draft-ietf-dhc-dhcpv6-stateful-issues-03.txt   draft-ietf-dhc-dhcpv6-stateful-issues-04.txt 
Network Working Group O. Troan Network Working Group O. Troan
Internet-Draft B. Volz Internet-Draft B. Volz
Updates: 3315,3633 (if approved) Cisco Systems, Inc. Updates: 3315,3633 (if approved) Cisco Systems, Inc.
Intended status: Standards Track November 5, 2012 Intended status: Standards Track May 13, 2013
Expires: May 9, 2013 Expires: November 14, 2013
Issues with multiple stateful DHCPv6 options Issues with multiple stateful DHCPv6 options
draft-ietf-dhc-dhcpv6-stateful-issues-03.txt draft-ietf-dhc-dhcpv6-stateful-issues-04.txt
Abstract Abstract
Dynamic Host Configuration Protocol for IPv6 (DHCPv6) was not written Dynamic Host Configuration Protocol for IPv6 (DHCPv6) was not written
with the expectation that additional stateful DHCPv6 options would be with the expectation that additional stateful DHCPv6 options would be
developed. IPv6 Prefix Options for Dynamic Host Configuration developed. IPv6 Prefix Options for Dynamic Host Configuration
Protocol (DHCP) version 6 shoe-horned the new options for Prefix Protocol (DHCP) version 6 shoe-horned the new options for Prefix
Delegation into DHCPv6. Implementation experience of the CPE model Delegation into DHCPv6. Implementation experience of the CPE model
described in has shown multiple issues with the DHCPv6 protocol in described in [RFC6204] has shown multiple issues with the DHCPv6
supporting multiple stateful options. protocol in supporting multiple stateful options.
Status of this Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on May 9, 2013. This Internet-Draft will expire on November 14, 2013.
Copyright Notice Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Handling of multiple IA options types . . . . . . . . . . . . 4 4. Handling of multiple IA options types . . . . . . . . . . . . 3
4.1. Advertisement message . . . . . . . . . . . . . . . . . . 4 4.1. Advertisement message . . . . . . . . . . . . . . . . . . 4
4.2. Placement of Status codes . . . . . . . . . . . . . . . . 5 4.2. Placement of Status codes . . . . . . . . . . . . . . . . 5
4.3. T1/T2 timers . . . . . . . . . . . . . . . . . . . . . . . 6 4.3. T1/T2 timers . . . . . . . . . . . . . . . . . . . . . . 5
4.4. Renew and Rebind messages . . . . . . . . . . . . . . . . 6 4.4. Renew and Rebind messages . . . . . . . . . . . . . . . . 6
4.5. Confirm message . . . . . . . . . . . . . . . . . . . . . 8 4.5. Confirm message . . . . . . . . . . . . . . . . . . . . . 7
4.6. Release messages . . . . . . . . . . . . . . . . . . . . . 9 4.6. Release messages . . . . . . . . . . . . . . . . . . . . 8
4.7. Multiple provisioning domains . . . . . . . . . . . . . . 9 4.7. Multiple provisioning domains . . . . . . . . . . . . . . 9
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
6. Security Considerations . . . . . . . . . . . . . . . . . . . 9 6. Security Considerations . . . . . . . . . . . . . . . . . . . 9
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 9 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
8.1. Normative References . . . . . . . . . . . . . . . . . . . 9 8.1. Normative References . . . . . . . . . . . . . . . . . . 9
8.2. Informative References . . . . . . . . . . . . . . . . . . 10 8.2. Informative References . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction 1. Introduction
DHCPv6 [RFC3315] was not written with the expectation that additional DHCPv6 [RFC3315] was not written with the expectation that additional
stateful DHCPv6 options would be developed. DHCPv6 Prefix Delegation stateful DHCPv6 options would be developed. DHCPv6 Prefix Delegation
[RFC3633] shoe-horned the new options for Prefix Delegation into [RFC3633] shoe-horned the new options for Prefix Delegation into
DHCPv6. Implementation experience of the CPE model described in DHCPv6. Implementation experience of the CPE model described in
[RFC6204] has shown multiple issues with the DHCPv6 protocol in [RFC6204] has shown multiple issues with the DHCPv6 protocol in
supporting multiple stateful options. supporting multiple stateful options.
skipping to change at page 4, line 43 skipping to change at page 4, line 20
of them, is not supported in the current protocol specification. of them, is not supported in the current protocol specification.
