path: root/doc/rfc/rfc7381.txt

Internet Engineering Task Force (IETF)                   K. Chittimaneni
Request for Comments: 7381                                 Dropbox, Inc.
Category: Informational                                         T. Chown
ISSN: 2070-1721                                University of Southampton
                                                               L. Howard
                                                       Time Warner Cable
                                                            V. Kuarsingh
                                                               Dyn, Inc.
                                                             Y. Pouffary
                                                         Hewlett Packard
                                                               E. Vyncke
                                                           Cisco Systems
                                                            October 2014


                 Enterprise IPv6 Deployment Guidelines

Abstract

   Enterprise network administrators worldwide are in various stages of
   preparing for or deploying IPv6 into their networks.  The
   administrators face different challenges than operators of Internet
   access providers and have reasons for different priorities.  The
   overall problem for many administrators will be to offer Internet-
   facing services over IPv6 while continuing to support IPv4, and while
   introducing IPv6 access within the enterprise IT network.  The
   overall transition will take most networks from an IPv4-only
   environment to a dual-stack network environment and eventually an
   IPv6-only operating mode.  This document helps provide a framework
   for enterprise network architects or administrators who may be faced
   with many of these challenges as they consider their IPv6 support
   strategies.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Not all documents
   approved by the IESG are a candidate for any level of Internet
   Standard; see Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc7381.



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Copyright Notice

   Copyright (c) 2014 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.





































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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   4
     1.1.  Enterprise Assumptions  . . . . . . . . . . . . . . . . .   5
     1.2.  IPv4-Only Considerations  . . . . . . . . . . . . . . . .   5
     1.3.  Reasons for a Phased Approach . . . . . . . . . . . . . .   6
   2.  Preparation and Assessment Phase  . . . . . . . . . . . . . .   7
     2.1.  Program Planning  . . . . . . . . . . . . . . . . . . . .   7
     2.2.  Inventory Phase . . . . . . . . . . . . . . . . . . . . .   8
       2.2.1.  Network Infrastructure Readiness Assessment . . . . .   8
       2.2.2.  Application Readiness Assessment  . . . . . . . . . .   9
       2.2.3.  Importance of Readiness Validation and Testing  . . .   9
     2.3.  Training  . . . . . . . . . . . . . . . . . . . . . . . .  10
     2.4.  Security Policy . . . . . . . . . . . . . . . . . . . . .  10
       2.4.1.  IPv6 Is No More Secure Than IPv4  . . . . . . . . . .  10
       2.4.2.  Similarities between IPv6 and IPv4 Security . . . . .  11
       2.4.3.  Specific Security Issues for IPv6 . . . . . . . . . .  11
     2.5.  Routing . . . . . . . . . . . . . . . . . . . . . . . . .  13
     2.6.  Address Plan  . . . . . . . . . . . . . . . . . . . . . .  14
     2.7.  Tools Assessment  . . . . . . . . . . . . . . . . . . . .  16
   3.  External Phase  . . . . . . . . . . . . . . . . . . . . . . .  17
     3.1.  Connectivity  . . . . . . . . . . . . . . . . . . . . . .  18
     3.2.  Security  . . . . . . . . . . . . . . . . . . . . . . . .  19
     3.3.  Monitoring  . . . . . . . . . . . . . . . . . . . . . . .  20
     3.4.  Servers and Applications  . . . . . . . . . . . . . . . .  20
     3.5.  Network Prefix Translation for IPv6 . . . . . . . . . . .  21
   4.  Internal Phase  . . . . . . . . . . . . . . . . . . . . . . .  21
     4.1.  Security  . . . . . . . . . . . . . . . . . . . . . . . .  22
     4.2.  Network Infrastructure  . . . . . . . . . . . . . . . . .  22
     4.3.  End-User Devices  . . . . . . . . . . . . . . . . . . . .  23
     4.4.  Corporate Systems . . . . . . . . . . . . . . . . . . . .  24
   5.  IPv6 Only . . . . . . . . . . . . . . . . . . . . . . . . . .  24
   6.  Considerations for Specific Enterprises . . . . . . . . . . .  26
     6.1.  Content Delivery Networks . . . . . . . . . . . . . . . .  26
     6.2.  Data Center Virtualization  . . . . . . . . . . . . . . .  26
     6.3.  University Campus Networks  . . . . . . . . . . . . . . .  26
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  28
   8.  Informative References  . . . . . . . . . . . . . . . . . . .  28
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  34
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  35











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1.  Introduction

   An enterprise network is defined in [RFC4057] as a network that has
   multiple internal links, one or more router connections to one or
   more providers, and is actively managed by a network operations
   entity (the "administrator", whether a single person or a department
   of administrators).  Administrators generally support an internal
   network, consisting of users' workstations; personal computers;
   mobile devices; other computing devices and related peripherals; a
   server network, consisting of accounting and business application
   servers; and an external network, consisting of Internet-accessible
   services such as web servers, email servers, VPN systems, and
   customer applications.  This document is intended as guidance for
   enterprise network architects and administrators in planning their
   IPv6 deployments.

   The business reasons for spending time, effort, and money on IPv6
   will be unique to each enterprise.  The most common drivers are due
   to the fact that when Internet service providers, including mobile
   wireless carriers, run out of IPv4 addresses, they will provide
   native IPv6 and non-native IPv4.  The non-native IPv4 service may be
   NAT64, NAT444, Dual-Stack Lite (DS-Lite), Mapping of Address and Port
   using Translation (MAP-T), Mapping of Address and Port using
   Encapsulation (MAP-E), or other transition technologies.  Compared to
   tunneled or translated service, native traffic typically performs
   better and more reliably than non-native.  For example, for client
   networks trying to reach enterprise networks, the IPv6 experience
   will be better than the transitional IPv4 if the enterprise deploys
   IPv6 in its public-facing services.  The native IPv6 network path
   should also be simpler to manage and, if necessary, troubleshoot.
   Further, enterprises doing business in growing parts of the world may
   find IPv6 growing faster there, where again potential new customers,
   employees, and partners are using IPv6.  It is thus in the
   enterprise's interest to deploy native IPv6 at the very least in its
   public-facing services but ultimately across the majority or all of
   its scope.

   The text in this document provides specific guidance for enterprise
   networks and complements other related work in the IETF, including
   [IPv6-DESIGN] and [RFC5375].











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1.1.  Enterprise Assumptions

   For the purpose of this document, we assume the following:

   o  The administrator is considering deploying IPv6 (but see
      Section 1.2 below).

   o  The administrator has existing IPv4 networks and devices that will
      continue to operate and be supported.

   o  The administrator will want to minimize the level of disruption to
      the users and services by minimizing the number of technologies
      and functions that are needed to mediate any given application.
      In other words, provide native IP wherever possible.

   Based on these assumptions, an administrator will want to use
   technologies that minimize the number of flows being tunneled,
   translated, or intercepted at any given time.  The administrator will
   choose transition technologies or strategies that both allow most
   traffic to be native and manage non-native traffic.  This will allow
   the administrator to minimize the cost of IPv6 transition
   technologies by containing the number and scale of transition
   systems.

   Tunnels used for IPv6/IPv4 transition are expected as near-/mid-term
   mechanisms, while IPv6 tunneling will be used for many long-term
   operational purposes such as security, routing control, mobility,
   multihoming, traffic engineering, etc.  We refer to the former class
   of tunnels as "transition tunnels".

1.2.  IPv4-Only Considerations

   As described in [RFC6302], administrators should take certain steps
   even if they are not considering IPv6.  Specifically, Internet-facing
   servers should log the source port number, timestamp (from a reliable
   source), and the transport protocol.  This will allow investigation
   of malefactors behind address-sharing technologies such as NAT444,
   MAP, or DS Lite.  Such logs should be protected for integrity,
   safeguarded for privacy, and periodically purged within applicable
   regulations for log retention.

   Other IPv6 considerations may impact ostensibly IPv4-only networks,
   e.g., [RFC6104] describes the rogue IPv6 Router Advertisement (RA)
   problem, which may cause problems in IPv4-only networks where IPv6 is
   enabled in end systems on that network.  Further discussion of the
   security implications of IPv6 in IPv4-only networks can be found in
   [RFC7123].




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1.3.  Reasons for a Phased Approach

   Given the challenges of transitioning user workstations, corporate
   systems, and Internet-facing servers, a phased approach allows
   incremental deployment of IPv6, based on the administrator's own
   determination of priorities.  This document outlines suggested
   phases: a Preparation and Assessment Phase, an Internal Phase, and an
   External Phase.  The Preparation Phase is highly recommended to all
   administrators, as it will save errors and complexity in later
   phases.  Each administrator must decide whether to begin with an
   External Phase (enabling IPv6 for Internet-facing systems, as
   recommended in [RFC5211]) or an Internal Phase (enabling IPv6 for
   internal interconnections first).

