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IETF RFC 6741
Last modified on Saturday, November 10th, 2012
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Internet Research Task Force (IRTF) RJ Atkinson
Request for Comments: 6741 Consultant
Category: Experimental SN Bhatti
ISSN: 2070-1721 U. St Andrews
November 2012
Identifier-Locator Network Protocol (ILNP)
Engineering Considerations
 Abstract
This document describes common (i.e., version independent)
engineering details for the Identifier-Locator Network Protocol
(ILNP), which 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/RFC 6741.
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RFC 6741 ILNP Engineering 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. Document Roadmap ...........................................4
1.2. Terminology ................................................5
2. ILNP Identifiers ................................................5
2.1. Syntax .....................................................6
2.2. Default Values for an Identifier ...........................6
2.3. Local-Scoped Identifier Values .............................6
2.4. Multicast Identifiers ......................................7
2.5. Administration of Identifier Values ........................7
3. Encoding of Identifiers and Locators for ILNPv6 .................7
3.1. Encoding of I and L Values .................................7
3.2. Network-Level Packet Formats ..............................10
3.3. Encoding of Identifiers and Locators for ILNPv4 ...........11
4. Transport-Layer Changes ........................................12
4.1. End-System State ..........................................12
4.2. TCP/UDP Checksum Handling .................................12
4.3. ICMP Checksum Handling ....................................12
5. ILNP Communication Cache (ILCC) ................................13
5.1. Formal Definition .........................................13
5.2. Ageing ILCC Entries .......................................15
5.3. Large Numbers of Locators .................................15
5.4. Lookups into the ILCC .....................................16
6. Handling Location/Connectivity Changes .........................16
6.1. Node Location/Connectivity Changes ........................16
6.2. Network Connectivity/Locator Changes ......................17
7. Subnetting .....................................................17
7.1. Subnetting for ILNPv6 .....................................18
7.2. Subnetting for ILNPv4 .....................................19
7.3. Subnetting for Router-Router Links in IPv6/ILNPv6 .........19
8. DNS Considerations .............................................19
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RFC 6741 ILNP Engineering November 2012
8.1. Secure Dynamic DNS Update .................................19
8.2. New DNS RR Types ..........................................20
8.4. DNS TTL Values for ILNP RRS Types .........................21
8.5. IP/ILNP Dual Operation and Transition .....................21
9. IP Security for ILNP ...........................................22
9.1. IPsec Security Association Enhancements for ILNP ..........22
9.2. IP Authentication Header Enhancements for ILNP ............23
9.3. Key Management Considerations .............................23
10. Backwards Compatibility and Incremental Deployment ............24
10.1. Priorities in the Design of ILNPv6 and ILNPv4 ............24
10.2. Infrastructure ...........................................25
10.3. Core Protocols ...........................................25
10.4. Scope of End-System Changes ..............................26
10.5. Applications .............................................27
10.6. Interworking between IP and ILNP .........................27
11. Security Considerations .......................................28
11.1. Authenticating ICMP Messages .............................29
11.2. Forged Identifier Attacks ................................31
12. Privacy Considerations ........................................31
13. Operational Considerations ....................................31
13.1. Session Liveness and Reachability ........................32
13.2. Key Management Considerations ............................33
13.3. Point-to-Point Router Links ..............................33
14. Referrals and Application Programming Interfaces ..............34
14.1. BSD Sockets APIs .........................................34
14.2. Java (and Other) APIs ....................................34
14.3. Referrals in the Future ..................................35
15. References ....................................................35
15.1. Normative References .....................................35
15.2. Informative References ...................................36
16. Acknowledgements ..............................................38
1. Introduction
The ILNP document set 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 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 is
exploring various approaches to evolving the Internet Architecture to
solve a variety of issues including, but not limited to, scalability
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RFC 6741 ILNP Engineering November 2012
of inter-domain routing [RFC 4984]. 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 an experimental
network protocol that provides evolutionary enhancements to IP. ILNP
is backwards compatible with IP and is incrementally deployable. The
best starting point for learning about ILNP is the ILNP Architectural
Description, which includes a document roadmap [RFC 6740].
1.1. Document Roadmap
This document describes engineering and implementation considerations
that are common to both ILNP for IPv4 (ILNPv4) and ILNP for IPv6
(ILNPv6).
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 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 this document. 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) [RFC 6740] is the main architectural description of ILNP, including
the concept of operations.
b) [RFC 6742] defines additional DNS resource records that support
ILNP.
c) [RFC 6743] 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.
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RFC 6741 ILNP Engineering November 2012
d) [RFC 6744] 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.
e) [RFC 6745] 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.
f) [RFC 6746] 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.
g) [RFC 6747] describes extensions to Address Resolution Protocol
(ARP) for use with ILNPv4.
h) [RFC 6748] 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.
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 [RFC 2119].
Several technical terms (e.g., "ILNP session") that are used by this
document are defined in [RFC 6740]. It is strongly recommended that
one read [RFC 6740] before reading this document.
2. ILNP Identifiers
All ILNP nodes must have at least one Node Identifier (or just
"Identifier") value. However, there are various options for
generating those Identifier values. We describe, in this section,
the relevant engineering issues related to Identifier generation and
usage.
Note well that an ILNP Node Identifier names an ILNP-capable node,
and it is NOT bound to a specific interface of that node. So a given
ILNP Node Identifier is valid on all active interfaces of the node to
which that ILNP Identifier is bound. This is true even if the bits
used to form the Identifier value happened to be taken from a
specific interface as an engineering convenience.
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RFC 6741 ILNP Engineering November 2012
2.1. Syntax
ILNP Identifiers are always unsigned 64-bit strings, and they may be
realised as 64-bit unsigned integers. Both ILNPv4 and ILNPv6 use the
Modified EUI-64 [IEEE-EUI] syntax that is used by IPv6 interface
identifiers [RFC 4291], Section 2.5.1, as shown in Figure 2.1.
+--------------------------------------------------+
| 6 id bits | U bit | G bit | 24 id bits |
+--------------------------------------------------+
| 32 id bits |
+--------------------------------------------------+
Figure 2.1: Node Identifier Format as Used for IPv6, Using the
Same Syntax as in RFC 4291, Section 2.5.1.
That syntax contains two special reserved bit flags. One flag (the U
bit) indicates whether the value has "universal" (i.e., global) scope
(1) or "local" (0) scope. The other flag (the G bit) indicates
whether the value is an "individual" address (1) or "group" (i.e.,
multicast) (0) address.
However, this format does allow other values to be set, by use of
administrative or other policy control, as required, by setting the U
bit to "local".
2.2. Default Values for an Identifier
By default, this value, including the U bit and G bit, are set as
described in Section 2.5.1 of [RFC 4291]. Where no other value of
Identifier is available for an ILNP node, this is the value that MUST
be used.
Because ILNP Identifiers might have local scope, and also to handle
the case where two nodes at different locations happen to be using
the same global scope Identifier (e.g., due to a manufacturing fault
in a network chipset or card), implementers must be careful in how
ILNP Identifiers are handled within an end system's networking
implementation. Some details are discussed in Section 4 below.
2.3. Local-Scoped Identifier Values
ILNP Identifiers for a node also MAY have the Scope bit of the Node
Identifier set to "local" scope. Locally unique identifiers MAY be
Cryptographically Generated, created following the procedures used
for IPv6 Cryptographically Generated Addresses (CGAs) [RFC 3972]
[RFC 4581] [RFC 4982].
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RFC 6741 ILNP Engineering November 2012
Also, locally unique identifiers MAY be used to create the ILNP
equivalent to the Privacy Extensions for IPv6, generating ILNP
Identifiers following the procedures used for IPv6 [RFC 4941].
2.4. Multicast Identifiers
An ILNP Identifier with the G bit set to "group" names an ILNP
multicast group, while an ILNP Identifier with the G bit set to
"individual" names an individual ILNP node. However, this usage of
multicast for Identifiers for ILNP is currently undefined: ILNP uses
IPv6 multicast for ILNPv6 and IPv4 multicast for ILNPv4 and uses the
multicast address formats defined as appropriate.
The use of multicast Identifiers and design of an enhanced multicast
capability for ILNPv6 and ILNPv4 is currently work in progress.
2.5. Administration of Identifier Values
Note that just as IPv6 does not need global, centralised
administrative management of its interface identifiers, so ILNPv6
does not need global, centralised administrative management of the
Node Identifier (NID) values.
