Network Working Group                                    G. Van de Velde
Internet-Draft                                                   T. Hain
Expires: December 3, 2005                                       R. Droms
                                                           Cisco Systems
                                                            B. Carpenter
                                                         IBM Corporation
                                                                E. Klein
                                                     Tel Aviv University
                                                               june 2005

                  IPv6 Network Architecture Protection

Status of this Memo

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   This Internet-Draft will expire on December 3, 2005.

Copyright Notice

   Copyright (C) The Internet Society (2005).


   Although there are many perceived benefits to Network Address
   Translation (NAT), its primary benefit of "amplifying" available
   address space is not needed in IPv6.  In addition to NAT's many

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   serious disadvantages, there is a perception that other benefits
   exist, such as a variety of management and security attributes that
   could be useful for an Internet Protocol site.  IPv6 does not support
   NAT by design and this document shows how Network Architecture
   Protection (NAP) using IPv6 can provide the same or more benefits
   without the need for NAT.

Table of Contents

   1.   Introduction . . . . . . . . . . . . . . . . . . . . . . . .   4
   2.   Perceived benefits of NAT and its impact on IPv4 . . . . . .   6
     2.1  Simple gateway between Internet and internal network . . .   6
     2.2  Simple security due to stateful filter implementation  . .   6
     2.3  User/Application tracking  . . . . . . . . . . . . . . . .   7
     2.4  Privacy and topology hiding  . . . . . . . . . . . . . . .   8
     2.5  Independent control of addressing in a private network . .   9
     2.6  Global address pool conservation . . . . . . . . . . . . .   9
     2.7  Multihoming and renumbering with NAT . . . . . . . . . . .   9
   3.   Description of the IPv6 tools  . . . . . . . . . . . . . . .  10
     3.1  Privacy addresses (RFC 3041) . . . . . . . . . . . . . . .  10
     3.2  Unique Local Addresses . . . . . . . . . . . . . . . . . .  11
     3.3  DHCPv6 prefix delegation . . . . . . . . . . . . . . . . .  11
     3.4  Untraceable IPv6 addresses . . . . . . . . . . . . . . . .  12
   4.   Using IPv6 technology to provide the market perceived
        benefits of NAT  . . . . . . . . . . . . . . . . . . . . . .  12
     4.1  Simple gateway between Internet and internal network . . .  12
     4.2  IPv6 and Simple security . . . . . . . . . . . . . . . . .  13
     4.3  User/Application tracking  . . . . . . . . . . . . . . . .  14
     4.4  Privacy and topology hiding using IPv6 . . . . . . . . . .  15
     4.5  Independent control of addressing in a private network . .  15
     4.6  Global address pool conservation . . . . . . . . . . . . .  16
     4.7  Multihoming and renumbering  . . . . . . . . . . . . . . .  16
   5.   Case Studies . . . . . . . . . . . . . . . . . . . . . . . .  17
     5.1  Medium/large private networks  . . . . . . . . . . . . . .  17
     5.2  Small private networks . . . . . . . . . . . . . . . . . .  19
     5.3  Single user connection . . . . . . . . . . . . . . . . . .  20
     5.4  ISP/Carrier customer networks  . . . . . . . . . . . . . .  21
   6.   IPv6 gap analysis  . . . . . . . . . . . . . . . . . . . . .  22
     6.1  Completion of work on ULAs . . . . . . . . . . . . . . . .  22
     6.2  Subnet topology masking  . . . . . . . . . . . . . . . . .  22
     6.3  Minimal traceability of privacy addresses  . . . . . . . .  23
     6.4  Renumbering procedure  . . . . . . . . . . . . . . . . . .  23
     6.5  Site multihoming . . . . . . . . . . . . . . . . . . . . .  23
     6.6  Untraceable addresses  . . . . . . . . . . . . . . . . . .  23
   7.   IANA Considerations  . . . . . . . . . . . . . . . . . . . .  23
   8.   Security Considerations  . . . . . . . . . . . . . . . . . .  23
   9.   Conclusion . . . . . . . . . . . . . . . . . . . . . . . . .  24
   10.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . .  24

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   11.  References . . . . . . . . . . . . . . . . . . . . . . . . .  24
     11.1   Normative References . . . . . . . . . . . . . . . . . .  24
     11.2   Informative References . . . . . . . . . . . . . . . . .  25
        Authors' Addresses . . . . . . . . . . . . . . . . . . . . .  26
   A.   Additional benefits due to Native IPv6 and universal
        unique addressing  . . . . . . . . . . . . . . . . . . . . .  27
     A.1  Universal any-to-any connectivity  . . . . . . . . . . . .  27
     A.2  Auto-configuration . . . . . . . . . . . . . . . . . . . .  27
     A.3  Native Multicast services  . . . . . . . . . . . . . . . .  28
     A.4  Increased security protection  . . . . . . . . . . . . . .  28
     A.5  Mobility . . . . . . . . . . . . . . . . . . . . . . . . .  29
     A.6  Merging networks . . . . . . . . . . . . . . . . . . . . .  29
     A.7  Community of interest  . . . . . . . . . . . . . . . . . .  29
   B.   Revision history . . . . . . . . . . . . . . . . . . . . . .  30
     B.1  Changes from *-vandevelde-v6ops-nap-00 to
          *-vandevelde-v6ops-nap-01  . . . . . . . . . . . . . . . .  30
     B.2  Changes from *-vandevelde-v6ops-nap-01 to
          *-ietf-v6ops-nap-00  . . . . . . . . . . . . . . . . . . .  30
     B.3  Changes from *-ietf-v6ops-nap-00 to *-ietf-v6ops-nap-01  .  30
        Intellectual Property and Copyright Statements . . . . . . .  31

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1.  Introduction

   Although there are many perceived benefits to Network Address
   Translation (NAT), its primary benefit of "amplifying" available
   address space is not needed in IPv6.  The serious disadvantages of
   ambiguous "private" address space and of Network Address Translation
   (NAT) [1][5] have been well documented [4][6].  However, given its
   wide market acceptance NAT undoubtedly has some perceived benefits.
   Indeed, in an Internet model based on universal any-to-any
   connectivity, product marketing departments have driven a perception
   that some connectivity and security concerns can only be solved by
   using a NAT device or by using logically separated LAN address
   spaces.  This document describes the market-perceived reasons to
   utilize a NAT device in an IPv4 environment and shows how these needs
   can be met and even exceeded with IPv6.  The use of the facilities
   from IPv6 described in this document avoids the negative impacts of
   translation and may be described as Network Architecture Protection

   As far as security and privacy is concerned, this document considers
   how to mitigate a number of threats.  Some are obviously external,
   such as having a hacker trying to penetrate your network, or having a
   worm infected machine outside your network trying to attack it.  Some
   are local such as a disgruntled employee disrupting business
   operations, or the unintentional negligence of a user downloading
   some malware which then proceeds to attack any device on the LAN.
   Some may be embedded such as having some firmware in a domestic
   appliance "call home" to its manufacturer without the user's consent.

   This document describes several techniques that may be combined on an
   IPv6 site to protect the integrity of its network architecture.
   These techniques, known collectively as NAP, retain the concept of a
   well defined boundary between "inside" and "outside" the private
   network, and allow firewalling, topology hiding, and privacy and will
   achieve these goals without address translation.

