OPSEC                                                    K. Chittimaneni
Internet-Draft                                              Dropbox Inc.
Intended status: Informational                                   M. Kaeo
Expires: March 12, 2016                             Double Shot Security
                                                               E. Vyncke
                                                       September 9, 2015

         Operational Security Considerations for IPv6 Networks


   Knowledge and experience on how to operate IPv4 securely is
   available: whether it is the Internet or an enterprise internal
   network.  However, IPv6 presents some new security challenges.  RFC
   4942 describes the security issues in the protocol but network
   managers also need a more practical, operations-minded document to
   enumerate advantages and/or disadvantages of certain choices.

   This document analyzes the operational security issues in all places
   of a network (enterprises, service providers and residential users)
   and proposes technical and procedural mitigations techniques.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on March 12, 2016.

Copyright Notice

   Copyright (c) 2015 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   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.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  Generic Security Considerations . . . . . . . . . . . . . . .   4
     2.1.  Addressing Architecture . . . . . . . . . . . . . . . . .   4
       2.1.1.  Statically Configured Addresses . . . . . . . . . . .   4
       2.1.2.  Use of ULAs . . . . . . . . . . . . . . . . . . . . .   5
       2.1.3.  Point-to-Point Links  . . . . . . . . . . . . . . . .   5
       2.1.4.  Temporary Addresses - Privacy Extensions for SLAAC  .   6
       2.1.5.  Privacy consideration of Addresses  . . . . . . . . .   7
       2.1.6.  DHCP/DNS Considerations . . . . . . . . . . . . . . .   7
     2.2.  Extension Headers . . . . . . . . . . . . . . . . . . . .   7
     2.3.  Link-Layer Security . . . . . . . . . . . . . . . . . . .   7
       2.3.1.  SeND and CGA  . . . . . . . . . . . . . . . . . . . .   8
       2.3.2.  Securing DHCP . . . . . . . . . . . . . . . . . . . .   8
       2.3.3.  ND/RA Rate Limiting . . . . . . . . . . . . . . . . .   9
       2.3.4.  ND/RA Filtering . . . . . . . . . . . . . . . . . . .  10
       2.3.5.  3GPP Link-Layer Security  . . . . . . . . . . . . . .  11
     2.4.  Control Plane Security  . . . . . . . . . . . . . . . . .  11
       2.4.1.  Control Protocols . . . . . . . . . . . . . . . . . .  12
       2.4.2.  Management Protocols  . . . . . . . . . . . . . . . .  13
       2.4.3.  Packet Exceptions . . . . . . . . . . . . . . . . . .  13
     2.5.  Routing Security  . . . . . . . . . . . . . . . . . . . .  14
       2.5.1.  Authenticating Neighbors/Peers  . . . . . . . . . . .  14
       2.5.2.  Securing Routing Updates Between Peers  . . . . . . .  15
       2.5.3.  Route Filtering . . . . . . . . . . . . . . . . . . .  15
     2.6.  Logging/Monitoring  . . . . . . . . . . . . . . . . . . .  16
       2.6.1.  Data Sources  . . . . . . . . . . . . . . . . . . . .  17
       2.6.2.  Use of Collected Data . . . . . . . . . . . . . . . .  20
       2.6.3.  Summary . . . . . . . . . . . . . . . . . . . . . . .  22
     2.7.  Transition/Coexistence Technologies . . . . . . . . . . .  23
       2.7.1.  Dual Stack  . . . . . . . . . . . . . . . . . . . . .  23
       2.7.2.  Transition Mechanisms . . . . . . . . . . . . . . . .  23
       2.7.3.  Translation Mechanisms  . . . . . . . . . . . . . . .  27
     2.8.  General Device Hardening  . . . . . . . . . . . . . . . .  28
   3.  Enterprises Specific Security Considerations  . . . . . . . .  29
     3.1.  External Security Considerations: . . . . . . . . . . . .  29

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     3.2.  Internal Security Considerations: . . . . . . . . . . . .  30
   4.  Service Providers Security Considerations . . . . . . . . . .  30
     4.1.  BGP . . . . . . . . . . . . . . . . . . . . . . . . . . .  30
       4.1.1.  Remote Triggered Black Hole Filtering . . . . . . . .  30
     4.2.  Transition Mechanism  . . . . . . . . . . . . . . . . . .  31
     4.3.  Lawful Intercept  . . . . . . . . . . . . . . . . . . . .  31
   5.  Residential Users Security Considerations . . . . . . . . . .  31
   6.  Further Reading . . . . . . . . . . . . . . . . . . . . . . .  32
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  32
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  32
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .  33
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  33
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  33
     10.2.  Informative References . . . . . . . . . . . . . . . . .  33
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  43

1.  Introduction

   Running an IPv6 network is new for most operators not only because
   they are not yet used to large scale IPv6 networks but also because
   there are subtle differences between IPv4 and IPv6 especially with
   respect to security.  For example, all layer-2 interactions are now
   done by Neighbor Discovery Protocol [RFC4861] rather than by Address
   Resolution Protocol [RFC0826].  Also, there are subtle differences
   between NAT44 and NPTv6 [RFC6296] which are explicitly pointed out in
   the latter's security considerations section.

   IPv6 networks are deployed using a variety of techniques, each of
   which have their own specific security concerns.

   This document complements [RFC4942] by listing all security issues
   when operating a network utilizing varying transition technologies
   and updating with ones that have been standardized since 2007.  It
   also provides more recent operational deployment experiences where

1.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in [RFC2119] when they
   appear in ALL CAPS.  These words may also appear in this document in
   lower case as plain English words, absent their normative meanings.

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2.  Generic Security Considerations

2.1.  Addressing Architecture

   IPv6 address allocations and overall architecture are an important
   part of securing IPv6.  Typically what you initially design for will
   be what you use for a very long time.  Although initially IPv6 was
   thought to make renumbering easy, in practice, it would be extremely
   difficult to renumber.

   Once an address allocation has been assigned, there should be some
   thought given to an overall address allocation plan.  With the
   abundance of address space available, an address allocation may be
   structured around services along with geographic locations, which
   then can be a basis for more structured security policies to permit
   or deny services between geographic regions.

   A common question is whether companies should use PI vs PA space
   [RFC7381] but from a security perspective there is little difference.
   However, one aspect to keep in mind is who has ownership of the
   address space and who is responsible if/when Law Enforcement may need
   to enforce restrictions on routability of the space due to malicious
   criminal activity.

2.1.1.  Statically Configured Addresses

   When considering how to assign statically configured addresses it is
   necessary to take into consideration the effectiveness of perimeter
   security in a given environment.  There is a trade-off between ease
   of operational deployment where some portions of the IPv6 address
   could be easily recognizable for operational debugging and
   troubleshooting versus the risk of scanning; [SCANNING] shows that
   there are scientifically based mechanisms that make scanning for IPv6
   reachable nodes more realizable than expected.  The use of common
   multicast groups which are defined for important networked devices
   and the use of commonly repeated addresses could make it easy to
   figure out which devices are name servers, routers or other critical

   While in some environments the perimeter security is so poor that
   obfuscating addresses is considered a benefit; it is a better
   practice to ensure that perimeter rules are actively checked and
   enforced and that statically configured addresses follow some logical
   allocation scheme for ease of operation.

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2.1.2.  Use of ULAs

   ULAs are intended for scenarios where IP addresses will not have
   global scope.  The implicit expectation from the RFC is that all ULAs
   will be randomly created as /48s.  Any use of ULAs that are not
   created as a /48 violates [RFC4193].

