Internet DRAFT - draft-ietf-dhc-dhcpv4-bulk-leasequery
draft-ietf-dhc-dhcpv4-bulk-leasequery
DHC Working Group Kim Kinnear
Internet Draft Mark Stapp
Intended Status: Standards Track Cisco Systems, Inc.
Expires: April 15, 2013 D. Rao
B. Joshi
Infosys Technologies Ltd.
Neil Russell
BMC Software, Inc.
October 15, 2012
Bulk DHCPv4 Lease Query
<draft-ietf-dhc-dhcpv4-bulk-leasequery-07.txt>
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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'................................ 8
3.4. Minimize data transmission................................. 8
4. Protocol Overview............................................ 8
5. Interaction Between UDP Leasequery and Bulk Leasequery....... 10
6. Message and Option Definitions............................... 11
6.1. Message Framing for TCP.................................... 11
6.2. New or Changed Options..................................... 12
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
8. Server Behavior.............................................. 28
8.1. Accepting Connections...................................... 28
8.2. Replying to a Bulk Leasequery.............................. 28
8.3. Building a Single Reply for Bulk Leasequery................ 31
8.4. Multiple or Parallel Queries............................... 33
8.5. Closing Connections........................................ 33
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9. Security Considerations...................................... 34
10. IANA Considerations......................................... 35
11. Contributing Authors........................................ 37
12. Acknowledgements............................................ 38
13. References.................................................. 38
13.1. Normative References...................................... 38
13.2. Informative References.................................... 39
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 |-...-| DHCP |
| | | 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.
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 rapidly recover lease state information
about a particular IP address or client.
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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
environment.
o "active binding"
An IP address with an active binding refers to an IP address
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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 Special Use
IPv4 Addresses as defined in [RFC1918].
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 an agent that is neither a DHCPv4 client
nor a DHCP server that transfers BOOTP and DHCPv4 messages
between clients and servers residing on different subnets, per
[RFC951] and [RFC1542].
o "DHCPv4 server"
A DHCPv4 server is an Internet node that returns configuration
parameters to DHCPv4 clients.
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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 and
toward the DHCPv4 client..
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 away from the DHCPv4 client toward
the DHCPv4 server.
o "stable storage"
Stable storage is used to hold information concerning IP address
bindings (among other things) so that this information is not
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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 (such as a DHCP Relay
Agent) to retrieve IP address binding information available in the
DHCPv4 server. The mechanism should also allow an Access
Concentrator or DHCP Relay Agent to retrieve consolidated IP address
binding information for either the entire access concentrator or a
single connection/circuit. Throughout the discussion below,
everything that applies to an Access Concentrator also applies to a
DHCP Relay Agent.
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
messages 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 messages. 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. One
of the goals of the DHCPv4 Bulk Leasequery is to reduce the need for
this sort of caching.
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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 messages 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 [RFC6607] 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.
The Bulk Leasequery TCP connection is only designed to handle the
DHCPBULKLEASEQUERY request. It is not intended as an alternative
DHCPv4 communication option for clients seeking other DHCPv4
services. DHCPv4 address allocation could not be performed over a
TCP connection in any case, as a TCP connection requires an IP
address, as no IPv4 address exists prior to a successful DHCPv4
address allocation exchange. In addition, the existing DHCPv4 UDP
transmission regime is implemented in untold millions of devices
deployed worldwide, and complicating DHCPv4 services with alternative
transmission approaces (even if it were possible) would be worse than
any perceived benefit to doing so.
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.
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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
[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 unsigned 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.
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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].
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 |
+------+------+------+------+------+-- --+-----+
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The status-code is indicated in one octet as defined in the table
below. The Status Message is an optional UTF-8 encoded text string
suitable for display to an end user. This text string MUST NOT
contain a termination character (e.g., a null). The len field
describes the length of the status message without any terminator
character. Nulls characters MUST NOT appear in the Status Message
string and it is a protocol violation for them to appear in any
position in the Status Message, including at the end.
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 unsigned integer in network byte order.
The code for this option is TBD2. The length of this option is 4
octets.
