draft-ietf-dhc-leasequery-by-remote-id-09.txt   rfc6148.txt 
DHC Working Group P. Kurapati Internet Engineering Task Force (IETF) P. Kurapati
Internet-Draft Juniper Networks. Request for Comments: 6148 Juniper Networks
Updates: 4388 (if approved) R. Desetti Updates: 4388 R. Desetti
Intended status: Standards Track B. Joshi Category: Standards Track B. Joshi
Expires: June 6, 2011 Infosys Technologies Ltd. ISSN: 2070-1721 Infosys Technologies Ltd.
December 3, 2010 February 2011
DHCPv4 lease query by Relay Agent Remote ID DHCPv4 Lease Query by Relay Agent Remote ID
draft-ietf-dhc-leasequery-by-remote-id-09.txt
Abstract Abstract
Some Relay Agents extract lease information from the DHCP messages Some relay agents extract lease information from the DHCP messages
exchanged between the client and DHCP server. This lease information exchanged between the client and DHCP server. This lease information
is used by relay agents for various purposes like antispoofing and is used by relay agents for various purposes like antispoofing and
prevention of flooding. RFC 4388 defines a mechanism for relay prevention of flooding. RFC 4388 defines a mechanism for relay
agents to retrieve the lease information from the DHCP server when agents to retrieve the lease information from the DHCP server when
this information is lost. The existing lease query mechanism is data this information is lost. The existing lease query mechanism is
driven, which means that a relay agent can initiate the lease query data-driven, which means that a relay agent can initiate the lease
only when it starts receiving data from/to the clients. In certain query only when it starts receiving data to and from the clients. In
scenarios, this model is not scalable. This document first looks at certain scenarios, this model is not scalable. This document first
issues in existing mechanism and then proposes a new query type, looks at issues in the existing mechanism and then proposes a new
query by Remote ID, to address these issues. query type, query by Remote ID, to address these issues.
Status of this Memo
This Internet-Draft is submitted in full conformance with the Status of This Memo
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering This is an Internet Standards Track document.
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months This document is a product of the Internet Engineering Task Force
and may be updated, replaced, or obsoleted by other documents at any (IETF). It represents the consensus of the IETF community. It has
time. It is inappropriate to use Internet-Drafts as reference received public review and has been approved for publication by the
material or to cite them other than as "work in progress." Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
This Internet-Draft will expire on June 6, 2011. Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6148.
Copyright Notice Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
skipping to change at page 3, line 7 skipping to change at page 3, line 7
modifications of such material outside the IETF Standards Process. modifications of such material outside the IETF Standards Process.
Without obtaining an adequate license from the person(s) controlling Without obtaining an adequate license from the person(s) controlling
the copyright in such materials, this document may not be modified the copyright in such materials, this document may not be modified
outside the IETF Standards Process, and derivative works of it may outside the IETF Standards Process, and derivative works of it may
not be created outside the IETF Standards Process, except to format not be created outside the IETF Standards Process, except to format
it for publication as an RFC or to translate it into languages other it for publication as an RFC or to translate it into languages other
than English. than English.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction ....................................................3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6 2. Terminology .....................................................4
3. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . 8 3. Motivation ......................................................6
4. Protocol Details . . . . . . . . . . . . . . . . . . . . . . . 9 4. Protocol Details ................................................7
4.1. Sending the DHCPLEASEQUERY Message . . . . . . . . . . . . 9 4.1. Sending the DHCPLEASEQUERY Message .........................7
4.2. Responding to the DHCPLEASEQUERY Message . . . . . . . . . 10 4.2. Responding to the DHCPLEASEQUERY Message ...................8
4.3. Building a DHCPLEASEACTIVE or DHCPLEASEUNKNOWN message . . 10 4.3. Building a DHCPLEASEACTIVE or DHCPLEASEUNKNOWN Message .....8
4.4. Determining the IP address to be used in response . . . . 11 4.4. Determining the IP Address to Be Used in Response ..........9
4.5. Sending a DHCPLEASEACTIVE or DHCPLEASEUNKNOWN Message . . 11 4.5. Sending a DHCPLEASEACTIVE or DHCPLEASEUNKNOWN Message ......9
4.6. Receiving a DHCPLEASEACTIVE or DHCPLEASEUNKNOWN 4.6. Receiving a DHCPLEASEACTIVE or DHCPLEASEUNKNOWN Message ....9
Message . . . . . . . . . . . . . . . . . . . . . . . . . 11 4.7. Receiving No Response to the DHCPLEASEQUERY Message .......10
4.7. Receiving No Response to the DHCPLEASEQUERY Message . . . 12 4.8. Lease-Binding Data Storage Requirements ...................10
4.8. Lease Binding Data Storage Requirements . . . . . . . . . 12 4.9. Using the DHCPLEASEQUERY Message with Multiple
