DHC Working Group                                         D. Raghuvanshi
Internet-Draft                                                K. Kinnear
Intended status: Standards Track                              D. Kukrety
Expires: June 7, September 29, 2014                          Cisco Systems, Inc.
                                                        December 4, 2013
                                                          March 28, 2014

                        DHCPv6 Active Leasequery
               draft-ietf-dhc-dhcpv6-active-leasequery-00
               draft-ietf-dhc-dhcpv6-active-leasequery-01

Abstract

   The Dynamic Host Configuration Protocol for IPv6 (DHCPv6) has been
   extended with a Leasequery capability that allows a requestor to
   request information about DHCPv6 bindings.  That mechanism is limited
   to queries for DHCPv6 binding data updates until prior to the time the
   DHCPv6 server receive receives the Leasequery request.  Continuous update of
   an external requestor with Leasequery data is sometimes desired.
   This document expands on the DHCPv6 Leasequery protocol, and allows
   for active transfer of real-time DHCPv6 binding information data via
   TCP.  This document also extends DHCPv6 Bulk Leasequery by adding new
   options.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
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   This Internet-Draft will expire on June 7, September 29, 2014.

Copyright Notice

   Copyright (c) 2013 2014 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
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   publication of this document.  Please review these documents
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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Protocol Overview . . . . . . . . . . . . . . . . . . . . . .   4   5
   4.  Interaction Between Active Leasequery and Bulk Leasequery . .   6
   5.  Extension to DHCPv6 Bulk Leasequery . . . . . . . . . . . . .   7
   6.  Message and Option Definitions  . . . . . . . . . . . . . . .   7
     6.1.  Message Framing for TCP . . . . . . . . . . . . . . . . .   7
     6.2.  Messages  . . . . . . . . . . . . . . . . . . . . . . . .   7
       6.2.1.  ACTIVELEASEQUERY  . . . . . . . . . . . . . . . . . .   7   8
     6.3.  Options . . . . . . . . . . . . . . . . . . . . . . . . .   8
       6.3.1.  OPTION_LQ_BASE_TIME . . . . . . . . . . . . . . . . .   8   9
       6.3.2.  OPTION_LQ_START_TIME  . . . . . . . . . . . . . . . .   9
       6.3.3.  OPTION_LQ_END_TIME  . . . . . . . . . . . . . . . . .   9  10
     6.4.  Connection and Transmission Parameters  . . . . . . . . .  10  11
   7.  Information Communicated by Active Leasequery . . . . . . . .  11
   8.  Requestor Behavior  . . . . . . . . . . . . . . . . . . . . .  11  12
     8.1.  Connecting and General Processing . . . . . . . . . . . .  11  12
     8.2.  Forming an Active Leasequery  . . . . . . . . . . . . . .  12  13
     8.3.  Processing Active Replies . . . . . . . . . . . . . . . .  13  14
       8.3.1.  Processing Replies from a Request Containing a
               OPTION_LQ_START_TIME  . . . . . . . . . . . . . . . .  15
     8.4.  Processing Time Values in Leasequery messages . . . . . .  17  18
     8.5.  Examples  . . . . . . . . . . . . . . . . . . . . . . . .  18
       8.5.1.  Query Failure . . . . . . . . . . . . . . . . . . . .  18  19
       8.5.2.  Data Missing on Server  . . . . . . . . . . . . . . .  18  19
       8.5.3.  Successful Query  . . . . . . . . . . . . . . . . . .  19
     8.6.  Closing Connections . . . . . . . . . . . . . . . . . . .  19  20
   9.  Server Behavior . . . . . . . . . . . . . . . . . . . . . . .  19  20
     9.1.  Accepting Connections . . . . . . . . . . . . . . . . . .  19  20
     9.2.  Replying to an Active Leasequery  . . . . . . . . . . . .  20
     9.3.  Multiple or Parallel Queries  . . . . . . . . . . . . . .  22
     9.4.  Closing Connections . . . . . . . . . . . . . . . . . . .  22  23
   10. Security Considerations . . . . . . . . . . . . . . . . . . .  22  23
   11. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  24
   12. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  24  25
   13. Modification History  . . . . . . . . . . . . . . . . . . . .  24  25
   14. References  . . . . . . . . . . . . . . . . . . . . . . . . .  24  25
     14.1.  Normative References . . . . . . . . . . . . . . . . . .  24  25
     14.2.  Informative References . . . . . . . . . . . . . . . . .  25

   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  25  26

1.  Introduction

   The DHCPv6 [RFC3315] protocol specifies a mechanism for the
   assignment of IPv6 address and configuration information to IPv6
   nodes.  IPv6 Prefix Delegation for DHCPv6 (PD) [RFC3633] specifies a
   mechanism for DHCPv6 delegation of IPv6 prefixes and related data.
   DHCPv6 servers maintain authoritative information including binding
   information for delegated IPv6 prefixes.

   Requirements exist for external entities to keep up to date on the
   correspondence between DHCPv6 clients and their bindings.  These
   requirements often stem from regulatory requirements placed on
   service providers by governmental agencies.

   These entities need to keep up with the current binding activity of
   the DHCPv6 server.  Keeping up with these binding activity is termed
   "active" leasequery.

   The DHCPv6 Bulk Leasequery [RFC5460] capability can be used to
   recover useful information from a DHCPv6 server when some external
   entity starts up.  This entity could be one which is directly
   involved in the DHCPv6 client - server transactions (e.g., a relay
   agent), or it could be an external process which needs information
   present in the DHCPv6 server's lease state database.

   The Active Leasequery capability documented here is designed to allow
   an entity not directly involved in DHCPv6 client - server
   transactions to nevertheless keep current with the state of the
   DHCPv6 lease state information in real-time.

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 RFC 2119 [RFC2119].