   IPv6 Network Architecture Protection can be summarized in the
   following table.  It presents the marketed functions of NAT with a
   cross-reference of how those are delivered in both the IPv4 and IPv6

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        Function               IPv4                     IPv6
   | Simple Gateway   |  DHCP - single        |  DHCP-PD - arbitrary  |
   | as default router|  address upstream     |  length customer      |
   | and address pool |  DHCP - limited       |  prefix upstream      |
   | manager          |  number of individual |  SLAAC via RA         |
   |                  |  devices downstream   |  downstream           |
   |                  |  see section 2.1      |  see section 4.1      |
   |  Simple Security |  Filtering side       |  Explicit Context     |
   |                  |  effect due to lack   |  Based Access Control |
   |                  |  of translation state |  (Reflexive ACL)      |
   |                  |  see section 2.2      |  see section 4.2      |
   |  Local usage     |  NAT state table      |  Address uniqueness   |
   |  tracking        |                       |                       |
   |                  |  see section 2.3      |  see section 4.3      |
   |  End system      |  NAT transforms       |  Temporary use        |
   |  privacy         |  device ID bits in    |  privacy addresses    |
   |                  |  the address          |                       |
   |                  |  see section 2.4      |  see section 4.4      |
   |  Topology hiding |  NAT transforms       |  Untraceable addresses|
   |                  |  subnet bits in the   |  using IGP host routes|
   |                  |  address              |  /or MIPv6 tunnels for|
   |                  |                       |  stationary systems   |
   |                  |  see section 2.4      |  see section 4.4      |
   |  Addressing      |  RFC 1918             |  RFC 3177 & ULA       |
   |  Autonomy        |                       |                       |
   |                  |  see section 2.5      |  see section 4.5      |
   |  Global Address  |  RFC 1918             |  340,282,366,920,938, |
   |  Pool            |                       |  463,463,374,607,431, |
   |  Conservation    |                       |  768,211,456          |
   |                  |                       |  (3.4*10^38) addresses|
   |                  |  see section 2.6      |  see section 4.6      |
   |  Renumbering and |  Address translation  |  Preferred lifetime   |
   |  Multi-homing    |  at border            |  per prefix & Multiple|
   |                  |                       |  addresses per        |
   |                  |                       |  interface            |
   |                  |  see section 2.7      |  see section 4.7      |

   This document first identifies the perceived benefits of NAT in more
   detail, and then shows how IPv6 NAP can provide each of them.  It

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   concludes with a IPv6 NAP case study and a gap analysis of work that
   remains to be done for a complete NAP solution.

2.  Perceived benefits of NAT and its impact on IPv4

   This section provides visibility into the generally perceived
   benefits of the use of IPv4 NAT.  The goal of this description is not
   to analyze these benefits or discuss the accuracy of the perception
   (detailed discussions in [4]) , but to describe the deployment
   requirements and set a context for the later descriptions of the IPv6
   approaches for dealing with those requirements.

2.1  Simple gateway between Internet and internal network

   A NAT device can connect a private network with any kind of address
   (ambiguous [RFC 1918] or global registered address) towards the
   Internet.  The address space of the private network can be built from
   globally unique addresses, from ambiguous address space or from both
   simultaneously.  Without specific configuration from public to
   private, the NAT device enables access between the client side of an
   application in the private network with the server side in the public

   Wide-scale deployments have shown that using NAT to attach a private
   IPv4 network to the Internet is simple and practical for the non-
   technical end user.  Frequently a simple user interface is sufficient
   for configuring both device and application access rights.

   Additionally, thanks to successful marketing campaigns it is
   perceived by end users that their equipment is protected from the bad
   elements and attackers on the public IPv4 Internet.

2.2  Simple security due to stateful filter implementation

   A firewall doesn't fully secure a network, because many attacks come
   from inside or are at a layer higher than the firewall can protect
   against.  In the final analysis, every system has to be responsible
   for its own security, and every process running on a system has to be
   robust in the face of challenges like stack overflows etc.  What a
   firewall does is prevent a network administration from having to pay
   for bandwidth to carry unauthorized traffic, and in so doing reduce
   the probability of certain kinds of attacks across the protected

   A distributed security mechanism to protect the end-systems may help
   in the above situation; however, to deploy such a system is quite
   complex and may depend upon behaviour per operating system and
   release version.  As a result it will probably not be available in

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   the next couple of years for end-user organizations.  End-system-only
   security mechanisms don't protect the network infrastructure from
   being misused for transit, or against DDOS attacks against individual
   systems inside, and this is the area where a NAT device is perceived
   to provide some relief.

   It is frequently believed that through its session-oriented
   operation, NAT puts in an extra barrier to keep the private network
   protected from evil outside influences.  Since a NAT device typically
   keeps state only for individual sessions, attackers, worms, etc.
   cannot exploit this state to attack a host in general and on any
   port.  This benefit may be partially real, however, experienced
   hackers are well aware of NAT devices and are very familiar with
   private address space, and have devised methods of attack (such as
   trojan horses) that readily penetrate NAT boundaries.  For these
   reasons the sense of security provided by NAT are actually false.

   Address translation does not provide security in itself; for example,
   consider a configuration with static NAT translation and all inbound
   ports translating to a single machine.  In such a scenario the
   security risk for that machine is identical to the case with no NAT
   device in the communication path.  As result there is no specific
   security value in the address translation function.  The perceived
   security comes from the lack of pre-established or permanent mapping
   state.  Dynamically establishing state in response to internal
   requests reduces the threat of unexpected external connections to
   internal devices.

   In some cases, NAT operators (including domestic users) may be
   obliged to configure quite complex port mapping rules to allow
   external access to local applications such as a multi-player game or
   web servers.  In this case the NAT actually adds management
   complexity compared to a simple router.  In situations where 2 or
   more devices need to host the same application this complexity shifts
   from difficult to impossible.

2.3  User/Application tracking

   Although NATs create temporary state for active sessions, in general
   they provide limited capabilities for the administrator of the NAT to
   gather information about who in the private network is requesting
   access to which Internet location.  This could in theory be done by
   logging the network address translation details of the private and
   the public addresses of the NAT devices state database.

   The checking of this database is not always a simple task, especially
   if Port Address Translation is used.  It also has an unstated
   assumption that the administrative instance has a mapping between an

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   IPv4-address and a network element or user at all times, or the
   administrator has a time-correlated list of the address/port

2.4  Privacy and topology hiding

   The ability of NAT to provide internet access by the use of a single
   (or few) global IPv4 routable addresses to a large community of users
   offers a simple mechanism to hide the internal topology of a network.
   In this scenario the large community will be reflected in the
   internet by a single (or few) IPv4 address(es).

   The use of NAT then results in a user behind a NAT gateway actually
   appearing on the Internet as a user inside the NAT box itself; i.e.,
   the IPv4 address that appears on the Internet is only sufficient to
   identify the NAT.  When concealed behind a NAT it is impossible to
   tell from the outside which member of a family, which customer of an
   Internet cafe, or which employee of a company generated or received a
   particular packet.  Thus, although NATs do nothing to provide
   application level privacy, they do prevent the external tracking and
   profiling of individual host computers by means of their IP
   addresses.  At the same time a NAT creates a smaller pool of
   addresses for a much more focused point of attack.

