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Internet Draft                                          R. Atkinson
draft-rja-ilnp-intro-02.txt                        Extreme Networks
Expires:  10 JUN 2009                              10 December 2008
Category: Experimental

                       ILNP Concept of Operations

Status of this Memo

   Distribution of this memo is unlimited.

   By submitting this Internet-Draft, each author represents that any
   applicable patent or other IPR claims of which he or she is aware
   have been or will be disclosed, and any of which he or she becomes
   aware will be disclosed, in accordance with Section 6 of BCP 79.

   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 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

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

   This document is a contribution to the IRTF Routing Research Group.
   It is NOT a contribution to the IETF or to any IETF Working Group
   or to any IETF Area.


   This documents the Concept of Operations for an experimental
   extension to IPv6 which is known as the Identifier Locator
   Network Protocol (ILNP).

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Table of Contents

   1. Introduction ...............................................2
   2. Transport Protocols.........................................4
   3. Multi-Homing................................................5
   4. Mobility....................................................6
   5. Localised Addressing........................................7
   6. IP Security Enhancements....................................8
   7. DNS Enhancements............................................9
   8. Backwards Compatibility....................................10
   9. Incremental Deployment.....................................11
  10. Security Considerations ...................................12
  11. IANA Considerations .......................................16
  12. References ................................................16

1. Introduction

   At present, the IRTF Routing Research Group is studying different
   approaches to evolving the Internet Architecture.  Several
   different  classes of evolution  are being  considered.  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 evoluationary approaches.

   There has been substantial research relating to naming in the
   Internet through the years.[IEN-1][IEN-19][IEN-23][IEN-31][RFC-814]
   [RFC-1498] More recently, and mindful of that important prior work,
   the author has been examining enhancements to certain naming aspects
   of the Internet Architecture.[MobiArch07][MobiWAC07]

   This architectural concept derives originally from a note by Dave
   Clark to the IETF mailing list suggesting that the IPv6 address
   be split into separate Identifier and Locator fields.  Afterwards,
   Mike O'Dell persued this concept in Internet-Drafts describing "GSE"
   or "8+8".[8+8][GSE] More recently, the IRTF Namespace Research Group
   (NSRG) studied this matter.  Unusually for an IRTF RG, the NSRG
   operated on the principle that unanimity was required for the NSRG
   to make a recommendation.  The author was a member of the IRTF NSRG.
   At least one other proposal, the Host Identity Protocol (HIP), also
   derives in part from the IRTF NSRG studies (and related antecedant
   work).  This current proposal differs from O'Dell's work in various

   The crux of this proposal is to split each 128-bit IPv6 address
   into two separate fields, with crisp semantics for each.  It is

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   worth remembering here that an IPv6 address names a specific
   interface on a node, since the new scheme will be different in
   that regard.

                            1        1                2               3
    0       4      8        2        6                4               1
   | Version| Traffic Class |           Flow Label                    |
   |          Payload Length         |   Next Header  |  Hop Limit    |
   |                          Source Address                          |
   +                                                                  +
   |                                                                  |
   +                                                                  +
   |                                                                  |
   +                                                                  +
   |                                                                  |
   |                        Destination  Address                      |
   +                                                                  +
   |                                                                  |
   +                                                                  +
   |                                                                  |
   +                                                                  +
   |                                                                  |

           Figure 1:  Existing ("Classic") IPv6 Header

   The high-order 64-bits of the IPv6 address become the Locator.
   The Locator indicates the subnetwork point of attachment for
   a node.  In essence, the Locator names a subnetwork.  Locators
   are also known as Routing Prefixes.

   The low-order 64-bits of the IPv6 address become the Identifier.
   The Identifier provides a fixed-length identity for a node,
   rather than an identity for a specific interface of a node.
   Identifiers are bound to nodes, not to interfaces, and are
   in the same modified EUI-64 syntax already specified for

   Identifiers are unique within the context of a given Locator; in many
   cases, Identifiers might happen to be globally unique, but that is
   not a functional requirement for this proposal.

