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Bulk DHCPv4 Lease Query
draft-ietf-dhc-dhcpv4-bulk-leasequery-05

The information below is for an old version of the document.
Document Type
This is an older version of an Internet-Draft that was ultimately published as RFC 6926.
Authors Kim Kinnear , Bernie Volz , Mark Stapp , Bharat Joshi , Neil Russell , Pavan Kurapati
Last updated 2012-02-16 (Latest revision 2011-11-18)
Replaces draft-dtv-dhc-dhcpv4-bulk-leasequery, draft-kinnear-dhc-dhcpv4-bulk-leasequery
RFC stream Internet Engineering Task Force (IETF)
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IESG IESG state Became RFC 6926 (Proposed Standard)
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Needs a YES. Needs 10 more YES or NO OBJECTION positions to pass.
Responsible AD Ralph Droms
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Send notices to dhc-chairs@tools.ietf.org, draft-ietf-dhc-dhcpv4-bulk-leasequery@tools.ietf.org
draft-ietf-dhc-dhcpv4-bulk-leasequery-05
DHC Working Group                                            Kim Kinnear
Internet Draft                                               Bernie Volz
Intended Status: Standards Track                              Mark Stapp
Expires: May 18, 2012                                Cisco Systems, Inc.
                                                                  D. Rao
                                                                B. Joshi
                                               Infosys Technologies Ltd.
                                                            Neil Russell
                                                                   Nokia
                                                             P. Kurapati
                                                   Juniper Networks Ltd.
                                                       November 18, 2011

                        Bulk DHCPv4 Lease Query
             <draft-ietf-dhc-dhcpv4-bulk-leasequery-05.txt>

Status of this Memo

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

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
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   Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
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Copyright Notice

   Copyright (c) 2011 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

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   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.

Abstract

   The Dynamic Host Configuration Protocol for IPv4 (DHCPv4) Leasequery
   extension allows a requestor to request information about DHCPv4
   bindings. This mechanism is limited to queries for individual
   bindings. In some situations individual binding queries may not be
   efficient, or even possible. This document extends the DHCPv4
   Leasequery protocol to allow for bulk transfer of DHCPv4 address
   binding data via TCP.

Table of Contents

    1.  Introduction................................................. 3
    2.  Terminology.................................................. 4
    3.  Design Goals................................................. 7
    3.1.  Information Acquisition before Data Starts................. 7
    3.2.  Lessen need for Caching and Negative Caching............... 7
    3.3.  Antispoofing in 'Fast Path'................................ 7
    3.4.  Minimize data transmission................................. 7
    4.  Protocol Overview............................................ 8
    5.  Interaction Between UDP Leasequery and Bulk Leasequery....... 9
    6.  Message and Option Definitions............................... 10
    6.1.  Message Framing for TCP.................................... 10
    6.2.  New or Changed Options..................................... 11
    6.3.  Connection and Transmission Parameters..................... 19
    7.  Requestor Behavior........................................... 19
    7.1.  Connecting and General Processing.......................... 19
    7.2.  Forming a Bulk Leasequery.................................. 20
    7.3.  Processing Bulk Replies.................................... 22
    7.4.  Processing Time Values in Leasequery messages.............. 24
    7.5.  Querying Multiple Servers.................................. 25
    7.6.  Making Sense Out of Multiple Responses Concerning a Single. 25
    7.7.  Multiple Queries to a Single Server over One Connection.... 26
    7.8.  Closing Connections........................................ 27

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    8.  Server Behavior.............................................. 27
    8.1.  Accepting Connections...................................... 27
    8.2.  Replying to a Bulk Leasequery.............................. 28
    8.3.  Building a Single Reply for Bulk Leasequery................ 31
    8.4.  Multiple or Parallel Queries............................... 32
    8.5.  Closing Connections........................................ 33
    9.  Security Considerations...................................... 33
    10.  IANA Considerations......................................... 34
    11.  Acknowledgements............................................ 36
    12.  References.................................................. 36
    12.1.  Normative References...................................... 36
    12.2.  Informative References.................................... 37

1.  Introduction

   The DHCPv4 protocol [RFC2131] [RFC2132] specifies a mechanism for the
   assignment of IPv4 address and configuration information to IPv4
   nodes.  DHCPv4 servers maintain authoritative binding information.

      +--------+
      | DHCPv4 |     +--------------+
      | Server |-...-|    DSLAM     |
      |        |     |  Relay Agent |
      +--------+     +--------------+
                          |        |
                      +------+   +------+
                      |Modem1|   |Modem2|
                      +------+   +------+
                         |        |    |
                      +-----+  +-----+ +-----+
                      |Node1|  |Node2| |Node3|
                      +-----+  +-----+ +-----+

                  Figure 1:  Example DHCPv4 configuration

   DHCPv4 relay agents receive DHCPv4 messages and frequently append a
   relay agent information option [RFC3046] before relaying them to the
   configured DHCPv4 servers (see Figure 1). In this process, some relay
   agents also glean lease information sent by the server and cache it
   locally. This information is used for a variety of purposes.   Two
   examples are prevention of spoofing attempts from the DHCPv4 clients,
   and installation of routes. When a relay agent reboots, this
   information is frequently lost.

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   The DHCPv4 Leasequery capability [RFC4388] extends the basic DHCPv4
   capability to allow an external entity, such as a relay agent, to
   query a DHCPv4 server to recover lease state information about a
   particular IP address or client in near real-time.

   The existing query types in Leasequery are typically data driven; the
   relay agent initiates the Leasequery when it receives data traffic
   from or to the client.  This approach may not scale well when there
   are thousands of clients connected to the relay agent or when the
   relay agent has a need to rebuild its internal data store prior to
   processing traffic in one direction or another.

   Some applications require the ability to query the server without
   waiting for traffic from or to clients. This query capability in turn
   requires an underlying transport more suitable to the bulk
   transmission of data.

   This document extends the DHCPv4 Leasequery protocol to add support
   for queries that address these additional requirements.  There may be
   many thousands of DHCPv4 bindings returned as the result of a single
   request, so TCP [RFC4614] is specified for efficiency of data
   transfer.  We define several additional query types, each of which
   can return multiple responses, in order to meet a variety of
   requirements.

2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in RFC
   2119 [RFC2119].

   This document uses the following terms:

      o "absolute time"

        A 32-bit quantity containing the number of seconds since Jan 1,
        1970.

      o "access concentrator"

        An access concentrator is a router or switch at the broadband
        access provider's edge of a public broadband access network.
        This document assumes that the access concentrator includes the
        DHCPv4 relay agent functionality.  For example, a CMTS (Cable
        Modem Termination System) in Cable environment or a DSLAM
        (Digital Subscriber Line Access Multiplexer) in a DSL

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        environment.

      o "active binding"

        An IP address with an active binding refers to an IP address
        which is currently associated with a DHCPv4 client where that
        DHCPv4 client has the right to use the IP address.

      o "Bulk Leasequery"

        Requesting and receiving the existing DHCPv4 address binding
        information in an efficient manner.

      o "clock skew"

        The difference between the absolute time on a DHCPv4 server and
        the absolute time on the system where a requestor of a Bulk
        Leasequery is executing is termed the "clock skew" for that Bulk
        Leasequery connection.  It is not absolutely constant but is
        likely to vary only slowly.  It is possible that, when both
        systems run NTP, the clock skew is negligible, and this is not
        only acceptable, but desired.