   DHCPv6 terminology is defined in [RFC3315].  Terminology specific to
   DHCPv6 Active Leasequery can be found below:

   o  "Absolute Time"

      A 32-bit quantity containing the number of seconds since midnight
      January 1, 2000 UTC.

   o  "Active Leasequery"

      Keeping up to date in real-time (or near real-time) with DHCPv6
      binding activity.

   o  "Bulk Leasequery"

      Requesting and receiving the existing DHCPv6 binding information
      in an efficient manner.

   o  "binding change/update"

      Any change in the DHCPv6 binding state or data stored on the
      DHCPv6 server related to binding.  This also includes expiration
      or deletion of the binding.

   o  "catch-up information, catch-up phase"

      If a DHCPv6 Active Leasequery requestor sends OPTION_LQ_START_TIME
      option in a an ACTIVELEASEQUERY message, the DHCPv6 server will
      attempt to send the requestor the information that changed since
      the time specified in the OPTION_LQ_START_TIME option.  The
      binding information sent to satisfy this request is the catch-up
      information, and the period while it is being sent is the catch-up
      phase.

   o  "clock skew"

      The difference between the absolute time on a DHCPv6 server and
      the absolute time on the system where a requestor of an Active or
      Bulk Leasequery is executing is termed the "clock skew" for that
      Active or Bulk Leasequery connection.  It is not absolutely
      constant but is likely to vary only slowly.  While it is easy to
      think that this can be calculated precisely after one packet is
      received by a requestor from a DHCPv6 server, a more accurate
      value is derived from continuously examining the instantaneous
      value developed from each packet received from a DHCPv6 server and
      using it to make small adjustments to the existing value held in
      the requestor.

   o  "Transaction ID"

      An opaque value used to match responses with queries initiated by
      an Active Leasequery requestor.

3.  Protocol Overview

   The Active Leasequery mechanism is modeled on the existing DHCPv6
   Bulk Leasequery [RFC5460]; most differences arise from the long term
   nature of the TCP [RFC4614] connection required for Active
   Leasequery.  In addition, a DHCPv6 server which supports Active
   Leasequery MUST support Bulk Leasequery [RFC5460] as well.

   An Active Leasequery requestor opens a TCP connection to a DHCPv6
   Server, using the DHCPv6 port 547.  Note that this implies that the
   Leasequery requestor has server IP address(es) available via
   configuration or some other means, and that it has unicast IP
   reachability to the DHCPv6 server.  No relaying for Active Leasequery
   is specified.

   After establishing a connection, the requestor sends an
   ACTIVELEASEQUERY message over the connection.  In response, the
   server sends updates to the requestor using LEASEQUERY-REPLY and
   LEASEQUERY-DATA messages.  This response procedure is identical to
   [RFC5460], except that in the case of Active Leasequery the server
   sends updates whenever some activity occurs to change the binding
   state - thus the need for long lived connection.

   Active Leasequery is designed to
   provide continuous updates of DHCPv6 IPv6 binding activity to an
   external entity.

   Active Leasequery has features which allow this external entity to
   lose its connection and then reconnect and receive the latest
   information concerning any IPv6 bindings changed while it was not
   connected.

   These capabilities are designed to allow the Active Leasequery
   requestor to efficiently become current with respect to the lease
   state database after it has been restarted or the machine on which it
   is running has been reinitialized.  It is easy to define a protocol
   which works when the requestor is always connected to the DHCPv6
   server.  Since that isn't sufficiently robust, much of the mechanism
   in this document is designed to deal efficiently with situations that
   occur when the Active Leasequery requestor becomes disconnected from
   the DHCPv6 server from which it is receiving updates and then becomes
   reconnected to that server.

   Central to this approach, if the Active Leasequery requestor loses
   service, it is allowed to specify the time of its most recent update
   in a subsequent Active Leasequery request and the DHCPv6 server will
   determine whether or not data was missed while the Active Leasequery
   requestor was not connected.

   The DHCPv6 server processing the Active Leasequery request may limit
   the amount of data saved, and methods exist for the DHCPv6 server to
   inform the Active Leasequery requestor that more data was missed than
   could be saved.  In this situation, the Active Leasequery requestor
   would issue a Bulk Leasequery [RFC5460] to recover information not
   available through an Active Leasequery.

   DHCPv6 servers are not required to keep any data corresponding to
   data missed on a an Active Leasequery connection, but will typically
   choose to keep data corresponding to some recent activity available
   for subsequent queries by a DHCPv6 Active Leasequery requestor whose
   connection was temporarily interrupted.  In other words, DHCPv6
   servers supporting catch-up are required to have some mechanism to
   keep/save historic information of bindings.

   An Active Leasequery requestor would typically use Bulk Leasequery to
   initialize its database with all current data when that database
   contains no binding information.  In addition, it would use Bulk
   Leasequery to recover missed information in the event that its
   connection with the DHCPv6 server was lost for a longer time than the
   DHCPv6 server would keep track of the specific changes to the IPv6
   binding information.

   The messages sent by the server in response to an Active Leasequery
   request SHOULD be identical to the messages sent by the server to a
   Bulk Leasequery request regarding the way the data is encoded into
   the Active Leasequery responses.  In addition, the actions taken by
   the Active Leasequery requestor to interpret the responses to an
   Active Leasequery request SHOULD be identical to the way that the
   requestor interprets the responses to a Bulk Leasequery request.
   Thus, the handling of OPTION_CLIENT_DATA and additional options
   discussed in the Bulk Leasequery specification [RFC5460] are to be
   followed when implementing Active Leasequery.

4.  Interaction Between Active Leasequery and Bulk Leasequery

   Active Leasequery can be seen as an extension of the Bulk Leasequery
   protocol [RFC5460].  The format of packets returned to an Active
   Leasequery requestor are identical to that defined for the Bulk
   Leasequery protocol [RFC5460].

   Applications which employ Active Leasequery to keep a database up to
   date with respect to the DHCPv6 server's lease state database will
   usually use an initial Bulk Leasequery to bring their database into
   equivalence with that of the DHCPv6 server, and then use Active
   Leasequery to keep that database current with respect to the DHCPv6
   server's lease state database.

   There are several differences between the Active and Bulk Leasequery
   protocols.  Active Leasequery defines a new message
   (ACTIVELEASEQUERY) to send Active Leasequery request to DHCPv6
   server.  An Active Leasequery connection sends all available updates
   to the requestor, based on OPTION_LQ_QUERY option (see
   Section 6.2.1).

   An Active Leasequery connection does not ever "complete", though the
   DHCPv6 server may drop the connection for a variety of reasons
   associated with some sort of exception condition.

5.  Extension to DHCPv6 Bulk Leasequery

   This document extends to the capabilities of DHCPv6 Bulk Leasequery
   protocol [RFC5460] by defining new options. options (OPTION_LQ_BASE_TIME,
   OPTION_LQ_START_TIME and OPTION_LQ_END_TIME).  DHCPv6 server sends
   OPTION_LQ_BASE_TIME option in Bulk Leasequery response if requestor
   ask for the same in Bulk Leasequery request.  OPTION_LQ_START_TIME
   and OPTION_LQ_END_TIME can be used in Bulk Leasequery request made to
   DHCPv6 server.  More details about these options are specified in
   Section 6.3.

