Internet DRAFT - draft-ietf-dhc-dhcvp6-leasequery
draft-ietf-dhc-dhcvp6-leasequery
DHC J. Brzozowski
Internet-Draft Comcast Cable
Intended status: Standards Track K. Kinnear
Expires: June 21, 2007 B. Volz
S. Zeng
Cisco Systems, Inc.
December 18, 2006
DHCPv6 Leasequery
<draft-ietf-dhc-dhcvp6-leasequery-01.txt>
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Copyright Notice
Copyright (C) The Internet Society (2006).
Abstract
This document specifies leasequery for the Dynamic Host Configuration
Protocol for IPv6 (DHCPv6) which can be used as a means to obtain
lease information about DHCPv6 clients from a DHCPv6 server. This
document specifies the scope of data that can be retrieved as well as
both DHCPv6 leasequery requestor and server behavior. This document
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extends DHCPv6.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 4
3.1. On-Demand Query . . . . . . . . . . . . . . . . . . . . . 4
3.2. Anticipatory Query . . . . . . . . . . . . . . . . . . . . 4
3.3. Query Types . . . . . . . . . . . . . . . . . . . . . . . 5
4. Protocol Details . . . . . . . . . . . . . . . . . . . . . . . 5
4.1. Message and Option Definitions . . . . . . . . . . . . . . 5
4.1.1. Messages . . . . . . . . . . . . . . . . . . . . . . . 5
4.1.2. Options . . . . . . . . . . . . . . . . . . . . . . . 5
4.1.3. Status Codes . . . . . . . . . . . . . . . . . . . . . 10
4.1.4. Transmission and Retransmission Parameters . . . . . . 11
4.2. Message Validation . . . . . . . . . . . . . . . . . . . . 11
4.2.1. LEASEQUERY . . . . . . . . . . . . . . . . . . . . . . 11
4.2.2. LEASEQUERY-REPLY . . . . . . . . . . . . . . . . . . . 11
4.3. DHCPv6 Leasequery Requestor Behavior . . . . . . . . . . . 12
4.3.1. Creation of LEASEQUERY . . . . . . . . . . . . . . . . 12
4.3.2. Transmission of LEASEQUERY . . . . . . . . . . . . . . 12
4.3.3. Receipt of LEASEQUERY-REPLY . . . . . . . . . . . . . 13
4.3.4. Handling DHCPv6 Client Data from Multiple Sources . . 13
4.4. DHCPv6 Leasequery Server Behavior . . . . . . . . . . . . 14
4.4.1. Receipt of LEASEQUERY Messages . . . . . . . . . . . . 14
4.4.2. Constructing the Client's OPTION_CLIENT_DATA . . . . . 15
4.4.3. Transmission of LEASEQUERY-REPLY Messages . . . . . . 16
5. Security Considerations . . . . . . . . . . . . . . . . . . . 16
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 18
8. Modification History . . . . . . . . . . . . . . . . . . . . . 18
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 19
9.1. Normative References . . . . . . . . . . . . . . . . . . . 19
9.2. Informative References . . . . . . . . . . . . . . . . . . 19
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 19
Intellectual Property and Copyright Statements . . . . . . . . . . 21
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1. Introduction
The DHCPv6 [2] protocol specifies a mechanism for the assignment of
both IPv6 address and configuration information to IPv6 nodes. IPv6
Prefix Options for DHCPv6 [4] specifies a mechanism for the automated
delegation of IPv6 prefixes and related options. Similar to DHCPv4
[6], DHCPv6 servers maintain authoritative information related to its
operations including but not limited to lease information for IPv6
addresses and delegated prefixes.
The requirement exists in various types of IPv6 deployments,
particularly those of a broadband variety, to leverage DHCPv6 [2] for
retrieving data related to the operation of DHCPv6 servers
programmatically. In particular it is desirable to be able to
extract lease information about IPv6 addresses and delegated prefixes
assigned using DHCPv6 [2] [4]. Specific examples where this
information has illustrated value are in broadband networks to
facilitate access control by edge devices. This capability to
programitcally extract lease data from the DHCPv6 server is called
leasequery.
Existing specifications, such as [3] are leveraged as a basis for
extending the DHCPv6 protocol to support leasequery. The motivations
and justifications identified in [3] also generally apply to this
specification. Furthermore, advancements in DHCPv6 [2] are expanded
upon to specify additional means by which IPv6 address and delegated
prefix lease data can be retrieved through DHCPv6 leasequery.