        While it is easy to think that this can be calculated precisely
        after one message is received by a requestor from a DHCPv4
        server, a more accurate value is derived from continuously
        examining the instantaneous value developed from each message
        received from a DHCPv4 server and using it to make small
        adjustments to the existing value held in the requestor.

      o "Default VPN"

        Indicates that the address being described belongs to the set of
        addresses not part of any VPN.  In other words, the normal
        address space operated on by DHCP.  This includes private
        addresses, for example the 10.x.x.x addresses as well as the
        other private subnets that are not routed on the open internet.

      o "DHCPv4 client"

        A DHCPv4 client is an Internet node using DHCPv4 to obtain
        configuration parameters such as a network address.

      o "DHCPv4 relay agent"

        A DHCPv4 relay agent is a third-party agent that transfers BOOTP
        and DHCPv4 messages between clients and servers residing on
        different subnets, per [RFC951] and [RFC1542].

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      o "DHCPv4 server"

        A DHCPv4 server is an Internet node that returns configuration
        parameters to DHCPv4 clients.

      o "DSLAM"

        Digital Subscriber Line Multiplexer.

      o "downstream"

        Refers to a direction away from the central part of a network
        and toward the edge.  In a DHCPv4 context, typically refers to a
        network direction which is away from the DHCPv4 server.

      o "Global VPN"

        Another name for the "Default VPN".

      o "IP address"

        In this document, the term "IP address" refers to an IPv4 IP
        address.

      o "IP address binding"

        The information that a DHCPv4 server keeps regarding the
        relationship between a DHCPv4 client and an IP address.  This
        includes the identity of the DHCPv4 client and the expiration
        time, if any, of any lease that client has on a particular IP
        address.  In some contexts, this may include information on IP
        addresses that are currently associated with DHCPv4 clients, and
        in others it may also include IP addresses with no current
        association to a DHCPv4 client.

      o "MAC address"

        In the context of a DHCPv4 message, a MAC address consists of
        the fields: hardware type "htype", hardware length "hlen", and
        client hardware address "chaddr".

      o "upstream"

        Refers to a direction toward the central part of a network and
        away from the edge.  In a DHCPv4 context, typically refers to a
        network direction which is toward the DHCPv4 server.

      o "stable storage"

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        Stable storage is used to hold information concerning IP address
        bindings (among other things) so that this information is not
        lost in the event of a failure which requires restart of the
        network element.  DHCPv4 servers are typically expected to have
        high speed access to stable storage, while relay agents and
        access concentrators usually do not have access to stable
        storage, although they may have periodic access to such storage.

      o "xid"

        Transaction-id.  The term "xid" refers to the DHCPv4 field
        containing the transaction-id of the message.

3.  Design Goals

   The goal of this document is to provide a lightweight mechanism for
   an Access Concentrator or other network element to retrieve IP
   address binding information available in the DHCPv4 server.  The
   mechanism should also allow an Access Concentrator to retrieve
   consolidated IP address binding information for either the entire
   access concentrator or a single connection/circuit.

3.1.  Information Acquisition before Data Starts

   The existing data driven approach required by [RFC4388] means that
   the Leasequeries can only be performed after an Access Concentrator
   receives data. To implement antispoofing, the concentrator must drop
   packets for each client until it gets lease information from the
   DHCPv4 server for that client. If an Access Concentrator finishes the
   Leasequeries before it starts receiving data, then there is no need
   to drop legitimate packets. In this way, outage time may be reduced.

3.2.  Lessen need for Caching and Negative Caching

   The result of a single Leasequery should be cached, whether that
   results in a positive or negative cache, in order to remember that
   the Leasequery was performed.  This caching is required to limit the
   traffic imposed upon a DHCPv4 server by Leasequeries for information
   already received.

   These caches not only consume precious resources, they also need to
   be managed.  Hence they should be avoided as much as possible.

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3.3.  Antispoofing in 'Fast Path'

   If Antispoofing is not done in the fast path, it will become a
   bottleneck and may lead to denial of service of the access
   concentrator.  The Leasequeries should make it possible to do
   antispoofing in the fast path.

3.4.  Minimize data transmission

   It may be that a network element is able to periodically save its
   entire list of assigned IP addresses to some form of stable storage.
   In this case, it will wish to recover all of the updates to this
   information without duplicating the information it has recovered from
   its own stable storage.

   Bulk Leasequery allows the specification of a query-start-time as
   well as a query-end-time.  Use of query-times allows a network
   element that periodically commits information to stable storage to
   recover just what it lost since the last commit.

4.  Protocol Overview

   The DHCPv4 Bulk Leasequery mechanism is modeled on the existing
   individual DHCPv4 Leasequery protocol in [RFC4388] as well as related
   work on DHCPv6 Bulk Leasequery [RFC5460]. A Bulk Leasequery requestor
   opens a TCP connection to a DHCPv4 Server, using the DHCPv4 port 67.
   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 DHCPv4 server.  No relaying of
   Bulk Leasequery messages is specified.

   After establishing a connection, the requestor sends a
   DHCPBULKLEASEQUERY message over the connection.

   The server uses the message type and additional data in the DHCPv4
   DHCPBULKLEASEQUERY message to identify any relevant bindings.

   In order to support some query types, servers may have to maintain
   additional data structures or otherwise be able to locate bindings
   that have been requested by the Leasequery requestor.

   Relevant bindings are returned in DHCPv4 packets with either the
   DHCPLEASEACTIVE message type for an IP address with a currently
   active lease or, in some situations, a DHCPLEASEUNASSIGNED message
   type for an IP address which is controlled by the DHCPv4 server but

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   which is not actively leased by a DHCPv4 client at the present time.

   The Bulk Leasequery mechanism is designed to provide an external
   entity with information concerning existing DHCPv4 IPv4 address
   bindings managed by the DHCPv4 server.  When complete, the DHCPv4
   server will send a DHCPLEASEQUERYDONE message.  If a connection is
   lost while processing a Bulk Leasequery, the Bulk Leasequery must be
   retried as there is no provision for determining the extent of data
   already received by the requestor for a Bulk Leasequery.

   Bulk Leasequery supports queries by MAC address and by Client
   Identifier in a way similar to [RFC4388].  The Bulk Leasequery
   protocol also adds several new queries.

      o Query by Relay Identifier

        This query asks a server for the bindings associated with a
        specific relay agent; the relay agent is identified by a DUID
        carried in a Relay-ID sub-option [RelayId]. Relay agents can
        include this sub-option while relaying messages to DHCPv4
        servers.  Servers can retain the Relay-ID and associate it with
        bindings made on behalf of the relay agent's clients. The
        bindings returned are only those for DHCPv4 clients with a
        currently active binding.

      o Query by Remote ID

        This query asks a server for the bindings associated with a
        Relay Agent Remote-ID sub-option [RFC3046] value. The bindings
        returned are only those for DHCPv4 clients with a currently
        active binding.

      o Query for All Configured IP Addresses

        This query asks a server for information concerning all IP
        addresses configured in that DHCPv4 server, by specifying no
        other type of query. In this case, the bindings returned are for
        all configured IP addresses, whether or not they contain a
        currently active binding to a DHCPv4 client, since one point of
        this type of query is to update an existing database with
        changes after a particular point in time.

   Any of the above queries can be qualified by the specification of a
   query-start-time or a query-end-time (or both). When these timers are
   used as qualifiers, they indicate that a binding should be included
   if it changed on or after the query-start-time and on or before the
   query-end-time.

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   In addition, any of the above queries can be qualified by the
   specification of a vpn-id option [VpnId] to select the VPN on which
   the query should be processed.  The vpn-id option is also extended to
   allow queries across all available VPNs. In the absence of any vpn-id
   option, only the default (global) VPN is used to satisfy the query.

5.  Interaction Between UDP Leasequery and Bulk Leasequery

   Bulk Leasequery can be seen as an extension of the existing UDP
   Leasequery protocol [RFC4388].  This section clarifies the
   relationship between the two protocols.

   Only the DHCPBULKLEASEQUERY request is supported over the Bulk
   Leasequery connection. No other DHCPv4 requests are supported.  The
   Bulk Leasequery connection is not an alternative DHCPv4 communication
   option for clients seeking other DHCPv4 services.