6.  Message and Option Definitions

6.1.  Message Framing for TCP

   The use of TCP for the Active Leasequery protocol permits one or more
   DHCPv6 messages to be sent at a time.  The receiver needs to be able
   to determine how large each message is.  The same message framing
   technique used for DHCPv6 Bulk Leasequery [RFC5460] is used for
   Active Leasequery as well.

   The intent in using the same format is that code which currently
   knows how to deal with a message returned from DHCPv6 Bulk Leasequery
   [RFC5460] will be able to deal with the message held inside of the
   TCP framing.

6.2.  Messages

   The LEASEQUERY-REPLY message is defined in [RFC5007].  The
   LEASEQUERY-DATA and LEASEQUERY-DONE messages are defined in
   [RFC5460].

   In a an Active Leasequery exchange, a single LEASEQUERY-REPLY message
   is used to indicate the success or failure of a query, and to carry
   data that do not change in the context of a single query and answer,
   such as the Server-ID and Client-ID options.  If a query is
   successful, only a single LEASEQUERY-REPLY message MUST appear.  If
   the server is returning binding data, the LEASEQUERY-REPLY also
   contains the first client's binding data in an OPTION_CLIENT_DATA
   option.  Additional binding data is returned using LEASEQUERY-DATA
   message as explained in DHCPv6 Bulk Leasequery [RFC5460].  In case of
   failure query, single LEASEQUERY-REPLY message is returned without
   any binding data.

6.2.1.  ACTIVELEASEQUERY

   The new message type (ACTIVELEASEQUERY) is designed to assist
   requestor for keeping the
   requestor up to date in real-time (or near real-time) with DHCPv6
   bindings.  It asks the server to return DHCPv6 bindings activity that
   occurs subsequent to the receipt of the Active Leasequery request.

   An ACTIVELEASEQUERY request MUST contain a transaction-id, and that
   transaction-id MUST BE locally unique to the TCP connection to the
   DHCPv6 server.

   While

   When sending an Active Leasequery request, the requestor MAY include
   the OPTION_LQ_START_TIME option in the ACTIVELEASEQUERY request.  In
   this case, DHCPv6 server returns all the bindings changed on or after
   the OPTION_LQ_START_TIME.

   If the requestor is interested in receiving all binding updates from
   the DHCPv6 server, it MUST NOT include the OPTION_LQ_QUERY option in
   the ACTIVELEASEQUERY message.  But if the requestor is only
   interested in specific binding updates, it MAY include an
   OPTION_LQ_QUERY option along with a query-types defined in [RFC5007]
   and [RFC5460].

   Other DHCPv6 options used in the LEASEQUERY message (as specified in
   [RFC5460]) can also be used in the ACTIVELEASEQUERY request.

6.3.  Options

   New options (OPTION_LQ_BASE_TIME, OPTION_LQ_START_TIME and
   OPTION_LQ_END_TIME) are defined as an extension to DHCPv6 Bulk
   Leasequery [RFC5460].  DHCPv6 server sends OPTION_LQ_BASE_TIME option
   in Active or Bulk Leasequery response if requestor ask for the same
   in Active or Bulk Leasequery request.  OPTION_LQ_START_TIME can be
   used in Active or Bulk Leasequery request made to DHCPv6 server.
   OPTION_LQ_END_TIME can be used in Bulk Leasequery request made to
   DHCPv6 server.  The reply messages for Active Leasequery uses
   these options along with the options defined in [RFC3315], [RFC5007]
   and [RFC5460].

6.3.1.  OPTION_LQ_BASE_TIME

   The OPTION_LQ_BASE_TIME option is the current time the message was
   created to be sent by the DHCPv6 server to the requestor of the
   Active or Bulk Leasequery. Leasequery if requestor ask for the same in Active or
   Bulk Leasequery request.  This MUST be an absolute time (i.e. seconds
   since midnight 1 Jan January 1, 2000 UTC modulo 2^32). UTC).  All of the other time based
   options in the reply message are relative to this time, including
   OPTION_CLT_TIME [RFC5007].  This time is in the context of the DHCPv6
   server who placed this option in a message.

   This is an unsigned integer in network byte order.

   The code for this option is TBD.  The length of this option is 4
   octets.

       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_LQ_BASE_TIME      |          option-len           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           base-time                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

        option-code       OPTION_LQ_BASE_TIME (TBD).
        option-len        4.
        base-time         DHCPv6 Server Base Time.

6.3.2.  OPTION_LQ_START_TIME

   The OPTION_LQ_START_TIME option specifies a query start time to the
   DHCPv6 server.  If specified, only bindings that have changed on or
   after the OPTION_LQ_START_TIME should be included in the response to
   the query.  This option MAY be used in Active or Bulk Leasequery
   requests made to a DHCPv6 server.

   The requestor MUST determine the OPTION_LQ_START_TIME using lease
   information it has received from the DHCPv6 server.  This MUST be an
   absolute time in the DHCPv6 server's context (see Section 8.4).

   Typically (though this is not a requirement) the OPTION_LQ_START_TIME
   option will contain the value most recently received in a
   OPTION_LQ_BASE_TIME option by the requestor, as this will indicate
   the last successful communication with the DHCPv6 server.

   This is an unsigned integer in network byte order.

   The code for this option is TBD.  The length of this option is 4
   octets.

       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_LQ_START_TIME     |          option-len           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                       query-start-time                        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

        option-code       OPTION_LQ_START_TIME (TBD).
        option-len        4.
        query-start-time  DHCPv6 Server Query Start Time.

6.3.3.  OPTION_LQ_END_TIME

   The OPTION_LQ_END_TIME option specifies a query end time to the
   DHCPv6 server.  If specified, only bindings that have changed on or
   before the OPTION_LQ_END_TIME should be included in the response to
   the query.  This option MAY be used in a Bulk Leasequery request.
   But it MUST NOT be used in an Active Leasequery request.

   The requestor MUST determine the OPTION_LQ_END_TIME based on lease
   information it has received from the DHCPv6 server.  This MUST be an
   absolute time in the context of the DHCPv6 server.

   In the absence of information to the contrary, the requestor SHOULD
   assume that the time context of the DHCPv6 server is identical to the
   time context of the requestor (see Section 8.4).

   This is an unsigned integer in network byte order.

   The code for this option is TBD.  The length of this option is 4
   octets.

       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_LQ_END_TIME       |          option-len           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                        query-end-time                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

        option-code       OPTION_LQ_END_TIME (TBD).
        option-len        4.
        query-end-time    DHCPv6 Server Query End Time.

