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Internet Draft                                              RJ Atkinson
draft-irtf-rrg-ilnp-eng-00.txt                               Consultant
Expires:  09 JUL 2012                                         SN Bhatti
Category: Experimental                                    U. St Andrews
                                                         9 January 2012

                    ILNP Engineering Considerations
                     draft-irtf-rrg-ilnp-eng-00.txt

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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   This document may contain material from IETF Documents or IETF
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   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.

   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
   progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/1id-abstracts.html

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html

   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.

   The ILNP document set 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
   IRTF Routing RG. The views in this document were considered
   controversial by the Routing RG, but the RG reached a consensus
   that the document still should be published. The Routing RG has
   had remarkably little consensus on anything, so virtually all
   Routing RG outputs are considered controversial.

Abstract

   This document describes common (i.e. version independent)
   engineering details for the Identifier-Locator Network Protocol
   (ILNP), which is an experimental, evolutionary enhancement to IP.
   This document is a product of the IRTF Routing RG.


Table of Contents

      1.  Introduction ..........................................2
      2.  Generating Identifiers.................................3
      3.  Transport-Layer Changes................................?
      4.  ILNP Correspondent Cache...............................?
      5.  Handling Location/Connectivity Changes.................?
      6.  Secure Dynamic DNS Update..............................?
      7.  Backwards Compatibility................................?
      8.  Incremental Deployment.................................?
      9.  Security Considerations ..............................21
      10. IANA Considerations...................................28
      11. References ...........................................28

1. INTRODUCTION



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   The Identifier Locator Network Protocol (ILNP) is an experimental
   network protocol that provides evolutionary enhancements to
   IP. ILNP is backwards-compatible with IP and also is
   incrementally deployable. The best starting point for learning
   about ILNP is the ILNP Architectural Description, which includes
   a document roadmap [ILNP-ARCH].

   ILNP is a single architecture that can have multiple
   instantiations.  Engineering considerations common to all
   instantiations of ILNP are described in this document. Packet
   formats and certain other IPv4-centric details of ILNP for IPv4
   (ILNPv4) are specified in separate documents [ILNP-v4opts]
   [ILNP-ICMPv4]. Packet formats and certain other IPv6-centric
   details of ILNP for IPv6 (ILNPv6) are specified in separate
   documents [ILNP-NONCE6] [ILNP-ICMPv6].

1.1 Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

2. ILNP IDENTIFIERS

   All ILNP nodes must have at least one Identifier value. However,
   there are various options for generating those Identifier
   values. We describe in this section the relevant engineering
   issues related to Identifier generation and usage.

   Note well that ILNP Identifiers name an ILNP-capable node, and
   are NOT bound to a specific interface of that node. So a given
   ILNP Identifier is valid on all active interfaces of the node to
   which that ILNP Identifier is bound. This is true even if the
   bits used to form the Identifier value happened to be taken from
   a specific interface as an engineering convenience.

   2.1 Syntax

   ILNP Identifiers are always unsigned 64-bit strings, and may be
   realised as 64-bit unsigned integers. Both ILNPv4 and ILNPv6 use
   the Modified EUI-64 syntax that is used by IPv6 Interface
   Identifiers, as shown in Figure 1.

          +--------------------------------------------------+
          |  6 id bits  | U bit | G bit |      24 id bits    |
          +--------------------------------------------------+
          |                   32 id bits                     |
          +--------------------------------------------------+



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     Figure 1. IEEE EUI-64 format as used for IPv6 [RFC4291, Sec 2.5.1].

   That syntax contains two special reserved bit flags. One flag
   (the U bit) indicates whether the value has "universal"
   (i.e. global) scope (1) or "local" (0) scope. The other flag (the
   G bit) indicates whether the value is an "individual" address (1)
   or "group" (i.e multicast) (0) address.

   However, this format does allow other values to be set, by use of
   administrative or other policy control, as required, by setting
   the U bit to "local".


   2.1 Default values for an Identifier

   By default, this value, including the U bit and G bit, are set as
   described in Appendix A of RFC4291 [RFC4291]. Where no other
   value of Identifier is available for an ILNP node, this is the
   value that MUST be used.

   Because ILNP Identifiers might have local scope, and also to
   handle the case where two nodes at different locations happen to
   be using the same global scope Identifier (e.g. due to a
   manufacturing fault in a network chipset or card), implementers
   must be careful in how ILNP Identifiers are handled within an end
   system's networking implementation. Some details are discussed in
   Section 4 below.


   2.2 Local-scoped Identifier values

   ILNP Identifiers for a node also MAY have the Scope bit of the
   Modified EUI-64 set to "local"" scope. Locally unique identifiers
   MAY be Cryptographically Generated, created following the
   procedures used for IPv6 Cryptographically Generated Addresses
   (CGAs) [RFC3972] [RFC4581] [RFC4982].

   Also, locally unique identifiers MAY be used to create the ILNP
   equivalent to the "Privacy Extensions for IPv6", generating ILNP
   Identifiers following the procedures used for IPv6 [RFC4941].