Proposed solution: a client SHOULD accept Advertise messages, even Proposed solution: a client SHOULD accept Advertise messages, even
when not all IA option types are being offered. A client SHOULD when not all IA option types are being offered. A client SHOULD
ignore an Advertise message when no bindings at all are being ignore an Advertise message when no bindings at all are being
offered. The client SHOULD include the not offered IA option types offered. The client SHOULD include the not offered IA option types
in its Request. in its Request.
Replace Section 17.1.3 of [RFC3315]: (existing errata) Replace Section 17.1.3 of [RFC3315]: (existing errata)
The client MUST ignore any Advertise message that includes a Status The client MUST ignore any Advertise message that includes a Status
Code option containing the value NoAddrsAvail, with the exception Code option containing the value NoAddrsAvail, with the exception
that the client MAY display the associated status message(s) to the that the client MAY display the associated status message(s) to the
user. user.
With: With:
The client MUST ignore any Advertise message that contains no The client MUST ignore any Advertise message that contains no
bindings (if only IA_NA and/or IA_TA options were requested, bindings (if only IA_NA and/or IA_TA options were requested,
this is a message that includes a Status Code option containing the this is a message that includes a Status Code option containing the
value NoAddrsAvail), with the exception that the client MAY display value NoAddrsAvail), with the exception that the client MAY display
the associated status message(s) to the user. the associated status message(s) to the user.
And, replace: And, replace:
- The client MAY choose a less-preferred server if that server - The client MAY choose a less-preferred server if that server
has a better set of advertised parameters, such as the has a better set of advertised parameters, such as the
available addresses advertised in IAs. available addresses advertised in IAs.
With: With:
- The client MAY choose a less-preferred server if that server - The client MAY choose a less-preferred server if that server
has a better set of advertised parameters, such as the has a better set of advertised parameters, such as the
available options advertised in IAs. available options advertised in IAs.
It is important to note that the receipt of a Advertisement without It is important to note that the receipt of a Advertisement without
any bindings does not imply that the client should restart the any bindings does not imply that the client should restart the
Solicit retransmissions timers. Doing so would lead to a Solicit/ Solicit retransmissions timers. Doing so would lead to a Solicit/
Advertisement storm. Advertisement storm.
4.2. Placement of Status codes 4.2. Placement of Status codes
In Reply messages IA specific status codes (NoAddrsAvail, NotOnlink, In Reply messages IA specific status codes (i.e., NoAddrsAvail,
NoBinding) are encapsulated in the IA option. In Advertisement NotOnlink, NoBinding, NoPrefixAvail) are encapsulated in the IA
messages the Status Code option with the NoAddrsAvail code is in the option. In Advertisement messages the Status Code option with the
"global" scope. That makes sense when the failure case is fatal. NoAddrsAvail code is in the "global" scope. That makes sense when
With the introduction of multiple IA option types, there might be a the failure case is fatal. With the introduction of multiple IA
case where a server is not willing to offer addresses, but might be option types, there might be a case where a server is not willing to
willing to offer other stateful option types. offer addresses, but might be willing to offer other stateful option
types.
While a Status Code option is implicitly bound to a specific type of While a Status Code option is implicitly bound to a specific type of
IA, e.g. NoPrefixAvail is only applicable to IA_PD and NoAddrsAvail IA, e.g. NoPrefixAvail is only applicable to IA_PD and NoAddrsAvail
is only applicable to IA_NA/IA_TA, it may be problematic to make this is only applicable to IA_NA/IA_TA, it may be problematic to make this
assumption for all status codes. Ideally the Status Code option assumption for all status codes. Ideally the Status Code option
should be encapsulated in the IA option for all DHCP messages. This should be encapsulated in the IA option for all DHCP messages. This
makes Advertisement messages equal to Reply messages. makes Advertisement messages equal to Reply messages.