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [1].
DHCPv6 terminology is defined in [2]. Terminology specific to DHCPv6
leasequery can be found below:
client(s) The nodes that have one or more bindings
with a DHCPv6 server. This does not refer to
the node issuing the LEASEQUERY unless it
itself has one or more bindings with a DHCPv6
server.
requestor The node that sends LEASEQUERY messages to one
or more servers to retrieve information on the
bindings for a client.
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3. Protocol Overview
The focus of this document is to extend the DHCPv6 protocol to allow
processes and devices that wish to access information from a DHCPv6
server to do so in a lightweight and convenient manner. It is
especially appropriate for processes and devices that already
interpret DHCPv6 messages.
The LEASEQUERY message is a query message only and does not affect
the state of the IPv6 address or prefix, or the binding information
associated with it.
One important motivating example is that the LEASEQUERY message
allows access concentrators to query DHCP servers to obtain location
information of broadband access network devices.
The leasequery capability described in this document parallels the
DHCPv4 leasequery capability documented in [3]. As such, it shares
many of the basic motivations, design goals and constraints as the
capability described in Section 4 of [3].
3.1. On-Demand Query
The on-demand leasequery capability allows requesting just the
information necessary to satisfy an immediate need. If the requestor
is an access concentrator, then the immediate need will typically be
that it has received an IPv6 packet and it needs to refresh its
information concerning the DHCPv6 client to which that an IPv6
address is currently leased. In this case, the request will be by
Address. This fits clearly into the single request/response cycle
common to other DHCPv6 message exchanges.
However, this approach has limitations when used with prefix
delegation [4] as no traffic may arrive because the access
concentrator is unable to inject the appropriate routing information
into the routing infrastructure, such as after a reboot. This
approach does work if the access concentrator is configured to inject
routing information for a prefix which aggregates potentially
delegated prefixes. Or, if the access concentrator and requesting
router use a routing protocol; as then the requesting router can
trigger the access concentrator to request information from a DHCPv6
server and inject appropriate routing information into the routing
infrastructure.
3.2. Anticipatory Query
A second approach for requesting information from a DHCPv6 server
would be to use a leasequery-like capability to rebuild an internal
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data store containing information available from a DHCPv6 server.
The rebuilding of the data store in this approach can take place as
soon as possible after the need to rebuild it is discovered (such as
on booting), and doesn't wait on the receipt of specific packets to
trigger a piecemeal database update (as is the case for on-demand
leasequery). This approach would also remove the limitation
discussed above for prefix delegation.
This anticipatory query is not specified in this document and is an
area of future work.
3.3. Query Types
Leasquery provides for the following queries:
Query by IPv6 address - This query allows a requestor to request
from a server the bindings for a client that either is bound to
the address or has been delegated the prefix that contains the
address.
Query by Client Identifier (DUID) - This query allows a requestor to
request from a server the bindings for a specific client on a
specific link or a list of the links on which the client has one
or more bindings.
4. Protocol Details
4.1. Message and Option Definitions
4.1.1. Messages
The LEASEQUERY and LEASEQUERY-REPLY messages use the Client/Server
message formats described in [2], section 6. Two new message codes
are defined:
LEASEQUERY (TBD) - A requestor sends a LEASEQUERY message to any
available server to obtain information on a client's or clients'
leases. The options in an OPTION_LQ_QUERY determine the query.
LEASEQUERY-REPLY (TBD) - A server sends a LEASEQUERY-REPLY message
containing client data in response to a LEASEQUERY message.
4.1.2. Options
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4.1.2.1. Query Option
The Leasequery Query option is used only in a LEASEQUERY message and
identifies the query being performed. The option includes the query
type, link-address (or 0::0), and option(s) to provide data needed
for the query.
The format of the Query option is shown below:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_LQ_QUERY | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| query-type | |
+-+-+-+-+-+-+-+-+ |
| |
| link-address |
| |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | .
+-+-+-+-+-+-+-+-+ .
. query-options .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
option-code OPTION_LQ_QUERY (TBD)
option-len 17 + length of query-options field.
link-address A global address that will be used by the
server to identify the link to which the
query applies, or 0::0 if unspecified.
query-type the query requested (see below).
query-options the options related to the query.