6.4.  Connection and Transmission Parameters

   Active Leasequery uses the same port configuration as DHCPv6 Bulk
   Leasequery [RFC5460].  It also uses the other transmission parameters
   (BULK_LQ_DATA_TIMEOUT and BULK_LQ_MAX_CONNS) as defined in [RFC5460].

   This section presents a table of values used to control Active
   Leasequery behavior, including recommended defaults.  Implementations
   MAY make these values configurable.  However, configuring too-small
   timeout values may lead to harmful behavior both to this application
   as well as to other traffic in the network.  As a result, timeout
   values smaller than the default values are SHOULD NOT RECOMMENDED. be used.

   +------------------------+----------+-------------------------------+
   | Parameter              | Default  | Description
   ----------------------------------------------------------------------                   |
   +------------------------+----------+-------------------------------+
   | ACTIVE_LQ_RCV_TIMEOUT  | 120 secs | Active Leasequery receive     |
   |                        |          | timeout                       |
   | ACTIVE_LQ_SEND_TIMEOUT | 120 secs | Active Leasequery send        |
   |                        |          | timeout                       |
   | ACTIVE_LQ_IDLE_TIMEOUT | 60 secs  | Active Leasequery idle        |
   |                        |          | timeout                       |
   +------------------------+----------+-------------------------------+

7.  Information Communicated by Active Leasequery

   While the information communicated by a DHCPv6 Bulk Leasequery
   [RFC5460] is taken directly from the DHCPv6 server's lease state
   database, the information communicated by an Active Leasequery is
   real-time information.  As such, it is the information which is
   currently associated with a particular binding in the DHCPv6 server's
   lease state database.

   This is of significance, because if the Active Leasequery requestor
   runs slowly or the requestor disconnects from the DHCPv6 server and
   then reconnects with a an OPTION_LQ_START_TIME (signalling option (signaling a
   catch-up operation), the information communicated to the Active
   Leasequery requestor is only the most current information from the
   DHCPv6 server's lease state database.

   The requestor of an Active Leasequery MUST NOT assume that every
   lease state change is communicated across an Active Leasequery
   connection.  Even if the Active Leasequery requestor remains
   connected, the DHCPv6 server is only required to transmit information
   about a binding that is current when the packet is created and handed
   off to the TCP stack to send to the requestor.

   If the TCP connection blocks and the DHCPv6 server is waiting to send
   information down the connection, when the connection becomes
   available to be written the DHCPv6 server MAY create the packet to
   send at this time.  The current state of the binding will be sent,
   and any transition in state or other information that occurred while
   the TCP connection was blocked will be lost.

   Thus, the Active Leasequery protocol does not allow the requestor to
   build a complete history of every activity on every lease.  An
   effective history of the important state changes for a lease can be
   created if the parameters of the DHCPv6 server are tuned to take into
   account the requirements of an Active Leasequery requestor.  For
   instance, the period after the expiration or release of a binding
   could be configured long enough (say several minutes, well more than
   the receive timeout), so that an Active Leasequery requestor would
   never be
   less likely to miss any changes in the binding.

8.  Requestor Behavior

8.1.  Connecting and General Processing

   A Requestor attempts to establish a TCP connection to a DHCPv6 Server
   in order to initiate a an Active Leasequery exchange.  If the attempt
   fails, the Requestor MAY retry.

   If an Active Leasequery is terminated prematurely by a LEASEQUERY-
   DONE with a DHCPv6 status code (carried in an OPTION_STATUS_CODE
   option) of QueryTerminated or by the failure of the connection over
   which it was being submitted, the requestor MAY retry the request
   after the creation of a new connection.

   Messages from the DHCPv6 server come as multiple responses to a
   single ACTIVELEASEQUERY message.  Thus, each ACTIVELEASEQUERY request
   MUST have an xid (transaction-id) unique on the connection on which
   it is sent, and all of the messages which come as a response to it
   contain the same xid as the request.  It is the xid which allows the
   data-streams of two or more different ACTIVELEASEQUERY requests to be
   de-multiplexed by the requestor.

   A requestor MAY send a an ACTIVELEASEQUERY request to a DHCPv6 server
   and immediately close the transmission side of its TCP connection,
   and then read the resulting response messages from the DHCPv6 server.
   This is not required, and the usual approach is to leave both sides
   of the TCP connection up until at least the conclusion of the Active
   Leasequery.

8.2.  Forming an Active Leasequery

   The Active Leasequery is designed to create a long lived connection
   between the requestor and the DHCPv6 server processing the active
   query.  The DHCPv6 server will send binding information back across
   this connection with minimal delay after it learns of the binding
   information.  It will learn about bindings either because it makes
   the bindings itself or because it has received information about a
   binding from another server.

   To form the Active Leasequery, a DHCPv6 request is constructed with a
   message type of ACTIVELEASEQUERY.  The DHCPv6 request MUST contain a
   transaction-id, and that transaction-id MUST BE locally unique to the
   TCP connection to the DHCPv6 server.

   An important capability of the Active Leasequery is the ability of
   the requestor to specify that some recent data be sent immediately to
   the requestor in parallel with the transmission of the ongoing
   binding information in more or less real time.  This capability is
   used in order to allow an Active Leasequery requestor to recover
   missed information in the event that it temporarily loses
   connectivity with the DHCPv6 server processing a previous Active
   Leasequery.

   Note that until all of the recent data (catch-up data) has been
   received, the requestor MUST NOT keep track of the base-time
   (OPTION_LQ_BASE_TIME) received in Leasequery reply messages to use
   later in a subsequent Active Leasequery request.

   This capability is enabled by the transmission of a 4 octet an
   OPTION_LQ_BASE_TIME option with each Leasequery reply sent as the
   result of a previous Active Leasequery.  The requestor will typically
   keep track of the highest base-time received from a particular DHCPv6
   server over an Active Leasequery connection, and in the event that
   the requestor finds it necessary (for whatever reason) to reestablish
   an Active Leasequery connection to that DHCPv6 server, the requestor
   will place this highest base-time value into a an OPTION_LQ_START_TIME
   option in the new Active Leasequery request.

   If the requestor doesn't wish to request an update of information
   missed when it was not connected to the DHCPv6 server, then it does
   not include the OPTION_LQ_START_TIME option in the Active Leasequery
   request.

   If the TCP connection becomes blocked or stops being writable while
   the requestor is sending its query, the requestor SHOULD be prepared
   to terminate the connection after BULK_LQ_DATA_TIMEOUT.  We make this
   recommendation to allow requesters to control the period of time they
   are willing to wait before abandoning a connection, independent of
   notifications from the TCP implementations they may be using.

