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

            Optional Advanced Deployment Scenarios for ILNP
                     draft-irtf-rrg-ilnp-adv-06.txt

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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

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   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.

Abstract

   This document provides an Architectural description and the
   Concept of Operations of some optional advanced deployment
   scenarios for the Identifier-Locator Network Protocol (ILNP),
   which is an evolutionary enhancement to IP. None of the functions
   described here is required for the use or deployment of ILNP.
   Instead, it offers descriptions of engineering and deployment
   options that might provide either enhanced capability or
   convenience in administration or management of ILNP-based
   systems.


Table of Contents


     1. Introduction......................................?
     2. Localised Numbering...............................?
     3. An Alternative For Site Multi-Homing..............?
     4. An Alternative For Site (Network) Mobility........?
     5. Traffic Engineering Options.......................?
     6. ILNP in Datacentres ..............................?
     7. Location Privacy..................................?
     8. Identity Privacy..................................?
     9. Security Considerations...........................?
    10. IANA Considerations...............................?
    11. References........................................?

1. INTRODUCTION

   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



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   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.

   ILNP is, in essence, an end-to-end architecture: the
   functions required for ILNP are implemented in, and controlled
   by, only those end-systems that wish to use ILNP, as described
   in [ILNP-ARCH]. Other nodes, such as Site Border Routers (SBRs)
   need only support IP to allow operation of ILNP, e.g. an SBR
   should support IPv6 in order to enable end-systems to operate
   ILNPv6 within the site network for which an SBR provides a
   service [ILNP-ENG].

   However, some features of ILNP could be optimised, from an
   engineering perspective, by the use of an intermediate system (a
   router, security gateway or "middlebox") that modifies (rewrites)
   Locator values of transit ILNP packets. It would also perform
   other control functions for an entire site, as an administrative
   convenience, such as providing a centralised point of management
   for a site. For example, an SBR might manipulate the topological
   presence of the packet, providing an elegant solution to the
   provision of functions such as site (network) mobility for an
   entire end site [ABH09a].

   This document discusses several such optional advanced deployment
   scenarios for ILNP. These typically use an ILNP-capable Site
   Border Router (SBR).

   Nothing in this document is a requirement for any ILNP
   implementation or any ILNP deployment.

   Readers are strongly advised to first read the ILNP Architecture
   Description [ILNP-ARCH], as this document uses the notation and
   terminology described or referenced in that document.

1.1 Document roadmap

   This document describes engineering and implementation
   considerations that are common to both ILNPv4 and ILNPv6.

   The ILNP architecture can have more than one engineering
   instantiation. For example, one can imagine a "clean-slate"



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   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-ARCH] is the main architectural description of ILNP,
       including the concept of operations.

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

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

    d) [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.

    e) [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.

    f) [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.

    g) [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.

    h) [ILNP-ARP] describes extensions to ARP for use with ILNPv4.




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1.2 Terminology

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


2. LOCALISED NUMBERING

   Today, Network Address Translation [RFC3022] is used for a number
   of purposes. Whilst one of the original intentions of NAT was to
   reduce the rate of use of global IPv4 addresses, through use of
   IPv4 private address space [RFC1918], NAT also offers to site
   administrators a convenient localised address management
   capability combined with a local-scope/private address space,
   for example [RFC1918] for IPv4.

   For IPv6, NAT would not necessarily be required to reduce the
   rate of IPv6 address depletion, because the availability of
   addresses is not such an issue as for IPv4.  The IETF has
   standardised Unique Local IPv6 Unicast Addresses [RFC4193],
   which provide local-scope IPv6 unicast address space that can be
   used by end sites.  However, localised address management, in a
   manner similar to that provided by IPv4 NAT and private address
   space [RFC1918], is still desirable for IPv6 [RFC5902], even
   though there is debate about the efficacy of such an approach
   [RFC4864].

   One of the major concerns that many have had with NAT is the loss
   of end-to-end transport-layer and network-layer session state
   invariance, which is still considered an important architectural
   principle by the IAB [RFC4924].  Nevertheless, the use of
   localised addressing remains in wide use and there is interest in
   its continued use in IPv6, e.g.  proposals such as [RFC6296].

   It is possible to have the benefits of NAT-like functions for
   ILNP without losing end-to-end state. Indeed, such a mechanism -
   the use of Locator re-writing in ILNP - forms the basis of many
   of the optional functions described in this document. In ILNP,
   we call this feature "localised numbering".

   Recall, that a Locator value in ILNP has the same semantics as a
   routing prefix in IP: indeed, in ILNPv4 and ILNPv6 [ILNP-ENG],
   routing prefixes from IPv4 and IPv6, respectively, are used as
   Locator values.

   We note that a deployment using private/local numbering can also



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   provide a convenient solution to centralised management of site
   multi-homing and network mobility by deploying SBRs in this manner
   - this is described below.

   Please note that with this proposal, localised numbering (e.g.
   using the equivalent of IP NAT on the ILNP Locator bits) would
   work in harmony with multihoming, mobility (for individual hosts
   and whole networks), and IP Security, plus the other advanced
   functions described in this document [BA11] [LABH06] [ABH07a]
   [ABH07b] [ABH08a] [ABH08b] [ABH09a] [ABH09b] [RAB09] [RB10]
   [ABH10] [BAK11].


2.1 Localised Locators

   For ILNP, the NAT-like function can best be descried by using a
   simple example, based on Figure 2.1.

          site                         . . . .      +----+
         network        SBR           .       .-----+ CN |
         . . . .      +------+ L_1   .         .    +----+
        .       .     |      +------.           .
       .         .L_L |      |      .           .
       .         .----+      |      . Internet  .
       .  H      .    |      |      .           .
        .       .     |      |      .           .
         . . . .      +------+       .         .
                                      .       .
                                       . . . .

            CN = Correspondent Node
             H = Host
           L_1 = global Locator value
           L_L = local Locator value
           SBR = Site Border Router

        Figure 2.1: A simple localised numbering example for ILNP.

   In this scenario, the SBR is allocated global locator value L_1
   from the upstream provider. However, the SBR advertises internally
   a "local" Locator value L_L. By "local" we mean that the Locator
   value only has significance within the site network, and any
   packets that have L_L as a source Locator cannot be forwarded
   beyond the SBR with value L_L as the source Locator. In
   engineering terms, L_L would, for example in ILNPv6, be an IPv6
   prefix based on the assignments possible according to IPv6 Unique
   Local Addresses (ULA) [RFC4193].




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   We assume that H uses Identifier I_H then it will use
   Identifier-Locator Vector (IL-V) [I_H, L_L], and that the
   correspondent node (CN) uses IL-V [I_CN, L_CN]. If we consider
   that H will send a UDP packet from its port P_H to CN's port P_CN,
   then, H could send a UDP/ILNP packet with the tuple expression:

     <UDP: I_H, I_CN, P_H, P_CN><ILNP: L_L, L_CN>           --- (1a)

   When this packet reaches the SBR, it knows that L_L is a local
   Locator value and so re-writes the source Locator on the egress
   packet to L_1, and forwards that out onto its external-facing
   interface. The value L_1 is a global prefix, which allows the
   packet to be routed globally:

     <UDP: I_H, I_CN, P_H, P_CN><ILNP: L_1, L_CN>           --- (1b)

   This packet reaches CN using normal routing based on the Locator
   value L_1, as it is a routing prefix.

