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Versions: 00 01 02 03 04 05 06 RFC 6740

Internet Draft                                             RJ Atkinson
draft-irtf-rrg-ilnp-arch-06.txt                             Consultant
Expires:  10 JAN 2013                                        SN Bhatti
Category: Experimental                                   U. St Andrews
                                                          10 July 2012

                     ILNP Architectural Description

Status of this Memo

   Distribution of this memo is unlimited.

   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
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   without warranty as described in the Simplified BSD License.

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   This document may contain material from IETF Documents or
   IETF Contributions published or made publicly available
   before November 10, 2008. The person(s) controlling the copyright
   in some of this material may not have granted the IETF Trust the
   right to allow modifications of such material outside the IETF
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   person(s) controlling the copyright in such materials, this
   document may not be modified outside the IETF Standards Process,
   and derivative works of it may not be created outside the IETF
   Standards Process, except to format it for publication as an RFC
   or to translate it into languages other than English.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups. Note that
   other groups may also distribute working documents as

   Internet-Drafts are draft documents valid for a maximum of six
   months and may be updated, replaced, or obsoleted by other

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   documents at any time. It is inappropriate to use Internet-Drafts
   as reference material or to cite them other than as "work in

   The list of current Internet-Drafts can be accessed at

   The list of Internet-Draft Shadow Directories can be accessed at

   This document is not on the IETF standards-track and does not
   specify any level of standard. This document merely provides
   information for the Internet community.

   This document is part of the ILNP document set, which has had
   extensive review within the IRTF Routing Research Group.  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


   This document provides an Architectural description and the
   Concept of Operations for the Identifier-Locator Network Protocol
   (ILNP), which is an experimental, evolutionary enhancement to
   IP. This is a product of the IRTF Routing RG.

Table of Contents

      1. Introduction .........................................?
      2. Architectural Overview................................?
      3. Architectural Changes Introduced by ILNP..............?
      4. ILNP Basic Connectivity...............................?
      5. Multi-Homing & Multi-Path Transport...................?
      6. Mobility..............................................?
      7. IP Security with ILNP.................................?
      8. Backwards Compatibility & Incremental Deployment......?
      9. Security Considerations ..............................?
     10. Privacy Considerations................................?
     11. IANA Considerations ..................................?
     12. References ...........................................?

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   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 multi-homing, node multi-homing,
   site/subnet mobility, node mobility) are also active concerns at
   present. Several different classes of evolution are being
   considered by the Internet research & 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.

   There has been substantial research relating to naming in the
   Internet through the years [IEN1] [IEN19] [IEN23] [IEN31]
   [IEN135] [RFC814] [RFC1498] [RFC2956]. Much of that research has
   indicated that binding the end-to-end transport-layer session
   state with a specific interface of a node at a specific location
   is undesirable, for example creating avoidable issues for
   mobility, multi-homing, end-to-end security. More recently,
   mindful of that important prior work, and starting well before
   the Routing RG was re-chartered to focus on inter-domain routing
   scalability, the authors have been examining enhancements to
   certain naming aspects of the Internet Architecture.  Separately,
   the Internet Architecture Board (IAB) recently considered
   the matter of Internet evolution, including naming [RFC6250].

   Our ideas and progress so far are embodied in the on-going
   definition of an experimental protocol which we call the
   Identifier Locator Network Protocol (ILNP).

   Links to relevant material are all available at:

   At the time of writing, the main body of peer-reviewed research
   from which the ideas in this and the accompanying documents draw
   is given in [LABH06], [ABH07a], [ABH07b], [ABH08a], [ABH08b],
   [ABH09a], [ABH09b], [RAB09], [ABH10], [RB10], [BA11], [BAK11],

   In this document, we:

     a) describe the architectural concepts behind ILNP and
        how various ILNP capabilities operate: this document

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        deliberately focuses on describing the key architectural
        changes that ILNP introduces and defers engineering
        discussion to separate documents.

   Other documents (listed below):

     b) show how functions based on ILNP would be realised on
        today's Internet by proposing an instance of ILNP based
        on IPv6, which we call ILNPv6 (there is also a document
        describing ILNPv4, which is how ILNP could be applied
        to IPv4).

     c) discuss salient operational and engineering issues impacting
        the deployment of ILNPv6 and the impact on the Internet.

     d) give architectural descriptions of optional advanced
        capabilities in advanced deployments based on the ILNP

1.1 Document Roadmap

   This document describes the architecture for the Identifier Locator
   Network Protocol (ILNP) including concept of operations. The authors
   recommend reading and understanding this document as the starting
   point to understanding ILNP.

   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 [ILNP-ENG]. 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) [ILNP-ENG] describes engineering and implementation
       considerations that are common to both ILNPv4 and ILNPv6.

    b) [ILNP-DNS] defines additional DNS resource records that
       support ILNP.

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    c) [ILNP-ICMPv6] 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.

    d) [ILNP-NONCEv6] 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) [ILNP-ICMPv4] 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) [ILNP-v4OPTS] 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) [ILNP-ARP] describes extensions to ARP for use with ILNPv4.

    h) [ILNP-ADV] 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 History

   In 1977, Internet researchers at University College London wrote
   the first Internet Experiment Note (IEN), which discussed issues
   with the interconnection of networks [IEN1].  This identified
   the inclusion of network-layer addresses in the transport-layer
   session state (e.g. TCP checksum) as a significant problem for
   mobile and multi-homed nodes and networks. It also proposed
   separation of identity from location as a better approach to take
   when designing the TCP/IP protocol suite.  Unfortunately, that
   separation did not occur, so the deployed IPv4 and IPv6 Internet
   entangles upper-layer protocols (e.g. TCP, UDP) with
   network-layer routing and topology information (e.g. IP
   addresses) [IEN1] [RFC768] [RFC793].

   The architectural concept behind ILNP derives from a June 1994
   note by Bob Smart to the IETF SIPP WG mailing list [SIPP94]. In
   January 1995, Dave Clark sent a similar note to the IETF IPng WG
   mailing list, suggesting that the IPv6 address be split into

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   separate Identifier and Locator fields [IPng95].

   Afterwards, Mike O'Dell pursued this concept in Internet-Drafts
   describing "8+8" or "GSE" [8+8] [GSE]. More recently, the IRTF
   Namespace Research Group (NSRG) studied this matter around the
   turn of the century. Unusually for an IRTF RG, the NSRG operated
   on the principle that unanimity was required for the NSRG to make
   a recommendation. Atkinson was a member of the IRTF NSRG. At
   least one other protocol, the Host Identity Protocol (HIP), also
   derives in part from the IRTF NSRG studies (and related
   antecedent work). This current proposal differs from O'Dell's
   work in various ways, notably in that it does not require
   deployment or use of Locator rewriting.

   The key idea proposed for ILNP is to directly and specifically
   change the overloaded semantics of the IP address. The Internet
   community has indicated explicitly, several times, that this use
   of overloaded semantics is a significant problem with the use of
   the Internet protocol today [RFC1498] [RFC2101] [RFC2956]

   While the research community has made a number of proposals that
   could provide solutions, so far there has been little progress on
   changing the status quo.

1.3 Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in RFC 2119 [RFC2119].


   ILNP takes a different approach to naming of communication
   objects within the network stack. Two new data types are
   introduced which subsume the role of the IP address at the
   network and transport layers in the current IP architecture.

2.1 Identifiers and Locators

   ILNP explicitly replaces the use of IP addresses with two
   distinct name spaces, each having distinct and different

     a) Identifier: a non-topological name for uniquely identifying
        a node.

     b) Locator: a topologically-bound name for an IP subnetwork.

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   The use of these two new namespaces in comparison to IP is given
   in Table 1. The table shows where existing names are used for
   state information in end-systems or protocols.

            Layer     |          IP          |     ILNP
         Application  |  FQDN or IP address  |  FQDN
         Transport    |  IP address          |  Identifier
         Network      |  IP address          |  Locator
         Physical i/f |  IP address          |  MAC address
       FQDN = Fully Qualified Domain Name
       i/f = interface

       Table 1: Use of names for state information in various
       communication layers for IP and ILNP.

   As shown in Table 1, if an application uses a Fully-Qualified
   Domain Name at the application-layer, rather than an IP Address
   or other lower-layer identifier, then the application perceives
   no architectural difference between IP and ILNP.  We call such
   applications "well-behaved" with respect to naming as use of the
   FQDN at the application-layer is recommended in RFC1958
   [RFC1958]. Some other applications also avoid use of IP address
   information within the application-layer protocol; we also
   consider these applications to be "well-behaved". Any
   well-behaved application should be able to operate on ILNP
   without any changes. Note that application level use of IP
   addresses includes application-level configuration information,
   e.g. Apache Web Server (httpd) configuration files make extensive
   use of IP addresses as a form of identity.

   ILNP does not require applications to be rewritten to use a new
   Networking Application Programming Interface (API). So existing
   well-behaved IP-based applications should be able to work over
   ILNP as-is.

   In ILNP, transport-layer protocols use only an end-to-end,
   non-topological node Identifier in any transport-layer session
   state. It is important to note that the node Identifier names the
   node, not a specific interface of the node. In this way, it has
   different semantics and properties than either the IPv4 Address,
   the IPv6 Address, or the IPv6 Interface Identifier [RFC791]

   The use of the ILNP Identifier value within application-layer
   protocols is not recommended.  Instead, the use of either a
   Fully Qualified Domain Name (FQDN) or some different

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   topology-independent namespace is recommended.

   At the network-layer, Locator values, which have topological
   significance, are used for routing and forwarding of ILNP
   packets, but Locators are not used in upper-layer protocols.

   As well as the new namespaces, another significant difference in
   ILNP, as shown in Table 1, is that there is no binding of a
   routable name to an interface, or Sub-Network Point of Attachment
   (SNPA), as there is in IP. The existence of such a binding in IP
   effectively binds transport protocol flows to a specific, single
   interface on a node. Also, applications that include IP addresses
   in their application-layer session state effectively bind to a
   specific, single interface on a node. [RFC2460] [RFC3484].

   In ILNP, dynamic bindings exist between Identifier values and
   associated Locator values, as well as between {Identifier,
   Locator} pairs and (physical or logical) interfaces on the node.

   This change enhances the Internet architecture by adding crisp
   and clear semantics for the Identifier and for the Locator,
   removing the overloaded semantics of the IP address [RFC1992]
   [RFC4984], by updating end system protocols, but without
   requiring any router or backbone changes.  In ILNP, the closest
   approximation to an IP address is an I-L Vector (I-LV),
   which is a given binding between an Identifier and Locator pair,
   written as [I, L].  I-LVs are discussed in more detail below.

   Where, today, IP packets have:

    - source IP address, destination IP address

   instead ILNP packets have:

    - source I-LV, destination I-LV

   However, it must be emphasised that the I-LV and the IP address
   are *not* equivalent.

   With these naming enhancements, we will improve the Internet
   architecture by adding explicit harmonised support for many
   functions, such as multi-homing, mobility and IP Security.

2.2  Deprecating IP Addresses

   ILNP places an explicit Locator and Identifier in the IP packet
   header, replacing the usual IP address. Locators are tied to the
   topology of the network. They may change frequently, as the node

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   or site changes its network connectivity. The node Identifier is
   normally much more static, and remains constant throughout the
   life of a given transport-layer session, and frequently much
   longer. However, there are various options for Identifier values,
   as will be discussed later [ILNP-ENG]. The way that I-LVs are
   encoded into packet headers is different for IPv4 and IPv6, as
   explained in [ILNP-ENG].

   Identifiers and Locators for hosts are advertised explicitly in
   DNS, through the use of new Resource Records (RRs). This is a
   logical and reasonable use of DNS, completely analogous to the
   capability that DNS provides today. At present, among other
   current uses, the DNS is used to map from an FQDN to a set of
   addresses. As ILNP replaces IP addresses with Identifiers and
   Locators, it is then clearly rational to use the DNS to map an
   FQDN to a set of Identifiers and a set of Locators for a node.