The query-type and required query-options are:
QUERY_BY_ADDRESS (1) - The query-options MUST contain an
OPTION_IAADDR option [2]. The link-address field, if not 0::0,
specifies an address for the link on which the client is located
if the address in the OPTION_IAADDR option is of insufficient
scope. Only the information for the client that has a lease for
the specified address or was delegated a prefix that contains the
specified address is returned (if available).
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QUERY_BY_CLIENTID (2) - The query-options MUST contain an
OPTION_CLIENTID option [2]. The link-address field, if not 0::0,
specifies an address for the link on which the client is located.
If the link-address field is 0::0, the server SHOULD search all of
its links of the client.
The query-options MAY also include an OPTION_ORO option [2] to
indicate the options for each client that the requestor would like
the server to return. Note that this OPTION_ORO is distinct and
separate from an OPTION_ORO that may be in the requestor's LEASEQUERY
message.
If a server receives an OPTION_LQ_QUERY with a query-type it does not
support, the server SHOULD return an UnknownQueryType status-code.
If a server receives a supported query-type but the query-options is
missing a required option, the server SHOULD return a MalformedQuery
status-code.
4.1.2.2. Client Data Option
The Client Data option is used to encapsulate the data for a single
client on a single link in a LEASEQUERY-REPLY message.
The format of the Client Data option is shown below:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_CLIENT_DATA | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. client-options .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
option-code OPTION_CLIENT_DATA (TBD)
option-len length, in octets, of the encapsulated client-
options field.
client-options the options associated with this client.
The encapsulated client-options include the OPTION_CLIENTID,
OPTION_IAADDR, OPTION_IAPREFIX, and OPTION_CLT_TIME options and other
options specific to the client and requested by the requestor in the
OPTION_ORO in the OPTION_LQ_QUERY's query-options. The server MUST
return all of the client's statefully assigned addresses and
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delegated prefixes, with a non-zero valid lifetime, on the link.
4.1.2.3. Client Last Transaction Time Option
The Client Last Transaction Time option is encapsulated in an
OPTION_CLIENT_DATA and identifies how long ago the server last
communicated with the client, in seconds.
The format of the Client Last Transaction Time option is shown below:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_CLT_TIME | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| client-last-transaction-time |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
option-code OPTION_CLT_TIME (TBD)
option-len 4
client-last-transaction-time
the number of seconds since the server last
communicated with the client (on that link).
The client-last-transaction-time is a positive value and reflects the
number of seconds since the server last communicated with the client
(on that link).
4.1.2.4. Relay Data
The Relay Data option is used only in a LEASEQUERY-REPLY message and
provides the relay agent information used when the client last
communicated with the server.
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The format of the Client Links option is shown below:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_LQ_RELAY_DATA | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| peer-address (IPv6 address) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| DHCP-relay-message |
. .
. .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
option-code OPTION_LQ_RELAY_DATA (TBD)
option-len 16 + length of DHCP-relay-message.
peer-address The address of the relay agent from which
the relayed message was received by the
server.
DHCP-relay-message
The last complete relayed message excluding
the client's message OPTION_RELAY_MSG
received by the server.
This option is used by the server to return full relay agent
information for a client. It MUST NOT be returned if the server does
not have such information, either because the client last
communicated directly (without relay agent) with the server or if the
server does not retained such information.
If returned, the DHCP-relay-message MUST contain a valid (perhaps
multi-hop) RELAY-FORW message as most recently received by the server
for the client. However, the (inner most) OPTION_RELAY_MSG option
containing the client's message MUST have been removed.
This option SHOULD only be returned if requested by the OPTION_ORO of
the OPTION_LQ_QUERY.
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4.1.2.5. Client Link Option
The Client Link option is used only in a LEASEQUERY-REPLY message and
identifies the links on which the client has one or more bindings.
It is used in reply to a query when no link-address was specified and
the client is found to be on more than one link.
The format of the Client Link option is shown below:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_LQ_CLIENT_LINK | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| link-address (IPv6 address) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| link-address (IPv6 address) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
option-code OPTION_LQ_CLIENT_LINKS (TBD)
option-len Length of the list of links in octets;
must be a multiple of 16.
link-address A global address used by the server to
identify the link on which the client is
located.