   2.3 Multicast Identifiers

   An ILNP Identifier with the G bit set to "group" names an ILNP
   multicast group, while an ILNP Identifier with the G bit set to
   "individual" names an individual ILNP node. However, this usage
   of multicast for Identifiers for ILNP is currently undefined:



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   ILNP uses IPv6 multicast for ILNPv6 and IPv4 multicast for ILNPv4
   and uses the multicast address formats defined as
   appropriate. The use of multicast Identifiers and design of an
   enhanced multicast capability for ILNPv6 and ILNPv4 is currently
   work in progress.


3.  TRANSPORT-LAYER CHANGES

   ILNP uses an Identifier value in order to form the invariant
   end-system state for end-to-end protocols. Currently, transport
   protocols such as TCP and UDP use all the bits of an IP address
   to form such state. So, transport protocol implementations MUST
   be modified in order to operate over ILNP.

   3.1 End-system state

   Currently, TCP and UDP, for example, use the 4-tuple:

     <local IP address, remote IP address, local port, remote port>

   for the end-system state for a transport layer end-point. For
   ILNP, implementations must be modified to instead use:

     <local Identifier, remote Identifier, local port, remote port>

   3.2 Pseudo-header checksum

   In IP-based implementations, the TCP or UDP pseudo-header
   checksum calculations include all the bits of the IP address.
   By contrast, when calculating the TCP or UDP pseudo-header
   checksums for use with ILNP, only the Identifier values are
   included in the TCP or UDP pseudo-header checksum calculations.

   To minimise the changes required within transport protocol
   implementations, and to maximise interoperability, current
   implementations are modified to zero the Locator fields (only for
   the purpose of TCP or UDP checksum calculations).  For example,
   for ILNPv6, this means that the existing code for IPv6 can be
   used, with the ILNPv6 Identifier bits occupying the lower 64 bits
   of the IPv6 address field, and the upper 64 bits of the IPv6
   address filed being set to zero.  For ILNPv4, the Identifier
   fields are carried in an IPv4 Option [ILNP-v4opts].

   Section 7 describes methods for incremental deployment of this
   ILNP-specific change and backwards compatibility with non-
   upgraded nodes (e.g. classic IPv4 or IPv6 nodes) in more detail.




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4.  ILNP CORRESPONDENT CACHE (ILCC)

   For operational purposes, implementations need to have a local
   cache of state information that allow communication end-points to
   be constructed and for communication protocols to operate. Such
   cache information is common today, e.g. IPv4 nodes commonly
   maintain an Address Resolution Protocol (ARP) cache with
   information relating to current and recent Correspondent Nodes;
   IPv6 nodes maintain a Neighbor Discovery (ND) table with
   information relating to current and CNs. Likewise, ILNP maintains
   an Identifier-Locator Correspondent Cache (ILCC) with information
   relating to the operation of ILNP.

   The ILCC is a (logical) set of data values required for ILNP to
   operate. These values are maintained by the endpoints of each
   ILNP communications session. From an engineering viewpoint, the
   ILCC could be implemented by extending or enhancing existing data
   structures within existing implementations. For example, by
   adding appropriate flags to the data structures in existing
   implementations.

   In theory, this cache is within the ILNP network-layer. However,
   many network protocol implementations do not have strict protocol
   separation or layering. So there is no requirement that the ILCC
   be kept partitioned from transport-layer protocols.

4.1  Formal Definition

   The ILCC contains information about both the local node and also
   about current or recent correspondent nodes, as follows.

   Information about the local node:

      - Each currently valid Identifier value,
             including its Identifier Precedence
           and whether it is active at present.

      - Each currently valid Locator value, including
           its associated local interface(s),
             its Locator Precedence, and
           whether it is active at present.

      - Each currently valid IL Vector (IL-V), including
           whether it is active at present.

   Information about each correspondent node:

      - Most recent set of Identifiers,



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             including lifetime and validity for each.

      - Most recent set of Locators,
             including lifetime and validity for each.

      - Nonce value for packets from the local host
             to the correspondent.

      - Nonce value for packets from the correspondent
             to the local host.


   In the above list for the ILNP Correspondent Cache:

    - A "valid" item is useable, from an administrative point of
      view, but might or might not be in use at present.

    - The "validity" parameter for the correspondent node indicates
      one of several different states for a datum. These include at
      least the following:

        - "valid"   : data is useable and has not expired.

       - "active"  : data is useable, has not expired,
                         and is in active use at present.

        - "expired" : data is still in use at present,
                         but is beyond its expiration (i.e.
                         without a replacement value).

        - "aged"    : data was recently in use, but is not
                         in active use at present, and is
                         beyond its expiration.

     - The "lifetime" parameter is an implementation-specific
       representation of the validity lifetime for the associated
       data element. In normal operation, the Lifetime for a
       correspondent node's Locator(s) are learned from the DNS
       Time-To-Live (DNS TTL) value associated with DNS records
       (ID, L32, L64 etc) of the FQDN owner name of the
       correspondent node. For time, a node might use UTC
       (e.g. via Network Time Protocol) or perhaps some
       node-specific time (e.g. seconds since node boot).

4.2 Aging ILCC Entries

   As a practical matter, it is not sensible to flush all Locator
   values associated with an existing session's correspondent node



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   even if the DNS TTL associated with those Locator values expires.