3. Encoding of Identifiers and Locators for ILNPv6
3.1. Encoding of I and L Values
With ILNPv6, the Identifier and Locator values within a packet are
encoded in the existing space for the IPv6 address. In general, the
ILNPv6 Locator has the same syntax and semantics as the current IPv6
unicast routing prefix, as shown in Figure 3.1:
/* IPv6 */
| 64 bits | 64 bits |
+-------------------------------------+-------------------------+
| IPv6 Unicast Routing Prefix | Interface Identifier |
+-------------------------------------+-------------------------+
/* ILNPv6 */
| 64 bits | 64 bits |
+-------------------------------------+-------------------------+
| Locator | Node Identifier (NID) |
+-------------------------------------+-------------------------+
Figure 3.1: The General Format of Encoding of I/NID and L Values
for ILNPv6 into the IPv6 Address Bits
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RFC 6741 ILNP Engineering November 2012
The syntactical structure of the IPv6 address spaces remains as given
in Section 2.5.4 of [RFC 4291], and an example is shown in Figure 3.2,
which is based in part on [RFC 3177] (which has since been obsoleted
by [RFC 6177]).
/* IPv6 */
| 3 | 45 bits | 16 bits | 64 bits |
+---+---------------------+-----------+-------------------------+
|001|global routing prefix| subnet ID | Interface Identifier |
+---+---------------------+-----------+-------------------------+
/* ILNPv6 */
| 64 bits | 64 bits |
+---+---------------------+-----------+-------------------------+
| Locator (L64) | Node Identifier (NID) |
+---+---------------------+-----------+-------------------------+
Figure 3.2: Example of IPv6 Address Format as Used in ILNPv6
The global routing prefix bits and subnet ID bits above are as for
[RFC 3177], but could be different, e.g., as for [RFC 6177].
The ILNPv6 Locator uses the upper 64-bits of the 128-bit IPv6 address
space. It has the same syntax and semantics as today's IPv6 routing
prefix. So, an ILNPv6 packet carrying a Locator value can be used
just like an IPv6 packet today as far as core routers are concerned.
The example in Figure 3.2 happens to use a /48 prefix, as was
recommended by [RFC 3177]. However, more recent advice is that
prefixes need not be fixed at /48 and could be up to /64 [RFC 6177].
This change, however, does not impact the syntax or semantics of the
Locator value.
The ILNPv6 Identifier value uses the lower 64-bits of the 128-bit
IPv6 address. It has the same syntax as an IPv6 identifier, but
different semantics. This provides a fixed-length non-topological
name for a node. Identifiers are bound to nodes, not to interfaces
of a node. All ILNP Identifiers MUST comply with the modified EUI-64
syntax already specified for IPv6's "interface identifier" values, as
described in Section 2.1.
IEEE EUI-64 Identifiers can have either global-scope or local-scope.
So ILNP Identifiers also can have either global-scope or local-scope.
A reserved bit in the modified EUI-64 syntax clearly indicates
whether a given Identifier has global-scope or local-scope. A node
is not required to use a global-scope Identifier, although that is
the recommended practice. Note that the syntax of the Node
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RFC 6741 ILNP Engineering November 2012
Identifier field has exactly the same syntax as that defined for IPv6
address in Section 2.5.1 of [RFC 4291]. (This is based on the IEEE
EUI-64 syntax [IEEE-EUI], but is not the same.)
Most commonly, Identifiers have global-scope and are derived from one
or more IEEE 802 or IEEE 1394 'MAC Addresses' (sic) already
associated with the node, following the procedure already defined for
IPv6 [RFC 4291]. Global-scope identifiers have a high probability of
being globally unique. This approach eliminates the need to manage
Identifiers, among other benefits.
Local-scope Identifiers MUST be unique within the context of their
Locators. The existing mechanisms of the IPv4 Address Resolution
Protocol [RFC 826] and IPv6 Stateless Address Autoconfiguration
(SLAAC) [RFC 4862] automatically enforce this constraint.
For example, on an Ethernet-based IPv4 subnetwork the ARP Reply
message is sent via link-layer broadcast, thereby advertising the
current binding between an IPv4 address and a Media Access Control
(MAC) address to all nodes on that IPv4 subnetwork. (Note also that
a well-known, long standing, issue with ARP is that it cannot be
authenticated.) Local-scope Identifiers MUST NOT be used with other
Locators without first ensuring uniqueness in the context of those
other Locators e.g., by using IPv6 Neighbour Discovery's Duplicate
Address Detection mechanism when using ILNPv6 or by sending an ARP
Request when using ILNPv4.
Other methods might be used to generate local-scope Identifiers. For
example, one might derive Identifiers using some form of
cryptographic generation or using the methods specified in the IPv6
Privacy Extensions [RFC 4941] to Stateless Address Autoconfiguration
(SLAAC) [RFC 4862]. When cryptographic generation of Identifiers
using methods described in RFC 3972 is in use, only the Identifier is
included, never the Locator, thereby preserving roaming capability.
One could also imagine creating a local-scope Identifier by taking a
cryptographic hash of a node's public key. Of course, in the
unlikely event of an Identifier collision, for example, when a node
has chosen to use a local-scope Identifier value, the node remains
free to use some other local-scope Identifier value(s).
It is worth remembering here that an IPv6 address names a specific
network interface on a specific node, but an ILNPv6 Identifier names
the node itself, not a specific interface on the node. This
difference in definition is essential to providing seamless support
for mobility and multihoming, which are discussed in more detail
later in this note.
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RFC 6741 ILNP Engineering November 2012
3.2. Network-Level Packet Formats
ILNPv6 Locator and Identifier values are encoded into IPv6 address
space and ILNPv6 uses directly the Classic IPv6 packet format, as
shown in Figure 3.3. This is also the view of an ILNPv6 packet as
seen by core routers -- they simply use the Locator value (top
64-bits of the address field) just as they would use an IPv6 prefix
today (e.g., either as /48 or as /64 when using sub-network routing).
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Version| Traffic Class | Flow Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Payload Length | Next Header | Hop Limit |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Address |
+ +
| |
+ +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination Address |
+ +
| |
+ +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3.3: Existing ("Classic") IPv6 Header
In essence, the Locator names a subnetwork. (Locators can also be
referred to as Routing Prefixes if discussing Classic IPv6). Of
course, backwards compatibility requirements mean that ILNPv6
Locators use the same number space as IPv6 routing prefixes. This
ensures that no changes are needed to deployed IPv6 routers when
deploying ILNPv6.
The low-order 64-bits of the IPv6 address become the Identifier.
Details of the Identifier were discussed above. The Identifier is
only used by end-systems, so Figure 3.4 shows the view of the same
packet format, but as viewed by an ILNPv6 node. As this only needs
to be parsed in this way by the end-system, so ILNPv6 deployment is
enabled incrementally by updating end-systems as required.
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RFC 6741 ILNP Engineering November 2012
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Version| Traffic Class | Flow Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Payload Length | Next Header | Hop Limit |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Locator |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Identifier |
| |
+ +
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination Locator |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination Identifier |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3.4: ILNPv6 Header as Seen by ILNPv6-Enabled End-Systems
3.3. Encoding of Identifiers and Locators for ILNPv4
Encoding of Identifier and Locator values for ILNPv4 is not as
straightforward as for ILNPv6. In analogy to ILNPv6, in ILNPv4, the
Locator value is a routing prefix for IPv4, but is at most 30 bits.
Source Locator values are carried in the source address field of the
IPv4 header, and destination Locator values in the destination
address field. So, just like for ILNPv6, for ILNPv4, packet routing
can be performed by routers examining existing prefix values in the
IPv4 header.
However, for ILNPv4, additional option headers have to be used to
carry the Identifier value as there is not enough room in the normal
IPv4 header fields. A 64-bit Identifier value is carried in an
option header. So, the detailed explanation of the ILNPv4 packet
header is to be found in [RFC 6746].
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RFC 6741 ILNP Engineering November 2012
4. Transport-Layer Changes
ILNP uses an Identifier value in order to form the invariant end-
system state for end-to-end protocols. Currently, transport
protocols such as TCP and UDP use all the bits of an IP Address to
form such state. So, transport protocol implementations MUST be
modified in order to operate over ILNP.