   There is a similarity with privacy based on application level
   proxies.  When using an application level gateway for browsing the
   web for example, the 'privacy' of a web user can be provided by
   masking the true identity of the original web user towards the
   outside world (although the details of what is - or is not - logged
   at the NAT/proxy will be different).

   Some enterprises prefer to hide as much as possible of their internal
   network topology from outsiders.  Mostly this is achieved by blocking
   "traceroute" etc., but NAT of course entirely hides the internal
   subnet topology, which some network managers believe is a useful
   precaution to mitigate scanning attacks.  Scanning for IPv6 can be
   much harder in comparison with IPv4 as described in [17]

   Once a list of available devices and IP addresses has been mapped, a
   port-scan on these IP addresses can be performed.  Scanning works by
   tracking which ports do not receive unreachable errors from either
   the firewall or host.  With the list of open ports an attacker can
   optimize the time needed for a successful attack by correlating it
   with known vulnerabilities to reduce the number of attempts.  For
   example, FTP usually runs on port 21, and HTTP usually runs on port
   80.  These open ports could be used for initiating attacks on an end

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2.5  Independent control of addressing in a private network

   Many private IPv4 networks take benefit from using the address space
   defined in RFC 1918 to enlarge the available addressing space for
   their private network, and at the same time reduce their need for
   globally routable addresses.  This type of local control of address
   resources allows a clean and hierarchical addressing structure in the

   Another benefit is due to the usage of independent addresses on
   majority of the network infrastructure there is an increased ability
   to change provider with less operational difficulties.

2.6  Global address pool conservation

   Due to the ongoing depletion of the IPv4 address range, the remaining
   pool of unallocated IPv4 addresses is below 30%.  While mathematical
   models based on historical IPv4 prefix consumption periodically
   attempt to predict the future exhaustion date of the IPv4 address
   pool, a direct result of this continuous resource consumption is that
   the administrative overhead for acquiring globally unique IPv4
   addresses will continue increasing in direct response to tightening
   allocation policies.  In response to the increasing administrative
   overhead many Internet Service Providers (ISPs) have already resorted
   to the ambiguous addresses defined in RFC 1918 behind a NAT for the
   various services they provide as well as connections for their end
   customers.  In turn this has restricted the number of and types of
   applications that can be deployed by these ISPs and their customers.
   Forced into this limiting situation such customers can rightly claim
   that despite the optimistic predictions of mathematical models the
   global pool of IPv4 addresses is effectively already exhausted.

2.7  Multihoming and renumbering with NAT

   The elements of multihoming and renumbering are quite different.
   However, multihoming is often a transitional state for renumbering,
   and NAT interacts with both in the same way.

   For enterprise networks, it is highly desirable to be connected to
   more than one Internet Service Provider (ISP) and to be able to
   change ISPs at will.  This means that a site must be able to operate
   under more than one CIDR prefix [13] and/or readily change its CIDR
   prefix.  Unfortunately, IPv4 was not designed to facilitate either of
   these maneuvers.  However, if a site is connected to its ISPs via NAT
   boxes, only those boxes need to deal with multihoming and renumbering

   Similarly, if two enterprise IPv4 networks need to be merged, it may

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   well be that installing a NAT box between them will avoid the need to
   renumber one or both.  For any enterprise, this can be a short term
   financial saving, and allow more time to renumber the network
   components.  The long term solution is a single network without usage
   of NAT to avoid the ongoing operational complexity of overlapping

   This solution may be sufficient for some networks; however when the
   merging networks were already using address translation it will
   create huge problems due to admistrative difficulties of the merged
   address space.

3.  Description of the IPv6 tools

   This section describes several features that can be used to provide
   the protection features associated with IPv4 NAT.

3.1  Privacy addresses (RFC 3041)

   There are situations where it is desirable to prevent device
   profiling, such as by contacted web sites, so IPv6 privacy addresses
   were defined to provide that capability.  IPv6 addresses consist of a
   routing prefix, subnet-id part (SID) and an interface identifier part
   (IID).  For interfaces that contain embedded IEEE Link Identifiers
   the interface identifier is typically derived from it, though this
   practice facilitates tracking and profiling of a device as it moves
   around the Internet.  RFC 3041 describes an extension to IPv6
   stateless address autoconfiguration for interfaces [7].  Use of the
   privacy address extension causes nodes to generate global-scope
   addresses from interface identifiers that change over time, even in
   cases where the interface contains an embedded IEEE link identifier.
   Changing the interface identifier (thus the global-scope addresses
   generated from it) over time makes it more difficult for
   eavesdroppers and other information collectors to identify when
   addresses used in different transactions actually correspond to the
   same node.  A relatively short valid lifetime for the privacy address
   also has the side effect of reducing the attack profile of a device,
   as it is not directly attackable once it stops answering at the
   temporary use address.

   While the primary implementation and source of randomized RFC 3041
   addresses is expected to be from end systems running stateless
   autoconfiguration, there is nothing that prevents a DHCP server from
   running the RFC 3041 algorithm for any new IEEE identifier it hears,
   then remembering that for future queries.  This would allow using
   them in DNS for registered services since the assumption of a server
   based deployment would be a persistent value that minimizes DNS
   churn.  A DHCP based deployment would also allow for local policy to

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   periodically change the entire collection of end device addresses
   while maintaining some degree of central knowledge and control over
   which addresses should be in use at any point in time.

   Randomizing the IID, as defined in RFC 3041, only precludes tracking
   of the lower 64 bits of the IPv6 address.  Masking of the subnet ID
   will require additional approaches as discussed below in 3.4.
   Additional considerations are discussed in [16].

3.2  Unique Local Addresses

   Local network and application services stability during periods of
   intermittent connectivity between one or more providers requires
   address management autonomy.  Such autonomy in a single routing
   prefix environment would lead to massive expansion of the global
   routing tables, so IPv6 provides for simultaneous use of multiple
   prefixes.  The Unique Local Address prefix (ULA) [12] has been set
   aside for use in local communications.  The ULA address prefix for
   any network is routable over a locally defined collection of routers.
   These prefixes are NOT to be routed on the public global Internet as
   that would have a serious negative impact on global routing.

   ULAs have the following characteristics:
   o  Globally unique prefix
      *  Allows networks to be combined or privately interconnected
         without creating any address conflicts or requiring renumbering
         of interfaces using these prefixes
      *  If accidentally leaked outside of a network via routing or DNS,
         there is no conflict with any other addresses
   o  ISP independent and can be used for communications inside of a
      network without having any permanent or intermittent Internet
   o  Well known prefix to allow for easy filtering at network
   o  In practice, applications may treat these addresses like global
      scoped addresses

3.3  DHCPv6 prefix delegation

   The Prefix Delegation (DHCP-PD) options [10] provide a mechanism for
   automated delegation of IPv6 prefixes using the Dynamic Host
   Configuration Protocol (DHCP) [8].  This mechanism (DHCP-PD) is
   intended for delegating a long-lived prefix from a delegating router
   to a requesting router, across an administrative boundary, where the
   delegating router does not require knowledge about the topology of
   the links in the network to which the prefixes will be assigned.

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3.4  Untraceable IPv6 addresses

   These should be globally routable IPv6 addresses which can be
   randomly and independently assigned to IPv6 devices.

