GENWiki

Premier IT Outsourcing and Support Services within the UK

User Tools

Site Tools


rfc:rfc7653

Internet Engineering Task Force (IETF) D. Raghuvanshi Request for Comments: 7653 K. Kinnear Updates: 5460 D. Kukrety Category: Standards Track Cisco Systems, Inc. ISSN: 2070-1721 October 2015

                      DHCPv6 Active Leasequery

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 prior to the time the
 DHCPv6 server 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 updates DHCPv6 Bulk Leasequery (RFC 5460) by
 adding new options.

Status of This Memo

 This is an Internet Standards Track document.
 This document is a product of the Internet Engineering Task Force
 (IETF).  It represents the consensus of the IETF community.  It has
 received public review and has been approved for publication by the
 Internet Engineering Steering Group (IESG).  Further information on
 Internet Standards is available in Section 2 of RFC 5741.
 Information about the current status of this document, any errata,
 and how to provide feedback on it may be obtained at
 http://www.rfc-editor.org/info/rfc7653.

Raghuvanshi, et al. Standards Track [Page 1] RFC 7653 DHCPv6 Active Leasequery October 2015

Copyright Notice

 Copyright (c) 2015 IETF Trust and the persons identified as the
 document authors.  All rights reserved.
 This document is subject to BCP 78 and the IETF Trust's Legal
 Provisions Relating to IETF Documents
 (http://trustee.ietf.org/license-info) in effect on the date of
 publication of this document.  Please review these documents
 carefully, as they describe your rights and restrictions with respect
 to this document.  Code Components extracted from this document must
 include Simplified BSD License text as described in Section 4.e of
 the Trust Legal Provisions and are provided without warranty as
 described in the Simplified BSD License.

Raghuvanshi, et al. Standards Track [Page 2] RFC 7653 DHCPv6 Active Leasequery October 2015

Table of Contents

 1. Introduction ....................................................4
 2. Terminology .....................................................4
 3. Protocol Overview ...............................................6
 4. Interaction between Active Leasequery and Bulk Leasequery .......8
 5. Extension to DHCPv6 Bulk Leasequery .............................8
 6. Message and Option Definitions ..................................9
    6.1. Message Framing for TCP ....................................9
    6.2. Messages ...................................................9
         6.2.1. ACTIVELEASEQUERY ....................................9
         6.2.2. STARTTLS ...........................................10
         6.2.3. Response Messages ..................................10
    6.3. Options ...................................................10
         6.3.1. OPTION_LQ_BASE_TIME ................................10
         6.3.2. OPTION_LQ_START_TIME ...............................11
         6.3.3. OPTION_LQ_END_TIME .................................12
    6.4. Connection and Transmission Parameters ....................12
 7. Information Communicated by Active Leasequery ..................13
 8. Requestor Behavior .............................................14
    8.1. General Processing ........................................14
    8.2. Initiating a Connection ...................................14
    8.3. Forming an Active Leasequery ..............................15
    8.4. Processing Active Replies .................................16
         8.4.1. Processing Replies from a Request Containing an
                OPTION_LQ_START_TIME ...............................18
    8.5. Processing Time Values in Leasequery Messages .............20
    8.6. Examples ..................................................21
         8.6.1. Query Failure ......................................21
         8.6.2. Data Missing on Server .............................21
         8.6.3. Successful Query ...................................21
    8.7. Closing Connections .......................................22
 9. Server Behavior ................................................22
    9.1. Accepting Connections .....................................22
    9.2. Rejecting Connections .....................................24
    9.3. Replying to an Active Leasequery ..........................24
    9.4. Multiple or Parallel Queries ..............................26
    9.5. Closing Connections .......................................26
 10. Security Considerations .......................................27
 11. IANA Considerations ...........................................28
 12. References ....................................................28
    12.1. Normative References .....................................28
    12.2. Informative References ...................................29
 Acknowledgments ...................................................30
 Authors' Addresses ................................................30

Raghuvanshi, et al. Standards Track [Page 3] RFC 7653 DHCPv6 Active Leasequery October 2015

1. Introduction

 The DHCPv6 protocol [RFC3315] specifies a mechanism for the
 assignment of IPv6 address and configuration information to IPv6
 nodes.  IPv6 Prefix Delegation for DHCPv6 [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
 entities need to keep up with the current binding activity of the
 DHCPv6 server.  Keeping up with this 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 that is directly involved
 in the DHCPv6 client-server transactions (e.g., a relay agent), or it
 could be an external process that 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.
 This document updates DHCPv6 Bulk Leasequery [RFC5460] by adding new
 options, as described in Section 6.2.1.  For DHCPv6 servers
 supporting Bulk Leasequery and not Active Leasequery, Section 9.2
 specifies the mechanism to reject incoming Active Leasequery
 requests.

