Internet Research Task Force (IRTF) RJ Atkinson
Request for Comments: 6747 Consultant
Category: Experimental SN Bhatti
ISSN: 2070-1721 U. St Andrews
November 2012
Address Resolution Protocol (ARP)
for the Identifier-Locator Network Protocol for IPv4 (ILNPv4)
Abstract
This document defines an Address Resolution Protocol (ARP) extension
to support the Identifier-Locator Network Protocol for IPv4 (ILNPv4).
ILNP is an experimental, evolutionary enhancement to IP. This
document is a product of the IRTF Routing Research Group.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for examination, experimental implementation, and
evaluation.
This document defines an Experimental Protocol for the Internet
community. This document is a product of the Internet Research Task
Force (IRTF). The IRTF publishes the results of Internet-related
research and development activities. These results might not be
suitable for deployment. This RFC represents the individual
opinion(s) of one or more members of the Routing Research Group of
the Internet Research Task Force (IRTF). Documents approved for
publication by the IRSG are not a candidate for any level of Internet
Standard; see Section 2 of RFC 5741.
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/rfc6747.
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RFC 6747 ILNPv4 ARP November 2012
Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document.
This document may not be modified, and derivative works of it may not
be created, except to format it for publication as an RFC or to
translate it into languages other than English.
Table of Contents
1. Introduction ....................................................3
1.1. ILNP Document Roadmap ......................................3
1.2. Terminology ................................................5
2. ARP Extensions for ILNPv4 .......................................5
2.1. ILNPv4 ARP Request Packet Format ...........................5
2.2. ILNPv4 ARP Reply Packet Format .............................7
2.3. Operation and Implementation of ARP for ILNPv4 .............8
3. Security Considerations .........................................9
4. IANA Considerations .............................................9
5. References .....................................................10
5.1. Normative References ......................................10
5.2. Informative References ....................................11
6. Acknowledgements ...............................................11
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1. Introduction
This document is part of the ILNP document set, which has had
extensive review within the IRTF Routing RG. ILNP
is one of the recommendations made by the RG Chairs. Separately,
various refereed research papers on ILNP have also been published
during this decade. So, the ideas contained herein have had much
broader review than the IRTF Routing RG. The views in this
document were considered controversial by the Routing RG, but the
RG reached a consensus that the document still should be
published. The Routing RG has had remarkably little consensus on
anything, so virtually all Routing RG outputs are considered
controversial.
At present, the Internet research and development community are
exploring various approaches to evolving the Internet
Architecture to solve a variety of issues including, but not
limited to, scalability of inter-domain routing [RFC4984]. A wide
range of other issues (e.g., site multihoming, node multihoming,
site/subnet mobility, node mobility) are also active concerns at
present. Several different classes of evolution are being
considered by the Internet research and development community. One
class is often called "Map and Encapsulate", where traffic would
be mapped and then tunnelled through the inter-domain core of the
Internet. Another class being considered is sometimes known as
"Identifier/Locator Split". This document relates to a proposal
that is in the latter class of evolutionary approaches.
The Identifier Locator Network Protocol (ILNP) is a proposal for
evolving the Internet Architecture. It differs from the current
Internet Architecture primarily by deprecating the concept of an
IP Address, and instead defining two new objects, each having
crisp syntax and semantics. The first new object is the Locator, a
topology-dependent name for a subnetwork. The other new object is
the Identifier, which provides a topology-independent name for a
node.
1.1. ILNP Document Roadmap
This document describes extensions to ARP for use with
ILNPv4.
The ILNP architecture can have more than one engineering
instantiation. For example, one can imagine a "clean-slate"
engineering design based on the ILNP architecture. In separate
documents, we describe two specific engineering instances of
ILNP. The term ILNPv6 refers precisely to an instance of ILNP that
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is based upon, and backwards compatible with, IPv6. The term ILNPv4
refers precisely to an instance of ILNP that is based upon, and
backwards compatible with, IPv4.
Many engineering aspects common to both ILNPv4 and ILNPv6 are
described in [RFC6741]. A full engineering specification for
either ILNPv6 or ILNPv4 is beyond the scope of this document.
Readers are referred to other related ILNP documents for details
not described here:
a) [RFC6740] is the main architectural description of ILNP,
including the concept of operations.
b) [RFC6741] describes engineering and implementation
considerations that are common to both ILNPv4 and ILNPv6.
c) [RFC6742] defines additional DNS resource records that
support ILNP.
d) [RFC6743] defines a new ICMPv6 Locator Update message
used by an ILNP node to inform its correspondent nodes
of any changes to its set of valid Locators.
e) [RFC6744] defines a new IPv6 Nonce Destination Option
used by ILNPv6 nodes (1) to indicate to ILNP correspondent
nodes (by inclusion within the initial packets of an ILNP
session) that the node is operating in the ILNP mode and
(2) to prevent off-path attacks against ILNP ICMP messages.