   ULAs could be useful for infrastructure hiding as described in
   [RFC4864]; Alternatively Link-Local addresses [RFC7404] could also be
   used.  Although ULAs are supposed to be used in conjunction with
   global addresses for hosts that desire external connectivity, a few
   operators chose to use ULAs in conjunction with some sort of address
   translation at the border in order to maintain a perception of parity
   between their IPv4 and IPv6 setup.  Some operators believe that
   stateful IPv6 Network Address and Port Translation (NAPT) provides
   some security not provided by NPTv6 (the authors of this document do
   not share this point of view).  The latter would be problematic in
   trying to track specific machines that may source malware although
   this is less of an issue if appropriate logging is done which
   includes utilizing accurate timestamps and logging a node's source
   ports [RFC6302].

   The use of ULA does not isolate 'by magic' the part of the network
   using ULA from other parts of the network (including the Internet).
   Although section 4.1 of [RFC4193] explicitly states "If BGP is being
   used at the site border with an ISP, the default BGP configuration
   must filter out any Local IPv6 address prefixes, both incoming and
   outgoing.", the operational reality is that this guideline is not
   always followed.  As written, RFC4193 makes no changes to default
   routing behavior of exterior protocols.  Therefore, routers will
   happily forward packets whose source or destination address is ULA as
   long as they have a route to the destination and there is no ACL
   blocking those packets.  This means that using ULA does not prevent
   route and packet filters to be implemented and monitored.  This also
   means that all Internet transit networks should consider ULA as
   source or destination as bogons packets and drop them.

   It is important to carefully weigh the benefits of using ULAs versus
   utilizing a section of the global allocation and creating a more
   effective filtering strategy.  A typical argument is that there are
   too many mistakes made with filters and ULAs make things easier to
   hide machines.

2.1.3.  Point-to-Point Links

   [RFC6164] recommends the use of /127 for inter-router point-to-point
   links.  A /127 prevents the ping-pong attack between routers.
   However, it should be noted that at the time of this writing, there

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   are still many networks out there that follow the advice provided by
   [RFC3627] (obsoleted and marked Historic by [RFC6547]) and therefore
   continue to use /64's and/or /112's.  We recommend that the guidance
   provided by RFC6164 be followed.

   Some environments are also using link-local addressing for point-to-
   point links.  While this practice could further reduce the attack
   surface against infrastructure devices, the operational disadvantages
   need also to be carefully considered [RFC7404].

2.1.4.  Temporary Addresses - Privacy Extensions for SLAAC

   Normal stateless address autoconfiguration (SLAAC) relies on the
   automatically generated EUI-64 address, which together with the /64
   prefix makes up the global unique IPv6 address.  The EUI-64 address
   is generated from the MAC address.  Randomly generating an interface
   ID, as described in [RFC4941], is part of SLAAC with so-called
   privacy extension addresses and used to address some privacy
   concerns.  Privacy extension addresses a.k.a. temporary addresses may
   help to mitigate the correlation of activities of a node within the
   same network, and may also reduce the attack exposure window.

   As privacy extension addresses could also be used to obfuscate some
   malevolent activities (whether on purpose or not), it is advised in
   scenarios where user attribution is important to disable SLAAC and
   rely only on DHCPv6.  However, in scenarios where anonymity is a
   strong desire since protecting user privacy is more important than
   user attribution, privacy extension addresses should be used

   Using privacy extension addresses prevents the operator from building
   a priori host specific access control lists (ACLs).  It must be noted
   that recent versions of Windows do not use the MAC address anymore to
   build the stable address but use a mechanism similar to the one
   described in [RFC7217], this also means that such an ACL cannot be
   configured based solely on the MAC address of the nodes, diminishing
   the value of such ACL.  On the other hand, different VLANs are often
   used to segregate users, then ACL can rely on a /64 prefix per VLAN
   rather than a per host ACL entry.

   The decision to utilize privacy extension addresses can come down to
   whether the network is managed versus unmanaged.  In some
   environments full visibility into the network is required at all
   times which requires that all traffic be attributable to where it is
   sourced or where it is destined to within a specific network.  This
   situation is dependent on what level of logging is performed.  If
   logging considerations include utilizing accurate timestamps and
   logging a node's source ports [RFC6302] then there should always

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   exist appropriate user attribution needed to get to the source of any
   malware originator or source of criminal activity.

   Disabling SLAAC and privacy extensions addresses can be done by
   sending Router Advertisement with a hint to use DHCPv6 by setting the
   M-bit but also disabling SLAAC by resetting all A-bits in all prefixe
   information options sent in the Router Advertisement message.

2.1.5.  Privacy consideration of Addresses

   However, there are several privacy issues still present with
   [RFC4941] such as host tracking, and address scanning attacks are
   still possible.  More details are provided in Appendix A.  of
   [RFC7217] and in [I-D.ietf-6man-ipv6-address-generation-privacy].

2.1.6.  DHCP/DNS Considerations

   Many environments use DHCPv6 to allocate addresses to ensure
   audibility and traceability (but see Section  A main
   security concern is the ability to detect and mitigate against rogue
   DHCP servers (Section 2.3.2).

   DNS is often used for malware activities and while there are no
   fundamental differences with IPv4 and IPv6 security concerns, there
   are specific consideration in DNS64 [RFC6147] environments that need
   to be understood.  Specifically the interactions and potential to
   interference with DNSsec implementation need to be understood - these
   are pointed out in detail in Section

2.2.  Extension Headers

   TBD, a short section referring to all Fernando's I-D & RFC.

2.3.  Link-Layer Security

   IPv6 relies heavily on the Neighbor Discovery protocol (NDP)
   [RFC4861] to perform a variety of link operations such as discovering
   other nodes on the link, resolving their link-layer addresses, and
   finding routers on the link.  If not secured, NDP is vulnerable to
   various attacks such as router/neighbor message spoofing, redirect
   attacks, Duplicate Address Detection (DAD) DoS attacks, etc. many of
   these security threats to NDP have been documented in IPv6 ND Trust
   Models and Threats [RFC3756] and in [RFC6583].

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2.3.1.  SeND and CGA

   SEcure Neighbor Discovery (SeND), as described in [RFC3971], is a
   mechanism that was designed to secure ND messages.  This approach
   involves the use of new NDP options to carry public key based
   signatures.  Cryptographically Generated Addresses (CGA), as
   described in [RFC3972], are used to ensure that the sender of a
   Neighbor Discovery message is the actual "owner" of the claimed IPv6
   address.  A new NDP option, the CGA option, was introduced and is
   used to carry the public key and associated parameters.  Another NDP
   option, the RSA Signature option, is used to protect all messages
   relating to neighbor and Router discovery.

   SeND protects against:

   o  Neighbor Solicitation/Advertisement Spoofing

   o  Neighbor Unreachability Detection Failure

   o  Duplicate Address Detection DoS Attack

   o  Router Solicitation and Advertisement Attacks

   o  Replay Attacks

   o  Neighbor Discovery DoS Attacks

   SeND does NOT:

   o  Protect statically configured addresses

   o  Protect addresses configured using fixed identifiers (i.e.  EUI-

   o  Provide confidentiality for NDP communications

   o  Compensate for an unsecured link - SEND does not require that the
      addresses on the link and Neighbor Advertisements correspond

   However, at this time and after many years after their
   specifications, CGA and SeND do not have wide support from generic
   operating systems; hence, their usefulness is limited.

2.3.2.  Securing DHCP

   Dynamic Host Configuration Protocol for IPv6 (DHCPv6), as detailed in
   [RFC3315], enables DHCP servers to pass configuration parameters such
   as IPv6 network addresses and other configuration information to IPv6

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   nodes.  DHCP plays an important role in any large network by
   providing robust stateful autoconfiguration and autoregistration of
   DNS Host Names.