8.3.  Processing Active Replies

   The Requestor attempts to read a DHCPv6 LEASEQUERY-REPLY message from
   the TCP connection.  If the stream of replies becomes blocked, the
   Requestor SHOULD be prepared to terminate the connection after
   ACTIVE_LQ_RCV_TIMEOUT, and MAY begin retry processing if configured
   to do so.

   The requestor examines the LEASEQUERY-REPLY message, and determines
   how to proceed.  Message validation rules are specified in DHCPv6
   Leasequery [RFC5007] and DHCPv6 Bulk Leasequery [RFC5460].  If the
   reply contains an DHCPv6 status code (carried in an
   OPTION_STATUS_CODE option), the requestor follows the recommendations
   in [RFC5007].

   Note that an Active Leasequery request specifically requests the
   DHCPv6 server to create a long-lived connection which may not have
   data transferring continuously during its lifetime.  Therefore the
   DHCPv6 server will send a LEASEQUERY-DATA message without binding
   data (OPTION_CLIENT_DATA) every ACTIVE_LQ_IDLE_TIMEOUT seconds
   (default 60) in order for the requestor to know that the connection
   remains alive.  This approach is followed only when connection is
   idle (i.e. server has no binding data to send).  During normal
   binding data exchange, receiving of LEASEQUERY-DATA message by
   requestor itself signifies that connection is active.  Note that the
   default for ACTIVE_LQ_RCV_TIMEOUT is 120 seconds, twice the value of
   the ACTIVE_LQ_IDLE_TIMEOUT's default of 60 seconds which drives the
   DHCPv6 server to send messages.  Thus ACTIVE_LQ_RCV_TIMEOUT controls
   how sensitive the requestor is to be to delays by the DHCPv6 server
   in sending updates or LEASEQUERY-DATA messages.

   A single Active Leasequery can and usually will result in a large
   number of replies.  The Requestor MUST be prepared to receive more
   than one reply with transaction-ids matching a single
   ACTIVELEASEQUERY message from a single DHCPv6 server.

   An Active Leasequery has two regimes -- during the catch-up phase, if
   any, and after any catch-up phase.  During the catch-up phase (if one
   exists), the data returned in the OPTION_LQ_BASE_TIME option in a
   LEASEQUERY-REPLY or LEASEQUERY-DATA message may appear to be ordered,
   but the most recent change in the lease state data being returned is
   not related to the OPTION_LQ_BASE_TIME option value in the messages.
   Another way to say this is that the ordering of the updates sent by
   the DHCPv6 server during the catch-up phase is independent of the
   ordering in the changes in the lease state data.  The
   OPTION_LQ_BASE_TIME option from messages during this phase MUST NOT
   be saved and used in a subsequent ACTIVELEASEQUERY message's
   OPTION_LQ_START_TIME option as it does not represent the extent of
   progress of the catch-up activity.

   After the catch-up phase, or during the entire series of messages
   received as the response to a an Active Leasequery request with no
   OPTION_LQ_START_TIME (and therefore no catch-up phase), the
   OPTION_LQ_BASE_TIME option of the most recent message SHOULD be saved
   as a record of the most recent time that data was received.  This
   base-time (in the context of the DHCPv6 server) can be used in a
   subsequent Active Leasequery message's OPTION_LQ_START_TIME after a
   loss of the Active Leasequery connection.

   The LEASEQUERY-DONE message MAY unilaterally terminate a successful
   Active Leasequery request which is currently in progress in the event
   that the DHCPv6 server determines that it cannot continue processing
   a ACTIVELEASEQUERY request.  For example, when a server is requested
   to shut down it SHOULD send a LEASEQUERY-DONE message with a DHCPv6
   status code of QueryTerminated and include OPTION_LQ_BASE_TIME option
   in the message.  This SHOULD be the last message on that connection,
   and once the message has been transmitted, the server should close
   the connection.

   After receiving LEASEQUERY-DONE with a QueryTerminated status from a
   server, the Requestor MAY close the TCP connection to that server.

8.3.1.  Processing Replies from a Request Containing a
        OPTION_LQ_START_TIME

   If the Active Leasequery was requested with a OPTION_LQ_START_TIME, an OPTION_LQ_START_TIME
   option, the DHCPv6 server will attempt to send information about all
   bindings that changed since the time specified in the
   OPTION_LQ_START_TIME.  This is the catch-up phase of the Active
   Leasequery processing.  The DHCPv6 server MAY also begin immediate
   updates over the same connection of real-time binding information
   changes.  Thus, the catch-up phase may run in parallel with the
   normal updates generated by the Active Leasequery request.

   A DHCPv6 server MAY keep only a limited amount of time ordered
   information available to respond to an Active Leasequery request
   containing a OPTION_LQ_START_TIME. an OPTION_LQ_START_TIME option.  Thus, it is possible that
   the time specified in the OPTION_LQ_START_TIME option represents a
   time not covered by the time ordered information kept by the DHCPv6
   server.  If this should occur, and there is not enough data saved in
   the DHCPv6 server to satisfy the request specified by the
   OPTION_LQ_START_TIME option, the DHCPv6 server will reply immediately
   with a LEASEQUERY-REPLY message with a DHCPv6 status code of
   DataMissing with a base-time option equal to the server's current
   time.  This will signal the end of the catch-up phase, and the only
   updates that will subsequently be received on this connection are the
   real-time updates from the Active Leasequery request.

   If there is enough data saved to satisfy the request, then
   LEASEQUERY-REPLY (with OPTION_STATUS_CODE of Success or reply without
   OPTION_STATUS_CODE option) and LEASEQUERY-DATA messages will begin
   arrive from the DHCPv6 server.  Some of these messages will be
   related to the OPTION_LQ_START_TIME request and be part of the catch-
   up phase.  Some of these messages will be real-time updates of
   binding changes taking place in the DHCPv6 server.  In general, there
   is no way to determine the source of each message.

   Until the catch-up phase is complete, the latest base-time value
   received from a DHCPv6 server processing an Active Leasequery request
   cannot be reset from the incoming messages because to do so would
   compromise the ability to recover lost information if the Active
   Leasequery were to terminate prior to the completion of the catch-up
   phase.

   The requestor will know that the catch-up phase is complete when the
   DHCPv6 server will transmit a LEASEQUERY-DATA message with the DHCPv6
   status code of CatchUpComplete.  Once this message is transmitted,
   all additional LEASEQUERY-DATA messages will relate to real-time
   ("new") binding changes in the DHCPv6 server.