   The random assignment has as purpose to confuse the outside world on
   the structure of the local network.  However for the local network
   there is a correlation between the location of the device and the
   untraceable IPv6 address.  This correlation could be done by
   generating IPv6 host route entries or by utilizing an aggregation
   device like a Mobile IPv6 Home Agent.

   The main goal of untraceable IPv6 addresses is to create an
   apparently unpredictable network infrastructure as seen from external
   networks to protect the local infrastructure from malicious outside
   influences or from mapping any correlation between the network
   activities of multiple devices from external networks.  When using
   untraceable IPv6 addresses, it could be that two apparently
   sequential addresses are reachable on very different parts of the
   local network instead of belonging to the same subnet next to each

4.  Using IPv6 technology to provide the market perceived benefits of

   The facilities in IPv6 can be used to provide the protection
   perceived to be associated with IPv4 NAT.  This section gives some
   examples of how IPv6 can be used securely.

4.1  Simple gateway between Internet and internal network

   As a simple gateway, the device has the role of managing both packet
   routing and local address management.  A basic IPv6 router could have
   a default configuration to advertize inside the site a locally
   generated random ULA prefix, independently from the state of any
   external connectivity.  This would allow local nodes to communicate
   amongst themselves prior to establishing a global connection.  If the
   network happened to concatenate with another local network, this is
   highly unlikely to result in address collisions.  With external
   connectivity the simple gateway could also use DHCP-PD to acquire a
   routing prefix from the service provider for use when connecting to
   the global Internet.  End node connections involving other nodes on
   the global Internet will always use the global IPv6 addresses [9]
   derived from this prefix delegation.  In the very simple case there
   is no explicit routing protocol and a single default route is used
   out to the global Internet.  A slightly more complex case might
   involve local routing protocols, but with the entire local network
   sharing a common global prefix there would still not be a need for an

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   external routing protocol as a default route would continue to be
   consistent with the connectivity.

4.2  IPv6 and Simple security

   The vulnerability of an IPv6 host is similar as for an IPv4 host
   directly connected towards the Internet, and firewall and IDS systems
   are recommended.  A proxy may be used for certain applications, but
   has the caveat that the end to end transparancy is broken.  However,
   with IPv6, the following protections are available without the use of
   NAT while maintaining end-to-end reachability:
   1.  Short lifetimes on privacy extension suffixes reduce the attack
       profile since the node will not respond to the address once the
       address is no longer valid.
   2.  IPsec is a mandatory service for IPv6 implementations.  IPsec
       functions to prevent session hijacking, prevent content
       tampering, and optionally masks the packet contents.  While IPsec
       might be available in IPv4 implementations, deployment in NAT
       environments either breaks the protocol or requires complex
       helper services with limited functionality or efficiency.
   3.  The size of the typical subnet ::/64 will make a network ping
       sweep and resulting port-scan virtually impossible due to the
       amount of possible combinations available.  This goes from the
       assumption that the attacker has no access to a local connection.
       If an attacker has local access then he could use ND [3] and
       ping6 to ff02::1 to detect local neighbors.  (Of course, a
       locally connected attacker has many scanning options with IPv4 as
       well.)  It is recommended for site administrators to take [17]
       into consideration to achieve the expected goal.

   IPv4 NAT was not developed as a security mechanism.  Despite
   marketing messages to the contrary it is not a security mechanism,
   and hence it will pose some security holes while many people assume
   their network is secure due to the usage of NAT.  This is directly
   the opposite of what IPv6 security best-practices are trying to

   An example of a potential set of firewall rules could be:

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           Source_A:       IPv6 Home broadband user
                           located on the internal network
           Destination_B:  IPv6 HTTP server
                           located on the external network

           On the edge broadband router a security rule could be:

           Internal network -> external network:

               Allow all traffic
               Create reflective session state (true) for the session

           External network -> internal network

               If the session had reflective 'true'-state,
                 then allow the inbound traffic
               If the session had reflective 'false' state,
                 then drop the traffic

   This simple rule would create similar protection and security holes
   the typical IPv4 NAT device will offer and may for example be enabled
   by a simple user-interface and should provide the facility with a
   simple mechanism to create holes in the rules to serve certain
   applications on edge-routers, with that difference that the security
   caveats will be documented, and may hence be removed with the next
   revision of the rule.  The goal is that at every iteration, the IPv6
   internet will become more secure for the oblivious users.

   Assuming the network administrator is aware of [17] the increased
   size of the IPv6 address will make topology probing much harder, and
   almost impossible for IPv6 devices.  What one does when topology
   probing is to get an idea of the available hosts inside an
   enterprise.  This mostly starts with a ping-sweep.  This is an
   automated procedure of sending Internet Control Message Protocol
   (ICMP) echo requests (also known as PINGs) to a range of IP addresses
   and recording replies.  This can enable an attacker to map the
   network.  Since the IPv6 subnets are 64 bits worth of address space,
   this means that an attacker has to send out a simply unrealistic
   number of pings to map the network, and virus/worm propagation will
   be thwarted in the process.  At full rate 40Gbps (400 times the
   typical 100Mbps LAN, and 13,000 times the typical DSL/Cable access
   link) it takes over 5000 years to scan a single 64 bit space.

4.3  User/Application tracking

   IPv6 enables the collection of information about data flows.  Due to

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   the fact that all addresses used for Internet and intra-/inter- site
   communication are unique, it is possible for an enterprise or ISP to
   get very detailed information on any communication exchange between
   two or more devices.  This enhances the capability of data-flow
   tracking for security audits compared with IPv4 NAT, because in IPv6
   a flow between a sender and receiver will always be uniquely
   identified due to the unique IPv6 source and destination addresses.

4.4  Privacy and topology hiding using IPv6

   Partial host privacy is achieved in IPv6 using pseudo-random privacy
   addresses (RFC 3041) which are generated as required, so that a
   session can use an address that is valid only for a limited time.
   Exactly like IPv4 NAT, this only allows such a session to be traced
   back to the subnet that originates it, but not immediately to the
   actual host.

   If a network manager wishes to conceal the internal IPv6 topology,
   and the majority of its host computer addresses, a good option will
   be to run all internal traffic using ULA since such packets can by
   definition never exit the site.  For hosts that do in fact need to
   generate external traffic, by using multiple IPv6 addresses (ULAs and
   one or more global addresses), it will be possible to hide and mask
   some or all of the internal network.  As discussed above, there are
   multiple parts to the IPv6 address, and different techniques to
   manage privacy for each.

   When a network manager also wishes to conceal the internal IPv6
   topology, by using explicit host routes it is possible to locate
   nodes on one segment while they appear externally to be on another.
   An alternative method to hide the internal topology would be to use
   Mobile IPv6 internally without route optimization where the public
   facing addresses are consolidated on an edge Home Agent (HA), then
   use MIPv6 in bidirectional tunnel mode between the HA and topology
   masked node using the ULA as a COA.  This truly masks the internal
   topology as all nodes with global access appear to share a common
   subnet.  There is no reason that rack mounted devices couldn't be
   considered mobile nodes to mask the internal topology.  It looks
   equivalent to running a VPN to a central server, however it does not
   involve any encryption or significant overhead.