Proposed solution: No change. For backwards compatibility, the Proposed solution: No change. For backwards compatibility, the
NoAddrsAvail Status Code option when no addresses are available will NoAddrsAvail Status Code option when no addresses are available will
skipping to change at page 6, line 46 skipping to change at page 6, line 25
client sent the Request. client sent the Request.
Proposed solution: The client should continue with the IA options Proposed solution: The client should continue with the IA options
received, while continuing to include the other IA options in received, while continuing to include the other IA options in
subsequent messages to the server. The client and server processing subsequent messages to the server. The client and server processing
need to be modified. Note that this change makes the server's IA need to be modified. Note that this change makes the server's IA
processing of Renew and Rebind similar to the Request processing. processing of Renew and Rebind similar to the Request processing.
Replace Section 18.1.3 of [RFC3315]: Replace Section 18.1.3 of [RFC3315]:
At time T1 for an IA, the client initiates a Renew/Reply message At time T1 for an IA, the client initiates a Renew/Reply message
exchange to extend the lifetimes on any addresses in the IA. The exchange to extend the lifetimes on any addresses in the IA. The
client includes an IA option with all addresses currently assigned client includes an IA option with all addresses currently assigned
to the IA in its Renew message. to the IA in its Renew message.
With: With:
At time T1 for an IA, the client initiates a Renew/Reply message At time T1 for an IA, the client initiates a Renew/Reply message
exchange to extend the lifetimes on any addresses in the IA. The exchange to extend the lifetimes on any addresses in the IA. The
client includes an IA option with all addresses currently assigned client includes an IA option with all addresses currently assigned
to the IA in its Renew message. The client also includes an IA to the IA in its Renew message. The client also includes an IA
option for each binding it desires but has been unable to obtain. option for each binding it desires but has been unable to obtain.
Replace Section 18.2.3 of [RFC3315]: Replace Section 18.2.3 of [RFC3315]:
If the server cannot find a client entry for the IA the server If the server cannot find a client entry for the IA the server
returns the IA containing no addresses with a Status Code option returns the IA containing no addresses with a Status Code option
set to NoBinding in the Reply message. set to NoBinding in the Reply message.
With: With:
If the server cannot find a client entry for the IA the server If the server cannot find a client entry for the IA the server
creates the bindings for that client according to the server's creates the bindings for that client according to the server's
policy and configuration information and records the IAs and policy and configuration information and records the IAs and
other information requested by the client. other information requested by the client.
Note that clients that communicate with servers that do not support Note that clients that communicate with servers that do not support
this updated Renew processing will receive the NoBinding status for this updated Renew processing will receive the NoBinding status for
the IA which had no bindings. The client MUST continue to process the IA which had no bindings. The client MUST continue to process
the other IAs in the Reply. The client MAY attempt a Solicit/ the other IAs in the Reply. The client MAY attempt a Solicit/
Advertise/Request/Reply sequence periodically to obtain bindings for Advertise/Request/Reply sequence periodically to obtain bindings for
these IAs. However, it MUST limit the frequency at which is does these IAs. However, it MUST limit the frequency at which is does
this to no more often than the renewal frequency. this to no more often than the renewal frequency.
Replace Section 18.1.4 of [RFC3315]: Replace Section 18.1.4 of [RFC3315]:
At time T2 for an IA (which will only be reached if the server to At time T2 for an IA (which will only be reached if the server to
which the Renew message was sent at time T1 has not responded), the which the Renew message was sent at time T1 has not responded), the
client initiates a Rebind/Reply message exchange with any available client initiates a Rebind/Reply message exchange with any available
server. The client includes an IA option with all addresses server. The client includes an IA option with all addresses
currently assigned to the IA in its Rebind message. currently assigned to the IA in its Rebind message.
With: With:
At time T2 for an IA (which will only be reached if the server to At time T2 for an IA (which will only be reached if the server to
which the Renew message was sent at time T1 has not responded), the which the Renew message was sent at time T1 has not responded), the
client initiates a Rebind/Reply message exchange with any available client initiates a Rebind/Reply message exchange with any available
server. The client includes an IA option with all addresses server. The client includes an IA option with all addresses
currently assigned to the IA in its Rebind message. The client currently assigned to the IA in its Rebind message. The client
also includes an IA option for each binding it desires but has been also includes an IA option for each binding it desires but has been
unable to obtain. unable to obtain.