4.9. Using the DHCPLEASEQUERY Message with Multiple DHCP DHCP Servers ..............................................10
Servers . . . . . . . . . . . . . . . . . . . . . . . . . 12 5. RFC 4388 Considerations ........................................11
5. RFC 4388 Considerations . . . . . . . . . . . . . . . . . . . 13 6. Security Considerations ........................................11
6. Security Considerations . . . . . . . . . . . . . . . . . . . 14 7. Acknowledgments ................................................11
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15 8. References .....................................................12
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 16 8.1. Normative References ......................................12
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17 8.2. Informative References ....................................12
9.1. Normative Reference . . . . . . . . . . . . . . . . . . . 17
9.2. Informative Reference . . . . . . . . . . . . . . . . . . 17
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18
1. Introduction 1. Introduction
DHCP relay agents snoop DHCP messages and append a relay agent DHCP relay agents snoop DHCP messages and append a Relay Agent
information option before relaying them to the configured DHCP Information option before relaying them to the configured DHCP
Server. In this process, some relay agents also glean the lease server. In this process, some relay agents also glean the lease
information sent by the server and maintain this locally. This information sent by the server and maintain this locally. This
information is used to prevent spoofing attempts from clients and information is used to prevent spoofing attempts from clients and
also sometimes to install routing information. When a relay agent also sometimes to install routing information. When a relay agent
reboots, this information is lost. RFC 4388 [RFC4388] has defined a reboots, this information is lost. RFC 4388 [RFC4388] has defined a
mechanism to retrieve this lease information from the DHCP server. mechanism to retrieve this lease information from the DHCP server.
The existing query types defined by RFC 4388 [RFC4388] are data- The existing query types defined by RFC 4388 [RFC4388] are data-
driven. When a client sends data upstream, the relay agent can query driven. When a client sends data upstream, the relay agent can query
the server about the related lease information, based on the source the server about the related lease information, based on the source
MAC/IP address. These mechanisms do not scale well when there are MAC/IP address. These mechanisms do not scale well when there are
thousands of clients connected to the relay agent. In the data thousands of clients connected to the relay agent. In the data-
driven model, lease query does not provide the full and consolidated driven model, lease query does not provide the full and consolidated
active lease information associated with a given connection/circuit, active lease information associated with a given connection/circuit,
which will result in inefficient anti-spoofing. The relay agent also which will result in inefficient anti-spoofing. The relay agent also
has to contend with considerable resources for negative caching has to contend with considerable resources for negative caching,
specially under spoofing attacks. especially under spoofing attacks.
We need a mechanism for a relay agent to retrieve the consolidated We need a mechanism for a relay agent to retrieve the consolidated
lease information for a given connection/circuit before upstream lease information for a given connection/circuit before upstream
traffic is sent by the clients. traffic is sent by the clients.
+--------+ +--------+
| DHCP | +--------------+ | DHCP | +--------------+
| Server |-...-| DSLAM | | Server |-...-| DSLAM |
| | | Relay Agent | | | | Relay Agent |
+--------+ +--------------+ +--------+ +--------------+
skipping to change at page 4, line 47 skipping to change at page 4, line 22
|Modem1| |Modem2| |Modem1| |Modem2|
+------+ +------+ +------+ +------+
| | | | | |
+-----+ +-----+ +-----+ +-----+ +-----+ +-----+
|Node1| |Node2| |Node3| |Node1| |Node2| |Node3|
+-----+ +-----+ +-----+ +-----+ +-----+ +-----+
Figure 1 Figure 1
For example, when a DSLAM (Digital Subscriber Line Access For example, when a DSLAM (Digital Subscriber Line Access
Multiplexer) acting as a Relay Agent is rebooted, it should query the Multiplexer) acting as a relay agent is rebooted, it should query the
server for the lease information for all the connections/circuits. server for the lease information for all the connections/circuits.
Also, as shown in the above figure, there could be multiple clients Also, as shown in the above figure, there could be multiple clients
on one DSL circuit. The relay agent should get the lease information on one DSL circuit. The relay agent should get the lease information
of all the clients connected to a DSL circuit. This is possible by of all the clients connected to a DSL circuit. This is possible by
introducing a new query type based on the Remote ID sub-option of the introducing a new query type based on the Remote ID sub-option of the
Relay Agent Information option. This document talks about the Relay Agent Information option. This document talks about the
motivation for the new query type and the method to perform it. motivation for the new query type and the method to perform it.