   Note that from expressions (1a) and (1b), the end-to-end state (in
   the UDP tuple) remains unchanged - end-to-end state invariance is
   honoured, for UDP. CN would send a UDP packet to H as:

     <UDP: I_CN, I_H, P_CN, P_H><ILNP: L_CN, L_1>           --- (2a)

   and the SBR would re-write the Locator value on the ingress packet
   before forwarding the packet on its internal interface:

     <UDP: I_CN, I_H, P_CN, P_H><ILNP: L_CN, L_L>           --- (2b)

   Again, this preserves the end-to-end transport-layer session
   state invariance.

   As the Locator values are not used in the transport layer pseudo
   header for ILNP [ILNP-ENG], the checksum would not have to be
   re-written. That is, the Locator re-writing function is stateless
   and has low overhead.

   (A discussion on the generation of Identifier values for initial
   use is presented in [ILNP-ENG].)

2.2 Mixed local/global numbering

   It is possible for the SBR to advertise both L_1 and L_L within
   the site, and for hosts within the site to have IL-Vs using both
   L_1 and L_L. For example, host H may have IL-Vs [I_H, L_1] and
   [I_H, L_L]. The configuration and use of such a mechanism can be
   controlled through local policy.



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2.3 Dealing with internal subnets with Locator re-writing

   Where the site network uses subnets, packets will need to be
   routed correctly, internally. That is, the site network may have
   several internal Locator values, e.g. L_La, L_Lb, and L_Lc. When
   an ingress packet has I-LV [I_H, L_1], it is expected that the
   SBR is capable of identifying the correct internal network for
   I_H, and so the correct Locator value to re-write for the ingress
   packet. This is not obvious as the I value and the L value are
   not related in any way.

   There are numerous ways the SBR could facilitate the correct
   lookup of the internal Locator value. This document does not
   prescribe any specific method. Of course, we do not preclude
   mappings directly from Identifier values to internal Locator
   values.

   Of course, such a "flat" mapping (between Identifier values and
   Locators) would serve, but maintaining such a mapping would be
   impractical for a large site. So, we propose the following
   solution.

   Consider that the Locator value, L_x consists of two parts, L_pp
   and L_ss, where L_pp is a network prefix and L_ss is a subnet
   selector. Also, consider that this structure is true for both
   the local identifier, L_L, as well as the global Identifier, L_1.
   Then an SBR need only to know the mapping from the values of L_ss
   as visible in L_1 and the values of L_ss used locally.

   Such a mapping could be mechanical, e.g. the L_ss part of L_L and
   L_1 are the same and it is only the L_pp part which is different.
   Where this is not desirable (e.g. for obfuscation of interior
   topology), an administrator would need to configure a suitable
   mapping policy in the SBR, which could be realised as a simple
   lookup table. Note that with such a policy, the L_pp for L_L and
   L_1 do not need to be of the same size.

   From a practical perspective, this is possible for both ILNPv6
   [RFC6177] and ILNPv4 [RFC4632]. For ILNPv6, recall that the
   Locator value is encoded to be syntactically similar to an IPv6
   address prefix, as shown in Figure 2.2, taken from [ILNP-ENG].

   /* IPv6 */
   | 3 |     45 bits         |  16 bits  |     64 bits             |
   +---+---------------------+-----------+-------------------------+
   |001|global routing prefix| subnet ID |  Interface Identifier   |
   +---+---------------------+-----------+-------------------------+




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   /* ILNPv6 */
   |             64 bits                 |     64 bits             |
   +---+---------------------+-----------+-------------------------+
   |          Locator (L64)              |  Node Identifier (NID)  |
   +---+---------------------+-----------+-------------------------+
   +<-------- L_pp --------->+<- L_ss -->+

     L_pp = Locator prefix part (assigned IPv6 prefix)
     L_ss = Locator subnet selector (locally managed subnet ID)

     Figure 2.2: IPv6 address format [RFC3587] as used in ILNPv6,
     showing how subnets can be identified.

   Note that the subnet ID forms part of the Locator value. Note
   also that [RFC6177] allows the global routing prefix to be more
   than 45 bits, and for the subnet ID to be smaller, but still
   preserving the 64-bit size of the Locator overall.

   For ILNPv4, the L_pp value overall is an IPv4 routing prefix,
   which is typically less than 32 bits. However, the ILNPv4 Locator
   value is carried in the 32-bit IP address space, so the bits not
   used for the routing prefix could be used for L_ss, e.g. for a
   /24 IPv4 prefix, the situation would be as shown in Fig 2.3, and
   L_ss could use any of the remaining 8-bits as required.

              24 bits           8 bits
     +------------------------+----------+
     |         Locator (L32)             |
     +------------------------+----------+
     +<------- L_pp --------->+<- L_ss ->+

     L_pp = Locator prefix (assigned IPv4 prefix)
     L_ss = Locator subnet selector (locally managed subnet ID)

     Figure 2.3: IPv4 address format for /24 IPv4 prefix, as used in
     ILNPv4, showing how subnets can be identified.

   As an example, for the case where the interior topology is not
   obfuscated, an interior "engineering" node might have an LP
   record pointing to eng.example.com and eng.example.com might have
   L32/L64 records for a specific subnet inside the site. Meanwhile,
   an interior "operations" node might have an LP record pointing at
   "ops.example.com" which might have different L32/L64 records for
   that specific subnet within the site. That is, eng.example.com
   might have Locator value L_pp_1:L_ss_1 and ops.example.com might
   have Locator value L_pp_1:L_ss_2. However, just as for IPv6 or
   IPv4 routing today, the routing for the site would only need to
   use L_pp_1, which is a routing prefix in either IPv6 (for ILNPv6)



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   or IPv4 (for ILNPv4).

2.4 Localised name resolution with DNS

   To support private numbering with IPv4 and IPv6 today, some sites
   use a split-horizon DNS service for the site [ID-appDNS].

   If a site using localised numbering chooses to deploy a
   split-horizon DNS server, then the DNS server would return the
   global-scope Locator(s) (L_1 in our example above) of the SBR to
   DNS clients outside the site, and would advertise the local-scope
   Locator(s) (L_L in our example above) specific to that internal
   node to DNS clients inside the site. Such deployments of
   split-horizon DNS servers are not unusual in the IPv4 Internet
   today. If an internal node (e.g. portable computer) moves outside
   the site, it would follow the normal ILNP methods to update its
   authoritative DNS server with its current Locator set. In this
   deployment model, the authoritative DNS server for that mobile
   device will be either the split-horizon DNS server itself or the
   master DNS server providing data to the split-horizon DNS server.

   If a site using localised numbering chooses not to deploy a
   split-horizon DNS server, then each internal nodes would
   advertise the global-scope Locator(s) of the site border routers
   in its respective DNS entries. To deliver packets from one
   internal node to another internal node, the site would either
   choose to use layer-2 bridging (e.g. IEEE Spanning Tree or IEEE
   Rapid Spanning Tree [IEEE04], or a link- state layer-2 algorithm
   such as the IETF TRILL group or IEEE 802.1 are developing), or
   the interior routers would forward packets up to the nearest site
   border router, which in turn would then rewrite the Locators to
   appropriate local-scope values, and forward the packet towards
   the interior destination node.

