended status: Standards Track September 28, 2012
Expires: April 1, 2013
RECONFIGURE Triggered by DHCPv6 Relay Agents
draft-ietf-dhc-triggered-reconfigure-01
Abstract
This document defines a new DHCPv6 message type: RECONFIGURE-REQUEST.
This message is sent by a DHCPv6 relay agent to notify a DHCPv6
server about a configuration information change, so that the DHCPv6
server can send a RECONFIGURE message accordingly.
This document updates RFC3315 and RFC6422.
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 April 1, 2013.
Copyright Notice
Copyright (c) 2012 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
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Problem . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Requirements Language . . . . . . . . . . . . . . . . . . . 4
2. Proposed Solution . . . . . . . . . . . . . . . . . . . . . . . 4
3. RECONFIGURE-REQUEST . . . . . . . . . . . . . . . . . . . . . . 5
3.1. Message Format . . . . . . . . . . . . . . . . . . . . . . 5
3.2. Message Validation . . . . . . . . . . . . . . . . . . . . 5
3.3. Creation and Transmission of RECONFIGURE-REQUEST . . . . . 6
3.4. Server Behaviour . . . . . . . . . . . . . . . . . . . . . 7
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 7
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8
7.1. Normative References . . . . . . . . . . . . . . . . . . . 8
7.2. Informative References . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8
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1. Introduction
1.1. Problem
[RFC6422] updates the DHCPv6 specification [RFC3315] with a new
feature to let a DHCPv6 relay agent communicate information towards a
DHCPv6 Client, and which is not available at the DHCPv6 server. This
is achieved owing to the use of RSOO (Relay-Supplied Options option)
which carries configuration data to the DHCPv6 server. The data
conveyed in an RSOO is then sent back by the DHCPv6 server to the
requesting DHCPv6 client.
An example of a RSOO context is shown in Figure 1; only a subset of
exchanged DHCPv6 and RADIUS messages is represented.
+-------+ +-------+ +-------+
|DHCPv6 | | NAS | |Radius |
|Client | |(DHCPv6| |Server |
| | | Relay)| | |
+-------+ +-------+ +-------+
| | |
|---Solicit---------------->| |
| |---Access-Request---------->|
|<--Access-Accept------------|
| (e.g. DS-Lite-Tunnel-Name)|
....
| +-------+
| |DHCPv6 |
| |Server |
| | |
| +-------+
| |
|---Relay-Forward----------->|
| (RSOO(DS-Lite-Tunnel-Name))|
| |
| |<--Relay-Reply--------------|
|<--Advertise---------------|
| (e.g., OPTION_AFTR_NAME) |
....
Figure 1: An Example of the RSOO Option Usage
The change of the configuration may result in RADIUS exchanges
([RFC5176]) between the NAS/DHCPv6 relay agent and Dynamic
Authorization Client (DAC) server as shown in Figure 2. Note the
change of the configuration in the DHCPv6 relay agent can be
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triggered by any other out-of-band mechanism.
+-------+ +-------+ +-------+
|DHCPv6 | | NAS | |Radius |
|Client | |(DHCPv6| |Server/|
| | | Relay)| | DAC |
+-------+ +-------+ +-------+
| | |
|<-----CoA-Request-----------|
| (e.g. DS-Lite-Tunnel-Name) |
|------CoA-Response--------->|
....
CoA (Change-of-Authorization, [RFC5176])
Figure 2: Change of configuration
Whenever the configuration information sent by the DHCPv6 relay agent
to the DHCPv6 server change, the DHCPv6 server has no means to detect
it so that it can send a Reconfigure message with the updated
configuration data accordingly. A solution is sketched in Section 2.
1.2. 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 [RFC2119].
2. Proposed Solution
To solve the problem described in Section 1.1, this document proposes
a new DHCP message called Reconfigure-Request. In the example
depicted in Figure 3 a Reconfigure-Request message is sent by the
DHCPv6 relay agent to a DHCPv6 server as soon as the configuration
data conveyed in an RSOO option have changed. Upon receipt of this
message, and if it is configured to support such mode, the DHCPv6
server must build a Reconfigure message. This message is then sent
to the DHCPv6 relay, which in turn will forward the message to the
appropriate DHCPv6 client.
This setup assumes the relay has a record of the client, so that it
has enough information to send the Reconfigure-Request message to the
server. Means to recover state in failure events must be supported,
but are not discussed in this document.
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+-------+ +-------+ +-------+
|DHCPv6 | | NAS | |Radius |
|Client | |(DHCPv6| |Server/|
| | | Relay)| | DAC |
+-------+ +-------+ +-------+
| | |
|<-----CoA-Request-----------|
| (e.g. DS-Lite-Tunnel-Name) |
| |
|------CoA-Response--------->|
....
| +-------+
| |DHCPv6 |
| |Server |
| | |
| +-------+
| |
|---Reconfigure-Request----->|
| |
| |
| |<--Relay-Reply -------------|
|<--Reconfigure-------------| (Reconfigure) |
| | |
....