                            1        1                2               3

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    0       4      8        2        6                4               1
   | Version| Traffic Class |           Flow Label                    |
   |          Payload Length         |   Next Header  |   Hop Limit   |
   |                          Source Locator                          |
   +                                                                  +
   |                                                                  |
   |                         Source Identifier                        |
   +                                                                  +
   |                                                                  |
   |                        Destination  Locator                      |
   +                                                                  +
   |                                                                  |
   |                        Destination Identifier                    |
   +                                                                  +
   |                                                                  |

              Figure 2: Enhanced IPv6 Header

   Most commonly, a node's set of Identifiers are derived from the
   IEEE 802 or IEEE 1394 MAC addresses associated with that node.
   This use of MAC addresses to generate Identifiers is convenient
   and is not required.  Other methods also might be used to generate
   Identifiers. For example, one might derive Identifiers using
   cryptographic-generation or using methods specified in the IPv6
   Privacy Extensions to State-Less Address Auto-Configuration
   (SLAAC). [RFC-3972, RFC-4941]

   This proposal enhances the Internet Architecture by adding crisp
   and clear semantics for the Identifier and for the Locator,
   removing the semantically-muddled concept of the IP address,
   and updating end system protocols slightly, without requiring
   router changes.

   With these naming enhancements, we have improved the architectural
   support not only for multi-homing, but also for mobility,
   localised addressing (e.g. NAT/NAPT), and IP Security.

2. Transport Protocols

   At present, commonly deployed transport protocols include a

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   pseudo-header checksum that includes certain network-layer
   fields, the IP addresses used for the session, in its
   calculation.  This inclusion of network-layer information
   within the transport-layer session state creates issues for
   multi-homing, mobility, IP Security, and localised
   addressing (e.g. using Network Address Translation).

   This unfortunate aspect of the TCP pseudo-header checksum
   has been understood to be an architectural problem at least
   since 1977, well before the transition from NCP to

   With this proposal, transport protocols include only the
   Identifier in their pseudo-header calculations, but do not
   include the Locator in their pseudo-header calculations.

   To minimise the changes required within transport protocol
   implementations, when this proposal is in use for an IP
   session, the Locator fields are zeroed before use by the
   transport protocols.

   Later in this document, methods for incremental deployment
   of this change and backwards compatibility with non-upgraded
   nodes are described.

3. Multi-Homing

   Conceptually, there are two kinds of multi-homing.  Site
   multi-homing is when all nodes at a site are multi-homed at
   the same time.  This is what most people mean when they talk
   about multi-homing.  However, there is also a separate
   concept of node multi-homing, where only a single node is

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

   At present, node multi-homing is not uncommon.  When TCP
   or UDP are in use for a session, node multi-homing cannot
   provide session reslience, because the transport

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   pseudo-header checksum binds the session to a single
   interface of the multi-homed node.  It must be noted that
   SCTP has a protocol-specific mechanism to support node
   multi-homing; SCTP can support session resilience both at
   present and also without change in the proposed approach.

   In the new scheme, when a node is multi-homed, it has more
   than one valid Locator value.  When one upstream connection
   fails, the node sends an ICMP Locator Update message to each
   existing correspondent node to remove the no-longer-valid
   Locator from the set of valid Locators. [ILNP-ICMP] Also,
   the node will use Secure Dynamic DNS Update to alter the set
   of currently valid L records associated with that node.
   [RFC-3007] This second step ensures that any new
   correspondents can reach the node.

   In the new scheme, site multi-homing works in a similar
   manner, with nodes having one Locator for each upstream
   connection to the Internet.  To avoid a DNS Update burst
   when a site or subnetwork moves location, a DNS record
   optimisation is possible.  This would change the number of
   DNS Updates required from Order(number of nodes at the
   site/subnetwork that moved) to Order(1).[ILNP-DNS]

   Additionally, since the transport-protocol session state
   no longer includes the Locators, a site could choose to
   perform Locator rewriting at its site border routers,
   possibly in combination with applying site traffic engineering
   policy on which upstream link to use for which packets.
   Since the site border router(s) are in the middle of any
   exterior packet flow, they also can send proxy Locator
   Update messages on behalf of nodes inside that site,
   and can even include the appropriate Nonce value in such
   proxy Locator Updates, if desired by that site's

4.  Mobility

   First, note well that mobiity and multi-homing actually present
   the same set of issues.  In each case, the set of Locators
   associated with a node or site changes.  The reason for the
   change might be different, but the effects on the network and
   on correspondents is identical.