   Two of the query-types introduced in the UDP Leasequery protocol can
   be used in the Bulk Leasequery protocol -- query by MAC address and
   query by client-id.

   The contents of the reply messages are similar between the existing
   UDP Leasequery protocol and the Bulk Leasequery protocol, though more
   information is returned in the Bulk Leasequery messages.

   One change in behavior for these existing queries is required when
   Bulk Leasequery is used.  [RFC4388], in sections 6.1, 6.4.1, and
   6.4.2 specifies the use of an associated-ip option in DHCPLEASEACTIVE
   messages in cases where multiple bindings were found.  When Bulk
   Leasequery is used, this mechanism is not necessary; a server
   returning multiple bindings simply does so directly as specified in
   this document.  The associated-ip option MUST NOT appear in Bulk
   Leasequery replies.

   Implementors should note that the TCP message framing defined in
   Section 4.1 is not compatible with the UDP message format.  If a TCP-
   framed request is sent as a UDP message, it may not be valid, because
   protocol fields will be offset by the message-size prefix.

6.  Message and Option Definitions

6.1.  Message Framing for TCP

   The use of TCP for the Bulk Leasequery protocol permits multiple
   messages to be sent from one end of the connection to the other
   without requiring a request/response paradigm as does UDP DHCPv4

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   [RFC2131].  The receiver needs to be able to determine the size of
   each message it receives.  Two octets containing the message size in
   network byte-order are prepended to each DHCPv4 message sent on a
   Bulk Leasequery TCP connection. The two message-size octets 'frame'
   each DHCPv4 message.

   The maximum message size is 65535 octets.

   DHCPv4 message framed for TCP:

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         message-size          |    op (1)     |   htype (1)   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   hlen (1)    |   hops (1)    |              ....             |
      +---------------+---------------+                               +
      |                                                               |
      .                  remainder of DHCPv4 message,
      .                   from Figure 1 of [RFC2131]                  .
      .                                                               .
      .                           (variable)                          .
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

           message-size    the number of octets in the message that
                           follows, as a 16-bit integer in network
                           byte-order.

           All other fields are as specified in DHCPv4 [RFC2131].

                  Figure 2:  Format of a DHCPv4 message in TCP

   The intent in using this format is that code which currently knows
   how to deal with sending or receiving a message in [RFC2131] format
   will easily be able to deal with the message contained in the TCP
   framing.

6.2.  New or Changed Options

   The existing messages DHCPLEASEUNASSIGNED and DHCPLEASEACTIVE are
   used as the value of the dhcp-message-type option to indicate an IP
   address which is currently not leased or currently leased to a DHCPv4
   client, respectively [RFC4388].

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   Additional options have also been defined to enable the Bulk
   Leasequery protocol to communicate useful information to the
   requestor.

6.2.1.  dhcp-message-type

   The dhcp-message-type option (option 53) from Section 9.6 of
   [RFC2132] requires new values.  The values of these message types are
   shown below in an extension of the table from Section 9.6 of
   [RFC2132]:

            Value   Message Type
            -----   ------------
            TBD8    DHCPBULKLEASEQUERY
            TBD9    DHCPLEASEQUERYDONE

6.2.2.  status-code

   The status code option allows a machine readable value to be returned
   regarding the status of a DHCPBULKLEASEQUERY request.

   This option has two possible scopes when used with Bulk Leasequery,
   depending on the context in which it appears.  It refers to the
   information in a single Leasequery reply if the value of the dhcp-
   message-type is DHCPLEASEACTIVE or DHCPLEASEUNASSIGNED.  It refers to
   the message stream related to an entire request if the value of the
   dhcp-message-type is DHCPLEASEQUERYDONE.

   The code for this option is TBD1. The length of this option is a
   minimum of 1 octet.

                     Status           Status
       Code    Len    Code            Message
      +------+------+------+------+------+--   --+-----+
      | TBD1 | n+1  |status|  s1  |  s2  |  ...  | sn  |
      +------+------+------+------+------+--   --+-----+

   The status-code is an octet defined in the table below.  The Status
   Message is an optional UTF-8 encoded text string suitable for display
   to an end user, which MUST NOT be null-terminated.

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     Name    Status Code Description
     ----    ----------- -----------
     Success         000 Success.  Also signaled by absence of
                         a status-code option.

     UnspecFail      001 Failure, reason unspecified.

     QueryTerminated 002 Indicates that the server is unable to
                         perform a query or has prematurely terminated
                         the query for some reason (which should be
                         communicated in the text message).

     MalformedQuery  003 The query was not understood.

     NotAllowed      004 The query or request was understood but was
                         not allowed in this context.

   A status-code option MAY appear in the options field of a DHCPv4
   message.  If the status-code option does not appear, it is assumed
   that the operation was successful.  The status-code option SHOULD NOT
   appear in a message which is successful unless there is some text
   string that needs to be communicated to the requestor.

6.2.3.  base-time

   The base-time option is the current time the message was created to
   be sent by the DHCPv4 server to the requestor of the Bulk Leasequery.
   This MUST be an absolute time. All of the other time based options in
   the reply message are relative to this time, including the dhcp-
   lease-time [RFC2132] and client-last-transaction-time [RFC4388].
   This time is in the context of the DHCPv4 server who placed this
   option in a message.

   This is an integer in network byte order.

   The code for this option is TBD2. The length of this option is 4
   octets.

                       DHCPv4 Server
       Code   Len        base-time
      +-----+-----+-----+-----+-----+-----+
      | TBD2|  4  |  t1 |  t2 |  t3 |  t4 |
      +-----+-----+-----+-----+-----+-----+

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6.2.4.  start-time-of-state

   The start-time-of-state option allows the receiver to determine the
   time at which the IP address made the transition into its current
   state.

   This MUST NOT be an absolute time, which is equivalent to saying that
   this MUST NOT be an absolute number of seconds since Jan 1, 1970.
   Instead, this MUST be the integer number of seconds from the time the
   IP address transitioned its current state to the time specified in
   the base-time option in the same message.

   This is an integer in network byte order.

   The code for this option is TBD3. The length of this option is 4
   octets.

                     Seconds in the past
       Code   Len      from base-time
      +-----+-----+-----+-----+-----+-----+
      | TBD3|  4  |  t1 |  t2 |  t3 |  t4 |
      +-----+-----+-----+-----+-----+-----+

6.2.5.  query-start-time

   The query-start-time option specifies a start query time to the
   DHCPv4 server.  If specified, only bindings that have changed on or
   after the query-start-time should be included in the response to the
   query.

   The requestor MUST determine the query-start-time using lease
   information it has received from the DHCPv4 server.  This MUST be an
   absolute time in the DHCPv4 server's context (see Section 7.4).

   Typically (though this is not a requirement) the query-start-time
   option will contain the value most recently received in a base-time
   option by the requestor, as this will indicate the last successful
   communication with the DHCP server.

   This MUST be an absolute time.

   This is an integer in network byte order.

   The code for this option is TBD4. The length of this option is 4
   octets.

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                         DHCPv4 Server
       Code   Len      query-start-time
      +-----+-----+-----+-----+-----+-----+
      | TBD4|  4  |  t1 |  t2 |  t3 |  t4 |
      +-----+-----+-----+-----+-----+-----+

6.2.6.  query-end-time

   The query-end-time option specifies an end query time to the DHCPv4
   server.  If specified, only bindings that have changed on or before
   the query-end-time should be included in the response to the query.

   The requestor MUST determine the query-end-time based on lease
   information it has received from the DHCPv4 server.  This MUST be an
   absolute time in the context of the DHCPv4 server.

   In the absence of information to the contrary, the requestor SHOULD
   assume that the time context of the DHCPv4 server is identical to the
   time context of the requestor (see Section 7.4).