4.1. End-System State
Currently, TCP and UDP, for example, use the 4-tuple:
<local port, remote port, local IP Address, remote IP Address>
for the end-system state for a transport layer end-point. For ILNP,
implementations must be modified to instead use the following:
<local port, remote port, local Identifier, remote Identifier>
4.2. TCP/UDP Checksum Handling
In IP-based implementations, the TCP or UDP pseudo-header checksum
calculations include all the bits of the IP Address. By contrast,
when calculating the TCP or UDP pseudo-header checksums for use with
ILNP, only the Identifier values are included in the TCP or UDP
pseudo-header checksum calculations.
To minimise the changes required within transport protocol
implementations, and to maximise interoperability, current
implementations are modified to zero the Locator fields (only for the
purpose of TCP or UDP checksum calculations). For example, for
ILNPv6, this means that the existing code for IPv6 can be used, with
the ILNPv6 Identifier bits occupying the lower 64 bits of the IPv6
address field, and the upper 64 bits of the IPv6 address filed being
set to zero. For ILNPv4, the Identifier fields are carried in an
IPv4 Option [RFC 6746].
Section 7 describes methods for incremental deployment of this ILNP-
specific change and backwards compatibility with non-upgraded nodes
(e.g., classic IPv4 or IPv6 nodes) in more detail.
4.3. ICMP Checksum Handling
To maximise backwards compatibility, the ILNPv6 ICMP checksum is
always calculated in the same way as for IPv6 ICMP. Similarly, the
ILNPv4 ICMP checksum is always calculated in the same way as for IPv4
ICMP.
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RFC 6741 ILNP Engineering November 2012
5. ILNP Communication Cache (ILCC)
For operational purposes, implementations need to have a local cache
of state information that allow communication endpoints to be
constructed and for communication protocols to operate. Such cache
information is common today, e.g., IPv4 nodes commonly maintain an
Address Resolution Protocol (ARP) cache with information relating to
current and recent Correspondent Nodes (CNs); IPv6 nodes maintain a
Neighbor Discovery (ND) table with information relating to current
and CNs. Likewise, ILNP maintains an Identifier Locator
Communication Cache (ILCC) with information relating to the operation
of ILNP.
The ILCC is a (logical) set of data values required for ILNP to
operate. These values are maintained by the endpoints of each ILNP
session.
In theory, this cache is within the ILNP network-layer. However,
many network protocol implementations do not have strict protocol
separation or layering. So there is no requirement that the ILCC be
kept partitioned from transport-layer protocols.
Note that, in many implementations, much of the information required
for the ILCC may already be present. Where some additional
information is required for ILNP, from an engineering viewpoint, the
ILCC could be implemented by extending or enhancing existing data
structures within existing implementations. For example, by adding
appropriate flags to the data structures in existing implementations.
Note that the ILCC does not impose any extra state maintenance
requirements for applications or applications servers. For example,
in the case of, say, HTTP, there will be no additional state for a
server to maintain, and any TCP state will be handled by the ILNP
code in the OS just as for IP.
5.1. Formal Definition
The ILCC contains information about both the local node and also
about current or recent correspondent nodes, as follows.
Information about the local node:
- Each currently valid Identifier value, including its Identifier
Precedence and whether it is active at present.
- Each currently valid Locator value, including its associated
local interface(s), its Locator Precedence and whether it is
active at present.
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RFC 6741 ILNP Engineering November 2012
- Each currently valid IL Vector (I-LV), including whether it is
active at present.
Information about each correspondent node:
- Most recent set of Identifiers, including lifetime and validity
for each.
- Most recent set of Locators, including lifetime and validity for
each.
- Nonce value for packets from the local host to the
correspondent.
- Nonce value for packets from the correspondent to the local
host.
In the above list for the ILNP Communication Cache:
- A "valid" item is usable, from an administrative point of view,
but it might or might not be in use at present.
- The "validity" parameter for the correspondent node indicates
one of several different states for a datum. These include at
least the following:
- "valid": data is usable and has not expired.
- "active": data is usable, has not expired, and is in active
use at present.
- "expired": data is still in use at present, but is beyond its
expiration (i.e., without a replacement value).
- "aged": data was recently in use, but is not in active use at
present, and is beyond its expiration.
- The "lifetime" parameter is an implementation-specific
representation of the validity lifetime for the associated data
element. In normal operation, the Lifetime for a correspondent
node's Locator(s) are learned from the DNS Time-To-Live (DNS
TTL) value associated with DNS records (NID, L32, L64, etc.) of
the Fully Qualified Domain Name (FQDN) owner name of the
correspondent node. For time, a node might use UTC (e.g., via
Network Time Protocol) or perhaps some node-specific time (e.g.,
seconds since node boot).
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RFC 6741 ILNP Engineering November 2012
5.2. Ageing ILCC Entries
As a practical engineering matter, it is not sensible to flush all
Locator values associated with an existing ILNP session's
correspondent node even if the DNS TTL associated with those Locator
values expires.
In some situations, a CN might be disconnected briefly when moving
location (e.g., immediate handover, which sometimes is called "break
before make"). If this happens, there might be a brief pause before
the Correspondent Node can (a) update its own L values in the DNS,
and (b) send an ICMP Locator Update message to the local node with
information about its new location. Implementers ought to try to
maintain ILNP sessions even when such events occur.
Instead, Locator values cached for a correspondent node SHOULD be
marked as "aged" when their TTL has expired, but retained until
either the next Locator Update message is received, there is other
indication that a given Locator is not working any longer, there is
positive indication that the Correspondent Node has terminated the
ILNP session (e.g., TCP RST if the only transport-layer session for
this ILNP session is a TCP session), until some appropriate timeout
(e.g., 2*MSL for TCP if the only transport-layer session for this
ILNP session is a TCP session), or the ILNP session has been inactive
for several minutes (e.g., no transport-layer session exists for this
ILNP session) and the storage space associated with the aged entry
needs to be reclaimed.
Separately, received authenticated Locator Update messages cause the
ILCC entries listed above to be updated.
Similarly, if there is indication that an ILNP session with a
Correspondent Node remains active and the DNS TTL associated with
that Correspondent Node's active Identifier value(s) has expired,
those remote Identifier value(s) ought to be marked as "expired", but
retained since they are in active use.
5.3. Large Numbers of Locators
Implementers should keep in mind that a node or site might have a
large number of concurrent Locators, and it should ensure that a
system fault does not arise if the system receives an authentic ICMP
Locator Update containing a large number of Locator values.
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RFC 6741 ILNP Engineering November 2012
5.4. Lookups into the ILCC
For received packets containing an ILNP Nonce Option, lookups in the
ILCC MUST use the <remote Identifier, Nonce> tuple as the lookup key.
For all other ILNP packets, lookups in the ILNP Correspondent Cache
MUST use the <remote Locator, remote Identifier> tuple, i.e., the
remote I-LV, as the lookup key.
These two checks between them facilitate situations where, perhaps
due to deployment of Local-scope Identifiers, more than one
correspondent node is using the same Identifier value.
(NOTE: Other mechanisms, such as IPv6 Neighbor Discovery, ensure that
two different nodes are incapable of using a given I-LV at the same
location, i.e., on the same link.)
While Locators are omitted from the transport-layer checksum, an
implementation SHOULD use Locator values to distinguish between
correspondents coincidentally using the same Identifier value (e.g.,
due to deployment of Local-scope Identifier values) when
demultiplexing to determine which application(s) should receive the
user data delivered by the transport-layer protocol.
6. Handling Location/Connectivity Changes
In normal operation, an ILNP node uses the DNS for initial rendezvous
in setting up ILNP sessions. The use of DNS for initial rendezvous
with mobile nodes was earlier proposed by others [PHG02] and then
separately reinvented by the current authors later on.
6.1. Node Location/Connectivity Changes
To handle the move of a node or a change to the upstream connectivity
of a multihomed node, we add a new ICMP control message [RFC 6745]
[RFC 6743]. The ICMP Locator Update (LU) message is used by a node to
inform its existing CNs that the set of valid Locators for the node
has changed. This mechanism can be used to add newly valid Locators,
to remove no longer valid Locators, or to do both at the same time.
The LU mechanism is analogous to the Binding Update mechanism in
Mobile IPv6, but in ILNP, such messages are used any time Locator
value changes need to be notified to CNs, e.g., for multihomed hosts
as well as for mobile hosts.
Further, if the node wishes to be able to receive new incoming ILNP
sessions, the node normally uses Secure Dynamic DNS Update [RFC 3007]
to ensure that a correct set of Locator values are present in the
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RFC 6741 ILNP Engineering November 2012
appropriate DNS records (i.e., L32, L64) in the DNS for that node
[RFC 6742]. This enables any new correspondents to correctly initiate
a new ILNP session with the node at its new location.