This Nonce is used, for example, with all ILNP ICMPv6
Locator Update messages that are exchanged among ILNP
correspondent nodes.
f) [RFC6745] defines a new ICMPv4 Locator Update message
used by an ILNP node to inform its correspondent nodes
of any changes to its set of valid Locators.
g) [RFC6746] defines a new IPv4 Nonce Option used by ILNPv4
nodes to carry a security nonce to prevent off-path attacks
against ILNP ICMP messages and also defines a new IPv4
Identifier Option used by ILNPv4 nodes.
h) [RFC6748] describes optional engineering and deployment
functions for ILNP. These are not required for the operation
or use of ILNP and are provided as additional options.
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1.2. 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].
2. ARP Extensions for ILNPv4
ILNP for IPv4 (ILNPv4) is merely a different instantiation of the
ILNP architecture, so it retains the crisp distinction between the
Locator and the Identifier. As with ILNPv6, only the Locator
values are used for routing and forwarding ILNPv4 packets
[RFC6740]. As with ILNP for IPv6 (ILNPv6), when ILNPv4 is used
for a network-layer session, the upper-layer protocols (e.g.,
TCP/UDP pseudo-header checksum, IPsec Security Association) bind
only to the Identifiers, never to the Locators [RFC6741].
However, just as the packet format for IPv4 is different to IPv6,
so the engineering details for ILNPv4 are different also. While
ILNPv6 is carefully engineered to be fully backwards-compatible
with IPv6 Neighbor Discovery, ILNPv4 relies upon an extended
version of the Address Resolution Protocol (ARP) [RFC826], which
is defined here. While ILNPv4 could have been engineered to avoid
changes in ARP, that would have required that the ILNPv4 Locator
(i.e., L32) have slightly different semantics, which was
architecturally undesirable.
The packet formats used are direct extensions of the existing
widely deployed ARP Request (OP code 1) and ARP Reply (OP code 2)
packet formats. This design was chosen for practical engineering
reasons (i.e., to maximise code reuse), rather than for maximum
protocol design purity.
We anticipate that ILNPv6 is much more likely to be widely
implemented and deployed than ILNPv4. However, having a clear
definition of ILNPv4 helps demonstrate the difference between
architecture and engineering, and also demonstrates that the
common ILNP architecture can be instantiated in different ways
with different existing network-layer protocols.
2.1. ILNPv4 ARP Request Packet Format
The ILNPv4 ARP Request is an extended version of the widely
deployed ARP Request (OP code 1). For experimentation purposes,
the ILNPv4 ARP Request OP code uses decimal value 24. It is
important to note that decimal value 24 is a pre-defined,
shared-use experimental OP code for ARP [RFC5494], and is not
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uniquely assigned to ILNPv4 ARP Requests. The ILNPv4 ARP Request
extension permits the Node Identifier (NID) values to be carried
in the ARP message, in addition to the node's 32-bit Locator
(L32) values [RFC6742].
0 7 15 23 31
+--------+--------+--------+--------+
| HT | PT |
+--------+--------+--------+--------+
| HAL | PAL | OP |
+--------+--------+--------+--------+
| S_HA (bytes 0-3) |
+--------+--------+--------+--------+
| S_HA (bytes 4-5)|S_L32 (bytes 0-1)|
+--------+--------+--------+--------+
|S_L32 (bytes 2-3)|S_NID (bytes 0-1)|
+--------+--------+--------+--------+
| S_NID (bytes 2-5) |
+--------+--------+--------+--------+
|S_NID (bytes 6-7)| T_HA (bytes 0-1)|
+--------+--------+--------+--------+
| T_HA (bytes 3-5) |
+--------+--------+--------+--------+
| T_L32 (bytes 0-3) |
+--------+--------+--------+--------+
| T_NID (bytes 0-3) |
+--------+--------+--------+--------+
| T_NID (bytes 4-7) |
+--------+--------+--------+--------+
Figure 2.1: ILNPv4 ARP Request packet format
In Figure 2.1, the fields are as follows:
HT Hardware Type (*)
PT Protocol Type (*)
HAL Hardware Address Length (*)
PAL Protocol Address Length (uses new value 12)
OP Operation Code (uses experimental value OP_EXP1=24)
S_HA Sender Hardware Address (*)
S_L32 Sender L32 (* same as Sender IPv4 address for ARP)
S_NID Sender Node Identifier (8 bytes)
T_HA Target Hardware Address (*)
T_L32 Target L32 (* same as Target IPv4 address for ARP)
T_NID Target Node Identifier (8 bytes)
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The changed OP code indicates that this is ILNPv4 and not IPv4. The
semantics and usage of the ILNPv4 ARP Request are identical to the
existing ARP Request (OP code 2), except that the ILNPv4 ARP Request
is sent only by nodes that support ILNPv4.