   This is an integer in network byte order.

   The code for this option is TBD5. The length of this option is 4
   octets.

                         DHCPv4 Server
       Code   Len       query-end-time
      +-----+-----+-----+-----+-----+-----+
      | TBD5|  4  |  t1 |  t2 |  t3 |  t4 |
      +-----+-----+-----+-----+-----+-----+

6.2.7.  dhcp-state

   The dhcp-state option allows greater detail to be returned than
   allowed by the DHCPLEASEACTIVE and DHCPLEASEUNASSIGNED message types.

   The code for this option is TBD6. The length of this option is 1
   octet.

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       0                   1                   2
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |     TBD6      |    Length     |    State      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

        TBD6     The option code.

        Length   The option length, 1 octet.

        State    The State of the IP address.

      Value  State
      -----  -----
        1   AVAILABLE   Address is available to local DHCPv4 server
        2   ACTIVE      Address is assigned to a DHCPv4 client
        3   EXPIRED     Lease has expired
        4   RELEASED    Lease has been released by DHCPv4 client
        5   ABANDONED   Server or client flagged address as unusable
        6   RESET       Lease was freed by some external agent
        7   REMOTE      Address is available to a remote DHCPv4 server
        8   TRANSITIONING Address is moving between states

   Note that some of these states may be transient and may not appear in
   normal use.   A DHCPv4 server MUST implement at least the AVAILABLE
   and ACTIVE states, and SHOULD implement at least the ABANDONED and
   RESET states.

   Note the states AVAILABLE and REMOTE are relative to the current
   server.  An address that is available to the current server should
   show AVAILABLE on that server, and if another server is involved with
   that address as well, on that other server it should show as REMOTE.

   The dhcp-state option SHOULD contain ACTIVE when it appears in a
   DHCPLEASEACTIVE message.  A DHCPv4 server MAY choose to not send a
   dhcp-state option in a DHCPLEASEACTIVE message, and a requestor
   SHOULD assume that the dhcp-state is ACTIVE if no dhcp-state option
   appears in a DHCPLEASEACTIVE message.

   The reference to local and remote relate to possible use in an
   environment that includes multiple servers cooperating to provide an
   increased availability solution.  In this case, an IP address with
   the state of AVAILABLE is available to the local server, while one
   with the state of REMOTE is available to a remote server.  Usually,
   an IP address which is AVAILABLE on one server would be REMOTE on any
   remote server.  The TRANSITIONING state is also likely to be useful
   in multiple server deployments, where sometimes one server must

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   interlock a state change with one or more other servers.  Should a
   Bulk Leasequery need to send information concerning the state of the
   IP address during this period, it SHOULD use the TRANSITIONING state,
   since the IP address is likely to be neither ACTIVE or AVAILABLE.

   There is no requirement for the state of an IP address to transition
   in a well defined way from state to state.  To put this another way,
   you cannot draw a simple state transition graph for the states of an
   IP address and the requestor of a Leasequery MUST NOT depend on one
   certain state always following a particular previous state.  In
   general, every state can (at times) follow every other state.

6.2.8.  data-source

   The data-source option contains information about the source of the
   data in a DHCPLEASEACTIVE or a DHCPLEASEUNASSIGNED message.  It is
   used when there are two or more servers who might have information
   about a particular IP address binding.  Frequently two servers work
   together to provide an increased availability solution for the DHCPv4
   service, and in these cases, both servers will respond to Bulk
   Leasequery requests for the same IP address.

   The data contained in this option will allow an external process to
   better discriminate between the information provided by each of the
   servers servicing this IPv4 address.

   The code for this option is TBD7. The length of this option is 1
   octet.

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         0                   1                   2
         0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |     TBD7      |    Length     |     Flags     |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

          TBD7     The option code.

          Length   The option length, 1 octet.

          Flags    The Source information for this message.

                      0 1 2 3 4 5 6 7
                     +-+-+-+-+-+-+-+-+
                     |    MBZ      |R|
                     +-+-+-+-+-+-+-+-+

                     R:  REMOTE flag

                          remote = 1
                          local = 0

                     MBZ:  MUST BE ZERO (reserved for future use)

   The REMOTE flag is used to indicate where the most recent change of
   state (or other interesting change) concerning this IPv4 address took
   place.  If the value is local, then the change took place on the
   server from which this message was transmitted.  If the value is
   remote, then the change took place on some other server, and was made
   known to the server from which this message was transmitted.

   If this option was requested and it doesn't appear, the requestor
   MUST consider that the data-source was local.

6.2.9.  Virtual Subnet Selection Type and Information

   All of the (sub)options defined in [VpnId] carry identical payloads,
   consisting of a type and additional VSS (Virtual Subnet Selection)
   information.  The existing table is extended (see below) with a new
   type 254 to allow specification of a type code which indicates that
   all VPN's are to be used to process the Bulk Leasequery.

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                Type    VSS Information format:
                ----    -----------------------
                0       UTF-8 ASCII VPN identifier
                1       RFC 2685 VPN-ID
     CHANGED -> 2-253   Not Allowed
         NEW -> 254     All VPN's (wildcard)
                255     Global, default VPN

6.3.  Connection and Transmission Parameters

   DHCPv4 servers that support Bulk Leasequery SHOULD listen for
   incoming TCP connections on the DHCPv4 server port 67.
   Implementations MAY offer to make the incoming port configurable, but
   port 67 MUST be the default.  Requestors SHOULD make TCP connections
   to port 67, and MAY offer to make the destination server port
   configurable.

   This section presents a table of values used to control Bulk
   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 NOT RECOMMENDED.

   Parameter             Default   Description
   -------------------------------------------
   BULK_LQ_DATA_TIMEOUT  300 secs  Bulk Leasequery data timeout
                                   for both client and server
                                   (see Sections 7 and 8)
   BULK_LQ_MAX_CONNS     10        Max Bulk Leasequery TCP connections
                                   at the server side (see Section 8.1)

7.  Requestor Behavior

7.1.  Connecting and General Processing

   A Requestor attempts to establish a TCP connection to a DHCPv4 Server
   in order to initiate a Leasequery exchange.  If the attempt fails,
   the Requestor MAY retry.

   If Bulk Leasequery is terminated prematurely by a DHCPLEASEQUERYDONE

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   with a status-code option with a status-code 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 DHCPv4 server come as multiple responses to a
   single DHCPBULKLEASEQUERY message. Thus, each DHCPBULKLEASEQUERY
   request MUST have an xid (transaction-id) unique on the connection on
   which it is sent.   All of the messages which come as a response to
   that message will contain the same xid as the request. It is the xid
   which allows the data-streams of two different DHCPBULKLEASEQUERY
   requests to be demultiplexed by the requestor.

7.2.  Forming a Bulk Leasequery

   Bulk Leasequery is designed to create a connection which will
   transfer the state of some subset (or possibly all) of the IP address
   bindings from the DHCPv4 server to the requestor.  The DHCPv4 server
   will send all of the requested IPv4 address bindings across this
   connection with minimal delay after it receives the request.  In this
   context, "all IP address binding information" means information about
   all IPv4 addresses configured within the DHCPv4 server which meet the
   specified query criteria.  For some query criteria, this may include
   IP address binding information for IP addresses which may not now
   have or ever had have an association with a specific DHCPv4 client.

   To form the Bulk query, a DHCPv4 request is constructed with a dhcp-
   message-type of DHCPBULKLEASEQUERY. The query SHOULD have a dhcp-
   parameter-request-list to inform the DHCPv4 server which DHCPv4
   options are of interest to the requestor sending the
   DHCPBULKLEASEQUERY message.  The dhcp-parameter-request-list in a
   DHCPBULKLEASEQUERY message SHOULD contain the codes for base-time,
   dhcp-lease-time, start-time-of-state, and client-last-transaction-
   time.