   The two most common threats to DHCP clients come from malicious
   (a.k.a. rogue) or unintentionally misconfigured DHCP servers.  A
   malicious DHCP server is established with the intent of providing
   incorrect configuration information to the client to cause a denial
   of service attack or mount a man in the middle attack.  While
   unintentionall, a misconfigured DHCP server can have the same impact.
   Additional threats against DHCP are discussed in the security
   considerations section of [RFC3315]DHCP-shield

   [RFC7610] specifies a mechanism for protecting hosts connected
   against rogue DHCPv6 servers.  This mechanism is based on DHCPv6
   packet-filtering at the layer-2 device; the administrator specifies
   the interfaces connected to DHCPv6 servers.

   It is recommended to use DHCP-shield.

2.3.3.  ND/RA Rate Limiting

   Neighbor Discovery (ND) can be vulnerable to denial of service (DoS)
   attacks in which a router is forced to perform address resolution for
   a large number of unassigned addresses.  Possible side effects of
   this attack preclude new devices from joining the network or even
   worse rendering the last hop router ineffective due to high CPU
   usage.  Easy mitigative steps include rate limiting Neighbor
   Solicitations, restricting the amount of state reserved for
   unresolved solicitations, and clever cache/timer management.

   [RFC6583] discusses the potential for DOS in detail and suggests
   implementation improvements and operational mitigation techniques
   that may be used to mitigate or alleviate the impact of such attacks.
   Here are some feasible mitigation options that can be employed by
   network operators today:

   o  Ingress filtering of unused addresses by ACL, route filtering,
      longer than /64 prefix; These require static configuration of the

   o  Tuning of NDP process (where supported).

   Additionally, IPv6 ND uses multicast extensively for signaling
   messages on the local link to avoid broadcast messages for on-the-
   wire efficiency.  However, this has some side effects on wifi
   networks, especially a negative impact on battery life of smartphones
   and other battery operated devices that are connected to such

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   networks.  The following drafts are actively discussing methods to
   rate limit RAs and other ND messages on wifi networks in order to
   address this issue:

   o  [I-D.thubert-savi-ra-throttler]

   o  [I-D.chakrabarti-nordmark-6man-efficient-nd]

2.3.4.  ND/RA Filtering

   Router Advertisement spoofing is a well-known attack vector and has
   been extensively documented.  The presence of rogue RAs, either
   intentional or malicious, can cause partial or complete failure of
   operation of hosts on an IPv6 link.  For example, a host can select
   an incorrect router address which can be used as a man-in-the-middle
   (MITM) attack or can assume wrong prefixes to be used for stateless
   address configuration (SLAAC).  [RFC6104] summarizes the scenarios in
   which rogue RAs may be observed and presents a list of possible
   solutions to the problem.  [RFC6105] (RA-Guard) describes a solution
   framework for the rogue RA problem where network segments are
   designed around switching devices that are capable of identifying
   invalid RAs and blocking them before the attack packets actually
   reach the target nodes.

   However, several evasion techniques that circumvent the protection
   provided by RA-Guard have surfaced.  A key challenge to this
   mitigation technique is introduced by IPv6 fragmentation.  An
   attacker can conceal the attack by fragmenting his packets into
   multiple fragments such that the switching device that is responsible
   for blocking invalid RAs cannot find all the necessary information to
   perform packet filtering in the same packet.  [RFC7113] describes
   such evasion techniques, and provides advice to RA-Guard implementers
   such that the aforementioned evasion vectors can be eliminated.

   Given that the IPv6 Fragmentation Header can be leveraged to
   circumvent current implementations of RA-Guard, [RFC6980] aims to
   update [RFC4861] such that use of the IPv6 Fragmentation Header is
   forbidden in all Neighbor Discovery messages except "Certification
   Path Advertisement", thus allowing for simple and effective measures
   to counter Neighbor Discovery attacks.

   The Source Address Validation Improvements (SAVI) working group has
   worked on other ways to mitigate the effects of such attacks.
   [RFC7513] would help in creating bindings between a DHCPv4 [RFC2131]
   /DHCPv6 [RFC3315] assigned source IP address and a binding anchor
   [RFC7039] on a SAVI device.  Also, [RFC6620] describes how to glean
   similar bindings when DHCP is not used.  The bindings can be used to

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   filter packets generated on the local link with forged source IP

   It is still recommended that RA-Guard be be employed as a first line
   of defense against common attack vectors including misconfigured

2.3.5.  3GPP Link-Layer Security

   The 3GPP link is a point-to-point like link that has no link-layer
   address.  This implies there can only be an end host (the mobile
   hand-set) and the first-hop router (i.e., a GPRS Gatewat Support Node
   (GGSN) or a Packet Gateway (PGW)) on that link.  The GGSN/PGW never
   configures a non link-local address on the link using the advertised
   /64 prefix on it.  The advertised prefix must not be used for on-link
   determination.  There is no need for an address resolution on the
   3GPP link, since there are no link-layer addresses.  Furthermore, the
   GGSN/PGW assigns a prefix that is unique within each 3GPP link that
   uses IPv6 stateless address autoconfiguration.  This avoids the
   necessity to perform DAD at the network level for every address built
   by the mobile host.  The GGSN/PGW always provides an IID to the
   cellular host for the purpose of configuring the link-local address
   and ensures the uniqueness of the IID on the link (i.e., no
   collisions between its own link-local address and the mobile host's

   The 3GPP link model itself mitigates most of the known NDP-related
   Denial-of-Service attacks.  In practice, the GGSN/PGW only needs to
   route all traffic to the mobile host that falls under the prefix
   assigned to it.  As there is also a single host on the 3GPP link,
   there is no need to defend that IPv6 address.

   See Section 5 of [RFC6459] for a more detailed discussion on the 3GPP
   link model, NDP on it and the address configuration detail.

2.4.  Control Plane Security

   [RFC6192] defines the router control plane and this definition is
   repeated here for the reader's convenience.

   Modern router architecture design maintains a strict separation of
   forwarding and router control plane hardware and software.  The
   router control plane supports routing and management functions.  It
   is generally described as the router architecture hardware and
   software components for handling packets destined to the device
   itself as well as building and sending packets originated locally on
   the device.  The forwarding plane is typically described as the
   router architecture hardware and software components responsible for

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   receiving a packet on an incoming interface, performing a lookup to
   identify the packet's IP next hop and determine the best outgoing
   interface towards the destination, and forwarding the packet out
   through the appropriate outgoing interface.

   While the forwarding plane is usually implemented in high-speed
   hardware, the control plane is implemented by a generic processor
   (named router processor RP) and cannot process packets at a high
   rate.  Hence, this processor can be attacked by flooding its input
   queue with more packets than it can process.  The control plane
   processor is then unable to process valid control packets and the
   router can lose OSPF or BGP adjacencies which can cause a severe
   network disruption.

   The mitigation technique is:

   o  To drop non-legit control packet before they are queued to the RP
      (this can be done by a forwarding plane ACL) and

   o  To rate limit the remaining packets to a rate that the RP can
      sustain.  Protocol specific protection should also be done (for
      example, a spoofed OSPFv3 packet could trigger the execution of
      the Dijkstra algorithm, therefore the number of Dijsktra execution
      should be also rate limited).