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DHCPv4 Server
Code Len base-time
+-----+-----+-----+-----+-----+-----+
| TBD2| 4 | t1 | t2 | t3 | t4 |
+-----+-----+-----+-----+-----+-----+
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 unsigned 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 unsigned 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.
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This MUST be an absolute time.
This is an unsigned integer in network byte order.
The code for this option is TBD4. The length of this option is 4
octets.
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 unsigned 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. While a
state transition diagram can be drawn, it would be fully connected
and therefore conveys no useful information. 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
SHOULD be 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. When one server
is working with another server and both may respond with information
about the same IP address, each server SHOULD return the data-source
option with the other information provided about the 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
+-+-+-+-+-+-+-+-+
| UNA |R|
+-+-+-+-+-+-+-+-+
R: REMOTE flag
remote = 1
local = 0
UNA: UNASSIGNED
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.
Unassigned bits MUST be ignored.
6.2.9. Virtual Subnet Selection Type and Information
All of the (sub)options defined in [RFC6607] 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 Network Virtual Terminal (NVT) ASCII VPN identifier
1 RFC 2685 VPN-ID
CHANGED -> 2-253 Unassigned
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 [RFC6607] 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. Note that the times specified
in the query-start-time or query-end-time options are absolute times,
not durations offset from "now".
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. This timer
is completely independent of any TCP timeout established by the TCP
protocol 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.
If the requestor receives more data than it can process, it can
simply abort the connection and try again with a more specific
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request. It can also simply read the TCP connection more slowly, and
match the rate at which it can digest the information returned in the
Bulk Leasequery packets with the rate at which it reads those packets
from 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.
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
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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
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
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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.
These other time values are specified as a offset (duration) from the
base-time value and not as an absolute time.
In systems whose clocks are synchronized, perhaps using NTP, the
clock skew will usually be zero.
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
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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
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 NOT
block sending replies on new queries until all replies for the
existing query are complete. 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
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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.
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
If a requestor as no additional queries to send, or doesn't know if
it has additional queries to send or not, then it SHOULD close the
connection after receiving the DHCPLEASEQUERYDONE message for the
last outstanding query that it has sent.
The requestor SHOULD close connections in a graceful manner and not
an abort. The requestor SHOULD NOT assume that the manner in which
the DHCP server closed a connection carries any special meaning.
Typically, the requestor is the entity which will close the
connection, as servers will often wait with an open connection in
case the requestor has additional queries.
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If a server closes a connection with an exception condition, the
requestor SHOULD consider as valid any completely received
intermediate results, and the requestor MAY retry the Bulk Leasequery
operation.
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
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
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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
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.
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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
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.
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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
[RFC6607] 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
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
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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.
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
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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
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 close connections in a graceful manner and
not abort the connection. The DHCPv4 server SHOULD NOT assume that
the manner in which the requestor closed a connection carries any
special meaning.
Typically, the DHCPv4 server will only close the connection after
some form of an exception or a timeout on the connection.
Using a timer to detect when a connection is idle, and then closing
that connection is designed to protect the DHCPv4 server from
consuming unnecessary resources.
The DHCPv4 server should start a timer for BULK_LQ_DATA_TIMEOUT
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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 restart
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 connection is closed for any reason, all of
the data flows associated with any currently outstanding
DHCPBULKLEASEQUERY messages will be terminated.
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
in-process queries from any one connection, and that they limit the
period of time during which an idle connection will be left open.
There are two specific issues regarding Bulk Leasequery security that
deserve explicit mention. The first is preventing information that
Bulk Leasequery can provide from reaching clients who are not
authorized to receive such information. The second is ensuring that
authorized clients of the Bulk Leasequery capability receive accurate
information from the Server (and that this information is not
disrupted in transit).
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To prevent information leakage to unauthorized clients Servers SHOULD
restrict Bulk Leasequery connections and DHCPBULKLEASEQUERY messages
to certain requestors, either through explicit configuration of the
Server itself or by employing external network elements to provide
such restrictions. In particular, the typical DHCPv4 client SHOULD
NOT be allowed to receive a response to a Bulk Leasequery request,
and some technique MUST exist to allow prevention of such access in
any environment where Bulk Leasequery is deployed.