   There are no standardised mechanisms to update most transport
   protocols with new IP addresses in use for the session.
   Exceptionally, the Stream Control Transport Protocol (SCTP)

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   recently added this capability.[RFC-5061]

   This creates various issues for mobility.  For example, there is
   no method at present to update the IP addresses associated with
   a transport layer session when one of the nodes in that session
   moves (i.e. changes one of its points of network attachment).

   So, the several approaches to IP mobility seek to hide the change
   in location (and corresponding change in IP addresses) via
   tunnelling, home agents, foreign agents, and so forth.[RFC-3775]
   All of this can add substantial complexity to IP mobility
   approaches, both in the initial deployment and also in ongoing

   By contrast, this ILNP proposal hides each node's location
   information from the transport layer protocols at all times,
   by removing location information from the transport session
   state (e.g. pseudo-header checksum calculations).

   In this proposal, mobility is supported using the same
   mechanisms as multihoming.  Both cases use Locator values to
   identify different IP subnetworks. To handle the move of a
   node, we add a new ICMP control message.  The ICMP Locator
   Update message is used by a node to inform its existing
   correspondents 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.  Further, the node uses Secure Dynamic DNS
   Update to correct the set of L records in the DNS for that
   node.  This enables any new correspondents to correctly
   initiate a new session with the node at its new location.
   This use of DNS for initial rendezvous with mobile node was
   independently proposed by others [PHG02] and then separately
   by the current author later on.

   Note that we can (and do) treat network mobility (as well as
   node mobility) as a special case of multihoming.  That is,
   when a network moves, it uses a new Locator value for all of
   its communications sessions.  So, the same mechanism, using
   a new or additional Locator value, also supports network

   So in ILNP, when a connectivity change affects the set of
   valid Locators, the affected node(s) actively update their
   correspondents with the updated information and also update
   their DNS entries.  This combination eliminates the need for
   network probing to discover how to reach an existing
   correspondent that has moved (or whose connectivity has developed

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   a fault).  Middleboxes do not need to participate for this
   to succeed.

5. Localised Addressing

   As the Locator value no longer forms part of the node session state
   (e.g. TCP pseudo-header), it is easier to implement localised
   addressing based on the use of local values of the Locator.  This
   would be either in place of, or to supplement, existing NAT-based
   schemes.[RFC-1631] [RFC-3022] For example, some form of IPv6 Unique
   Local Addressing (ULA) might be used for localised addressing along
   with some form of IPv6 network address translation at a site border

   In the simplest case, an ILNP capable NAT only would need to change
   the value of the Source Locator in an outbound packet, and the
   value of the Destination Locator for an inbound packet.  Identifier
   values would not need to change, so a true end-to-end session
   could be maintained.

   If a site using localised addressing chooses to deploy a
   split-horizon DNS server, then all internal nodes would advertise
   the global-scope Locator(s) of the site border routers outside
   the site and would advertise the local-scope Locator(s) specific
   to that internal node inside the site.  Such deployments of
   split-horizon DNS servers are not unusual in the IPv4 Internet

   If a site using localised addressing chooses not to deploy
   a split-horizon DNS server, then all internal nodes would advertise
   the global-scope Locator(s) of the site border routers.  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,
   IEEE Rapid Spanning Tree, 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.

   Please note that with this proposal, localised addressing
   (e.g. using Network Address Translation on the Locator bits)
   would work in harmony with multihoming, mobility, and IP

6.  IP Security Enhancements

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   A current issue is that the IP Security protocols, AH and ESP,
   have Security Associations that include the IP addresses of
   the secure session endpoints.  This was understood to be a
   problem when AH and ESP were originally defined, however the
   limited set of namespaces in the Internet Architecture did not
   provide any better choices at that time.