   In some situations, a CN might be disconnected briefly when
   moving location (e.g. immediate handover). If this happens, there
   might be a brief pause before the Correspondent Node can (a)
   update its own L values in the DNS and (b) send an ICMP Locator
   Update message to the local node with information about its new
   location. Implementers ought to try to maintain ILNP sessions
   even when such events occur.

   Instead, Locator values cached for a correspondent node SHOULD be
   marked as "aged" when their TTL has expired, but retained until
   either the next Locator Update message is received, there is
   other indication that a given Locator is not working any longer,
   there is positive indication that the Correspondent Node has
   terminated the session (e.g.  TCP RST), until some appropriate
   timeout (e.g. 2*MSL for TCP), or the session has been inactive
   for several minutes and the storage space associated with the
   aged entry needs to be reclaimed.

   Separately, received authenticated Locator Update messages cause
   the ILCC entries listed above to be updated.

   Similarly, if there is indication that a session with a
   Correspondent Node remains active and the DNS TTL associated with
   that Correspondent Node's active Identifier value(s) has expired,
   those remote Identifier value(s) ought to be marked as "aged" but
   retained since they are in active use.

4.3  Large Numbers of Locators

   Implementers should keep in mind that a node or site might have a
   large number of concurrent Locators, and should ensure that a
   system fault does not arise if the system receives an authentic
   ICMP Locator Update containing a large number of Locator values.

4.4  Lookups into the ILCC

   For received packets containing an ILNP Nonce Option, lookups in
   the ILCC MUST use the <remote Identifier, Nonce> tuple as the
   lookup key.  This facilitates situations where, perhaps due to
   deployment of Local-scope Identifiers, more than one
   Correspondent Node is using the same Identifier value.

   For all other ILNP packets, lookups in the ILNP Correspondent
   Cache MUST use the <remote Locator, remote Identifier} tuple as
   the lookup key. This facilitates situations where, perhaps due to
   deployment of Local-scope Identifiers, more than one



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   correspondent node is using the same Identifier value.

   (NOTE: Other mechanisms, such as IPv6 Neighbor Discovery, ensure
   that 2 different nodes are incapable of using a given IL-V tuple
   at the same location.)

   While Locators are omitted from the transport-layer checksum, an
   implementation SHOULD use Locator values to distinguish between
   correspondents coincidentally using the same Identifier value
   (e.g. due to deployment of Local-scope Identifier values) when
   demultiplexing to determine which application(s) should receive
   the user data delivered by the transport-layer protocol.


5.  HANDLING LOCATION/CONNECTIVITY CHANGES

   In normal operation, an ILNP node uses the DNS for initial
   rendezvous in setting up sessions. The use of DNS for initial
   rendezvous with mobile nodes was earlier proposed by others
   [PHG02] and then separately re-invented by the current authors
   later on.

5.1  Node Location/Connectivity Changes

   To handle the move of a node or a change to the upstream
   connectivity of a multi-homed node, we add a new ICMP control
   message [ILNP-ICMPv4] [ILNP-ICMPv6]. The ICMP Locator Update (LU)
   message is used by a node to inform its existing CNs that the set
   of valid Locators for the node has changed.  This mechanism can
   be used to add newly valid Locators, to remove no longer valid
   Locators, or to do both at the same time. The LU mechanisms is
   analogous to the Binding Update mechanism in Mobile IPv6, but in
   ILNP, such messages are used any time Locator value changes need
   to be notified to CNs, e.g. for multi-homed hosts as well as for
   mobile hosts.

   Further, if the node wishes to be able to receive new incoming
   sessions, the node uses Secure Dynamic DNS Update [RFC3007] to
   ensure that a correct set of Locator values are present in the
   appropriate DNS records (i.e. L32, L64) in the DNS for that node
   [ILNP-DNS]. This enables any new correspondents to correctly
   initiate a new session with the node at its new location.

   While the Locator Update control message could be an entirely new
   protocol running over UDP, for example, there is no obvious
   advantage to creating a new protocol rather than using a new ICMP
   message.  So ILNP defines a new ICMP Locator Update message
   for both IPv4 and IPv6.



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5.2  Network Connectivity/Locator Changes

   As a DNS performance optimisation, the LP DNS resource record
   MAY be used to avoid requiring each node on a subnetwork to
   update its DNS L64 record entries when that subnetwork's
   location (e.g. upstream connectivity) changes [ILNP-DNS].
   This can reduce the number of DNS updates required when a
   subnetwork moves from O(number of nodes on subnetwork) to O(1).

   In this case, the nodes on the subnetwork each would have an LP
   record pointing to a common Fully-Qualified Domain Name (FQDN)
   used to name that subnetwork. In turn, that subnetwork's domain
   name would have one or more L64 record(s) in the DNS. Since the
   contents of an LP record are stable, relatively long DNS TTL
   values can be associated with these records facilitating DNS
   caching. By contrast, the DNS TTL of an L32 or L64 record for a
   mobile or multi-homed node should be small.  Experimental work at
   the University of St Andrews indicates that the DNS continues to
   work well even with very low (e.g. zero) DNS TTL values [BA2011].

   Correspondents of a node on a mobile subnetwork using this DNS
   performance optimisation would perform an ID, L32, or L64 record
   query for that target node, and would receive the LP records as
   additional data in the DNS reply. Next, the correspondent would
   perform an L32 or L64 record lookup on the domain-name pointed to
   by that LP record, in order to learn the Locator value to use to
   reach that target node.