   Each scenario is likely to be different to some extent, but we can
   highlight some considerations:

   o  In many cases, customers outside the network will have IPv6 before
      the internal enterprise network.  For these customers, IPv6 may
      well perform better, especially for certain applications, than
      translated or tunneled IPv4, so the administrator may want to
      prioritize the External Phase such that those customers have the
      simplest and most robust connectivity to the enterprise, or at
      least its external-facing elements.

   o  Employees who access internal systems by VPN may find that their
      ISPs provide translated IPv4, which does not support the required
      VPN protocols.  In these cases, the administrator may want to
      prioritize the External Phase and any other remotely accessible
      internal systems.  It is worth noting that a number of emerging
      VPN solutions provide dual-stack connectivity; thus, a VPN service
      may be useful for employees in IPv4-only access networks to access
      IPv6 resources in the enterprise network (much like many public
      tunnel broker services, but specifically for the enterprise).
      Some security considerations are described in [RFC7359].

   o  Internet-facing servers cannot be managed over IPv6 unless the
      management systems are IPv6 capable.  These might be Network
      Management Systems (NMS), monitoring systems, or just remote
      management desktops.  Thus, in some cases, the Internet-facing
      systems are dependent on IPv6-capable internal networks.  However,
      dual-stack Internet-facing systems can still be managed over IPv4.

   o  Virtual Machines (VMs) may enable a faster rollout once initial
      system deployment is complete.  Management of VMs over IPv6 is
      still dependent on the management software supporting IPv6.





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   o  IPv6 is enabled by default on all modern operating systems, so it
      may be more urgent to manage and have visibility on the internal
      traffic.  It is important to manage IPv6 for security purposes,
      even in an ostensibly IPv4-only network, as described in
      [RFC7123].

   o  In many cases, the corporate accounting, payroll, human resource,
      and other internal systems may only need to be reachable from the
      internal network, so they may be a lower priority.  As enterprises
      require their vendors to support IPv6, more internal applications
      will support IPv6 by default, and it can be expected that
      eventually new applications will only support IPv6.  The
      inventory, as described in Section 2.2, will help determine the
      systems' readiness, as well as the readiness of the supporting
      network elements and security, which will be a consideration in
      prioritization of these corporate systems.

   o  Some large organizations (even when using private IPv4 addresses
      [RFC1918]) are facing IPv4 address exhaustion because of the
      internal network growth (for example, the vast number of VMs) or
      because of the acquisition of other companies that often raise
      private IPv4 address overlapping issues.

   o  IPv6 restores end-to-end transparency even for internal
      applications (of course security policies must still be enforced).
      When two organizations or networks merge [RFC6879], the unique
      addressing of IPv6 can make the merger much easier and faster.  A
      merger may, therefore, prioritize IPv6 for the affected systems.

   These considerations are in conflict; each administrator must
   prioritize according to their company's conditions.  It is worth
   noting that the reasons given in "A Large Corporate User's View of
   IPng", described in [RFC1687], for reluctance to deploy have largely
   been satisfied or overcome in the intervening years.

2.  Preparation and Assessment Phase

2.1.  Program Planning

   Since enabling IPv6 is a change to the most fundamental Internet
   Protocol, and since there are so many interdependencies, having a
   professional project manager organize the work is highly recommended.
   In addition, an executive sponsor should be involved in determining
   the goals of enabling IPv6 (which will establish the order of the
   phases) and should receive regular updates.

   It may be necessary to complete the Preparation Phase before
   determining whether to prioritize the Internal or External Phase,



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   since needs and readiness assessments are part of that phase.  For a
   large enterprise, it may take several iterations to really understand
   the level of effort required.  Depending on the required schedule, it
   may be useful to roll IPv6 projects into other architectural upgrades
   -- this can be an excellent way to improve the network and reduce
   costs.  However, by increasing the scope of projects, the schedule is
   often affected.  For instance, a major systems upgrade may take a
   year to complete, where just patching existing systems may take only
   a few months.

   The deployment of IPv6 will not generally stop all other technology
   work.  Once IPv6 has been identified as an important initiative, all
   projects, both new and in progress, will need to be reviewed to
   ensure IPv6 support.

   It is normal for assessments to continue in some areas while
   execution of the project begins in other areas.  This is fine, as
   long as recommendations in other parts of this document are
   considered, especially regarding security (for instance, one should
   not deploy IPv6 on a system before security has been evaluated).

2.2.  Inventory Phase

   To comprehend the scope of the Inventory Phase, we recommend dividing
   the problem space in two: network infrastructure readiness and
   applications readiness.

2.2.1.  Network Infrastructure Readiness Assessment

   The goal of this assessment is to identify the level of IPv6
   readiness of network equipment.  This will identify the effort
   required to move to an infrastructure that supports IPv6 with the
   same functional service capabilities as the existing IPv4 network.
   This may also require a feature comparison and gap analysis between
   IPv4 and IPv6 functionality on the network equipment and software.
   IPv6 support will require testing; features often work differently in
   vendors' labs than production networks.  Some devices and software
   will require IPv4 support for IPv6 to work.

   The inventory will show which network devices are already capable,
   which devices can be made IPv6 ready with a code/firmware upgrade,
   and which devices will need to be replaced.  The data collection
   consists of a network discovery to gain an understanding of the
   topology and inventory network infrastructure equipment and code
   versions with information gathered from static files and IP address
   management, DNS, and DHCP tools.





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   Since IPv6 might already be present in the environment, through
   default configurations or VPNs, an infrastructure assessment (at
   minimum) is essential to evaluate potential security risks.

2.2.2.  Application Readiness Assessment

   Just like network equipment, application software needs to support
   IPv6.  This includes OS, firmware, middleware, and applications
   (including internally developed applications).  Vendors will
   typically handle IPv6 enablement of off-the-shelf products, but often
   enterprises need to request this support from vendors.  For
   internally developed applications, it is the responsibility of the
   enterprise to enable them for IPv6.  Analyzing how a given
   application communicates over the network will dictate the steps
   required to support IPv6.  Applications should avoid instructions
   specific to a given IP address family.  Any applications that use
   APIs, such as the C language, that expose the IP version
   specifically, need to be modified to also work with IPv6.

   There are two ways to IPv6-enable applications.  The first approach
   is to have separate logic for IPv4 and IPv6, thus leaving the IPv4
   code path mainly untouched.  This approach causes the least
   disruption to the existing IPv4 logic flow, but introduces more
   complexity, since the application now has to deal with two logic
   loops with complex race conditions and error recovery mechanisms
   between these two logic loops.  The second approach is to create a
   combined IPv4/IPv6 logic, which ensures operation regardless of the
   IP version used on the network.  Knowing whether a given
   implementation will use IPv4 or IPv6 in a given deployment is a
   matter of some art; see Source Address Selection [RFC6724] and Happy
   Eyeballs [RFC6555].  It is generally recommended that the application
   developer use industry IPv6-porting tools to locate the code that
   needs to be updated.  Some discussion of IPv6 application porting
   issues can be found in [RFC4038].

2.2.3.  Importance of Readiness Validation and Testing

   Lastly, IPv6 introduces a completely new way of addressing endpoints,
   which can have ramifications at the network layer all the way up to
   the applications.  So to minimize disruption during the transition
   phase, we recommend complete functionality, scalability, and security
   testing to understand how IPv6 impacts the services and networking
   infrastructure.








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2.3.  Training

   Many organizations falter in IPv6 deployment because of a perceived
   training gap.  Training is important for those who work with
   addresses regularly, as with anyone whose work is changing.  Better
   knowledge of the reasons IPv6 is being deployed will help inform the
   assessment of who needs training and what training they need.

2.4.  Security Policy

   It is obvious that IPv6 networks should be deployed in a secure way.
   The industry has learned a lot about network security with IPv4, so
   network operators should leverage this knowledge and expertise when
   deploying IPv6.  IPv6 is not so different than IPv4: it is a
   connectionless network protocol using the same lower-layer service
   and delivering the same service to the upper layer.  Therefore, the
   security issues and mitigation techniques are mostly identical with
   the same exceptions that are described further.

2.4.1.  IPv6 Is No More Secure Than IPv4

   Some people believe that IPv6 is inherently more secure than IPv4
   because it is new.  Nothing can be more wrong.  Indeed, being a new
   protocol means that bugs in the implementations have yet to be
   discovered and fixed and that few people have the operational
   security expertise needed to operate securely an IPv6 network.  This
   lack of operational expertise is the biggest threat when deploying
   IPv6: the importance of training is to be stressed again.

   One security myth is that, thanks to its huge address space, a
   network cannot be scanned by enumerating all IPv6 addresses in a /64
   LAN; hence, a malevolent person cannot find a victim.  [RFC5157]
   describes some alternate techniques to find potential targets on a
   network, for example, enumerating all DNS names in a zone.
   Additional advice in this area is also given in [HOST-SCANNING].

   Another security myth is that IPv6 is more secure because it mandates
   the use of IPsec everywhere.  While the original IPv6 specifications
   may have implied this, [RFC6434] clearly states that IPsec support is
   not mandatory.  Moreover, if all the intra-enterprise traffic is
   encrypted, both malefactors and security tools that rely on payload
   inspection (Intrusion Prevention System (IPS), firewall, Access
   Control List (ACL), IP Flow Information Export (IPFIX) ([RFC7011] and
   [RFC7012]), etc.) will be affected.  Therefore, IPsec is as useful in
   IPv6 as in IPv4 (for example, to establish a VPN overlay over a non-
   trusted network or to reserve for some specific applications).





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   The last security myth is that amplification attacks (such as
   [SMURF]) do not exist in IPv6 because there is no more broadcast.
   Alas, this is not true as ICMP error (in some cases) or information
   messages can be generated by routers and hosts when forwarding or
   receiving a multicast message (see Section 2.4 of [RFC4443]).
   Therefore, the generation and the forwarding rate of ICMPv6 messages
   must be limited as in IPv4.