   Alternately, for sites using localised numbering but not
   deploying a split-horizon DNS server, the DNS server could return
   all global-scope and local-scope Locators to all queriers, and
   assume that nodes would use normal, local address/route selection
   criteria to choose the best Locator to use to reach a given
   remote node [RFC3484]. Hosts within the same site as the
   correspondent node would only have a ULA configured, and hence
   would select the ULA destination Locator for the correspondent
   (L_L in our example). Hosts outside the site would not have the
   same ULA configured (L_CN for the CN in our example). Note that
   RFC3484 probably needs to be updated to indicate that the
   longest-prefix matching rule is inadequate when comparing ULA-
   based Locators with global-scope Locators: to choose a ULA for a
   correspondent, a node must have a Locator that matches all ULA



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   bits of the target Locator value.

   Note that for split-horizon operation, there needs to be a DNS
   management policy for mobile hosts, as when such hosts are away
   from their "home" network, they will need to update DNS entries
   so that the global-scope Locator(s) only is (are) used, and these
   are consistent with the current topological position of the
   mobile host. Such updates would need to be done using Secure
   Dynamic DNS Update.

   For an ILNP mobile network using LP records, there are likely to
   separate LP records for internal and external use.


2.5 Use of mDNS

   Multicast DNS (mDNS) [ID-mDNS11] is popularly used in many end-
   system OSs today, especially desktop OSs (such as Windows, MacOSX
   and Linux). It is used for localised name resolution using names
   with a ".local" suffix, for both IPv4 and IPv6. This protocol
   would need to be modified so that when an ILNP-capable node
   advertises its ".local" name, another ILNP-capable node would be
   able to see that it is an ILNP-capable, but other, non-ILNP nodes
   would not be perturbed in operation. The details of a mechanism
   for using mDNS to enable such a feature are not defined here.


2.6 Site Network Name in DNS

   In this scenario, if H expects incoming ILNP session requests,
   for example, then remote nodes normally will need to look up
   appropriate Identifier and Locator information in the DNS. Just
   as for IP, and as already described in [ILNP-ARCH], a Fully
   Qualified Domain Name (FQDN) lookup for H should resolve to the
   correct NID and L32/L64 records.  If there are many hosts like H
   that need to keep DNS records (for any reason, including to allow
   incoming ILNP session requests), then, potentially, there are
   many such DNS Resource Records.

   As an optimisation, the network as a whole may be configured with
   one or more L32 and L64 records (to store the value L_1 from our
   example) that are resolved from an FQDN. At the same time,
   individual hosts now have an FQDN that returns one or more LP
   record entries [ILNP-DNS] as well as NID records. The LP record
   points to the L32 or L64 records for the site.  A multi-homed
   site normally will have at least one L32 or L64 record for each
   distinct uplink (i.e. link from a Site Border Router towards the
   global Internet), because ILNP uses provider-aggregatable



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   addressing.

   More than one L32 or L64 will be required if multiple Locator
   values are in use. For example, if an ILNPv6 site has multiple
   links for multi-homing, it will use one L64 record for each
   Locator value it is using on each link.


2.7  Site Interior Topology Obfuscation

   In some situations, it can be desirable to obfuscate the details
   of the interior topology of an end site. Alternately, in some
   situations, local site policy requires that local-scope routing
   prefixes be used within the local site. ILNP can provide these
   capabilities through the ILNP local addressing capability
   described here, under the control of the SBR.

   As described in Sec. 2.3 above, locator re-writing can be used to
   hid the internal structure of the network with respect to the
   sub-netting arrangement of the site network. Specifically, the
   procedure described in Sec 2.3 would be followed, with the
   following additional modification of the use of Locator values:

    (1) only the aggregated Locator value, i.e. L_pp, is advertised
        outside the site (e.g. in an L32 or L64 record), and L_ss is
        zeroed in that advertisement.

    (2) the SBR needs to maintain a mapping table to restore the
        interior topology information for received packets, for
        example by using a mapping table from I values to either
        L_ss values or to internal Locator values.

    (3) the SBR needs to zero the L_ss values for all Source Locators
        of egress packets, as well as performing an Locator re-writing
        effecting the L_pp bits of the Locator value.

   Of course, this only obscures the interior topology of the site,
   not the exterior connectivity of the site.  In order for the site
   to be reachable from the global Internet, the site's DNS entries
   need to advertise Locator values for the site to the global
   Internet (e.g. in L32, L64 records).


2.8 Other SBR considerations

   For backwards compatibility, for ILNP, the ICMP checksum is
   always calculated identically as for IPv6 or IPv4. For ILNPv6,
   this means that the SBR need not be aware if ILNPv6 is operating



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   as described in [ILNP-ARCH] and [ILNP-ENG]. For ILNPv4, again,
   the SBR need not be aware of the operation if ILNPv4 is operating
   as it will not need to inspect the extension header carrying the
   I value.

   In order to support communication between two internal nodes that
   happen to be using global-scope addresses (for whatever reason),
   the SBR MUST support the "hair pinning" behaviour commonly used
   in existing NAT/NAPT devices.  (This behaviour is described in
   Section 6 of RFC4787 [RFC4787].)

   In the near-term, a more common deployment scenario will be to
   deploy ILNP incrementally, with some ordinary classic IP traffic
   still existing. In this case, the SBR should maintain flow state
   that contains a flag for each flow indicating whether that flow
   is using ILNP or not. If that flag indicated ILNP were enabled
   for a given flow, and ILNP local numbering were also enabled,
   then the SBR would know that it should perform the simpler ILNP
   Locator re-writing mapping. If that flag indicated ILNP were not
   enabled for a given flow and IP NAT or IP NAPT were also enabled,
   then the SBR would know that it should perform the more complex
   NAT/NAPT translation (e.g. including TCP or UDP checksum
   recalculation).

       NOTE: Existing commercial security-aware routers
       (e.g. Juniper SRX routers) already can maintain flow state
       for millions of concurrent IP flows.  This feature would add
       one flag to each flow's state, so this approach is believed
       scalable today using existing commercial technology.

   Those applications that do not use IP address values in
   application state or configuration data are considered to be
   "well-behaved". For well-behaved applications, no further
   enhancements are required. Where application-layer protocols are
   not well-behaved, for example the File Transfer Protocol (FTP),
   then the SBR might need to perform additional stateful processing
   -- just as NAT and NAPT equipment needs to do today for FTP. See
   the description in Section 7.6 of [ILNP-ENG].

   When the SBR rewrites a Locator in an ILNP packet, that obscures
   information about how well a particular path is working between
   the sender and the receiver of that ILNP packet. So, the SBR that
   rewrites Locator values needs to include mechanisms to ensure
   that any packet with a new Destination Locator will travel along
   a valid path to the intended destination node. For ILNPv4, the
   path liveness will be no worse than IPv4, and mechanisms already
   in use for IPv4 can be re-used. For ILNPv6, the path liveness
   will be no worse than for IPv6, and mechanisms already in use for



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   IPv6 can be re-used.

   In the future, the Border Router Discovery Protocol (BRDP) also
   might be used in some deployments to indicate which routing
   prefixes are currently valid and which site border routers
   currently have a working uplink [ID-BRDP11].