A server may respond to a query by client-id, where the 0::0 link-
address was specified, with this option if the client is found to be
on multiple links. The requestor may then repeat the query once for
each link-address returned in the list, specifying the returned link-
address. If the client is on a single link, the server SHOULD return
the client's data in an OPTION_CLIENT_DATA option.
4.1.3. Status Codes
The following new status codes are defined:
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UnknownQueryType (TBD) - The query-type is unknown to or not
supported by the server.
MalformedQuery (TBD) - The query is not valid, for example a
required query-option is missing from the OPTION_LQ_QUERY.
NotConfigured (TBD) - The server does not have the target address or
link in its configuration.
NotAllowed (TBD) - The server does not allow the requestor to issue
this LEASEQUERY.
4.1.4. Transmission and Retransmission Parameters
This section presents a table of values used to describe the message
transmission behavior for leasequery.
Parameter Default Description
----------------------------------
LQ_TIMEOUT 1 sec Initial LEASEQUERY timeout
LQ_MAX_RT 10 secs Max LEASEQUERY timeout value
LQ_MAX_RC 5 Max LEASEQUERY retry attempts
4.2. Message Validation
4.2.1. LEASEQUERY
Requestors and clients MUST discard any received LEASEQUERY messages.
Servers MUST discard any received LEASEQUERY messages that meet any
of the following conditions:
o the message does not include an OPTION_CLIENTID option.
o the message includes an OPTION_SERVERID option but the contents of
the OPTION_SERVERID option does not match the server's identifier.
o the message does not include an OPTION_LQ_QUERY option.
4.2.2. LEASEQUERY-REPLY
Requestors MUST discard any received LEASEQUERY-REPLY messages that
meet any of the following conditions:
o the message does not include an OPTION_SERVERID option.
o the message does not include an OPTION_CLIENTID option or the
contents of the OPTION_CLIENTID option do not match the DUID of
the requestor.
o the "transaction-id" field in the message does not match the value
used in the original message.
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Servers and Relay Agents (on the server port, 547 [2]) MUST discard
any received LEASEQUERY-REPLY messages.
4.3. DHCPv6 Leasequery Requestor Behavior
This section describes how a requestor initiates lease data retrieval
from DHCPv6 servers.
4.3.1. Creation of LEASEQUERY
The requestor sets the "msg-type" field to LEASEQUERY. The requestor
generates a transaction ID and inserts this value in the
"transaction-id" field.
The requestor MUST include an OPTION_CLIENTID option to identify
itself to the server.
The requestor MUST include an OPTION_LQ_QUERY option and set the
query-type, link-address, and query-options as appropriate to the
query-type (Section 4.1.2.1).
The requestor SHOULD include an OPTION_SERVERID if it is not
unicasting the LEASEQUERY yet only wants a response from a specific
server.
4.3.2. Transmission of LEASEQUERY
The requestor MAY be configured to use a list of destination
addresses, which MAY include unicast addresses, the All_DHCP_Servers
multicast address, or other addresses selected by the network
administrator. If the requestor has not been explicitly configured,
it MAY use the All_DHCP_Servers multicast address as the default.
The requestor SHOULD send LEASEQUERY to one or more DHCPv6 servers
which are known to possess authoritative information concerning the
query target.
In the absence of information concerning which DHCPv6 servers might
possess authoritative information on the query target, the requestor
SHOULD send LEASEQUERY to all DHCPv6 servers that the requestor knows
about or is configured with. For example, the requestor MAY send
LEASEQUERY to the All_DHCP_Servers multicast address.
The requestor transmits LEASEQUERY messages according to section 14
of [2], using the following parameters:
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IRT LQ_TIMEOUT
MRT LQ_MAX_RT
MRC LQ_MAX_RC
MRD 0
If the message exchange fails, the requestor takes an action based on
the requestor's local policy. Examples of actions the requestor
might take include:
o Select another server from a list of servers known to the
requestor.
o Send to multiple servers by multicasting to the All_DHCP_Servers
address.
o Terminate the leasequery.