   The presence of ILNP Locators and Identifiers in the DNS for a
   DNS owner name is an indicator to correspondents that the
   correspondents can try to establish an ILNP-based transport-layer
   session with that DNS owner name.

   Specifically in response to [RFC4984], ILNP improves routing
   scalability by helping multi-homed sites operate effectively with
   provider-aggregatable (PA) address prefixes. Many multi-homed
   sites today request provider-independent (PI) address prefixes so
   they can provide session survivability despite the failure of one
   or more access links or Internet Service Providers (ISPs). ILNP
   provides this transport-layer session survivability by having a
   provider-independent Node Identifier (NID) value that is free of
   any topological semantics. This NID value can be bound
   dynamically to a provider-aggregatable Locator (L) value, the
   latter being a topological name i.e. a PA network prefix. By
   allowing correspondents to change arbitrarily among multiple PA
   Locator values, survivability is enabled as changes to the L
   values need not disrupt transport-layer sessions. In turn, this
   allows an ILNP multi-homed site to have both the full
   transport-layer and full network-layer session resilience that is
   today offered by PI addressing while using the equivalent of PA
   addressing.  In turn, this eliminates the current need to use
   globally visible PI routing prefixes for each multi-homed site.

2.3  Session Terminology

   To improve clarity and readability of the several ILNP
   specification documents, this section defines the terms
   "network-layer session" and "transport-layer session"
   both for IP-based networks and ILNP-based networks.

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   Today, network-layer IP sessions have 2 components:

    - Source IP address (A_S)
    - Destination IP address (A_D)

   For example, a tuple for an IP layer session would be:

     <IP: A_S, A_D>

   Instead network-layer ILNP sessions have 4 components:

    - Source Locator(s) (L_S)
    - Source Identifier(s) (I_S)
    - Destination Locator(s) (L_D)
    - Destination Identifier(s) (L_S)

   and a tuple for an ILNP session would be:

     <ILNP: I_S, L_S, I_D, L_D>

   The phrase "ILNP session" refers to an ILNP-based network-layer
   session, having the 4 components in the definition above.

   For engineering efficiency, multiple transport-layer sessions
   between a pair of ILNP correspondents normally share a single
   ILNP session (IL-V pairs and associated Nonce values). Also, for
   engineering convenience (and to cope with situation where different
   nodes, at different locations, might use the same I values), in the
   specific implementation of ILNPv6 and ILNPv4, we define the use of
   nonce values:

    - Source-to-destination Nonce value (N_S)
    - Destination-to-source Nonce value (N_D)

   These are explained in more detail in [ILNP-ENG], with
   [ILNP-NONCEv6] for ILNPv6 and [ILNP-V4OPTS] for ILNPv4.

   Today, transport-layer sessions using IP include these
   5 components:
    - Source IP address (A_S)
    - Destination IP address (A_D)
    - Transport-layer protocol (e.g. UDP, TCP, SCTP)
    - Source transport-layer port number (P_S)
    - Destination transport-layer port number (P_D)

   For example, a TCP tuple would be:

     <TCP: P_S, P_D, A_S, A_D>

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   Instead, transport-layer sessions using ILNP include these
   5 components:

    - Source Identifier (I_S)
    - Destination Identifier (I_D)
    - Transport-layer protocol (e.g. UDP, TCP, SCTP)
    - Source transport-layer port number (P_S)
    - Destination transport-layer port number (P_D)

   and an example tuple:

    <TCP: P_S, P_D, I_S, I_D>

2.4  Other Goals

   While we seek to make significant enhancements to the current
   Internet Architecture, we also wish to ensure that instantiations
   of ILNP are:

    a) Backwards compatible: implementations of ILNP should be able
       to work with existing IPv6 or IPv4 deployments, without
       requiring application changes.

    b) Incrementally deployable: to deploy an implementation of
       ILNP, changes to the network nodes should only be for those
       nodes that choose to use ILNP. The use of ILNP by some nodes
       does not require other nodes (that do not use ILNP) to be


   In this section, we describe the key changes that are made to the
   current Internet architecture. These key changes impact end
   systems, rather than routers.

3.1 Identifiers

   Identifiers, also called Node Identifiers (NIDs), are non-topological
   values that identify an ILNP node. A node might be a physical
   node or a virtual node. For example, a single physical device
   might contain multiple independent virtual nodes.  Alternately,
   a single virtual device might be composed from multiple physical
   devices. In the case of a Multi-Level Secure (MLS) system, each
   valid sensitivity label of that system might be a separate
   virtual node.

   A node MAY have multiple Identifier values associated with it,

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   which MAY be used concurrently.

   In normal operation when a node is responding to a received ILNP
   packet that creates a new network-layer session, the correct NID
   value to use for that network-layer session with that
   correspondent node will be learned from the received ILNP packet.

   In normal operation, when a node is initiating communication with
   a correspondent node, the correct I value to use for that session
   with that correspondent node will be learned either through the
   application-layer naming, through DNS name resolution, through
   some alternative name resolution system, or an application may be
   able to select different I values directly -- as Identifiers are
   visible above the network-layer via the transport protocol.

3.1.1  Node Identifiers are immutable during a session

   Once a Node Identifier (NID) value has been used to establish a
   transport-layer session, that Node Identifier value forms part of
   the end-to-end (invariant) transport-layer session state and so
   MUST remain fixed for the duration of that session. This means,
   for example, that throughout the duration of a given TCP session,
   the Source Node Identifier and Destination Node Identifier values
   will not change.

   In normal operation, a node will not change its set of valid
   Identifier values frequently. However, a node MAY change its set
   of valid Identifier values over time, for example in an effort to
   provide identity obfuscation, while remaining subject to the
   architectural rule of the preceding paragraph.  When a node
   has more than one Node Identifier value concurrently, the node
   might have multiple concurrent ILNP sessions with some
   correspondent node, in which case Node Identifier values will
   differ between the different concurrent ILNP sessions.

3.1.2  Syntax

   ILNP Identifiers have the same syntax as IPv6 Interface
   Identifiers [RFC4291], based on the EUI-64 format [IEEE-EUI],
   which helps with backwards compatibility.  There is no semantic
   equivalent to an ILNP Identifier in IPv4 or IPv6 today.

   The Modified EUI-64 syntax used by both ILNP Identifiers and IPv6
   Interface Identifiers contains a bit indicating whether the value
   has global-scope or local-scope [IEEE-EUI] [RFC4219].  ILNP
   Identifiers have either global-scope or local-scope. If they have
   global scope, they SHOULD be globally unique.

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   Regardless of whether an Identifier is global-scope or
   local-scope, an Identifier MUST be unique within the scope of a
   given Locator value to which it is bound for a given ILNP session or
   packet flow. As an example, with ILNPv6, the ordinary IPv6
   Neighbour Discovery (ND) processes ensure that this is true, just
   as ND ensures that no two IPv6 nodes on the same IPv6 subnetwork
   have the same IPv6 address at the same time.

   Both the IEEE EUI-64 specification and the Modified EUI-64 syntax
   also has a 'Group' bit [IEEE-EUI][RFC4291] For both ILNP node
   Identifiers and also IPv6 Interface Identifiers, this Group bit
   is set to 0.

3.1.3  Semantics

   Unicast ILNP Identifier values name the node, rather than naming
   a specific interface on that node. So ILNP Identifiers have
   different semantics than IPv6 Interface Identifiers.

3.2 Locators

   Locators are topologically-significant names, analogous to
   (sub)network routing prefixes. The Locator names the IP
   subnetwork that a node is connected to. ILNP neither prohibits
   nor mandates in-transit modification of Locator values.

   A host MAY have several Locators at the same time, for example
   if it has a single network interface connected to multiple
   subnetworks (e.g.  VLAN deployments on wired Ethernet), or has
   multiple interfaces each on a different subnetwork. Locator
   values normally have Locator Precedence Indicator (LPI) values
   associated with them. These LPIs indicate that a specific Locator
   value has higher or lower precedence for use at a given
   time. Local LPI values may be changed through local policy or via
   management interfaces. Remote LPI values are normally learned
   from the DNS, but the local copy of a remote LPI value might be
   modified by local policy relating to preferred paths or prefixes.

   Locator values are used only at the network-layer. Locators are
   not used in end-to-end transport state. For example, Locators are
   not used in transport-layer session state or application-layer
   session state.  However, this does not preclude an end-system
   setting up local dynamic bindings for a single transport flow to
   multiple Locator values concurrently.

   The routing system only uses Locators, not Identifiers. For
   unicast traffic, ILNP uses longest-prefix match routing, just as

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   the IP Internet does.

   Section 4 below describes in more detail how Locators are used by
   the forwarding and routing packets from a sending node on an
   origin subnetwork to one or more receiving nodes on one or more
   destination subnetworks.

   A difference from earlier [GSE, 8+8] proposals is that, in normal
   operation, the originating host supplies both Source Locator and
   Destination Locator values in the packets it sends out.

   Section 4.2 describes packet forwarding in more detail, while
   Section 4.3 describes packet routing in more detail.

3.2.1  Locator Values are Dynamic

   The ILNP architecture recognises that Locator values are
   topologically significant, so the set of Locator values
   associated with a node normally will need to change when the
   node's connectivity to the Internet topology changes. For
   example, a mobile or multi-homed node is likely to have
   connectivity changes from time to time, along with the
   corresponding changes to the set of Locator values.

   When a node using a specific set of Locator values changes one
   or more of those Locator values, then the node (1) needs to
   update its local knowledge of its own Locator values, (2) needs
   to inform all active Correspondent Nodes (CNs) of those changes
   to its set of Locator values so that ILNP session continuity is
   maintained, and (3) if it expects incoming connections the node
   also needs to update its Locator related entries in the Domain
   Name System. [ILNP-ENG] describes the engineering and
   implementation details of this process.

3.2.2 Locator Updates

   As Locator values can be dynamic, and they could change for a
   node during an ILNP session, correspondents need to be notified
   when a Locator value for a node changes for any existing ILNP
   session.  To enable this, a node that sees its Locator values
   have changed MUST send a Locator Update (LU) message to its
   correspondent nodes.  The details of this procedure are discussed
   in other ILNP documents [ILNP-ENG, ILNP-ICMPv6, ILNP-ICMPv4].
   (The change in Locator values may also need to be notified to DNS
   but that is discussed elsewhere.)

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3.2.3  Syntax

   ILNP Locators have the same syntax as an IP unicast routing prefix.

3.2.4  Semantics

   ILNP unicast Locators have the same semantics as an IP unicast
   routing prefix, since they name a specific subnetwork.  ILNP
   neither prohibits nor requires in-transit modification of Locator

3.3 IP Address and Identifier-Locator Vector (I-LV)

   Historically, an IP Address has been considered to be an atomic
   datum, even though it is recognised that an IP address has an
   internal structure: the network prefix plus either the host ID
   (IPv4) or the interface identifier (IPv6). However, this internal
   structure has not been used in end-system protocols: instead all
   the bits of the IP address are used. (Additionally, in IPv4 the
   IPv4 sub-net mask uses bits from the host ID, a further confusion
   of the structure, even thought it is an extremely useful
   engineering mechanism.)

   In ILNP, the IP address is replaced by an "Identifier-Locator
   Vector" (I-LV). This consists of a pairing of an Identifier value
   and a Locator value for that packet, written as [I, L]. All ILNP
   packets have Source Identifier, Source Locator, Destination
   Identifier, and Destination Locator values. The I value of the
   I-LV is used by upper-layer protocols (e.g. TCP, UDP, SCTP), so
   needs to be immutable. Locators are not used by upper-layer
   protocols (e.g. TCP, UDP, SCTP). Instead, Locators are similar to
   IP routing prefixes, and are only used to name a specific

   While it is possible to say that an I-LV is an approximation
   to an IP address of today, it should be understood that
   an I-LV:

     a) is not an atomic datum, being a pairing of two data types,
        an Identifier and a Locator.

     b) has different semantics and properties to an IP address,
        as is described in this document.