   It should be noted that in a dual-stack network, the security
   implementation for both IPv4 and IPv6 needs to be considered, in
   addition to security considerations related to the interaction of
   (and transition between) the two, while they coexist.

2.4.2.  Similarities between IPv6 and IPv4 Security

   As mentioned earlier, IPv6 is quite similar to IPv4; therefore,
   several attacks apply for both protocol families, including:

   o  Application layer attacks: such as cross-site scripting or SQL
      injection

   o  Rogue device: such as a rogue Wi-Fi access point

   o  Flooding and all traffic-based denial of services (including the
      use of control plane policing for IPv6 traffic: see [RFC6192])

   A specific case of congruence is IPv6 Unique Local Addresses (ULAs)
   [RFC4193] and IPv4 private addressing [RFC1918], which do not provide
   any security by 'magic'.  In both cases, the edge router must apply
   strict filters to block those private addresses from entering and,
   just as importantly, leaving the network.  This filtering can be done
   by the enterprise or by the ISP, but the cautious administrator will
   prefer to do it in the enterprise.

   IPv6 addresses can be spoofed as easily as IPv4 addresses, and there
   are packets with bogon IPv6 addresses (see [CYMRU]).  Anti-bogon
   filtering must be done in the data and routing planes.  It can be
   done by the enterprise or by the ISP, or both, but again the cautious
   administrator will prefer to do it in the enterprise.

2.4.3.  Specific Security Issues for IPv6

   Even if IPv6 is similar to IPv4, there are some differences that
   create some IPv6-only vulnerabilities or issues.  We give examples of
   such differences in this section.

   Privacy extension addresses [RFC4941] are usually used to protect
   individual privacy by periodically changing the interface identifier



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   part of the IPv6 address to avoid tracking a host by its otherwise
   always identical and unique 64-bit Extended Unique Identifier
   (EUI-64) based on Media Access Control (MAC).  While this presents a
   real advantage on the Internet, moderated by the fact that the prefix
   part remains the same, it complicates the task of following an audit
   trail when a security officer or network operator wants to trace back
   a log entry to a host in their network because when the tracing is
   done, the searched IPv6 address could have disappeared from the
   network.  Therefore, the use of privacy extension addresses usually
   requires additional monitoring and logging of the binding of the IPv6
   address to a data-link layer address (see also the monitoring section
   in [IPv6-SECURITY], Section 2.5).  Some early enterprise deployments
   have taken the approach of using tools that harvest IP/MAC address
   mappings from switch and router devices to provide address
   accountability; this approach has been shown to work, though it can
   involve gathering significantly more address data than in equivalent
   IPv4 networks.  An alternative is to try to prevent the use of
   privacy extension addresses by enforcing the use of DHCPv6, such that
   hosts only get addresses assigned by a DHCPv6 server.  This can be
   done by configuring routers to set the M bit in RAs, combined with
   all advertised prefixes being included without the A bit set (to
   prevent the use of stateless autoconfiguration).  Of course, this
   technique requires that all hosts support stateful DHCPv6.  It is
   important to note that not all operating systems exhibit the same
   behavior when processing RAs with the M bit set.  The varying OS
   behavior is related to the lack of prescriptive definition around the
   A, M, and O bits within the Neighbor Discovery Protocol (NDP).
   [DHCPv6-SLAAC-PROBLEM] provides a much more detailed analysis on the
   interaction of the M bit and DHCPv6.

   Extension headers complicate the task of stateless packet filters
   such as ACLs.  If ACLs are used to enforce a security policy, then
   the enterprise must verify whether its ACLs (but also stateful
   firewalls) are able to process extension headers (this means
   understand them enough to parse them to find the upper-layer
   payloads) and to block unwanted extension headers (e.g., to implement
   [RFC5095]).  This topic is discussed further in [RFC7045].

   Fragmentation is different in IPv6 because it is done only by the
   source host and never during a forwarding operation.  This means that
   ICMPv6 packet-too-big messages must be allowed to pass through the
   network and not be filtered [RFC4890].  Fragments can also be used to
   evade some security mechanisms such as RA-Guard [RFC6105].  See also
   [RFC5722] and [RFC7113].

   One of the biggest differences between IPv4 and IPv6 is the
   introduction of NDP [RFC4861], which includes a variety of important
   IPv6 protocol functions, including those provided in IPv4 by the



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   Address Resolution Protocol (ARP) [RFC0826].  NDP runs over ICMPv6
   (which as stated above means that security policies must allow some
   ICMPv6 messages to pass, as described in RFC 4890), but has the same
   lack of security as, for example, ARP, in that there is no inherent
   message authentication.  While Secure Neighbor Discovery (SEND)
   [RFC3971] and Cryptographically Generated Addresses (CGAs) [RFC3972]
   have been defined, they are not widely implemented).  The threat
   model for RAs within the NDP suite is similar to that of DHCPv4 (and
   DHCPv6), in that a rogue host could be either a rogue router or a
   rogue DHCP server.  An IPv4 network can be made more secure with the
   help of DHCPv4 snooping in edge switches, and likewise RA snooping
   can improve IPv6 network security (in IPv4-only networks as well).
   Thus, enterprises using such techniques for IPv4 should use the
   equivalent techniques for IPv6, including RA-Guard [RFC6105] and all
   work in progress from the Source Address Validation Improvement
   (SAVI) WG, e.g., [RFC6959], which is similar to the protection given
   by dynamic ARP monitoring in IPv4.  Other DoS vulnerabilities are
   related to NDP cache exhaustion, and mitigation techniques can be
   found in ([RFC6583]).

   As stated previously, running a dual-stack network doubles the attack
   exposure as a malevolent person has now two attack vectors: IPv4 and
   IPv6.  This simply means that all routers and hosts operating in a
   dual-stack environment with both protocol families enabled (even if
   by default) must have a congruent security policy for both protocol
   versions.  For example, permit TCP ports 80 and 443 to all web
   servers and deny all other ports to the same servers must be
   implemented both for IPv4 and IPv6.  It is thus important that the
   tools available to administrators readily support such behavior.

2.5.  Routing

   An important design choice to be made is what IGP is to use inside
   the network.  A variety of IGPs (IS-IS, OSPFv3, and Routing
   Information Protocol Next Generation (RIPng)) support IPv6 today, and
   picking one over the other is a design choice that will be dictated
   mostly by existing operational policies in an enterprise network.  As
   mentioned earlier, it would be beneficial to maintain operational
   parity between IPv4 and IPv6; therefore, it might make sense to
   continue using the same protocol family that is being used for IPv4.
   For example, in a network using OSPFv2 for IPv4, it might make sense
   to use OSPFv3 for IPv6.  It is important to note that although OSPFv3
   is similar to OSPFv2, they are not the same.  On the other hand, some
   organizations may chose to run different routing protocols for
   different IP versions.  For example, one may chose to run OSPFv2 for
   IPv4 and IS-IS for IPv6.  An important design question to consider
   here is whether to support one IGP or two different IGPs in the
   longer term.  [IPv6-DESIGN] presents advice on the design choices



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   that arise when considering IGPs and discusses the advantages and
   disadvantages to different approaches in detail.

2.6.  Address Plan

   The most common problem encountered in IPv6 networking is in applying
   the same principles of conservation that are so important in IPv4.
   IPv6 addresses do not need to be assigned conservatively.  In fact, a
   single, larger allocation is considered more conservative than
   multiple non-contiguous small blocks because a single block occupies
   only a single entry in a routing table.  The advice in [RFC5375] is
   still sound and is recommended to the reader.  If considering ULAs,
   give careful thought to how well it is supported, especially in
   multiple address and multicast scenarios, and assess the strength of
   the requirement for ULA.  [ULA-USAGE] provides much more detailed
   analysis and recommendations on the usage of ULAs.

   The enterprise administrator will want to evaluate whether the
   enterprise will request address space from a Local Internet Registry
   (LIR) such as an ISP; a Regional Internet Registry (RIR) such as
   AfriNIC, APNIC, ARIN, LACNIC, or RIPE-NCC; or a National Internet
   Registry (NIR) operated in some countries.  The normal allocation is
   Provider-Aggregated (PA) address space from the enterprise's ISP, but
   use of PA space implies renumbering when changing providers.
   Instead, an enterprise may request Provider-Independent (PI) space;
   this may involve an additional fee, but the enterprise may then be
   better able to be multihomed using that prefix and will avoid a
   renumbering process when changing ISPs (though it should be noted
   that renumbering caused by outgrowing the space, merger, or other
   internal reason would still not be avoided with PI space).

   The type of address selected (PI vs. PA) should be congruent with the
   routing needs of the enterprise.  The selection of address type will
   determine if an operator will need to apply new routing techniques
   and may limit future flexibility.  There is no right answer, but the
   needs of the External Phase may affect what address type is selected.

   Each network location or site will need a prefix assignment.
   Depending on the type of site/location, various prefix sizes may be
   used.  In general, historical guidance suggests that each site should
   get at least a /48, as documented in RFC 5375 and [RFC6177].  In
   addition to allowing for simple planning, this can allow a site to
   use its prefix for local connectivity, should the need arise, and if
   the local ISP supports it.