4.5  Independent control of addressing in a private network

   IPv6 provides for autonomy in local use addresses through ULAs.  At
   the same time IPv6 simplifies simultaneous use of multiple addresses
   per interface so that a NAT is not required (or even defined) between
   the ULA and the public Internet.  Nodes that need access to the
   public Internet may have a ULA for local use, and will have a global

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   use address because the global use IPv6 address space is not a scarce
   resource like the global use IPv4 space.  While global IPv6
   allocation policy is managed through the Regional Internet
   Registries, it is expected that they will continue with derivatives
   of RFC 3177 for the foreseeable future.

   When using IPv6, the need to ask for more address space will become
   far less likely due to the increased size of the subnets.  These
   subnets typically allow 2^64 hosts per subnet and an enterprise will
   typically receive a /48 which allows segmentation into at least 2^16
   different subnets.

   The ongoing subnet size maintenance may become simpler when IPv6
   technology is utilised.  If IPv4 address space is optimised one has
   periodically to look into the number of hosts on a segment and the
   subnet size allocated to the segment; an enterprise today may have a
   mix of /28 - /23 size subnets for example, and may shrink/grow these
   as their network user base/etc changes.  In v6, it's all /64.

4.6   Global address pool conservation

   IPv6 provides sufficient space to completely avoid the need for
   overlapping address space,
   340,282,366,920,938,463,463,374,607,431,768,211,456 (3.4*10^38) total
   possible addresses.  As previously discussed, the serious
   disadvantages of ambiguous address space have been well documented,
   and with sufficient space there is no need to continue the
   increasingly aggressive conservation practices that are necessary
   with IPv4.  While IPv6 allocation policies and ISP business practice
   will continue to evolve, the recommendations in RFC 3177 are based on
   the technical potential of the vast IPv6 address space.  That
   document demonstrates that there is no resource limitation which will
   lead to the IPv4 practice of ambiguous space behind a NAT.  As an
   example of the direct contrast, many expansion oriented IPv6
   deployment scenarios result in multiple IPv6 addresses per device, as
   opposed to the IPv4 constricting scenarios of multiple devices
   sharing a scarce global address.

4.7  Multihoming and renumbering

   Multihoming and renumbering remain technically challenging with IPv6
   (see the Gap Analysis below).  However, IPv6 was designed to allow
   sites and hosts to run with several simultaneous CIDR-like prefixes
   and thus with several simultaneous ISPs.  An address selection
   mechanism [9] is specified so that hosts will behave consistently
   when several addresses are simultaneously valid.  The fundamental
   difficulty that IPv4 has in this regard therefore does not apply to
   IPv6.  IPv6 sites can and do run today with multiple ISPs active, and

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   the processes for adding and removing active prefixes at a site have
   been documented [11] and [18].

   The IPv6 address space allocated by the ISP will be dependent upon
   the connecting Service provider.  This may result in a renumbering
   effort if the network changes from Service Provider.  When changing
   ISPs or ISPs readjusting their addressing pool, DHCP-PD [10] can be
   used as the zero-touch external mechanism for prefix change in
   conjunction with a ULA prefix for internal connection stability.
   With appropriate management of the lifetime values and overlap of the
   external prefixes, a smooth make-before-break transition is possible
   as existing communications will continue on the old prefix as long as
   it remains valid, while any new communications will use the new

5.  Case Studies

   It is possible to divide the type of networks in different
   categories.  This can be done on various criteria.  The criteria used
   within this document are based on the number of components or
   connections.  For each of these category of networks we can use IPv6
   Network Architecture Protection to achieve a secure and flexible
   infrastructure, which provides an enhanced network functionality in
   comparison with the usage of address translation.

   o  Medium/large private networks (typically >10 connections)
   o  Small private networks (typically 1 to 10 connections)
   o  Single user connection (typically 1 connection)
   o  ISP/Carrier customer networks

5.1  Medium/large private networks

   Under this category fall the majority of private enterprise networks.
   Many of these networks have one or more exit points to the Internet.
   Though these organizations have sufficient resources to acquire
   addressing independence there are several reasons why they might
   choose to use NAT in such a network.  For the ISP there is no need to
   import the IPv4 address range from the remote end-customer, which
   facilitates IPv4 address summarization.  The customer can use a
   larger IPv4 address range (probably with less-administrative
   overhead) by the use of RFC 1918 and NAT.  The customer also reduces
   the overhead in changing to a new ISP, because the addresses assigned
   to devices behind the NAT do not need to be changed when the customer
   is assigned a different address by a new ISP.  By using address
   translation one avoids the need for network renumbering.  Finally,
   the customer can provide privacy about its hosts and the topology of
   its internal network if the internal addresses are mapped through

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   It is expected that there will be enough IPv6 addresses available for
   all networks and appliances for the foreseeable future.  The basic
   IPv6 address-range an ISP allocates for a private network is large
   enough (currently /48) for most of the medium and large enterprises,
   while for the very large private enterprise networks address-ranges
   can be concatenated.  A single /48 alloaction provides an enterprise
   network with 65536 different /64 prefixes.

   The summarization benefit for the ISP is happening based on the IPv6
   allocation rules.  This means that the ISP will provide the
   enterprise with an IPv6 address-range (typically a one or multiple
   range(s) of '/48') from its RIR assigned IPv6 address-space.  The
   goal of this allocation mechanism is to decrease the total amount of
   entries in the internet routing table.

   To mask the identity of a user on a network of this type, the usage
   of IPv6 privacy extensions may be advised.  This technique is useful
   when an external element wants to track and collect all information
   sent and received by a certain host with known IPv6 address.  Privacy
   extensions add a random factor to the host part of an IPv6 address
   and will make it very hard for an external element to keep
   correlating the IPv6 address to a host on the inside network.  The
   usage of IPv6 privacy extensions does not mask the internal network
   structure of an enterprise network.

   If there is need to mask the internal structure towards the external
   IPv6 internet, then some form of 'Untraceable' addresses may be used.
   These addresses will be derived from a local pool, and may be
   assigned to those hosts for which topology masking is required or
   which want to reach the IPv6 Internet or other external networks.
   The technology to assign these addresses to the hosts could be based
   on DHCPv6.  To complement the 'Untraceable' addresses it is needed to
   have at least awareness of the IPv6 address location when routing an
   IPv6 packet through the internal network.  This could be achieved by
   'route-injection' in the network infrastructure.  This route-
   injection could be done based on /128 host-routes to each device that
   wants to connect to the Internet using an untraceable address.  This
   will provide the most dynamic masking, but will have a scalability
   limitation, as an IGP is typically not designed to carry many
   thousands of IPv6 prefixes.  A large enterprise may have thousands of
   hosts willing to connect to the Internet.  Less flexible masking
   could be to have time-based IPv6 prefixes per link or subnet.  This
   may reduce the amount of route entries in the IGP by a significant
   factor, but has as trade-off that masking is time and subnet based.

   The dynamic allocation of 'Untraceable' addresses can also limit the

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   IPv6 access between local and external hosts to those local hosts
   being authorized for this capability.  Dynamically allocated
   'Untraceable' addresses may also facilitate and simplify the
   connectivity to the outside networks during renumbering, because the
   existing IPv6 central address pool could be swapped for the newly
   allocated IPv6 address pool.