   In our discussion, it will be convenient sometimes to refer to an

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   I-LV, but sometimes to refer only to an Identifier value, or only
   to a Locator value.

   ILNP packets always contain a source I-LV and a destination I-LV.

3.4 Notation

   In describing how capabilities are implemented in ILNP, we will
   consider the differences in end-systems state between IP and ILNP
   in order to highlight the architectural changes.

   We define a formal notation to represent the data contained in
   the transport-layer session state. We define:

      A = IP address
      I = Identifier
      L = Locator
      P = Transport-layer port number

   To differentiate the local and remote values for the above items,
   we also use suffixes, for example:

     _L = local
     _R = remote

   With IPv4 and IPv6 today, the invariant state at the
   transport-layer for TCP can be represented by the tagged tuple:

     <TCP: A_L, A_R, P_L, P_R>                               --- (1)

   Tag values that will be used are:

     IP   Internet Protocol
     ILNP Identifier Locator Network Protocol
     TCP  Transmission Control Protocol
     UDP  User Datagram Protocol

   So, for example, with IP, a UDP packet would have the
   tagged tuple:

     <UDP: A_L, A_R, P_L, P_R>                               --- (2)

   A TCP segment carried in an IP packet may be represented by the
   tagged tuple binding:

     <TCP: A_L, A_R, P_L, P_R><IP: A_L, A_R>                 --- (3)

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   and a UDP packet would have the tagged tuple binding:

     <UDP: A_L, A_R, P_L, P_R><IP: A_L, A_R>                 --- (4)

   In ILNP, the transport-layer state for TCP is:

     <TCP: I_L, I_R, P_L, P_R>                               --- (5)

   The binding for a TCP segment within an ILNP packet:

     <TCP: I_L, I_R, P_L, P_R><ILNP: L_L, L_R>               --- (6)

   When comparing tuple expressions (3) and (6), we see that for IP,
   any change to network addresses impacts the end-to-end state, but
   for ILNP, changes to Locator values do not impact end-to-end
   state, providing end-system session state invariance, a key
   feature of ILNP compared to IP as it is used in some situations
   today. ILNP adopts the end-to-end approach for its architecture
   [SRC84]. As noted previously, nodes MAY have more than one
   Locator concurrently and nodes MAY change their set of active
   Locator values as required.

   While these documents don't include SCTP examples, the same
   notation can be used, simply substituting the string SCTP for the
   string TCP or the string UDP in the above examples.

3.5  Transport-layer state and transport pseudo-headers

   In ILNP, protocols above the network-layer do not use the Locator
   values. Thus, the transport-layer uses only the I values for the
   transport-layer session state (e.g. TCP pseudo-header checksum,
   UDP pseudo-header checksum), as is shown, for example, in
   expression (6) above.

   Additionally, again from a practical perspective, while the I
   values are only used in protocols above the network-layer, it is
   convenient for them to be carried in network packets, so that the
   namespace for the I values can be used by any transport-layer
   protocols operating above the common network-layer.

3.6  Rationale for this document

   This document provides an architectural description of the core
   ILNP capabilities and functions. It is based around the use of
   example scenarios so that practical issues can be highlighted.

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   In some cases, illustrative suggestions and light
   discussion are presented with respect to engineering issues,
   but detailed discussion of engineering issues are deferred
   to other ILNP documents.

   The order of the examples presented below are intended
   to allow an incremental technical understanding of ILNP
   to be developed. There is no other reason for the ordering
   of the examples listed below.

   Many of the descriptions are based on the use of an example
   site network as shown in Figure 2.1.

         site                         . . . .      +----+
        network                      .       .-----+ CN |
        . . . .      +------+       .         .    +----+
       .       .     |      +------.           .
      .    D    .    |      |      .           .
      .         .----+ SBR  |      . Internet  .
      .  H      .    |      |      .           .
       .       .     |      +------.           .
        . . . .      +------+       .         .
                                     .       .
                                      . . . .

           CN  = Correspondent Node
            D  = Device
            H  = Host
          SBR  = Site Border Router

      Figure 2.1: A simple site network for ILNP examples.

   In some cases, hosts (H) or devices (D) act as end-systems
   within the site network, and communicate with (one or more)
   Correspondent Node (CN) instances that are beyond the site.

   Note that the Figure is illustrative and presents a logical
   view. For example, the CN may itself be on a site network,
   just like H or D.

   Also, for formulating examples, we assume ILNPv6 is in use,
   which has the same packet header format (as viewed by
   routers) as IPv6, and can be seen as a superset of IPv6

   For simplicity, we assume that name resolution is via the
   deployed DNS which has been updated to store DNS records
   for ILNP [ILNP-DNS].

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   Note that, from an engineering viewpoint, this does NOT mean
   that the DNS also has to be ILNP capable: existing IPv4 or
   IPv6 infrastructure can be used for DNS transport.

3.7 ILNP Multicasting

   Multicast forwarding and routing are unchanged, in order to avoid
   requiring changes in deployed IP routers and routing protocols.
   ILNPv4 multicasting is the same as IETF standards-track IPv4
   multicasting.  ILNPv6 multicasting is the same as IETF
   standards-track IPv6 multicasting.


   In this section, we describe basic packet forwarding and routing
   in ILNP. We highlight areas where it is similar to current IP,
   and also where it is different from current IP. We use
   examples in order to illustrate the intent and show the
   feasibility of the approach.

   For this section, in Figure 4.1, H is a fixed host in a simple
   site network, CN is a remote Correspondent Node outside the site,
   H and CN are ILNP-capable, while the Site Border Router (SBR)
   does not need to be ILNP-capable.

         site                         . . . .      +----+
        network                      .       .-----+ CN |
        . . . .      +------+       .         .    +----+
       .       .     |      +------.           .
      .         .    |      |      .           .
      .         .----+ SBR  |      . Internet  .
      .  H      .    |      |      .           .
       .       .     |      |      .           .
        . . . .      +------+       .         .
                                     .       .
                                      . . . .

           CN  = Correspondent Node
            H  = Host
          SBR  = Site Border Router

      Figure 4.1: A simple site network for ILNP examples.

4.1  Basic Local Configuration

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   This section uses the term "Address management", in recognition
   of the analogy with capabilities present in IP today. In this
   document, address management is about enabling hosts to attach to
   a subnetwork and enabling network-layer communication between and
   among hosts, also including:

    a) enabling identification of a node within a site.
    b) allowing basic routing/forwarding from a node acting as
       an end-system.

   If we consider Figure 4.1, imagine that host H has been connected
   to the site network. Administratively, it needs at least one I
   value and one L value in order to be able to communicate.

   Today, local administrative procedures allocate IP addresses,
   often using various protocol mechanisms (e.g. NetConf-based
   router configuration, DHCP for IPv4, DHCP for IPv6, IPv6 Router
   Advertisements). Similarly, local administrative procedures can
   allocate I and L values as required, e.g. I_H and L_H. This may
   be through manual configuration.

   Additionally, if it is expected or desired that H might have
   incoming communication requests, e.g. it is a server, then the
   values I_H and L_H can be added to the relevant name services
   (e.g. DNS, NIS/YP), so that FQDN lookups for H resolve to the
   appropriate DNS resource records (e.g. NID, L32, L64, and LP
   [ILNP-DNS]) for node H.

   From a network operations perspective, this whole process also
   can be automated. As an example, consider that in Figure 3.1 the
   Site Border Router (SBR) is an IPv6 capable router and is
   connected via link1 to an ISP that supports IPv6. SBR will have
   been allocated one (or more) IPv6 prefixes that it will multicast
   using IPv6 Routing Advertisements (RAs) into the site network,
   e.g. say prefix L_1. L_1 is actually a local IPv6 prefix (/64),
   which is formed from an address assignment by the upstream ISP,
   according to [RFC3177] or [RFC6177]. Host H will see these RAs,
   for example, on its local interface with name eth0, will be able
   to use that prefix as a Locator value, and will cache that
   Locator value locally.

   Also, node H can use the mechanism documented in either Section
   2.5.1 of [RFC4291], in [RFC3972] [RFC4581] [RFC4982], or in
   [RFC4941] in order to create a default I value, say I_H, just as
   an IPv6 host can.  For DNS, the I_H and L_1 values may be
   pre-configured in DNS by an administrator who already has
   knowledge of these, or added to DNS by H using Secure DNS Dynamic
   Update [RFC3007] to add or update the correct NID and L64 records

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   to DNS for the FQDN for H.

4.2  I-L Communication Cache

   For the purposes of explaining the concept of operations, we talk
   of a local I-L Communication Cache (ILCC). This is an engineering
   convenience and does not form part of the ILNP architecture,  but
   is used in our examples. More details on the ILCC can be found in
   [ILNP-ENG]. The ILCC contains information that is required for
   the operation of ILNP. This will include, amongst other things,
   the current set of valid Identifier and Locator values in use by
   a node, the bindings between them and the bindings between
   Locator values and interfaces.

4.3  Packet Forwarding

   When the SBR needs to send a packet to H, it uses local address
   resolution mechanisms to discover the bindings between interface
   addresses and currently active I-LVs for H. For our example of
   Figure 3.1, IPv6 Neighbour Discovery (ND) can be used without
   modification, as the I-LV for ILNPv6 occupies the same bits as
   the IPv6 address in the IPv6 header. For packets from H to SBR,
   the same basic mechanism applies, as long as SBR supports IPv6
   and even if it is not ILNPv6-capable, as IPv6 ND is used
   unmodified for ILNPv6.

   For Figure 3.1, assuming:

    - SBR advertises prefix L_1 locally, uses I value I_S, and has
      an Ethernet MAC address M_S on interface with local name sbr0

    - H uses I value I_H, and has an ethernet MAC address of M_H on
      the interface with local name eth0

   then H will have in its ILCC:

     [I_H, L_1]                                         --- (7a)
     L_1, eth0                                          --- (7b)

   After the IPv6 RA and ND mechanism has executed, the ILCC at H
   would contain, as well as (7a) and (7b), the following entry for

     [I_S ,L_1], M_S                                    --- (8)

   For ILNPv6, it does not matter that the SBR is not ILNPv6
   capable, as the I-LV [I_S, L_1] is physically equivalent to the

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   IPv6 address for the internal interface sbr0.

   At SBR, which is not ILNP-capable, there would be the following
   entries in its local cache and configuration:

      L_1:I_S                                           --- (9a)
      L_1, sbr0                                         --- (9b)

   Expression (9a) represents a valid IPv6 ND entry: in this case,
   the I_S value (which is 64 bits in ILNPv6) and the L_1 values
   are, effectively, concatenated and treated as if they were a
   single IPv6 address.  Expression (9b) binds transmissions for L_1
   to interface sbr0 (again, sbr0 is a local, implementation-
   specific name, and such a binding is possible with standard tools
   today, for example ifconfig(8)).

4.4  Packet Routing

   If we assume that host H is configured as in the previous
   section, it is now ready to send and receive ILNP packets.

   Let us assume that, for Figure 3.1, it wishes to contact the
   node CN, which has FQDN cn.example.com and is ILNP-capable.
   A DNS query by H for cn.example.com will result in NID and L64
   records for CN, with values I_CN and L_CN, respectively,
   being returned to H, and stored in its ILCC:

     [I_CN, L_CN]                                     --- (10)

   This will be considered active, as long as the TTL values for the
   DNS records are valid. If the TTL for an I or L value is zero,
   then the value is still useable but becomes stale as soon as it
   has been used once. However, it is more likely that the TTL value
   will be greater than zero [BA11] [SBK01].