   When assigning addresses to end systems, the enterprise may use
   manually configured addresses (common on servers) or Stateless
   Address Autoconfiguration (SLAAC) or DHCPv6 for client systems.



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   Early IPv6 enterprise deployments have used SLAAC both for its
   simplicity and the time DHCPv6 has taken to mature.  However, DHCPv6
   is now very mature; thus, workstations managed by an enterprise may
   use stateful DHCPv6 for addressing on corporate LAN segments.  DHCPv6
   allows for the additional configuration options often employed by
   enterprise administrators, and by using stateful DHCPv6,
   administrators correlating system logs know which system had which
   address at any given time.  Such an accountability model is familiar
   from IPv4 management, though DHCPv6 hosts are identified by a DHCP
   Unique Identifier (DUID) rather than a MAC address.  For equivalent
   accountability with SLAAC (and potentially privacy addresses), a
   monitoring system that harvests IP/MAC mappings from switch and
   router equipment could be used.

   A common deployment consideration for any enterprise network is how
   to get host DNS records updated.  Commonly, either the host will send
   DNS updates or the DHCP server will update records.  If there is
   sufficient trust between the hosts and the DNS server, the hosts may
   update (and the enterprise may use SLAAC for addressing).  Otherwise,
   the DHCPv6 server can be configured to update the DNS server.  Note
   that an enterprise network with this more controlled environment will
   need to disable SLAAC on network segments and force end hosts to use
   DHCPv6 only.

   In the data center or server room, assume a /64 per VLAN.  This
   applies even if each individual system is on a separate VLAN.  In a
   /48 assignment, typical for a site, there are then still 65,535 /64
   blocks.  Some administrators reserve a /64 but configure a small
   subnet, such as /112, /126, or /127, to prevent rogue devices from
   attaching and getting numbers; an alternative is to monitor traffic
   for surprising addresses or Neighbor Discovery (ND) tables for new
   entries.  Addresses are either configured manually on the server or
   reserved on a DHCPv6 server, which may also synchronize forward and
   reverse DNS (though see [RFC6866] for considerations on static
   addressing).  SLAAC is not recommended for servers because of the
   need to synchronize RA timers with DNS Times to Live (TTLs) so that
   the DNS entry expires at the same time as the address.

   All user access networks should be a /64.  Point-to-point links where
   NDP is not used may also utilize a /127 (see [RFC6164]).

   Plan to aggregate at every layer of network hierarchy.  There is no
   need for variable length subnet mask (VLSM) [RFC1817] in IPv6, and
   addressing plans based on conservation of addresses are shortsighted.
   Use of prefixes longer then /64 on network segments will break common
   IPv6 functions such as SLAAC [RFC4862].  Where multiple VLANs or
   other Layer 2 domains converge, allow some room for expansion.
   Renumbering due to outgrowing the network plan is a nuisance, so



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   allow room within it.  Generally, plan to grow to about twice the
   current size that can be accommodated; where rapid growth is planned,
   allow for twice that growth.  Also, if DNS (or reverse DNS) authority
   may be delegated to others in the enterprise, assignments need to be
   on nibble boundaries (that is, on a multiple of 4 bits, such as /64,
   /60, /56, ..., /48, /44), to ensure that delegated zones align with
   assigned prefixes.

   If using ULAs, it is important to note that AAAA and PTR records for
   ULAs are not recommended to be installed in the global DNS.
   Similarly, reverse (address-to-name) queries for ULA must not be sent
   to name servers outside of the organization, due to the load that
   such queries would create for the authoritative name servers for the
   ip6.arpa zone.  For more details, please refer to Section 4.4 of
   [RFC4193].

   Enterprise networks are increasingly including virtual networks where
   a single, physical node may host many virtualized addressable
   devices.  It is imperative that the addressing plans assigned to
   these virtual networks and devices be consistent and non-overlapping
   with the addresses assigned to real networks and nodes.  For example,
   a virtual network established within an isolated lab environment may,
   at a later time, become attached to the production enterprise
   network.

2.7.  Tools Assessment

   Enterprises will often have a number of operational tools and support
   systems that are used to provision, monitor, manage, and diagnose the
   network and systems within their environment.  These tools and
   systems will need to be assessed for compatibility with IPv6.  The
   compatibility may be related to the addressing and connectivity of
   various devices as well as IPv6 awareness of the tools and processing
   logic.

   The tools within the organization fall into two general categories:
   those that focus on managing the network and those that are focused
   on managing systems and applications on the network.  In either
   instance, the tools will run on platforms that may or may not be
   capable of operating in an IPv6 network.  This lack in functionality
   may be related to operating system version or based on some hardware
   constraint.  Those systems that are found to be incapable of
   utilizing an IPv6 connection, or which are dependent on an IPv4
   stack, may need to be replaced or upgraded.

   In addition to devices working on an IPv6 network natively, or via a
   transition tunnel, many tools and support systems may require
   additional software updates to be IPv6 aware or even a hardware



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   upgrade (usually for additional memory, IPv6 addresses are larger and
   for a while, IPv4 and IPv6 addresses will coexist in the tool).  This
   awareness may include the ability to manage IPv6 elements and/or
   applications in addition to the ability to store and utilize IPv6
   addresses.

   Considerations when assessing the tools and support systems may
   include the fact that IPv6 addresses are significantly larger than
   IPv4, requiring data stores to support the increased size.  Such
   issues are among those discussed in [RFC5952].  Many organizations
   may also run dual-stack networks; therefore, the tools need to not
   only support IPv6 operation but may also need to support the
   monitoring, management, and intersection with both IPv6 and IPv4
   simultaneously.  It is important to note that managing IPv6 is not
   just constrained to using large IPv6 addresses, but also that IPv6
   interfaces and nodes are likely to use two or more addresses as part
   of normal operation.  Updating management systems to deal with these
   additional nuances will likely consume time and considerable effort.

   For networking systems, like node management systems, it is not
   always necessary to support local IPv6 addressing and connectivity.
   Operations such as SNMP MIB polling can occur over IPv4 transport
   while seeking responses related to IPv6 information.  Where this may
   seem advantageous to some, it should be noted that without local IPv6
   connectivity, the management system may not be able to perform all
   expected functions -- such as reachability and service checks.

   Organizations should be aware that changes to older IPv4-only SNMP
   MIB specifications have been made by the IETF and are related to
   legacy operation in [RFC2096] and [RFC2011].  Updated specifications
   are now available in [RFC4292] and [RFC4293] that modified the older
   MIB framework to be IP protocol agnostic, supporting both IPv4 and
   IPv6.  Polling systems will need to be upgraded to support these
   updates as well as the end stations, which are polled.

3.  External Phase

   The External Phase for enterprise IPv6 adoption covers topics that
   deal with how an organization connects its infrastructure to the
   external world.  These external connections may be toward the
   Internet at large or to other networks.  The External Phase covers
   connectivity, security and monitoring of various elements, and
   outward-facing or accessible services.








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3.1.  Connectivity

   The enterprise will need to work with one or more service providers
   to gain connectivity to the Internet or transport service
   infrastructure such as a BGP/MPLS IP VPN as described in [RFC4364]
   and [RFC4659].  One significant factor that will guide how an
   organization may need to communicate with the outside world will
   involve the use of PI and/or PA IPv6 space.

   Enterprises should be aware that, depending on which address type
   they selected (PI vs. PA) in their planning phase, they may need to
   implement new routing functions and/or behaviors to support their
   connectivity to the ISP.  In the case of PI, the upstream ISP may
   offer options to route the prefix (typically a /48) on the
   enterprise's behalf and update the relevant routing databases.
   Otherwise, the enterprise may need to perform this task on their own
   and use BGP to inject the prefix into the global BGP system.

   Note that the rules set by the RIRs for an enterprise acquiring PI
   address space have changed over time.  For example, in the European
   region, the RIPE-NCC no longer requires an enterprise to be
   multihomed to be eligible for an IPv6 PI allocation.  Requests can be
   made directly or via a LIR.  It is possible that the rules may change
   again and may vary between RIRs.

   When seeking IPv6 connectivity to a service provider, native IPv6
   connectivity is preferred since it provides the most robust and
   efficient form of connectivity.  If native IPv6 connectivity is not
   possible due to technical or business limitations, the enterprise may
   utilize readily available transition tunnel IPv6 connectivity.  There
   are IPv6 transit providers that provide robust tunneled IPv6
   connectivity that can operate over IPv4 networks.  It is important to
   understand the transition-tunnel mechanism used and to consider that
   it will have higher latency than native IPv4 or IPv6, and may have
   other problems, e.g., related to MTUs.

   It is important to evaluate MTU considerations when adding IPv6 to an
   existing IPv4 network.  It is generally desirable to have the IPv6
   and IPv4 MTU congruent to simplify operations (so the two address
   families behave similarly, that is, as expected).  If the enterprise
   uses transition tunnels inside or externally for IPv6 connectivity,
   then modification of the MTU on hosts/routers may be needed as mid-
   stream fragmentation is no longer supported in IPv6.  It is preferred
   that Path MTU Discovery (pMTUD) be used to optimize the MTU, so
   erroneous filtering of the related ICMPv6 message types should be
   monitored.  Adjusting the MTU may be the only option if undesirable
   upstream ICMPv6 filtering cannot be removed.