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 unsigned quantity containing the number of seconds since
    midnight (UTC), January 1, 2000, modulo 2^32.

Raghuvanshi, et al. Standards Track [Page 4] RFC 7653 DHCPv6 Active Leasequery October 2015

 o  Active Leasequery
    Keeping up to date in real time (or near real time) with DHCPv6
    binding activity.
 o  Bulk Leasequery
    Requesting and receiving information about all or some of the
    existing DHCPv6 binding information in an efficient manner, as
    defined by [RFC5460].
 o  blocked TCP connection
    A TCP connection is considered blocked if the underlying TCP
    transport will not accept new messages to be sent without blocking
    the thread that is attempting to send the message.
 o  binding change/update
    Any change in the DHCPv6 binding state.  This also includes
    expiration or deletion of the binding.
 o  catch-up information
    If a DHCPv6 Active Leasequery requestor sends an
    OPTION_LQ_START_TIME option in 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.
 o  catch-up phase
    The period while catch-up information 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 message is
    received by a requestor from a DHCPv6 server, a more accurate
    value is derived from continuously examining the instantaneous
    value developed from each message received from a DHCPv6 server

Raghuvanshi, et al. Standards Track [Page 5] RFC 7653 DHCPv6 Active Leasequery October 2015

    and using it to make small adjustments to the existing value held
    in the requestor.
 o  DHCPv6 binding state
    Data stored on the DHCPv6 server related to binding.
 o  requestor
    The node that sends LEASEQUERY messages to one or more servers to
    retrieve information on the bindings for a client.
 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 [RFC7414] connection required for Active
 Leasequery.  A DHCPv6 server that 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 similar to the
 procedure specified in [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 a long-lived
 connection.  Additionally, the Active Leasequery server SHOULD
 provide a mechanism to control which data is allowed to be included
 in the OPTION_CLIENT_DATA messages sent to the requestor.  See
 Section 9.3.
 Active Leasequery has features that 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.

Raghuvanshi, et al. Standards Track [Page 6] RFC 7653 DHCPv6 Active Leasequery October 2015

 These features 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 that
 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 reconnects
 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 data was missed (i.e.,
 not all data could be saved).  In this situation, the Active
 Leasequery requestor should 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 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

Raghuvanshi, et al. Standards Track [Page 7] RFC 7653 DHCPv6 Active Leasequery October 2015

 discussed in the Bulk Leasequery specification [RFC5460] are to be
 followed when implementing Active Leasequery, with the exception that
 a server responding to an Active Leasequery request SHOULD be able to
 be configured to prevent specific data items from being included in
 the OPTION_CLIENT_DATA option even if they were requested by
 inclusion in the OPTION_ORO option.

4. Interaction between Active Leasequery and Bulk Leasequery

 Active Leasequery is an extension of the Bulk Leasequery protocol
 [RFC5460].  The format of messages returned to an Active Leasequery
 requestor is identical to that defined for the Bulk Leasequery
 protocol [RFC5460].
 Applications that employ Active Leasequery to keep a database up to
 date with respect to the DHCPv6 server's lease state database should
 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 requests to the DHCPv6
 server.  An Active Leasequery connection sends all available updates
 to the requestor, based on the OPTION_LQ_QUERY option (see
 Section 6.2.1).
 An Active Leasequery connection does not ever "complete", though the
 DHCPv6 server can close the connection for a variety of reasons
 associated with some sort of exception condition.