3. AN ALTERNATIVE FOR SITE MULTI-HOMING

   The ILNP Architectural Description [ILNP-ARCH] describes the
   basic approach to enabling site multi-homing (S-MH) with ILNP.
   However, as an option, it is possible to leave the control of
   S-MH to an ILNP-enabled SBR. This alternative is based on the use
   of the Localised Numbering function described in Section 2 of
   this document.

3.1 Site multi-homing (S-MH) connectivity using an SBR

   The approach to Site Multi-Homing (S-MH) using an SBR is best
   illustrated through an example, as shown in Figure 3.1.

          site                         . . . .      +----+
         network         SBR          .       .-----+ CN |
         . . . .      +------+ L_1   .         .    +----+
        .       .     |  sbr1+------.           .
       .         .L_L |      |      .           .
       .         .----+      |      . Internet  .
       .  H      .    |      |      .           .
        .       .     |  sbr2+------.           .
         . . . .      +------+ L_2   .         .
                                     .       .
                                      . . . .

             CN = Correspondent Node
              H = Host
            L_1 = global Locator value 1
            L_2 = global Locator value 2
            L_L = local Locator value
            SBR = Site Border Router
           sbrN = interface N on SBR

      Figure 3.1: Alternative site multi-homing example with an SBR.

   The situation here is similar to the localised numbering example,
   except that the SBR now has two external links, with using
   locator value L_1 and another using Locator value L_2. These
   could, e.g. for ILNPv6, be separate, provider aggregated (PA)



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   IPv6 prefixes from two different ISPs. H has IL-V [I_H, L_L], and
   will forward a packet to CN as given in expression (1a). However,
   when the packet reaches the SBR, local policy will decide whether
   the packet is forwarded on the link sbr1 using L_1 or on sbr2
   using L_2. Of course, the correct Locator value will be re-
   written into the egress packet in place of L_L.

   If only local numbering is being used, then the SBR need never
   advertise any global Locator values. However, it could do, as
   described in Section 2.2.

3.2 Dealing with link/connectivity changes

   One of the key uses for multi-homing is providing resilience to
   link failure. If either link breaks, then the SBR can manage the
   change in connectivity locally. For example, assume SBR has been
   configured to use sbr1 for all traffic, and sbr2 only as backup
   link. So, SBR directs packets from H to communicate with CN using
   sbr1, and CN will receive packets as in expression (1b) and
   respond with packets as in expression (2a).

   However, if sbr1 goes down then SBR will move the communication
   to interface sbr2. As H is not aware of the actions of the SBR,
   the SBR must maintain some state about IL-V "pairs" in order
   hand-off the connectivity from sbr1 to sbr2. So, when moving the
   the communication to sbr2, the SBR would firstly send a Locator
   Update (LU) message [ILNP-ICMPv4] [ILNP-ICMPv6], to CN informing
   it that L_2 is now the valid Locator for the communication. This
   operation would not be visible to H, although there might be some
   disruption to transmission, e.g. packets being sent from CN to H
   that are in flight when sbr1 goes down may be lost. The SBR might
   also need to update DNS entries (see Section 3.3).  Since ILNP
   requires that all Locator Update messages be authenticated by the
   ILNP Nonce, the SBR will need to include the appropriate Nonce
   values as part of its cache of information about ILNP sessions
   traversing the SBR.  (NOTE: Since commercial security gateways
   available as of this writing reportedly can handle full stateful
   packet inspection for millions of flows at multi-gigabit speeds,
   it should be practical for such devices to cache the ILNP flow
   information, including Nonce values.)

   This approach has some efficiency gains over the approach for
   multi-homing described in [ILNP-ARCH], where each hosts manages
   its own connectivity.

   If sbr1 was to be re-instated, now with Locator value L_3, then
   local policy would determine if the communication should be moved
   back to sbr1, with appropriate additional actions, such as



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   transmission of LU messages with the new Locator values and also
   the updates to DNS.

   Note that in such movement of an ILNP session across interfaces
   at the SBR, only Locator values in ILNP packets are changed. As
   already noted in [ILNP-ARCH], end-to-end transport-layer session
   state invariance is maintained.

3.3 SBR updates to DNS

   When the SBR manages connectivity as described above, the internal
   hosts, such as H, are not necessarily aware of any connectivity
   changes. Indeed, there is certainly no requirement for them to be
   aware. So, if H was a server expecting incoming connections, the
   SBR must update the relevant DNS entries when the site
   connectivity changes.

   There are two possibilities: each host could have its own L32
   or L64 records; or the site might use a combination of LP and
   L32/L64 records (see Section 2.4). Either way, the SBR would need
   to update the relevant DNS entries. For our example, with ILNPv6
   and LP records in use, the SBR would need to manage two L64
   records (one for each uplink) which would resolve from
   a FQDN, for example, site.example.com. Meanwhile, individual
   hosts, such as H, have an FQDN which resolves to an NID value and
   an LP record that would contain the value site.example.com, which
   then would be used to lookup the two L64 records.

   If the SBR is multi-homed, as in Fig 3.1, then it will have (at
   least) two Locator values, one for each link, and local policy
   will need to be used to determine how preference values are
   applied in the relevant L32 and L64 records.


3.4 DNS TTL values for L32 and L64 records

   Imagine that in the scenario described above, there was a link
   failure that resulted in sbr1 going down and sbr2 was used.
   Existing ILNP sessions in progress would move to sbr2 as
   described above. However, new incoming ILNP sessions to the site
   would need to know to use L_2 and not L_1. L_1 and L_2 would be
   stored in DNS records (e.g. L32 for ILNPv4 or L64 for ILNPv6).
   If a remote host has already resolved from DNS that L_1 is the
   correct Locator for sending packets to the site, then that host
   might be holding stale information.

   DNS allows values returned to be aged using Time-To-Live (TTL)
   which is specified in the time unit of seconds. So that remote



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   nodes do not hold on to stale values from DNS, the L64 records for
   our site should have low TTL values. An appropriate value must be
   considered carefully. For example, let us assume that the site
   administrator knows that when sbr1 fails, it takes 20 seconds to
   failover to sbr2. Then, 20s would seem to be an appropriate time
   to use for the TTL value of an L64 for the site: if a remote node
   had just resolved the value L_1 for the site, and the link to sbr1
   went down, that remote node would not hold the stale value of L_1
   for any longer than it takes the site to failover to sbr2 and use
   L_2.

   Our studies for a university School site network show that low TTL
   values, as low as zero, are feasible for operational use [BA11].

   NOTE: From 01 Nov 2010, the site network of the School of Computer
         Science, University of St Andrews, UK, has been running
         operational DNS with DNS A records that have TTL of zero.
         At the time of writing of this note (05 Jan 2011),
         a zero DNS TTL was still in use at the school.


3.5 Multiple SBRs

   For site multi-homing, with multiple SBRs, a situation may be as
   follows (see also Sec 5.3.1 in [ILNP-ARCH]).

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




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         CP     = coordination protocol
         L_1    = global Locator value 1
         L_2    = global Locator value 2
         SBR_A  = Site Border Router A
         SBR_B  = Site Border Router P

     Figure 3.2: 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 3.1. 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 functions are available today in
   some commercial network security products. Note that, logically,
   there is little difference between Fig 5.1 and Fig 3.2, but with
   two distinct routers in Fig 3.2, the interaction using CP is
   required. Of course, it is also possible to have multiple
   interfaces in each router and more than two routers.