4.3.3. Receipt of LEASEQUERY-REPLY
A successful LEASEQUERY-REPLY is one without an OPTION_STATUS_CODE
option (or an OPTION_STATUS_CODE option with a success code). There
are three varients:
1. If the server has bindings for the requested client, the message
includes an OPTION_CLIENT_DATA option and the requestor extracts
the client data for the LEASEQUERY-REPLY and updates its binding
information database. If the OPTION_CLIENT_DATA contains no
OPTION_CLT_TIME, the requestor SHOULD silently discard the
OPTION_CLIENT_DATA option. The LEASEQUERY-REPLY SHOULD contain
an OPTION_SERVER_RSN option [5] and the requestor SHOULD only
update its binding information database as described in [5].
2. If the server found bindings for the client on multiple links,
the message includes an OPTION_CLIENT_LINK option. The requestor
will need to reissue LEASEQUERY messages using each of the
returned link-addresses to obtain the client's bindings.
3. If the server has no bindings for the client, neither the
OPTION_CLIENT_DATA nor OPTION_CLIENT_LINK option will be present.
An unsuccessful LEASEQUERY-REPLY is one that has an
OPTION_STATUS_CODE with an error code. Depending on the status code,
the requestor may try a different server (such as for NotAllowed,
NotConfigured, and UnknownQueryType), try a different or corrected
query (such as for UnknownQueryType and MalformedQuery), or terminate
the query.
4.3.4. Handling DHCPv6 Client Data from Multiple Sources
A requestor may receive lease data on the same client from the same
DHCPv6 server in response to different types of LEASEQUERY. If a
LEASEQUERY is sent to multiple servers, the requestor may receive
from several servers lease data on the same DHCPv6 client.
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Additionally, if a requestor is an access concentrator, it may
receive lease data from other than leasequery exchanges, e.g., [7].
This section describes how the requestor handles multiple lease data
sources on the same DHCPv6 client from the same server or different
servers.
The client data from the different sources may be disjoint or
overlapping. The disjoint and overlapping relationship can happen
between data from the same server or different servers.
If client data from two sources on the same client are of different
types or values, then the data are disjoint. An example of data of
different types is when a requestor receives an IPv6 address lease
from one server and a prefix lease from another server, both assigned
to the same client. An example of different values (but the same
type) is when a requestor receives two IPv6 address leases from two
different servers, both assigned to the same client, but the leases
are on two different IPv6 addresses. If the requestor receives
disjoint client data from different sources, it SHOULD merge them.
If client data from two sources on the same client are of the same
type and value, then the data are overlapping. An example of
overlapping data is when a requestor receives a lease on the same
IPv6 address from two different servers. Overlapping client data are
also called conflicting data.
The requestor SHOULD use the OPTION_SERVER_RSN [5] to resolve data
conflicts originated from the same server, and SHOULD accept data
with the higher server-sequence-number. The requestor SHOULD use the
OPTION_CLT_TIME to resolve data conflicts originated from different
servers, and SHOULD accept data with most recent OPTION_CLT_TIME.
4.4. DHCPv6 Leasequery Server Behavior
A DHCPv6 server sends LEASEQUERY-REPLY messages in response to valid
LEASEQUERY messages it receives to return the statefully assigned
addresses, delegated prefixes, and other information about that match
the query.
4.4.1. Receipt of LEASEQUERY Messages
Upon receipt of a valid LEASEQUERY message, the DHCPv6 server locates
the requested client, collects data on the client, and constructs and
returns a LEASEQUERY-REPLY. A LEASEQUERY message can not be used to
assign, release, or otherwise modify bindings or other configuration
information.
The server constructs a LEASEQUERY-REPLY message by setting the "msg-
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type" field to LEASEQUERY-REPLY, and copying the transaction ID from
the LEASEQUERY message into the transaction-id field.
If the query-type in the OPTION_LQ_QUERY option is not a known or
supported value, the server adds an OPTION_STATUS_CODE option with
the UnknownQueryType status code and sends the LEASEQUERY-REPLY to
the requestor. If the query-options do not contain the required
options for the query-type, the server adds an OPTION_STATUS_CODE
option with the MalformedQuery status code and sends the LEASEQUERY-
REPLY to the client.
A server may also restrict LEASEQUERY messages, or query-types, to
certain requestors. In this case, the server MAY discard the
LEASEQUERY message or MAY add an OPTION_STATUS_CODE option with the
NotAllowed status code and send the LEASEQUERY-REPLY to the
requestor.
