Network Working Group S. Krishnan
Internet-Draft Ericsson
Intended status: Standards Track August 23, 2007
Expires: February 24, 2008
Neighbor Discovery Information over DHCP
draft-krishnan-dhc-ndc-option-00
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Copyright (C) The IETF Trust (2007).
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Abstract
Neighbor discovery options, in addition to being used for Neighbor
Discovery, are used to convey some forms of network configuration
information to the hosts attached to a network. Some centrally
managed networks, that do not wish to configure their routers to
advertise these pieces of information, might use a DHCP server to
configure there parameters. This document defines a generic DHCP
option for carrying these parameters.
Table of Contents
1. Requirements notation . . . . . . . . . . . . . . . . . . . . 3
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Applicability . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5. Neighbor Discovery Container(NDC) Option . . . . . . . . . . . 7
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
7. Security Considerations . . . . . . . . . . . . . . . . . . . 10
8. Normative References . . . . . . . . . . . . . . . . . . . . . 11
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 12
Intellectual Property and Copyright Statements . . . . . . . . . . 13
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1. Requirements notation
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].
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2. Introduction
Router Advertisements (RAs) as defined in [RFC2461] are used to
deliver configuration information that is common to several nodes in
the same network. The router advertisements are usually multicasted
to all nodes in a given network in order to be scalable. The
configuration information is contained in Neigbor Discovery (ND)
options. DHCP [RFC3315] is used for delivering addressing
information and other related configuration information to single
clients when they request it. Since there are two mechanisms for
delivering configuration information to a given node, configuration
parameters need to be defined under two varying option formats. This
leads to duplication of work needed to standardize these options and
additional implementation complexity on hosts in order to process
these option variants. In order to prevent this duplication, this
document proposes a DHCP option that can be used to directly carry
any neighbor discovery option.
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3. Applicability
It is possible to carry any neighbor discovery option using the NDC
option. This does not always make sense since there are neigbor
discovery options that are not related to configuration. The NDC
option SHOULD NOT be used to carry neighbor discovery options that
are not related to configuration. e.g. Source Link-layer Address,
Target Link-layer Address etc.
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4. Operation
After a DHCP client receives a message that contains a NDC option it
needs to verify if the NDC option length is at least 8 octets. If it
is not, the client MUST NOT process the NDC option any further and
SHOULD log an error message locally. Otherwise it needs to process
the embedded Neighbor Discovery options one at a time as it would if
it had received them through a Router Advertisement. It is entirely
possible that the code for processing these options is shared between
the RA based delivery and DHCP based delivery of these options.
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5. Neighbor Discovery Container(NDC) Option
The DHCP NDC option is used to carry complete neighbor discovery
options. There can be more than one neighbor discovery option that
is contained in a NDC. The number of contained options is not
explicitly mentioned in the NDC. The receiving node needs to process
all the contained options
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_NDC | Option Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPT1_Type | OPT1_Length | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| |
| OPT1_Data |
. .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTn_Type | OPTn_Length | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| |
| OPTn_Data |
. .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
OPTION_NDC
DHCP Option code allocated for the NDC option. To be
allocated by IANA out of the dhcpv6 parameters for option
codes.
Option Length
Length of the NDC option in octets not including the Option
Code and the Option Length fields. i.e. Combined length of
the included neighbor discovery options.
OPT1_Type
The neighbor discovery option type of the first included
option.
OPT1_Length
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The length of the first included option (including the
OPT1_Type and OPT1_Length fields) in units of 8 octets. The
value 0 is invalid.
OPT1_Data
The data field of the first included neighbor discovery
option. The contents of this field are determined by the type
of the option.
OPTn_Type
The neighbor discovery option type of the nth included option.
OPTn_Length
The length of the nth included option (including the OPT1_Type
and OPT1_Length fields) in units of 8 octets. The value 0 is
invalid.
OPTn_Data
The data field of the nth included neighbor discovery option.
The contents of this field are determined by the type of the
option.
Figure 1: NDC layout
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6. IANA Considerations
This document defines a new DHCPv6 option code for carrying neighbor
discovery options. IANA is requested to assign the following new
DHCPv6 Option Code in the registry maintained at
http://www.iana.org/assignments/dhcpv6-parameters:
OPTION_NDC
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7. Security Considerations
The mechanism described in this document provides a method by which
one or more neighbor discovery options can be carried using DHCP
messages. The DHCP messages containing the NDC option may be
intercepted, modified or replayed in order to communicate false
configuration data to the client hosts. In order to prevent these
kinds of attacks, it is recommended that authenticated DHCP [RFC3118]
be used.
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8. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2461] Narten, T., Nordmark, E., and W. Simpson, "Neighbor
Discovery for IP Version 6 (IPv6)", RFC 2461,
December 1998.
[RFC3118] Droms, R. and W. Arbaugh, "Authentication for DHCP
Messages", RFC 3118, June 2001.
[RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C.,
and M. Carney, "Dynamic Host Configuration Protocol for
IPv6 (DHCPv6)", RFC 3315, July 2003.
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Author's Address
Suresh Krishnan
Ericsson
8400 Decarie Blvd.
Town of Mount Royal, QC
Canada
Phone: +1 514 345 7900 x42871
Email: suresh.krishnan@ericsson.com
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