DHC B. Joshi
Internet-Draft R. Rao
Intended status: Standards Track Infosys Technologies Ltd.
Expires: December 6, 2011 M. Stapp
Cisco Systems, Inc.
June 4, 2011
The DHCPv4 Relay Agent Identifier Suboption
draft-ietf-dhc-relay-id-suboption-08.txt
Abstract
This draft defines a new Relay Agent Identifier suboption for the
Dynamic Host Configuration Protocol's (DHCP) Relay Agent Information
option. The suboption carries a value that uniquely identifies the
relay agent device within the administrative domain. The value is
typically administratively-configured in the relay agent. The
suboption allows a DHCP relay agent to include the identifier in the
DHCP messages it sends.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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Internet-Drafts are draft documents valid for a maximum of six months
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on December 6, 2011.
Copyright Notice
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document authors. All rights reserved.
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to this document. Code Components extracted from this document must
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Example Use-Cases . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. Industrial Ethernet . . . . . . . . . . . . . . . . . . . . 3
3.2. Bulk Leasequery . . . . . . . . . . . . . . . . . . . . . . 4
4. Suboption Format . . . . . . . . . . . . . . . . . . . . . . . 4
5. Relay Identifier Types . . . . . . . . . . . . . . . . . . . . 4
6. Identifier Stability . . . . . . . . . . . . . . . . . . . . . 5
7. Security Considerations . . . . . . . . . . . . . . . . . . . . 5
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 6
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6
10.1. Normative References . . . . . . . . . . . . . . . . . . . 6
10.2. Informative References . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7
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1. Introduction
The Dynamic Host Configuration Protocol for IPv4 (DHCPv4) [RFC2131]
provides IP addresses and configuration information for IPv4 clients.
It includes a relay agent capability, in which network elements
receive broadcast messages from clients and forward them to DHCP
servers as unicast messages. In many network environments, relay
agents add information to the DHCP messages before forwarding them,
using the Relay Agent Information option [RFC3046]. Servers that
recognize the relay agent information option echo it back in their
replies.
This specification introduces a Relay Agent Identifier suboption for
the Relay Agent Information option. The Relay-Id suboption carries a
sequence of octets that is intended to uniquely identify the relay
agent within the administrative domain.
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 [RFC2119].
DHCPv4 terminology is defined in [RFC2131], and the DHCPv4 Relay
Agent Information Option in [RFC3046].
3. Example Use-Cases
3.1. Industrial Ethernet
DHCP typically identifies clients based on information in their DHCP
messages - such as the Client-Identifier option, or the value of the
chaddr field. In some networks, however, the location of a client -
its point of attachment to the network - is a more useful identifier.
In factory-floor networks (commonly called 'Industrial' networks),
for example, the role a device plays is often fixed and based on its
location. Using manual address configuration is possible (and is
common) but it would be beneficial if DHCP configuration could be
applied to these networks.
One way to provide connection-based identifiers for industrial
networks is to have the network elements acting as DHCP relay agents
supply information that a DHCP server could use as a client
identifier. A straightforward way to form identifier information is
to combine something that is unique within the scope of the network
element, such as a port/slot value, with something that uniquely
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identifies that network element, such as a Relay Agent Identifier.
3.2. Bulk Leasequery
There has been quite a bit of recent interest in extending the DHCP
Leasequery protocol [RFC4388] to accommodate some additional
situations. There is a recent draft
([I-D.ietf-dhc-dhcpv4-bulk-leasequery]) proposing a variety of
enhancements to the existing Leasequery protocol. The draft
describes a use-case where a relay agent queries DHCP servers using
the Relay Identifier to retrieve all the leases allocated through the
relay agent.
4. Suboption Format
Format of the Relay Agent Identifier suboption:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|SUBOPT_RELAY_ID| length | type | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
. .
. identifier (variable) .
. .
+---------------------------------------------------------------+
Where:
SUBOPT_RELAY_ID [TBA]
length the number of octets in the suboption
(excluding the suboption ID and length fields);
the minimum length is two.
type a single octet describing the type of
identifier that is present.
identifier the identifying data.
5. Relay Identifier Types
For clarity, the suboption specified here includes a type octet that
describes the data used in the identifier field. The type value zero
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is reserved and MUST NOT be used. One type value is defined here:
RELAY_IDENTIFIER_OPAQUE. RELAY_IDENTIFIER_OPAQUE is used when the
identifier field contains a series of octets.