5. Extension to DHCPv6 Bulk Leasequery

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

Raghuvanshi, et al. Standards Track [Page 8] RFC 7653 DHCPv6 Active Leasequery October 2015

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 in response to a single Active Leasequery
 request.  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 that 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.
 When using Transport Layer Security (TLS), once TLS negotiation
 completes, the connection will be encrypted and is now protected from
 eavesdropping, and normal Active Leasequery messages are sent and
 received using the TLS application data protocol services (see
 Section 10 of [RFC5246]).

6.2. Messages

6.2.1. ACTIVELEASEQUERY

 The new message type (ACTIVELEASEQUERY) is designed for keeping the
 requestor up to date in real time (or near real time) with DHCPv6
 bindings.  It asks the server to return DHCPv6 binding 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 on the TCP connection on which
 it is sent to the DHCPv6 server.
 When sending an ACTIVELEASEQUERY request, the requestor MAY include
 the OPTION_LQ_START_TIME option in the ACTIVELEASEQUERY request.  In
 this case, the 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 message.

Raghuvanshi, et al. Standards Track [Page 9] RFC 7653 DHCPv6 Active Leasequery October 2015

6.2.2. STARTTLS

 The new message type (STARTTLS) is designed for establishment of a
 TLS connection between a requestor and a DHCPv6 server.  The STARTTLS
 message SHOULD be sent without any options.  Any options received in
 a STARTTLS message SHOULD be ignored.
 More details about this message are specified in Section 8.2.

6.2.3. Response Messages

 The LEASEQUERY-REPLY message is defined in [RFC5007].  The
 LEASEQUERY-DATA and LEASEQUERY-DONE messages are defined in
 [RFC5460].
 In 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, the DHCPv6 server MUST respond to it with exactly one
 LEASEQUERY-REPLY message.  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 a LEASEQUERY-DATA message as explained in DHCPv6 Bulk
 Leasequery [RFC5460].  In case of a query failure, a single
 LEASEQUERY-REPLY message is returned without any binding data.

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].  The reply messages for Active Leasequery use
 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 if the requestor asked for the same in an
 Active or Bulk Leasequery request.  This MUST be an absolute time
 (i.e., seconds since midnight January 1, 2000 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 that placed this option in a message.
 This is an unsigned integer in network byte order.

Raghuvanshi, et al. Standards Track [Page 10] RFC 7653 DHCPv6 Active Leasequery October 2015

 The code for this option is 100.
     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 (100)
      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 8.5).
 Typically (though this is not a requirement), the
 OPTION_LQ_START_TIME option will contain the value most recently
 received in an 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 101.
     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 (101)
      option-len        4
      query-start-time  DHCPv6 Server Query Start Time

Raghuvanshi, et al. Standards Track [Page 11] RFC 7653 DHCPv6 Active Leasequery October 2015

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 8.5).
 This is an unsigned integer in network byte order.
 The code for this option is 102.
     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 (102)
      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
 and to other traffic in the network.  As a result, timeout values
 smaller than the default values SHOULD NOT be used.

Raghuvanshi, et al. Standards Track [Page 12] RFC 7653 DHCPv6 Active Leasequery October 2015

 +------------------------+----------+-------------------------------+
 | 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 that 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 an OPTION_LQ_START_TIME 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 message 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 message 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

Raghuvanshi, et al. Standards Track [Page 13] RFC 7653 DHCPv6 Active Leasequery October 2015

 the receive timeout), so that an Active Leasequery requestor would be
 less likely to miss any changes in the binding.

8. Requestor Behavior

8.1. General Processing

 A requestor attempts to establish a TCP connection to a DHCPv6 server
 in order to initiate an Active Leasequery exchange.  If the attempt
 fails, the requestor MAY retry.  Retries should not be more frequent
 than one every ACTIVE_LQ_IDLE_TIMEOUT.  See Section 6.4.
 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.  Retries should not be more
 frequent than one every ACTIVE_LQ_IDLE_TIMEOUT.  See Section 6.4.
 Messages from the DHCPv6 server come as multiple responses to a
 single ACTIVELEASEQUERY message.  Thus, each ACTIVELEASEQUERY request
 MUST have a transaction-id unique on the connection on which it is
 sent, and all of the messages that come as a response to it contain
 the same transaction-id as the request.