   This section will consider several classes of control packets:

   o  Control protocols: routing protocols: such as OSPFv3, BGP and by
      extension Neighbor Discovery and ICMP

   o  Management protocols: SSH, SNMP, IPfix, etc

   o  Packet exceptions: which are normal data packets which requires a
      specific processing such as generating a packet-too-big ICMP
      message or having the hop-by-hop extension header.

2.4.1.  Control Protocols

   This class includes OSPFv3, BGP, NDP, ICMP.

   An ingress ACL to be applied on all the router interfaces SHOULD be
   configured such as:

   o  drop OSPFv3 (identified by Next-Header being 89) and RIPng
      (identified by UDP port 521) packets from a non link-local address

   o  allow BGP (identified by TCP port 179) packets from all BGP
      neighbors and drop the others

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   o  allow all ICMP packets (transit and to the router interfaces)

   Note: dropping OSPFv3 packets which are authenticated by IPsec could
   be impossible on some routers whose ACL are unable to parse the IPsec
   ESP or AH extension headers.

   Rate limiting of the valid packets SHOULD be done.  The exact
   configuration obviously depends on the power of the Route Processor.

2.4.2.  Management Protocols

   This class includes: SSH, SNMP, syslog, NTP, etc

   An ingress ACL to be applied on all the router interfaces SHOULD be
   configured such as:

   o  Drop packets destined to the routers except those belonging to
      protocols which are used (for example, permit TCP 22 and drop all
      when only SSH is used);

   o  Drop packets where the source does not match the security policy,
      for example if SSH connections should only be originated from the
      NOC, then the ACL should permit TCP port 22 packets only from the
      NOC prefix.

   Rate limiting of the valid packets SHOULD be done.  The exact
   configuration obviously depends on the power of the Route Processor.

2.4.3.  Packet Exceptions

   This class covers multiple cases where a data plane packet is punted
   to the route processor because it requires specific processing:

   o  generation of an ICMP packet-too-big message when a data plane
      packet cannot be forwarded because it is too large;

   o  generation of an ICMP hop-limit-expired message when a data plane
      packet cannot be forwarded because its hop-limit field has reached

   o  generation of an ICMP destination-unreachable message when a data
      plane packet cannot be forwarded for any reason;

   o  processing of the hop-by-hop extension header;

   o  or more specific to some router implementation: an oversized
      extension header chain which cannot be processed by the hardware
      and force the packet to be punted to the generic router CPU.

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   On some routers, not everything can be done by the specialized data
   plane hardware which requires some packets to be 'punted' to the
   generic RP.  This could include for example the processing of a long
   extension header chain in order to apply an ACL based on layer 4
   information.  [RFC6980] and more generally [RFC7112] highlight the
   security implications of oversized header chains on routers and aims
   to update RFC2460 such that the first fragment of a packet is
   required to contain the entire IPv6 header chain.

   An ingress ACL cannot help to mitigate a control plane attack using
   those packet exceptions.  The only protection for the RP is to limit
   the rate of those packet exceptions forwarded to the RP, this means
   that some data plane packets will be dropped without any ICMP
   messages back to the source which will cause Path MTU holes.  But,
   there is no other solution.

   In addition to limiting the rate of data plane packets queued to the
   RP, it is also important to limit the generation rate of ICMP
   messages both the save the RP but also to prevent an amplification
   attack using the router as a reflector.

2.5.  Routing Security

   Routing security in general can be broadly divided into three

   1.  Authenticating neighbors/peers

   2.  Securing routing updates between peers

   3.  Route filtering

   [RFC7454] covers these sections specifically for BGP in detail.

2.5.1.  Authenticating Neighbors/Peers

   A basic element of routing is the process of forming adjacencies,
   neighbor, or peering relationships with other routers.  From a
   security perspective, it is very important to establish such
   relationships only with routers and/or administrative domains that
   one trusts.  A traditional approach has been to use MD5 HMAC, which
   allows routers to authenticate each other prior to establishing a
   routing relationship.

   OSPFv3 can rely on IPsec to fulfill the authentication function.
   However, it should be noted that IPsec support is not standard on all
   routing platforms.  In some cases, this requires specialized hardware
   that offloads crypto over to dedicated ASICs or enhanced software

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   images (both of which often come with added financial cost) to
   provide such functionality.  An added detail is to determine whether
   OSPFv3 IPsec implementations use AH or ESP-Null for integrity
   protection.  In early implementations all OSPFv3 IPsec configurations
   relied on AH since the details weren't specified in [RFC5340] or
   [RFC2740] that was obsoleted by the former.  However, the document
   which specifically describes how IPsec should be implemented for
   OSPFv3 [RFC4552] specifically states that ESP-Null MUST and AH MAY be
   implemented since it follows the overall IPsec standards wordings.
   OSPFv3 can also use normal ESP to encrypt the OSPFv3 payload to hide
   the routing information.

   [RFC7166] (which obsoletes [RFC6506] changes OSPFv3's reliance on
   IPsec by appending an authentication trailer to the end of the OSPFv3
   packets.  This document does not specifically provide for a mechanism
   that will authenticate the specific originator of a packet.  Rather,
   it will allow a router to confirm that the packet has indeed been
   issued by a router that had access to the shared authentication key.

   With all authentication mechanisms, operators should confirm that
   implementations can support re-keying mechanisms that do not cause
   outages.  There have been instances where any re-keying cause outages
   and therefore the tradeoff between utilizing this functionality needs
   to be weighed against the protection it provides.

2.5.2.  Securing Routing Updates Between Peers

   IPv6 initially mandated the provisioning of IPsec capability in all
   nodes.  However, in the updated IPv6 Nodes Requirement standard
   [RFC6434] is now a SHOULD and not MUST implement.  Theoretically it
   is possible, and recommended, that communication between two IPv6
   nodes, including routers exchanging routing information be encrypted
   using IPsec.  In practice however, deploying IPsec is not always
   feasible given hardware and software limitations of various platforms
   deployed, as described in the earlier section.  Additionally, in a
   protocol such as OSPFv3 where adjacencies are formed on a one-to-many
   basis, IPsec key management becomes difficult to maintain and is not
   often utilized.

2.5.3.  Route Filtering

   Route filtering policies will be different depending on whether they
   pertain to edge route filtering vs internal route filtering.  At a
   minimum, IPv6 routing policy as it pertains to routing between
   different administrative domains should aim to maintain parity with
   IPv4 from a policy perspective e.g.,

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   o  Filter internal-use, non-globally routable IPv6 addresses at the

   o  Discard packets from and to bogon and reserved space

   o  Configure ingress route filters that validate route origin, prefix
      ownership, etc. through the use of various routing databases,
      e.g., RADB.  There is additional work being done in this area to
      formally validate the origin ASs of BGP announcements in [RFC6810]

   Some good recommendations for filtering can be found from Team CYMRU
   at [CYMRU].

2.6.  Logging/Monitoring

   In order to perform forensic research in case of any security
   incident or to detect abnormal behaviors, network operator should log
   multiple pieces of information.

   This includes:

   o  logs of all applications when available (for example web servers);

   o  use of IP Flow Information Export [RFC7011] also known as IPfix;

   o  use of SNMP MIB [RFC4293];

   o  use of the Neighbor cache;

   o  use of stateful DHCPv6 [RFC3315] lease cache, especially when a
      relay agent [RFC6221] in layer-2 switches is used;

   o  use of RADIUS [RFC2866] for accounting records.

   Please note that there are privacy issues related to how those logs
   are collected, kept and safely discarded.  Operators are urged to
   check their country legislation.

   All those pieces of information will be used for:

   o  forensic (Section research to answer questions such as
      who did what and when?

   o  correlation (Section which IP addresses were used by a
      specific node (assuming the use of privacy extensions addresses

   o  inventory (Section which IPv6 nodes are on my network?