   As discussed in Section 8.3, the requestor SHOULD keep track of the
   latest base-time option value received over a particular connection,
   to be used in a subsequent Active Leasequery request -- but only if
   the catch-up phase is complete.  Prior to the completion of the
   catch-up phase, if the connection should go away or if the requestor
   receives a LEASEQUERY-DONE message, then when it reconnects it MUST
   use the base-time value from the previous connection and not any
   base-time value received from the recently closed connection.

   In the event that there was enough data available to the DHCPv6
   server to begin to satisfy the request implied by the
   OPTION_LQ_START_TIME option, but during the processing of that data
   the server found that it was unable to continue (perhaps there was
   barely enough, the connection is very slow, and the aging algorithm
   causes the saved data to become unavailable) the DHCPv6 server will
   terminate the catch-up phase of processing immediately by sending a
   LEASEQUERY-DATA message with a DHCPv6 status code of DataMissing and
   with a base-time option of the current time.

   The requestor MUST NOT assume that every individual state change of
   every binding during the period from the time specified in the
   OPTION_LQ_START_TIME and the present is replicated in an Active
   Leasequery reply message.  The requestor MAY assume that at least one
   Active Leasequery reply message will exist for every binding which
   had one or more changes of state during the period specified by the
   OPTION_LQ_START_TIME and the current time.  The last message for each
   binding will contain the state at the current time, and there may be
   one or more messages concerning a single binding during the catch-up
   phase of processing.

   If a binding changed state multiple times during the time that the
   requestor was not connected (that is, during the time from the
   OPTION_LQ_START_TIME and the present), then only the current binding
   information will be sent during the catch-up phase.  However, the
   requestor MUST NOT assume that every intermediate state change that
   occurred during the period from the OPTION_LQ_START_TIME to the
   present will be represented by an individual Leasequery message.

   If the LEASEQUERY-REPLY or LEASEQUERY-DATA message containing a
   DHCPv6 status code of DataMissing is received and the requestor is
   interested in keeping its database up to date with respect to the
   current state of bindings in the DHCPv6 server, then the requestor
   SHOULD issue a Bulk Leasequery request to recover the information
   missing from its database.  This Bulk Leasequery request should
   include a OPTION_LQ_START_TIME, set to be OPTION_LQ_START_TIME option with the same value as its the
   OPTION_LQ_START_TIME option previously included in the
   ACTIVELEASEQUERY responses from the DHCPv6 server, and a an
   OPTION_LQ_END_TIME option equal to the OPTION_LQ_BASE_TIME option
   returned by the DHCPv6 server in the LEASEQUERY-REPLY or LEASEQUERY-DATA LEASEQUERY-
   DATA message with the DHCPv6 status code of DataMissing.

   In the event that the requestor receives a LEASEQUERY-REPLY or
   LEASEQUERY-DATA message with a DHCPv6 status code of DataMissing, it
   is a reasonable assumption that it is interested in keeping its
   database up to date with respect to the DHCPv6 server's internal
   binding database or it would not have included the
   OPTION_LQ_START_TIME in the ACTIVELEASEQUERY message.

   Typically, the requestor would have one connection open to a DHCPv6
   server for a an Active Leasequery request and possibly one additional
   connection open for a Bulk Leasequery request to the same DHCPv6
   server to fill in the data that might have been missed prior to the
   initiation of the Active Leasequery.  The Bulk Leasequery connection
   would typically run to completion and be closed, leaving one Active
   Leasequery connection open to a single DHCPv6 server.  Alternatively,
   both requests could be issued over a single connection.

8.4.  Processing Time Values in Leasequery messages

   Active or Bulk Leasequery requests may be made to a DHCPv6 server
   whose absolute time may not be synchronized with the local time of
   the requestor.  Thus, there are at least two time contexts in even
   the simplest Active or Bulk Leasequery response.

   If the requestor of a an Active or Bulk Leasequery is saving the data
   returned in some form, it has a requirement to store a variety of
   time values, and some of these will be time in the context of the
   requestor and some will be time in the context of the DHCPv6 server.

   When receiving a an Active or Bulk Leasequery reply message from the
   DHCPv6 server, the message will contain a an OPTION_LQ_BASE_TIME
   option.  The time contained in this OPTION_LQ_BASE_TIME option is in
   the context of the DHCPv6 server.  As such, it is an ideal time to
   save and use as input to an Active or Bulk Leasequery message in the
   OPTION_LQ_START_TIME or OPTION_LQ_END_TIME option, should the
   requestor need to ever issue an Active or Bulk Leasequery message
   using these option as part of a later query, since these option
   requires a time in the context of the DHCPv6 server.

   In addition to saving the OPTION_LQ_BASE_TIME for possible future use
   in OPTION_LQ_START_TIME or OPTION_LQ_END_TIME option, the
   OPTION_LQ_BASE_TIME is used as part of the conversion of the other
   times in the Leasequery message to values which are meaningful in the
   context of the requestor.

   In systems whose clocks are synchronized, perhaps using NTP, the
   clock skew will usually be zero, which is not only acceptable, but
   desired.

8.5.  Examples

   These examples illustrate what a series of queries and responses
   might look like.  These are only examples -- there are no requirement
   that these sequence must be followed.

8.5.1.  Query Failure

   This example illustrates the message flows in case DHCPv6 server
   identifies that it can not cannot accept and/or process Active Leasequery
   request from the requestor.  This could be because of various reasons
   (i.e. UnknownQueryType, MalformedQuery, NotConfigured, NotAllowed).

      Client                          Server
      ------                          ------
      ACTIVELEASEQUERY xid 1  ----->
                              <-----  LEASEQUERY-REPLY xid 1 (w/error)

8.5.2.  Data Missing on Server

   This example illustrates the message flows in case DHCPv6 server
   identifies that it does not have enough data saved to satisfy the
   request specified by the OPTION_LQ_START_TIME option.

   In this case the DHCPv6 server will reply immediately with a
   LEASEQUERY-REPLY message with a DHCPv6 status code of DataMissing
   with a base-time option equal to the server's current time.  This
   will signal the end of the catch-up phase, and the only updates that
   will subsequently be received on this connection are the real-time
   updates from the Active Leasequery request.

      Client                          Server
      ------                          ------
      ACTIVELEASEQUERY xid 2  ----->
                              <-----  LEASEQUERY-REPLY xid 2 (w/error)
                              <-----  LEASEQUERY-DATA xid 2
                              <-----  LEASEQUERY-DATA xid 2
                              <-----  LEASEQUERY-DATA xid 2

8.5.3.  Successful Query

   This example illustrates the message flows in case of successful
   query processing by DHCPv6 server.