2. Terminology 2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119]. document are to be interpreted as described in RFC 2119 [RFC2119].
This document uses the following terms: This document uses the following terms:
o "Access Concentrator" o Access Concentrator
An access concentrator is a router or switch at the broadband access An access concentrator is a router or switch at the broadband
provider's edge of a public broadband access network. This document access provider's edge of a public broadband access network. This
assumes that the access concentrator includes the DHCP relay agent document assumes that the access concentrator includes the DHCP
functionality. relay agent functionality.
o "DHCP client" o DHCP client
A DHCP client is an Internet node using DHCP to obtain configuration A DHCP client is an Internet node using DHCP to obtain
parameters such as a network address. configuration parameters such as a network address.
o "DHCP relay agent" o DHCP relay agent
A DHCP relay agent is a third-party agent that transfers Bootstrap A DHCP relay agent is a third-party agent that transfers Bootstrap
Protocol (BOOTP) and DHCP messages between clients and servers Protocol (BOOTP) and DHCP messages between clients and servers
residing on different subnets, per RFC 951 [RFC951] and RFC 1542 residing on different subnets, per RFC 951 [RFC951] and RFC 1542
[RFC1542]. [RFC1542].
o "DHCP server" o DHCP server
A DHCP server is an Internet node that returns configuration A DHCP server is an Internet node that returns configuration
parameters to DHCP clients. parameters to DHCP clients.
o "Fast path" o Fast path
Data transfer that happens through a Network Processor or an ASIC, Fast path refers to data transfer that happens through a network
which are programmed to forward the data at very high speeds. processor or an Application Specific Integrated Circuit (ASIC)
programmed to forward the data at very high speeds.
o "Gleaning" o Gleaning
Gleaning is the extraction of location information from DHCP Gleaning is the extraction of location information from DHCP
messages, as the messages are forwarded by the DHCP relay agent messages as the messages are forwarded by the DHCP relay agent
function. function.
o "Location information" o Location information
Location information is information needed by the access concentrator Location information is information needed by the access
to forward traffic to a broadband-accessible node. This information concentrator to forward traffic to a broadband-accessible node.
includes knowledge of the node's hardware address, the port or This information includes knowledge of the node's hardware
virtual circuit that leads to the node, and/or the hardware address address, the port or virtual circuit that leads to the node,
of the intervening subscriber modem. and/or the hardware address of the intervening subscriber modem.
o "MAC address" o MAC address
In the context of a DHCP packet, a MAC address consists of the In the context of a DHCP packet, a MAC address consists of the
following fields: hardware type "htype", hardware length "hlen", and following fields: hardware type ("htype"), hardware length
client hardware address "chaddr". ("hlen"), and client hardware address ("chaddr").
o "Slow path" o Slow path
Data transfer that happens through the control plane. This has very Slow path refers to data transfer that happens through the control
limited buffers to store data and the speeds are very low compared to plane. This has very limited buffers to store data, and the
the fast path data transfer. speeds are very low compared to the fast path data transfer.
o "Upstream" o Upstream
Upstream is the direction from the broadband subscriber towards the Upstream is the direction from the broadband subscriber towards
access concentrator. the access concentrator.
3. Motivation 3. Motivation
Consider an access concentrator (e.g., DSLAM) working also as a DHCP Consider an access concentrator (e.g., DSLAM) working also as a DHCP
relay agent. A "Fast path" and a "slow path" generally exist in most relay agent. A "fast path" and a "slow path" generally exist in most
networking boxes. Fast path processing is done in a network networking boxes. Fast path processing is done in a network
processor or an ASIC (Application Specific Integrated Circuit). Slow processor or an ASIC. Slow path processing is done in a normal
path processing is done in a normal processor. As much as possible, processor. As much as possible, regular data forwarding should be
regular data forwarding should be done in the fast path. Slow path done in the fast path. Slow path processing should be reduced, as it
processing should be reduced as it may become a bottleneck. may become a bottleneck.
For an access concentrator having multiple access ports, multiple IP For an access concentrator having multiple access ports, multiple IP
addresses may be assigned using DHCP to a single port and the number addresses may be assigned to a single port using DHCP, and the number
of clients on a port may be unknown. The access concentrator may of clients on a port may be unknown. The access concentrator may
also not know the network portions of the IP addresses that are also not know the network portions of the IP addresses that are
assigned to its DHCP clients. assigned to its DHCP clients.