The field descriptions marked with "*" should have the same values as
for ARP as used for IPv4.
2.2. ILNPv4 ARP Reply Packet Format
The ILNPv4 ARP Reply is an extended version of the widely deployed
ARP Reply (OP code 2). For experimentation purposes, the ILNPv4 ARP
Request OP code uses decimal value 25. It is important to note that
decimal value 25 is a pre-defined, shared-use experimental OP code
for ARP [RFC5494], and is not uniquely assigned to ILNPv4 ARP
Requests. The ILNPv4 ARP Reply extension permits the Node Identifier
(NID) values to be carried in the ARP message, in addition to the
node's 32-bit Locator (L32) values [RFC6742].
0 7 15 23 31
+--------+--------+--------+--------+
| HT | PT |
+--------+--------+--------+--------+
| HAL | PAL | OP |
+--------+--------+--------+--------+
| S_HA (bytes 0-3) |
+--------+--------+--------+--------+
| S_HA (bytes 4-5)|S_L32 (bytes 0-1)|
+--------+--------+--------+--------+
|S_L32 (bytes 2-3)|S_NID (bytes 0-1)|
+--------+--------+--------+--------+
| S_NID (bytes 2-5) |
+--------+--------+--------+--------+
|S_NID (bytes 6-7)| T_HA (bytes 0-1)|
+--------+--------+--------+--------+
| T_HA (bytes 3-5) |
+--------+--------+--------+--------+
| T_L32 (bytes 0-3) |
+--------+--------+--------+--------+
| T_NID (bytes 0-3) |
+--------+--------+--------+--------+
| T_NID (bytes 4-7) |
+--------+--------+--------+--------+
Figure 2.2: ILNPv4 ARP Reply packet format
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In Figure 2.2, the fields are as follows:
HT Hardware Type (*)
PT Protocol Type (*)
HAL Hardware Address Length (*)
PAL Protocol Address Length (uses new value 12)
OP Operation Code (uses experimental value OP_EXP2=25)
S_HA Sender Hardware Address (*)
S_L32 Sender L32 (* same as Sender IPv4 address for ARP)
S_NID Sender Node Identifier (8 bytes)
T_HA Target Hardware Address (*)
T_L32 Target L32 (* same as Target IPv4 address for ARP)
T_NID Target Node Identifier (8 bytes)
The changed OP code indicates that this is ILNPv4 and not IPv4. The
semantics and usage of the ILNPv4 ARP Reply are identical to the
existing ARP Reply (OP code 2), except that the ILNPv4 ARP Reply is
sent only by nodes that support ILNPv4.
The field descriptions marked with "*" should have the same values as
for ARP as used for IPv4.
2.3. Operation and Implementation of ARP for ILNPv4
The operation of ARP for ILNPv4 is almost identical to that for IPv4.
Essentially, the key differences are:
a) where an IPv4 ARP Request would use IPv4 addresses, an ILNPv4
ARP Request MUST use:
1. a 32-bit L32 value (_L32 suffixes in Figures 2.1 and 2.2)
2. a 64-bit NID value (_NID suffixes in Figures 2.1 and 2.2)
b) where an IPv4 ARP Reply would use IPv4 addresses, an ILNPv4 ARP
Reply MUST use:
1. a 32-bit L32 value (_L32 suffixes in Figures 2.1 and 2.2)
2. a 64-bit NID value (_NID suffixes in Figures 2.1 and 2.2)
As the OP codes 24 and 25 are distinct from ARP for IPv4, but the
packet formats in Figures 2.1 and 2.2 are, effectively, extended
versions of the corresponding ARP packets. It should be possible to
implement this extension of ARP by extending existing ARP
implementations rather than having to write an entirely new
implementation for ILNPv4. It should be emphasised, however, that OP
codes 24 and 25 are for experimental use as defined in [RFC5494], and
so it is possible that other experimental protocols could be using
these OP codes concurrently.
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3. Security Considerations
Security considerations for the overall ILNP architecture are
described in [RFC6740]. Additional common security considerations
applicable to ILNP are described in [RFC6741]. This section
describes security considerations specific to the specific ILNPv4
topics discussed in this document.
The existing widely deployed Address Resolution Protocol (ARP) for
IPv4 is a link-layer protocol, so it is not vulnerable to off-link
attackers. In this way, it is a bit different than IPv6 Neighbor
Discovery (ND); IPv6 ND is a subset of the Internet Control Message
Protocol (ICMP), which runs over IPv6.