   Once the CN's I value is known, the upper layer protocol, e.g.
   the transport protocol, can set up suitable transport-layer
   session state:

      <UDP: I_H, I_CN, P_H, P_CN>                     --- (11)

   For routing of ILNP packets, the destination L value in an ILNPv6
   packet header is semantically equivalent to a routing prefix.
   So, once a packet has been forwarded from a host to its first-hop
   router, only the destination L value needs to be used for getting
   the packet to the destination network. Once the packet has
   arrived at the router for the site network, local mechanisms and

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   packet forwarding mechanism, as described above in Section 4.3,
   allow the packet to be delivered to the host.

   For our example of Figure 4.1, H will send a UDP packet
   over ILNP as:

     <UDP: I_H, I_CN, P_H, P_CN><ILNP: L_1, L_CN>     --- (12a)

   and CN will send UDP packets to H as:

     <UDP: I_CN, I_H, P_CN, P_H><ILNP: L_CN, L_1>     --- (12b)

   The I value for H used in the transport-layer state (I_H in
   expression (12a)) selects the correct L value (L_1 in this case)
   from the bindings in the ILCC (expression (7a)), and that, in
   turn, selects the correct interface from the ILCC (expression
   (7b)), as described in Sec 4.2. This gets the packet to the first
   hop router, and beyond that, the ILNPv6 packet is treated as if
   it were an IPv6 packet.


   For multi-homing, there are three cases to consider:

     a) Host Multi-Homing (H-MH): a single host is, individually,
       connected to multiple upstream links, via separate routing
       paths, and those multiple paths are used by that host as it
       wishes. That is, use of multiple upstream links is managed
       by the single host itself.  For example, the host might have
       multiple valid Locator values on a single interface, with
       each Locator value being associated with a different
       upstream link (provider).

     b) Multi-Path Transport (MPT): This is similar to using
       ILNP's support for host multi-homing (i.e. H-MH),
       so we describe multi-path transport here. (Indeed,
       for ILNP, this can be considered a special case of H-MH.)

     c) Site Multi-Homing (S-MH): a site network is connected to
       multiple upstream links via separate routing paths, and hosts
       on the site are not necessarily aware of the multiple
       upstream paths. That is, the multiple upstream paths are
       managed, typically, through a site-border router, or via the

   Essentially, for ILNP, multi-homing is implemented by enabling:

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     a) multiple Locator values to be used simultaneously by a node

     b) dynamic, simultaneous binding between one (or more)
        Identifier value(s) and multiple Locator values

   With respect to the requirements for hosts [RFC1122], the multi-
   homing function provided by ILNP is very flexible. It is not
   useful to discuss ILNP multi-homing strictly within the confines
   of the exposition presented in Section 3.3.4 of [RFC1122], as
   that text is couched in terms of relationships between IP
   addresses and interfaces, which can be dynamic in ILNP. The
   closest relationship between ILNP multi-homing and [RFC1122]
   would be that certainly ILNP could support the notion of
   "Multiple Logical Networks", "Multiple Logical Hosts" and "Simple

5.1 Host Multi-Homing (H-MH)

   At present, host multi-homing is not common in the deployed
   Internet.  When TCP or UDP are in use with an IP-based
   network-layer session, host multi-homing cannot provide session
   resilience, because the transport protocol's pseudo-header
   checksum binds the transport-layer session to a single IP address
   of the multi-homed node, and hence to a single interface of that
   node. SCTP has a protocol-specific mechanism to support node
   multi-homing; SCTP can support session resilience both at present
   and also without change in the proposed approach [RFC5061].

   Host multi-homing in ILNP is supported directly in each host by
   ILNP.  The simplest explanation of H-MH for ILNP is that an
   ILNP-capable host can simultaneously use multiple Locator values,
   for example by having a binding between an I value and two
   different L values, e.g. the ILCC may contain the I-LVs:

     [I_1, L_1]                                       --- (14a)
     [I_1, L_2]                                       --- (14b)

   Additionally, a host may use several I values concurrently,
   e.g. the ILCC may contain the I-LVs:

     [I_1, L_1]                                       --- (15a)
     [I_1, L_2]                                       --- (15b)
     [I_2, L_2]                                       --- (15c)
     [I_3, L_1]                                       --- (15d)

   Architecturally, ILNP considers these all to be cases of
   multi-homing: the host is connected to more than one
   subnetwork, each subnetwork being named by a different

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   Locator value.

   In the cases above, the selection of which I-LV to use
   would be through local policy or through management
   mechanisms. Additionally, suitably modified transport-layer
   protocols, such as multi-path transport-layer protocol
   implementations, may make use of multiple I-LVs. Note that
   in such a case, the way in which multiple I-LVs are used
   would be under the control of the higher-layer protocol.

   Recall, however, that L values also have precedence - LPI
   values - and these LPI values can be used at the network-layer,
   or by a transport-layer protocol implementation, in order
   make use of L values in a specific manner.

   Note that, from a practical perspective, ILNP dynamically binds
   L values to interfaces on a node to indicate the SNPA for that
   L value, so the multi-homing is very flexible: a node could have
   a single interface and have multiple L values bound to that
   interface. For example, for expressions (14a) and (14b) if the
   end-system has a single interface with local name eth0, then the
   entries in the ILCC will be:

     L_1, eth0                                       --- (16a)
     L_2, eth0                                       --- (16b)

   and if we assume that for expressions (15a-c), the end-system
   has two interfaces, eth0 and eth1, then these ILCC entries
   are possible:

     L_1, eth0                                       --- (17a)
     L_2, eth1                                       --- (17b)

   Let us consider the network in Figure 5.1.

         site                         . . . .
        network                      .       .
        . . . .      +------+ L_1   .         .
       .       .     |      +------.           .
      .         .    |      |      .           .
      .         .----+ SBR  |      . Internet  .
      .         .    |      |      .           .
       .  H    .     |      +------.           .
        . . . .      +------+ L_2   .         .
                                     .       .
                                      . . . .

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         L_1 = global Locator value 1
         L_2 = global Locator value 2
         SBR = Site Border Router

     Figure 5.1: A simple multi-homing scenario for ILNP.

   We assume that H has a single interface, eth0. SBR will advertise
   L_1 and L_2 internally to the site. Host H will configure these
   as both reachable via its single interface, eth0, by using ILCC
   entries as in expressions (16a) and (16b). When packets from H
   that are to egress the site network reach SBR, it can make
   appropriate decisions on which link to use based on the source
   Locator value (which has been inserted by H), or based on other
   local policy.

   If, however, H has two interfaces, eth0 and eth1, then it can use
   ILCC entries as in expressions (17a) and (17b).

   Note that the values L_1 and L_2 do not need to be PI based
   Locator values, and can be taken from ISP-specific PA routing
   prefix allocations from the upstream ISPs providing the two

   Of course, this example is illustrative: many other
   configurations are also possible, but the fundamental mechanism
   remains the same, as described above.

   If any Locator values change then H will discover this when it
   sees new Locator values in RAs from SBR, and sees that L values
   that were previously used are no longer advertised. When this
   happens, H will:

     a) maintain existing active network-layer sessions: based on
        its current ILCC entries and active sessions, send Locator
        Update (LU) messages to CNs to notify them of the change of
        L values. (LU messages are synonymous to Mobile IPv6 Binding

     b) if required, update its relevant DNS entries with the new L
        value in the appropriate DNS records, to enable correct
        resolution for new incoming session requests.

   From an engineering view point, H also updates its ILCC data,
   removing the old L value(s) and replacing with new L value(s) as

   Depending on the nature of the physical change in connectivity
   that the L value change represents, this may disrupt upper-level

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   protocols, e.g.  a fibre cut. Dealing with such physical-level
   disruption is beyond the scope of ILNP. However, ILNP supports
   graceful changes in L values, and this is explained below in
   Section 6 in the discussion on mobility support.

5.2 Support for Multi-Path Transport Protocols (MPTs)

   ILNP supports deployment and use of multi-path transport
   protocols, such as the Multi-Path extensions to TCP (MP-TCP)
   being defined by the IETF TCPM Working Group. Specifically, ILNP
   will support the use of multiple paths as it allows a single I
   value to be bound to multiple L values - see Sec 5.1 and
   specifically expressions (15a) and (15b).

   Of course, there will be specific mechanisms for:
    - congestion control
    - signalling for connection/session management
    - path discovery and path management
    - engineering and implementation issues

   These transport-layer mechanisms fall outside the scope of ILNP
   and would be defined in the multi-path transport protocol

   As far as the ILNP architecture is concerned, the transport
   protocol connection is simply using multiple I-LVs, but with the
   same I value in each, and different L values, i.e. a multi-homed

5.3 Site multi-homing (S-MH)

   At present, site multi-homing is common in the deployed
   Internet. This is primarily achieved by advertising the site's
   routing prefix(es) to more than one upstream Internet service
   provider at a given time. In turn, this requires de-aggregation
   of routing prefixes within the inter-domain routing system. This
   increases the entropy of the inter-domain routing system
   (e.g. RIB/FIB size increases beyond the minimal RIB/FIB size that
   would be required to reach all sites).

   Site multi-homing, in its simplest form in ILNP, is an extension
   of the H-MH scenario described in Sec 5.1. If we consider Figure
   5.1 and assume that there are many hosts in the site network,
   each can choose to manage its own ILNP connectivity and whether
   or not multiple Locator values are used. This allows maximal
   control of connectivity for each host.

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   Of course, with ILNPv6, just as any IPv6 router is required to
   generate IPv6 Router Advertisement messages with the correct
   routing prefix information for the link the RA is advertised
   upon, thus also the SBR is required to generate RAs containing
   the correct Locator value(s) for the link that the RA is
   advertised upon. The correct values for these RA messages are
   typically configured by system administration, or might be passed
   down from the upstream provider.

   To avoid a DNS Update burst when a site or (sub)network changes
   location, a DNS record optimisation is possible by using the new
   LP record for ILNP. This would change the number of DNS Updates
   required from Order(Number of nodes within the site/subnetwork
   that moved) to Order(1) [ILNP-DNS].

5.3.1 A common multi-homing scenario - multiple SBRs

   The scenario of Fig 5.1 is an example to illustrate the
   architectural operation of multi-homing for ILNP. For site multi-
   homing, a scenario such as the one depicted in Figure 5.2 is also
   common. Here, there are two SBRs, each with its own global

         site                          . . . .
        network                       .       .
        . . . .      +-------+ L_1   .         .
       .       .     |       +------.           .
      .         .    |       |      .           .
     .           .---+ SBR_A |      .           .
     .           .   |       |      .           .
     .           .   |       |      .           .
     .           .   +-------+      .           .
     .           .       ^          .           .
     .           .       | CP       . Internet  .
     .           .       v          .           .
     .           .   +-------+ L_2  .           .
     .           .   |       +------.           .
     .           .   |       |      .           .
     .           .---+ SBR_B |      .           .
      .         .    |       |      .           .
       .       .     |       |      .           .
        . . . .      +-------+       .         .
                                      .       .
                                       . . . .

         CP     = coordination protocol
         L_1    = global Locator value 1

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         L_2    = global Locator value 2
         SBR_A  = Site Border Router A
         SBR_B  = Site Border Router P

     Figure 5.2: A dual-router multi-homing scenario for ILNP.

   The use of two physical routers provides an extra level of
   resilience compared to the scenario of Fig 5.1. The coordination
   protocol (CP) between the two routers keeps their actions in
   synchronisation according to whatever management policy is in
   place for the site network. Such capabilities are available today
   in products. Note that, logically, there is little difference
   between Fig 5.1 and Fig 5.2, but with two distinct routers in Fig
   5.2, the interaction using CP is required. Of course, it is also
   possible to have multiple interfaces in each router and more than
   two routers.