   Operationally, this binding causes problems for the use of
   the IPsec protocols through Network Address Translation
   devices, with mobile nodes (because the mobile node's IP
   address changes at each network-layer handoff), and with
   multi-homed nodes (because the session is bound to a
   particular interface of the multi-homed node, rather than
   being bound to the node itself).[RFC-3027][RFC-3715]

   To resolve the issue of IPsec interoperability through
   a NAT deployment, UDP encapsulation of IPsec is commonly
   used today.[RFC-3948]

   With this proposal, the IP Security protocols, AH and ESP,
   are enhanced to bind Security Associations only to
   Identifier values and never to Locator values (and also not
   to an entire 128-bit IPv6 address).

   Similarly, key management protocols used with IPsec would be
   enhanced to deprecate use of IP addresses as identifiers and
   to substitute the use of the new Identifier for that

   This small change enables IPsec to work in harmony with
   multihoming, mobility, and localised addressing.  Further,
   it would obviate the need for specialised IPsec NAT
   Traversal mechanisms, thus simplifying IPsec implementations
   while enhancing deployability and interoperability.

   This change does not reduce the security provided by the IP
   Security protocols.

7. DNS Enhancements

   As part of this proposal, additional DNS Resource Records have
   been proposed in a separate document. [ILNP-DNS] These new
   records store the Identifier and Locator values for nodes that
   have been upgraded to support the Identifier-Locator Split Mode.

   With this proposal, mobile or multi-homed nodes and sites are
   expected to use the existing widely implemented "Secure Dynamic

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   DNS Update" protocol to keep their Identifier and Locator records
   correct in its authoritative DNS server(s).  [RFC-3007]

   Reverse DNS lookups, to find a node's Fully Qualified Domain Name
   from the combination of a Locator and related Identifier value,
   can be performed as at present.

   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 will not be adversely affected by assigning
   very short time-to-live (TTL) values to the Locator records of
   typical nodes.  It also means that it is preferable to deploy the
   DNS server function on nodes that have longer TTL values, rather
   than on nodes that have shorter 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 or
   are cryptographically-generated, or they might have a moderate
   lifetime (e.g. hours) when they have been created by the
   IPv6 Privacy Extensions or some other method that regularly
   generates new Identifier values over time.

   Existing DNS specifications require that DNS clients and DNS
   resolvers obey 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.

   As a practical matter, it is not sensible to flush all Locator
   values associated with an existing session's remote node from the
   local node's I/L Session Cache.  Instead, Locator values should
   be marked as "aged" when their TTL has expired until the next
   Locator Update message is received or there is other indication
   that a given Locator is not working any longer.

   During a long transition period, a node that is I/L-enabled
   should have not only I and L records present in its
   authoritative DNS server, but also should have AAAA records
   for the benefit of non-upgraded nodes.  This capability might
   be implemented strictly inside a DNS server, whereby the DNS
   server synthesised a set of AAAA records to advertise from
   the I and L values that the node has kept updated in that
   DNS server.

   Existing DNS specifications require that a DNS resolver or DNS

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   client ignore unrecognised DNS record types.  So gratuitously
   appending I and L records as "additional data" in DNS responses
   to AAAA queries is not expected to create any operational issues.

8. Backwards Compatibility

   First, if one comapres Figure 1 and Figure 2, one can see
   that IPv6 with the Identifier/Locator Split enhancement is
   fully backwards compatible with existing IPv6.  This means
   that no router software or silicon changes are necessary to
   support the proposed enhancements.  A router would be
   unaware whether the packet being forwarded were classic IPv6
   or the proposed enhanced version of IPv6.  So no changes to
   IPv6 routers is required to deploy this proposal.

   Further, IPv6 Neighbour Discovery should work fine without
   any significant protocol changes.

   If a node that has been enhanced to support the Identifier/
   Locator Split mode initiates an IP session with another
   node, normally it will first perform a DNS lookup on the
   responding node's DNS name.  If the inititator node does not
   find any new I and L DNS resource records for the responder
   node, then the initiator uses the Classical IPv6 mode of
   operation for the new session with the responder, rather
   than trying to use the I/L Split mode for that session.

   If the responder node for a new IP session has not been
   enhanced to support the I/L Split mode and receives initial
   packet(s) containing the Nonce Destination Option, the
   responder will drop the packet and send an ICMP Parameter
   Problem error message back to the initiator.