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   o  abnormal behavior detection (Section unusual traffic
      patterns are often the symptoms of a abnormal behavior which is in
      turn a potential attack (denial of services, network scan, a node
      being part of a botnet, ...)

2.6.1.  Data Sources

   This section lists the most important sources of data that are useful
   for operational security.  Logs of Applications

   Those logs are usually text files where the remote IPv6 address is
   stored in all characters (not binary).  This can complicate the
   processing since one IPv6 address, 2001:db8::1 can be written in
   multiple ways such as:

   o  2001:DB8::1 (in uppercase)

   o  2001:0db8::0001 (with leading 0)

   o  and many other ways.

   RFC 5952 [RFC5952] explains this problem in detail and recommends the
   use of a single canonical format (in short use lower case and
   suppress leading 0).  This memo recommends the use of canonical
   format [RFC5952] for IPv6 addresses in all possible cases.  If the
   existing application cannot log under the canonical format, then this
   memo recommends the use an external program in order to canonicalize
   all IPv6 addresses.

   For example, this perl script can be used:

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   #!/usr/bin/perl ?w
   use strict ;
   use warnings ;
   use Socket ;
   use Socket6 ;

   my (@words, $word, $binary_address) ;

   ## go through the file one line at a time
   while (my $line = <STDIN>) {
     chomp $line;
     foreach my $word (split /[ \n]/, $line) {
       $binary_address = inet_pton AF_INET6, $word ;
       if ($binary_address) {
         print inet_ntop AF_INET6, $binary_address ;
       } else {
         print $word ;
       print " " ;
     print "\n" ;
   }  IP Flow Information Export by IPv6 Routers

   IPfix [RFC7012] defines some data elements that are useful for

   o  in section 5.4 (IP Header fields): nextHeaderIPv6 and

   o  in section 5.6 (Sub-IP fields) sourceMacAddress.

   Moreover, IPfix is very efficient in terms of data handling and
   transport.  It can also aggregate flows by a key such as
   sourceMacAddress in order to have aggregated data associated with a
   specific sourceMacAddress.  This memo recommends the use of IPfix and
   aggregation on nextHeaderIPv6, sourceIPv6Address and
   sourceMacAddress.  SNMP MIB by IPv6 Routers

   RFC 4293 [RFC4293] defines a Management Information Base (MIB) for
   the two address families of IP.  This memo recommends the use of:

   o  ipIfStatsTable table which collects traffic counters per

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   o  ipNetToPhysicalTable table which is the content of the Neighbor
      cache, i.e. the mapping between IPv6 and data-link layer
      addresses.  Neighbor Cache of IPv6 Routers

   The neighbor cache of routers contains all mappings between IPv6
   addresses and data-link layer addresses.  It is usually available by
   two means:

   o  the SNMP MIB (Section as explained above;

   o  also by connecting over a secure management channel (such as SSH
      or HTTPS) and explicitely requesting a neighbor cache dump.

   The neighbor cache is highly dynamic as mappings are added when a new
   IPv6 address appears on the network (could be quite often with
   privacy extension addresses [RFC4941] or when they are removed when
   the state goes from UNREACH to removed (the default time for a
   removal per Neighbor Unreachability Detection [RFC4861] algorithm is
   38 seconds for a typical host such as Windows 7).  This means that
   the content of the neighbor cache must periodically be fetched every
   30 seconds (to be on the safe side) and stored for later use.

   This is an important source of information because it is trivial (on
   a switch not using the SAVI [RFC7039] algorithm) to defeat the
   mapping between data-link layer address and IPv6 address.  Let us
   rephrase the previous statement: having access to the current and
   past content of the neighbor cache has a paramount value for forensic
   and audit trail.  Stateful DHCPv6 Lease

   In some networks, IPv6 addresses are managed by stateful DHCPv6
   server [RFC3315] that leases IPv6 addresses to clients.  It is indeed
   quite similar to DHCP for IPv4 so it can be tempting to use this DHCP
   lease file to discover the mapping between IPv6 addresses and data-
   link layer addresses as it was usually done in the IPv4 era.

   It is not so easy in the IPv6 era because not all nodes will use
   DHCPv6 (there are nodes which can only do stateless
   autoconfiguration) but also because DHCPv6 clients are identified not
   by their hardware-client address as in IPv4 but by a DHCP Unique ID
   (DUID) which can have several formats: some being the data-link layer
   address, some being data-link layer address prepended with time
   information or even an opaque number which is useless for operation
   security.  Moreover, when the DUID is based on the data-link address,
   this address can be of any interface of the client (such as the

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   wireless interface while the client actually uses its wired interface
   to connect to the network).

   If a lightweight DHCP relay agent [RFC6221] is used in the layer-2
   switches, then the DHCP server also receives the Interface-ID
   information which could be save in order to identifity the interface
   of the switches which received a specific leased IPv6 address.

   In short, the DHCPv6 lease file is less interesting than in the IPv4
   era.  DHCPv6 servers that keeps the relayed data-link layer address
   in addition to the DUID in the lease file do not suffer from this
   limitation.  On a managed network where all hosts support DHCPv6,
   special care must be taken to prevent stateless autoconfiguration
   anyway (and if applicable) by sending RA with all announced prefixes
   without the A-bit set.

   The mapping between data-link layer address and the IPv6 address can
   be secured by using switches implementing the SAVI [RFC7513]
   algorithms.  RADIUS Accounting Log

   For interfaces where the user is authenticated via a RADIUS [RFC2866]
   server, and if RADIUS accounting is enabled, then the RADIUS server
   receives accounting Acct-Status-Type records at the start and at the
   end of the connection which include all IPv6 (and IPv4) addresses
   used by the user.  This technique can be used notably for Wi-Fi
   networks with Wi-Fi Protected Address (WPA) or any other IEEE 802.1X
   [IEEE-802.1X]wired interface on an Ethernet switch.  Other Data Sources

   There are other data sources that must be kept exactly as in the IPv4

   o  historical mapping of IPv6 addresses to users of remote access

   o  historical mapping of MAC address to switch interface in a wired

2.6.2.  Use of Collected Data

   This section leverages the data collected as described before
   (Section 2.6.1) in order to achieve several security benefits.

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   The forensic use case is when the network operator must locate an
   IPv6 address that was present in the network at a certain time or is
   still currently in the network.

   The source of information can be, in decreasing order, neighbor
   cache, DHCP lease file.  Then, the procedure is:

   1.  based on the IPv6 prefix of the IPv6 address find the router(s)
       which are used to reach this prefix;

   2.  based on this limited set of routers, on the incident time and on
       IPv6 address to retrieve the data-link address from live neighbor
       cache, from the historical data of the neighbor cache, or from
       the DHCP lease file;

   3.  based on the data-link layer address, look-up on which switch
       interface was this data-link layer address.  In the case of
       wireless LAN, the RADIUS log should have the mapping between user
       identification and the MAC address.

   At the end of the process, the interface where the malicious user was
   connected or the username that was used by the malicious user is
   found.  Inventory

   RFC 5157 [RFC5157] is about the difficulties to scan an IPv6 network
   due to the vast number of IPv6 addresses per link.  This has the side
   effect of making the inventory task difficult in an IPv6 network
   while it was trivial to do in an IPv4 network (a simple enumeration
   of all IPv4 addresses, followed by a ping and a TCP/UDP port scan).
   Getting an inventory of all connected devices is of prime importance
   for a secure operation of a network.

   There are two ways to do an inventory of an IPv6 network.