The access concentrator gleans IP address or other information from The access concentrator gleans IP address or other information from
DHCP negotiations for antispoofing and other purposes. The DHCP negotiations for antispoofing and other purposes. The
antispoofing itself is done in the fast path. The access antispoofing itself is done in the fast path. The access
concentrator keeps track of only one list of IP addresses: list of IP concentrator keeps track of only one list of IP addresses: the list
addresses that are assigned by the DHCP servers; upstream traffic of IP addresses that are assigned by the DHCP servers; upstream
from all other IP addresses is dropped. If a client starts its data traffic from all other IP addresses is dropped. If a client starts
transfer after its DHCP negotiations have been gleaned by the access its data transfer after its DHCP negotiations have been gleaned by
concentrator, no legitimate packets will be dropped because of the access concentrator, no legitimate packets will be dropped
antispoofing. In other words, antispoofing is effective (no because of antispoofing. In other words, antispoofing is effective
legitimate packets are dropped and all spoofed packets are dropped) (no legitimate packets are dropped, and all spoofed packets are
and efficient (antispoofing is done in the fast path). The intention dropped) and efficient (antispoofing is done in the fast path). The
is to achieve similar effective and efficient antispoofing in the intention is to achieve similar effective and efficient antispoofing
lease query scenario also when an access concentrator loses its in the lease query scenario also, when an access concentrator loses
gleaned information (for example, because of a reboot). its gleaned information (for example, because of a reboot).
After a deep analysis, we found that the three existing query types After a deep analysis, we found that the three existing query types
supported by RFC 4388 [RFC4388] do not provide effective and supported by RFC 4388 [RFC4388] do not provide effective and
efficient antispoofing for the above scenario and a new mechanism is efficient antispoofing for the above scenario, and a new mechanism is
required. required.
The existing query types The existing query types necessitate a data-driven approach: the
lease queries can only be performed when the access concentrator
receives data. This results in
o necessitate a data-driven approach: the lease queries can only be o increased outage time for clients
performed when the access concentrator receives data. This
results in increased outage time for clients
o results in excessive negative caching, consuming a lot of o excessive negative caching, consuming a lot of resources under a
resources under a spoofing attack spoofing attack
o results in antispoofing being done in the slow path instead of the o antispoofing being done in the slow path instead of the fast path
fast path
4. Protocol Details 4. Protocol Details
This section talks about the protocol details for query by Remote ID. This section talks about the protocol details for query by Remote ID.
Most of the message handling is similar to RFC 4388 [RFC4388] and Most of the message handling is similar to RFC 4388 [RFC4388], and
this section highlights only the differences. Readers are advised to this section highlights only the differences. Readers are advised to
go through RFC 4388 [RFC4388] before going through this section for go through RFC 4388 [RFC4388] before going through this section for
complete understanding of the protocol. complete understanding of the protocol.
When used in this document, the unqualified term "DHCPLEASEQUERY" When used in this document, the unqualified term "DHCPLEASEQUERY"
indicates a lease query by Remote ID, unless otherwise specified. indicates a lease query by Remote ID, unless otherwise specified.
RFC 3046 [RFC3046] defines two sub-options for the Relay Agent RFC 3046 [RFC3046] defines two sub-options for the Relay Agent
Information option. Sub-option 1 corresponds to the Circuit ID that Information option. Sub-option 1 corresponds to the Circuit ID that
identifies the local circuit of the access concentrator. This sub- identifies the local circuit of the access concentrator. This
option is unique to the relay agent. Sub-option 2 corresponds to the sub-option is unique to the relay agent. Sub-option 2 corresponds to
Remote ID that identifies the remote node connected to the access the Remote ID that identifies the remote node connected to the access
concentrator. The Remote ID is globally unique in the network and is concentrator. The Remote ID is globally unique in the network and is
configured per circuit/connection in the relay agent. configured per circuit/connection in the relay agent.
This document defines a new query type based on the Remote ID sub- This document defines a new query type based on the Remote ID
option. Suppose that the access concentrator (e.g., DSLAM) lost the sub-option. Suppose that the access concentrator (e.g., DSLAM) lost
lease information when it was rebooted. When the access concentrator the lease information when it was rebooted. When the access
comes up, it initiates (for each connection/circuit) a DHCP lease concentrator comes up, it initiates (for each connection/circuit) a
query by Remote ID as defined in this section. For this query, the DHCP lease query by Remote ID as defined in this section. For this
requester supplies an option 82 that includes only a Remote ID sub- query, the requester supplies an option 82 that includes only a
option in the DHCPLEASEQUERY message. The Remote ID is normally pre- Remote ID sub-option in the DHCPLEASEQUERY message. The Remote ID is
provisioned in the access concentrator per circuit/connection and normally pre-provisioned in the access concentrator per circuit/
hence the same will remain available to the access concentrator after connection and hence will remain available to the access concentrator
reboot. after reboot.