   If the initiator node does not receive a response from the
   responder in a timely manner (e.g. within TCP timeout for a
   TCP session) and also does not receive an ICMP Unreachable
   error message for that packet, OR if the initiator receives
   an ICMP Parameter Problem error message for that packet,
   then the initiator knows that the responder is not able to
   support the I/L Split Operating mode.  In this case, the
   initiator node should try again to create the new IP session
   but this time OMITTING the Nonce Destination Option, and
   this time operating in Classic IPv6 mode, rather than I/L
   Split mode.

   The existing BSD Sockets API can continue to be used.  That
   API can be implemented in a manner that hides the underlying
   protocol changes from the applications.  So it is believed

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   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.

   (We note, however, that a more architecturally sensible
   approach to referrals would be to use Fully-Qualified Domain
   Names (FQDNs), as is commonly done today with web URLs.
   This is true even with the deployed IPv4 or IPv6 Internet.)

   It is suggested, however, that a new, optional, more
   abstract, API be created so that new applications do not
   have to delve needlessly into low-level details of the
   underlying network protocols.

9. Incremental Deployment

   If a node has been enhanced to support the Identifier/
   Locator Split operating mode, that node's fully-qualified
   domain name will normally have one or more I records and one
   or more L records associated with it in the DNS.

   When a host ("initiator") initiates a new IP session with a
   correspondent ("responder"), it normally will perform a DNS
   lookup to determine the address(es) of the responder.  A
   host that has been enhanced to support the Identifier/
   Locator Split operating mode normally will look for
   Identifier ("I") and Locator ("L") records in any received
   DNS replies.  DNS servers that support I and L records
   should include them (when they exist) as additional data in
   all DNS replies to queries for DNS AAAA records.[ILNP-DNS]

   If the initiator supports the I/L Split mode and from DNS
   information learns that the responder also supports the I/L
   Split mode, then the initiator will generate an unpredictable
   nonce value, store that value in a local Correspondent Cache,
   and will include the Nonce Destination Option in its initial
   packet(s) to the responder.[ILNP-Nonce]

   If the responder supports the I/L Split mode and receives
   initial packet(s) containing the Nonce Destination Option,
   the responder will thereby know that the initiator supports
   the I/L Split mode and the responder will also operate in
   I/L Split mode for this new IP session.

   If the responder supports the I/L Split mode and receives

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   initial packet(s) NOT containing the Nonce Destination Option,
   the responder will thereby know that the initiator does NOT
   support the I/L Split mode and the responder will operate
   in classic IPv6 mode for this new IP session.

   The previous section described how interoperability between
   enhanced nodes and non-enhanced nodes is retained even if a
   non-enhanced node erroneously has I and L DNS resource
   records in place (e.g. due to some accident).

10. Security Considerations

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

10.1 Authentication of Locator Updates

   A separate document [ILNP-Nonce] proposed a new IPv6
   Destination Option that can be used to carry a session nonce
   end-to-end between communicating nodes.  That nonce provides
   protection against off-path attacks on an Identifier/Locator
   session.  The Nonce Destination Option is used ONLY for IP
   sessions in the Identifier/Locator Split mode.

   Ordinary IPv6 is vulnerable to on-path attacks unless
   the IP Authentication Header or IP Encapsulating Security
   Payload is in use.  So the Nonce Destination Option
   only seeks to provide protection against off-path attacks
   on an IP session -- equivalent to ordinary IPv6 when
   not using IP Security.

   When the Identifier/Locator split mode is in use for an
   existing IP session, the Nonce Destination Option must be
   included in any ICMP control messages (e.g. ICMP Unreachable,
   ICMP Locator Update) sent with regard to that IP session.

   It is common to have non-symmetric paths between
   two nodes on the Internet.  To reduce the number
   of on-path nodes that know the Nonce value for
   a given session when the I/L split mode is in use,
   separate nonce values are used in each direction.
   For example, for a session between two nodes A and B,
   one nonce value is used from A to B and a different
   nonce value is used from B to A.

   When in the I/L Split operating mode for an existing IP

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   session, ICMP control messages received without a Nonce
   Destination Option must be discarded as forgeries.  This
   security event should be logged.

   When in the I/L Split operating mode for an existing IP
   session, ICMP control messages received without a correct
   nonce value inside the Nonce Destination Option must be
   discarded as forgeries.  This security event should be logged.