   The first technique is to use the IPfix information and extract the
   list of all IPv6 source addresses to find all IPv6 nodes that sent
   packets through a router.  This is very efficient but alas will not
   discover silent node that never transmitted such packets... Also, it
   must be noted that link-local addresses will never be discovered by
   this means.

   The second way is again to use the collected neighbor cache content
   to find all IPv6 addresses in the cache.  This process will also
   discover all link-local addresses.  See Section

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   Another way works only for local network, it consists in sending a
   ICMP ECHO_REQUEST to the link-local multicast address ff02::1 which
   is all IPv6 nodes on the network.  All nodes should reply to this
   ECHO_REQUEST per [RFC4443].  Correlation

   In an IPv4 network, it is easy to correlate multiple logs, for
   example to find events related to a specific IPv4 address.  A simple
   Unix grep command was enough to scan through multiple text-based
   files and extract all lines relevant to a specific IPv4 address.

   In an IPv6 network, this is slightly more difficult because different
   character strings can express the same IPv6 address.  Therefore, the
   simple Unix grep command cannot be used.  Moreover, an IPv6 node can
   have multiple IPv6 addresses...

   In order to do correlation in IPv6-related logs, it is advised to
   have all logs with canonical IPv6 addresses.  Then, the neighbor
   cache current (or historical) data set must be searched to find the
   data-link layer address of the IPv6 address.  Then, the current and
   historical neighbor cache data sets must be searched for all IPv6
   addresses associated to this data-link layer address: this is the
   search set.  The last step is to search in all log files (containing
   only IPv6 address in canonical format) for any IPv6 addresses in the
   search set.  Abnormal Behavior Detection

   Abnormal behaviors (such as network scanning, spamming, denial of
   service) can be detected in the same way as in an IPv4 network

   o  sudden increase of traffic detected by interface counter (SNMP) or
      by aggregated traffic from IPfix records [RFC7012];

   o  change of traffic pattern (number of connection per second, number
      of connection per host...) with the use of IPfix [RFC7012]

2.6.3.  Summary

   While some data sources (IPfix, MIB, switch CAM tables, logs, ...)
   used in IPv4 are also used in the secure operation of an IPv6
   network, the DHCPv6 lease file is less reliable and the neighbor
   cache is of prime importance.

   The fact that there are multiple ways to express in a character
   string the same IPv6 address renders the use of filters mandatory
   when correlation must be done.

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2.7.  Transition/Coexistence Technologies

   Some text

2.7.1.  Dual Stack

   Dual stack has established itself as the preferred deployment choice
   for most network operators without a MPLS core where 6PE [RFC4798] is
   quite common.  Dual stacking the network offers many advantages over
   other transition mechanisms.  Firstly, it is easy to turn on without
   impacting normal IPv4 operations.  Secondly, perhaps more
   importantly, it is easier to troubleshoot when things break.  Dual
   stack allows you to gradually turn IPv4 operations down when your
   IPv6 network is ready for prime time.

   From an operational security perspective, this now means that you
   have twice the exposure.  One needs to think about protecting both
   protocols now.  At a minimum, the IPv6 portion of a dual stacked
   network should maintain parity with IPv4 from a security policy point
   of view.  Typically, the following methods are employed to protect
   IPv4 networks at the edge:

   o  ACLs to permit or deny traffic

   o  Firewalls with stateful packet inspection

   It is recommended that these ACLs and/or firewalls be additionally
   configured to protect IPv6 communications.  Also, given the end-to-
   end connectivity that IPv6 provides, it is also recommended that
   hosts be fortified against threats.  General device hardening
   guidelines are provided in Section 2.8

2.7.2.  Transition Mechanisms

   There are many tunnels used for specific use cases.  Except when
   protected by IPsec [RFC4301], all those tunnels have a couple of
   security issues (most of them being described in RFC 6169 [RFC6169]);

   o  tunnel injection: a malevolent person knowing a few pieces of
      information (for example the tunnel endpoints and the used
      protocol) can forge a packet which looks like a legit and valid
      encapsulated packet that will gladly be accepted by the
      destination tunnel endpoint, this is a specific case of spoofing;

   o  traffic interception: no confidentiality is provided by the tunnel
      protocols (without the use of IPsec), therefore anybody on the
      tunnel path can intercept the traffic and have access to the
      clear-text IPv6 packet;

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   o  service theft: as there is no authorization, even a non authorized
      user can use a tunnel relay for free (this is a specific case of
      tunnel injection);

   o  reflection attack: another specific use case of tunnel injection
      where the attacker injects packets with an IPv4 destination
      address not matching the IPv6 address causing the first tunnel
      endpoint to re-encapsulate the packet to the destination... Hence,
      the final IPv4 destination will not see the original IPv4 address
      but only one IPv4 address of the relay router.

   o  bypassing security policy: if a firewall or an IPS is on the path
      of the tunnel, then it will probably neither inspect not detect an
      malevolent IPv6 traffic contained in the tunnel.

   To mitigate the bypassing of security policies, it could be helpful
   to block all default configuration tunnels by denying all IPv4
   traffic matching:

   o  IP protocol 41: this will block ISATAP (Section, 6to4
      (Section, 6rd (Section as well as 6in4
      (Section tunnels;

   o  IP protocol 47: this will block GRE (Section tunnels;

   o  UDP protocol 3544: this will block the default encapsulation of
      Teredo (Section tunnels.

   Ingress filtering [RFC2827] should also be applied on all tunnel
   endpoints if applicable to prevent IPv6 address spoofing.

   As several of the tunnel techniques share the same encapsulation
   (i.e.  IPv4 protocol 41) and embeb the IPv4 address in the IPv6
   address, there are a set of well-known looping attacks described in
   RFC 6324 [RFC6324], this RFC also proposes mitigation techniques.  Site-to-Site Static Tunnels

   Site-to-site static tunnels are described in RFC 2529 [RFC2529] and
   in GRE [RFC2784].  As the IPv4 endpoints are statically configured
   and are not dynamic they are slightly more secure (bi-directional
   service theft is mostly impossible) but traffic interception ad
   tunnel injection are still possible.  Therefore, the use of IPsec
   [RFC4301] in transport mode and protecting the encapsulated IPv4
   packets is recommended for those tunnels.  Alternatively, IPsec in
   tunnel mode can be used to transport IPv6 traffic over a non-trusted
   IPv4 network.

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   ISATAP tunnels [RFC5214] are mainly used within a single
   administrative domain and to connect a single IPv6 host to the IPv6
   network.  This means that endpoints and and the tunnel endpoint are
   usually managed by a single entity; therefore, audit trail and strict
   anti-spoofing are usually possible and this raises the overall

   Special care must be taken to avoid looping attack by implementing
   the measures of RFC 6324 [RFC6324] and of [RFC6964].

   IPsec [RFC4301] in transport or tunnel mode can be used to secure the
   IPv4 ISATAP traffic to provide IPv6 traffic confidentiality and
   prevent service theft.  Teredo

   Teredo tunnels [RFC4380] are mainly used in a residential environment
   because that can easily traverse an IPv4 NAT-PT device thanks to its
   UDP encapsulation and they connect a single host to the IPv6
   Internet.  Teredo shares the same issues as other tunnels: no
   authentication, no confidentiality, possible spoofing and reflection

   IPsec [RFC4301] for the transported IPv6 traffic is recommended.