8.2. Initiating a Connection

 A requestor SHOULD be able to operate in either insecure or secure
 mode.  This MAY be a feature that is administratively controlled.
 When operating in insecure mode, the requestor SHOULD proceed to send
 an ACTIVELEASEQUERY message after the establishment of a TCP
 connection.
 When operating in secure mode, the requestor MUST attempt to
 negotiate a TLS [RFC5246] connection over the TCP connection.  If
 this negotiation fails, the requestor MUST close the TCP connection.
 The recommendations in [RFC7525] SHOULD be followed when negotiating
 this connection.
 A requestor requests the establishment of a TLS connection by sending
 the STARTTLS message to the DHCPv6 server as the first message over
 the TCP connection.  This message indicates to the DHCPv6 server that
 a TLS connection over this TCP connection is desired.  There are four
 possibilities after the requestor sends the STARTTLS message to the
 DHCPv6 server:
 1.  No response from the DHCPv6 server.

Raghuvanshi, et al. Standards Track [Page 14] RFC 7653 DHCPv6 Active Leasequery October 2015

 2.  The DHCPv6 server closes the TCP connection after it receives the
     STARTTLS message.
 3.  The DHCPv6 server responds with a REPLY [RFC3315] message with a
     DHCPv6 status code of TLSConnectionRefused.
 4.  The DHCPv6 server responds with a REPLY [RFC3315] message without
     a DHCPv6 status code, indicating success.
 In any of the first three possibilities, the DHCPv6 server can be
 assumed to not support TLS.  In this case, the requestor MUST close
 the TCP connection.
 In the final possibility, where the DHCPv6 server has responded with
 a REPLY message without a DHCPv6 status code in response to the
 requestor's STARTTLS message, the requestor SHOULD initiate the
 exchange of the messages involved in a TLS handshake [RFC5246].
 During the TLS handshake, the requestor MUST validate the DHCPv6
 server's digital certificate.
 If the handshake exchange yields a functioning TLS connection, then
 the requestor SHOULD transmit an ACTIVELEASEQUERY request over that
 TLS connection and use that TLS connection for all further
 interactions in which it engages with the DHCPv6 server over this TCP
 connection.
 If the handshake exchange does not yield a functioning TLS
 connection, then the requestor MUST close the TCP connection.

8.3. Forming an Active Leasequery

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

Raghuvanshi, et al. Standards Track [Page 15] RFC 7653 DHCPv6 Active Leasequery October 2015

 This capability is enabled by the transmission of an
 OPTION_LQ_BASE_TIME option with each Leasequery reply sent as the
 result of a previous Active Leasequery.  The requestor SHOULD 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
 SHOULD place this highest base-time value into an
 OPTION_LQ_START_TIME option in the new Active Leasequery request.
 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.
 If the requestor doesn't wish to request an update of information
 missed when it was not connected to the DHCPv6 server, then it SHOULD
 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 terminate
 the connection after BULK_LQ_DATA_TIMEOUT.  We make this
 recommendation to allow requestors 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.

8.4. 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 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 a DHCPv6 status code (carried in an OPTION_STATUS_CODE
 option), the requestor should follow the recommendations in
 [RFC5007].
 Note that the connection resulting from accepting an Active
 Leasequery request may be long-lived and may not have data
 transferring continuously during its lifetime.  Therefore, the DHCPv6
 server SHOULD 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.,

Raghuvanshi, et al. Standards Track [Page 16] RFC 7653 DHCPv6 Active Leasequery October 2015

 server has no binding data to send).  During a normal exchange of
 binding data, receiving a LEASEQUERY-DATA message 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 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.  If the Active Leasequery was
 requested with an OPTION_LQ_START_TIME option, the Active Leasequery
 starts out in the catch-up phase.  See Section 8.4.1 for information
 on processing during the catch-up phase, as well as how to determine
 when the catch-up phase is complete.
 The updates sent by the DHCPv6 server during the catch-up phase are
 not in the order that the lease state data was updated.  Therefore,
 the OPTION_LQ_BASE_TIME option from messages during this phase MUST
 NOT be saved and used to compute the subsequent ACTIVELEASEQUERY
 message's OPTION_LQ_START_TIME option.
 After the catch-up phase, or during the entire series of messages
 received as the response to 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 that is currently in progress in the event
 that the DHCPv6 server determines that it cannot continue processing
 an Active Leasequery 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 the
 OPTION_LQ_BASE_TIME option in the message.  This MUST be the last
 message on that connection, and once the message has been
 transmitted, the server MUST close the connection.
 After receiving LEASEQUERY-DONE with a QueryTerminated status from a
 server, the requestor MAY close the TCP connection to that server.