   The use of permanent ULA addresses on a site provides the benefit
   that even if an enterprise would change its ISP, the renumbering is
   only affecting those devices that have a wish to connect beyond the
   site.  Internal servers and services would not change their allocated
   IPv6 ULA address, and the service would remain available even during
   global address renumbering.

5.2  Small private networks

        Also known as SOHO (Small Office/Home Office) networks, this
   category describes those networks which have few routers in the
   topology, and usually have a single network egress point.  Typically
   these networks are connected via either a dial-up connection or
   broadband access; don't have dedicated Network Operation Center
   (NOC); and through economic pressure are typically forced today to
   use NAT.  In most cases the received global IPv4 prefix is not fixed
   over time and is too long to provide every node in the private
   network with a unique globally usable address.  Fixing either of
   those issues typically adds an administrative overhead for address
   management to the user.  This category may even be limited to
   receiving ambiguous IPv4 addresses from the service provider based on
   RFC 1918.  An ISP will typically pass along the higher administration
   cost attached to larger address blocks, or IPv4 prefixes that are
   static over time, due to the larger public address pool each of those

   As a direct response to explicit charges per public address most of
   this category has deployed NAPT (port demultiplexing NAT) to minimize
   the number of addresses in use.  Unfortunately this also limits the
   Internet capability of the equipment to being mainly a receiver of
   Internet data (client), and makes it quite hard for the equipment to
   become a world wide Internet server (i.e.  HTTP, FTP, etc.) due to
   the stateful operation of the NAT equipment.  Even when there is
   sufficient technical knowledge to manage the NAT to enable a server,
   only one server of any given protocol type is possible per address,
   and then only when the address from the ISP is public.

   When deploying IPv6 NAP in this environment, there are two approaches
   possible with respect to IPv6 addressing.

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   o  DHCPv6 Prefix-Delegation
   o  ISP provides a static IPv6 address-range

      For the DHCPv6-PD solution, a dynamic address allocation approach
   is chosen.  By means of the enhanced DHCPv6 protocol it is possible
   to have the ISP push down an IPv6 prefix range automatically towards
   the small private network and populate all interfaces in that small
   private network dynamically.  This reduces the burden for
   administrative overhead because everything happens automatically.

         For the static configuration the mechanisms used could be the
   same as for the medium/large enterprises.  Typically the need for
   masking the topology will not be of high priority for these users,
   and the usage of IPv6 privacy extensions could be sufficient.

      For both alternatives the ISP has the unrestricted capability for
   summarization of its RIR allocated IPv6 prefix, while the small
   private network administrator has all flexibility in using the
   received IPv6 prefix to its advantage because it will be of
   sufficient size to allow all the local nodes to have a public address
   and full range of ports available whenever necessary.

      While a full prefix is expected to be the primary deployment model
   there may be cases where the ISP provides a single IPv6 address for
   use on a single piece of equipment (PC, PDA, etc.).  This is expected
   to be rare though, because in the IPv6 world the assumption is that
   there is an unrestricted availability of a large amount of globally
   routable and unique address space.  If scarcity was the motivation
   with IPv4 to provide RFC 1918 addresses, in this environment the ISP
   will not be motivated to allocate private addresses towards the
   single user connection because there are enough global addresses
   available at essentially the same cost.  Also if the single device
   wants to mask its identity to the called party or its attack profile
   over a short time window it will need to enable IPv6 privacy
   extensions, which in turn leads to the need for a minimum allocation
   of a /64 prefix rather than a single address.

5.3  Single user connection

   This group identifies the users which are connected via a single IPv4
   address and use a single piece of equipment (PC, PDA, etc.).  This
   user may get an ambiguous IPv4 address (frequently imposed by the
   ISP) from the service provider which is based on RFC 1918.  If
   ambiguous addressing is utilized, the service provider will execute
   NAT on the allocated IPv4 address for global Internet connectivity.
   This also limits the internet capability of the equipment to being
   mainly a receiver of Internet data, and makes it quite hard for the
   equipment to become a world wide internet server (i.e.  HTTP, FTP,

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   etc.) due to the stateful operation of the NAT equipment.

   When using IPv6 NAP, this group will identify the users which are
   connected via a single IPv6 address and use a single piece of
   equipment (PC, PDA, etc.).

   In IPv6 world the assumption is that there is unrestricted
   availability of a large amount of globally routable and unique IPv6
   addresses.  The ISP will not be motivated to allocate private
   addresses towards the single user connection because he has enough
   global addresses available, if scarcity was the motivation with IPv4
   to provide RFC 1918 addresses.  If the single user wants to mask his
   identity, he may choose to enable IPv6 privacy extensions.

5.4  ISP/Carrier customer networks

   This group refers to the actual service providers that are providing
   the IPv4 access and transport services.  They tend to have three
   separate IPv4 domains that they support:
   o  For the first they fall into the Medium/large private networks
      category (above) for their own internal networks, LANs etc.
   o  The second is the Operations network which addresses their
      backbone and access switches, and other hardware, this is separate
      for both engineering reasons as well as simplicity in managing the
      security of the backbone.
   o  The third is the IP addresses (single or blocks) that they assign
      to customers.  These can be registered addresses (usually given to
      category 5.1 and 5.2 and sometimes 5.3) or can be from a pool of
      RFC 1918 addresses used with NAT for single user connections.
      Therefore they can actually have two different NAT domains that
      are not connected (internal LAN and single user customers).

   When IPv6 NAP is utilized in these three domains then for the first
   category it will be possible to use the same solutions as described
   in chapter 5.1.  The second domain of the ISP/carrier is the
   Operations network.  This environment tends to be a closed
   environment, and consequently intra- communication can be done based
   on ULA addresses.  This would give a stable configuration with
   respect to a local IPv6 address plan.  Using these local scope
   addresses would also prevent from being accessed from the external
   network.  The third is the IPv6 addresses that ISP/carrier network
   assign to customers.  These will typically be assigned with prefix
   lengths terminating on nibble boundaries to be consistent with the
   DNS PTR records.  As scarcity of IPv6 addresses is not a concern, it
   will be possible for the ISP to provide global routable IPv6 prefixes
   without a requirement for address translation.  An ISP may for
   commercial reasons still decide to restrict the capabilities of the
   end users by other means like traffic and/or route filtering etc.

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   If the carrier network is a mobile provider, then IPv6 is encouraged
   in comparison with the combination of IPv4+NAT for 3GPP attached
   devices.  When looking in chapter 2.3 of RFC3314 'Recommendations for
   IPv6 in 3GPP Standards' [14] it is found that the IPv6 WG recommends
   that one or more /64 prefixes should be assigned to each primary PDP
   context.  This will allow sufficient address space for a 3GPP-
   attached node to allocate privacy addresses and/or route to a multi-
   link subnet, and  will discourage the use of NAT within 3GPP-attached

6.  IPv6 gap analysis

      Like IPv4 and any major standards effort, IPv6 standardization
   work continues as deployments are ongoing.  This section discusses
   several topics for which additional standardization, or documentation
   of best practice, is required to fully realize the benefits of NAP.
   None of these items are show-stoppers for immediate usage of NAP in
   roles where there are no current gaps.

