Network Working Group D. Evans
Internet-Draft ARRIS International, Inc.
Intended status: Informational R. Droms
Expires: May 21, 2009 Cisco Systems, Inc.
November 17, 2008
Rebind Capability in DHCPv6 Reconfigure Messages
draft-ietf-dhc-dhcpv6-reconfigure-rebind-06.txt
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Abstract
This document updates RFC 3315 to allow the Rebind message type to
appear in the Reconfigure Message option of a Reconfigure message,
which extends the Reconfigure message to allow a DHCPv6 server to
cause a DHCPv6 client to send a Rebind message. The document also
clarifies how a DHCPv6 client responds to a received Reconfigure
message.
1. Introduction
DHCPv6 [RFC3315] allows a server to send an unsolicited Reconfigure
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message to a client. The client's response to a Reconfigure message,
according to section 19 of RFC 3315 is either a Renew or an
Information-Request message, depending on the contents of the msg-
type field in the Reconfigure Message option of the Reconfigure
message.
If the client sends a Renew message, it includes a Server Identifier
option in the Renew message to specify the server that should respond
to the Renew message. Under some circumstances, it may be desirable
for the client to communicate with a different server; for example,
if the server that the client most recently communicated with is no
longer available, the network administrator may want the client to
communicate with a different server. This document expands the
allowed values of the msg-type field to allow the server to indicate
that the client is to send a Rebind message, which does not include a
Server Identifier option and allows any server to respond to the
client.
RFC 3315 does not specify that a Reconfigure message must be sent
from the server with which the client most recently communicated, and
it does not specify which server the client should identify with a
Server Identifier option when the client responds to the Reconfigure
message. This document clarifies that the client should send a Renew
message in response to a Reconfigure message with a Server Identifier
option identifying the same server that the client would have
identified if the client had sent the Renew message after expiration
of T1.
2. Terminology
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].
This document uses IPv6 and DHCPv6 terms as defined in section 4 of
RFC 3315.
3. The Reconfigure Message option of the DHCPv6 Reconfigure Message
This section modifies section 22.19 of RFC 3315 to allow the
specification of the Rebind message in a Reconfigure message.
A server includes a Reconfigure Message option in a Reconfigure
message to indicate to the client whether the client responds with a
Renew, an Information-request, or a Rebind message.
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The format of this option is:
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_RECONF_MSG | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| msg-type |
+-+-+-+-+-+-+-+-+
option-code OPTION_RECONF_MSG (19).
option-len 1.
msg-type 5 for Renew message, 6 for Rebind, 11 for
Information-request message.
4. Server Behavior
This section updates specific text in sections 19.1, 19.2 and 19.3 of
RFC 3315.
The server MUST include a Reconfigure Message option (as defined in
Section 3) to select whether the client responds with a Renew
message, a Rebind message or an Information-Request message.
The Reconfigure message causes the client to initiate a Renew/Reply,
a Rebind/Reply message exchange or an Information-request/Reply
message exchange. The server interprets the receipt of a Renew, a
Rebind or an Information-request message (whichever was specified in
the original Reconfigure message) from the client as satisfying the
Reconfigure message request.
The server retransmits a Reconfigure message specifying a Rebind
message in the same way as described in section 19.1.2 of RFC 3315.
In response to a Rebind message, the server generates and sends a
Reply message to the client as described in sections 18.2.4 and
18.2.8, including options for configuration parameters.
The server MAY include options containing the IAs and new values for
other configuration parameters in the Reply message, even if those
IAs and parameters were not requested in the Renew message from the
client.
4.1. Client Behavior
This section updates specific text in section 19.4 of RFC 3315.
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Upon receipt of a valid Reconfigure message, the client responds with
a Renew message, a Rebind message or an Information-request message
as indicated by the Reconfigure Message option (as defined in
Section 3). The client ignores the transaction-id field in the
received Reconfigure message. While the transaction is in progress,
the client silently discards any Reconfigure messages it receives.
When responding to a Reconfigure, the client creates and sends the
Rebind message in exactly the same manner as outlined in section
18.1.4 of RFC 3315, with the exception that the client copies the
Option Request option and any IA options from the Reconfigure message
into the Rebind message.
If a client is currently sending Rebind messages, as described in
section 18.1.4 of RFC 3315, the client ignores any received
Reconfigure messages.
The client uses the same variables and retransmission algorithm as it
does with Renew, Rebind or Information-request messages generated as
part of a client-initiated configuration exchange. See sections
18.1.3, 18.1.4 and 18.1.5 of RFC 3315 for details. If the client
does not receive a response from the server by the end of the
retransmission process, the client ignores and discards the
Reconfigure message.
5. Clarification of section 19.4.2, RFC 3315
When sending a Renew message in response to the receipt of a
Reconfigure message, the client MUST include a Server Identifier
option identifying the server the client most recently communicated
with.
6. Security Considerations
This document adds no new security considerations beyond those
present in RFC 3315.
7. IANA Considerations
There are no actions for IANA associated with this document.
8. Change log
This section MUST be removed before publication.
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8.1. Revision -05
Clarified description of this feature in introduction.
Clarified action of client if it receives a Reconfigure while sending
Rebind messages.
8.2. Revision -06
Corrected a minor typo, changing "RFC3315" to "RFC 3315" in section
1.
9. 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.
Authors' Addresses
D. R. Evans
ARRIS International, Inc.
7912 Fairview Road
Boulder, CO 80303
USA
Phone: +1 303.494.0394
Email: N7DR@arrisi.com
Ralph Droms
Cisco Systems, Inc.
1414 Massachusetts Avenue
Boxborough, MA 01719
USA
Phone: +1 978.936.1674
Email: rdroms@cisco.com
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