Raghuvanshi, et al. Standards Track [Page 17] RFC 7653 DHCPv6 Active Leasequery October 2015

8.4.1. Processing Replies from a Request Containing an

      OPTION_LQ_START_TIME
 If the Active Leasequery was requested with 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 send information
 about real-time binding updates over the same connection.  Thus, the
 catch-up phase can 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 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.  In such case, when 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
 the OPTION_STATUS_CODE option) and LEASEQUERY-DATA messages will
 begin to 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.
 The updates sent by the DHCPv6 server during the catch-up phase are
 not in the order that the binding data was updated.  Therefore, 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 (and used in a subsequent Active
 Leasequery's query-start-time option), 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 transmits a LEASEQUERY-DATA message with the DHCPv6
 status code of CatchUpComplete (or a LEASEQUERY-REPLY message with a

Raghuvanshi, et al. Standards Track [Page 18] RFC 7653 DHCPv6 Active Leasequery October 2015

 DHCPv6 status code of DataMissing, as discussed above).  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 8.4, 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 (during transmission,
 the aging algorithm causes [some of] 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 that 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 can be
 one or more messages concerning a single binding during the catch-up
 phase of processing.
 Bindings can change multiple times while the requestor is not
 connected (that is, during the time from the OPTION_LQ_START_TIME to
 the present).  The requestor will only receive information about the
 current state of the binding, not information about each state change
 that occurred during the period from the OPTION_LQ_START_TIME to the
 present.
 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 an OPTION_LQ_START_TIME option with the same value as the

Raghuvanshi, et al. Standards Track [Page 19] RFC 7653 DHCPv6 Active Leasequery October 2015

 OPTION_LQ_START_TIME option previously included in the Active
 Leasequery responses from the DHCPv6 server and 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 message with the
 DHCPv6 status code of DataMissing.
 Typically, the requestor would have one connection open to a DHCPv6
 server for 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.

8.5. Processing Time Values in Leasequery Messages

 Active or Bulk Leasequery requests can 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 an Active or Bulk Leasequery is saving the data
 returned in some form, it has a requirement to store a variety of
 time values; 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 an Active or Bulk Leasequery reply message from the
 DHCPv6 server, the message will contain 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 options should the
 requestor need to ever issue an Active or Bulk Leasequery message
 using these options as part of a later query, since these options
 require a time in the context of the DHCPv6 server.
 In addition to saving the OPTION_LQ_BASE_TIME for possible future use
 in the OPTION_LQ_START_TIME or OPTION_LQ_END_TIME options, the
 OPTION_LQ_BASE_TIME option is used as part of the conversion of the
 other times in the Leasequery message to values that are meaningful
 in the context of the requestor.
 In systems whose clocks are synchronized, perhaps using the Network
 Time Protocol (NTP), the clock skew will usually be zero, which is
 not only acceptable, but desired.

Raghuvanshi, et al. Standards Track [Page 20] RFC 7653 DHCPv6 Active Leasequery October 2015

8.6. Examples

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

8.6.1. Query Failure

 This example illustrates the message flows in case the DHCPv6 server
 identifies that it cannot accept and/or process an Active Leasequery
 request from the requestor.  This could be because of various reasons
 (i.e., UnknownQueryType, MalformedQuery, NotConfigured, NotAllowed,
 and NotSupported).
    Client                          Server
    ------                          ------
    ACTIVELEASEQUERY xid 1  ----->
                            <-----  LEASEQUERY-REPLY xid 1 (w/error)

8.6.2. Data Missing on Server

 This example illustrates the message flows in case the 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

8.6.3. Successful Query

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

Raghuvanshi, et al. Standards Track [Page 21] RFC 7653 DHCPv6 Active Leasequery October 2015

 LEASEQUERY-DATA messages.  In case the DHCPv6 server wants to abort
 an in-process request and terminate the connection due to some
 reason, it sends LEASEQUERY-DONE with an error code present in the
 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)

8.7. 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 that supports Active Leasequery MUST support DHCPv6
 Bulk Leasequery [RFC5460] along with the updates mentioned in this
 document.