4.5. Confirm message 4.5. Confirm message
The Confirm message, as described in [RFC3315], is specific to The Confirm message, as described in [RFC3315], is specific to
address assignment. It lets a server without a binding to reply to address assignment. It allows a server without a binding reply to
the message, under the assumption that the server only needs the message, under the assumption that the server only needs
knowledge about the prefix(es) on the link, to inform the client that knowledge about the prefix(es) on the link, to inform the client that
the address is likely valid or not. This message is sent when e.g. the address is likely valid or not. This message is sent when e.g.
the client has moved and needs to validate its addresses. Not all the client has moved and needs to validate its addresses. Not all
bindings can be validated by servers and the Confirm message provides bindings can be validated by servers and the Confirm message provides
for this by specifying that a server that is unable to determine the for this by specifying that a server that is unable to determine the
on-link status MUST NOT send a Reply. on-link status MUST NOT send a Reply.
Note: Confirm has a specific meaning and does not overload Renew/ Note: Confirm has a specific meaning and does not overload Renew/
Rebind. It also is lower processing cost as the server does NOT need Rebind. It also is lower processing cost as the server does NOT need
skipping to change at page 9, line 9 skipping to change at page 8, line 43
associated with those IA_PDs in its Confirm message. associated with those IA_PDs in its Confirm message.
... ...
The Decline message type is not used with Prefix Delegation. The Decline message type is not used with Prefix Delegation.
4.6. Release messages 4.6. Release messages
A client can release any individual lease at any time. A client can A client can release any individual lease at any time. A client can
get "back" a lease by using a Renew message. It MAY do this at any get "back" a lease by using a Renew message. It MAY do this at any
time, though must avoid creating a Renew storm. E.g. wait until T1. time, though must avoid creating a Renew storm. E.g. wait until T1.
4.7. Multiple provisioning domains 4.7. Multiple provisioning domains
This document has assumed that all DHCP servers on a network are in a This document has assumed that all DHCP servers on a network are in a
single provisioning domain and thus should be "equal" in the service single provisioning domain and thus should be "equal" in the service
that they offer. This was also assumed by [RFC3315] and [RFC3633]. that they offer. This was also assumed by [RFC3315] and [RFC3633].
One could envision a network where the DHCP servers are in multiple One could envision a network where the DHCP servers are in multiple
provisioning domains, and it may be desirable to have the DHCP client provisioning domains, and it may be desirable to have the DHCP client
obtain different IA types from different provisioning domains. How a obtain different IA types from different provisioning domains. How a
skipping to change at page 10, line 12 skipping to change at page 10, line 4
Host Configuration Protocol (DHCP) version 6", RFC 3633, Host Configuration Protocol (DHCP) version 6", RFC 3633,
December 2003. December 2003.
8.2. Informative References 8.2. Informative References
[RFC6204] Singh, H., Beebee, W., Donley, C., Stark, B., and O. [RFC6204] Singh, H., Beebee, W., Donley, C., Stark, B., and O.
Troan, "Basic Requirements for IPv6 Customer Edge Troan, "Basic Requirements for IPv6 Customer Edge
Routers", RFC 6204, April 2011. Routers", RFC 6204, April 2011.
Authors' Addresses Authors' Addresses
Ole Troan Ole Troan
Cisco Systems, Inc. Cisco Systems, Inc.
Philip Pedersens vei 20 Philip Pedersens vei 20
N-1324 Lysaker, N-1324 Lysaker
Norway Norway
Email: ot@cisco.com Email: ot@cisco.com
Bernie Volz Bernie Volz
Cisco Systems, Inc. Cisco Systems, Inc.
1414 Massachusetts Ave 1414 Massachusetts Ave
Boxborough, MA 01719, Boxborough, MA 01719
USA USA
Email: volz@cisco.com Email: volz@cisco.com
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