While the Locator Update control message could be an entirely new
protocol running over UDP, for example, there is no obvious advantage
to creating a new protocol rather than using a new ICMP message. So
ILNP defines a new ICMP Locator Update message for both IPv4 and
IPv6.
6.2. Network Connectivity/Locator Changes
As a DNS performance optimisation, the LP DNS resource record MAY be
used to avoid requiring each node on a subnetwork to update its DNS
L64 record entries when that subnetwork's location (e.g., upstream
connectivity) changes [RFC 6742]. This can reduce the number of DNS
updates required when a subnetwork moves from Order (number of nodes
on subnetwork) to Order(1).
In this case, the nodes on the subnetwork each would have an LP
record pointing to a common FQDN used to name that subnetwork. In
turn, that subnetwork's domain name would have one or more L64
record(s) in the DNS. Since the contents of an LP record are stable,
relatively long DNS TTL values can be associated with these records
facilitating DNS caching. By contrast, the DNS TTL of an L32 or L64
record for a mobile or multihomed node should be small. Experimental
work at the University of St Andrews indicates that the DNS continues
to work well even with very low (e.g., zero) DNS TTL values [BA11].
Correspondents of a node on a mobile subnetwork using this DNS
performance optimisation would initially perform a normal FQDN lookup
for a node. If that lookup returned another FQDN in an LP record as
additional data, then the correspondent would perform a lookup on
that FQDN and expect an L32 or L64 record returned as additional
data, in order to learn the Locator value to use to reach that target
node. (Of course, a lookup that did not return any ILNP-related DNS
records would result in an ordinary IPv4 session or ordinary IPv6
session being initiated, instead.)
7. Subnetting
For ILNPv4 and ILNPv6, the Locator value includes the subnetting
information, as that also is topological information. As well as
being architecturally correct, the placement of subnetting as part of
the Locator is also convenient from an engineering point of view in
both IPv4 and IPv6.
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RFC 6741 ILNP Engineering November 2012
We consider that a Locator value, L consists of two parts:
- L_pp: the Locator prefix part, which occupies the most significant
bits in the address (for both ILNPv4 and ILNPv6).
- L_ss: Locator subnetwork selector, which occupies bits just after
the L_pp.
For each of ILNPv4 and ILNPv6, L_pp gets its value from the provider-
assigned routing prefix for IPv4 and IPv6, respectively. For L_ss,
in each case of ILNPv4 and ILNPv6, the L_ss bits are located in the
part of the address space which you might expect them to be located
if IPv4 or IPv6 addresses were being used, respectively.
7.1. Subnetting for ILNPv6
For ILNPv6, recall that the Locator value is encoded to be
syntactically similar to an IPv6 address prefix, as shown in Figure
7.1.
/* IPv6 */
| 3 | 45 bits | 16 bits | 64 bits |
+---+---------------------+-----------+-------------------------+
|001|global routing prefix| subnet ID | Interface Identifier |
+---+---------------------+-----------+-------------------------+
/* ILNPv6 */
| 64 bits | 64 bits |
+---+---------------------+-----------+-------------------------+
| Locator (L64) | Node Identifier (NID) |
+---+---------------------+-----------+-------------------------+
+<-------- L_pp --------->+<- L_ss -->+
L_pp = Locator prefix part (assigned IPv6 prefix)
L_ss = Locator subnet selector (locally managed subnet ID)
Figure 7.1: IPv6 Address Format [RFC 3587] as Used in ILNPv6,
Showing How Subnets Can Be Identified
Note that the subnet ID forms part of the Locator value. Note also
that [RFC 6177] allows the global routing prefix to be more than 45
bits, and for the subnet ID to be smaller, but still preserving the
64-bit size of the Locator.
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RFC 6741 ILNP Engineering November 2012
7.2. Subnetting for ILNPv4
For ILNPv4, the L_pp value is an IPv4 routing prefix as used today,
which is typically less than 32 bits. However, the ILNPv4 Locator
value is carried in the 32-bit IP Address space, so the bits not used
for the routing prefix could be used for L_ss, e.g., for a /24 IPv4
prefix, the situation would be as shown in Figure 7.2.
24 bits 8 bits
+------------------------+----------+
| Locator (L32) |
+------------------------+----------+
+<------- L_pp --------->+<- L_ss ->+
L_pp = Locator prefix part (assigned IPv4 prefix)
L_ss = Locator subnet selector (locally managed subnet ID)
Figure 7.2: IPv4 Address Format for /24 IPv4 Prefix, as Used in
ILNPv4, Showing How Subnets Can Be Identified
Note that the L_ss occupies bits that in an IPv4 address would
normally be the host part of the address, which the site network
could use for subnetting in any case.
7.3. Subnetting for Router-Router Links in IPv6/ILNPv6
There is a special case of /127 prefixes used in router-router,
point-to-point links for IPv6 [RFC 6164]. ILNPv6 does not preclude
such use.
8. DNS Considerations
ILNP makes use of DNS for name resolution, as does IP. Unlike IP,
ILNP also uses DNS to support features such as mobility and
multihoming. While such usage is appropriate use of the DNS, it is
important to discuss operational and engineering issues that may
impact DNS usage.
8.1. Secure Dynamic DNS Update
When a host that expects incoming connections changes one or more of
its Locator values, the host normally uses the IETF Secure Dynamic
DNS Update protocol [RFC 3007] to update the set of currently valid
Locator values associated with its FQDN. This ensures that the
authoritative DNS server for its FQDN will be able to generate an
accurate set of Locator values if the DNS server receives DNS name
resolution request for its FQDN.
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RFC 6741 ILNP Engineering November 2012
Liu and Albitz [LA06] report that Secure Dynamic DNS Update has been
supported on the client-side for several years now in widely deployed
operating systems (e.g., MS Windows, Apple Mac OS X, UNIX, and Linux)
and also in DNS server software (e.g., BIND). Publicly available
product data sheets indicate that some other DNS server software
packages, such as that from Nominum, also support this capability.
For example, Microsoft Windows XP (and later versions), the freely
distributable BIND DNS software package (used in Apple Mac OS X and
in most UNIX systems), and the commercial Nominum DNS server all
implement support for Secure Dynamic DNS Update and are known to
interoperate [LA06]. There are credible reports that when a site
deploys Microsoft's Active Directory, the site (silently)
automatically deploys Secure Dynamic DNS Update [LA06]. So, many
sites have already deployed Secure Dynamic DNS Update even though
they are not actively using it (and might not be aware they have
already deployed that protocol) [LA06].
So DNS update via Secure Dynamic DNS Update is not only standards-
based, but also readily available in widely deployed systems today.
8.2. New DNS RR Types
As part of this proposal, additional DNS resource records have been
proposed in a separate document [RFC 6742]. These new records are
summarised in Table 6.1.
new DNS RR type | Purpose
-----------------+------------------------------------------------
NID | store the value of a Node Identifier
L32 | store the value of a 32-bit Locator for ILNPv4
L64 | store the value of a 64-bit Locator for ILNPv6
LP | points to a (several) L32 and/or L64 record(s)
-----------------+------------------------------------------------
Table 6.1. Summary of new DNS RR Types for ILNP
With this proposal, mobile or multihomed nodes and sites are expected
to use the existing "Secure Dynamic DNS Update" protocol to keep
their Node Identifier (NID) and Locator (L32 and/or L43) records
correct in their authoritative DNS server(s) [RFC 3007] [RFC 6742].
Reverse DNS lookups, to find a node's FQDN from the combination of a
Locator and related Identifier value, can be performed as at present.
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RFC 6741 ILNP Engineering November 2012
8.3. DNS TTL Values for ILNP RRS Types
Existing DNS specifications require that DNS clients and DNS
resolvers honour the TTL values provided by the DNS servers. In the
context of this proposal, short DNS TTL values are assigned to
particular DNS records to ensure that the ubiquitous DNS caching
resolvers do not cache volatile values (e.g., Locator records of a
mobile node) and consequently return stale information to new
requestors.
The TTL values for L32 and L64 records may have to be relatively low
(perhaps a few seconds) in order to support mobility and multihoming.
Low TTL values may be of concern to administrators who might think
that this would reduce efficacy of DNS caching increase DNS load
significantly.