5.4  Multi-Homing Requirements for Site Border Routers

   For multi-homing, the SBR does NOT need to be ILNP-capable for
   Host Multi-Homing or Site Multi-Homing. This is true provided the
   multi-homing is left to individual hosts as described above. In
   this deployment approach, the SBR need only issue Routing
   Advertisements (RAs) that are correct with respect to its
   upstream connectivity; that is, the SBR properly advertises
   routing prefixes (Locator values) to the ILNP hosts.

   In such a scenario, when hosts in the site network see new
   Locator values, and see that a previous Locator value is no
   longer being advertised, those hosts can update their ILCCs,
   send Locator Updates to CNs, and change connectivity
   as required.


   ILNP supports mobility directly, rather than relying upon
   special-purpose mobility extensions as is the case both with IPv4
   [RFC-2002] and also with IPv6 [RFC6275].

   There are two different mobility cases to consider:

     a) Host Mobility: individual hosts may be mobile, moving across
        administrative boundaries or topological boundaries within
        an IP-based network, or across the Internet. Such hosts
        would need to independently manage their own mobility.

     b) Network (Site) Mobility: a whole site, i.e. one (or more) IP

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        subnetwork(s) may be mobile, moving across administrative
        boundaries or topological boundaries within an IP-based
        network, or across the Internet. The site as a whole needs
        to maintain consistency in connectivity.

   Essentially, for ILNP, mobility is implemented by enabling:

     a) Locator values to be changed dynamically by a node,
        including for active network-layer sessions.

     b) use of Locator Updates to allow active network-layer
        sessions to be maintained.

     c) for those hosts that expect incoming network-layer or
        transport-layer session requests (e.g., servers), updates
        to the relevant DNS entries for those hosts.

   It is possible that a device is both a mobile host and part of a
   mobile network, e.g. a smartphone in a mobile site network. This
   is supported in ILNP as the mechanism for mobile hosts and mobile
   networks are very similar and work in harmony.

   For mobility, there are two general features that must be

     a) Handover (or Hand-off): when a host changes its connectivity
        (e.g. it has a new SNPA as it moves to a new ILNP
        subnetwork), any active network-layer sessions for that host
        must be maintained with minimal disruption
        (i.e. transparently) to the upper layer protocols.

     b) Rendezvous: when a host that expects incoming network-layer
        or transport-layer session requests has new connectivity
        (e.g. it has a new SNPA as it moves to a new ILNP
        subnetwork), it needs to update its relevant DNS entries so
        that name resolution will provide the correct I and L values
        to remote nodes.

6.1 Mobility/multi-homing duality in ILNP

   Mobility and multi-homing present the same set of issues for
   ILNP.  Indeed, mobility and multi-homing form a duality: the set
   of Locators associated with a node or site changes. The reason
   for the change might be different for the case of mobility and
   multi-homing, but the effects on the network-layer session state
   and on correspondents is identical.

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   With ILNP, mobility and multi-homing are supported using a common
   set of mechanisms. In both cases, different Locator values are
   used to identify different IP subnetworks. Also, ILNP nodes that
   expect incoming network-layer or transport-layer session requests
   are assumed to have a Fully Qualified Domain Name (FQDN) stored
   in the Domain Name System (DNS), as is already done within the
   deployed Internet.  ILNP mobility normally relies upon the Secure
   Dynamic DNS Update standard for mobile nodes to update their
   location information in the DNS.  This approach of using DNS for
   rendezvous with mobile systems was proposed earlier by others

   Host Mobility considers individual hosts that are individually
   mobile, for example a mobile telephone carried by a person
   walking in a city.  Network (Site) Mobility considers a group of
   hosts within a local topology that move jointly and periodically
   change their uplinks to the rest of the Internet, for example a
   ship that has wired connections internally but one or more
   wireless uplinks to the rest of the Internet.

   For ILNP, Host Mobility is analogous to Host Multi-homing (H-MH)
   and Network Mobility is analogous to Site Multi-homing
   (S-MH). So, mobility and multi-homing capabilities can be used
   together, without conflict.

   6.2 Host Mobility

   With host mobility, each individual end-system manages its own
   connectivity through the use of Locator values. (This is very
   similar to the situation described for H-MH in Sec 5.1.)

   Let us consider the network in Figure 6.1.

         site                          . . . .
        network A                     .       .
        . . . .      +-------+ L_A   .         .
       .       .     |       +------.           .
      .         .    |       |      .           .
     .           .---+ SBR_A |      .           .
     .           .   |       |      .           .
     .  H(1)     .   |       |      .           .
     .           .   +-------+      .           .
      . . . . . .                   .           .
       .  H(2) .                    . Internet  .
      . . . . . .                   .           .
     .           .   +-------+ L_B  .           .
     .  H(3)     .   |       +------.           .
     .              .   |       |      .           .

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     .           .---+ SBR_B |      .           .
      .         .    |       |      .           .
       .       .     |       |      .           .
        . . . .      +-------+       .         .
         site                         .       .
        network B                      . . . .

         H(X) = host H at position X
         L_A  = global Locator value A
         L_B  = global Locator value B
         SBR  = Site Border Router

     Figure 6.1: A simple mobile host scenario for ILNP.

   A host, H is at position (1), hence H(1), in a site network
   A. This site network might be, for example, a single radio-cell
   under administrative domain A. We assume that the host will move
   into site network B, which might be a single radio-cell under
   administrative domain B. We also assume that the site networks
   have a region of overlap so that connectivity can be maintained,
   else, of course, the host will loose connectivity. Also, let us
   assume that the host already has ILNP connectivity in site
   network A.

   If site network A has connectivity via Locator value L_A, and H
   uses Identifier value I_H with a single interface ra0, then the
   host's ILCC will contain:

     [I_H, L_A]                                           --- (18a)
     L_A, ra0                                             --- (18b)

   Note the equivalence of expressions (18a) and (18b),
   respectively, with the expressions (15a) and (16a)
   for host multi-homing.

   The host now moves into the overlap region of site networks A and
   B, and has position (2), H(2) as indicated in Fig 6.1. As this
   region is now in site network B, as well as site network A, H
   should see RAs from SBR_B for L_B, as well as the RAs for L_A
   from SBR_A. The host can now start to use L_B for its
   connectivity. The host H must now:

     a) maintain existing active upper-layer sessions: based on its
        current ILCC entries and active sessions, send Locator
        Update (LU) messages to CNs to notify them of the change of
        L values. (LU messages are synonymous to Mobile IPv6 Binding

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     b) if required, update its relevant DNS entries with the new L
        value in the appropriate DNS records, to enable correct
        resolution for new incoming network-layer or transport-layer
        session requests.

   However, it can opt to do this one of two ways:

     1) immediate handover: the host sends Locator Update (LU)
        messages to CNs, immediately stops using L_A and switches
        to using L_B only. In this case, its ILCC entries
        change to:

        [I_H, L_B]                                        --- (19a)
        L_B, ra0                                          --- (19b)

        There might be packets in flight to H which use L_A and H
        MAY choose to ignore these on reception.

     2) soft handover: the host sends Locator Update (LU) messages
        to CNS, but it uses both L_A and L_B until (i) it no longer
        receives incoming packets with destination Locator values
        set to L_A within a given time period (ii) it no longer sees
        RAs for L_A (i.e. it has left the overlap region and so has
        left site network A). In this case, its ILCC entries change

        [I_H, L_A]                                        --- (20a)
        L_A, ra0                                          --- (20b)
        [I_H, L_B]                                        --- (20c)
        L_B, ra0                                          --- (20d)

   ILNP does not mandate the use of one handover option over
   another.  Indeed, a host may implement both and decide, through
   local policy or other mechanisms (e.g. under the control of a
   particular transport protocol implementation), to use one or
   other for a specific transport-layer session, as required.

   Note that if using soft handover, when in the overlap region
   the host is multi-homed. Also, soft handover is likely to
   provide a less disruptive handover (e.g. lower packet loss)
   compared to immediate handover, all other things being equal.

   There is a case where both the host and its correspondent node
   are mobile. In the unlikely event of simultaneous motion which
   changes both nodes' Locators within a very small time period,
   there is the possibility that communication may be lost. If the
   communication between the nodes was direct (i.e. one node
   initiated communication with another, through a DNS lookup)

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   a node can use the DNS to discover the new Locator value(s) for
   the other node. If the communication was through some sort of
   middlebox providing a relay service, then communication is more
   likely to disrupted only if the middlebox is also mobile.

   It is also possible that high packet loss results in Locator
   Updates being lost, which could disrupt handover. However, this
   is an engineering issue and does not impact the basic concept of
   operation: additional discussion on this issue is provided in

   Of course, for any handover, the new end-to-end path through
   SBR_B might have very different end-to-end path characteristics
   (e.g.  different end-to-end delay, packet-loss,
   throughput). Also, the physical connectivity on interface ra0
   as well as through SBR_B's uplink may be different. Such impact
   on end-to-end packet transfer are outside the scope of ILNP.

6.3 Network Mobility

   For network mobility, a whole site may be mobile, e.g. the SBRs
   of Figure 6.1 has a radio uplink on a moving vehicle. Within the
   site, individual hosts may or may not be mobile.

   In the simplest case, ILNP deals with mobile networks in the
   same way as for site multi-homing: the management of mobility
   is delegated to each host in the site, so it needs to be
   ILNP-capable. Each host, effectively, behaves as if it was a
   mobile host, even though it may not actually be mobile. Indeed,
   in this way, the mechanism is very similar to that for site

   Let us consider the mobile network in Figure 6.2.

         site                        ISP_1
        network        SBR           . . .
        . . . .      +------+ L_1   .     .
       .       .     |   ra1+------.       .
      .         .----+      |      .       .
       .  H    .     |   ra2+--    .       .
        . . . .      +------+       .     .
                                     . . .

      Figure 6.2a: ILNP mobile network before handover.

         site                        ISP_1
        network        SBR           . . .

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        . . . .      +------+ L_1   .     .
       .       .     |   ra1+------. . . . .
      .         .----+      |      .       .
       .  H    .     |   ra2+------.       .
        . . . .      +------+ L_2  . . . . .
                                    .     .
                                     . . .

       Figure 6.2b: ILNP mobile network during handover.

         site                        ISP_2
        network        SBR           . . .
        . . . .      +------+       .     .
       .       .     |   ra1+--    .       .
      .         .----+      |      .       .
       .  H    .     |   ra2+------.       .
        . . . .      +------+       .     .
                                     . . .

       Figure 6.2c: ILNP mobile network after handover.

           H = host
         L_1 = global Locator value 1
         L_2 = global Locator value 2
         SBR = Site Border Router

     Figure 6.2: A simple mobile network scenario for ILNP.

   In Figure 6.2, we assume that the site network is mobile,
   and the SBR has two radio interfaces ra1 and ra2. However,
   this particular figure is chosen for simplicity and clarity
   for our scenario, and other configurations are possible,
   e.g. a single radio interface which uses separate radio
   channels (separate carriers, coding channels, etc.) In the
   figure, ISP_1 and ISP_2 are separate, radio-based service
   providers, accessible via ra1 and ra2.