If the OPTION_LQ_QUERY specified a non-zero link-address, the server
MUST use the link-address to find the appropriate link for the
client. For a QUERY_BY_ADDRESS, if the 0::0 link-address was
specified, the server uses the address from the OPTION_IAADDR option
to find the appropriate link for the client. In either of these
cases, if the server is unable to find the link, it SHOULD return an
OPTION_STATUS_CODE option with the NotConfigured status and send the
LEASEQUERY-REPLY to the requestor.
For a QUERY_BY_CLIENTID, if a 0::0 link-address was specified, the
server MUST search all of its links for the client. If the client is
only found on a single link, the server SHOULD return that client's
data in an OPTION_CLIENT_DATA option. If the client is found on more
than a single link, the server MUST return the list of links in the
OPTION_CLIENT_LINK option; the server MUST NOT return any client
data.
Otherwise, the server uses the data in the OPTION_LQ_QUERY to
initiate the query. The result of the query will be zero or one
client. This will result in zero or one OPTION_CLIENT_DATA option
being added to the LEASEQUERY-REPLY.
4.4.2. Constructing the Client's OPTION_CLIENT_DATA
An OPTION_CLIENT_DATA option in a LEASEQUERY-REPLY message MUST
minimally contain the following data.
1. OPTION_CLIENTID
2. OPTION_IAADDR
3. OPTION_IAPREFIX
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4. OPTION_CLT_TIME
Depending on the bindings the client has on a link, either
OPTION_IAADDR options, OPTION_IAPREFIX options, or both may be
present.
The OPTION_CLIENT_DATA SHOULD include options requested in the
OPTION_ORO of the OPTION_LQ_QUERY option in the LEASEQUERY message
and that are acceptable to return based on the list of "sensitive
options", discussed below.
DHCPv6 servers SHOULD be configurable with a list of "sensitive
options" that must not be returned to the requestor when specified in
the OPTION_ORO of the OPTION_LQ_QUERY option in the LEASEQUERY
message. Any option on this list MUST NOT be returned to a
requestor, even if requested by that requestor.
4.4.3. Transmission of LEASEQUERY-REPLY Messages
The server sends the LEASEQUERY-REPLY message as described in the
"Transmission of Reply Messages" section of [2].
5. Security Considerations
The senders of LEASEQUERY messages are expected to be within the same
security domain as the DHCPv6 server. As such, the security threat
to DHCPv6 leasequery is inherently an insider threat. However, this
document doesn't prohibit entities in external security domains from
sending LEASEQUERY messages to DHCPv6 servers. Regardless of the
network configuration, however, the potential attacks by insiders and
outsiders are the same.
If the requestor is an access concentrator, DHCPv6 leasequery
security SHOULD follow security between the relay agent and the
DHCPv6 server as described in [2] Sections 21.1 and 22.11.
Requestors are essentially a DHCPv6 client for the purposes of the
LEASEQUERY message. Thus, DHCPv6 authentication [2] is also an
appropriate mechanism for securing LEASEQUERY and LEASEQUERY-REPLY
messages.
Access concentrators are expected to be common leasequery requestors.
Access concentrators that use DHCPv6 gleaning (i.e., [7]), refreshed
with LEASEQUERY messages, will maintain accurate client/binding
information. This ensures that the access concentrator can forward
data traffic to the intended destination in the broadband access
network, can perform IPv6 source address verification of datagrams
from the access network, and can encrypt traffic that can only be
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decrypted by the intended access modem (e.g., [BPI] and [BPI+]).
Thus, the LEASEQUERY message allows an access concentrator to provide
considerably enhanced security. DHCPv6 servers SHOULD prevent
exposure of their information (particularly the mapping of hardware
address to IPv6 address, which can be an invasion of broadband
subscriber privacy) by employing the techniques detailed in [2],
Section 21, "Authentication of DHCP Messages".
DHCPv6 servers SHOULD also provide for the ability to restrict the
information that they make via leasequery, as described in
Section 4.4.2.
DHCPv6 servers supporting LEASEQUERY SHOULD ensure that they cannot
be successfully attacked by being flooded with large quantities of
LEASEQUERY messages in a short time. In some environments, it may be
appropriate to configure a DHCPv6 server with the IPv6 source
addresses of the relay agents for which it may respond to LEASEQUERY
messages, thereby allowing it to respond only to requests from only a
handful of relay agents. This does not provide any true security,
but may be useful to thwart unsophisticated attacks of various sorts.