   In this case the DHCPv6 server will reply immediately with a
   LEASEQUERY-REPLY message (with OPTION_STATUS_CODE of Success or reply
   without OPTION_STATUS_CODE option), followed by binding data in
   LEASEQUERY-DATA messages.  In case, DHCPv6 server wants to abort in-
   process request and terminate the connection due to some reason, it
   sends LEASEQUERY-DONE with error code present in OPTION_STATUS_CODE
   option.

      Client                          Server
      ------                          ------
      ACTIVELEASEQUERY xid 3  ----->
                              <-----  LEASEQUERY-REPLY xid 3
                              <-----  LEASEQUERY-DATA xid 3
                              <-----  LEASEQUERY-DATA xid 3
                              <-----  LEASEQUERY-DATA xid 3
                              <-----  LEASEQUERY-DATA xid 3
                              <-----  LEASEQUERY-DONE xid 3 (w/error)

8.6.  Closing Connections

   The Requestor or DHCPv6 Leasequery server MAY close its end of the
   TCP connection at any time.  The Requestor MAY choose to retain the
   connection if it intends to issue additional queries.  Note that this
   requestor behavior does not guarantee that the connection will be
   available for additional queries: the server might decide to close
   the connection based on its own configuration.

9.  Server Behavior

   A DHCPv6 server which supports Active Leasequery MUST support DHCPv6
   Bulk Leasequery [RFC5460] and as well. extended herein.

9.1.  Accepting Connections

   Servers that implement DHCPv6 Active Leasequery listen for incoming
   TCP connections.  Approach used in accepting (or rejecting) the
   requestor connection is same as specified in DHCPv6 Bulk Leasequery
   [RFC5460].

9.2.  Replying to an Active Leasequery

   The DHCPv6 Leasequery [RFC5007] specification describes the initial
   construction of LEASEQUERY-REPLY messages.  Use of the LEASEQUERY-
   REPLY and LEASEQUERY-DATA messages to carry multiple bindings is
   described in DHCPv6 Bulk Leasequery [RFC5460].  Message transmission
   and framing for TCP is described in Section 6.1.

   If the connection becomes blocked while the server is attempting to
   send reply messages, the server SHOULD be prepared to terminate the
   TCP connection after ACTIVE_LQ_SEND_TIMEOUT.  This timeout governs
   how much congestion the DHCPv6 server is prepared to tolerate over
   any Active Leasequery connection.  The default is two minutes, which
   means that if more than two minutes goes by without the requestor
   reading enough information to unblock the TCP connection, the DHCPv6
   server will drop the TCP connection.

   If the DHCPv6 server encounters an error during initial processing of
   the ACTIVELEASEQUERY message, it SHOULD send a LEASEQUERY-REPLY
   message containing an error code of some kind in a DHCPv6 status code
   option.  It SHOULD close the connection after this error is
   signalled. signaled.

   If the DHCPv6 server encounters an error during later processing of
   the ACTIVELEASEQUERY message, it SHOULD send a LEASEQUERY-DONE
   containing an error code of some kind in a DHCPv6 status code option.
   It SHOULD close the connection after this error is signalled. signaled.

   If the server finds any bindings satisfying a query, it sends each
   binding's data in a reply message.  The first reply message is a
   LEASEQUERY-REPLY.  The binding data is carried in an
   OPTION_CLIENT_DATA option, as specified in [RFC5007].  The server
   returns subsequent bindings in LEASEQUERY-DATA messages, which can
   avoid redundant data (such as the requestor's Client-ID).

   Every reply to a an Active Leasequery request MUST contain the
   information specified in replies to a DHCPv6 Bulk Leasequery request
   [RFC5460].

   If an Active Leasequery or Bulk Leasequery request contains
   OPTION_LQ_BASE_TIME option code present in OPTION_ORO, the DHCPv6
   server MUST include OPTION_LQ_BASE_TIME option in every reply for
   this request.  The value for base-time option is current absolute
   time in the DHCPv6 server's context.

   If an Active Leasequery request contains a an OPTION_LQ_START_TIME
   option, it indicates that the requestor would like the DHCPv6 server
   to send it not only messages that correspond to DHCPv6 binding
   activity that occurs subsequent to the receipt of the Active
   Leasequery request, but also messages that correspond to DHCPv6
   binding activity that occurred prior to the Active Leasequery
   request.

   If OPTION_LQ_END_TIME option appears in a an Active Leasequery request,
   the DHCPv6 server should send a LEASEQUERY-REPLY message with a
   DHCPv6 status code of MalformedQuery and terminate the connection.

   In order to implement a meaningful response to this query, the DHCPv6
   server MAY keep track of the binding activity and associate changes
   with particular base-time values from the messages.  Then, when
   requested to do so by a an Active Leasequery request containing a
   OPTION_LQ_START_TIME option, the DHCPv6 server can respond with
   replies for all binding activity occurring on that
   OPTION_LQ_START_TIME or later times.

   These replies based on the OPTION_LQ_START_TIME MAY be interleaved
   with the messages generated due to current binding activity.

   Once the transmission of the DHCPv6 Leasequery messages associated
   with the OPTION_LQ_START_TIME option are complete, a LEASEQUERY-DATA
   message MUST be sent with a DHCPv6 status code value of
   CatchUpComplete.

   The DHCPv6 server SHOULD, but is not required to, keep track of a
   limited amount of previous binding activity.  The DHCPv6 server MAY
   choose to only do this in the event that it has received at least one
   Active Leasequery request in the past, as to do so will almost
   certainly entail some utilization of resources which would be wasted
   if there are no Active Leasequery requestors for this DHCPv6 server.
   The DHCPv6 server SHOULD make the amount of previous binding activity
   it retains configurable.  There is no requirement on the DHCPv6
   server to retain this information over a server restart (or even to
   retain such information at all).

   Unless there is an error or some requirement to cease processing a
   Active Leasequery request yielding a LEASEQUERY-DONE message, such as
   a server shutdown, there will be no LEASEQUERY-DONE message at the
   conclusion of the Active Leasequery processing because that
   processing will not conclude but will continue until either the
   requestor or the server drops the connection.

9.3.  Multiple or Parallel Queries

   Requesters may want to use an existing connection if they need to
   make multiple queries.  Servers MAY support reading and processing
   multiple queries from a single connection.  A server MUST NOT read
   more query messages from a connection than it is prepared to process
   simultaneously.