The DHCP server MUST reply with a DHCPLEASEACTIVE message if there is The DHCP server MUST reply with a DHCPLEASEACTIVE message if there is
an active lease corresponding to the Remote ID that is present in the an active lease corresponding to the Remote ID that is present in the
DHCPLEASEQUERY message. Otherwise, the server MUST reply with a DHCPLEASEQUERY message. Otherwise, the server MUST reply with a
DHCPLEASEUNKNOWN message. Servers that do not implement DHCP lease DHCPLEASEUNKNOWN message. Servers that do not implement DHCP lease
query based on Remote ID SHOULD simply not respond. query based on Remote ID SHOULD simply not respond.
4.1. Sending the DHCPLEASEQUERY Message 4.1. Sending the DHCPLEASEQUERY Message
The lease query defined in this document will mostly be used by The lease query defined in this document will mostly be used by
skipping to change at page 10, line 7 skipping to change at page 8, line 11
message format as described in RFC 2131 [RFC2131], and uses message message format as described in RFC 2131 [RFC2131], and uses message
number 10 in the DHCP Message Type option (option 53). The number 10 in the DHCP Message Type option (option 53). The
DHCPLEASEQUERY message has the following pertinent message contents: DHCPLEASEQUERY message has the following pertinent message contents:
o There MUST be a Relay Agent Information option (option 82) with o There MUST be a Relay Agent Information option (option 82) with
only a Remote ID sub-option (sub-option 2) in the DHCPLEASEQUERY only a Remote ID sub-option (sub-option 2) in the DHCPLEASEQUERY
message. message.
o The Parameter Request List option [RFC2132] MUST be populated by o The Parameter Request List option [RFC2132] MUST be populated by
the access concentrator with the Associated-IP option code. The the access concentrator with the Associated-IP option code. The
giaddr field and other option codes listed in Parameter Request giaddr field and other option codes listed in the Parameter
List option are set as explained in section 6.2 of RFC 4388 Request List option are set as explained in Section 6.2 of
[RFC4388]. RFC 4388 [RFC4388].
o The ciaddr field MUST be set to zero. o The ciaddr field MUST be set to zero.
o The values of htype, hlen, and chaddr MUST be set to zero. o The values of htype, hlen, and chaddr MUST be set to zero.
o The Client Identifier option (option 61) MUST NOT appear in the o The Client Identifier option (option 61) MUST NOT appear in the
packet. packet.
The DHCPLEASEQUERY message SHOULD be sent to a DHCP server that is The DHCPLEASEQUERY message SHOULD be sent to a DHCP server that is
known to possess authoritative information concerning the Remote ID. known to possess authoritative information concerning the Remote ID.
skipping to change at page 10, line 32 skipping to change at page 8, line 36
possess authoritative information concerning the Remote ID, it SHOULD possess authoritative information concerning the Remote ID, it SHOULD
be sent to all DHCP servers configured for the associated relay agent be sent to all DHCP servers configured for the associated relay agent
(if any are known). (if any are known).
4.2. Responding to the DHCPLEASEQUERY Message 4.2. Responding to the DHCPLEASEQUERY Message
There are two possible responses to a DHCPLEASEQUERY message: There are two possible responses to a DHCPLEASEQUERY message:
o DHCPLEASEUNKNOWN o DHCPLEASEUNKNOWN
The DHCPLEASEUNKNOWN message indicates that the client associated The DHCPLEASEUNKNOWN message indicates that the client associated
with the Remote ID suboption of the DHCPLEASEQUERY message is not with the Remote ID sub-option of the DHCPLEASEQUERY message is not
allocated any lease or it is not managed by the server. allocated any lease or it is not managed by the server.
o DHCPLEASEACTIVE o DHCPLEASEACTIVE
The DHCPLEASEACTIVE message indicates that the server not only knows The DHCPLEASEACTIVE message indicates that the server not only
the client specified in the DHCPLEASEQUERY message, but also knows knows the client specified in the DHCPLEASEQUERY message, but also
that there is an active lease for that client. knows that there is an active lease for that client.
4.3. Building a DHCPLEASEACTIVE or DHCPLEASEUNKNOWN message 4.3. Building a DHCPLEASEACTIVE or DHCPLEASEUNKNOWN Message
A DHCPLEASEACTIVE message is built by populating information A DHCPLEASEACTIVE message is built by populating information
pertaining to the client associated with the IP address specified in pertaining to the client associated with the IP address specified in
the ciaddr field. the ciaddr field.