   A DHCPBULKLEASEQUERY request is constructed of one primary query and
   optionally one or more qualifiers for it.

   The possible primary queries are listed below.  Each
   DHCPBULKLEASEQUERY request MUST contain only one of these primary
   queries.

      o Query by MAC address

        In a Query by MAC address, the chaddr, htype, and hlen of the
        DHCPv4 packet are filled in with the values requested.

      o Query by Client-Id

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        In a Query by Client-Id, a dhcp-client-id option containing the
        requested value is included in the DHCPBULKLEASEQUERY request.

      o Query by Remote-Id

        In a Query by Remote-Id, a remote-id sub-option containing the
        requested value is included in the relay-agent-information
        option of the DHCPBULKLEASEQUERY request.

      o Query by Relay-Id

        In a Query by Relay-Id, a relay-id sub-option [RelayId]
        containing the requested value is included in the relay-agent-
        information option of the DHCPBULKLEASEQUERY request.

      o Query for All Configured IP Addresses

        A Query for All Configured IP addresses is signaled by the
        absence of any other primary query.

   There are three qualifiers which can be applied to any of the above
   primary queries.  These qualifiers can appear individually or
   together in any combination, but only one of each can appear.

   o Query Start Time

     Inclusion of a query-start-time option specifies that only IP
     address bindings which have changed on or after the time specified
     in the query-start-time option should be returned.

   o Query End Time

     Inclusion of a query-end-time option specifies that only IP address
     bindings which have changed on or before the time specified in the
     query-end-time option should be returned.

   o VPN Id

     If no vpn-id option appears in the DHCPBULKLEASEQUERY, the default
     (global) VPN is searched to satisfy the query specified by the
     DHCPBULKLEASEQUERY. Using the vpn-id option [VpnId] allows the
     requestor to specify a single VPN other than the default VPN.  In
     addition, the vpn-id option has been extended as part of this
     document to allow specification that all configured VPN's be
     searched in order to satisfy the query specified in the
     DHCPBULKLEASEQUERY.

     In all cases, any message returned from a DHCPBULKLEASEQUERY

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     request containing information about an IP address for other than
     the default (global) VPN MUST contain a vpn-id option in the
     message.

   Use of the query-start-time or the query-end-time options or both can
   serve to reduce the amount of data transferred over the TCP
   connection by a considerable amount.

   The TCP connection may become blocked or stop being writable while
   the requestor is sending its query.   Should this happen, the
   implementation's behavior is controlled by the current value of
   BULK_LQ_DATA_TIMEOUT.  The default value is given elsewhere in this
   document, and this value may be overridden by local configuration of
   the operator.

   If this situation is detected, the requestor SHOULD start a timer
   using the current value of BULK_LQ_DATA_TIMEOUT.  If that timer
   expires, the requestor SHOULD terminate the connection.

7.3.  Processing Bulk Replies

   The requestor attempts to read a DHCPv4 Leasequery reply message from
   the TCP connection.

   The TCP connection may stop delivering reply data (i.e., the
   connection stops being readable).  Should this happen, the
   implementation's behavior is controlled by the current value of
   BULK_LQ_DATA_TIMEOUT.  The default value is given elsewhere in this
   document, and this value may be overridden by local configuration of
   the operator.

   If this situation is detected, the requestor SHOULD start a timer
   using the current value of BULK_LQ_DATA_TIMEOUT.  If that timer
   expires, the requestor SHOULD terminate the connection.

   A single Bulk Leasequery can and usually will result in a large
   number of replies.  The requestor MUST be prepared to receive more
   than one reply with an xid matching a single DHCPBULKLEASEQUERY
   message from a single DHCPv4 server. If the xid in the received
   message does not match an outstanding DHCPBULKLEASEQUERY message, the
   requestor MUST close the TCP connection.

   The DHCPv4 server MUST send a server-identifier option (option 54) in
   the first response to any DHCPBULKLEASEQUERY message.   The DHCPv4
   server SHOULD NOT send server identifier options in subsequent
   responses to that DHCPBULKLEASEQUERY message.   The requestor MUST
   cache the server-identifier option from the first response and apply
   it to any subsequent responses.

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   The response messages generated by a DHCPBULKLEASEQUERY request are:

      o DHCPLEASEACTIVE

        A Bulk Leasequery will generate DHCPLEASEACTIVE messages
        containing binding data for bound IP addresses which match the
        specified query criteria. The IP address which is bound to a
        DHCPv4 client will appear in the ciaddr field of the
        DHCPLEASEACTIVE message.  The message may contain a non-zero
        chaddr, htype, and hlen and possibly additional options.

      o DHCPLEASEUNASSIGNED

        Some queries will also generate DHCPLEASEUNASSIGNED messages for
        IP addresses which match the query criteria.  These messages
        indicate that the IP address is managed by the DHCPv4 server but
        is not currently bound to any DHCPv4 client.  The IP address to
        which this message refers will appear in the ciaddr field of the
        DHCPLEASEUNASSIGNED message.  A DHCPLEASEUNASSGINED message MAY
        also contain information about the last DHCPv4 client that was
        bound to this IP address. The message may contain a non-zero
        chaddr, htype, and hlen and possibly additional options in this
        case.

      o DHCPLEASEQUERYDONE

        A response of DHCPLEASEQUERYDONE indicates that the server has
        completed its response to the query, and that no more messages
        will be sent in response to the DHCPBULKLEASEQUERY. More details
        will sometimes be available in the received status-code option
        in the DHCPLEASEQUERYDONE message. If there is no status-code
        option in the DHCPLEASEQUERYDONE message, then the query
        completed successfully.

        Note that a query which returned no data, that is a
        DHCPBULKLEASEQUERY request followed by a DHCPLEASEQUERYDONE
        response, is considered a successful query in that no errors
        occurred during the processing.  It is not considered an error
        to have no information to return to a DHCPBULKLEASEQUERY
        request.

   The DHCPLEASEUNKNOWN message MUST NOT appear in a response to a Bulk
   Leasequery.

   The requestor MUST NOT assume that there is any inherent order in the
   IP address binding information that is sent in response to a
   DHCPBULKLEASEQUERY.  While the base-time will tend to increase
   monotonically (as it is the current time on the DHCPv4 server), the

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   actual time that any IP address binding information changed is
   unrelated to the base-time.

   The DHCPLEASEQUERYDONE message always ends a successful
   DHCPBULKLEASEQUERY request and any unsuccessful DHCPBULKLEASEQUERY
   requests not terminated by a dropped connection. After receiving
   DHCPLEASEQUERYDONE from a server, the requestor MAY close the TCP
   connection to that server if no other DHCPBULKLEASEQUERY is
   outstanding on that TCP connection.

   The DHCPv4 Leasequery protocol [RFC4388] uses the associated-ip
   option as an indicator that multiple bindings were present in
   response to a single DHCPv4 client based query.  For Bulk Leasequery,
   a separate message is returned for each binding, and so the
   associated-ip option is not used.

7.4.  Processing Time Values in Leasequery messages

   Bulk Leasequery requests may be made to a DHCPv4 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 Bulk Leasequery response, and in the situation where
   multiple DHCPv4 servers are queried, the situation becomes even more
   complex.

   If the requestor of a 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 DHCPv4 server.

   When receiving a DHCPLEASEACTIVE or DHCPLEASEUNASSIGNED message from
   the DHCPv4 server, the message will contain a base-time option.  The
   time contained in this base-time option is in the context of the
   DHCPv4 server.  As such, it is an ideal time to save and use as input
   to a DHCPBULKLEASEQUERY in the query-start-time or query-end-time
   options, should the requestor need to ever issue a DHCPBULKLEASEQUERY
   message using those options as part of a later query, since those
   options require a time in the context of the DHCPv4 server.