9.1. Accepting Connections

 DHCPv6 servers that implement DHCPv6 Active Leasequery listen for
 incoming TCP connections.  The approach used in accepting the
 requestor's connection is the same as specified in DHCPv6 Bulk
 Leasequery [RFC5460], with the exception that support for Active
 Leasequery MUST NOT be enabled by default and MUST require an
 explicit configuration step to be performed before it will operate.
 DHCPv6 servers SHOULD be able to operate in either insecure or secure
 mode.  This MAY be a mode that is administratively controlled, where
 the server will require a TLS connection to operate or will only
 operate without a TLS connection.  In either case, operation in
 insecure mode MUST NOT be the default, even if operation in secure
 mode is not supported.  Operation in insecure mode MUST always
 require an explicit configuration step, separate from the
 configuration step required to enable support for Active Leasequery.

Raghuvanshi, et al. Standards Track [Page 22] RFC 7653 DHCPv6 Active Leasequery October 2015

 When operating in insecure mode, the DHCPv6 server simply waits for
 the requestor to send the Active Leasequery request after the
 establishment of a TCP connection.  If it receives a STARTTLS
 message, it MUST respond with a REPLY [RFC3315] message with a DHCPv6
 status code of TLSConnectionRefused.
 When operating in secure mode, DHCPv6 servers MUST support TLS
 [RFC5246] to protect the integrity and privacy of the data
 transmitted over the TCP connection.  When operating in secure mode,
 DHCPv6 servers MUST be configurable with regard to which requestors
 they will communicate.  The certificate presented by a requestor when
 initiating the TLS connection is used to distinguish between
 acceptable and unacceptable requestors.
 When operating in secure mode, the DHCPv6 server MUST begin to
 negotiate a TLS connection with a requestor who asks for one and MUST
 close the TCP connections that are not secured with TLS or for which
 the requestor's certificate is deemed unacceptable.  The
 recommendations in [RFC7525] SHOULD be followed when negotiating a
 TLS connection.
 A requestor will request a TLS connection by sending a STARTTLS as
 the first message over a newly created TCP connection.  If the DHCPv6
 server supports TLS connections and has not been configured to not
 allow them on this link, the DHCPv6 server MUST respond to this
 STARTTLS message by sending a REPLY [RFC3315] message without a
 DHCPv6 status code back to the requestor.  This indicates to the
 requestor that the DHCPv6 server will support the negotiation of a
 TLS connection over this existing TCP connection.
 If for some reason the DHCPv6 server cannot support a TLS connection
 or has been configured to not support a TLS connection, then it
 SHOULD send a REPLY message with a DHCPv6 status code of
 TLSConnectionRefused back to the requestor.
 In the event that the DHCPv6 server sends a REPLY message without a
 DHCPv6 status code option included (which indicates success), the
 requestor is supposed to initiate a TLS handshake [RFC5246] (see
 Section 8.2).  During the TLS handshake, the DHCPv6 server MUST
 validate the requestor's digital certificate.  In addition, the
 digital certificate presented by the requestor is used to decide if
 this requestor is allowed to perform an Active Leasequery.  If this
 requestor's certificate is deemed unacceptable, the server MUST abort
 the creation of the TLS connection.
 All TLS connections established between a requestor and a DHCPv6
 server for the purposes of supporting Active Leasequery MUST be
 mutually authenticated.

Raghuvanshi, et al. Standards Track [Page 23] RFC 7653 DHCPv6 Active Leasequery October 2015

 If the TLS handshake is not successful in creating a TLS connection,
 the server MUST close the TCP connection.

9.2. Rejecting Connections

 Servers that do not implement DHCPv6 Active and Bulk Leasequery
 SHOULD NOT listen for incoming TCP connections for these requests.
 If the DHCPv6 server supporting Bulk Leasequery and not Active
 Leasequery receives an Active Leasequery request, it SHOULD send a
 LEASEQUERY-REPLY with a DHCPv6 status code of NotSupported.  It
 SHOULD close the TCP connection after this error is signaled.