   In Fig 6.2a, the SBR has connectivity via ISP_1 using Locator
   value L_1. The host H, with interface ra0 and Identifier I_H,
   has an established connectivity via the SBR and so has ILCC
   entries as shown in (21):

     [I_H, L_1]                                           --- (21a)
     L_1, ra0                                             --- (21b)

   Note the equivalence to expressions (18a) and (18b). As the whole
   network moves, the SBR detects a new radio provider, ISP_2, and

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   connects to it using ra2, as shown in Figure 6.2b, with the
   service areas of ISP_1 and ISP_2 overlapping. ISP_2 provides
   Locator L_2, which SBR advertises into the site network along
   with L_1. As with the mobile host scenario above, individual
   hosts may decide to perform immediate handover or soft
   handover. So, the ILCC state for H will be as for expressions
   (19a,b) and (20a,b,c,d), but with L_1 in place of L_A and L_2 in
   place of L_B. Finally, as in Figure 6.2c, the site network moves
   and is no longer served by ISP_1, and handover is complete. Note
   that during the handover the site is multi-homed, as in Figure

6.4 Mobility Requirements for Site Border Routers

   As for multi-homing, the SBR does NOT need to be ILNP-capable:
   it simply needs to advertise the available routing prefixes
   into the site network. The mobility capability is handled
   completely by the hosts.

6.5 Mobility with multiple SBRs

   Just as Section 5.3.1 describes the use of multiple routers for
   multi-homing, so it is possible to have multiple routers for
   mobility for ILNP, for both mobile hosts and mobile networks.


   IP Security for ILNP [ILNP-ENG] becomes simpler, in principle,
   than IP Security as it is today, based on the use of IP addresses
   as Identifiers.

   An operational issue in the deployed IP Internet is that the IP
   Security protocols, AH and ESP, have Security Associations (IPsec
   SAs) that include the IP addresses of the secure IPsec session
   endpoints. This was understood to be a problem when AH and ESP
   were originally defined [RFC-1825, RFC-1826, RFC-1827] However,
   the limited set of namespaces in the Internet Architecture did
   not provide any better choices at that time.  ILNP provides more
   namespaces, thus now enabling better IPsec architecture and

7.1 Adapting IP Security for ILNP

   In essence, ILNP provides a very simple architectural change to
   IP security: in place of IP addresses as used today for IPsec

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   SAs, ILNP uses Node Identifier values instead for its IPsec
   SAs. Recall that Identifier values are immutable once in use,
   so they can be used to maintain end-to-end state for any protocol
   that requires it. Note from the discussion above that the
   Identifier values for a host remain unchanged when multi-homing
   and mobility is in use, so IP security using ILNP can work in
   harmony with multi-homing and mobility [ABH08b] [ABH09a].

   To resolve the issue of IPsec interoperability through a Network
   Address Translator (NAT) deployment [RFC1631] [RFC3022], UDP
   encapsulation of IPsec [RFC3948] is commonly used as of the date
   this document was published.  This special-case handling for
   IPsec traffic traversing a NAT is not needed with ILNP IPsec.

   Further, it would obviate the need for specialised IPsec NAT
   Traversal mechanisms, thus simplifying IPsec implementations
   while enhancing deployability and interoperability [RFC3948].

   This architectural change does not reduce the security provided
   by the IP Security protocols.  In fact, had the Node Identifer
   namespace existed back in the early 1990s, IP Security would
   always have bound to that location-independent Node Identifier
   and would not have bound to IP Addresses.

7.2 Operational use of IP Security with ILNP

   Operationally, this change in SA bindings to use Identifiers
   rather than IP addresses causes problems for the use of the IPsec
   protocols through IP Network Address Translation (NAT) devices,
   with mobile nodes (because the mobile node's IP address changes
   at each network-layer handoff), and with multi-homed nodes
   (because the network-layer IPsec session is bound to a particular
   interface of the multi-homed node, rather than being bound to the
   node itself) [RFC3027] [RFC3715].


   ILNPv6 is fully backwards compatible with existing IPv6. No
   router software or silicon changes are necessary to support the
   proposed enhancements. An IPv6 router would be unaware whether
   the packet being forwarded were classic IPv6 or the proposed
   enhancement in ILNPv6. IPv6 Neighbour Discovery will work
   unchanged for ILNPv6.  ILNPv6 multicasting is the same as IETF
   standards-track IPv6 multicasting.

   ILNPv4 is backwards compatible with existing IPv4. As the IPv4
   address fields are used as 32-bit Locators, using only the

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   address prefix bits of the the 32-bit space, IPv4 routers also
   would not require changes.  An IPv4 router would be unaware
   whether the packet being forwarded were classic IPv4 or the
   proposed enhancement in ILNPv4 [ILNP-V4OPTS].  ARP [RFC826]
   requires enhancements to support ILNPv4 [ILNP-ARP] [ILNP-ENG].
   ILNPv4 multicasting is the same as IETF standards-track IPv4

   If a node supports ILNP, and intends to receive incoming
   network-layer or transport-layer sessions, the node's
   Fully-Qualified Domain Name (FQDN) normally will have one or more
   NID records and one or more Locator (i.e. L32, L64, and/or LP)
   records associated with the node within the DNS [ILNP-ENG]

   When an IP host ("initiator") initiates a new network-layer
   session with a correspondent ("responder"), it normally will
   perform a DNS lookup to determine the address(es) of the
   responder. An ILNP host normally will look for Node Identifier
   ("NID") and Locator (i.e. L32, L64, and LP) records in any
   received DNS replies. DNS servers that support NID and Locator
   (i.e. L32, L64, and LP) records SHOULD include them (when they
   exist) as additional data in all DNS replies to queries for DNS
   AAAA records [ILNP-DNS].

   If the initiator supports ILNP, and from DNS information learns
   that the responder also supports ILNP, then the initiator will
   generate an unpredictable ILNP Nonce value, cache that value
   locally as part of the network-layer ILNP session, and will
   include the ILNP Nonce value in its initial packet(s) to the
   responder [ILNP-ENG] [ILNP-NONCEv6] [ILNP-V4OPTS].

   If the initiator node does not find any ILNP-specific DNS
   resource records for the responder node, then the initiator uses
   classic IP for the new network-layer session with the responder,
   rather than trying to use ILNP for that network-layer session. Of
   course, multiple transport-layer sessions can concurrently share
   a single network-layer (e.g. IP or ILNP) session.

   If the responder node for a new network-layer session does not
   support ILNP and the responder node receives initial packet(s)
   containing the ILNP Nonce, then the responder will drop the
   packet and send an ICMP error message back to the initiator. If
   the responder node for a new network-layer session supports ILNP
   and receives initial packet(s) containing the ILNP Nonce, the
   responder learns that ILNP is in use for that network-layer
   session (i.e. by the presence of that ILNP Nonce).

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   If the initiator node using ILNP does not receive a response from
   the responder in a timely manner (e.g. within TCP timeout for a
   TCP session) and also does not receive an ICMP Unreachable error
   message for that packet, OR if the initiator receives an ICMP
   Parameter Problem error message for that packet, then the
   initiator concludes that the responder does not support ILNP. In
   this case, the initiator node SHOULD try again to create the new
   network-layer session, but this time using IP (and therefore
   omitting the ILNP Nonce).

   Finally, since an ILNP node also is a fully-capable IP node, then
   the upgraded node can use any standardised IP mechanisms for
   communicating with a legacy IP-only node. So ILNP will not be
   worse than existing IP, but when ILNP is used the enhanced
   capabilities described in these ILNP documents will be available.


   This proposal outlines a proposed evolution for the Internet
   Architecture to provide improved capabilities. This section
   discusses security considerations for this proposal.

   Note that ILNP provides security equivalent to IP for similar
   threats when similar mitigations (e.g. IPsec or not) are in
   use. In some cases, but not all, ILNP exceeds that objective and
   has lower security risk than IP. Additional engineering details
   for several of these topics can be found in [ILNP-ENG].

9.1 Authentication of Locator Updates

   All Locator Update messages are authenticated. ILNP requires use
   of an ILNP session nonce [ILNP-NONCEv6] [ILNP-V4OPTS] to prevent
   off-path attacks, and also allows use of IPsec cryptography to
   provide stronger protection where required.

   Ordinary network-layer sessions based on IP are vulnerable to
   on-path attacks unless IP Security is used. So the Nonce
   Destination Option only seeks to provide protection against
   off-path attacks on an ILNP-based network-layer session --
   equivalent to ordinary IP-based network-layer sessions that
   aren't using IP Security.

   It is common to have non-symmetric paths between two nodes on the
   Internet. To reduce the number of on-path nodes that know the
   Nonce value for a given session when ILNP is in use, a nonce
   value is unidirectional, not bidirectional. For example, for a
   network-layer ILNP-based session between nodes A and B, one nonce

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   value is used from A to B and a different nonce value is used
   from B to A.

   ILNP sessions operating in higher risk environments SHOULD also
   use the cryptographic authentication provided by IP Security *in
   addition* to concurrent use of the ILNP Nonce.

   It is important to note that at present a network-layer IP-based
   session is entirely vulnerable to on-path attacks unless IPsec is
   in use for that particular IP session, so the security properties
   of the new proposal are never worse than for existing IP.

9.2 Forged Identifier Attacks

   In the deployed Internet, active attacks using packets with a
   forged Source IP Address have been publicly known at least since
   early 1995 [CA-1995-01]. While these exist in the deployed
   Internet, they have not been widespread. This is equivalent to
   the issue of a forged Identifier value and demonstrates that this
   is not a new threat created by ILNP.

   One mitigation for these attacks has been to deploy Source IP
   Address Filtering [RFC2827] [RFC3704]. Jun Bi at U. Tsinghua
   cites Arbor Networks as reporting that this mechanism has less
   than 50% deployment and cites an MIT analysis indicating that at
   least 25% of the deployed Internet permits forged source IP

   In an other document [ILNP-ENG] there is a discussion of an
   accidental use of a duplicate Identifier on the
   Internet. However, this sub-section instead focuses on methods
   for mitigating attacks based on packets containing deliberately
   forged Source Identifier values.

   Firstly, the recommendations of [RFC2827] & [RFC3704] remain.
   So any packets that have a forged Locator value can be easily
   filtered using existing widely available mechanisms.

   Secondly, the receiving node does not blindly accept any packet
   with the proper Source Identifier and proper Destination
   Identifier as an authentic packet. Instead, each ILNP node
   maintains an ILNP Communication Cache (ILCC) for each of its
   correspondents, as described in [ILNP-ENG]. Information in the
   cache is used in validating received messages and preventing
   off-path attackers from succeeding. This process is discussed
   more in [ILNP-ENG]

   Thirdly, any node can distinguish different nodes using the same

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   Identifier value by other properties of their ILNP sessions. For
   example, IPv6 Neighbor Discovery prevents more than one node from
   using the same source I-LV at the same time on the same link
   [RFC4861]. So cases of different nodes using the same Identifier
   value will involve nodes that have different sets of valid
   Locator values. A node thus can demultiplex based on the
   combination of Source Locator and Source Identifier if
   necessary. If IP Security is in use, the combination of the
   Source Identifier and the SPI value would be sufficient to demux
   two different ILNP sessions.

   Fourthly, deployments in high threat environments also SHOULD use
   IP Security to authenticate control traffic and data
   traffic. Because IP Security for ILNP binds only to the
   Identifier values, and never to the Locator values, a mobile or
   multi-homed node can use IPsec even when its Locator value(s)
   have just changed.

   Lastly, note well that ordinary IPv4, ordinary IPv6, Mobile IPv4,
   and also Mobile IPv6 already are vulnerable to forged Identifier
   and/or forged IP address attacks. An attacker on the same link as
   the intended victim simply forges the victims MAC address and the
   victim's IP address. With IPv6, when Secure Neighbour Discovery
   (SEND) and Cryptographically Generated Addresses (CGAs) are in
   use, the victim node can defend its use of its IPv6 address using
   SEND. With ILNP, when SEND and CGAs are in use, the victim node
   also can defend its use of its IPv6 address using SEND. There are
   no standard mechanisms to authenticate ARP messages, so IPv4 is
   especially vulnerable to this sort of attack. These attacks also
   work against Mobile IPv4 and Mobile IPv6. In fact, when either
   form of Mobile IP is in use, there are additional risks, because
   the attacks work not only when the attacker has access to the
   victim's current IP subnetwork but also when the attacker has
   access to the victim's home IP subnetwork. So the risks of using
   ILNP are not greater than exist today with IP or Mobile IP.