Previous research by others indicates that DNS caching is largely
ineffective, with the exception of NS records and the addresses of
DNS servers referred to by NS records [SBK02]. This means DNS
caching performance and DNS load will not be adversely affected by
assigning very short TTL values (down to zero) to the Locator records
of typical nodes for an edge site [BA11]. It also means that it is
preferable to deploy the DNS server function on nodes that have
longer DNS TTL values, rather than on nodes that have shorter DNS TTL
values.
LP records normally are stable and will have relatively long TTL
values, even if the L32 or L64 records they point to have values that
have relatively low TTL values.
Identifier values might be very long-lived (e.g., days) when they
have been generated from an IEEE MAC address on the system.
Identifier values might have a shorter lifetime (e.g., hours or
minutes) if they have been cryptographically generated [RFC 3972],
have been created by the IPv6 Privacy Extensions [RFC 4941], or
otherwise have the EUI-64 scope bit set to "local-scope". Note that
when ILNP is used, the cryptographic generation method described in
RFC 3972 is used only for the Identifier, omitting the Locator,
thereby preserving roaming capability. Note that a given ILNP
session normally will use a single Identifier value for the lifetime
of that ILNP session.
8.4. IP/ILNP Dual Operation and Transition
During a long transition period, a node that is ILNP-capable SHOULD
have not only NID and L32/L64 (or NID and LP) records present in its
authoritative DNS server but also SHOULD have A/AAAA records in the
DNS for the benefit of non-upgraded nodes. Then, when any CN
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RFC 6741 ILNP Engineering November 2012
performs an FQDN lookup for that node, it will receive the A/AAAA
with the appropriate NID, L32/L64 records, and/or LP records as
"additional data".
Existing DNS specifications require that a DNS resolver or DNS client
ignore unrecognised DNS record types. So, gratuitously appending NID
and Locator (i.e., L32, L64, or LP) records as "additional data" in
DNS responses to A/AAAA queries ought not to create any operational
issues. So, IP only nodes would use the A/AAAA RRs, but ILNP-capable
nodes would be able to use the NID, L32/L64 and/or LP records are
required.
There is nothing to prevent this capability being implemented
strictly inside a DNS server, whereby the DNS server synthesises a
set of A/AAAA records to advertise from the NID and Locator (i.e.,
L32, L64, or LP) values that the node has kept updated in that DNS
server. Indeed, such a capability may be desirable, reducing the
amount of manual configuration required for a site, and reducing the
potential for errors as the A/AAAA records would be automatically
generated.
9. IP Security for ILNP
The primary conceptual difference from ordinary IP security (IPsec)
is that ILNP IP Security omits all use of, and all reference to,
Locator values. This leads to several small, but important, changes
to IPsec when it is used with ILNP sessions.
9.1. IPsec Security Association Enhancements for ILNP
IPsec Security Associations for ILNP only include the Identifier
values for the endpoints, and omit the Locator values. As an
implementation detail, ILNP implementations MUST be able to
distinguish between different Security Associations with ILNP
correspondents (at different locations, with different ILNP Nonce
values in use) that happen to use the same Identifier values (e.g.,
due to an inadvertent Identifier collision when using identifier
values generated by using the IPv6 Privacy Addressing extension).
One possible way to distinguish between such different ILNP sessions
is to maintain a mapping between the IPsec Security Association
Database (SAD) entry and the corresponding ILCC entry.
Consistent with this enhancement to the definition of an IPsec
Security Association, when processing received IPsec packets
associated with an ILNP session, ILNP implementations ignore the
Locator bits of the received packet and only consider the Identifier
bits. This means, for example, that if an ILNP correspondent node
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RFC 6741 ILNP Engineering November 2012
moves to a different subnetwork, and thus is using a different Source
Locator in the header of its ILNP IPsec packets, the ILNP session
will continue to work and will continue to be secure.
Since implementations of ILNP are also required to support IP,
implementers need to ensure that ILNP IPsec Security Associations can
be distinguished from ordinary IPsec Security Associations. The
details of this are left to the implementer. As an example, one
possible implementation strategy would be to retain a single IPsec
Security Association Database (SAD), but add an internal flag bit to
each entry of that IPsec SAD to indicate whether ILNP is in use for
that particular IPsec Security Association.
9.2. IP Authentication Header Enhancements for ILNP
Similarly, for an ILNP session using IPsec, the IPsec Authentication
Header (AH) only includes the Identifier values for the endpoints in
its authentication calculations, and it omits the Source Locator and
Destination Locator fields from its authentication calculations.
This enables IPsec AH to work well even when used with ILNP localised
numbering [RFC 6748] or other situations where a Locator value might
change while the packet travels from origin to destination.
9.3. Key Management Considerations
In order to distinguish at the network-layer between multiple ILNP
nodes that happen to be using the same Node Identifier values (e.g.,
because the identifier values were generated using the IPv6 Privacy
Addressing method), key management packets being used to set up an
ILNP IPsec session MUST include the ILNP Nonce Option.
Similarly, key management protocols used with IPsec are enhanced to
deprecate use of IP Addresses as identifiers and to substitute the
use of the new Node Identifier values for that purpose. This results
in an ILNP IPsec Security Association that is independent of the
Locator values that might be used.
For ILNPv6 implementations, the ILNP Node Identifier (64-bits) is
smaller than the IPv6 Address (128-bits). So support for ILNPv6
IPsec is accomplished by zeroing the upper-64 bits of the IPv6
Address fields in the application-layer key management protocol,
while retaining the Node Identifier value in the lower-64 bits of the
application-layer key management protocol.
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RFC 6741 ILNP Engineering November 2012
For ILNPv4 implementations, enhancements to the key management
protocol likely will be needed, because existing key management
protocols rely on 32-bit IPv4 addresses, while ILNP Node Identifiers
are 64-bits. Such enhancements are beyond the scope of this
specification.
10. Backwards Compatibility and Incremental Deployment
Experience with IPv6 deployment over the past many years has shown
that it is important for any new network protocol to provide
backwards compatibility with the deployed IP base and should be
incrementally deployable, ideally requiring modification of only
those nodes that wish to use ILNP and not requiring the modification
of nodes that do not intend to use ILNP. The two instances of ILNP,
ILNPv4 and ILNPv6, are intended to be, respectively, backwards
compatible with, and incrementally deployable on, the existing IPv4
and IPv6 installed bases. Indeed, ILNPv4 and ILNPv6 can each be
seen, from an engineering viewpoint, as supersets of the IPv4 and
IPv6, respectively.
However, in some cases, ILNP introduces functions that supersede
equivalent functions available in IP. For example, ILNP has a
mobility model, and so it does not need to use the models for Mobile
IPv4 or Mobile IPv6.
As ILNP changes, the use of end-to-end namespaces, for the most part,
it is only end-systems that need to be modified. However, in order
to leverage existing engineering (e.g., existing protocols), in some
cases, there is a compromise, and these are highlighted in this
section.
10.1. Priorities in the Design of ILNPv6 and ILNPv4
In the engineering design of ILNPv6 and ILNPv4, we have used the
following priorities. In some ways, this choice is arbitrary, and it
may be equally valid to "invert" these priorities for a different
architectural and engineering design.
1. Infrastructure
As much of the deployed IP network infrastructure should be used
without change. That is, routers and switches should require minimal
or zero modifications in order to run ILNP. As much as possible of
the existing installed base of core protocols should be reused.
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RFC 6741 ILNP Engineering November 2012
2. Core protocols
As much of the deployed network control protocols, such as routing,
should be used without change. That is, existing routing protocols
and switch configuration should require minimal or zero modifications
in order to run ILNP.
3. Scope of end-system changes
Any nodes that do not need to run ILNP should not need to be
upgraded. It should be possible to have a site network that has a
mix of IP-only and ILNP-capable nodes without any changes required to
the IP-only nodes.
4. Applications
There should be minimal impact on applications, even though ILNP
requires end-to-end protocols to be upgraded. Indeed, for those
applications that are "well behaved" (e.g., do not use IP Address
values directly for application state or application configuration),
there should be little or no effort required in enabling them to
operate over ILNP.
Each of these items is discussed in its own section below.
10.2. Infrastructure
ILNP is designed to be deployed on existing infrastructure. No new
infrastructure is required to run ILNP as it will be implemented as a
software upgrade impacting only end-to-end protocols. Existing
routing protocols can be reused: no new routing protocols are
required. This means that network operators and service providers do
not need to learn about, test, and deploy new protocols, or change
the structure of their network in order for ILNP to be deployed.
Exceptionally, edge routers supporting ILNPv4 hosts will need to
support an enhanced version of ARP.