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3.2.  Security

   The most important part of security for external IPv6 deployment is
   filtering and monitoring.  Filtering can be done by stateless ACLs or
   a stateful firewall.  The security policies must be consistent for
   IPv4 and IPv6 (or else the attacker will use the less-protected
   protocol stack), except that certain ICMPv6 messages must be allowed
   through and to the filtering device (see [RFC4890]):

   o  Packet Too Big: essential to allow Path MTU discovery to work

   o  Parameter Problem

   o  Time Exceeded

   In addition, NDP messages (including Neighbor Solicitation, RAs,
   etc.) are required for local hosts.

   It could also be safer to block all fragments where the transport
   layer header is not in the first fragment to avoid attacks as
   described in [RFC5722].  Some filtering devices allow this filtering.
   Ingress filters and firewalls should follow [RFC5095] in handling
   routing extension header type 0, dropping the packet and sending
   ICMPv6 Parameter Problem, unless Segments Left = 0 (in which case,
   ignore the header).

   If an IPS is used for IPv4 traffic, then an IPS should also be used
   for IPv6 traffic.  In general, make sure IPv6 security is at least as
   good as IPv4.  This also includes all email content protection (anti-
   spam, content filtering, data leakage prevention, etc.).

   The edge router must also implement anti-spoofing techniques based on
   [RFC2827] (also known as BCP 38).

   In order to protect the networking devices, it is advised to
   implement control plane policing as per [RFC6192].

   The potential NDP cache exhaustion attack (see [RFC6583]) can be
   mitigated by two techniques:

   o  Good NDP implementation with memory utilization limits as well as
      rate limiters and prioritization of requests.

   o  Or, as the external deployment usually involves just a couple of
      exposed statically configured IPv6 addresses (virtual addresses of
      web, email, and DNS servers), then it is straightforward to build
      an ingress ACL allowing traffic for those addresses and denying
      traffic to any other addresses.  This actually prevents the attack



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      as a packet for a random destination will be dropped and will
      never trigger a neighbor resolution.

3.3.  Monitoring

   Monitoring the use of the Internet connectivity should be done for
   IPv6 as it is done for IPv4.  This includes the use of IPFIX
   [RFC7012] to report abnormal traffic patterns (such as port scanning,
   SYN flooding, and related IP source addresses) from monitoring tools
   and evaluating data read from SNMP MIBs [RFC4293] (some of which also
   enable the detection of abnormal bandwidth utilization) and syslogs
   (finding server and system errors).  Where NetFlow is used, Version 9
   is required for IPv6 support.  Monitoring systems should be able to
   examine IPv6 traffic, use IPv6 for connectivity, and record IPv6
   addresses, and any log parsing tools and reporting need to support
   IPv6.  Some of this data can be sensitive (including personally
   identifiable information) and care in securing it should be taken,
   with periodic purges.  Integrity protection on logs and sources of
   log data is also important to detect unusual behavior
   (misconfigurations or attacks).  Logs may be used in investigations,
   which depend on trustworthy data sources (tamper resistant).

   In addition, monitoring of external services (such as web sites)
   should be made address specific, so that people are notified when
   either the IPv4 or IPv6 version of a site fails.

3.4.  Servers and Applications

   The path to the servers accessed from the Internet usually involves
   security devices (firewall and IPS), server load balancing (SLB), and
   real physical servers.  The latter stage is also multi-tiered for
   scalability and security between presentation and data storage.  The
   ideal transition is to enable native dual stack on all devices; but
   as part of the phased approach, operators have used the following
   techniques with success:

   o  Use a network device to apply NAT64 and basically translate an
      inbound TCP connection (or any other transport protocol) over IPv6
      into a TCP connection over IPv4.  This is the easiest to deploy as
      the path is mostly unchanged, but it hides all IPv6 remote users
      behind a single IPv4 address, which leads to several audit trail
      and security issues (see [RFC6302]).

   o  Use the server load balancer, which acts as an application proxy
      to do this translation.  Compared to the NAT64, it has the
      potential benefit of going through the security devices as native
      IPv6 (so more audit and trace abilities) and is also able to
      insert an HTTP X-Forward-For header that contains the remote IPv6



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      address.  The latter feature allows for logging and rate limiting
      on the real servers based on the IPV6 address even if those
      servers run only IPv4.

   In either of these cases, care should be taken to secure logs for
   privacy reasons and to periodically purge them.

3.5.  Network Prefix Translation for IPv6

   Network Prefix Translation for IPv6, or NPTv6 as described in
   [RFC6296], provides a framework to utilize prefix ranges within the
   internal network that are separate (address independent) from the
   assigned prefix from the upstream provider or registry.  As mentioned
   above, while NPTv6 has potential use cases in IPv6 networks, the
   implications of its deployment need to be fully understood,
   particularly where any applications might embed IPv6 addresses in
   their payloads.

   Use of NPTv6 can be chosen independently from how addresses are
   assigned and routed within the internal network, how prefixes are
   routed towards the Internet, or whether PA or PI addresses are used.

4.  Internal Phase

   This phase deals with the delivery of IPv6 to the internal user-
   facing side of the Information Technology (IT) infrastructure, which
   comprises various components such as network devices (routers,
   switches, etc.), end-user devices and peripherals (workstations,
   printers, etc.), and internal corporate systems.

   An important design paradigm to consider during this phase is "dual
   stack when you can, tunnel when you must".  Dual stacking allows a
   more robust, production-quality IPv6 network than is typically
   facilitated by internal use of transition tunnels that are harder to
   troubleshoot and support, and that may introduce scalability and
   performance issues.  Of course, tunnels may still be used in
   production networks, but their use needs to be carefully considered,
   e.g., where the transition tunnel may be run through a security or
   filtering device.  Tunnels do also provide a means to experiment with
   IPv6 and gain some operational experience with the protocol.
   [RFC4213] describes various transition mechanisms in more detail.
   [RFC6964] suggests operational guidance when using Intra-Site
   Automatic Tunnel Addressing Protocol (ISATAP) tunnels [RFC5214],
   though we would recommend use of dual stack wherever possible.







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4.1.  Security

   IPv6 must be deployed in a secure way.  This means that all existing
   IPv4 security policies must be extended to support IPv6; IPv6
   security policies will be the IPv6 equivalent of the existing IPv4
   ones (taking into account the difference for ICMPv6 [RFC4890]).  As
   in IPv4, security policies for IPv6 will be enforced by firewalls,
   ACL, IPS, VPN, and so on.

   Privacy extension addresses [RFC4941] raise a challenge for an audit
   trail as explained in Section 2.4.3 of this document.  The enterprise
   may choose to attempt to enforce use of DHCPv6 or deploy monitoring
   tools that harvest accountability data from switches and routers
   (thus making the assumption that devices may use any addresses inside
   the network).

   One major issue is threats against ND.  This means, for example, that
   the internal network at the access layer (where hosts connect to the
   network over wired or wireless) should implement RA-Guard [RFC6105]
   and the techniques being specified by the SAVI WG [RFC6959]; see also
   Section 2.4.3 of this document for more information.

4.2.  Network Infrastructure

   The typical enterprise network infrastructure comprises a combination
   of the following network elements -- wired access switches, wireless
   access points, and routers (although it is fairly common to find
   hardware that collapses switching and routing functionality into a
   single device).  Basic wired access switches and access points
   operate only at the physical and link layers and don't really have
   any special IPv6 considerations other than being able to support IPv6
   addresses themselves for management purposes.  In many instances,
   these devices possess a lot more intelligence than simply switching
   packets.  For example, some of these devices help assist with link-
   layer security by incorporating features such as ARP inspection and
   DHCP snooping, or they may help limit where multicast floods by using
   IGMP (or, in the case of IPv6, Multicast Listener Discovery (MLD))
   snooping.

   Another important consideration in enterprise networks is first-hop
   router redundancy.  This directly ties into network reachability from
   an end host's point of view.  IPv6 ND [RFC4861] provides a node with
   the capability to maintain a list of available routers on the link,
   in order to be able to switch to a backup path should the primary be
   unreachable.  By default, ND will detect a router failure in 38
   seconds and cycle onto the next default router listed in its cache.
   While this feature provides a basic level of first-hop router
   redundancy, most enterprise IPv4 networks are designed to fail over



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   much faster.  Although this delay can be improved by adjusting the
   default timers, care must be taken to protect against transient
   failures and to account for increased traffic on the link.  Another
   option in which to provide robust first-hop redundancy is to use the
   Virtual Router Redundancy Protocol Version 3 (VRRPv3) for IPv6
   [RFC5798].  This protocol provides a much faster switchover to an
   alternate default router than default ND parameters.  Using VRRPv3, a
   backup router can take over for a failed default router in around
   three seconds (using VRRPv3 default parameters).  This is done
   without any interaction with the hosts and a minimum amount of VRRP
   traffic.