6. DNS CONSIDERATIONS

   ILNP makes use of DNS for name resolution, as does IP. However,
   unlike IP, ILNP also uses DNS to support functions such as
   mobility and multi-homing. While such usage is appropriate to the
   function of DNS, it is important to discuss operational and
   engineering issues that may impact DNS usage.

6.1 Secure Dynamic DNS Update

   When a host that expects incoming connections changes one or more
   of its Locator values, the host normally uses the IETF Secure
   Dynamic DNS Update protocol [RFC3007] to update the set of
   currently valid Locator values associated with its Fully
   Qualified Domain Name (FQDN). This ensures that the authoritative
   DNS server for its FQDN will be able to generate an accurate set
   of Locator values if the DNS server receives DNS name resolution
   request for its FQDN.




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   Liu & Albitz [LA2006] report that Secure Dynamic DNS Update has
   been supported on the client-side for several years now in widely
   deployed operating systems (e.g. MS Windows, Apple MacOS X, UNIX,
   and Linux) and also in DNS server software (e.g. BIND). Publicly
   available product data sheets indicate that some other DNS server
   software packages, such as that from Nominum, also support this
   capability.

   For example, Microsoft Windows XP (and later versions), the
   freely distributable BIND DNS software package (used in Apple
   MacOS X and in most UNIX systems), and the commercial Nominum DNS
   server all implement support for Secure Dynamic DNS Update and
   are known to interoperate [LA2006]. There are credible reports
   that when a site deploys Microsoft's Active Directory, the site
   (silently) automatically deploys Secure Dynamic DNS Update
   [LA2006]. So, many sites have already deployed Secure Dynamic DNS
   Update even though they are not actively using it (and might not
   be aware they have already deployed that protocol) [LA2006].

   So DNS update via Secure Dynamic DNS Update is not only
   standards-based, but also readily available in widely deployed
   systems today.


6.3. New DNS RR types

   As part of this proposal, additional DNS Resource Records have
   been proposed in a separate document [ILNP-DNS]. These new
   records are summarised in Table 6.1.

       new DNS RR type |  Purpose
      -----------------+------------------------------------------------
             ID        | store the value of an Identifier
             L32       | store the value of a 32-bit Locator for ILNPv4
             L64       | store the value of a 64-bit Locator for ILNPv6
             LP        | points to a (several) L32 and/or L64 record(s)
      -----------------+------------------------------------------------

      Table 6.1: Summary of new DNS RR types for ILNP

   With this proposal, mobile or multi-homed nodes and sites are
   expected to use the existing "Secure Dynamic DNS Update" protocol
   to keep their Identifier (ID) and Locator (L32 and/or L43)
   records correct in their authoritative DNS server(s) [RFC3007]
   [ILNP-DNS].

   Reverse DNS lookups, to find a node's Fully Qualified Domain Name
   from the combination of a Locator and related Identifier value,



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   can be performed as at present.

6.4 DNS TTL values for ILNP RRS types

   Existing DNS specifications require that DNS clients and DNS
   resolvers honour the TTL values provided by the DNS servers. In
   the context of this proposal, short DNS TTL values are assigned
   to particular DNS records to ensure that the ubiquitous DNS
   caching resolvers do not cache volatile values (e.g. Locator
   records of a mobile node) and consequently return stale
   information to new requestors.

   The time-to-live (TTL) values for L32 and L64 records may have to
   be relatively low (perhaps a few seconds) in order to support
   mobility and multi-homing. Low TTL values may be of concern to
   administrators who might think that this would reduce efficacy of
   DNS caching increase DNS load significantly.

   Previous research by others indicates that DNS caching is largely
   ineffective, with the exception of NS records and the addresses
   of DNS servers referred to by NS records [SBK2002]. This means
   DNS caching performance and DNS load will not be adversely
   affected by assigning very short TTL values (down to zero) to the
   Locator records of typical nodes for a edge site [BA2011]. It
   also means that it is preferable to deploy the DNS server
   function on nodes that have longer DNS TTL values, rather than on
   nodes that have shorter DNS TTL values.

   LP records normally are stable and will have relatively long TTL
   values, even if the L32 or L64 records they point to have values
   that have relatively low TTL values.

   Identifier values might be very long-lived (e.g. days) when they
   have been generated from an IEEE MAC address on the
   system. Identifier values might have a shorter lifetime
   (e.g. hours or minutes) if they have been cryptographically-
   generated [RFC3972], or have been created by the IPv6 Privacy
   Extensions [RFC4941], or otherwise have the EUI-64 scope bit set
   to "local-scope". Note that when ILNP is used, the cryptographic
   generation method described in RFC 3972 is used only for the
   Identifier, omitting the Locator, thereby preserving roaming
   capability. Note that a given ILNP session normally will use a
   single Identifier value for the lifetime of that session.

6.5 IP/ILNP dual operation and transition

   During a long transition period, a node that is ILNP-capable
   SHOULD have not only have ID and l32/L64 (or ID and LP) records



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   present in its authoritative DNS server, but also SHOULD have
   A/AAAA records in the DNS for the benefit of non-upgraded
   nodes. Then, when any CN performs an FQDN lookup for that node,
   it will receive the A/AAAA with the appropriate ID, L32/L64
   and/or LP records as "additional data".