10.3. Core Protocols
Existing routing and other control protocols should not need to
change in devices such as switches and routers. We believe this to
be true for ILNPv6. However, for ILNPv4, we believe that ARP will
need to be enhanced in edge routers (or Layer 3 switches) that
support ILNPv4 hosts. Backbone and transit routers still ought not
require changes for either ILNPv4 or ILNPv6.
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RFC 6741 ILNP Engineering November 2012
For both ILNPv4 and ILNPv6, the basic packet format for packets
reuses that format that is seen by routers for IPv4 and IPv6,
respectively. Specifically, as the ILNP Locator value is always a
routing prefix (either IPv4 or IPv6), routing protocols should work
unchanged.
Both ILNPv4 and ILNPv6 introduce new header options (e.g., Nonce
Option messages) and ICMP messages (e.g., Locator Update messages)
that are used to enable end-to-end signalling. For packet
forwarding, depending on the forwarding policies used by some
providers or site border routers, there may need to be modifications
to those policies to allow the new header options and new ICMP
messages to be forwarded. However, as the header options and new
ICMP messages are end-to-end, such modifications are likely to be in
configuration files (or firewall policy on edge routers), as core
routers do NOT need to parse and act upon the information contained
in the header options or ICMP messages.
10.4. Scope of End-System Changes
Only end-systems that need to use ILNP need to be updated in order
for ILNP to be used at a site.
There are three exceptions to this statement as follows:
a) ILNPv4 ARP: as the Identifier value for IPv4 cannot fit into the
normal 20-byte IPv4 packet header (a header extension is used),
ARP must be modified. This only impacts end-systems that use
ILNPv4 and those switches or site border routers that are the
first hop from an ILNPv4 node. For ILNPv6, as the I and L values
fit into the existing basic IPv6 packet, IPv6 Neighbour Discovery
can operate without modification.
b) Use of IP NAT: Where IP NAT or NAPT is in use for a site, existing
NAT/NAPT device will rewrite address fields in ILNPv4 packets or
ILNPv6 packets. To avoid this, the NAT should either (i) be
configured to allow the pass-through of packets originating from
ILNP-capable nodes (e.g., by filtering on source address fields in
the IP header); or (ii) should be enhanced to recognise ILNPv4 or
ILNPv6 packets (e.g., by looking for the ILNP Nonce Option).
c) Site Border Routers (SBRs) in ILNP Advanced Deployment scenarios:
There are options to use an ILNP-capable Site Border Router (SBR)
as described in another document [RFC 6748]. In such scenarios,
the SBR(s) need to be ILNP-capable.
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Other than these exceptions, it is entirely possible to have a site
that uses a mix of IP and ILNP nodes and requires no changes to nodes
other than the nodes that wish to use ILNP. For example, if a user
on a site wishes to have his laptop use ILNPv6, only that laptop
would need to have an upgraded stack: no other devices (end-systems,
Layer 2 switches or routers) at that site would need to be upgraded.
10.5. Applications
As noted, in the Architecture Description [RFC 6740], those
applications that do not use IP Address values in application state
or configuration data are considered to be "well behaved".
Applications that work today through a NAT or Network Address Port
Translation (NAPT) device without application-specific support are
also considered "well behaved". Such applications might use DNS
FQDNs or application-specific name spaces. (Note Well: application-
specific name spaces should not be derived from IP Address values.)
For well-behaved applications, replacing IP with ILNP should have no
impact. That is, well-behaved applications should work unmodified
over ILNP.
Those applications that directly use IP Address values in application
state or configuration will need to be modified for operation over
ILNP. Examples of such applications include the following:
- FTP: which uses IP Address values in the application-layer
protocol. In practice, use of Secure Copy (SCP) is growing, while
use of FTP is either flat or declining, in part due to the improved
security provided by SCP.
- SNMP: which uses IP Address values in MIB definitions, and values
derived from IP Address values in SNMP object names.
Further experimentation in this area is planned to validate these
details.
10.6. Interworking between IP and ILNP
A related topic is interworking: for example, how would an IPv6 node
communicate with an ILNPv6 node? Currently, we make the assumption
that ILNP nodes "drop down" to using IP when communicating with a
non-ILNP capable node, i.e., there is no interworking as such. In
the future, it may be beneficial to define interworking scenarios
that do not rely on having ILNP nodes fall back to IP, for example,
by the use of suitable protocol translation gateways or middleboxes.
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RFC 6741 ILNP Engineering November 2012
For now, a simplified summary of the process for interaction between
ILNP hosts and non-ILNP hosts is as follows:
a) For a host initiating communication using DNS, the resolution of
the FQDN for the remote host will return at least one NID record
and at least one of an L32 record (for ILNPv4) or an L64 record
(for ILNPv6). Then, the host knows that the remote host supports
ILNP.
b) When a host has I and L values for a remote host, the initial
packet to initiate communication MUST contain a Nonce Header
[RFC 6746] [RFC 6744] that indicates to the remote host that this
packet is attempting to set up an ILNP session.
c) When a receiving host sees a Nonce Header, if it DOES support ILNP
it will proceed to set up an ILNP session.
d) When a receiving host sees a Nonce Header, if it DOES NOT support
ILNP, it will reject the packet and this will be indicated to the
sender through an ICMP message [RFC 6743] [RFC 6745]. Upon
receiving the ICMP messages, the sender will re-initiate
communication using standard IPv4 or IPv6.
Many observers in the community expect IPv4 to remain in place for a
long time even though IPv6 has been available for over a decade.
With a similar anticipation, it is likely that in the future there
will be a mixed environment of both IP and ILNP hosts. Until there
is a better understanding of the deployment and usage scenarios that
will develop, it is not clear what interworking scenarios would be
useful to define and focus on between IP and ILNP.
11. Security Considerations
There are numerous security considerations for ILNP from an
engineering viewpoint. Overall, ILNP and its capabilities are no
less secure than IP and equivalent IP capabilities. In some cases,
ILNP has the potential to be more secure, or offer security
capability in a more harmonised manner, for example, with ILNP's use
of IPsec in conjunction with multihoming and mobility. [RFC 6740]
describes several security considerations that apply to ILNP and is
included here by reference.
ILNP offers an enhanced version of IP security (IPsec). The details
of IP Security for ILNP were described separately above. All ILNP
implementations MUST support the use of the IP Authentication Header
(AH) for ILNP and also the IP Encapsulating Security Payload (ESP)
for ILNP, but deployment and use of IPsec for ILNP remains a matter
for local operational security policy.
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RFC 6741 ILNP Engineering November 2012
11.1. Authenticating ICMP Messages
Separate documents propose a new IPv4 Option [RFC 6746] and a new IPv6
Destination Option [RFC 6744]. Each of these options can be used to
carry an ILNP Nonce value end-to-end between communicating nodes.
That nonce provides protection against off-path attacks on an ILNP
session. These ILNP Nonce Options are used ONLY for ILNP and not for
IP. The nonce values are exchanged in the initial packets of an ILNP
session by including them in those initial/handshake packets.
ALL ICMP Locator Update messages MUST include an ILNP Nonce Option
and MUST include the correct ILNP Nonce value for the claimed sender
and intended recipient of that ICMP Locator Update message. There
are no exceptions to this rule. ICMP Locator Update messages MAY be
protected by IPsec, but they still MUST include an ILNP Nonce Option
and the ILNP Nonce Option still MUST include the correct ILNP Nonce
value.
When a node has an active ILNP session, and that node changes its
Locator set, it SHOULD include the appropriate ILNP Nonce Option in
the first few data packets sent using a new Locator value so that the
recipient can validate the received data packets as valid (despite
having an unexpected Source Locator value).
Any ILNP Locator Update messages received without an ILNP Nonce
Option MUST be discarded as forgeries.
Any ILNP Locator Update messages received with an ILNP Nonce Option,
but that do NOT have the correct ILNP Nonce value inside the ILNP
Nonce Option, MUST be discarded as forgeries.
When the claimed sender of an ICMP message is known to be a current
ILNP correspondent of the recipient (e.g., has a valid, non-expired,
ILCC entry), then any ICMP error messages from that claimed sender
MUST include the ILNP Nonce Option and MUST include the correct ILNP
Nonce value (i.e., correct for that sender recipient pair) in that
ILNP Nonce Option.
When the claimed sender of an ICMP error message is known to be a
current ILNP correspondent of the recipient (e.g., has a valid, non-
expired, ILCC entry), then any ICMP error messages from that claimed
sender that are received without an ILNP Nonce Option MUST be
discarded as forgeries.