   Last but not least, one of the most important design choices to make
   while deploying IPv6 on the internal network is whether to use SLAAC
   [RFC4862], the Dynamic Host Configuration Protocol for IPv6 (DHCPv6)
   [RFC3315], or a combination thereof.  Each option has advantages and
   disadvantages, and the choice will ultimately depend on the
   operational policies that guide each enterprise's network design.
   For example, if an enterprise is looking for ease of use, rapid
   deployment, and less administrative overhead, then SLAAC makes more
   sense for workstations.  Manual or DHCPv6 assignments are still
   needed for servers, as described in the Address Plan and External
   Phase sections of this document; see Sections 2.6 and 3,
   respectively.  However, if the operational policies call for precise
   control over IP address assignment for auditing, then DHCPv6 may be
   preferred.  DHCPv6 also allows you to tie into DNS systems for host
   entry updates and gives you the ability to send other options and
   information to clients.  It is worth noting that in general
   operation, RAs are still needed in DHCPv6 networks, as there is no
   DHCPv6 Default Gateway option.  Similarly, DHCPv6 is needed in RA
   networks for other configuration information, e.g., NTP servers or,
   in the absence of support for DNS resolvers in RAs [RFC6106], DNS
   resolver information.

4.3.  End-User Devices

   Most operating systems (OSes) that are loaded on workstations and
   laptops in a typical enterprise support IPv6 today.  However, there
   are various out-of-the-box nuances that one should be mindful about.
   For example, the default behavior of OSes vary; some may have IPv6
   turned off by default, some may only have certain features such as
   privacy extensions to IPv6 addresses (RFC 4941) turned off, while
   others have IPv6 fully enabled.  Further, even when IPv6 is enabled,
   the choice of which address is used may be subject to source address
   selection (RFC 6724) and Happy Eyeballs (RFC 6555).  Therefore, it is
   advised that enterprises investigate the default behavior of their
   installed OS base and account for it during the Inventory Phases of
   their IPv6 preparations.  Furthermore, some OSes may have some



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   transition tunneling mechanisms turned on by default, and in such
   cases, it is recommended to administratively shut down such
   interfaces unless required.

   It is important to note that it is recommended that IPv6 be deployed
   at the network and system infrastructure level before it is rolled
   out to end-user devices; ensure IPv6 is running and routed on the
   wire, and secure and correctly monitored, before exposing IPv6 to end
   users.

   Smartphones and tablets are significant IPv6-capable platforms,
   depending on the support of the carrier's data network.

   IPv6 support for peripherals varies.  Much like servers, printers are
   generally configured with a static address (or DHCP reservation) so
   clients can discover them reliably.

4.4.  Corporate Systems

   No IPv6 deployment will be successful without ensuring that all the
   corporate systems that an enterprise uses as part of its IT
   infrastructure support IPv6.  Examples of such systems include, but
   are not limited to, email, video conferencing, telephony (VoIP), DNS,
   RADIUS, etc.  All these systems must have their own detailed IPv6
   rollout plan in conjunction with the network IPv6 rollout.  It is
   important to note that DNS is one of the main anchors in an
   enterprise deployment, since most end hosts decide whether or not to
   use IPv6 depending on the presence of IPv6 AAAA records in a reply to
   a DNS query.  It is recommended that system administrators
   selectively turn on AAAA records for various systems as and when they
   are IPv6 enabled; care must be taken though to ensure all services
   running on that host name are IPv6 enabled before adding the AAAA
   record.  Care with web proxies is advised; a mismatch in the level of
   IPv6 support between the client, proxy, and server can cause
   communication problems.  All monitoring and reporting tools across
   the enterprise will need to be modified to support IPv6.

5.  IPv6 Only

   Early IPv6 enterprise deployments have generally taken a dual-stack
   approach to enabling IPv6, i.e., the existing IPv4 services have not
   been turned off.  Although IPv4 and IPv6 networks will coexist for a
   long time, the long-term enterprise network roadmap should include
   steps to simplify engineering and operations by deprecating IPv4 from
   the dual-stack network.  In some extreme cases, deploying dual-stack
   networks may not even be a viable option for very large enterprises
   due to the address space described in RFC 1918 not being large enough
   to support the network's growth.  In such cases, deploying IPv6-only



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   networks might be the only choice available to sustain network
   growth.  In other cases, there may be elements of an otherwise dual-
   stack network that may be run in IPv6 only.

   If nodes in the network don't need to talk to an IPv4-only node, then
   deploying IPv6-only networks should be straightforward.  However,
   most nodes will need to communicate with some IPv4-only nodes; an
   IPv6-only node may, therefore, require a translation mechanism.  As
   [RFC6144] points out, it is important to look at address translation
   as a transition strategy towards running an IPv6-only network.

   There are various stateless and stateful IPv4/IPv6 translation
   methods available today that help IPv6-to-IPv4 communication.  RFC
   6144 provides a framework for IPv4/IPv6 translation and describes in
   detail various scenarios in which such translation mechanisms could
   be used.  [RFC6145] describes stateless address translation.  In this
   mode, a specific IPv6 address range will represent IPv4 systems
   (IPv4-converted addresses), and the IPv6 systems have addresses
   (IPv4-translatable addresses) that can be algorithmically mapped to a
   subset of the service provider's IPv4 addresses.  NAT64 [RFC6146]
   describes stateful address translation.  As the name suggests, the
   translation state is maintained between IPv4 address/port pairs and
   IPv6 address/port pairs, enabling IPv6 systems to open sessions with
   IPv4 systems.  DNS64 [RFC6147] describes a mechanism for synthesizing
   AAAA resource records (RRs) from A RRs.  Together, RFCs 6146 and RFC
   6147 provide a viable method for an IPv6-only client to initiate
   communications to an IPv4-only server.  As described in Enterprise
   Assumptions, Section 1.1, the administrator will usually want most
   traffic or flows to be native and only translate as needed.

   The address translation mechanisms for the stateless and stateful
   translations are defined in [RFC6052].  It is important to note that
   both of these mechanisms have limitations as to which protocols they
   support.  For example, RFC 6146 only defines how stateful NAT64
   translates unicast packets carrying TCP, UDP, and ICMP traffic only.
   The classic problems of IPv4 NAT also apply, e.g., handling IP
   literals in application payloads.  The ultimate choice of which
   translation mechanism to chose will be dictated mostly by existing
   operational policies pertaining to application support, logging
   requirements, etc.

   There is additional work being done in the area of address
   translation to enhance and/or optimize current mechanisms.  For
   example, [DIVI] describes limitations with the current stateless
   translation, such as IPv4 address sharing and application layer
   gateway (ALG) problems, and presents the concept and implementation
   of dual-stateless IPv4/IPv6 translation (dIVI) to address those
   issues.



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   It is worth noting that for IPv6-only access networks that use
   technologies such as NAT64, the more content providers (and
   enterprises) that make their content available over IPv6, the less
   the requirement to apply NAT64 to traffic leaving the access network.
   This particular point is important for enterprises that may start
   their IPv6 deployment well into the global IPv6 transition.  As time
   progresses, and given the current growth in availability of IPv6
   content, IPv6-only operation using NAT64 to manage some flows will
   become less expensive to run versus the traditional NAT44 deployments
   since only IPv6-to-IPv4 flows need translation.  [RFC6883] provides
   guidance and suggestions for Internet Content Providers and
   Application Service Providers in this context.

   Enterprises should also be aware that networks may be subject to
   future convergence with other networks (i.e., mergers, acquisitions,
   etc.).  An enterprise considering IPv6-only operation may need to be
   aware that additional transition technologies and/or connectivity
   strategies may be required depending on the level of IPv6 readiness
   and deployment in the merging networking.

6.  Considerations for Specific Enterprises

6.1.  Content Delivery Networks

   Some guidance for Internet Content and Application Service Providers
   can be found in [RFC6883], which includes a dedicated section on
   Content Delivery Networks (CDNs).  An enterprise that relies on a CDN
   to deliver a 'better' e-commerce experience needs to ensure that
   their CDN provider also supports IPv4/IPv6 traffic selection so that
   they can ensure 'best' access to the content.  A CDN could enable
   external IPv6 content delivery even if the enterprise provides that
   content over IPv4.

6.2.  Data Center Virtualization

   IPv6 Data Center considerations are described in [IPv6-DC].

6.3.  University Campus Networks

   A number of campus networks around the world have made some initial
   IPv6 deployments.  This has been encouraged by their National
   Research and Education Network (NREN) backbones, having made IPv6
   available natively since the early 2000's.  Universities are a
   natural place for IPv6 deployment to be considered at an early stage,
   perhaps compared to other enterprises, as they are involved by their
   very nature in research and education.





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   Campus networks can deploy IPv6 at their own pace; there is no need
   to deploy IPv6 across the entire enterprise from day one.  Rather,
   specific projects can be identified for an initial deployment that
   are both deep enough to give the university experience but small
   enough to be a realistic first step.  There are generally three areas
   in which such deployments are currently made.

   In particular, those initial areas commonly approached are:

   o  External-facing services.  Typically, the campus web presence and
      commonly also external-facing DNS and mail exchange (MX) services.
      This ensures early IPv6-only adopters elsewhere can access the
      campus services as simply and as robustly as possible.

   o  Computer science department.  This is where IPv6-related research
      and/or teaching is most likely to occur, and where many of the
      next generation of network engineers are studying, so enabling
      some or all of the campus computer science department network is a
      sensible first step.

   o  The eduroam wireless network.  Eduroam [EDUROAM] is the de facto
      wireless roaming system for academic networks and uses
      authentication based on 802.1X, which is agnostic to the IP
      version used (unlike web-redirection gateway systems).  Making a
      campus' eduroam network dual stack is a very viable early step.