   Existing DNS specifications require that a DNS resolver or DNS
   client ignore unrecognised DNS record types. So gratuitously
   appending ID and Locator (i.e., L32, L64, or LP) records as
   "additional data" in DNS responses to A/AAAA queries ought not to
   create any operational issues.  So, IP only nodes would use the
   A/AAAA RRs, but ILNP-capable nodes would be able to use the ID,
   L32/L64 and/or LP records are required.

   There is nothing to prevent this capability being implemented
   strictly inside a DNS server, whereby the DNS server synthesises
   a set of A/AAAA records to advertise from the ID and Locator
   (i.e., L32, L64, or LP) values that the node has kept updated in
   that DNS server. Indeed, such a capability may be desirable,
   reducing the amount of manual configuration required for a site,
   and reducing the potential for errors as the A/AAAA records would
   be automatically generated.


7.  BACKWARDS COMPATIBILITY & INCREMENTAL DEPLOYMENT

   Experience with IPv6 deployment over the past many years has
   shown that it is important for any new network protocol to
   provide backwards compatibility with the deployed IP base and
   should be incrementally deployable, ideally requiring
   modification of only those nodes that wish to use ILNP and no
   requiring the modification of nodes that do not intend to use
   ILNP. The two instances of ILNP, ILNPv4 and ILNPv6, are intended
   to be, respectively, backwards compatible with, and incrementally
   deployable on, the existing IPv4 and IPv6 installed
   based. Indeed, ILNPv4 and ILNPv6 each be seen, from an
   engineering viewpoint, as supersets of the IPv4 and IPv6
   respectively.

   However, in some cases, ILNP introduces functionality that
   supersedes equivalent functionality available in IP. For example,
   ILNP has a mobility model and so does not need to use the models
   for Mobile IPv4 or Mobile IPv6.

   As ILNP changes the use of end-to-end namespaces, for the most
   part, it is only end-systems that need to be modified. However,
   in order to leverage existing engineering (e.g. existing
   protocols), in some cases, there is a compromise, and these



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   are highlighted in this section.

7.1 Interworking between IP and ILNP

   A related topic is interworking: for example, how would an IPv6
   node communicate with an ILNPv6 node? Currently, we make the
   assumption that ILNP nodes "drop down" to using IP when
   communicating with a non-ILNP capable node, i.e. there is no
   interworking as such. In the future, it may be beneficial to
   define interworking scenarios, for example by the use of suitable
   gateways or middleboxes. However, at the current time, such
   functionality is not defined.

   Realistically, we see that it is likely that just as many
   observers expect IPv4 to remain in place for a long time even
   though IPv6 has been available for over a decade, it is likely
   that in the future there may be hosts that are both IP and ILNP
   hosts. Until there is a better understanding of the deployment
   and usage scenarios that will develop, it is not clear what
   interworking scenarios would be useful to define between IP and
   ILNP.


7.2 Priorities in the design of ILNPv4 and ILNPv4

   In the engineering design of ILNPv4 and ILNPv6, we have used the
   following priorities. In some ways, this choice is arbitrary, and
   it may be equally valid to "invert" these priorities for a
   different architectural and engineering design.

     1. Infrastructure

        As much of the deployed IP network infrastructure should be
        used without change. That is, routers and switches should
        require minimal or zero modifications in order to run
        ILNP. As much of the existing installed base of core
        protocols should be re-used.


     2. Core protocols

        As much of the deployed network control protocols, such as
        routing, should be used without change. That is, existing
        routing protocols and switch configuration should require
        minimal or zero modifications in order to run ILNP.

     3. Scope of end-system changes




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        Any nodes that do not need to run ILNP should not need to be
        upgraded. It should be possible to have a site network that
        has a mix of IP-only and ILNP-capable nodes without any
        changes required to the IP-only nodes.

     4. Applications

        There should be minimal impact on applications, even though
        ILNP requires end-to-end protocols to be upgraded. Indeed,
        for those applications that are "well-behaved" (e.g. do not
        use IP address values directly for application state or
        application configuration), there should be little or no
        effort required in enabling them to operate over ILNP.

   Each of these items is discussed in its own section below.


7.3 Infrastructure

   ILNP is designed to be deployed on existing infrastructure. No
   new infrastructure is required to run ILNP as it will be
   implemented as a software upgrade impacting only end-to-end
   protocols. Existing routing protocols can be re-used: no new
   routing protocols are required. This means that network operators
   and service providers do not need to learn about, test, and deploy
   new protocols, or change the structure of their network in order
   for ILNP to be deployed.  Exceptionally, edge routers supporting
   ILNPv4 hosts will need to support an enhanced version of ARP.

7.4 Core protocols

   Existing routing and other control protocols should not need to
   change in devices such as switches and routers. We believe this
   to be true for ILNPv6.  However, for ILNPv4, we believe that ARP
   will need to be enhanced in edge routers (or layer-3 switches)
   that support ILNPv4 hosts.  Backbone and transit routers
   still ought not require changes for either ILNPv4 or ILNPv6.

   However, for both ILNPv4 and ILNPv6, the basic packet format for
   packets re-uses that format that is seen by routers for IPv4 and
   IPv6 respectively. Specifically, as the ILNP Locator value is
   always a routing prefix (either IPv4 or IPv6), routing protocols
   should work unchanged.