9.3. 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 terminate the TCP connection
 after ACTIVE_LQ_SEND_TIMEOUT.  This timeout governs for how long the
 DHCPv6 server is prepared to wait for the requestor to read and
 process enough information to unblock the TCP 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 SHOULD close the TCP
 connection.
 If the DHCPv6 server encounters an error during the 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 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 signaled.
 If the server finds any bindings satisfying a query, it SHOULD send
 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
 SHOULD send subsequent bindings in LEASEQUERY-DATA messages, which
 can avoid redundant data (such as the requestor's Client-ID).

Raghuvanshi, et al. Standards Track [Page 24] RFC 7653 DHCPv6 Active Leasequery October 2015

 Every reply to an Active Leasequery request MUST contain the
 information specified in replies to a DHCPv6 Bulk Leasequery request
 [RFC5460], with the exception that a server implementing Active
 Leasequery SHOULD be able to be configured to prevent specific data
 items from being sent to the requestor even if these data items were
 requested in the OPTION_ORO option.
 Some servers can be configured to respond to a DHCPv6 Leasequery
 [RFC5007] and DHCPv6 Bulk Leasequery [RFC5460] for an IPv6 binding
 that is reserved in such a way that it appears that the IPv6 binding
 is leased to the DHCP client for which it is reserved.  These servers
 SHOULD also respond to an Active Leasequery request with the same
 information as they would to a Bulk Leasequery request when they
 first determine that the IPv6 binding is reserved to a DHCP client.
 If an Active Leasequery or Bulk Leasequery request contains the
 OPTION_LQ_BASE_TIME option code present in OPTION_ORO, the DHCPv6
 server MUST include the OPTION_LQ_BASE_TIME option in every reply for
 this request.  The value for the base-time option is the current
 absolute time in the DHCPv6 server's context.
 If an Active Leasequery request contains 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 the OPTION_LQ_END_TIME option appears in 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 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.

Raghuvanshi, et al. Standards Track [Page 25] RFC 7653 DHCPv6 Active Leasequery October 2015

 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 that 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 closes the connection.

9.4. Multiple or Parallel Queries

 Every Active Leasequery request MUST be made on a single TCP
 connection where there is no other request active at the time the
 request is made.
 Typically, a requestor of 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 in parallel would
 be possible and reasonable.  In case of parallel Active and Bulk
 Leasequeries, the requestor MUST use different TCP connections.
 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 requestors seeking service.

9.5. 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

Raghuvanshi, et al. Standards Track [Page 26] RFC 7653 DHCPv6 Active Leasequery October 2015

 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.
 The server SHOULD limit the number of connections it maintains and
 SHOULD 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 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 can also exhaust a server's pool of available
 connections.
 When operating in secure mode, TLS [RFC5246] is used to secure the
 connection.  The recommendations in [RFC7525] SHOULD be followed when
 negotiating a TLS connection.
 Servers SHOULD offer configuration parameters to limit the sources of
 incoming connections through validation and use of the digital
 certificates presented to create a TLS connection.  They SHOULD also
 limit the number of accepted connections and limit the period of time
 during which an idle connection will be left open.
 The data acquired by using an Active Leasequery is subject to the
 same potential abuse as the data held by the DHCPv6 server from which
 it was acquired and SHOULD be secured by mechanisms as strong as
 those used for the data held by that DHCPv6 server.  The data
 acquired by using an Active Leasequery SHOULD be deleted as soon as
 possible after the use for which it was acquired has passed.
 Authentication for DHCP messages [RFC3315] MUST NOT be used to
 attempt to secure transmission of the messages described in this
 document.