9.3 IP Security Enhancements

   The IP Security standards are enhanced here by binding IPsec
   Security Associations (SAs) to the Node Identifiers of the
   endpoints, rather than binding IPsec SAs to the IP Addresses of
   the endpoints as at present. This change enhances the
   deployability and interoperability of the IP Security standards,
   but does not decrease the security provided by those
   protocols. See Section 7 for a more detailed explanation.

9.4 DNS Security

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   The DNS enhancements proposed here are entirely compatible with,
   and can be protected using, the existing IETF standards for DNS
   Security [RFC4033]. The Secure DNS Dynamic Update mechanism used
   here is also used unchanged [RFC3007]. So ILNP does not change
   the security properties of the DNS or of DNS servers.

9.5 Firewall Considerations

   In the proposed new scheme, stateful firewalls are able to
   authenticate ILNP-specific control messages arriving on the
   external interface. This enables more thoughtful handling of ICMP
   messages by firewalls than is commonly the case at present. As
   the firewall is along the path between the communicating nodes,
   the firewall can snoop on the ILNP Nonce being carried in the
   initial packets of an ILNP session. The firewall can verify the
   correct ILNP Nonce is present on incoming control packets,
   dropping any control packets that lack the correct nonce value.

   By always including the ILNP Nonce in ILNP-specific control
   messages, even when IP Security (IPsec) is also in use, the
   firewall can filter out off-path attacks against those ILNP
   messages without needing to perform computationally-expensive
   IPsec processing. In any event, a forged packet from an on-path
   attacker will still be detected when the IPsec input processing
   occurs in the receiving node; this will cause that forged packet
   to be dropped rather than acted upon.

9.6 Neighbour Discovery Authentication

   Nothing in this proposal prevents sites from using the Secure
   Neighbour Discovery (SEND) proposal for authenticating IPv6
   Neighbour Discovery with ILNPv6 [RFC3971].

9.7 Site Topology Obfuscation

   A site that wishes to obscure its internal topology information
   MAY do so by deploying site border routers that rewrite the
   Locator values for the site as packets enter or leave the site.
   This operational scenario was presented in [ABH09a] and is
   discussed in more detail in [ILNP-ADV].

   For example, a site might choose to use a ULA prefix internally
   for this reason [RFC4193] [ID-ULA]. In this case, the site border
   routers would rewrite the Source Locator of ILNP packets leaving
   the site to a global-scope Locator associated with the site.
   Also, those site border routers would rewrite the Destination
   Locator of packets entering the site from the global-scope
   Locator to an appropriate interior ULA Locator for the

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   destination node [ABH08b] [ABH09a] [ILNP-ADV].


   ILNP has support for both:

   - Location Privacy: to hide a node's topological location by
     obfuscating the ILNP Locator information. (See also Section 7
     of [ILNP-ADV].)

   - Identity Privacy: to hide a node's identity by allowing the
     allowing the use of Node Identifier values that are not
     tied to the node in some permanent or semi-permanent manner.
     (See also Section 11 of [ILNP-ENG].)

   A more detailed exposition of the possibilities is given in

10.1 Location Privacy

   Some users have concerns about the issue of "location privacy",
   whereby the user's location might be determined by others. The
   term "location privacy" does not have a crisp definition within
   the Internet community at present. Some mean the location of a
   node relative to the Internet's routing topology, while others
   mean the geographic coordinates of the node (i.e. latitude X,
   longitude Y). The concern seems to focus on Internet-enabled
   devices, most commonly handheld devices such as a "smart phone",
   that might have 1:1 mappings with individual users.

   There is a fundamental trade-off here. Quality of a node's
   Internet connectivity tends to be inversely proportional to the
   "location privacy" of that node. For example, if a node were to
   use a router with NAT as a privacy proxy, routing all traffic to
   and from the Internet via that proxy, then (a) latency will
   increase as the distance increases between the node seeking
   privacy and its proxy, and (b) communications with the node
   seeking privacy will be more vulnerable to communication faults
   -- both due to the proxy itself (which might fail) and due to the
   longer path (which has more points of potential failure than a
   more direct path would have).

   Any Internet node that wishes for other Internet nodes to be able
   to initiate transport-layer or network-layer sessions with it
   needs to include associated address (e.g. A, AAAA) or Locator
   (e.g. L32, L64, LP) records in the publicly accessible Domain
   Name System (DNS). Information placed in the DNS is publicly
   accessible. Since the goal of DNS is to distribute information to

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   other Internet nodes, it does not provide mechanisms for
   selective privacy. Of course, a node that does not wish to be
   contacted need not be present in the DNS.

   In some cases, various parties have attempted to create mappings
   between IP address blocks and geographic locations. The quality
   of such mappings appears to vary [GUF07]. Many such mapping
   efforts are driven themselves by efforts to comply with legal
   requirements in various legal jurisdictions. For example, some
   content providers reportedly have licenses authorising
   distribution of content in one set of locations, but not in a
   different set of locations.

   ILNP does not compromise user location privacy any more than base
   IPv6.  In fact, by its nature ILNP provides additional choices to
   the user to protect their location privacy.

10.2 Identity Privacy

   Both ILNP and IPv6 permit use of identifier values generated
   using the IPv6 Privacy Address extension [RFC4941]. ILNP and IPv6
   also support a node having multiple unicast addresses/locators at
   the same time, which facilitates changing the node's
   addresses/locators over time. IPv4 does not have any non-
   topological identifiers, and many IPv4 nodes only support 1 IPv4
   unicast address per interface, so IPv4 is not directly comparable
   with IPv6 or ILNP.

   In normal operation with IPv4, IPv6, or ILNP, a mobile node might
   intend to be accessible for new connection attempts from the
   global Internet and also might wish to have both optimal routing
   and maximal Internet availability, both for sent and received
   packets. In that case, the node will want to have its addressing
   or location information kept in the DNS and made available to

   In some cases, a mobile node might only desire to initiate
   network-layer or transport-layer sessions with other Internet
   nodes, and thus not desire to be a responder, in which case that
   node need not be present in the DNS. Some potential correspondent
   nodes might, as a matter of local security policy, decline to
   communicate with nodes that do not have suitable DNS records
   present in the DNS.  For example, some deployed IPv4-capable mail
   relays refuse to communicate with an initiating node that lacks
   an appropriate PTR record in the DNS.

   In some cases, for example intermittent electronic mail access or
   browsing specific web pages, support for long-lived network

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   sessions (i.e. where network-layer session lifetime is longer
   than the time the node remains on the same subnetwork) is not
   required. In those cases, support for node mobility
   (i.e. network-layer session continuity even when the SNPA
   changes) is not required and need not be used.

   If an ILNP node that is mobile chooses not to use DNS for
   rendezvous, yet desires to permit any node on the global Internet
   to initiate communications with that node, then that node may
   fall back to using Mobile IPv4 or Mobile IPv6 instead.

   Many residential broadband Internet users are subject to
   involuntary renumbering, usually when their ISP's DHCP server(s)
   deny a DHCP RENEW request and instead issue different IP
   addressing information to the residential user's device(s). In
   many cases, such users want their home server(s) or client(s) to
   be externally reachable. Such users today often use Secure DNS
   Dynamic Update to update their addressing or location information
   in the DNS entries, for the devices they wish to make reachable
   from the global Internet [RFC2136] [RFC3007] [LA2006]. This
   option exists for those users, whether they use IPv4, IPv6, or
   ILNP.  Users also have the option not to use such mechanisms.


   This document has no IANA considerations.

   (Note to RFC Editor; this section can be removed prior to
   publication as an RFC.)


   This section provides normative and informative references
   relating to this note.

12.1.  Normative References

   [RFC768]     J. Postel, "User Datagram Protocol", RFC768,
                August 1980.

   [RFC791]     J. Postel, "Internet Protocol", RFC791,
                September 1981.

   [RFC793]     J. Postel, "Transmission Control Protocol",
                RFC793, September 1981.

   [RFC826]     D. Plummer, "Ethernet Address Resolution Protocol:
                Or Converting Network Protocol Addresses to

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                48 bit Ethernet Address for Transmission on
                Ethernet Hardware", RFC 826, November 1982.

   [RFC2119]    Bradner, S., "Key words for use in RFCs to
                Indicate Requirement Levels", BCP 14, RFC 2119,
                March 1997.

   [RFC2460]    S. Deering & R. Hinden, "Internet Protocol
                Version 6 Specification", RFC2460,
                December 1998.

   [RFC3007]    B. Wellington, "Secure Domain Name System
                Dynamic Update", RFC3007, November 2000.

   [RFC3484]    R. Draves, "Derfault Address Selection for IPv6",
             RFC 3484, February 2003.

   [RFC4033]    R. Arends, et alia, "DNS Security Introduction
                and Requirements", RFC4033, March 2005.

   [RFC4219]    R. Hinden & S. Deering, "IP Version 6
                Addressing Architecture", RFC4219,
                February 2006.

   [RFC4861]    T. Narten, E. Nordmark, W. Simpson, & H. Soliman,
                "Neighbor Discovery for IP version 6 (IPv6)",
                RFC 4861, September 2007.

   [ILNP-ARP]   R.J. Atkinson & S.N. Bhatti, "ARP Extension for
                ILNPv4", draft-irtf-rrg-ilnp-arp, 10 July 2012.

   [ILNP-DNS]     R.J. Atkinson, S.N. Bhatti, & S Rose,
                  "DNS Resource Records for ILNP",
                  draft-irtf-rrg-ilnp-dns, 10 July 2012.

   [ILNP-ENG]     R.J. Atkinson & S.N. Bhatti,
                  "ILNP Engineering and Implementation Considerations",
                  draft-irtf-rrg-ilnp-eng, 10 July 2012.

   [ILNP-ICMPv4]  R.J. Atkinson & S.N. Bhatti,
                  "ICMPv4 Locator Update message"
                  draft-irtf-rrg-ilnp-icmpv4, 10 July 2012.

   [ILNP-ICMPv6]  R.J. Atkinson & S.N. Bhatti,
                  "ICMPv6 Locator Update message"
                  draft-irtf-rrg-ilnp-icmpv6, 10 July 2012.

   [ILNP-NONCEv6] R.J. Atkinson & S.N. Bhatti,

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                 "IPv6 Nonce Destination Option for ILNPv6",
                 draft-irtf-rrg-ilnp-noncev6, 10 July 2012.

   [ILNP-v4OPTS] R.J. Atkinson & S.N. Bhatti,
                 "IPv4 Options for ILNP",
                 draft-irtf-rrg-ilnp-v4opts, 10 July 2012.

12.2.  Informative References

   [8+8]        M. O'Dell, "8+8 - An Alternate Addressing
                Architecture for IPv6", Internet-Draft,
                October 1996.

   [ABH07a]     R. Atkinson, S. Bhatti, & S. Hailes,
                "Mobility as an Integrated Service Through
                the Use of Naming", Proceedings of
                ACM MobiArch 2007, August 2007,
                Kyoto, Japan.

   [ABH07b]     R. Atkinson, S. Bhatti, & S. Hailes,
                "A Proposal for Unifying Mobility with
                Multi-Homing, NAT, & Security",
                Proceedings of ACM MobiWAC 2007, Chania,
                Crete. ACM, October 2007.

   [ABH08a]    R. Atkinson, S. Bhatti, & S. Hailes,
                "Mobility Through Naming: Impact on DNS",
                Proceedings of ACM MobiArch 2008, August 2008,
                ACM, Seattle, WA, USA.