In the case where more than one IP address has been involved in a In the case where more than one IP address has been involved in a
DHCP message exchange with the client specified by the Remote ID, DHCP message exchange with the client specified by the Remote ID,
then the list of all those IP addresses MUST be returned in the then the list of all those IP addresses MUST be returned in the
Associated-IP option, whether or not that option was requested as Associated-IP option, whether or not that option was requested as
part of the Parameter Request List option. This is intended for part of the Parameter Request List option. This is intended for
maintaining backwards compatibility with RFC 4388 [RFC4388]. maintaining backwards compatibility with RFC 4388 [RFC4388].
All other options specified in the Parameter Request List [RFC2132] All other options specified in the Parameter Request List [RFC2132]
are processed as mentioned in section 6.4.2 of RFC 4388 [RFC4388]. are processed as mentioned in Section 6.4.2 of RFC 4388 [RFC4388].
In a DHCPLEASEUNKNOWN response message, the DHCP server MUST echo the In a DHCPLEASEUNKNOWN response message, the DHCP server MUST echo the
Option 82 received in the DHCPLEASEQUERY message. No other option is option 82 received in the DHCPLEASEQUERY message. No other option is
included in the message. included in the message.
4.4. Determining the IP address to be used in response 4.4. Determining the IP Address to Be Used in Response
The IP address placed in the ciaddr field of a DHCPLEASEACTIVE The IP address placed in the ciaddr field of a DHCPLEASEACTIVE
message MUST be the IP address with the latest client-last- message MUST be the IP address with the latest client-last-
transaction-time associated with the client described by the Remote transaction-time associated with the client described by the Remote
ID specified in the DHCPLEASEQUERY message. ID specified in the DHCPLEASEQUERY message.
If there is only a single IP address that fulfills this criteria, If there is only a single IP address that fulfills this criteria,
then it MUST be placed in the ciaddr field of the DHCPLEASEACTIVE then it MUST be placed in the ciaddr field of the DHCPLEASEACTIVE
message. message.
In the case where more than one IP address has been accessed by the In the case where more than one IP address has been accessed by the
client specified by the Remote ID, then the DHCP server MUST return client specified by the Remote ID, then the DHCP server MUST return
the IP address returned to the client in the most recent transaction the IP address returned to the client in the most recent transaction
with the client unless the DHCP server has been configured by the with the client, unless the DHCP server has been configured by the
server administrator to use some other preference mechanism. server administrator to use some other preference mechanism.
4.5. Sending a DHCPLEASEACTIVE or DHCPLEASEUNKNOWN Message 4.5. Sending a DHCPLEASEACTIVE or DHCPLEASEUNKNOWN Message
The server unicasts the DHCPLEASEACTIVE or DHCPLEASEUNKNOWN message The server unicasts the DHCPLEASEACTIVE or DHCPLEASEUNKNOWN message
to the address specified in the giaddr field of the DHCPLEASEQUERY to the address specified in the giaddr field of the DHCPLEASEQUERY
message. message.
4.6. Receiving a DHCPLEASEACTIVE or DHCPLEASEUNKNOWN Message 4.6. Receiving a DHCPLEASEACTIVE or DHCPLEASEUNKNOWN Message
When a DHCPLEASEACTIVE message is received in response to the When a DHCPLEASEACTIVE message is received in response to the
DHCPLEASEQUERY message, it means that there is currently an active DHCPLEASEQUERY message, it means that there is currently an active
lease associated with the Remote ID in the DHCP server. The access lease associated with the Remote ID in the DHCP server. The access
concentrator SHOULD use the information in the htype, hlen, and concentrator SHOULD use the information in the htype, hlen, and
chaddr fields of the DHCPLEASEACTIVE as well as the Relay Agent chaddr fields of the DHCPLEASEACTIVE message as well as the Relay
Information option included in the packet to refresh its location Agent Information option included in the packet to refresh its
information for this IP address. An access concentrator is likely to location information for this IP address. An access concentrator is
query by IP address for all the IP addresses specified in the likely to query by IP address for all the IP addresses specified in
Associated-IP option in the response, if any, at this point in time. the Associated-IP option in the response, if any, at this point in
time.