Raghuvanshi, et al. Standards Track [Page 27] RFC 7653 DHCPv6 Active Leasequery October 2015

11. IANA Considerations

 IANA has assigned new DHCPv6 option codes in the "Option Codes"
 registry maintained at <http://www.iana.org/assignments/
 dhcpv6-parameters>:
    OPTION_LQ_BASE_TIME (100)
    OPTION_LQ_START_TIME (101)
    OPTION_LQ_END_TIME (102)
 IANA has assigned new values in the DHCPv6 "Status Codes" registry
 maintained at <http://www.iana.org/assignments/dhcpv6-parameters>:
    DataMissing (12)
    CatchUpComplete (13)
    NotSupported (14)
    TLSConnectionRefused (15)
 IANA has assigned values for the following new DHCPv6 message types
 in the "Message Types" registry maintained at
 <http://www.iana.org/assignments/dhcpv6-parameters>:
    ACTIVELEASEQUERY (22)
    STARTTLS (23)

12. References

12.1. Normative References

 [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
            Requirement Levels", BCP 14, RFC 2119,
            DOI 10.17487/RFC2119, March 1997,
            <http://www.rfc-editor.org/info/rfc2119>.
 [RFC3315]  Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins,
            C., and M. Carney, "Dynamic Host Configuration Protocol
            for IPv6 (DHCPv6)", RFC 3315, DOI 10.17487/RFC3315, July
            2003, <http://www.rfc-editor.org/info/rfc3315>.

Raghuvanshi, et al. Standards Track [Page 28] RFC 7653 DHCPv6 Active Leasequery October 2015

 [RFC3633]  Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic
            Host Configuration Protocol (DHCP) version 6", RFC 3633,
            DOI 10.17487/RFC3633, December 2003,
            <http://www.rfc-editor.org/info/rfc3633>.
 [RFC5007]  Brzozowski, J., Kinnear, K., Volz, B., and S. Zeng,
            "DHCPv6 Leasequery", RFC 5007, DOI 10.17487/RFC5007,
            September 2007, <http://www.rfc-editor.org/info/rfc5007>.
 [RFC5246]  Dierks, T. and E. Rescorla, "The Transport Layer Security
            (TLS) Protocol Version 1.2", RFC 5246,
            DOI 10.17487/RFC5246, August 2008,
            <http://www.rfc-editor.org/info/rfc5246>.
 [RFC5460]  Stapp, M., "DHCPv6 Bulk Leasequery", RFC 5460,
            DOI 10.17487/RFC5460, February 2009,
            <http://www.rfc-editor.org/info/rfc5460>.
 [RFC7525]  Sheffer, Y., Holz, R., and P. Saint-Andre,
            "Recommendations for Secure Use of Transport Layer
            Security (TLS) and Datagram Transport Layer Security
            (DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May
            2015, <http://www.rfc-editor.org/info/rfc7525>.

12.2. Informative References

 [RFC4301]  Kent, S. and K. Seo, "Security Architecture for the
            Internet Protocol", RFC 4301, DOI 10.17487/RFC4301,
            December 2005, <http://www.rfc-editor.org/info/rfc4301>.
 [RFC7414]  Duke, M., Braden, R., Eddy, W., Blanton, E., and A.
            Zimmermann, "A Roadmap for Transmission Control Protocol
            (TCP) Specification Documents", RFC 7414,
            DOI 10.17487/RFC7414, February 2015,
            <http://www.rfc-editor.org/info/rfc7414>.

Raghuvanshi, et al. Standards Track [Page 29] RFC 7653 DHCPv6 Active Leasequery October 2015

Acknowledgments

 Some of the concepts 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.
 Useful review comments were provided by Scott Bradner, Francis
 Dupont, and Stephen Farrell.  The privacy protections were
 substantially upgraded due to these comments and discussions.

Authors' Addresses

 Dushyant Raghuvanshi
 Cisco Systems, Inc.
 Cessna Business Park
 Varthur Hobli, Outer Ring Road
 Bangalore, Karnataka  560037
 India
 Phone: +91 80 4426-7372
 Email: draghuva@cisco.com
 Kim Kinnear
 Cisco Systems, Inc.
 1414 Massachusetts Avenue
 Boxborough, Massachusetts  01719
 United States
 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 80 4426-7346
 Email: dkukrety@cisco.com

Raghuvanshi, et al. Standards Track [Page 30]

/data/webs/external/dokuwiki/data/pages/rfc/rfc7653.txt · Last modified: 2015/10/14 23:39 by 127.0.0.1

Donate Powered by PHP Valid HTML5 Valid CSS Driven by DokuWiki