   In addition to saving the base-time for possible future use in a
   query-start-time or query-end-time option, the 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.

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7.5.  Querying Multiple Servers

   A Bulk Leasequery requestor MAY be configured to attempt to connect
   to and query from multiple DHCPv4 servers in parallel.  The DHCPv4
   Leasequery specification [RFC4388] includes a discussion about
   reconciling binding data received from multiple DHCPv4 servers.

   In addition, the algorithm in Section 7.6 should be used.

7.6.  Making Sense Out of Multiple Responses Concerning a Single IPv4
Address

   Any requestor of an Bulk Leasequery MUST be prepared for multiple
   responses to arrive for a particular IPv4 address from multiple
   different DHCPv4 servers. The following algorithm SHOULD be used to
   decide if the information just received is more up to date (i.e.,
   better) than the best existing information.  In the discussion below,
   the information that is received from a DHCPv4 server about a
   particular IPv4 address is termed a "record".  The times used in the
   algorithm below SHOULD have been converted into the requestor's
   context and the time comparisons SHOULD be performed in a manner
   consistent with the information in Section 7.4.

      o If both the existing and the new record contain client-last-
        transaction-time information, the record with the later client-
        last-transaction-time is considered better.

      o If one of the records contains client-last-transaction-time
        information and the other one doesn't, then compare the client-
        last-transaction-time in the record that contains it against the
        other record's start-time-of-state.  The record with the later
        time is considered better.

      o If neither record contains client-last-transaction-time
        information, compare their start-time-of-state information.  The
        record with the later start-time-of-state is considered better.

      o If none of the comparisons above yield a clear answer as to
        which record is later, then compare the value of the REMOTE flag
        from the data-source option for each record.

        If the values of the REMOTE flag are different between the two
        records, the record with the REMOTE flag value of local is
        considered better.

   The above algorithm does not necessarily determine which record is
   better.  In the event that the algorithm is inconclusive with regard
   to a record which was just received by the requestor, the requestor

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   SHOULD use additional information in the two records to make a
   determination as to which record is better.

7.7.  Multiple Queries to a Single Server over One Connection

   Bulk Leasequery requestors may need to make multiple queries in order
   to recover binding information.  A requestor MAY use a single
   connection to issue multiple queries to a server willing to support
   them. Each query MUST have a unique xid.

   A server SHOULD allow configuration of the number of queries that can
   be processed simultaneously over a single connection.  A server
   SHOULD read the number of queries it is configured to process
   simultaneously and only read any subsequent queries as current
   queries are processed.

   A server that is processing multiple queries simultaneously MUST
   interleave replies to the multiple queries within the stream of reply
   messages it sends.  Requestors need to be aware that replies for
   multiple queries may be interleaved within the stream of reply
   messages.  Requestors that are not able to process interleaved
   replies (based on xid) MUST NOT send more than one query over a
   single connection prior to the completion of the previous query.

   Requestors should be aware that servers are not required to process
   more than one query over a connection at a time (the limiting case
   for the configuration described above), and that servers are likely
   to limit the rate at which they process queries from any one
   requestor.

7.7.1.  Example

   This example illustrates what a series of queries and responses might
   look like.  This is only an example - there is no requirement that
   this sequence must be followed, or that requestors or servers must
   support parallel queries.

   In the example session, the client sends four queries after
   establishing a connection.  Query 1 returns no results; query 2
   returns 3 messages and the stream of replies concludes before the
   client issues any new query. Query 3 and query 4 overlap, and the
   server interleaves its replies to those two queries.

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      Requestor                                Server
      ---------                                ------
      DHCPBULKLEASEQUERY xid 1 ----->
                               <-----       DHCPLEASEQUERYDONE xid 1
      DHCPBULKLEASEQUERY xid 2 ----->
                               <-----       DHCPLEASEACTIVE xid 2
                               <-----       DHCPLEASEACTIVE xid 2
                               <-----       DHCPLEASEACTIVE xid 2
                               <-----       DHCPLEASEQUERYDONE xid 2
      DHCPBULKLEASEQUERY xid 3 ----->
      DHCPBULKLEASEQUERY xid 4 ----->
                               <-----       DHCPLEASEACTIVE xid 4
                               <-----       DHCPLEASEACTIVE xid 4
                               <-----       DHCPLEASEACTIVE xid 3
                               <-----       DHCPLEASEACTIVE xid 4
                               <-----       DHCPLEASEUNASSIGNED xid 3
                               <-----       DHCPLEASEACTIVE xid 4
                               <-----       DHCPLEASEACTIVE xid 3
                               <-----       DHCPLEASEQUERYDONE xid 3
                               <-----       DHCPLEASEACTIVE xid 4
                               <-----       DHCPLEASEQUERYDONE xid 4

7.8.  Closing Connections

   The requestor SHOULD close the connection after the
   DHCPLEASEQUERYDONE message is received for the last outstanding query
   that it has sent, if it has no more queries to send.

8.  Server Behavior

8.1.  Accepting Connections

   Servers that implement DHCPv4 Bulk Leasequery listen for incoming TCP
   connections.  Port numbers are discussed in Section 6.3.  Servers
   MUST be able to limit the number of concurrently accepted and active
   connections.  The value BULK_LQ_MAX_CONNS SHOULD be the default;
   implementations MAY permit the value to be configurable.  Connections
   SHOULD be accepted and, if the number of connections is over
   BULK_LQ_MAX_CONNS, they SHOULD be closed immediately.

   Servers MAY restrict Bulk Leasequery connections and
   DHCPBULKLEASEQUERY messages to certain requestors.  Connections not
   from permitted requestors SHOULD be closed immediately, to avoid
   server connection resource exhaustion.  Servers MAY restrict some
   requestors to certain query types.  Servers MAY reply to queries that

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   are not permitted with the DHCPLEASEQUERYDONE message with a status-
   code option status of NotAllowed, or MAY simply close the connection.

   If the TCP connection becomes blocked while the server is accepting a
   connection or reading a query, it SHOULD be prepared to terminate the
   connection after an BULK_LQ_DATA_TIMEOUT.  We make this
   recommendation to allow servers to control the period of time they
   are willing to wait before abandoning an inactive connection,
   independent of the TCP implementations they may be using.

8.2.  Replying to a Bulk Leasequery

   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 BULK_LQ_DATA_TIMEOUT.

   Every Bulk Leasequery request MUST be terminated by sending a final
   DHCPLEASEQUERYDONE message if such a message can be sent.  The
   DHCPLEASEQUERYDONE message MUST have a status-code option status if
   the termination was other than successful, and SHOULD NOT contain a
   status-code option status if the termination was successful.

   If the DHCPv4 server encounters an error during processing of the
   DHCPBULKLEASEQUERY message, either during initial processing or later
   during the message processing, it SHOULD send a DHCPLEASEQUERYDONE
   containing a status-code option.  It MAY close the connection after
   this error is signaled, but that is not required.

   If the server does not find any bindings satisfying a query, it MUST
   send a DHCPLEASEQUERYDONE.  It SHOULD NOT include a status-code
   option with a Success status unless there is a useful string to
   include in the status-code option.  Otherwise, the server sends each
   binding's data in a DHCPLEASEACTIVE or DHCPLEASEUNASSIGNED message.

   The response to a DHCPBULKLEASEQUERY may involve examination of
   multiple DHCPv4 IP address bindings maintained by the DHCPv4 server.
   The Bulk Leasequery protocol does not require any ordering of the IP
   addresses returned in DHCPLEASEACTIVE or DHCPLEASEUNASSIGNED
   messages.

   When responding to a DHCPBULKLEASEQUERY message, the DHCPv4 server
   MUST NOT send more than one message for each applicable IP address,
   even if the state of some of those IP addresses changes during the
   processing of the message.   Updates to such IP address state are
   already handled by normal protocol processing, so no special effort
   is needed here.