When a DHCPLEASEUNKNOWN message is received by an access concentrator When a DHCPLEASEUNKNOWN message is received by an access concentrator
that had sent out a DHCPLEASEQUERY message, it means that the DHCP that had sent out a DHCPLEASEQUERY message, it means that the DHCP
server does not have definitive information concerning the DHCP server does not have definitive information concerning the DHCP
client specified in the Remote ID sub-option of the DHCPLEASEQUERY client specified in the Remote ID sub-option of the DHCPLEASEQUERY
message. The access concentrator MAY store this information for message. The access concentrator MAY store this information for
future use. However, another DHCPLEASEQUERY message to the same DHCP future use. However, another DHCPLEASEQUERY message to the same DHCP
server SHOULD NOT be attempted with the same Remote ID sub-option. server SHOULD NOT be attempted with the same Remote ID sub-option.
For lease query by Remote ID, the impact of negative caching is For lease query by Remote ID, the impact of negative caching is
greatly reduced as the response leads to "definitive" information on greatly reduced, as the response leads to "definitive" information on
all the nodes connected behind the connection. Note that in case of all the nodes connected behind the connection. Note that in the case
the data-driven approach [RFC4388], a node spoofing several IP of the data-driven approach [RFC4388], a node spoofing several IP
addresses can lead to negative caching of greater magnitude. Another addresses can lead to negative caching of greater magnitude. Another
important change that this draft brings is the removal of periodic important change that this document brings is the removal of periodic
lease queries generated from negative caching caused by lease queries generated from negative caching caused by
DHCPLEASEUNKNOWN. Since the information obtained through query by DHCPLEASEUNKNOWN messages. Since the information obtained through
Remote ID is complete, there is no need of attempting lease query query by Remote ID is complete, there is no need to attempt lease
again for the same connection. query again for the same connection.
4.7. Receiving No Response to the DHCPLEASEQUERY Message 4.7. Receiving No Response to the DHCPLEASEQUERY Message
The condition of an access concentrator receiving no response to a The condition of an access concentrator receiving no response to a
DHCPLEASEQUERY message is handled in the same manner as suggested in DHCPLEASEQUERY message is handled in the same manner as suggested in
RFC 4388 [RFC4388]. RFC 4388 [RFC4388].
4.8. Lease Binding Data Storage Requirements 4.8. Lease-Binding Data Storage Requirements
Implementation Note: Implementation Note:
To generate replies for a lease query by Remote ID efficiently, a To generate replies for a lease query by Remote ID efficiently, a
DHCP server should index the lease binding data structures using DHCP server should index the lease-binding data structures using
Remote ID. Remote ID.
4.9. Using the DHCPLEASEQUERY Message with Multiple DHCP Servers 4.9. Using the DHCPLEASEQUERY Message with Multiple DHCP Servers
This scenario is handled in the same way it is done in RFC 4388 This scenario is handled in the same way it is done in RFC 4388
[RFC4388]. [RFC4388].
5. RFC 4388 Considerations 5. RFC 4388 Considerations
This document is compatible with RFC 4388 [RFC4388] based This document is compatible with RFC 4388-based [RFC4388]
implementations, which means that a client that supports this implementations, which means that a client that supports this
extension can work with a server not supporting this document, extension can work with a server not supporting this document,
provided it uses RFC 4388 [RFC4388] defined query types. Also, a provided it uses RFC 4388-defined query types. Also, a server
server supporting this document can work with a client not supporting supporting this document can work with a client not supporting this
this query type. However, there are some changes that this document query type. However, there are some changes that this document
proposes with respect to RFC 4388 [RFC4388]. Implementers extending proposes with respect to RFC 4388 [RFC4388]. Implementers extending
RFC 4388 [RFC4388] implementations to support this document should RFC 4388 [RFC4388] implementations to support this document should
take note of the following points: take note of the following points:
o There may be cases where a query by IP address/MAC address/Client o There may be cases where a query by IP address/MAC address/Client
Identifier has an option 82 containing Remote ID. In that case, Identifier has an option 82 containing a Remote ID. In that case,
the query will still be recognized as query by IP address/MAC the query will still be recognized as a query by IP address/MAC
address/Client Identifier as specified by RFC 4388 [RFC4388]. address/Client Identifier as specified by RFC 4388 [RFC4388].
o Section 6.4 of RFC 4388 [RFC4388] suggests that a DHCPLEASEUNKNOWN o Section 6.4 of RFC 4388 [RFC4388] suggests that a DHCPLEASEUNKNOWN
MUST NOT have any other option present. But for a query by Remote message MUST NOT have any other option present. But for a query
ID, option 82 MUST be present in the reply. by Remote ID, option 82 MUST be present in the reply.
6. Security Considerations 6. Security Considerations
This document inherits the security concerns present in the original This document inherits the security concerns present in the original
lease query protocol RFC 4388 [RFC4388] specifications. lease query protocol specification (RFC 4388 [RFC4388]).
