| Network Working Group | M. Boucadair |
| Internet-Draft | France Telecom |
| Updates: 3315 (if approved) | August 24, 2012 |
| Intended status: Standards Track | |
| Expires: February 23, 2013 |
RECONFIGURE Triggered by DHCPv6 Relay Agents
draft-boucadair-dhc-triggered-reconfigure-00
This document specifies a companion solution to the RSOO (Relay-Supplied Options option) procedure to trigger a DHCPv6 server to issue a RECONFIGURE message. This document defines a new DHCPv6 messages type: RECONFIGURE-REQUEST. This message is issued by a relay agent to notify a DHCPv6 server a change has occurred in the configuration supplied in an RSOO.
This document updates RFC 3315.
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 February 23, 2013.
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[RFC6422] updates DHCPv6 specification [RFC3315] with a new feature to let a DHCPv6 relay agent communicate information not available at the DHCPv6 server to a DHCPv6 client. 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 illustration example is shown in Figure 1; only a subset of exchanged messages are represented.
+-------+ +-------+ +-------+
|DHCPv6 | | NAS | |Radius |
|Client | |(DHCPv6| |Server |
| | | Relay)| | |
+-------+ +-------+ +-------+
| | |
|---Solicit---------------->| |
|---Access-Request---------->|
|<--Access-Accept------------|
| (e.g. AFTR_NAME)
....
| +-------+
| |DHCPv6 |
| |Server |
| | |
| +-------+
|---Relay-Forward----------->|
| (RSOO(AFTR_NAME))
|
|<--Relay-Reply--------------|
|<--Advertise---------------|
(e.g., AFTR_NAME) |
....
Figure 1: RSOO Flow Example
The change of the configuration may result in RADIUS exchanges between the NAS/DHCPv6 relay agent and AAA server as shown in Figure 2. Note the change of the configuration in the DHCPv6 relay agent can be triggered by any other out-of-band mechanism.
+-------+ +-------+ +-------+
|DHCPv6 | | NAS | |Radius |
|Client | |(DHCPv6| |Server |
| | | Relay)| | |
+-------+ +-------+ +-------+
| | |
|<-----CoA-Request-----------|
| (e.g. AFTR_NAME)
|------CoA-Response--------->|
....
Figure 2: Change of configuration
In the event of the change of the configuration data supplied to the DHCPv6 server by the DHCPv6 relay agent, DHCPv6 server has no trigger to issue a Reconfigure message with the updated configuration data. A solution is sketched in Section 2.
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].
To solve the problem described in Section 1.1, this document proposes a new DHCP message called Reconfigure-Request. This message is sent by the DHCPv6 relay agent to a DHCPv6 server when a configuration data already supplied in an RSOO is detected. In particular, Reconfigure-Request must include RSOO with the new configuration. Upon receipt of this message, and if it is configured to support such mode, the DHCPv6 server must build a Reconfigure message which copies the data conveyed in RSOO. This message is sent to the DHCPv6 relay and then relayed to the appropriate DHCPv6 client.
This setup assumes the relay has a record of the client, so it has enough information to send the request to the server. Means to recover state in failure events must be supported.
An example is depicted in Figure 3.
+-------+ +-------+ +-------+
|DHCPv6 | | NAS | |Radius |
|Client | |(DHCPv6| |Server |
| | | Relay)| | |
+-------+ +-------+ +-------+
| | |
|<-----CoA-Request-----------|
| (e.g. AFTR_NAME)
|------CoA-Response--------->|
....
| +-------+
| |DHCPv6 |
| |Server |
| | |
| +-------+
|---Reconfigure-Request----->|
| (RSOO(AFTR_NAME))
|
|<--Relay-Reply -------------|
|<--Reconfigure-------------| (Reconfigure(AFTR_NAME))
(e.g., AFTR_NAME) |
....
Figure 3: RECONFIGURE-REQUEST Flow Example
The RECONFIGURE-REQUEST message uses the Client/Server message format described in Section 6 of [RFC3315]. A new message type code is defined
Clients MUST discard any received RECONFIGURE-REQUEST messages.
Servers MUST 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.
o the message does not include an RSOO.
In the event of change of an information which has been supplied to the DHCPv6 server, the relay agent determines the client which is concerned by the change and then builds a Reconfigure-Request message: the relay agent sets the "msg-type" field to RECONFIFURE-REQUEST and sets the "transaction-id" field to 0. The relay agent MUST supply the updated configuration in RSOO as defined in [RFC6422] and MUST include an OPTION_CLIENTID option [RFC3315] to identify the client to the DHCPv6 server.
Upon receipt of a valid Reconfigure-Request message from a DHCPv6 relay agent, the server follows the procedure defined in Section 19.1 of [RFC3315] and Section 4 of [RFC6422] to construct a Reconfigure message.
As defined in [RFC3315], this message may be sent directly to the DHCPv6 client or to a relay agent.
This document requests IANA to assign a new DHCPv6 Message type:
Security considerations elaborated in [RFC3315] and [RFC6422] must be taken into account.
Some security issues discussed in [RFC5007] may also be valid for RECONFIGURE-REQUEST. This will be elaborated in further versions of this document.
Many thanks to T. Lemon for the discussion prior to the publication of this document.
| [RFC2119] | Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. |
| [RFC6422] | Lemon, T. and Q. Wu, "Relay-Supplied DHCP Options", RFC 6422, December 2011. |
| [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. |
| [RFC5007] | Brzozowski, J., Kinnear, K., Volz, B. and S. Zeng, "DHCPv6 Leasequery", RFC 5007, September 2007. |