   For packet forwarding, as both ILNPv4 and ILNPv6 introduce new
   header options (e.g Nonce Option messages) and ICMP messages
   (e.g. Locator Update messages) which are used to enable
   end-to-end signalling, depending on the forwarding policies used



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   by some providers or site border routers, there may need to be
   modifications to those policies to allow the new header options
   and new ICMP messages to be forwarded.  However, as the header
   options and new ICMP messages are end-to-end, such modifications
   are likely to be in configuration files (or firewall policy on
   edge routers), as core routers do NOT need to parse and act upon
   the information contained in the header options or ICMP messages.


7.5 Scope of end-system changes

   Only end-systems that need to use ILNP need to be updated in
   order for ILNP to be used at a site.

   There are three exceptions to this statement as follows:

     a) ILNPv4 ARP: as the Identifier value for IPv4 cannot fit into
        the normal 20-byte IPv4 packet header (a header extension is
        used), ARP must be modified. This only impacts end-systems
        that use ILNPv4 and those switches or site-border routers
        that are the first hop from an ILNPv4 node. For ILNPv6, as
        the I and L values fit into the existing basic IPv6 packet,
        IPv6 Neighbour Discovery can operate without modification

     b) Use of IP NAT: Where IP NAT or NAPT is in use for a site,
        existing NAT/NAPT device will re-write address fields in
        ILNPv4 packets or ILNPv6 packets. To avoid this, the NAT
        should either (i) configured to allow the pass-through of
        packets originating from ILNP-capable nodes (e.g.  by
        filtering on source address fields in the IP header);
        or (ii) should be enhanced to recognise ILNPv4 or ILNPv6
        packets (e.g. by looking for the ILNP Nonce option).

     c) Site border routers (SBRs) in ILNP Advanced Deployment
        scenarios: There are options to use an ILNP-capable site
        border router (SBR) as described in another document
        [ILNP-ADV]. In such scenarios, the SBR(s) need to be
        ILNP-capable.

   Other than these exceptions, it is entirely possible to have a
   site that uses a mix of IP and ILNP nodes and requires no changes
   to nodes other than the nodes that wish to use ILNP. For example,
   if a user on a site wishes to have his laptop use ILNPv6, only
   that laptop would need to have an upgraded stack: no other
   devices (end-systems, layer-2 switches or routers) at that site
   would need to be upgraded.





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7.6 Applications

   As noted, in the Architecture Description [ILNP-ARCH], those
   applications that do not use IP address values in application
   state or configuration data are considered to be "well-behaved".
   Applications that work today through a NAT or NAPT device without
   application-specific support are also considered "well behaved".
   Such applications might use DNS FQDNs or application-specific
   name spaces. (Note Well: application-specific name spaces should
   not be derived from IP address values).

   For well-behaved applications, replacing IP with ILNP should have
   no impact. That is, well-behaved applications should work
   unmodified over ILNP.

   Those applications that use directly IP address values in
   application state or configuration will need to be modified for
   operation over ILNP. Examples of such applications include:

    - FTP: which uses IP address values in the application layer
      protocol.  In practice, use of Secure Copy (SCP) is growing,
      while use of FTP is either flat or declining, in part due
      to the improved security provided by SCP.

    - SNMP: which uses IP address values in MIB definitions, and
      values derived from IP address values in SNMP object names.

   Further experimentation in this area is planned to validate
   these details.


8.  SECURITY CONSIDERATIONS

   There are numerous security considerations for ILNP from an
   engineering viewpoint. Overall, ILNP functionality is no less
   secure than equivalent IP functionality. In some cases, ILNP has
   the potential to be more secure, or offer security capability in
   a more harmonised manner, for example with ILNP's use of IPsec in
   conjunction with multi-homing and mobility.  [ILNP-ARCH]
   describes several security considerations that apply to ILNP and
   is included here by reference.


8.1  Authenticating ICMP Locator Updates

   Separate documents propose a new IPv4 Option [ILNP-v4opts]
   and a new IPv6 Destination Option [ILNP-NONCE6]. Each of
   these options can be used to carry a session nonce end-to-end



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   between communicating nodes.  That nonce provides protection
   against off-path attacks on an Identifier/Locator session. The
   Nonce options are used ONLY for ILNP and not for IP. The nonce
   values are exchanged in the initial packets of an ILNP session
   by including them in those initial/handshake packets.

   When ILNP is in use, the Nonce Destination Option MUST be
   included in any ICMP control messages (e.g. ICMP Unreachable,
   ICMP Locator Update) sent by a correspondent node with regard to
   their ILNP sessions.  Note that in a small number of situations,
   a transit router or firewall legitimately might send an ICMP
   message (e.g. Packet Too Big) to an end system without including
   the ILNP Nonce.

   When using ILNP for an existing session, ICMP control messages
   for that session that are received from a correspondent node
   without a Nonce Destination Option MUST be discarded as
   forgeries. This security event SHOULD be logged.

   When using ILNP for an existing session, ICMP control messages
   received from a correspondent node that contain an ILNP Nonce
   option, but do not have the correct nonce value inside the Nonce
   Destination Option, MUST be discarded as forgeries. This security
   event SHOULD be logged.