4. AN ALTERNATIVE FOR SITE (NETWORK) MOBILITY

   The ILNP Architectural Description [ILNP-ARCH] describes the basic
   approach to enabling site (network) mobility with ILNP. However,
   as an option, it is possible to leave the control of site mobility
   to an ILNP-enabled SBR by exploiting the alternative site
   multi-homing feature described in Section 3 of this document.

   Again, as described in [ILNP-ARCH], we exploit the duality between
   mobility and multi-homing for ILNP.

4.1 Site (network) mobility

   Let us consider the mobile network in Figure 4.2, which is taken
   from [ILNP-ARCH].

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

       Figure 4.1a: ILNP mobile network before handover.

          site                        ISP_1



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         network        SBR           . . .
         . . . .      +------+ L_1   .     .
        .       . L_L |   ra1+------. . . . .
       .         .----+      |      .       .
        .  H    .     |   ra2+------.       .
         . . . .      +------+ L_2  . . . . .
                                     .     .
                                      . . .
                                      ISP_2

       Figure 4.1b: ILNP mobile network during handover.

          site                        ISP_2
         network        SBR           . . .
         . . . .      +------+       .     .
        .       . L_L |   ra1+--    .       .
       .         .----+      |      .       .
        .  H    .     |   ra2+------.       .
         . . . .      +------+ L_2   .     .
                                      . . .

       Figure 4.1c: ILNP mobile network after handover.

            H = host
          L_1 = global Locator value 1
          L_2 = global Locator value 2
          L_L = local Locator value
          raN = radio interface N
          SBR = Site Border Router

     Figure 4.1: An alternative mobile network scenario with an SBR.

   We assume that the site (network) is mobile, and the SBR has two
   radio interfaces ra1 and ra2. In the figure, ISP_1 and ISP_2 are
   separate, radio-based service providers, accessible via interfaces
   ra1 and ra2.

   While the SBR makes the transition from using a single link (Fig.
   4.1a) to the hand-over overlap on both links (Fig 4.1b), to only
   using a single link again (Fig 4.1c), the host H continues to use
   only Locator value L_L, as already described for site multi-homing
   (S-MH). During this time the actions taken by the SBR are the same
   as already described in [ILNP-ARCH], except that the SBR:

      a) also performs that ILNP localised numbering function
         described in Section 2.
      b) does not need to advertise L_1 and L_2 internally if only
         local numbering is being used.



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   As for the case of S-MH above, H need not be aware of the change
   in connectivity for the SBR if it is only using local numbering,
   and the SBR would send LU messages for H (for any correspondent
   nodes, not shown in Fig 4.1), and would update DNS entries as
   required.

   The difference to the S-MH scenario described earlier in this
   document is that in the situation of Fig 4.1b, the SBR can opt to
   use soft handover has previously described in [ILNP-ARCH].

   Again, there is an efficiency gain compared to the situation
   described in [ILNP-ARCH]: the SBR provides a convenient point at
   which to centrally manage the movement of the site as a whole.
   Note that in Fig 4.1b, the site is multi-homed.

   As for S-MH, L_1 and L_2 could be advertised internally, as a
   local policy decision, for those hosts that require direct control
   of their connectivity.

   Note that for handover, immediate handover will have a similar
   behaviour to a link outage as described for S-MH. However, as ILNP
   allows soft-handover, during the handover period, this should help
   to reduce (perhaps even remove) packet loss.

4.3 SBR updates to DNS

   As for S-MH, a similar discussion to Section 3.3 applies for
   mobile networks with respect to the updates to DNS. As a mobile
   network is likely to have more frequent changes to its
   connectivity than a multi-homed network would due to connectivity
   changes, the use of LP DNS records is likely to be particularly
   advantageous here.


4.4 DNS TTL values for L32 and L64 records

   As for S-MH, a similar discussion to Section 3.4 applies for
   mobile networks with respect to the TTL of L32 and/or L64 records
   that are used for the name of the mobile network. In the case of
   the mobile network, it makes sense for the TTL to be aligned to
   the time for handover.


5. TRAFFIC ENGINEERING OPTIONS

   The use of Locator re-writing provides some simple yet useful
   options for traffic engineering (TE) controlled from the edge-site
   via the SBR, requiring no cooperation from the service provider



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   other than the provision of basic connectivity services, e.g.
   physical connectivity, allocation of IP address prefixes and
   packet forwarding. This does not preclude other TE options that
   are already in use, such as use of MPLS, but we choose to
   highlight here the specific options available and controllable
   solely through the use of ILNP.

   When a site network is multi-homed, we have seen that the use of
   the Locator re-writing function permits the SBR to have
   packet-by-packet control when forwarding on external links.
   Various configuration and policies could be applied at the SBR in
   order to control the egress and ingress traffic to the site
   network.

5.1 Load balancing

   Let us consider Figure 5.1, and assume ILNP local numbering is in
   use; that H1, H2 and H3 use, respectively, Identifier values, I_1,
   I_2 and I_3; and all of them use Locator value L_L.


           site                         . . . .
          network         SBR          .       .
          . . . .      +------+ L_1   .         .
         .       .     |  sbr1+------.           .
        .     H2  .L_L |      |      .           .
        . H3      .----+      |      . Internet  .
        .         .    |      |      .           .
         .  H1   .     |  sbr2+------.           .
          . . . .      +------+ L_2   .         .
                                       .       .
                                        . . . .

            HN = host N
           L_1 = global Locator value 1
           L_2 = global Locator value 2
           L_L = local Locator value
           SBR = Site Border Router
          sbrN = interface N on sbr

      Figure 5.1: A site multi-homing scenario for traffic control.

   The SBR could be configured, subject to local policy, to try to
   control load across the external links. For example, it could be
   configured initially with the following mappings:

     srcI=I_1, sbr1                                        --- (3a)
     srcI=I_2, sbr2                                        --- (3b)



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     srcI=I_3, sbr1                                        --- (3c)

   These mappings direct packets matching course Identifier values
   to particular outgoing interfaces. As load changes, these
   mappings could be changed. For example, expression (3c) could be
   changed to:

     srcI=I_3, sbr2                                        --- (4)

   and the SBR would need to send LU message to the correspondents of
   H3 (sbr to uses L_2 while sbr1 uses L_1). The egress connectivity
   is totally within control of the SBR under administrative policy,
   as already seen in the descriptions of multi-homing and mobility
   in this document.

   Of course, more complex policies are possible, based on:

    - whether ILNP sessions are incoming or outgoing
    - time of day
    - internal subnets

   and any number of criteria already in use for control of traffic.

   In expressions (3a,b,c) above, source I values are used. However:

    - destination I values could be used
    - source or destination L values could be used
    - mappings could be to L values, not to specific interfaces

   and, again, any number of criteria could be used to manipulate
   the packet path, based on filtering of values in header fields
   and local policy.

   With ILNP, hosts do not need to be aware of the operation of the
   SBR in this manner.

   Note, again, that in this scenario, there is nothing to prevent
   SBR from also advertising L_1 and L_2 into the site network. If
   required, administrative controls could be used to enable
   selective hosts in the site network to use L_1 and L_2 directly as
   described in [ILNP-ARCH].