6.1  Completion of work on ULAs

      As noted above, a new form of Unique Local IPv6 Unicast Addresses
   (ULAs) is being standardized by the IETF.  Experience to date has
   shown that most network managers want to gain some operational
   familiarity with IPv6 in their local environment before exposing
   their network to the live global Internet.  Since these addresses
   allow autonomy for local deployment of IPv6 in private networks, this
   work should be completed as soon as possible.  In addition to
   autonomy the routing limitation of ULA addresses protects nodes that
   are only for local use from global exposure.

6.2  Subnet topology masking

      There really is no functional gap here as a centrally assigned
   pool of addresses in combination with host routes in the IGP is an
   effective way to mask topology.  If necessary a best practice
   document could be developed describing the interaction between DHCP
   and various IGPs which would in effect define Untraceable Addresses.

      As an alternative, some work in Mobile IP to define a policy
   message where a mobile node would learn from the home agent.  It
   should not even try to inform its correspondent about route
   optimization (and thereby expose its real location) would allow a
   border home agent using internal tunneling to the logically mobile
   node (potentially rack mounted) to completely mask all internal
   topology, while avoiding the strain from a large number of host
   routes in the IGP.  This work should be pursued in the IETF.

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6.3  Minimal traceability of privacy addresses

      Privacy addresses (RFC 3041) may certainly be used to limit the
   traceability of external traffic flows back to specific hosts, but
   lacking a topology masking component above they would still reveal
   the subnet address bits.  For complete privacy a best practice
   document describing the combination of privacy addresses with
   topology masking is required.  This work remains to be done, and
   should be pursued by the IETF.

6.4  Renumbering procedure

   Documentation of site renumbering procedures [11] should be
   completed.  It should also be noticed that ULAs will help here too,
   since a change of ISP prefix will only affect hosts that need an
   externally routeable address as well as a ULA.

6.5  Site multihoming

   This complex problem has never been well solved for IPv4, which is
   exactly why NAT has been used as a partial solution.  For IPv6, after
   several years' work, the relevant IETF WG is finally converging on an
   architectural approach intended to reconcile enterprise and ISP
   perspectives.  Again, ULAs will help since they will provide stable
   addressing for internal communications that are not affected by

6.6  Untraceable addresses

   The details of the untraceable addresses, along with any associated
   mechanisms such as route injection, must be worked out and specified.

7.  IANA Considerations

   This document requests no action by IANA

8.  Security Considerations

      While issues which are potentially security related are discussed
   throughout the document, the approaches herein do not introduce any
   new security concerns.  Product marketing departments have widely
   sold IPv4 NAT as a security tool, though the misleading nature of
   those claims has been previously documented in RFC 2663 [2] and RFC
   2993 [4].

      This document defines IPv6 approaches which collectively achieve
   the goals of the network manager without the negative impact on
   applications or security that are inherent in a NAT approach.  To the

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   degree that these techniques improve a network manager's ability to
   explicitly know about or control access, and thereby manage the
   overall attack exposure of local resources, they act to improve local
   network security.  In particular the explicit nature of a content
   aware firewall in NAP will be a vast security improvement over the
   NAT artifact where lack of translation state has been widely sold as
   a form of protection.

9.  Conclusion

   This document has described a number of techniques that may be
   combined on an IPv6 site to protect the integrity of its network
   architecture.  These techniques, known collectively as Network
   Architecture Protection, retain the concept of a well defined
   boundary between "inside" and "outside" the private network, and
   allow firewalling, topology hiding, and privacy.  However, because
   they preserve address transparency where it is needed, they achieve
   these goals without the disadvantage of address translation.  Thus,
   Network Architecture Protection in IPv6 can provide the benefits of
   IPv4 Network Address Translation without the corresponding

   The document has also identified a few ongoing IETF work items that
   are needed to realize 100% of the benefits of NAP.

10.  Acknowledgements

   Christian Huitema has contributed during the initial round table to
   discuss the scope and goal of the document, while the European Union
   IST 6NET project acted as a catalyst for the work documented in this
   draft.  Editorial comments and contributions have been received from:
   Fred Templin, Chao Luo, Pekka Savola, Tim Chown, Jeroen Massar,
   Salman Asadullah, Patrick Grossetete, Fred Baker, Jim Bound, Mark
   Smith, Alain Durand, John Spence, Christian Huitema and other members
   of the v6ops WG.

11.  References

11.1  Normative References

   [1]   Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and E.
         Lear, "Address Allocation for Private Internets", BCP 5,
         RFC 1918, February 1996.

   [2]   Srisuresh, P. and M. Holdrege, "IP Network Address Translator
         (NAT) Terminology and Considerations", RFC 2663, August 1999.

   [3]   Narten, T., Nordmark, E., and W. Simpson, "Neighbor Discovery

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         for IP Version 6 (IPv6)", RFC 2461, December 1998.

   [4]   Hain, T., "Architectural Implications of NAT", RFC 2993,
         November 2000.

   [5]   Srisuresh, P. and K. Egevang, "Traditional IP Network Address
         Translator (Traditional NAT)", RFC 3022, January 2001.

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

   [7]   Narten, T. and R. Draves, "Privacy Extensions for Stateless
         Address Autoconfiguration in IPv6", RFC 3041, January 2001.

   [8]   Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., and M.
         Carney, "Dynamic Host Configuration Protocol for IPv6
         (DHCPv6)", RFC 3315, July 2003.

   [9]   Draves, R., "Default Address Selection for Internet Protocol
         version 6 (IPv6)", RFC 3484, February 2003.

   [10]  Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic Host
         Configuration Protocol (DHCP) version 6", RFC 3633,
         December 2003.

   [11]  Baker, F., "Procedures for Renumbering an IPv6 Network without
         a Flag Day", draft-ietf-v6ops-renumbering-procedure-05 (work in
         progress), March 2005.

   [12]  Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
         Addresses", draft-ietf-ipv6-unique-local-addr-09 (work in
         progress), January 2005.

11.2  Informative References

   [13]  Fuller, V., Li, T., Yu, J., and K. Varadhan, "Classless Inter-
         Domain Routing (CIDR): an Address Assignment and Aggregation
         Strategy", RFC 1519, September 1993.

   [14]  Wasserman, M., "Recommendations for IPv6 in Third Generation
         Partnership Project (3GPP) Standards", RFC 3314,
         September 2002.

   [15]  Savola, P. and B. Haberman, "Embedding the Rendezvous Point
         (RP) Address in an IPv6 Multicast Address", RFC 3956,
         November 2004.

   [16]  Dupont, F. and P. Savola, "RFC 3041 Considered Harmful

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         (draft-dupont-ipv6-    rfc3041harmful-05.txt)", June 2004.

   [17]  Chown, T., "IPv6 Implications for TCP/UDP Port Scanning (chown-
         v6ops- port-scanning-implications-01.txt)", July 2004.

   [18]  Chown, T., Tompson, M., and A. Ford, "Things to think about
         when Renumbering an IPv6 network
         (draft-chown-v6ops-renumber-thinkabout-00)", October 2004.

Authors' Addresses

   Gunter Van de Velde
   Cisco Systems
   De Kleetlaan 6a
   Diegem  1831

   Phone: +32 2704 5473

   Tony Hain
   Cisco Systems
   500 108th Ave. NE
   Bellevue, Wa.