When the claimed sender of an ICMP error message is known to be a
current ILNP correspondent of the recipient (e.g., has a valid, non-
expired, ILCC entry), then any ICMP error messages from that claimed
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RFC 6741 ILNP Engineering November 2012
sender that contain an ILNP Nonce Option, but that do NOT have the
correct ILNP Nonce value inside the ILNP Nonce Option, MUST be
discarded as forgeries.
ICMP messages (not including ICMP Locator Update messages) with a
claimed sender that is NOT known to be a current ILNP correspondent
of the recipient (e.g., does not have a valid, non-expired, ILCC
entry) MAY include the ILNP Nonce Option, but, in this case, the ILNP
Nonce Option is ignored by the recipient upon receipt, since the
recipient has no way to authenticate the received ILNP Nonce value.
Received ICMP messages (not including ICMP Locator Update messages)
with a claimed sender that is NOT known to be a current ILNP
correspondent of the recipient (e.g., does not have a valid, non-
expired, ILCC entry) do NOT require the ILNP Nonce Option because the
security risks are no different than for deployed IPv4 and IPv6 --
provided that the received ICMP message is not an ICMP Locator Update
message. Such ICMP messages (e.g., Destination Unreachable, Packet
Too Big) might legitimately originate in an intermediate system along
the path of an ILNP session. That intermediate system might not be
ILNP capable. Even if ILNP capable itself, that intermediate system
might not know which of the packets it forwards are part of ILNP
sessions.
When ILNP is in use, IP Security for ILNP also MAY be used to protect
stronger protections for ICMP packets associated with an ILNP
session. Even in this case, the ILNP Nonce Option also MUST be
present and MUST contain the correct ILNP Nonce value. This
simplifies packet processing and enables rapid discard of any forged
packets from an off-path attacker that lack either the ILNP Nonce
Option or the correct ILNP Nonce value -- without requiring
computationally expensive IPsec processing. Received ICMP messages
that are protected by ILNP IP Security, but fail the recipient's
IPsec checks, MUST be dropped as forgeries. If a deployment chooses
to use ILNP IPsec ESP to protect its ICMP messages and is NOT also
using ILNP IPsec AH with those messages, then the ILNP Nonce Option
MUST be placed in the ILNP packet after the ILNP IPsec ESP header,
rather than before the ILNP IPsec ESP header, to ensure that the
Nonce Option is protected in transit.
Receipt of any ICMP message that is dropped or discarded as a forgery
SHOULD cause the details of the received forged ICMP packet (e.g.,
Source and Destination Locators / Source and Destination Identifiers
/ Source and Destination IP Addresses, ICMP message type, receiving
interface, receive date, receive time) to be logged in the receiving
system's security logs. Implementations MAY rate-limit such logging
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RFC 6741 ILNP Engineering November 2012
in order to reduce operational risk of denial-of-service attacks on
the system logging functions. The details of system logging are
implementation specific.
11.2. Forged Identifier Attacks
The ILNP Communication Cache (ILCC) contains two unidirectional nonce
values (one used in control messages sent by this node, a different
one used to authenticate messages from the other node) for each
active or recent ILNP session. The ILCC also contains the currently
valid set of Locators and set of Identifiers for each correspondent
node.
If a received ILNP packet contains valid Identifier values and a
valid Destination Locator, but contains a Source Locator value that
is not present in the ILCC, the packet MUST be dropped as an invalid
packet and a security event SHOULD be logged, UNLESS the packet also
contains a Nonce Destination Option with the correct value used for
packets from the node with that Source Identifier to this node. This
prevents an off-path attacker from stealing an existing ILNP session.
12. Privacy Considerations
There are no additional privacy issues created by ILNP compared to
IP. Please see Section 10 of [RFC 6740] for more detailed discussion
of Privacy Considerations.
ILNPv6 supports use of the IPv6 Privacy Extensions for Stateless
Address Autoconfiguration in IPv6 [RFC 4941] to enable identity
privacy (see also Section 2).
Location Privacy can be provided by locator rewriting techniques as
described in Section 7 of [RFC 6748].
A description of various possibilities for obtaining both identity
privacy and location privacy with ILNP can be found in [BAK11].
13. Operational Considerations
This section covers various operational considerations relating to
ILNP, including potential session liveness and reachability
considerations and Key Management considerations. Again, the
situation is similar to IP, but it is useful to explain the issues in
relation to ILNP nevertheless.
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RFC 6741 ILNP Engineering November 2012
13.1. Session Liveness and Reachability
For bidirectional flows, such as a TCP/ILNP session, each node knows
whether the current path in use is working by the reception of data
packets, acknowledgements, or both. Therefore, as with TCP/IP,
TCP/ILNP does not need special path probes. UDP/ILNP sessions with
acknowledgements work similarly and do not need special path probes.
In the deployed Internet, the sending node for a UDP/IP session
without acknowledgements does not know for certain that all packets
are received by the intended receiving node. Such UDP/ILNP sessions
have the same properties as UDP/IP sessions in this respect. The
receiver(s) of such an UDP/ILNP session SHOULD send a gratuitous IP
packet containing an ILNP Nonce Option to the sender, in order to
enable the receiver to subsequently send ICMP Locator Updates if
appropriate [RFC 6744]. In this case, UDP/ILNP sessions fare better
than UDP/IP sessions, still without using network path probes.
A mobile (or multihomed) node may change its connectivity more
quickly than DNS can be updated. This situation is unlikely,
particularly given the widespread use of link-layer mobility
mechanisms (e.g., GSM, IEEE 802 bridging) in combination with
network-layer mobility. However, the situation is equivalent to the
situation where a traditional IP node is moving faster than the
Mobile IPv4 or Mobile IPv6 agents/servers can be updated with the
mobile node's new location. So the issue is not new in any way to
ILNP. In all cases, Mobile IPv4 and Mobile IPv6 and ILNP, a node
moving that quickly might be temporarily unreachable until it remains
at a given network-layer location (e.g., IP subnetwork, ILNP Locator
value) long enough for the location update mechanisms (for Mobile
IPv4, for Mobile IPv6, or ILNP) to catch up.
Another potential issue for IP is what is sometimes called "Path
Liveness" or, in the case of ILNP, "Locator Liveness". This refers
to the question of whether an IP packet with a particular destination
Locator value will be able to reach the intended destination network
or not, given that some otherwise valid paths might be unusable by
the sending node (e.g., due to security policy or other
administrative choice). In fact, this issue has existed in the IPv4
Internet for decades.
For example, an IPv4 server might have multiple valid IP Addresses,
each advertised to the world via a DNS A record. However, at a given
moment in time, it is possible that a given sending node might not be
able to use a given (otherwise valid) destination IPv4 address in an
IP packet to reach that IPv4 server.
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RFC 6741 ILNP Engineering November 2012
Indeed, for ILNPv6, as the ILNP packet reuses the IPv6 packet header
and uses IPv6 routing prefixes as Locator values, such liveness
considerations are no worse than they are for IPv6 today. For
example, for IPv6, if a host, H, performs a DNS lookup for an FQDN
for remote host F, and receives a AAAA RR with IPv6 address F_A, this
does not mean necessarily that H can reach F on its F_A using its
current connectivity, i.e., an IPv6 path may not be available from H
to F at that point in time.
So we see that using an Identifier/Locator Split architecture does
not create this issue, nor does it make this issue worse than it is
with the deployed IPv4 Internet.
In ILNP, the same conceptual approach described in [RFC 5534] (Locator
Pair Exploration for SHIM6) can be reused. Alternatively, an ILNP
node can reuse the existing IPv4 methods for determining whether a
given path to the target destination is currently usable, for which
existing methods leverage transport-layer session state information
that the communicating end systems are already keeping for transport-
layer protocol reasons.
Lastly, it is important to note that the ICMP Locator Update
mechanism described in [RFC 6743] [RFC 6745] is a performance
optimisation, significantly shortening the network-layer handoff time
if/when a correspondent changes location. Architecturally, using
ICMP is no different from using UDP, of course.
13.2. Key Management Considerations
ILNP potentially has advantages over either form of Mobile IP with
respect to key management, given that ILNP is using Secure Dynamic
DNS Update -- which capability is much more widely available today in
deployed desktop and server environments (e.g., Microsoft Windows,
Mac OS X, Linux, other UNIX), as well as being widely available today
in deployed DNS server software (e.g., Microsoft and the freely
available BIND) and appliances [LA06], than the security enhancements
needed by either Mobile IPv4 or Mobile IPv6.