   If the ciaddr, yiaddr, or siaddr is non-zero in a DHCPBULKLEASEQUERY

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   request, the request must be terminated immediately by a
   DHCPLEASEQUERYDONE message with a status-code status of
   MalformedQuery.

   Any DHCPBULKLEASEQUERY which has more than one of the following
   primary query types specified MUST be terminated immediately by a
   DHCPLEASEQUERYDONE message with a status-code option status code of
   NotAllowed.

   The allowable queries in a DHCPBULKLEASEQUERY message are processed
   as follows.  Note that the descriptions of the primary queries below
   must be constrained by the actions of any of the three qualifiers
   described subsequently as well.

   The following table discusses how to process the various queries.
   For information on how to identify the query, see the information in
   Section 7.2.

      o Query by MAC address

        Every IP address that has a current binding to a DHCPv4 client
        matching the chaddr, htype, and hlen in the DHCPBULKLEASEQUERY
        request MUST be returned in a DHCPLEASEACTIVE message.

      o Query by Client-Id

        Every IP address that has a current binding to a DHCPv4 client
        matching the client-id option in the DHCPBULKLEASEQUERY request
        MUST be returned in a DHCPLEASEACTIVE message.

      o Query by Remote-Id

        Every IP address that has a current binding to a DHCPv4 client
        matching the remote-id sub-option of the relay-agent-information
        option in the DHCPBULKLEASEQUERY request MUST be returned in a
        DHCPLEASEACTIVE message.

      o Query by Relay-Id

        Every IP address that has a current binding to a DHCPv4 client
        matching the relay-id sub-option of the relay-agent-information
        option in the DHCPBULKLEASEQUERY request MUST be returned in a
        DHCPLEASEACTIVE message.

      o Query for All Configured IP Addresses

        A Query for All Configured IP addresses is signaled by the

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        absence of any other primary query.  That is, if there is no
        value in the chaddr, hlen, htype, no client-id option, no
        remote-id sub-option or relay-id sub-option of the relay-agent-
        information option, then the request is a query for information
        concerning all configured IP addresses. In this case, every
        configured IP address that has a current binding to a DHCPv4
        client MUST be returned in a DHCPLEASEACTIVE message.  In
        addition, every configured IP address that does not have a
        current binding to a DHCPv4 client MUST be returned in a
        DHCPLEASEUNASSIGNED message.

        In this form of query, each configured IP address MUST be
        returned at most one time.  If the absence of qualifiers
        restricting the number of IP addresses returned, every
        configured IP address MUST be returned exactly once.

   There are three qualifiers that can be applied to any of the above
   primary queries.  These qualifiers can appear individually or
   together in any combination, but only one of each can appear.

   o Query Start Time

     If a query-start-time option appears in the DHCPBULKLEASEQUERY
     request, only IP address bindings that have changed on or after the
     time specified in the query-start-time option should be returned.

   o Query End Time

     If a query-end-time option appears in the DHCPBULKLEASEQUERY
     request, only IP address bindings that have changed on or before
     the time specified in the query-end-time option should be returned.

   o VPN Id

     If no vpn-id option appears in the DHCPBULKLEASEQUERY, the default
     (global) VPN is used to satisfy the query.  A vpn-id option [VpnId]
     value other than the wildcard value (254) allows the requestor to
     specify a single VPN other than the default VPN.  In addition, the
     vpn-id option has been extended as part of this document to allow
     specification of a type 254 which indicates that all configured
     VPN's be searched in order to satisfy the primary query.

     In all cases, if the information returned in a DHCPLEASEACTIVE or
     DHCPLEASEUNASSIGNED message is for a VPN other than the default
     (global) VPN, a vpn-id option MUST appear in the packet.

   The query-start-time and query-end-time qualifiers are used to
   constrain the amount of data returned by a Bulk Leasequery request by

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   returning only IP addresses whose address bindings have changed in
   some way during the time window specified by the query-start-time and
   query-end-time.

   A DHCPv4 server SHOULD consider an address binding to have changed
   during a specified time window if either the client-last-
   transaction-time or the start-time-of-state of the address binding
   changed during that time window.

   The DHCPv4 server MAY return address binding data in any order, as
   long as binding information for any given IP address is not repeated.
   When all binding data for a given DHCPBULKLEASEQUERY has been sent,
   the DHCPv4 server MUST send a DHCPBULKLEASEQUERYDONE message.

8.3.  Building a Single Reply for Bulk Leasequery

   The DHCPv4 Leasequery [RFC4388] specification describes the initial
   construction of DHCPLEASEQUERY reply messages using the
   DHCPLEASEACTIVE and DHCPLEASEUNASSIGNED message types in Section
   6.4.2.  All of the reply messages in Bulk Leasequery are similar to
   the reply messages for an IP address query.  Message transmission and
   framing for TCP is described in this document in Section 6.1.

   [RFC2131] and [RFC4388] specify that every response message MUST
   contain the server-identifier option.  However, that option will be
   the same for every response from a particular DHCPBULKLEASEQUERY
   request.  Thus, the DHCPv4 server MUST include the server-identifier
   option in the first message sent in response to a DHCPBULKLEASEQUERY.
   It SHOULD NOT include the server-identifier in later messages.

   The message type of DHCPLEASEACTIVE or DHCPLEASEUNASSIGNED is based
   on the value of the dhcp-state option.  If the dhcp-state option
   value is ACTIVE, then the message type is DHCPLEASEACTIVE, otherwise
   the message type is DHCPLEASEUNASSIGNED.

   In addition to the basic message construction described in [RFC4388],
   the following guidelines exist:

      1. If the dhcp-state option code appears in the dhcp-parameter-
         request-list, the DHCPv4 server SHOULD include a dhcp-state
         option whose value corresponds most closely to the state held
         by the DHCPv4 server for the IP address associated with this
         reply.  If the state is ACTIVE and the message being returned
         is DHCPLEASEACTIVE, then the DHCPv4 server MAY choose to not
         send the dhcp-state option.  The requestor SHOULD assume that
         any DHCPLEASEACTIVE message arriving without a requested dhcp-
         state option has a dhcp-state of ACTIVE.

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      2. If the base-time option code appears in the dhcp-parameter-
         request-list, the DHCPv4 server MUST include a base-time
         option, which is the current time in the DHCPv4 server's
         context and the time from which the start-time-of-state, dhcp-
         lease-time, client-last-transaction-time, and other duration-
         style times are based upon.

      3. If the start-time-of-state option code appears in the dhcp-
         parameter-request-list, the DHCPv4 server MUST include a
         start-time-of-state option whose value represents the time at
         which the dhcp-state option's state became valid.

      4. If the dhcp-lease-time option code appears in the dhcp-
         parameter-request-list, the DHCPv4 server MUST include a dhcp-
         lease-time option for any state that has a time-out value
         associated with it.

      5. If the data-source option code appears in the dhcp-parameter-
         request-list, the DHCPv4 server MUST include the data-source
         option in any situation where any of the bits would be non-
         zero.  Thus, in the absence of the data-source option, the
         assumption is that all of the flags were zero.

      6. If the client-last-transaction-time option code appears in the
         dhcp-parameter-request-list, The DHCPv4 server MUST include the
         client-last-transaction-time option in any situation where the
         information is available.

      7. If there is a dhcp-parameter-request-list in the initial
         DHCPBULKLEASEQUERY request, then it should be used for all of
         the replies generated by that request.  Some options can be
         sent from a DHCPv4 client to the server or from the DHCPv4
         server to a DHCPv4 client. Option 125 is such an option.  If
         the option code for one of these options appears in the dhcp-
         parameter-request-list, it SHOULD result in returning the value
         of the option sent by the DHCPv4 client to the server if one
         exists.