   [ABH08b]    R. Atkinson, S. Bhatti, & S. Hailes,
                "Harmonised Resilience, Security, and Mobility
                Capability for IP", Proceedings of IEEE
                Military Communications (MILCOM) Conference,
                San Diego, CA, USA, November 2008.

   [ABH09a]    R. Atkinson, S. Bhatti, & S. Hailes,
                "Site-Controlled Secure Multi-Homing and
                Traffic Engineering For IP", Proceedings of
                IEEE Military Communications (MILCOM) Conference,
                Boston, MA, USA, October 2009.

   [ABH09b]     R. Atkinson, S. Bhatti, & S. Hailes, "ILNP: Mobility,
                Multi-Homing, Localised Addressing and Security
                Through Naming", Telecommunications Systems,
                Volume 42, Number 3-4, pp 273-291,
                Springer-Verlag, December 2009, ISSN 1018-4864.

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   [ABH10]     R. Atkinson, S. Bhatti, S. Hailes,
               "Evolving the Internet Architecture Through Naming",
               IEEE Journal on Selected Areas in Communication
               (JSAC), vol. 28, no. 8, pp. 1319-1325, IEEE,
               Piscataway, NJ, USA, Oct 2010.

   [BA11]      S. Bhatti & R. Atkinson, "Reducing DNS Caching",
                Proceedings of IEEE Global Internet Symposium
                (GI2011), Shanghai, P.R. China. 15 April 2011.

   [BA12]      S. N. Bhatti & R. Atkinson,
               "Secure & Agile Wide-area Virtual Machine Mobility",
               Procedings of IEEE Military Communications
               Conference (MILCOM), Orlando, FL, USA. Oct 2012.

   [BAK11]     S. Bhatti, R. Atkinson, & J. Klemets, "Integrating
               Challenged Networks", Proceedings of IEEE Military
               Communications Conference (MILCOM), Baltimore, MD,
               USA. November 2011.

   [CA-1995-01] US CERT, "IP Spoofing Attacks and Hijacked
                Terminal Connections", CERT Advisory 1995-01,
                Issued 23 JAN 1995, Revised 23 SEP 1997.

   [GSE]        M. O'Dell, "GSE - An Alternate Addressing
                Architecture for IPv6", Internet-Draft,
                February 1997.

   [ID-ULA]     R. Hinden, G. Huston, & T. Narten, "Centrally
                Assigned Unique Local IPv6 Unicast Addresses",
                draft-ietf-ipv6-ula-central-02.txt, 15 June 2007.

   [IEEE-EUI]   IEEE, "Guidelines for 64-bit Global Identifier
                (EUI-64) Registration Authority",
                IEEE, Piscataway, NJ, USA, March 1997.

   [IEN1]       C.J. Bennett, S.W. Edge, & A.J. Hinchley,
                "Issues in the Interconnection of Datagram
                Networks", Internet Experiment Note (IEN) 1,
                INDRA Note 637, PSPWN 76, University College
                London, London, England, UK, WC1E 6BT,
                29 July 1977.

   [IEN19]      J. F. Shoch, "Inter-Network Naming, Addressing,
                and Routing", IEN-19, January 1978.

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   [IEN23]      J. F. Shoch, "On Names, Addresses, and
                Routings", IEN-23, January 1978.

   [IEN31]      D. Cohen, "On Names, Addresses, and Routings
                (II)", IEN-31, April 1978.

   [IEN135]     C. Sunshine & J. Postel, "Addressing Mobile Hosts in
                the ARPA Internet Environment", IEN 135,
                March 1980.

   [IPng95]     D. Clark, "A thought on addressing",
             electronic mail message to IETF IPng WG,
             Message-ID: 9501111901.AA28426@caraway.lcs.mit.edu,
             Laboratory for Computer Science, MIT,
             Cambridge, MA, USA, 11 January 1995.

   [LA2006]     C. Liu & P. Albitz, "DNS & Bind", 5th Edition,
                O'Reilly & Associates, Sebastopol, CA, USA,
                May 2006.  ISBN 0-596-10057-4

   [LABH06]    M. Lad, R. Atkinson, S. Bhatti, and S. Hailes,
               "A Proposal for Coalition Networking in Dynamic
               Operational Environments", Proceedings of IEEE
               Military Communications Conference, Washington,
               DC, USA. Nov 2006.

   [PHG02]     A. Pappas, S. Hailes, & R. Giaffreda,
               "Mobile Host Location Tracking through DNS",
               Proceedings of IEEE London Communications
               Symposium, IEEE, London, England, UK,
               September 2002.

   [RAB09]     D. Rehunthan, R. Atkinson, & S. Bhatti,
               "Enabling Mobile Networks Through Secure Naming",
               Proceedings of IEEE Military Communications
               Conference (MILCOM), Boston, MA, USA, October 2009.

   [RB10]      D. Rehunathan and S. Bhatti,
               "A Comparative Assessment of Routing for Mobile
               Networks", Proceedings of IEEE International
               Conference on Wireless and Mobile Computing
               Networking and Communications (WiMob2010),
               IEEE, Niagara Falls, ON, Canada. Oct 2010.

   [SBK01]    Alex C. Snoeren, Hari Balakrishnan, & M. Frans
              Kaashoek, "Reconsidering Internet Mobility",
              Proceedings of 8th Workshop on Hot Topics in
              Operating Systems, IEEE, Elmau, Germany, May 2001.

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   [SIPP94]   Bob Smart, "Re: IPng Directorate meeting in
           Chicago; possible SIPP changes", electronic
           mail to the IETF SIPP WG mailing list,
           Commonwealth Scientific & Industrial Research
           Organisation (CSIRO), Melbourne, VIC, 3001,
           Australia, 2 June 1994.

   [SRC84]    J. Saltzer, D. Reed, & D. Clark, "End to End
              Arguments in System Design", ACM Transactions on
              Computer Systems, Volume 2, Number 4, ACM,
              New York, NY, USA, November 1984.

   [RFC814]   D.D. Clark, "Names, Addresses, Ports, and
              Routes", RFC814, July 1982.

   [RFC1122]  R. Braden, "Requirements for Internet Hosts -
              Communication Layers", RFC1122, October 1989.

   [RFC1498]  J.H. Saltzer, "On the Naming and Binding of
              Network Destinations", RFC1498, August 1993.

   [RFC1631]  K. Egevang & P. Francis, "The IP Network
              Address Translator (NAT)", RFC1631, May 1994.

   [RFC1825]  R. Atkinson, "Security Architecture for the Internet
              Protocol", RFC-1825, August 1995.

   [RFC1826]  R. Atkinson, "IP Authentication Header", RFC-1826,
              August 1995.

   [RFC1827]  R. Atkinson, "IP Encapsulating Security Payload",
              RFC-1827, August 1995.

   [RFC1958]  B. Carpenter (Ed.), "Architectural Principles
              of the Internet", RFC1958, June 1996.

   [RFC1992]  I. Castineyra, N. Chiappa, & M. Steenstrup,
              "The Nimrod Routing Architecture", RFC1992,
              August 1996.

   [RFC2002]  C. Perkins et alia, "IP Mobility Support",
              RFC 2002, October 1996.

   [RFC2101]  B. Carpenter, J. Crowcroft, & Y. Rekhter,
              "IPv4 Address Behaviour Today", RFC2101,
                February 1997.

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   [RFC2136]  P. Vixie, S. Thomson, Y. Rekhter, and J. Bound,
              "Dynamic Updates in the Domain Name System",
              RFC2136, April 1997.

   [RFC2827]  P. Ferguson & D. Senie, "Network Ingress Filtering:
              Defeating Denial of Service Attacks which employ
              IP Source Address Spoofing", RFC2827, May 2000.

   [RFC2956]  M. Kaat, "Overview of 1999 AB WOrkshop", RFC2956,
              October 2000.

   [RFC3177]  IAB and IESG, "IAB/IESG Recommendations on IPv6
              Address Allocations to Sites", RFC3177, September

   [RFC3022]  P. Srisuresh & K. Egevang, "Traditional IP
              Network Address Translator", RFC3022,
              January 2001.

   [RFC3027]  M. Holdrege and P Srisuresh, "Protocol
              Complications of the IP Network Address
              Translator", RFC3027, January 2001.

   [RFC3704]  F. Baker & P. Savola, "Ingress Filtering for
              Multihomed Networks, RFC3704, March 2004.

   [RFC3715]  B. Aboba and W. Dixon, "IPsec-Network Address
              Translation (NAT) Compatibility Requirements",
              RFC3715, March 2004.

   [RFC6250]  D. Thaler, "Evolution of the IP Model",
              RFC6250, May 2011.

   [RFC6275]  C. Perkins, D. Johnson, and J. Arkko, "Mobility
              Support in IPv6", RFC6275, July 2011.

   [RFC3948]  A. Huttunen, et alia, "UDP Encapsulation of
              IPsec ESP Packets", RFC3948, January 2005.

   [RFC3971]  J. Arkko, J. Kempf, B. Zill, & P. Nikander,
              "SEcure Neighbor Discovery (SEND)", RFC3971
              March 2005.

   [RFC3972]  T. Aura, "Cryptographically Generated Addresses
              (CGAs)", RFC3972, March 2005.

   [RFC4193]  R. Hinden & B. Haberman, "Unique Local IPv6
              Unicast Addresses, RFC4193, October 2005.

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   [RFC4291]  R. Hinden & S. Deering, "IP version 6 Addressing
              Architecture", RFC4291, February 2006.

   [RFC4581]  M. Bagnulo & J. Arkko, "Cryptographically Generated
              Addresses Extension Field Format", RFC4581,
              October 2006.

   [RFC4941]  T. Narten, R. Draves, & S. Krishnan, "Privacy
              Extensions for Stateless Address Autoconfiguration
              in IPv6", RFC4941, September 2007.

   [RFC4982]  M. Bagnulo & J. Arkko, "Support for Multiple Hash
              Algorithms in Cryptographically Generated
              Addresses", RFC4982, July 2007.

   [RFC4984]  D. Meyer, L. Zhang, K. Fall, "Report from the IAB
              Workshop on Routing and Addressing", RFC4984,
              September 2007.

   [RFC5061]  R. Stewart, Q. Xie, M. Tuexen, S. Maruyama, &
              M. Kozuka, "Stream Control Transmission Protocol
              (SCTP) Dynamic Address Reconfiguration", RFC5061,
              September 2007.

   [RFC6177]  T. Narten, G. Huston, L. Roberts, "IPv6 Address
              Assignment to End Sites", RFC6177 (BCP157), March

   [GUF07]    B. Gueye, S. Uhlig, & S. Fdida, "Investigating the
              Imprecision of IP Block-Based Geolocation",
              Lecture Notes in Computer Science, Volume 4427,
              pp. 237-240, Springer-Verlag, Heidelberg,
              Germany, 2007.

   [ILNP-ADV]  R.J. Atkinson & S.N. Bhatti,
               "Optional Advanced Deployment Scenarios for ILNP",
               draft-irtf-rrg-ilnp-adv, 10 July 2012.


   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

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   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.

   Noel Chiappa graciously provided the authors with copies of the
   original email messages cited here as [SIPP94] and [IPng95],
   which enabled the precise citation of those messages herein.


   This section is to be removed prior to publication.

   Please note that this document is written in British English, so
   British English spelling is used throughout. This is consistent
   with existing practice in several other RFCs, for example

   This document tries to be very careful with history, in the
   interest of correctly crediting ideas to their earliest
   identifiable author(s). So in several places the first published
   RFC about a topic is cited rather than the most recent published
   RFC about that topic.

Author's Address

   RJ Atkinson
   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, Scotland
   KY16 9SX, UK

   Email: saleem@cs.st-andrews.ac.uk

   Expires: 10 JAN 2013

Atkinson & Bhatti  Expires in 6 months                         [Page 53]

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