   When in the I/L Split operating mode for an existing IP
   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

   For ID/Locator Split mode sessions operating in higher risk
   environments, the use of the cryptographic authentication
   provided by IP Authentication Header is recommended
   *in addition* to concurrent use of the Nonce Destination

   It is important to note that at present an IPv6 session
   is entirely vulnerable to on-path attacks unless IPsec
   is in use for that particular IPv6 session, so the security
   properties of the new proposal are never worse than
   for existing IPv6.

10.2 Forged Identifier Attacks

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

   One mitigation for these attacks has been to deploy Source IP
   Address Filtering.[BCP-38] Jun Bi at U.  Tsinghua cites Arbor
   Networks as reporting that this mechanism has less than 50%
   deployment and cites an MIT analysis indicating that at least 25%
   of the deployed Internet permits forged source IP addresses.

   Other parts of this document discuss the probability of an
   accidental duplicate Identifier being used on the Internet.
   However, this sub-section instead focuses on methods for

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   mitigating attacks based on packets containing deliberately
   forged Source Identifier values.

   First, the recommendations of [BCP-38] remain.  Packets that
   have a forged Locator value can be easily filtered using
   existing widely available mechanisms.

   Second, the receiving node does not blindly accept any packet
   with the proper Source Identifier and proper Destination
   Identifier as an authentic packet.  Instead, each node operating
   the I/L-split mode maintains a session cache for each of its
   correspondents.  This 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).
   The cache also contains the currently valid set of Locators
   and set of Identifiers for each correspondent node.  If a
   received packet contains valid Identifier values and a valid
   Destination Locator, but contains a Source Locator value that
   is not present in the session cache, the packet is dropped
   without further processing as an invalid packet, unless the
   packet also contains a Nonce Destination Option with the
   correct value used for packets from the node with that
   Source Identifier to this node.  This prevents an off-path
   attacker from stealing an existing session.

   Third, any node can distinguish different nodes using the same
   Identifier value by other properties of their sessions.  IPv6
   Neighbor Discovery prevents more than one node from using the
   same source (Locator + Identifier) pair at the same time.  So
   cases of different nodes using the same Identifier value will
   involve nodes that have different sets of valid Locator values.
   A node can thus demux based on the combination of Source Locator
   and Source Identifier if necessary.  If IP Security is in use,
   the combination of the Source Identifier and the SPI value would
   be sufficient to demux two different sessions.

   Finally, deployments in high threat environments also should use
   the IP Authentication Header to authenticate control traffic and
   data traffic.  Because in the I/L-split mode, IP Security binds
   only to the Identifier values, and never to the Locator values,
   this enables a mobile or multi-homed node to use IPsec even when
   its Locator value(s) have just changed.

10.3 IP Security Enhancements

   The IP Security standards are enhanced here by binding IPsec
   Security Associations to the Identifiers of the session
   endpoints, rather than binding IPsec Security Associations

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   to the IP Addresses as at present.  This change enhances the
   deployability and interoperability of the IP Security
   standards, but does not decrease the security provided by
   those protocols.

10.4 DNS Security

   The DNS enhancements proposed here are entirely compatible
   with, and can be protected using, the existing IETF
   standards for DNS Security.[RFC-4033] The Secure DNS Dynamic
   Update mechanism used here is also used unchanged.[RFC-3007]
   So there is no change to the security properties of the
   Domain Name System.

10.5 Firewall Considerations

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

   By always including the nonce, even when IP Security is also in
   use, the firewall can filter out all off-path attacks.  In this
   case, a forged packet from an on-path attacker will still be
   detected when the IPsec input processing occurs in the receiving
   node; this will cause that forged packet to be dropped rather
   than acted upon.

10.6 Neighbor Discovery Authentication

   Nothing in this proposal prevents sites from using
   the Secure Neighbor Discovery (SEND) proposal for
   authenticating IPv6 Neighbor Discovery. [RFC-3971]

11. IANA Considerations

   This document has no IANA considerations.

12.  References

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

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12.1.  Normative References

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

   [RFC-2460]   S. Deering & R. Hinden, "Internet Protocol
                Version 6 Specification", RFC-2460,
                December 1998.