This specification introduces one additional issue, beyond those This specification introduces one additional issue, beyond those
described in RFC 4388 [RFC4388]. A query by remote-id will result in described in RFC 4388 [RFC4388]. A query by Remote ID will result in
the server replying with a consolidated lease binding information. the server replying with consolidated lease-binding information.
Such a query, if done from an unauthorized source may lead to leak of Such a query, if done from an unauthorized source, may lead to a leak
lease binding information. It is critical to deploy authentication of lease-binding information. It is critical to deploy
techniques mentioned in RFC 3118 [RFC3118] to prevent such authentication techniques mentioned in RFC 3118 [RFC3118] to prevent
unauthorized lease queries. such unauthorized lease queries.
7. IANA Considerations
This document does not introduce any new namespaces for the IANA to
manage.
8. Acknowledgments 7. Acknowledgments
Copious amounts of text in this document are derived from RFC 4388 Copious amounts of text in this document are derived from RFC 4388
[RFC4388]. Kim Kinnear, Damien Neil, Stephen Jacob, Ted Lemon, Ralph [RFC4388]. Kim Kinnear, Damien Neil, Stephen Jacob, Ted Lemon, Ralph
Droms and Alfred Hoenes provided valuable feedback on this document. Droms, and Alfred Hoenes provided valuable feedback on this document.
9. References 8. References
9.1. Normative Reference 8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4388] Woundy, R. and K. Kinnear, "Dynamic Host Configuration [RFC4388] Woundy, R. and K. Kinnear, "Dynamic Host Configuration
Protocol (DHCP) Leasequery", RFC 4388, February 2006. Protocol (DHCP) Leasequery", RFC 4388, February 2006.
[RFC2131] Droms, R., "Dynamic Host Configuration Protocol", [RFC2131] Droms, R., "Dynamic Host Configuration Protocol",
RFC 2131, March 1997. RFC 2131, March 1997.
[RFC2132] Droms, R. and S. Alexander, "DHCP Options and BOOTP Vendor [RFC2132] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor
Extensions", RFC 2132, March 1997. Extensions", RFC 2132, March 1997.
[RFC3046] Patrick, M., "DHCP Relay Agent Information Option", [RFC3046] Patrick, M., "DHCP Relay Agent Information Option",
RFC 3046, January 2001. RFC 3046, January 2001.
[RFC3118] Droms, R. and W. Arbaugh, "Authentication for DHCP [RFC3118] Droms, R., Ed. and W. Arbaugh, Ed., "Authentication for
Messages", RFC 3118, June 2001. DHCP Messages", RFC 3118, June 2001.
9.2. Informative Reference 8.2. Informative References
[RFC951] Croft, B. and J. Gilmore, "Bootstrap Protocol (BOOTP)", [RFC951] Croft, B. and J. Gilmore, "Bootstrap Protocol (BOOTP)",
RFC 951, September 1985. RFC 951, September 1985.
[RFC1542] Wimer, W., "Clarifications and Extensions for the [RFC1542] Wimer, W., "Clarifications and Extensions for the
Bootstrap Protocol", RFC 1542, October 1993. Bootstrap Protocol", RFC 1542, October 1993.
Authors' Addresses Authors' Addresses
Pavan Kurapati Pavan Kurapati
Juniper Networks. Juniper Networks
Embassy Prime Buildings, C.V.Raman Nagar Embassy Prime Buildings, C.V. Raman Nagar
Bangalore 560 093 Bangalore 560 093
India India
Email: kurapati@juniper.net EMail: kurapati@juniper.net
URI: http://www.juniper.net/ URI: http://www.juniper.net/
D.T.V Ramakrishna Rao D.T.V Ramakrishna Rao
Infosys Technologies Ltd. Infosys Technologies Ltd.
44 Electronics City, Hosur Road 44 Electronics City, Hosur Road
Bangalore 560 100 Bangalore 560 100
India India
Email: ramakrishnadtv@infosys.com EMail: ramakrishnadtv@infosys.com
URI: http://www.infosys.com/ URI: http://www.infosys.com/
Bharat Joshi Bharat Joshi
Infosys Technologies Ltd. Infosys Technologies Ltd.
44 Electronics City, Hosur Road 44 Electronics City, Hosur Road
Bangalore 560 100 Bangalore 560 100
India India
Email: bharat_joshi@infosys.com EMail: bharat_joshi@infosys.com
URI: http://www.infosys.com/ URI: http://www.infosys.com/
 End of changes. 78 change blocks. 
201 lines changed or deleted 190 lines changed or added

This html diff was produced by rfcdiff 1.41. The latest version is available from http://tools.ietf.org/tools/rfcdiff/