Replayed messages can represent a DOS attack through exhaustion of
processing resources, bogus leasequery requestors can send a lot of
LEASEQUERY messages to overwhelm a DHCPv6 server, thus preventing the
server from serving legitimate and regular DHCPv6 clients as well as
legitimate DHCPv6 leasequery requestors, denying configurations to
legitimate DHCPv6 clients as well lease information to legitimate
DHCPv6 leasequery requestors.
One attack specific to an access concentrator as a requestor is the
establishment of a malicious server with the intent of providing
incorrect lease or route information to the access concentrator,
thwarting source IPv6 address verification and preventing correct
routing.
The use of the OPTION_SERVER_RSN option [5] does provide an attacker
that also knows the server's DUID the ability to effectively lock out
future updates from the real server by supply a large sequence
number.
6. IANA Considerations
IANA is requested to assign the following new DHCPv6 Message types in
the registry maintained in
http://www.iana.org/assignments/dhcpv6-parameters:
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LEASEQUERY
LEASEQUERY-REPLY
IANA is requested to assign the following new DHCPv6 Option Codes in
the registry maintained in
http://www.iana.org/assignments/dhcpv6-parameters:
OPTION_LQ_QUERY
OPTION_CLIENT_DATA
OPTION_CLT_TIME
OPTION_LQ_RELAY_DATA
OPTION_LQ_CLIENT_LINK
IANA is requested to assign the following new DHCPv6 Status Codes in
the registry maintained in
http://www.iana.org/assignments/dhcpv6-parameters:
UnknownQueryType
MalformedQuery
NotConfigured
NotAllowed
IANA is requested to create a new registry for the OPTION_LQ_QUERY
option query-type codes in the registry maintained in
http://www.iana.org/assignments/dhcpv6-parameters with the following
initial assignments:
QUERY_BY_ADDRESS 1
QUERY_BY_CLIENTID 2
7. Acknowledgements
Thanks to Ralph Droms, Richard Johnson, Josh Littlefield, Hemant
Singh, Pak Siripunkaw, Markus Stenberg, and Ole Troan for their
input, ideas, and review during the production of this document.
8. Modification History
If this section is present in the document when it is submitted for
publication, the RFC Editor is requested to remove it.
Changes in rev -01:
o Added the ability to query by client identifier (DUID),
QUERY_BY_CLIENTID. To avoid potentially large messages for
clients that are multihomed or mobile, a new option,
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OPTION_LQ_CLIENT_LINK, to return the list of the links the client
is on was added. The requestor then needs to re-query for each
link, specifying the link-address in the query to get the client's
data.
o Added the ability to return full relay agent details via the
OPTION_LQ_RELAY_DATA option.
o And, other minor changes to accommodate the above.
9. References
9.1. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[2] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., and M.
Carney, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)",
RFC 3315, July 2003.
[3] Woundy, R. and K. Kinnear, "Dynamic Host Configuration Protocol
(DHCP) Leasequery", RFC 4388, February 2006.
[4] Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic Host
Configuration Protocol (DHCP) version 6", RFC 3633,
December 2003.
[5] Volz, B. and R. Droms, "DHCPv6 Server Reply Sequence Number
Option (draft-volz-dhc-dhcpv6-srsn-option-*)", August 2006.
9.2. Informative References
[6] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131,
March 1997.
[7] Droms, R., Volz, B., and O. Troan, "DHCP Relay Agent Assignment
Notification Option
(draft-ietf-dhc-dhcpv6-agentopt-delegate-*)", August 2006.
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Authors' Addresses
John Jason Brzozowski
Comcast Cable
1800 Bishops Gate Boulevard
Mt. Laurel, NJ 08054
USA
Phone: +1 856 324 2671
Email: john_brzozowski@cable.comcast.com
Kim Kinnear
Cisco Systems, Inc.
1414 Massachusetts Ave.
Boxborough, MA 01719
USA
Phone: +1 978 936 0000
Email: kkinnear@cisco.com
Bernard Volz
Cisco Systems, Inc.
1414 Massachusetts Ave.
Boxborough, MA 01719
USA
Phone: +1 978 936 0000
Email: volz@cisco.com
Shengyou Zeng
Cisco Systems, Inc.
1414 Massachusetts Ave.
Boxborough, MA 01719
USA
Phone: +1 978 936 0000
Email: szeng@cisco.com
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