   When using ILNP for an existing session, and a node changes its
   Locator set, it SHOULD include the Nonce Destination Option in
   the first few data packets sent using a new Locator value, so
   that the recipient can validate the received data packets as
   valid (despite having an unexpected Source Locator value).


8.2  Forged Identifier Attacks

   The ILNP Correspondent Cache contains two unidirectional nonce
   values (one used in control messages sent by this node, a
   different one used to authenticate messages from the other node)
   for each active or recent ILNP session. The correspondent cache
   also contains the currently valid set of Locators and set of
   Identifiers for each correspondent node.

   If a received ILNP packet contains valid Identifier values and a
   valid Destination Locator, but contains a Source Locator value
   that is not present in the correspondent cache, the packet MUST
   be dropped as an invalid packet and a security event SHOULD be
   logged, UNLESS the packet also contains a Nonce Destination
   Option with the correct value used for packets from the node with
   that Source Identifier to this node. This prevents an off-path



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   attacker from stealing an existing session.



9.  OPERATIONAL CONSIDERATIONS

   This section covers various operational considerations relating
   to ILNP, including potential session liveness and reachability
   considerations and Key Management considerations. Again, the
   situation is similar to IP, but it is useful to explain the
   issues in relation to ILNP nevertheless.


9.1  Session Liveness and Reachability

   For bi-directional flows, such as a TCP session, each node knows
   whether the current path in use is working by the reception of
   data packets, acknowledgements, or both. Therefore, as with
   TCP/IP, TCP/ILNP does not need special path probes. UDP/ILNP
   sessions with acknowledgements work similarly, and also do not
   need special path probes.

   In the deployed Internet, the sending node for a UDP/IP session
   without acknowledgements does not know for certain that all
   packets are received by the intended receiving node. Such
   UDP/ILNP sessions have the same properties as UDP/IP sessions in
   this respect. The receiver(s) of such an UDP/ILNP session SHOULD
   send a gratuitous IP packet containing an ILNP Nonce option to
   the sender, in order to enable the receiver to subsequently send
   ICMP Locator Updates if appropriate [ILNP-NONCE6]. In this case,
   UDP/ILNP sessions fare better than UDP/IP sessions, still without
   using network path probes.

   A mobile (or multi-homed) node may change its connectivity more
   quickly than DNS can be updated. This situation is unlikely,
   particularly given the widespread use of link-layer mobility
   mechanisms (e.g. GSM, IEEE 802 bridging) in combination with
   network-layer mobility. However, the situation is functionally
   equivalent to the situation where a traditional IP node is moving
   faster than the Mobile IPv4 or Mobile IPv6 agents/servers can be
   updated with the mobile node's new location.  So the issue is not
   new in any way to ILNP. In all cases, Mobile IPv4 and Mobile IPv6
   and ILNP, a node moving that quickly might be temporarily
   unreachable until it remains at a given network-layer location
   (e.g. IP subnetwork, ILNP Locator value) long enough for the
   location update mechanisms (for Mobile IPv4, for Mobile IPv6, or
   ILNP) to catch up.




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   Another potential issue for IP is what is sometimes called "Path
   Liveness" or, in the case of ILNP, "Locator Liveness". This
   refers to the question of whether an IP packet with a particular
   destination Locator value will be able to reach the intended
   destination network or not, given that some otherwise valid paths
   might be unusable by the sending node (e.g. due to security
   policy or other administrative choice). In fact, this issue has
   existed in the IPv4 Internet for decades.

   For example, an IPv4 server might have multiple valid IP
   addresses, each advertised to the world via an DNS A
   record. However, at a given moment in time, it is possible that a
   given sending node might not be able to use a given (otherwise
   valid) destination IPv4 address in an IP packet to reach that
   IPv4 server.

   Indeed, for ILNPv6, as the ILNP packet reuses the IPv6 packet
   header and uses IPv6 routing prefixes as Locator values, such
   liveness considerations are no worse than they are for IPv6
   today. For example, for IPv6, if a host, H, performs a DNS lookup
   for an FQDN for remote host F, and receives a AAAA RR with IPv6
   address F_A, this does not mean necessarily that H can reach F on
   its F_A using its current connectivity, i.e. an IPv6 path may not
   be available from H to F at that point in time.

   So we see that using an Identifier/Locator Split architecture
   does not create this issue, nor does it make this issue worse
   than it is with the deployed IPv4 Internet.

   In ILNP, the same conceptual approach described in [RFC5534]
   (Locator Pair Exploration for SHIM6) can be
   reused. Alternatively, an ILNP node can reuse the existing IPv4
   methods for determining whether a given path to the target
   destination is currently usable, for which existing methods
   leverage transport-layer session state information that the
   communicating end systems are already keeping for transport-layer
   protocol reasons.

   Lastly, it is important to note that the ICMP Locator Update
   mechanism described in [ILNP-ICMPv6] [ILNP-ICMPv4] is a
   performance optimisation, significantly shortening the
   network-layer handoff time if/when a correspondent changes
   location.  Architecturally, using ICMP is no different from
   using UDP, of course.