   Note that there may be other requirements for a reply to a
   DHCPBULKLEASEQUERY request discussed in Section 8.2.

8.4.  Multiple or Parallel Queries

   As discussed in Section 7.3, requestors may want to use a connection
   that has already been established when they need to make additional
   queries. Servers SHOULD support reading and processing multiple
   queries from a single connection and SHOULD allow configuration of
   the number of simultaneous queries it may process. A server MUST NOT

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   read more query messages from a connection than it is prepared to
   process simultaneously.

   This SHOULD be a feature that is administratively controlled.
   Servers 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.

8.5.  Closing Connections

   The DHCPv4 server SHOULD start a timer for BULK_LQ_DATA_TIMEOUT
   seconds for a particular connection after it sends a
   DHCPLEASEQUERYDONE message over that connection and if there is no
   current query outstanding for that connection.  It should clear this
   timer if a query arrives over that connection.  If the timer expires,
   the DHCPv4 server should close the connection.

   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 status-code option in a DHCPLEASEQUERYDONE
   message, including a message string indicating details of the reason
   for the abort.   If the server detects that the requesting end of the
   connection has been closed, the server MUST close its end of the
   connection.

9.  Security Considerations

   The "Security Considerations" section of [RFC2131] details the
   general threats to DHCPv4.  The DHCPv4 Leasequery specification
   [RFC4388] describes recommendations for the Leasequery protocol,
   especially with regard to authentication of LEASEQUERY messages,
   mitigation of packet-flooding DOS attacks, and restriction to trusted
   requestors.

   The use of TCP introduces some additional concerns.  Attacks that
   attempt to exhaust the DHCPv4 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

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   in-process queries from any one connection, and that they limit the
   period of time during which an idle connection will be left open.

   [RFC4388] discusses security concerns and potential solutions for
   DHCPLEASEQUERY message exchanges in its Section 7, and all of the
   solutions discussed there are applicable to the DHCPLEASEQUERY
   message exchanges described in this document.

10.  IANA Considerations

   IANA is requested to assign the following new DHCPv4 option codes
   from the registry "BOOTP Vendor Extensions and DHCP Options"
   maintained at http://www.iana.org/assignments/bootp-dhcp-parameters

      1. An option code of TBD1 for status-code.

      2. An option code of TBD2 for base-time.

      3. An option code of TBD3 for start-time-of-state.

      4. An option code of TBD4 for query-start-time.

      5. An option code of TBD5 for query-end-time.

      6. An option code of TBD6 for dhcp-state.

      7. An option code of TBD7 for data-source.

   IANA is requested to assign the following new DHCP message types from
   the registry "DHCP Message Type 53 Values" maintained at
   http://www.iana.org/assignments/bootp-dhcp-parameters

      1. A dhcp-message-type of TBD8 for DHCPBULKLEASEQUERY.

      2. A dhcp-message-type of TBD9 for DHCPLEASEQUERYDONE.

   IANA is requested to create a new registry on the same assignments
   page, titled "DHCP State TBD6 Values" (where TBD6 corresponds to the
   assigned value of the dhcp-state option, above).  This registry will
   have the following initial values:

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     State
     -----
       1     AVAILABLE
       2     ACTIVE
       3     EXPIRED
       4     RELEASED
       5     ABANDONED
       6     RESET
       7     REMOTE
       8     TRANSITIONING

   New values for this name space may only be defined by IETF Consensus,
   as described in [RFC5226]. Basically, this means that they are
   defined by RFCs approved by the IESG.

   IANA is requested to create a new registry on the same assignments
   page, titled "DHCP Status Code TBD1 Values" (where TBD1 corresponds
   to the assigned value of the status-code option, above).  This
   registry will have the following initial values:

     Name    status-code
     ----    -----------
     Success         000
     UnspecFail      001
     QueryTerminated 002
     MalformedQuery  003
     NotAllowed      004

   New values for this name space may only be defined by IETF Consensus,
   as described in [RFC5226]. Basically, this means that they are
   defined by RFCs approved by the IESG.

   IANA is requested to revise the registry that will be created on the
   same assignments page when the [VpnId] option is approved.  The
   registry will be "Virtual Subnet Selection Type and Information".  It
   should be revised to appear as follows:

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          Type     VSS Information format:

           0       UTF-8 ASCII VPN identifier
           1       RFC2685 VPN-ID
           2-253   Not Allowed
           254     All VPN's.  (wildcard; only allowed in
                   DHCPBULKLEASEQUERY messages)
           255     Global, default VPN.

11.  Acknowledgements

   This draft is a collaboration between the authors of draft-dtv-dhc-
   dhcpv4-bulk-leasequery-00.txt and draft-kkinnear-dhc-dhcpv4-bulk-
   leasequery-00.txt.  Both documents acknowledged that significant text
   as well as important ideas were borrowed in whole or in part from the
   DHCPv6 Bulk Leasequery RFC, [RFC5460] written by Mark Stapp. Further
   suggestions and improvements were made by participants in the DHC
   working group, including Alfred Hoenes.

12.  References

12.1.  Normative References

   [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
      Requirement Levels", RFC 2119, March 1997.

   [RFC2131] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131,
      March 1997.

   [RFC2132] Alexander, S., Droms, R., "DHCP Options and BOOTP Vendor
      Extensions", RFC 2132, March 1997.

   [RFC3046] Patrick, M., "DHCP Relay Agent Information Option", RFC
      3046, January 2001.

   [RFC4388] Woundy, R., K. Kinnear, "Dynamic Host Configuration
      Protocol (DHCP) Leasequery", RFC 4388, February 2006.

   [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
      IANA Considerations Section in RFCs", BCP 26, RFC 5226, May 2008.

   [RelayId] Stapp, M., "The DHCPv4 Relay Agent Identifier Suboption",
      draft-ietf-dhc-relay-id-suboption-09.txt, (work in progress) June

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      2011.

   [VpnId] Kinnear, K., R. Johnson, M. Stapp and J. Kumarasamy, "Virtual
      Subnet Selection Options for DHCPv4 and DHCPv6" draft-ietf-dhc-
      vpn-option-14.txt, (work in progress) November 2011.

12.2.  Informative References

   [RFC951] Croft, B., Gilmore, J., "Bootstrap Protocol (BOOTP)", RFC
      951, September 1985.

   [RFC1542] Wimer, W., "Clarifications and Extensions for the Bootstrap
      Protocol", RFC 1542, October 1993.

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

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

Authors' Addresses

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

      Phone: (978) 936-0000

      EMail: kkinnear@cisco.com

      Bernie Volz
      Cisco Systems
      1414 Massachusetts Ave.
      Boxborough, Massachusetts 01719

      Phone: (978) 936-0000

      EMail: volz@cisco.com

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      Neil Russell
      Nokia
      5 Wayside Drive
      Burlington, MA 01803

      EMail: neil.russell@nokia.com

      Mark Stapp
      Cisco Systems
      1414 Massachusetts Ave.
      Boxborough, Massachusetts 01719

      Phone: (978) 936-0000

      EMail: mjs@cisco.com

      Ramakrishna Rao DTV
      Infosys Technologies Ltd.
      44 Electronics City, Hosur Road
      Bangalore  560 100
      India

      EMail: ramakrishnadtv@infosys.com
      URI:   http://www.infosys.com/

      Bharat Joshi
      Infosys Technologies Ltd.
      44 Electronics City, Hosur Road
      Bangalore  560 100
      India

      EMail: bharat_joshi@infosys.com
      URI:   http://www.infosys.com/

      Pavan Kurapati
      Juniper Networks Ltd.
      Embassy Prime Buildings, C.V.Raman Nagar
      Bangalore  560 093
      India

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      Email: kurapati@juniper.net
      URI:   http://www.juniper.net/

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