Figure 3: RECONFIGURE-REQUEST Flow Example
The Reconfigure-Request message can also be used in other scenarios
than those that assume the use of RSOO. It is out of scope of this
document to describe all these scenarios.
3. RECONFIGURE-REQUEST
3.1. Message Format
A new message type code is defined:
RECONFIGURE-REQUEST (To be assigned by IANA, see Section 4).
RECONFIGURE-REQUEST uses the same format as defined in Section 6 of
[RFC3315].
3.2. Message Validation
Clients MUST silently discard any received RECONFIGURE-REQUEST
messages.
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Servers MUST silently discard any received RECONFIGURE-REQUEST
messages that meet any of the following conditions:
o the message does not include an OPTION_CLIENTID option.
o the message includes an OPTION_SERVERID option but the contents of
the OPTION_SERVERID option does not match the server's identifier.
The server MUST be configurable to accept or reject RECONFIGURE-
REQUEST messages. If the server is configured to reject RECONFIGURE-
REQUEST, the server MUST silently discard any RECONFIGURE-REQUEST it
receives.
The relay agent MUST be configurable to accept or reject RECONFIGURE-
REQUEST messages received from other relay agents. If the relay is
configured to reject RECONFIGURE-REQUEST, the relay MUST silently
discard any RECONFIGURE-REQUEST it receives. If the relay is
configured to accept RECONFIGURE-REQUEST messages, these messages are
relayed as specified in Section 20.1.1 of [RFC3315].
Because RECONFIGURE-REQUEST message provides a mechanism for
triggering the DHCP Reconfigure message, and the DHCP Reconfigure
message can raise security threats (e.g., to control the timing of a
DHCP renewal), the DHCP server MUST have some mechanism for
determining that the relay agent is a trusted entity. RECONFIGURE-
REQUEST messages originating from unknown relay agents MUST be
silently dropped.
3.3. Creation and Transmission of RECONFIGURE-REQUEST
For any event (e.g., modification of the configuration information)
that requires the server to issue a Reconfigure message, the relay
agent determines the client which is affected by the change and then
builds a Reconfigure-Request message: the relay agent sets the "msg-
type" field to RECONFIGURE-REQUEST and sets the "transaction-id "
field to 0. The relay agent MUST include an OPTION_CLIENTID option
[RFC3315] so that the DHCPv6 server can identify the corresponding
client. The relay agent MAY supply the updated configuration in the
RSOO [RFC6422]. The relay agent MAY supply an OPTION_RECONF_MSG
option to indicate which form of Reconfigure to use.
When several clients are concerned with a configuration change, the
relay MUST include several OPTION_CLIENTID options, each of them
identifies a specific client. If including OPTION_CLIENTID options
of all impacted clients exceeds the maximum message size, the relay
MUST generate several RECONFIGURE-REQUEST messages required to carry
all OPTION_CLIENTID options.
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3.4. Server Behaviour
Upon receipt of a valid Reconfigure-Request message from a DHCPv6
relay agent (see Section 3.2), the server determines the client(s)
for which a Reconfigure message is to be sent.
The server MAY use the content of the OPTION_RECONF_MSG option
supplied by the relay agent to determine which form of Reconfigure to
use.
If RSOO is supplied, the server MAY use its content to double check
whether a Reconfigure is required to be sent to the client. This
assumes the server store the content of RSOO it used to generate
configuration data sent to requesting clients.
Then, the server MUST follow the procedure defined in Section 19.1 of
[RFC3315] to construct a Reconfigure message. This message may be
sent directly to the DHCPv6 client or to a relay agent [RFC3315].
4. IANA Considerations
This document requests IANA to assign a new DHCPv6 Message type:
RECONFIGURE-REQUEST
5. Security Considerations
Security considerations elaborated in [RFC3315] and [RFC6422] must be
taken into account. In addition, DHCPv6 servers MAY be configured to
discard relayed RECONFIGURE-REQUEST messages or restrict relay
chaining (see [RFC5007] for more discussion about the rationale of
this recommended behavior). Relay agents SHOULD implement
appropriate means to prevent using RECONFIGURE-REQUEST messages as a
denial-of-service attack on the DHCPv6 servers.
6. Acknowledgements
Many thanks to T. Lemon, R. Maglione, A. Kostur, G. Halwasia and C.
Jacquenet for the comments and review.
7. References
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7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, 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.
[RFC6422] Lemon, T. and Q. Wu, "Relay-Supplied DHCP Options",
RFC 6422, December 2011.
7.2. Informative References
[RFC5007] Brzozowski, J., Kinnear, K., Volz, B., and S. Zeng,
"DHCPv6 Leasequery", RFC 5007, September 2007.
[RFC5176] Chiba, M., Dommety, G., Eklund, M., Mitton, D., and B.
Aboba, "Dynamic Authorization Extensions to Remote
Authentication Dial In User Service (RADIUS)", RFC 5176,
January 2008.
Authors' Addresses
Mohamed Boucadair
France Telecom
Rennes, 35000
France
Email: mohamed.boucadair@orange.com
Xavier Pougnard
France Telecom
Lannion,
France
Phone:
Email: xavier.pougnard@orange.com
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