   Ralph Droms
   Cisco Systems
   1414 Massachusetts Avenue
   Boxborough, MA  01719


   Brian Carpenter
   IBM Corporation
   Sauemerstrasse 4
   Rueschlikon,   8803


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   Eric Klein
   Leon Recanati Graduate School of Business Administration at Tel
   Aviv University
   Tel Aviv,


Appendix A.  Additional benefits due to Native IPv6 and universal unique

   The users of native IPv6 technology and global unique IPv6 addresses
   have the potential to make use of the enhanced IPv6 capabilities, in
   addition to the benefits offered by the IPv4 technology.

A.1  Universal any-to-any connectivity

   One of the original design points of the Internet was any-to-any
   connectivity.  The dramatic growth of Internet connected systems
   coupled with the limited address space of the IPv4 protocol spawned
   address conservation techniques.  NAT was introduced as a tool to
   reduce demand on the limited IPv4 address pool, but the side effect
   of the NAT technology was to remove the any-to-any connectivity
   capability.  By removing the need for address conservation (and
   therefore NAT), IPv6 returns the any-to-any connectivity model and
   removes the limitations on application developers.  With the freedom
   to innovate unconstrained by NAT traversal efforts, developers will
   be able to focus on new advanced network services (i.e. peer-to-peer
   applications, IPv6 embedded IPsec communication between two
   communicating devices, instant messaging, Internet telephony, etc..)
   rather than focusing on discovering and traversing the increasingly
   complex NAT environment.

   It will also allow application and service developers to rethink the
   security model involved with any-to-any connectivity, as the current
   edge firewall solution in IPv4 may not be sufficient for Any-to-any
   service models.

A.2  Auto-configuration

   IPv6 offers a scalable approach to minimizing human interaction and
   device configuration.  Whereas IPv4 implementations require touching
   each end system to indicate the use of DHCP vs. a static address and
   management of a server with the pool size large enough for the
   potential number of connected devices, IPv6 uses an indication from
   the router to instruct the end systems to use DHCP or the stateless
   auto configuration approach supporting a virtually limitless number
   of devices on the subnet.  This minimizes the number of systems that

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   require human interaction as well as improves consistency between all
   the systems on a subnet.  In the case that there is no router to
   provide this indication, an address for use on the local link only
   will be derived from the interface media layer address.

A.3  Native Multicast services

   Multicast services in IPv4 were severely restricted by the limited
   address space available to use for group assignments and an implicit
   locally defined range for group membership.  IPv6 multicast corrects
   this situation by embedding explicit scope indications as well as
   expanding to 4 billion groups per scope.  In the source specific
   multicast case, this is further expanded to 4 billion groups per
   scope per subnet by embedding the 64 bits of subnet identifier into
   the multicast address.

   IPv6 allows also for innovative usage of the IPv6 address length, and
   makes it possible to embed the multicast 'Rendez-Vous Point' (or RP)
   [15] directly in the IPv6 multicast address when using ASM multicast.
   this is not possible with limited size of the IPv4 address.  This
   approach also simplifies the multicast model considerably, making it
   easier to understand and deploy.

A.4  Increased security protection

   The security protection offered by native IPv6 technology is more
   advanced than IPv4 technology.  There are various transport
   mechanisms enhanced to allow a network to operate more securely with
   less performance impact:
   o  IPv6 has the IPsec technology directly embedded into the IPv6
      protocol.  This allows for simpler peer-to-peer encryption and
      authentication, once a simple key/trust management model is
      developed, while the usage of some other less secure mechanisms is
      avoided (i.e. md5 password hash for neighbor authentication).
   o  On a local network, any user will have more security awareness.
      This awareness will motivate the usage of simple firewall
      applications/devices to be inserted on the border between the
      external network and the local (or home network) as there is no
      Address Translater and hance no false safety perception.
   o  All flows on the Internet will be better traceable due to a unique
      and globally routable source and destination IPv6 address.  This
      may facilitate an easier methodology for back-tracing DoS attacks
      and avoid illegal access to network resources by simpler traffic
   o  The usage of private address-space in IPv6 is now provided by
      Unique Local Addresses, which will avoid conflict situations when
      merging networks and securing the internal communication on a
      local network infrastructure due to simpler traffic filtering

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   o  The technology to enable source-routing on a network
      infrastructure has been enhanced to allow this feature to
      function, without impacting the processing power of intermediate
      network devices.  The only devices impacted with the source-
      routing will be the source and destination node and the
      intermediate source-routed nodes.  This impact behavior is
      different if IPv4 is used, because then all intermediate devices
      would have had to look into the source-route header.

A.5  Mobility

   Anytime, anywhere, universal access requires MIPv6 services in
   support of mobile nodes.  While a Home Agent is required for initial
   connection establishment in either protocol version, IPv6 mobile
   nodes are able to optimize the path between them using the MIPv6
   option header while IPv4 mobile nodes are required to triangle route
   all packets.  In general terms this will minimize the network
   resources used and maximize the quality of the communication.

A.6   Merging networks

   When two IPv4 networks want to merge it is not guaranteed that both
   networks would be using different address-ranges on some parts of the
   network infrastructure due to the legitimate usage of RFC 1918
   private addressing.  This potential overlap in address space may
   complicate a merge of two and more networks dramatically due to the
   additional IPv4 renumbering effort. i.e. when the first network has a
   service running (NTP, DNS, DHCP, HTTP, etc..) which need to be
   accessed by the 2nd merging network.  Similar address conflicts can
   happen when two network devices from these merging networks want to

   With the usage of IPv6 the addressing overlap will not exist because
   of the existence of the Unique Local Address usage for private and
   local addressing.

A.7  Community of interest

   Although some Internet-enabled devices will function as fully-fledged
   Internet hosts, it is believed that many will be operated in a highly
   restricted manner functioning largely or entirely within a Community
   of Interest.  By Community of Interest we mean a collection of hosts
   that are logically part of a group reflecting their ownership or
   function.  Typically, members of a Community of Interest need to
   communicate within the community but should not be generally
   accessible on the Internet.  They want the benefits of the
   connectivity provided by the Internet, but do not want to be exposed

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   to the rest of the world.  This functionality will be available
   through the usage of NAP and native IPv6 dataflows, without any
   stateful device in the middle.  It will also allow to build virtual
   organization networks on the fly, which is very difficult to do in
   IPv4+NAT scenarios.

Appendix B.  Revision history

B.1  Changes from *-vandevelde-v6ops-nap-00 to *-vandevelde-v6ops-nap-01
   o  Document introduction has been revised and overview table added
   o  Comments and suggestions from nap-00 draft have been included.
   o  Initial section of -00 draft 2.6 and 4.6 have been aggregated into
      a new case study section 5.
   o  The  list of additional IPv6 benefits has been been placed into
   o  new security considerations section added.
   o  GAP analysis revised.
   o  Section 2.6 and 4.6 have been included.

B.2  Changes from *-vandevelde-v6ops-nap-01 to *-ietf-v6ops-nap-00
   o  Change of Draft name from *-vandevelde-v6ops-nap-01.txt to *-ietf-
   o  Editorial changes.

B.3  Changes from *-ietf-v6ops-nap-00 to *-ietf-v6ops-nap-01
   o  Added text in Chapter 2.2 and 4.2 to address more details on
      firewall and proxy
   o  Revised Eric Klein contact details
   o  Added note in 4.2 that control over the proposed statefull-filter
      should be by a simple user-interface

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