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

   [RFC-4033]   R. Arends, et alia, "DNS Security Introduction
                and Requirements", RFC-4033, March 2005.

   [RFC-4219]   R. Hinden & S. Deering, "IP Version 6
                Addressing Architecture", RFC-4219, February

12.2.  Informative References

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

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

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

   [IEEE-EUI]   IEEE Standards Association, "Guidelines for
                64-bit Global Identifier (EUI-64)", IEEE,

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

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

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

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

   [ILNP-Nonce] R. Atkinson, "Nonce Destination Option",
                draft-rja-ilnp-nonce-01.txt, December 2008.

   [ILNP-DNS]   R. Atkinson, "Additional DNS Resource Records",
                draft-rja-ilnp-dns-01.txt, December 2008.

   [ILNP-ICMP]  R. Atkinson, "ICMP Locator Update message"
                draft-rja-ilnp-icmp-00.txt, December 2008.

   [MobiArch07] R. Atkinson, S. Bhatti, & S. Hailes,
                "Mobility as an Integrated Service Through
                the Use of Naming", Proceedings of
                ACM MobiArch 2007, August 2007,
                Kyoto, Japan.

   [MobiWAC07]  R. Atkinson, S. Bhatti, & S. Hailes,
                "A Proposal for Unifying Mobility with
                Multi-Homing, NAT, & Security",
                Proceedings of ACM MobiWAC 2007, Chania,
                Crete. ACM, October 2007.

   [MILCOM08]   R. Atkinson, S. Bhatti, & S. Hailes,
                "Harmonised Resilience, Security, and Mobility
                Capability for IP", Proceedings of IEEE
                Military Communications Conference,
                San Diego, CA, USA, November 2008.

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

   [SBK2002]    Alex C. Snoeren, Hari Balakrishnan, & M. Frans
                Kaashoek, "Reconsidering Internet Mobility",
                Proceedings of 8th Workshop on Hot Topics in
                Operating Systems, 2002.

   [RFC-814]    D.D. Clark, "Names, Addresses, Ports, and
                Routes", RFC-814, July 1982.

   [RFC-1498]   J.H. Saltzer, "On the Naming and Binding of

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                Network Destinations", RFC-1498, August 1993.

   [RFC-1631]   K. Egevang & P. Francis, "The IP Network
                Address Translator (NAT)", RFC-1631, May 1994.

   [RFC-3022]   P. Srisuresh & K. Egevang, "Traditional IP
                Network Address Translator", RFC-3022,
                January 2001.

   [RFC-3027]   M. Holdrege and P Srisuresh, "Protocol
                Complications of the IP Network Address
                Translator", RFC-3027, January 2001.

   [RFC-3715]   B. Aboba and W. Dixon, "IPsec-Network Address
                Translation (NAT) Compatibility Requirements",
                RFC-3715, March 2004.

   [RFC-3775]   D. Johnson, C. Perkins, and J. Arkko, "Mobility
                Support in IPv6", RFC-3775, June 2004.

   [RFC-3948]   A. Huttunen, et alia, "UDP Encapsulation of
                IPsec ESP Packets", RFC-3948, January 2005.

   [RFC-3972]   T. Aura, "Cryptographically Generated Addresses
                (CGAs)", RFC-3972, March 2005.

   [RFC-4193]   R. Hinden & B. Haberman, "Unique Local IPv6
                Unicast Addresses, RFC-4193, October 2005.

   [RFC-4941]   T. Narten, R. Draves, & S. Krishnan, "Privacy
                Extensions for Stateless Address Autoconfiguration
                in IPv6", RFC-4941, September 2007.

   [RFC-5061]   R. Stewart, Q. Xie, M. Tuexen, S. Maruyama, &
                M. Kozuka, "Stream Control Transmission Protocol
                (SCTP) Dynamic Address Reconfiguration", RFC-5061,
                September 2007.

   (Additional references to be added later.)

Author's Address

   R. Atkinson
   Extreme Networks
   3585 Monroe Street
   Santa Clara, CA
   95051  USA

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   Telephone: +1 (408)579-2800
   Email:     rja@extremenetworks.com

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Expires: 10 June 2009

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