5.2 Control of egress traffic paths

   Extending the scenario for load-balancing described above, it is
   also be possible for the ILNP-capable SBR to direct traffic along
   specific network paths based on the use of different L values,
   i.e. by using multiple prefixes assigned from upstream providers.



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   Of course, as previously discussed, these prefixes can be Provider
   Aggregated (PA) and need not be Provider Independent (PI).

   Let us consider Figure 5.2, and assume ILNP local numbering is in
   use; that H1, H2 and H3 use, respectively, Identifier values, I_1,
   I_2 and I_3; and all of them use Locator value L_L. Let us also
   assume that the node CN uses IL-V [I_CN, L_CN].

           site                           . . . .      +----+
          network         SBR            .       .-----+ CN |
          . . . .      +------+ L1,L2   .         .    +----+
         .       .     |  sbr1+--------.           .
        .     H2  .L_L |      |        .           .
        . H3      .----+  sbr2+--------. Internet  .
        .         .    |      | L3,L4  .           .
        .         .    |      |        .           .
         .  H1   .     |  sbr3+--------.           .
          . . . .      +------+ L5,L6   .         .
                                         .       .
                                          . . . .

            CN = correspondent node
            HN = host N
            LN = global Locator value N
           L_L = local Locator value
           SBR = Site Border Router
          sbrN = interface N on sbr

      Figure 5.2: A site multi-homing scenario for traffic control.

   Here, many configurations are possible. For example, for egress
   traffic:

     srcI=I_2, L2                                          --- (5a)
     srcI=I_3, L3                                          --- (5b)
     dstI=I_CN, L6                                         --- (5c)
     srcI=I_1 dstI=I_CN, L1                                --- (5d)

   Expression (5a) maps all egress packets from H2 to have their
   source Locator value re-written to L2 (and implicitly to use
   interface sbr1). Expression (5b) maps all egress packets from H3
   to have their source Locator value re-written to L3 (and
   implicitly to use interface sbr2). Expression (5c) directs ay
   traffic to CN to use Locator value L6 as the source Locator (and
   implicitly to use interface sbr3), and may override (5a) and (5b),
   subject to local policy, when packets to CN are from H2 or H3.

   Meanwhile, in expression (5d), we see a further, more specific



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   rule, in that packets from H1 destined to CN should use Locator
   value L1 (and implicitly to use interface sbr1).

   Note the implicit bindings to interfaces in expressions
   (5a,b,c,d), compared to the explicit bindings in expressions
   (3a,b,c). ILNP only requires that the Locator values are correctly
   re-written and packets forwarded in conformance with the routing
   already configured for the Locator values.

   Of course, these rules can be changed dynamically at the SBR, and
   the SBR will migrate ILNP sessions across Locator values, as
   already described above for mobility.


6. ILNP IN DATACENTRES

   As ILNP has first class support for mobility and multi-homing,
   and supports flexible options for localised addressing, there is
   great potential for it to be used in datacentre scenarios. Further
   details of possibilities are in [BA12], with a summary presented
   here.

   There are several scenarios that could be beneficial to
   datacentres, in order to provide functions such as load
   balancing, resilience and fault tolerance, and resource
   management:

   - Same datacentre, internal VM mobility: This could be beneficial
     in load balancing, dynamically, where load changes are taking
     place. The remote user does not see the VM has moved.

   - Different datacentres, transparent mobility: This is where the
     datacentre resources may be geographically distributed, but
     the geographical movement is transparent to the remote user.

   - Different datacentres, mobility is visible: This is where the
     datacentre resources may be geographically distributed, but
     the geographical movement is visible to the remote user.

   These are three situations which may be supported by ILNP, but
   they are not the only ones: we provide these here as examples,
   and they are not intended to be prescriptive. The intention is
   only to show the flexibility that is possible through the use of
   ILNP.

   This section describes some Virtual Machine (VM) mobility
   capabilities that are possible with ILNP. Depending on the
   internal details and virtualisation model provided by a VM



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   platform, it might be sufficient for the guest operating system
   to support ILNP. In a some cases, again depending on the internal
   details and virtualisation model provided by a VM platform, the
   VM platform itself also might need to include support for ILNP.

   Details of how a particular VM platform works, and which
   virtualisation model(s) a VM platform supports, are beyond the
   scope of this document. Internal implementation details of VM
   platform support for ILNP are also beyond the scope of this
   document, just as internal implementation details for any other
   networked system supporting ILNP are beyond the scope of this
   document.


6.1 Virtual image mobility within a single datacentre

   Let us consider first the scenario of Figure 6.1, noting its
   similarity to Figure 2.1 for use of localised numbering.

          site                         . . . .      +----+
         network        SBR           .       .-----+ CN |
         . . . .      +------+ L_1   .         .    +----+
        .       .     |      +------.           .
       .    H2   .L_L |      |      .           .
       .         .----+      |      . Internet  .
       .  V*H1   .    |      |      .           .
        .       .     |      |      .           .
         . . . .      +------+       .         .
                                      .       .
                                       . . . .

            CN = Correspondent Node
             V = Virtual machine image
            Hx = Host x
           L_1 = global Locator value
           L_L = local Locator value
          SBR = Site Border Router

     Figure 6.1: A simple virtual image mobility example for ILNP.

   L_L is a Locator value used for the ILNP hosts H1 an H2. Here,
   the "V*H1" signifies that the virtual machine image V is
   currently resident on H1. Let us assume that V has Identifier
   I_V. Note that as H1 and H2 have the same Locator value (L_1), as
   far as CN is concerned, it does not matter if V is resident on H1
   or H2, all transport packets between V and CN will have the same
   signature as far as CN is concerned, e.g. for a UDP flow (in
   analogy to (1a)):



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     <UDP: I_V, I_CN, P_V, P_CN><ILNP: L_1, L_CN>           --- (6a)

   Now, if V was to migrate to H2, the migration would be an issue
   purely local to the site-network, and the end-to-end integrity of
   the transport flow would be maintained.

   Of course, there are practical operating systems issues in
   enabling such a migration locally, but products exist today that
   could be modified and made ILNP-aware in order to enable such VM
   image mobility.

   Note that for convenience, above, we have used localised
   numbering for ILNP, but if local Locator values were not used and
   the whole site simply used L_1, the principle would be the same.

6.2 Virtual image mobility between data centres - invisible

   Let us now consider an extended version of the scenario above in
   Fig. 6.2, where we see that there is a second site network, which
   is geographically distant to the first site network, and the two
   site networks are interconnected via their respective SBRs.

          site                         . . . .      +----+
         network 1      SBR1          .       .-----+ CN |
         . . . .      +------+ L_1   .         .    +----+
        .       .     |      +------.           .
       .         .L_L1|      |      .           .
       .         .----+      |      . Internet  .
       .  V*H1   .    |      |      .           .
        .       .     |      |      .           .
         . . . .      +---+--+      .           .
                          :         .           .
                          :         .           .
         . . . .      +---+--+ L_2  .           .
        .       .     |      +------.           .
       .    H2   .L_L2|      |      .           .
       .         .----+      |      .           .
       .         .    |      |      .           .
        .       .     |      |      .           .
         . . . .      +------+       .         .
          site          SBR2          .       .
         network 2                     . . . .