However, ARP does not include any form of authentication, so current
ARP deployments are vulnerable to a range of attacks from on-link
nodes. For example, it is possible for one node on a link to forge
an ARP packet claiming to be from another node, thereby "stealing"
the other node's IPv4 address. [RFC5227] describes several of these
risks and some measures that an ARP implementation can use to reduce
the chance of accidental IPv4 address misconfiguration and also to
detect such misconfiguration if it should occur.
This extension does not change the security risks that are inherent
in using ARP.
In situations where additional protection against on-link attackers
is needed (for example, within high-risk operational environments),
the IEEE standards for link-layer security [IEEE-802.1-AE] SHOULD be
implemented and deployed.
Implementers of this specification need to understand that the two OP
code values used for these 2 extensions are not uniquely assigned to
ILNPv4. Other experimenters might be using the same two OP code
values at the same time for different ARP-related experiments.
Absent prior coordination among all users of a particular IP
subnetwork, different experiments might be occurring on the same IP
subnetwork. So, implementations of these two ARP extensions ought to
be especially defensively coded.
4. IANA Considerations
This document makes no request of IANA.
If in the future the IETF decided to standardise ILNPv4, then
allocation of unique ARP OP codes for the two extensions above would
be sensible as part of the IETF standardisation process.
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5. References
5.1. Normative References
[IEEE-802.1-AE] IEEE, "Media Access Control (MAC) Security", IEEE
Standard 802.1 AE, 18 August 2006, IEEE, New York,
NY, 10016, USA.
[RFC826] Plummer, D., "Ethernet Address Resolution Protocol:
Or Converting Network Protocol Addresses to 48.bit
Ethernet Address for Transmission on Ethernet
Hardware", STD 37, RFC 826, November 1982.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5227] Cheshire, S., "IPv4 Address Conflict Detection", RFC
5227, July 2008.
[RFC5494] Arkko, J. and C. Pignataro, "IANA Allocation
Guidelines for the Address Resolution Protocol
(ARP)", RFC 5494, April 2009.
[RFC6740] Atkinson, R. and S. Bhatti, "Identifier Locator
Network Protocol (ILNP) Architectural Description",
RFC 6740, November 2012.
[RFC6741] Atkinson, R. and S. Bhatti, "Identifier-Locator
Network Protocol (ILNP) Engineering and
Implementation Considerations", RFC 6741, November
2012.
[RFC6742] Atkinson, R., Bhatti, S., and S. Rose, "DNS Resource
Records for the Identifier-Locator Network Protocol
(ILNP)", RFC 6742, November 2012.
[RFC6745] Atkinson, R. and S. Bhatti, "ICMP Locator Update
Message for the Identifier-Locator Network Protocol
for IPv4 (ILNPv4)", RFC 6745, November 2012.
[RFC6746] Atkinson, R. and S.Bhatti, "IPv4 Options for the
Identifier-Locator Network Protocol (ILNP)", RFC
6746, November 2012.
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5.2. Informative References
[RFC4984] Meyer, D., Ed., Zhang, L., Ed., and K. Fall, Ed.,
"Report from the IAB Workshop on Routing and
Addressing", RFC 4984, September 2007.
[RFC6743] Atkinson, R. and S. Bhatti, "ICMPv6 Locator Update
Message", RFC 6743, November 2012.
[RFC6744] Atkinson, R. and S. Bhatti, "IPv6 Nonce Destination
Option for the Identifier-Locator Network Protocol
for IPv6 (ILNPv6)", RFC 6744, November 2012.
[RFC6748] Atkinson, R. and S. Bhatti, "Optional Advanced
Deployment Scenarios for the Identifier-Locator
Network Protocol (ILNP)", RFC 6748, November 2012.
6. Acknowledgements
Steve Blake, Stephane Bortzmeyer, Mohamed Boucadair, Noel Chiappa,
Wes George, Steve Hailes, Joel Halpern, Mark Handley, Volker Hilt,
Paul Jakma, Dae-Young Kim, Tony Li, Yakov Rehkter, Bruce Simpson,
Robin Whittle, and John Wroclawski (in alphabetical order) provided
review and feedback on earlier versions of this document. Steve
Blake provided an especially thorough review of an early version of
the entire ILNP document set, which was extremely helpful. We also
wish to thank the anonymous reviewers of the various ILNP papers for
their feedback.
Roy Arends provided expert guidance on technical and procedural
aspects of DNS issues.
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Authors' Addresses
RJ Atkinson
Consultant
San Jose, CA,
95125 USA
EMail: rja.lists@gmail.com
SN Bhatti
School of Computer Science
University of St Andrews
North Haugh, St Andrews,
Fife KY16 9SX
Scotland, UK
EMail: saleem@cs.st-andrews.ac.uk
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