In the IESG, there is work in progress that addresses use of DNS to
support key management for entities having DNS Fully Qualified Domain
Names.
13.3. Point-to-Point Router Links
As a special case, for the operational reasons described in
[RFC 6164], ILNPv6 deployments MAY continue to use classic IPv6 with a
/127 routing prefix on router to router point-to-point links (e.g.,
SONET/SDH). Because an ILNPv6 packet and an IPv6 packet are
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RFC 6741 ILNP Engineering November 2012
indistinguishable for forwarding purposes to a transit router, this
should not create any operational difficulty for ILNPv6 traffic
travelling over such links.
14. Referrals and Application Programming Interfaces
This section is concerned with support for using existing ("legacy")
applications over ILNP, including both referrals and Application
Programming Interfaces (APIs).
ILNP does NOT require that well-behaved applications be modified to
use a new networking API, nor does it require applications be
modified to use extensions to an existing API. Existing well-behaved
IP applications should work over ILNP without modification using
existing networking APIs.
14.1. BSD Sockets APIs
The existing BSD Sockets API can continue to be used with ILNP
underneath the API. That API can be implemented in a manner that
hides the underlying protocol changes from the applications. For
example, the combination of a Locator and an Identifier can be used
with the API in the place of an IPv6 address.
So it is believed that existing IP address referrals can continue to
work properly in most cases. For a rapidly moving target node,
referrals might break in at least some cases. The potential for
referral breakage is necessarily dependent upon the specific
application and implementation being considered.
It is suggested, however, that a new, optional, more abstract, C
language API be created so that new applications may avoid delving
into low-level details of the underlying network protocols. Such an
API would be useful today, even with the existing IPv4 and IPv6
Internet, whether or not ILNP were ever widely deployed.
14.2. Java (and Other) APIs
Most existing Java APIs already use abstracted network programming
interfaces, for example, in the java.Net.URL class. Because these
APIs already hide the low-level network-protocol details from the
applications, the applications using these APIs (and the APIs
themselves) don't need any modification to work equally well with
IPv4, IPv6, ILNP, and probably also HIP.
Other programming languages, such as C++, python and ruby, also
provide higher-level APIs that abstract away from sockets, even
though sockets may be used beneath those APIs.
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RFC 6741 ILNP Engineering November 2012
14.3. Referrals in the Future
The approach proposed in [REFERRAL] appears to be very suitable for
use with ILNP, in addition to being suitable for use with the
deployed Internet. Protocols using that approach would not need
modification to have their referrals work well with IPv4, IPv6, ILNP,
and probably also other network protocols (e.g., HIP).
A sensible approach to referrals is to use FQDNs, as is commonly done
today with web URLs. This approach is highly portable across
different network protocols, even with both the IPv4 Internet or the
IPv6 Internet.
15. References
15.1. Normative References
[IEEE-EUI] IEEE, "Guidelines for 64-bit Global Identifier (EUI-64)
Registration Authority", <http://standards.ieee.org/
regauth/oui/tutorials/EUI64.html>, IEEE, Piscataway, NJ,
USA, March 1997.
[RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC 3007] Wellington, B., "Secure Domain Name System (DNS) Dynamic
Update", RFC 3007, November 2000.
[RFC 3177] IAB and IESG, "IAB/IESG Recommendations on IPv6 Address
Allocations to Sites", RFC 3177, September 2001.
[RFC 3587] Hinden, R., Deering, S., and E. Nordmark, "IPv6 Global
Unicast Address Format", RFC 3587, August 2003.
[RFC 4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
Address Autoconfiguration", RFC 4862, September 2007.
[RFC 4984] Meyer, D., Ed., Zhang, L., Ed., and K. Fall, Ed.,
"Report from the IAB Workshop on Routing and
Addressing", RFC 4984, September 2007.
[RFC 6177] Narten, T., Huston, G., and L. Roberts, "IPv6 Address
Assignment to End Sites", BCP 157, RFC 6177, March 2011.
[RFC 6740] Atkinson, R. and S. Bhatti, "Identifier-Locator Network
Protocol (ILNP) Architectural Description", RFC 6740,
November 2012.
Atkinson & Bhatti Experimental PAGE 35
RFC 6741 ILNP Engineering November 2012
[RFC 6742] Atkinson, R., Bhatti, S. and S. Rose, "DNS Resource
Records for the Identifier-Locator Network Protocol
(ILNP)", RFC 6742, November 2012.
[RFC 6743] Atkinson, R. and S. Bhatti, "ICMPv6 Locator Update
Message", RFC 6743, November 2012.
[RFC 6744] Atkinson, R. and S. Bhatti, "IPv6 Nonce Destination
Option for the Identifier-Locator Network Protocol for
IPv6 (ILNPv6)", RFC 6744, November 2012.
[RFC 6745] Atkinson, R. and S. Bhatti, "ICMP Locator Update
Message for the Identifier-Locator Network Protocol for
IPv4 (ILNPv4)", RFC 6745, November 2012.
[RFC 6746] Atkinson, R. and S.Bhatti, "IPv4 Options for the
Identifier-Locator Network Protocol (ILNP)", RFC 6746,
November 2012.
[RFC 6747] Atkinson, R. and S. Bhatti, "Address Resolution Protocol
(ARP) Extension for the Identifier-Locator Network
Protocol for IPv4 (ILNPv4)", RFC 6747, November 2012.
15.2. Informative References
[BA11] Bhatti, S. and R. Atkinson, "Reducing DNS Caching",
Proceedings of IEEE Global Internet Symposium (GI2011),
Shanghai, P.R. China, 15 April 2011.
[BAK11] Bhatti, S.N., Atkinson, R., and J. Klemets, "Integrating
Challenged Networks", Proceedings of IEEE Military
Communications Conference (MILCOM), IEEE, Baltimore, MD,
USA, Nov 2011.
[LA06] Liu, C. and P. Albitz, "DNS and Bind", 5th Edition,
O'Reilly & Associates, Sebastopol, CA, USA, 2006. ISBN
0-596-10057-4.
[PHG02] Pappas, A., Hailes, S. and R. Giaffreda, "Mobile Host
Location Tracking through DNS", Proceedings of IEEE
London Communications Symposium, IEEE, September 2002,
London, England, UK.
[SBK02] Snoeren, A., Balakrishnan, H. and M. Frans Kaashoek,
"Reconsidering Internet Mobility", Proceedings of 8th
Workshop on Hot Topics in Operating Systems, IEEE,
Elmau, Germany, May 2001.
Atkinson & Bhatti Experimental PAGE 36
RFC 6741 ILNP Engineering November 2012
[REFERRAL] Carpenter, B., Boucadair, M., Halpern, J., Jiang, S.,
and K. Moore, "A Generic Referral Object for Internet
Entities", Work in Progress, October 2009.
[RFC 826] 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.
[RFC 3972] Aura, T., "Cryptographically Generated Addresses (CGA)",
RFC 3972, March 2005.
[RFC 4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, February 2006.
[RFC 4581] Bagnulo, M. and J. Arkko, "Cryptographically Generated
Addresses (CGA) Extension Field Format", RFC 4581,
October 2006.
[RFC 4941] Narten, T., Draves, R., and S. Krishnan, "Privacy
Extensions for Stateless Address Autoconfiguration in
IPv6", RFC 4941, September 2007.
[RFC 4982] Bagnulo, M. and J. Arkko, "Support for Multiple Hash
Algorithms in Cryptographically Generated Addresses
(CGAs)", RFC 4982, July 2007.
[RFC 5534] Arkko, J. and I. van Beijnum, "Failure Detection and
Locator Pair Exploration Protocol for IPv6 Multihoming",
RFC 5534, June 2009.
[RFC 6164] Kohno, M., Nitzan, B., Bush, R., Matsuzaki, Y., Colitti,
L., and T. Narten, "Using 127-Bit IPv6 Prefixes on
Inter-Router Links", RFC 6164, April 2011.
[RFC 6748] Atkinson, R. and S. Bhatti, "Optional Advanced
Deployment Scenarios for the Identifier-Locator Network
Protocol (ILNP)", RFC 6748, November 2012.
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RFC 6741 ILNP Engineering November 2012
16. 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.
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
Atkinson & Bhatti Experimental PAGE 38
RFC TOTAL SIZE: 93512 bytes
PUBLICATION DATE: Saturday, November 10th, 2012
LEGAL RIGHTS: The IETF Trust (see BCP 78)
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