6. Identifier Stability
If the relay identifier is to be meaningful it has to be stable. A
relay agent SHOULD use a single identifier type and value
consistently. The identifier used by a relay device SHOULD be
committed to stable storage, unless the relay device can regenerate
the value upon reboot.
Relay agents SHOULD make their relay identifiers visible to their
administrators via their user interface, through a log entry, or
through some other mechanism. Among other uses, this is expected to
be useful to administrators in detecting misconfiguration of relay
identifiers (for example, multiple relay agents configured with the
same relay identifier).
Implementors should note that the identifier needs to be present in
all DHCP message types where its value is being used by the DHCP
server. The relay agent may not be able to add the Relay Agent
Information option to all messages - such as RENEW messages sent as
IP unicasts. In some deployments that might mean that the server has
to be willing to continue to associate the relay identifier it has
last seen with a lease that is being RENEWed. Other deployments may
prefer to use the Server Identifier Override suboption [RFC5107] to
permit the relay device to insert the Relay Agent Information option
into all relayed messages.
Handling situations where a relay agent device is replaced is another
aspect of "stability". One of the use-cases for the relay identifier
is to permit a server to associate clients' lease bindings with the
relay device connected to the clients. If the relay device is
replaced, because it has failed or been upgraded, it may be desirable
for the new device to continue to provide the same relay identifier
as the old device. Implementors should be aware of this possibility,
and consider making it possible for administrators to configure the
identifier.
7. Security Considerations
Security issues with the Relay Agent Information option and its use
by servers in address assignment are discussed in [RFC3046] and
[RFC4030]. Relay agents who send the Relay Agent Identifier
suboption SHOULD use the Relay Agent Authentication suboption
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[RFC4030] to provide integrity protection and to avoid duplication of
relay identifiers by malicious entities.
8. IANA Considerations
We request that IANA assign a new suboption code from the registry of
DHCP Agent Sub-Option Codes maintained in
http://www.iana.org/assignments/bootp-dhcp-parameters.
Relay Agent Identifier Suboption [TBA]
We request that IANA establish a new registry of DHCP Relay Agent
Identifier Sub-Option Types, to be maintained in
http://www.iana.org/assignments/bootp-dhcp-parameters. The
Identifier Type is a single octet. The initial values assigned in
this document are:
Reserved 0
RELAY_IDENTIFIER_OPAQUE 1
Additional Identifier Type values will be allocated and assigned
through IETF Review, as defined in [RFC5226].
9. Acknowledgments
Thanks to Ted Lemon, David W. Hankins and Bernie Volz for providing
valuable suggestions.
10. References
10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2131] Droms, R., "Dynamic Host Configuration Protocol",
RFC 2131, March 1997.
[RFC3046] Patrick, M., "DHCP Relay Agent Information Option",
RFC 3046, January 2001.
[RFC4030] Stapp, M. and T. Lemon, "The Authentication Suboption for
the Dynamic Host Configuration Protocol (DHCP) Relay Agent
Option", RFC 4030, March 2005.
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[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008.
10.2. Informative References
[RFC4388] Woundy, R. and K. Kinnear, "Dynamic Host Configuration
Protocol (DHCP) Leasequery", RFC 4388, February 2006.
[RFC5107] Johnson, R., Kumarasamy, J., Kinnear, K., and M. Stapp,
"DHCP Server Identifier Override Suboption", RFC 5107,
February 2008.
[I-D.ietf-dhc-dhcpv4-bulk-leasequery]
Kinnear, K., Volz, B., Russell, N., Stapp, M., Rao, D.,
Joshi, B., and P. Kurapati, "Bulk DHCPv4 Lease Query",
draft-ietf-dhc-dhcpv4-bulk-leasequery-04 (work in
progress), May 2011.
Authors' Addresses
Bharat Joshi
Infosys Technologies Ltd.
44 Electronics City, Hosur Road
Bangalore 560 100
India
Email: bharat_joshi@infosys.com
URI: http://www.infosys.com/
D.T.V Ramakrishna Rao
Infosys Technologies Ltd.
44 Electronics City, Hosur Road
Bangalore 560 100
India
Email: ramakrishnadtv@infosys.com
URI: http://www.infosys.com/
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Mark Stapp
Cisco Systems, Inc.
1414 Massachusetts Ave.
Boxborough, MA 01719
USA
Phone: +1 978 936 0000
Email: mjs@cisco.com
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