Connections not from permitted requestors SHOULD be closed
immediately, to avoid server connection resource exhaustion or
alternatively, simply not be allowed to reach the server at all.
Servers SHOULD have the capability to restrict certain requestors to
certain query types. Servers MAY reply to queries that are not
permitted with the DHCPLEASEQUERYDONE message with a status-code
option status of NotAllowed, or MAY simply close the connection.
To prevent disruption and malicious corruption of Bulk Leasequery
data flows between the server and authorized clients these data flows
SHOULD transit only secured networks. These data flows are
typically infrastructure oriented, and there is usually no reason to
have them flowing over networks where such attacks are likely. In
the rare cases where these data flows might need to be sent through
unsecured networks, they MUST sent over connections secured through
means external to the DHCPv4/DHCPv6 server and its client(s) (e.g.,
through VPN's).
Authentication for DHCP Messages [RFC3118] MUST NOT be used to
attempt to secure transmission of the messages described in this
document. In particular, the message framing would not be protected
by using the mechanisms described in [RFC3118] (which was designed
only with UDP transport in mind).
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.
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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:
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 Review, as
described in [RFC5226].
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
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New values for this name space may only be defined by IETF Review, as
described in [RFC5226].
IANA is requested to revise the registry "VSS Type Options" created
by [RFC6607] in the overall area "Dynamic Host Configuration Protocol
(DHCP) and Bootstrap Protocol (BOOTP) Parameters". It should be
revised to appear as follows. Note that the number range for
"Unassigned" has changed as well as the new line for "All VPN's
(wildcard)" which was added.
Type VSS Information Format
------------------------------------------------------------
0 Network Virtual Terminal (NVT) ASCII VPN identifier
1 RFC 2685 VPN-ID
2-253 Unassigned
254 All VPN's (wildcard)
255 Global, default VPN
11. Contributing Authors
The following authors were full participants in creating this
document. In order to facilitate the process of approval for this
work, they graciously volunteered to have their names appear in this
section instead of on the title page.
Pavan Kurapati
Juniper Networks Ltd.
Embassy Prime Buildings, C.V.Raman Nagar
Bangalore 560 093
India
Email: kurapati@juniper.net
URI: http://www.juniper.net/
Bernie Volz
Cisco Systems
1414 Massachusetts Ave.
Boxborough, Massachusetts 01719
Phone: (978) 936-0000
EMail: volz@cisco.com
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12. 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.
13. References
13.1. Normative References
[RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and
E. Lear, "Address Allocation for Private Internets", RFC 1918,
February 1996.
[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. and R. Droms, "DHCP Options and BOOTP Vendor
Extensions", RFC 2132, March 1997.
[RFC3046] Patrick, M., "DHCP Relay Agent Information Option", RFC
3046, January 2001.
[RFC3118] Droms, R. "Authentication for DHCP Messages", RFC 3118,
June 2001.
[RFC4388] Woundy, R. and 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] Joshi, B., Rao, D., and M. Stapp, "The DHCPv4 Relay Agent
Identifier Suboption", draft-ietf-dhc-relay-id-suboption-11.txt,
(work in progress) July 2012.
[RFC6607] Kinnear, K., Johnson, R., and M. Stapp, "Virtual Subnet
Selection Options for DHCPv4 and DHCPv6", RFC 6607, April 2012.
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13.2. Informative References
[RFC951] Croft, B. and J. Gilmore, "Bootstrap Protocol (BOOTP)", RFC
951, September 1985.
[RFC1542] Wimer, W., "Clarifications and Extensions for the Bootstrap
Protocol", RFC 1542, October 1993.
[RFC4614] Duke, M., Braden, R., Eddy, W., 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
Neil Russell
BMC Software
10 Maguire Rd., Bldg. 3, Ste. 320
Lexington, MA 02421
Phone: (781) 257-3105
EMail: neil_russell@bmc.com
Mark Stapp
Cisco Systems
1414 Massachusetts Ave.
Boxborough, Massachusetts 01719
Phone: (978) 936-0000
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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/
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