   Typically, a requestor of a an Active Leasequery would not need to send
   a second Active Leasequery while the first is still active.  However,
   sending an Active Leasequery and a Bulk Leasequery over the same
   connection would be possible and reasonable.  But it is RECOMMENDED
   to use different connection in case of parallel Active and Bulk
   Leasequeries.

   This MAY be a feature that is administratively controlled.  Servers
   that are able to process queries in parallel SHOULD offer
   configuration that limits the number of simultaneous queries
   permitted from any one requestor, in order to control resource use if
   there are multiple requesters seeking service.

9.4.  Closing Connections

   The server MUST close its end of the TCP connection if it encounters
   an error sending data on the connection.  The server MUST close its
   end of the TCP connection if it finds that it has to abort an in-
   process request.  A server aborting an in-process request SHOULD
   attempt to signal that to its requestors by using the QueryTerminated
   status code in the DHCPv6 status code option in a LEASEQUERY-DONE
   message.  If the server detects that the requestor end has been
   closed, the server MUST close its end of the connection after it has
   finished processing any outstanding requests from the requestor.

   The server SHOULD be prepared to limit the number of connections it
   maintains, and SHOULD be prepared to close idle connections to
   enforce the limit.

10.  Security Considerations

   The "Security Considerations" section of [RFC3315] details the
   general threats to DHCPv6.  The DHCPv6 Leasequery specification
   [RFC5007] describes recommendations for the Leasequery protocol,
   especially with regard to relayed Leasequery messages, mitigation of
   packet-flooding denial-of-service (DoS) attacks, restriction to
   trusted requestors, and use of IPsec [RFC4301].

   The use of TCP introduces some additional concerns.  Attacks that
   attempt to exhaust the DHCPv6 server's available TCP connection
   resources, such as SYN flooding attacks, can compromise the ability
   of legitimate requestors to receive service.  Malicious requestors
   who succeed in establishing connections, but who then send invalid
   queries, partial queries, or no queries at all also can exhaust a
   server's pool of available connections.  We recommend that servers
   offer configuration to limit the sources of incoming connections,
   that they limit the number of accepted connections and the number of
   in-process queries from any one connection, and that they limit the
   period of time during which an idle connection will be left open.

   There are two specific issues regarding Active Leasequery security
   that deserve explicit mention.  The first is preventing information
   that Active Leasequery can provide from reaching requestors who are
   not authorized to receive such information.  The second is ensuring
   that authorized requestors of the Active Leasequery capability
   receive accurate information from the Server (and that this
   information is not disrupted in transit).

   To prevent information leakage to unauthorized requestors, Servers
   SHOULD restrict Active Leasequery connections and ACTIVELEASEQUERY
   messages to certain requestors, either through explicit configuration
   of the Server itself or by employing external network elements to
   provide such restrictions.  In particular, the typical DHCPv6 client
   SHOULD NOT be allowed to receive a response to an Active Leasequery
   request, and some technique MUST exist to allow prevention of such
   access in any environment where Active Leasequery is deployed.

   Connections not from permitted requestors SHOULD be closed
   immediately, to avoid server connection resource exhaustion or
   alternatively, simply not be allowed to reach the server at all.
   Servers SHOULD have the capability to restrict certain requestors to
   certain query types.  Servers MAY reply to queries that are not
   permitted with the LEASEQUERY-DONE message with a status-code option
   status of NotAllowed, or MAY simply close the connection.

   To prevent interception, disruption and malicious corruption of
   Active Leasequery data flows between the server and authorized
   requestors these data flows SHOULD transit only secured networks.
   These data flows are typically infrastructure oriented, and there is
   usually no reason to have them flowing over networks where such
   attacks are likely.  In the rare cases where these data flows might
   need to be sent through unsecured networks, they MUST be sent over
   connections secured through means external to the DHCPv4/DHCPv6
   server and its requestor(s) (e.g., through VPN's).

   Authentication for DHCP Messages [RFC3315] MUST NOT be used to
   attempt to secure transmission of the messages described in this
   document.

11.  IANA Considerations

   IANA is requested to assign new DHCPv6 Option Codes in the registry
   maintained in http://www.iana.org/assignments/dhcpv6-parameters:

      OPTION_LQ_BASE_TIME

      OPTION_LQ_START_TIME

      OPTION_LQ_END_TIME

   IANA is requested to assign new values in the registry of DHCPv6
   Status Codes maintained in http://www.iana.org/assignments/
   dhcpv6-parameters:

      DataMissing

      CatchUpComplete

   IANA is requested to assign value for the following new DHCPv6
   Message type in the registry maintained in http://www.iana.org/
   assignments/dhcpv6-parameters:

      ACTIVELEASEQUERY

12.  Acknowledgements

   Some of the concept and content, present in this document, are based
   on DHCPv4 Active Leasequery which was originally proposed by Kim
   Kinnear, Bernie Volz, Mark Stapp and Neil Russell.

13.  Modification History

14.  References

14.1.  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.

   [RFC3633]  Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic
              Host Configuration Protocol (DHCP) version 6", RFC 3633,
              December 2003.

   [RFC5007]  Brzozowski, J., Kinnear, K., Volz, B., and S. Zeng,
              "DHCPv6 Leasequery", RFC 5007, September 2007.

   [RFC5460]  Stapp, M., "DHCPv6 Bulk Leasequery", RFC 5460, February
              2009.

14.2.  Informative References

   [RFC4301]  Kent, S. and K. Seo, "Security Architecture for the
              Internet Protocol", RFC 4301, December 2005.

   [RFC4614]  Duke, M., Braden, R., Eddy, W., and E. Blanton, "A Roadmap
              for Transmission Control Protocol (TCP) Specification
              Documents", RFC 4614, September 2006.

Authors' Addresses

   Dushyant Raghuvanshi
   Cisco Systems, Inc.
   Cessna Business Park,
   Varthur Hobli, Outer Ring Road,
   Bangalore, Karnataka  560037
   India

   Phone: +91 (080) 4365-7476
   Email: draghuva@cisco.com

   Kim Kinnear
   Cisco Systems, Inc.
   1414 Massachusetts Ave.
   Boxborough, Massachusetts  01719
   USA

   Phone: +1 (978) 936-0000
   Email: kkinnear@cisco.com

   Deepak Kukrety
   Cisco Systems, Inc.
   Cessna Business Park,
   Varthur Hobli, Outer Ring Road,
   Bangalore, Karnataka  560037
   India

   Phone: +91 (080) 4365-7474
   Email: dkukrety@cisco.com