9.2  Key Management Considerations

   ILNP potentially has advantages over either form of Mobile IP



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   with respect to key management, given that ILNP is using Secure
   Dynamic DNS Update -- which capability is much more widely
   available today in deployed desktop and server environments
   (e.g. Microsoft Windows, MacOS X, Linux, other UNIX), as well as
   being widely available today in deployed DNS server software
   (e.g. Microsoft and the freely available BIND) and appliances
   [LA2006], than the Security enhancements needed by either Mobile
   IPv4 or Mobile IPv6.

   IETF work in progress is addressing use of DNS to support key
   management for entities having DNS Fully-Qualified Domain Names.


10. REFERRALS & APPLICATION PROGRAMMING INTERFACES

   This section is concerned with support for using existing
   ("legacy") applications over ILNP, including both referrals and
   Application Programming Interfaces (APIs).

   ILNP does NOT require well-behaved applications be modified to
   use a new networking API, nor does it require applications be
   modified to use extensions to an existing API. Existing
   well-behaved IP applications should work over ILNP without
   modification using existing networking APIs.

10.1 BSD Sockets APIs

   The existing BSD Sockets API can continue to be used with ILNP
   underneath the API. That API can be implemented in a manner that
   hides the underlying protocol changes from the applications. For
   example, the combination of a Locator and an Identifier can be
   used with the API in the place of an IPv6 address.

   So it is believed that existing IP address referrals can continue
   to work properly in most cases. For a rapidly moving target node,
   referrals might break in at least some cases. The potential for
   referral breakage is necessarily dependent upon the specific
   application and implementation being considered.

   It is suggested, however, that a new, optional, more abstract, C
   language API be created so that new applications may avoid
   delving into low-level details of the underlying network
   protocols. Such an API would be useful today, even with the
   existing IPv4 and IPv6 Internet, whether or not ILNP were ever
   widely deployed.


10.2 Java (and other) APIs



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   Most existing Java APIs already use abstracted network
   programming interfaces, for example in the java.Net.URL
   class. Because these APIs already hide the low-level
   network-protocol details from the applications, the applications
   using these APIs (and the APIs themselves) don't need any
   modification to work equally well with IPv4, IPv6, ILNP, and
   probably also HIP.

   Other programming languages, such as C++, python and ruby, also
   provide higher-level APIs that abstract away from sockets, even
   though sockets may be used beneath those APIs.


10.3 Referrals in the Future

   The approach proposed in [ID-Referral] appears to be very
   suitable for use with ILNP, in addition to being suitable for use
   with the deployed Internet. Protocols using that approach would
   not need modification to have their referrals work well with
   IPv4, IPv6, ILNP, and probably also other network protocols
   (e.g. HIP).

   A sensible approach to referrals is to use Fully-Qualified Domain
   Names (FQDNs), as is commonly done today with web URLs. This
   approach is highly portable across different network protocols,
   even with both the IPv4 Internet or the IPv6 Internet.


11.  IANA CONSIDERATIONS

   There are no IANA considerations.

   (The RFC Editor is requested to remove this section prior to
   publication.)

12.  REFERENCES

12.1 Normative References

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

   [RFC3007]    B. Wellington, "Secure Domain Name System
                Dynamic Update", RFC-3007, November 2000.

   [ILNP-ARCH]  R. Atkinson & S. Bhatti, "ILNP Architecture",
                draft-irtf-rrg-ilnp-arch, January 2012.



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

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

   [ILNP-ICMPv6]  R. Atkinson, "ICMPv6 Locator Update message"
                draft-irtf-rrg-ilnp-icmpv6, January 2012.

   [ILNP-NONCE6] R. Atkinson & S. Bhatti, "IPv6 Nonce Destination
                 Option for ILNPv6", draft-irtf-rrg-ilnp-nonce6,
                 January 2012.

   [ILNP-v4opts] R. Atkinson & S. Bhatti, "IPv4 Options for ILNP",
                 draft-irtf-rrg-ilnp-v4opts, January 2012.

12.2 Informative References


   [BA2011] S. Bhatti & R. Atkinson, "Reducing DNS Caching",
            Proc. GI2011 - 14th IEEE Global Internet Symposium.
            Shanghai, China. 15 April 2011.

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

   [PHG02]

   [SBK2002]

   [ID-Referral]

   [RFC3972]

   [RFC4291]

   [RFC4581]

   [RFC4941]

   [RFC4982]

   [RFC5534]

ACKNOWLEDGEMENTS




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   Steve Blake, Mohamed Boucadair, Noel Chiappa, Steve Hailes, Joel
   Halpern, Mark Handley, Volker Hilt, Paul Jakma, Dae-Young Kim,
   Tony Li, Yakov Rehkter, Robin Whittle and John Wroclawski (in
   alphabetical order) provided review and feedback on earlier
   versions of ILNP documents. Steve Blake provided an especially
   thorough review of an early version of the entire ILNP document
   set, which was extremely helpful. We also wish to thank the
   anonymous reviewers of the various ILNP papers for their
   feedback.

Author's Address

   RJ Atkinson
   Consultant
   San Jose, CA
   95125 USA

   Email:     rja.lists@gmail.com

   SN Bhatti
   School of Computer Science
   University of St Andrews
   North Haugh, St Andrews
   Fife, Scotland
   KY16 9SX, UK

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

   Expires: 09 JUL 2012






















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