             : = logical inter-router link and coordination
            CN = Correspondent Node
             V = Virtual machine image
            Hx = Host x



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           L_y = global Locator value y
          L_Lz = local Locator value z
          SBR = Site Border Router

     Figure 6.2: A simple localised numbering example for ILNP.

   Note that the logical inter-router link between SBR1 and SBR2
   could be realised physically in many different ways that are
   available today and are not ILNP specific, e.g. leased line,
   secure IP-layer or layer-2 tunnel, etc. We assume that this link
   also allows coordination between the two SBRs. For now, we ignore
   external link L_2 on SBR2, and assume that the remote node, CN,
   is in communication with V through SBR1.

   When in initial communication, the packets have the signature is
   given in expression (6a). When V moves to H2, it now uses Locator
   value L_L2, but all communication between V and CN is still
   routed via SBR1. So, the remote CN still sees that same packet
   signature as given in expression (6a). L_L1 and L_L2 are,
   effectively, two internal (private) subnetworks, and are not
   visible to CN.

   However, SBR2 and SBR1 must coordinate so that any further
   communication to V via SBR1 is routed across the inter-router
   link. Again, there are commercial products today that could be
   adapted to manage such shared state.

6.3 Virtual image mobility between data centres - visible

   Clearly, in the scenario of the section above, once V has moved
   to site network 2, it may be beneficial, for a number of reasons,
   for communication to V to be routed via SBR2 rather than SBR1.

   When V moves from site network 1 to site network 2, this
   visibility of mobility could be by V sending ILNP Locator Update
   messages to the CN during the mobility process. Also, V would
   update any relevant ILNP DNS records, such as L64 records, for
   new ILNP session requests to be routed via SBR2.

   Indeed, let us now consider again Fig 6.2, and assume now that
   Local locators L_L1 and L_L2 are not in use on either site
   network, and each site networks uses its own global Locator
   value, L_1 and L_2, respectively, internally. In that case, the
   packet flow signature for V when it is in site network 1 as
   viewed from CN is, again as given in expression (6a). However,
   when V moves to site network 2, it would simply use L_2 as its
   new Locator, send Locator Update messages to CN as would a normal
   mobile node for ILNP, and complete its migration to H2. Then, CN



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   would see the packet signatures as in expression (6b).

     <UDP: I_V, I_CN, P_V, P_CN><ILNP: L_2, L_CN>           --- (6b)

   In this case, no "special" inter-router link is required for
   mobility - the normal Internet connectivity between SBR1 and SBR2
   would suffice. However, it is quite likely that some sort of
   tunnelled link would still be desirable to offer protection of
   the VM image as it migrates.

6.4 ILNP capability in the remote host for VM image mobility

   For the remote host - the correspondent node (CN) - the
   availability of ILNP would be beneficial. However, for the first
   two scenarios listed above, as the packet signature of the
   transport flows remains fixed from the viewpoint of the CN, it
   seems possible that the benefits of ILNP VM mobility could be
   used for datacentres even while CNs remain as normal IP hosts.
   Of course, a major caveat here is that the application level
   protocols should be "well-behaved": that is, the application
   protocol or configuration should not rely on the use of IP
   addresses.


7.  LOCATION PRIVACY

   Extending the Locator re-writing paradigm, it is possible to also
   enable Location privacy for ILNP by a modified version of the
   "onion routing" paradigm that is used for Tor [DMS04] [RSG98].

7.1 Locator Re-writing Relay (LRR)

   To enable this function, we use a middlebox which we call the the
   Locator Re-writing Relay. The function of this unit is described
   by the use of Figure 7.1.

      <UDP: I_H, I_CN, P_H, P_CN><ILNP: L_1, L_CN>         --- (7a)

              v
              |
           +--+--+
           |     |   src=[I_H, L_1], L_X                   --- (7b)
           | LRR |   dst=[I_H, L_X], L_1                   --- (7c)
           |     |
           +--+--+
              |
              v




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      <UDP: I_H, I_CN, P_H, P_CN><ILNP: L_X, L_CN>         --- (7d)

        LRR = Locator Re-writing Relay

     Figure 7.1: Locator Re-Writing Relay (LRR) example

   The operation of the LRR is conceptually very simple. We assume
   that the LRR first has mappings as given in expressions (7b) and
   (7c) (see next sub-section). Expression (7b) says that for
   packets with src IL-V [I_H, L_1], the packet's source Locator
   value should be re-written to value L_X and then forwarded.
   Expression (7c) has the complimentary mapping for packets with
   destination IL-V [I_H, L_1] (for the reverse direction).

   Expression (6a) is a UDP/ILNP packet as might be sent in Figure
   2.1 from H to CN. However, instead of going directly to L_CN, the
   packet with destination Locator L_1 goes to a LRR. Expression
   (7d) is the result of the mapping of packet (7a) using expression
   (7b).

   Note that it is entirely possible that the packet of expression
   (7d) then is processed by another LRR for source Locator value
   L_X. Effectively, this creates and LRR path for the packet, as an
   overlay path on top of the normal IP routing.

   In this way, there is a level of protection, without the need for
   cryptographic techniques, for the (topological) Location of the
   packet. Of course, an extremely well-resourced adversary could,
   potentially, backtrack the LRR path, but, depending on the LRR
   overlay path that is created, could be very difficult to trace in
   reality. For example, the mechanism will protect against off-path
   attacks, but where the threat regime includes the potential for
   on-path attacks, cryptographically protected tunnels between H
   and LRR might be required.

   Again, as the Locator value is not part of the end-to-end state,
   this mechanism is very general and has a low overhead.

   7.2 Options for installing LRR packet forwarding state

   There are many options for managing the "network" of LRRs that
   could be in place if such a system was used on a large scale,
   including the setting up and removal of LRR state for packet
   relaying, as for expressions (7b) and (7c). We consider this
   function to be outside the scope of these ILNP specifications,
   but note that there are many existing mechanisms that could
   modified for use, and also many possibilities for new mechanisms
   that would be specific to the use of ILNP LRRs.



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   (Note also that the control/management communication with the LRR
   does not need to use ILNP: IPv4 or IPv6 could be used.)

   The host, H, by itself could install the required state, assuming
   it was aware of suitable information to contact the LRR.  The
   first packet in an ILNP session might contain a header option
   called a Locator Redirection Option (LRO). The LRO would contain
   the Locator value that should be re-written into the source
   Locator of the packet. When a LRR receives such a packet, it
   would install the required state. Such a mechanism could be soft-
   state, requiring periodic use of the LRO in order to maintain the
   state in the LRR. The LRO could also be delivered using an ICMP
   ECHO packet sent from H to the LRR, periodically, again to
   maintain a soft-state update.

   It would, of course, be prudent to protect the LRR state control
   packets with some sort of authentication token, to prevent an
   adversary from easily installing false LRR state and causing packets
   from H or its correspondent to be subject to man-in-the-middle
   attacks, or black-holing. Again, such attacks are not specific
   to ILNP or new to ILNP.

   It would also be possible to use proprietary application level
   protocols, with strong authentication for the control of the LRR
   state. For example, an application level protocol based on XMPP
   (http://xmpp.org/) operating over SSL.

   Above, we have offered very brief and incomplete descriptions of
   some possibilities, and we do not necessarily mandate any one of
   them: they serve only as examples.