   The biggest threat to Teredo is probably for IPv4-only network as
   Teredo has been designed to easily traverse IPV4 NAT-PT devices which
   are quite often co-located with a stateful firewall.  Therefore, if
   the stateful IPv4 firewall allows unrestricted UDP outbound and
   accept the return UDP traffic, then Teredo actually punches a hole in
   this firewall for all IPv6 traffic to the Internet and from the
   Internet.  While host policies can be deployed to block Teredo in an
   IPv4-only network in order to avoid this firewall bypass, it would be
   more efficient to block all UDP outbound traffic at the IPv4 firewall
   if deemed possible (of course, at least port 53 should be left open
   for DNS traffic).  6to4

   6to4 tunnels [RFC3056] require a public routable IPv4 address in
   order to work correctly.  They can be used to provide either one IPv6
   host connectivity to the IPv6 Internet or multiple IPv6 networks
   connectivity to the IPV6 Internet.  The 6to4 relay is usually the
   anycast address defined in [RFC3068].  Some security considerations
   are explained in [RFC3964].

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   [RFC6343] points out that if an operator provides well-managed
   servers and relays for 6to4, non-encapsulated IPv6 packets will pass
   through well- defined points (the native IPv6 interfaces of those
   servers and relays) at which security mechanisms may be applied.
   Client usage of 6to4 by default is now discouraged, and significant
   precautions are needed to avoid operational problems  6rd

   While 6rd tunnels share the same encapsulation as 6to4 tunnels
   (Section, they are designed to be used within a single SP
   domain, in other words they are deployed in a more constrained
   environment than 6to4 tunnels and have little security issues except
   lack of confidentiality.  The security considerations (Section 12) of
   [RFC5969] describes how to secure the 6rd tunnels.

   IPsec [RFC4301] for the transported IPv6 traffic can be used if
   confidentiality is important.  6PE and 6VPE

   Organizations using MPLS in their core can also use 6PE [RFC4798] and
   6VPE [RFC4659] to enable IPv6 access over MPLS.  As 6PE and 6VPE are
   really similar to BGP/MPLS IP VPN described in [RFC4364], the
   security of these networks is also similar to the one described in
   [RFC4381].  It relies on:

   o  Address space, routing and traffic seperation with the help of VRF
      (only applicable to 6VPE);

   o  Hiding the IPv4 core, hence removing all attacks against

   o  Securing the routing protocol between CE and PE, in the case of
      6PE and 6VPE, link-local addresses (see [RFC7404]) can be used and
      as these addresses cannot be reached from outside of the link, the
      security of 6PE and 6VPE is even higher than the IPv4 BGP/MPLS IP
      VPN.  DS-Lite

   DS-lite is more a translation mechanism and is therefore analyzed
   further (Section in this document.

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   With the tunnel and encapsulation versions of Mapping of Address and
   Port (MAP [RFC7597]), the access network is purely an IPv6 network
   and MAP protocols are used to give IPv4 hosts on the subscriber
   network, access to IPv4 hosts on the Internet.  The subscriber router
   does stateful operations in order to map all internal IPv4 addresses
   and layer-4 ports to the IPv4 address and the set of layer-4 ports
   received through MAP configuration process.  The SP equipment always
   does stateless operations (either decapsulation or stateless
   translation).  Therefore, as opposed to Section there is no
   state-exhaustion DoS attack against the SP equipment because there is
   no state and there is no operation caused by a new layer-4 connection
   (no logging operation).

   The SP MAP equipment MUST implement all the security considerations
   of [RFC7597]; notably, ensuring that the mapping of the IPv4 address
   and port are consistent with the configuration.  As MAP has a
   predictable IPv4 address and port mapping, the audit log are easier
   to manager.

2.7.3.  Translation Mechanisms

   Translation mechanisms between IPv4 and IPv6 networks are alternative
   coexistence strategies while networks transition to IPv6.  While a
   framework is described in [RFC6144] the specific security
   considerations are documented in each individual mechanism.  For the
   most part they specifically mention interference with IPsec or DNSSEC
   deployments, how to mitigate spoofed traffic and what some effective
   filtering strategies may be.  Carrier-Grade Nat (CGN)

   Carrier-Grade NAT (CGN), also called NAT444 CGN or Large Scale NAT
   (LSN) or SP NAT is described in [RFC6264] and is utilized as an
   interim measure to prolong the use of IPv4 in a large service
   provider network until the provider can deploy and effective IPv6
   solution.  [RFC6598] requested a specific IANA allocated /10 IPv4
   address block to be used as address space shared by all access
   networks using CGN.  This has been allocated as

   Section 13 of [RFC6269] lists some specific security-related issues
   caused by large scale address sharing.  The Security Considerations
   section of [RFC6598] also lists some specific mitigation techniques
   for potential misuse of shared address space.

   [From Panos K: could mention the log size concern and draft-donley-
   behave-deterministic-cgn that alleviates it]

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   Stateful NAT64 translation [RFC6146] allows IPv6-only clients to
   contact IPv4 servers using unicast UDP, TCP, or ICMP.  It can be used
   in conjunction with DNS64 [RFC6147], a mechanism which synthesizes
   AAAA records from existing A records.

   The Security Consideration sections of [RFC6146] and [RFC6147] list
   the comprehensive issues.  A specific issue with the use of NAT64 is
   that it will interfere with most IPsec deployments unless UDP
   encapsulation is used.  DNS64 has an incidence on DNSSEC see section
   3.1 of [RFC7050].  DS-lite

   Dual-Stack Lite (DS-Lite) [RFC6333] is a transition technique that
   enables a service provider to share IPv4 addresses among customers by
   combining two well-known technologies: IP in IP (IPv4-in-IPv6) and
   Network Address and Port Translation (NAPT)

   Security considerations with respect to DS-Lite mainly revolve around
   logging data, preventing DoS attacks from rogue devices and
   restricting service offered by the AFTR only to registered customers.

   Section 11 of [RFC6333] describes important security issues
   associated with this technology.

2.8.  General Device Hardening

   There are many environments which rely too much on the network
   infrastructure to disallow malicious traffic to get access to
   critical hosts.  In new IPv6 deployments it has been common to see
   IPv6 traffic enabled but none of the typical access control
   mechanisms enabled for IPv6 device access.  With the possibility of
   network device configuration mistakes and the growth of IPv6 in the
   overall Internet it is important to ensure that all individual
   devices are hardened agains miscreant behavior.

   The following guidelines should be used to ensure appropriate
   hardening of the host, be it an individual computer or router,
   firewall, load-balancer,server, etc device.

   o  Restrict access to the device to authenticated and authorized

   o  Monitor and audit access to the device

   o  Turn off any unused services on the end node

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   o  Understand which IPv6 addresses are being used to source traffic
      and change defaults if necessary

   o  Use cryptographically protected protocols for device management if
      possible (SCP, SNMPv3, SSH, TLS, etc)

   o  Use host firewall capabilities to control traffic that gets
      processed by upper layer protocols

   o  Use virus scanners to detect malicious programs

3.  Enterprises Specific Security Considerations

   Enterprises generally have robust network security policies in place
   to protect existing IPv4 networks.  These policies have been
   distilled from years of experiential knowledge of securing IPv4
   networks.  At the very least, it is recommended that enterprise
   networks have parity between their security policies for both
   protocol versions.

   Security considerations in the enterprise can be broadly categorized
   into two sections - External and Internal.