   The general IPv6 deployment model in a campus enterprise will still
   follow the general principles described in this document.  While the
   above early stage projects are commonly followed, these still require
   the campus to acquire IPv6 connectivity and address space from their
   NREN (or other provider in some parts of the world) and to enable
   IPv6 on the wire on at least part of the core of the campus network.
   This implies a requirement to have an initial address plan, and to
   ensure appropriate monitoring and security measures are in place, as
   described elsewhere in this document.

   Campuses that have deployed to date do not use ULAs, nor do they use
   NPTv6.  In general, campuses have very stable PA-based address
   allocations from their NRENs (or their equivalent).  However, campus
   enterprises may consider applying for IPv6 PI; some have already done
   so.  The discussions earlier in this text about PA vs. PI still
   apply.

   Finally, campuses may be more likely than many other enterprises to
   run multicast applications, such as IP TV or live lecture or seminar
   streaming, so they may wish to consider support for specific IPv6
   multicast functionality, e.g., the Embedded Rendezvous Point




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   (Embedded-RP) [RFC3956] in routers and MLDv1 and MLDv2 snooping in
   switches.

7.  Security Considerations

   This document has multiple security sections detailing with how to
   securely deploy an IPv6 network within an enterprise network.

8.  Informative References

   [CYMRU]    Team CYMRU Community Services, "THE BOGON REFERENCE",
              Version 7, April 2012,
              <http://www.team-cymru.org/Services/Bogons/>.

   [DHCPv6-SLAAC-PROBLEM]
              Liu, B. and R. Bonica, "DHCPv6/SLAAC Address Configuration
              Interaction Problem Statement", Work in Progress, draft-
              liu-bonica-dhcpv6-slaac-problem-02, September 2013.

   [DIVI]     Bao, C., Li, X., Zhai, Y., and W. Shang, "dIVI: Dual-
              Stateless IPv4/IPv6 Translation", Work in Progress, draft-
              xli-behave-divi-06, January 2014.

   [EDUROAM]  Wierenga, K., Winter, S., and T. Wolniewicz, "The eduroam
              architecture for network roaming", Work in Progress,
              draft-wierenga-ietf-eduroam-04, August 2014.

   [HOST-SCANNING]
              Gont, F. and T. Chown, "Network Reconnaissance in IPv6
              Networks", Work in Progress, draft-ietf-opsec-ipv6-host-
              scanning-04, June 2014.

   [IPv6-DC]  Lopez, D., Chen, Z., Tsou, T., Zhou, C., and A. Servin,
              "IPv6 Operational Guidelines for Datacenters", Work in
              Progress, draft-ietf-v6ops-dc-ipv6-01, February 2014.

   [IPv6-DESIGN]
              Matthews, P. and V. Kuarsingh, "Design Choices for IPv6
              Networks", Work in Progress, draft-ietf-v6ops-design-
              choices-02, September 2014.

   [IPv6-SECURITY]
              Chittimaneni, K., Kaeo, M., and E. Vyncke, "Operational
              Security Considerations for IPv6 Networks", Work in
              Progress, draft-ietf-opsec-v6-04, October 2013.






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   [RFC0826]  Plummer, D., "Ethernet Address Resolution Protocol: Or
              converting network protocol addresses to 48.bit Ethernet
              address for transmission on Ethernet hardware", STD 37,
              RFC 826, November 1982,
              <http://www.rfc-editor.org/info/rfc826>.

   [RFC1687]  Fleischman, E., "A Large Corporate User's View of IPng",
              RFC 1687, August 1994,
              <http://www.rfc-editor.org/info/rfc1687>.

   [RFC1817]  Rekhter, Y., "CIDR and Classful Routing", RFC 1817, August
              1995, <http://www.rfc-editor.org/info/rfc1817>.

   [RFC1918]  Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and
              E. Lear, "Address Allocation for Private Internets", BCP
              5, RFC 1918, February 1996,
              <http://www.rfc-editor.org/info/rfc1918>.

   [RFC2011]  McCloghrie, K., "SNMPv2 Management Information Base for
              the Internet Protocol using SMIv2", RFC 2011, November
              1996, <http://www.rfc-editor.org/info/rfc2011>.

   [RFC2096]  Baker, F., "IP Forwarding Table MIB", RFC 2096, January
              1997, <http://www.rfc-editor.org/info/rfc2096>.

   [RFC2827]  Ferguson, P. and D. Senie, "Network Ingress Filtering:
              Defeating Denial of Service Attacks which employ IP Source
              Address Spoofing", BCP 38, RFC 2827, May 2000,
              <http://www.rfc-editor.org/info/rfc2827>.

   [RFC3315]  Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C.,
              and M. Carney, "Dynamic Host Configuration Protocol for
              IPv6 (DHCPv6)", RFC 3315, July 2003,
              <http://www.rfc-editor.org/info/rfc3315>.

   [RFC3956]  Savola, P. and B. Haberman, "Embedding the Rendezvous
              Point (RP) Address in an IPv6 Multicast Address", RFC
              3956, November 2004,
              <http://www.rfc-editor.org/info/rfc3956>.

   [RFC3971]  Arkko, J., Kempf, J., Zill, B., and P. Nikander, "SEcure
              Neighbor Discovery (SEND)", RFC 3971, March 2005,
              <http://www.rfc-editor.org/info/rfc3971>.

   [RFC3972]  Aura, T., "Cryptographically Generated Addresses (CGA)",
              RFC 3972, March 2005,
              <http://www.rfc-editor.org/info/rfc3972>.




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   [RFC4038]  Shin, M-K., Hong, Y-G., Hagino, J., Savola, P., and E.
              Castro, "Application Aspects of IPv6 Transition", RFC
              4038, March 2005,
              <http://www.rfc-editor.org/info/rfc4038>.

   [RFC4057]  Bound, J., "IPv6 Enterprise Network Scenarios", RFC 4057,
              June 2005, <http://www.rfc-editor.org/info/rfc4057>.

   [RFC4193]  Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
              Addresses", RFC 4193, October 2005,
              <http://www.rfc-editor.org/info/rfc4193>.

   [RFC4213]  Nordmark, E. and R. Gilligan, "Basic Transition Mechanisms
              for IPv6 Hosts and Routers", RFC 4213, October 2005,
              <http://www.rfc-editor.org/info/rfc4213>.

   [RFC4292]  Haberman, B., "IP Forwarding Table MIB", RFC 4292, April
              2006, <http://www.rfc-editor.org/info/rfc4292>.

   [RFC4293]  Routhier, S., "Management Information Base for the
              Internet Protocol (IP)", RFC 4293, April 2006,
              <http://www.rfc-editor.org/info/rfc4293>.

   [RFC4364]  Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
              Networks (VPNs)", RFC 4364, February 2006,
              <http://www.rfc-editor.org/info/rfc4364>.

   [RFC4443]  Conta, A., Deering, S., and M. Gupta, "Internet Control
              Message Protocol (ICMPv6) for the Internet Protocol
              Version 6 (IPv6) Specification", RFC 4443, March 2006,
              <http://www.rfc-editor.org/info/rfc4443>.

   [RFC4659]  De Clercq, J., Ooms, D., Carugi, M., and F. Le Faucheur,
              "BGP-MPLS IP Virtual Private Network (VPN) Extension for
              IPv6 VPN", RFC 4659, September 2006,
              <http://www.rfc-editor.org/info/rfc4659>.

   [RFC4861]  Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
              "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
              September 2007, <http://www.rfc-editor.org/info/rfc4861>.

   [RFC4862]  Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
              Address Autoconfiguration", RFC 4862, September 2007,
              <http://www.rfc-editor.org/info/rfc4862>.

   [RFC4890]  Davies, E. and J. Mohacsi, "Recommendations for Filtering
              ICMPv6 Messages in Firewalls", RFC 4890, May 2007,
              <http://www.rfc-editor.org/info/rfc4890>.



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   [RFC4941]  Narten, T., Draves, R., and S. Krishnan, "Privacy
              Extensions for Stateless Address Autoconfiguration in
              IPv6", RFC 4941, September 2007,
              <http://www.rfc-editor.org/info/rfc4941>.

   [RFC5095]  Abley, J., Savola, P., and G. Neville-Neil, "Deprecation
              of Type 0 Routing Headers in IPv6", RFC 5095, December
              2007, <http://www.rfc-editor.org/info/rfc5095>.

   [RFC5157]  Chown, T., "IPv6 Implications for Network Scanning", RFC
              5157, March 2008,
              <http://www.rfc-editor.org/info/rfc5157>.

   [RFC5211]  Curran, J., "An Internet Transition Plan", RFC 5211, July
              2008, <http://www.rfc-editor.org/info/rfc5211>.

   [RFC5214]  Templin, F., Gleeson, T., and D. Thaler, "Intra-Site
              Automatic Tunnel Addressing Protocol (ISATAP)", RFC 5214,
              March 2008, <http://www.rfc-editor.org/info/rfc5214>.

   [RFC5375]  Van de Velde, G., Popoviciu, C., Chown, T., Bonness, O.,
              and C. Hahn, "IPv6 Unicast Address Assignment
              Considerations", RFC 5375, December 2008,
              <http://www.rfc-editor.org/info/rfc5375>.

   [RFC5722]  Krishnan, S., "Handling of Overlapping IPv6 Fragments",
              RFC 5722, December 2009,
              <http://www.rfc-editor.org/info/rfc5722>.