8. IDENTITY PRIVACY

   For the sake of completeness, and in complement to Section 6, it
   should be noted that ILNP can use either cryptographically
   verifiable Identifier values, or use Identifier values that
   provide a level of anonymity to protect a user's privacy. More
   details are given in Section 2 and 11 of [ILNP-ENG].


9. SECURITY CONSIDERATIONS

   The relevant security considerations to this document are
   the same as for the main ILNP Architectural Description
   [ILNP-ARCH]. The one additional point to note is that this
   document describes ILNP capability in the SBR and so those
   adversaries wishing to subvert the operation of ILNP



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   specifically, have a target that would, potentially, disable
   an entire site. However, this is not an attack vector that is
   specific to ILNP: today, disruption of an IPv4 or IPv6 SBR
   would have the same impact.

   The security considerations for Section 7 (Location Privacy) are
   already documented in [DMS04] and [RSG98]. One possibility is
   that the LRR mechanism itself could be used by an adversary to
   launch an attack and hide his own (topological) Location, for
   example. This is already possible for IPv4 and IPv4 with a
   Tor-like system today, so is not new to ILNP.


10.  IANA Considerations

       There are no IANA considerations for this document.
       (Note to RFC Editor: please remove this section
        prior to publication.)

11.  REFERENCES

11.1.  Normative References

   [RFC1918]     Y. Rekther, B. Moskowitz, D. Karrenberg & G. J.
                 de Groot,
                 "Address Allocation for Private Internets",
                 RFC1918, Feb 1996

   [RFC2119]     S. Bradner, "Key Words for Use in RFCs to
                 Indicate Requirement Levels", RFC2119,
                 March 1997.

   [RFC3022]     P. Srisuresh & K. Egevang,
                 "Traditional IP Network Address Translator
                 (Traditional NAT)",
                 RFC3022, Jan 2011.

   [RFC3484]     R. Draves, "Default Address Selection for IPv6",
                 RFC3484, Feb 2003.

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

   [RFC4632]     V. Fuller and T. Li, "Classless Inter-domain
                 Routing (CIDR): The Internet Address Assignment and
                 Aggregation Plan", RFC4632, August 2006.

   [RFC4787]     F. Audet & C. Jennings, "NAT Behavioural



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                 Requirements for Unicast UDP", RFC4787,
                 January 2007.

   [RFC4864]     G. Van de Velde, T. Hain, R. Droms, B. Carpenter &
                 E. Klein,
                 "Local Network Protection for IPv6",
                 RFC4864, May 2007

   [RFC4924]     B. Adoba & E. Davbies (eds),
                 "Reflections on Internet Transparency",
                 RFC4924, Jul 2007

   [RFC5902]     D. Thaler, L. Zhang & G. Lebovitz,
                 "IAB Thoughts on IPv6 Network Address Translation",
                 RFC5902, Jul 2010

   [RFC6177]    T. Narten, G. Huston, L. Roberts, "IPv6 Address
                Assignment to End Sites", RFC6177 (BCP157), March
                2011.

   [ILNP-ARCH]    R.J. Atkinson & S.N. Bhatti,
                  "ILNP Architectural Description",
                  draft-irtf-rrg-ilnp-arch, 10 July 2012.

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

   [ILNP-v4OPTS] R.J. Atkinson & S.N. Bhatti,



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                 "IPv4 Options for ILNP",
                 draft-irtf-rrg-ilnp-v4opts, 10 July 2012.

11.2.  Informative References

   [ABH07a]    R. Atkinson, S. Bhatti, & S. Hailes,
               "Mobility as an Integrated Service Through the Use of
               Naming", Proceedings of ACM Workshop on Mobility
               in the Evolving Internet Architecture (MobiArch),
               ACM SIGCOMM, Kyoto, Japan. 27 Aug 2007.

   [ABH07b]    R. Atkinson, S. Bhatti, & S. Hailes,
               "A Proposal for Unifying Mobility with Multi-Homing,
               NAT, & Security", Proceedings of 2nd ACM Workshop on
               Mobility Management and Wireless Access (MobiWAC),
               ACM, Chania, Crete. Oct 2007.
               ISBN: 978-1-59593-809-1

   [ABH08a]    R. Atkinson, S. Bhatti, & S. Hailes,
               "Mobility Through Naming: Impact on DNS", Proceedings
               of 3rd ACM Workshop on Mobility in the Evolving
               Internet Architecture (MobiArch), ACM SIGCOMM,
               Seattle, WA, USA. Aug 2008.

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

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

   [ABH09b]    R. Atkinson, S. Bhatti, S. Hailes,
               "ILNP: Mobility, Multi-Homing, Localised Addressing and
               Security Through Naming"", Telecommunication Systems,
               vol. 42, no. 3-4, pp273-291, Springer-Verlag, Dec 2009.

   [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, pp1319-1325, IEEE, Oct 2010.

   [BA11]      S. Bhatti & R. Atkinson,
               "Reducing DNS Caching", Proceedings of IEEE



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               Global Internet Symposium (GI2011), Shanghai,
               P.R. China. 15 Apr 2011.

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

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

   [DMS04]     R. Dingledine, N. Mathewson, & P. Syverson,
               "Tor: the second-generation onion router",
               Proceedings of 13th USENIX Security Symposium, USENIX
               Association, San Diego, CA, USA. 2004.

   [ID-appDNS] O. Kolman, J. Peterson, H. Tschofenig & B. Aboba,
               "Architectural Considerations on Application Features
               in the DNS", draft-iab-dns-applications, March 2012.

   [ID-BRDP11] T. Boot & A. Holtzer, "Border Router Discovery
               Protocol (BRDP) Framework",
               draft-boot-brdp-framework-00, Internet-Draft,
               31 Jan 2011.

   [ID-mDNS11] S. Cheshire, M. Krochmal, "Multicast DNS",
               draft-cheshire-dnsext-multicastdns-15, 09 Dec 2011.

   [IEEE04]    "IEEE 802.1D - IEEE Standard for Local and Metropolitan
               Area Networks, Media Access Control (MAC) Bridges",
               IEEE Standards Association, New York, NY, USA, 9 June
               2004.
               Print: ISBN 0-7381-3881-5 SH95213
               PDF: ISBN 0-7381-3982-3 SS95213

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

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




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   [RB10]      D. Rehunathan, S. Bhatti,
               "A Comparative Assessment of Routing for Mobile
               Networks", Procedings of 6th IEEE International
               Conference on Wireless and Mobile Computing
               Networking and Communications (WiMob), IEEE, Niagara
               Falls, ON, Canada. Oct 2010.

   [RSG98]     Michael G. Reed, Paul F. Syverson, and David
               M. Goldschlag, "Anonymous Connections and
               Onion Routing", IEEE Journal on Selected Areas
               in Communications, Vol. 16, No. 4, IEEE,
               Piscataway, NJ, USA, May 1998.

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

   [RFC6296]   W. Wasserman, F. Baker, "IPv6-to-IPv6 Network Prefix
               Translation", RFC6296, June 2011.

ACKNOWLEDGEMENTS

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

   Roy Arends provided expert guidance on technical and procedural
   aspects of DNS issues.

RFC EDITOR NOTE

   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
   RFC-5887.

   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.



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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: 10 JAN 2013































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