   [RFC5798]  Nadas, S., "Virtual Router Redundancy Protocol (VRRP)
              Version 3 for IPv4 and IPv6", RFC 5798, March 2010,
              <http://www.rfc-editor.org/info/rfc5798>.

   [RFC5952]  Kawamura, S. and M. Kawashima, "A Recommendation for IPv6
              Address Text Representation", RFC 5952, August 2010,
              <http://www.rfc-editor.org/info/rfc5952>.

   [RFC6052]  Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and X.
              Li, "IPv6 Addressing of IPv4/IPv6 Translators", RFC 6052,
              October 2010, <http://www.rfc-editor.org/info/rfc6052>.

   [RFC6104]  Chown, T. and S. Venaas, "Rogue IPv6 Router Advertisement
              Problem Statement", RFC 6104, February 2011,
              <http://www.rfc-editor.org/info/rfc6104>.

   [RFC6105]  Levy-Abegnoli, E., Van de Velde, G., Popoviciu, C., and J.
              Mohacsi, "IPv6 Router Advertisement Guard", RFC 6105,
              February 2011, <http://www.rfc-editor.org/info/rfc6105>.



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   [RFC6106]  Jeong, J., Park, S., Beloeil, L., and S. Madanapalli,
              "IPv6 Router Advertisement Options for DNS Configuration",
              RFC 6106, November 2010,
              <http://www.rfc-editor.org/info/rfc6106>.

   [RFC6144]  Baker, F., Li, X., Bao, C., and K. Yin, "Framework for
              IPv4/IPv6 Translation", RFC 6144, April 2011,
              <http://www.rfc-editor.org/info/rfc6144>.

   [RFC6145]  Li, X., Bao, C., and F. Baker, "IP/ICMP Translation
              Algorithm", RFC 6145, April 2011,
              <http://www.rfc-editor.org/info/rfc6145>.

   [RFC6146]  Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful
              NAT64: Network Address and Protocol Translation from IPv6
              Clients to IPv4 Servers", RFC 6146, April 2011,
              <http://www.rfc-editor.org/info/rfc6146>.

   [RFC6147]  Bagnulo, M., Sullivan, A., Matthews, P., and I. van
              Beijnum, "DNS64: DNS Extensions for Network Address
              Translation from IPv6 Clients to IPv4 Servers", RFC 6147,
              April 2011, <http://www.rfc-editor.org/info/rfc6147>.

   [RFC6164]  Kohno, M., Nitzan, B., Bush, R., Matsuzaki, Y., Colitti,
              L., and T. Narten, "Using 127-Bit IPv6 Prefixes on Inter-
              Router Links", RFC 6164, April 2011,
              <http://www.rfc-editor.org/info/rfc6164>.

   [RFC6177]  Narten, T., Huston, G., and L. Roberts, "IPv6 Address
              Assignment to End Sites", BCP 157, RFC 6177, March 2011,
              <http://www.rfc-editor.org/info/rfc6177>.

   [RFC6192]  Dugal, D., Pignataro, C., and R. Dunn, "Protecting the
              Router Control Plane", RFC 6192, March 2011,
              <http://www.rfc-editor.org/info/rfc6192>.

   [RFC6296]  Wasserman, M. and F. Baker, "IPv6-to-IPv6 Network Prefix
              Translation", RFC 6296, June 2011,
              <http://www.rfc-editor.org/info/rfc6296>.

   [RFC6302]  Durand, A., Gashinsky, I., Lee, D., and S. Sheppard,
              "Logging Recommendations for Internet-Facing Servers", BCP
              162, RFC 6302, June 2011,
              <http://www.rfc-editor.org/info/rfc6302>.

   [RFC6434]  Jankiewicz, E., Loughney, J., and T. Narten, "IPv6 Node
              Requirements", RFC 6434, December 2011,
              <http://www.rfc-editor.org/info/rfc6434>.



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   [RFC6555]  Wing, D. and A. Yourtchenko, "Happy Eyeballs: Success with
              Dual-Stack Hosts", RFC 6555, April 2012,
              <http://www.rfc-editor.org/info/rfc6555>.

   [RFC6583]  Gashinsky, I., Jaeggli, J., and W. Kumari, "Operational
              Neighbor Discovery Problems", RFC 6583, March 2012,
              <http://www.rfc-editor.org/info/rfc6583>.

   [RFC6724]  Thaler, D., Draves, R., Matsumoto, A., and T. Chown,
              "Default Address Selection for Internet Protocol Version 6
              (IPv6)", RFC 6724, September 2012,
              <http://www.rfc-editor.org/info/rfc6724>.

   [RFC6866]  Carpenter, B. and S. Jiang, "Problem Statement for
              Renumbering IPv6 Hosts with Static Addresses in Enterprise
              Networks", RFC 6866, February 2013,
              <http://www.rfc-editor.org/info/rfc6866>.

   [RFC6879]  Jiang, S., Liu, B., and B. Carpenter, "IPv6 Enterprise
              Network Renumbering Scenarios, Considerations, and
              Methods", RFC 6879, February 2013,
              <http://www.rfc-editor.org/info/rfc6879>.

   [RFC6883]  Carpenter, B. and S. Jiang, "IPv6 Guidance for Internet
              Content Providers and Application Service Providers", RFC
              6883, March 2013,
              <http://www.rfc-editor.org/info/rfc6883>.

   [RFC6959]  McPherson, D., Baker, F., and J. Halpern, "Source Address
              Validation Improvement (SAVI) Threat Scope", RFC 6959, May
              2013, <http://www.rfc-editor.org/info/rfc6959>.

   [RFC6964]  Templin, F., "Operational Guidance for IPv6 Deployment in
              IPv4 Sites Using the Intra-Site Automatic Tunnel
              Addressing Protocol (ISATAP)", RFC 6964, May 2013,
              <http://www.rfc-editor.org/rfc/rfc6964.txt>.

   [RFC7011]  Claise, B., Trammell, B., and P. Aitken, "Specification of
              the IP Flow Information Export (IPFIX) Protocol for the
              Exchange of Flow Information", STD 77, RFC 7011, September
              2013, <http://www.rfc-editor.org/info/rfc7011>.

   [RFC7012]  Claise, B. and B. Trammell, "Information Model for IP Flow
              Information Export (IPFIX)", RFC 7012, September 2013,
              <http://www.rfc-editor.org/info/rfc7012>.






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   [RFC7045]  Carpenter, B. and S. Jiang, "Transmission and Processing
              of IPv6 Extension Headers", RFC 7045, December 2013,
              <http://www.rfc-editor.org/info/rfc7045>.

   [RFC7113]  Gont, F., "Implementation Advice for IPv6 Router
              Advertisement Guard (RA-Guard)", RFC 7113, February 2014,
              <http://www.rfc-editor.org/info/rfc7113>.

   [RFC7123]  Gont, F. and W. Liu, "Security Implications of IPv6 on
              IPv4 Networks", RFC 7123, February 2014,
              <http://www.rfc-editor.org/info/rfc7123>.

   [RFC7359]  Gont, F., "Layer 3 Virtual Private Network (VPN) Tunnel
              Traffic Leakages in Dual-Stack Hosts/Networks", RFC 7359,
              August 2014, <http://www.rfc-editor.org/info/rfc7359>.

   [SMURF]    The Cert Division of the Software Engineering Institute,
              "Smurf IP Denial-of-Service Attacks", CERT Advisory CA-
              1998-01, March 2000,
              <http://www.cert.org/advisories/CA-1998-01.html>.

   [ULA-USAGE]
              Liu, B. and S. Jiang, "Considerations of Using Unique
              Local Addresses", Work in Progress, draft-ietf-v6ops-ula-
              usage-recommendations-03, July 2014.

Acknowledgements

   The authors would like to thank Robert Sparks, Steve Hanna, Tom
   Taylor, Brian Haberman, Stephen Farrell, Chris Grundemann, Ray
   Hunter, Kathleen Moriarty, Benoit Claise, Brian Carpenter, Tina Tsou,
   Christian Jacquenet, and Fred Templin for their substantial comments
   and contributions.


















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Authors' Addresses

   Kiran K. Chittimaneni
   Dropbox, Inc.
   185 Berry Street, Suite 400
   San Francisco, CA  94107
   United States
   EMail: kk@dropbox.com

   Tim Chown
   University of Southampton
   Highfield
   Southampton, Hampshire  SO17 1BJ
   United Kingdom
   EMail: tjc@ecs.soton.ac.uk

   Lee Howard
   Time Warner Cable
   13820 Sunrise Valley Drive
   Herndon, VA  20171
   United States
   Phone: +1 703 345 3513
   EMail: lee.howard@twcable.com

   Victor Kuarsingh
   Dyn, Inc.
   150 Dow Street
   Manchester, NH
   United States
   EMail: victor@jvknet.com

   Yanick Pouffary
   Hewlett Packard
   950 Route Des Colles
   Sophia-Antipolis  06901
   France
   EMail: Yanick.Pouffary@hp.com

   Eric Vyncke
   Cisco Systems
   De Kleetlaan 6a
   Diegem  1831
   Belgium
   Phone: +32 2 778 4677
   EMail: evyncke@cisco.com






Chittimaneni, et al.          Informational                    [Page 35]
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