3.1.  External Security Considerations:

   The external aspect deals with providing security at the edge or
   perimeter of the enterprise network where it meets the service
   providers network.  This is commonly achieved by enforcing a security
   policy either by implementing dedicated firewalls with stateful
   packet inspection or a router with ACLs.  A common default IPv4
   policy on firewalls that could easily be ported to IPv6 is to allow
   all traffic outbound while only allowing specific traffic, such as
   established sessions, inbound.  Here are a few more things that could
   enhance the default policy:

   o  Filter internal-use IPv6 addresses at the perimeter

   o  Discard packets from and to bogon and reserved space

   o  Accept certain ICMPv6 messages to allow proper operation of ND and
      PMTUD, see also [RFC4890]

   o  Filter specific extension headers, where possible

   o  Filter unneeded services at the perimeter

   o  Implement anti-spoofing

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   o  Implement appropriate rate-limiters and control-plane policers

3.2.  Internal Security Considerations:

   The internal aspect deals with providing security inside the
   perimeter of the network, including the end host.  The most
   significant concerns here are related to Neighbor Discovery.  At the
   network level, it is recommended that all security considerations
   discussed in Section 2.3 be reviewed carefully and the
   recommendations be considered in-depth as well.

   As mentioned in Section 2.6.2, care must be taken when running
   automated IPv6-in-IP4 tunnels.

   Hosts need to be hardened directly through security policy to protect
   against security threats.  The host firewall default capabilities
   have to be clearly understood, especially 3rd party ones which can
   have different settings for IPv4 or IPv6 default permit/deny
   behavior.  In some cases, 3rd party firewalls have no IPv6 support
   whereas the native firewall installed by default has it.  General
   device hardening guidelines are provided in Section 2.8

   It should also be noted that many hosts still use IPv4 for transport
   for things like RADIUS, TACACS+, SYSLOG, etc.  This will require some
   extra level of due diligence on the part of the operator.

4.  Service Providers Security Considerations

4.1.  BGP

   The threats and mitigation techniques are identical between IPv4 and
   IPv6.  Broadly speaking they are:

   o  Authenticating the TCP session;

   o  TTL security (which becomes hop-limit security in IPv6);

   o  Prefix Filtering.

   These are explained in more detail in section Section 2.5.

4.1.1.  Remote Triggered Black Hole Filtering

   RTBH [RFC5635] works identically in IPv4 and IPv6.  IANA has
   allocated 100::/64 as discard prefix [RFC6666].

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4.2.  Transition Mechanism

   SP will typically use transition mechanisms such as 6rd, 6PE, MAP,
   DS-LITE which have been analyzed in the transition Section 2.7.2

4.3.  Lawful Intercept

   The Lawful Intercept requirements are similar for IPv6 and IPv4
   architectures and will be subject to the laws enforced in varying
   geographic regions.  The local issues with each jurisdiction can make
   this challenging and both corporate legal and privacy personnel
   should be involved in discussions pertaining to what information gets
   logged and what the logging retention policies will be.

   The target of interception will usually be a residential subscriber
   (e.g. his/her PPP session or physical line or CPE MAC address).  With
   the absence of NAT on the CPE, IPv6 has the provision to allow for
   intercepting the traffic from a single host (a /128 target) rather
   than the whole set of hosts of a subscriber (which could be a /48, a
   /60 or /64).

   In contrast, in mobile environments, since the 3GPP specifications
   allocate a /64 per device, it may be sufficient to intercept traffic
   from the /64 rather than specific /128's (since each time the device
   powers up it gets a new IID).

   A sample architecture which was written for informational purposes is
   found in [RFC3924].

5.  Residential Users Security Considerations

   The IETF Homenet working group is working on how IPv6 residential
   network should be done; this obviously includes operational security
   considerations; but, this is still work in progress.

   Residential users have usually less experience and knowledge about
   security or networking.  As most of the recent hosts, smartphones,
   tablets have all IPv6 enabled by default, IPv6 security is important
   for those users.  Even with an IPv4-only ISP, those users can get
   IPv6 Internet access with the help of Teredo tunnels.  Several peer-
   to-peer programs (notably Bittorrent) support IPv6 and those programs
   can initiate a Teredo tunnel through the IPv4 residential gateway,
   with the consequence of making the internal host reachable from any
   IPv6 host on the Internet.  It is therefore recommended that all host
   security products (personal firewall, ...) are configured with a
   dual-stack security policy.

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   If the Residential Gateway has IPv6 connectivity, [RFC7084] (which
   obsoletes [RFC6204] defines the requirements of an IPv6 CPE and does
   not take position on the debate of default IPv6 security policy:

   o  outbound only: allowing all internally initiated connections and
      block all externally initiated ones, which is a common default
      security policy enforced by IPv4 Residential Gateway doing NAT-PT
      but it also breaks the end-to-end reachability promise of IPv6.
      [RFC6092] lists several recommendations to design such a CPE;

   o  open: allowing all internally and externally initiated
      connections, therefore restoring the end-to-end nature of the
      Internet for the IPv6 traffic but having a different security
      policy for IPv6 than for IPv4.

   [RFC7084] states that a clear choice must be given to the user to
   select one of those two policies.

   There is also an alternate solution which has been deployed notably
   by Swisscom ([I-D.ietf-v6ops-balanced-ipv6-security]: open to all
   outbound and inbound connections at the exception of an handful of
   TCP and UDP ports known as vulnerable.

6.  Further Reading

   There are several documents that describe in more details the
   security of an IPv6 network; these documents are not written by the
   IETF but are listed here for your convenience:

   1.  Guidelines for the Secure Deployment of IPv6 [NIST]

   2.  North American IPv6 Task Force Technology Report - IPv6 Security
       Technology Paper [NAv6TF_Security]

   3.  IPv6 Security [IPv6_Security_Book]

7.  Acknowledgements

   The authors would like to thank the following people for their useful
   comments: Mikael Abrahamsson, Brian Carpenter, Tim Chown, Fernando
   Gont, Jeffry Handal, Panos Kampanakis, Jouni Korhonen, Mark
   Lentczner, Tarko Tikan (by alphabetical order).

8.  IANA Considerations

   This memo includes no request to IANA.

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9.  Security Considerations

   This memo attempts to give an overview of security considerations of
   operating an IPv6 network both in an IPv6-only network and in
   utilizing the most widely deployed IPv4/IPv6 coexistence strategies.

10.  References

10.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,

   [RFC6104]  Chown, T. and S. Venaas, "Rogue IPv6 Router Advertisement
              Problem Statement", RFC 6104, DOI 10.17487/RFC6104,
              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,
              DOI 10.17487/RFC6105, February 2011,

10.2.  Informative References

   [CYMRU]    "Packet Filter and Route Filter Recommendation for IPv6 at
              xSP routers", <http://www.team-

              Chakrabarti, S., Nordmark, E., Thubert, P., and M.
              Wasserman, "IPv6 Neighbor Discovery Optimizations for
              Wired and Wireless Networks", draft-chakrabarti-nordmark-
              6man-efficient-nd-07 (work in progress), February 2015.

              Cooper, A., Gont, F., and D. Thaler, "Privacy
              Considerations for IPv6 Address Generation Mechanisms",
              draft-ietf-6man-ipv6-address-generation-privacy-07 (work
              in progress), June 2015.

              Gysi, M., Leclanche, G., Vyncke, E., and R. Anfinsen,
              "Balanced Security for IPv6 Residential CPE", draft-ietf-
              v6ops-balanced-ipv6-security-01 (work in progress),
              December 2013.

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              Thubert, P., "Throttling RAs on constrained interfaces",
              draft-thubert-savi-ra-throttler-01 (work in progress),
              June 2012.

              IEEE, , "IEEE Standard for Local and metropolitan area
              networks - Port-Based Network Access Control", IEEE Std
              802.1X-2010, February 2010.

              Hogg, and Vyncke, "IPv6 Security", ISBN 1-58705-594-5,
              Publisher CiscoPress, December 2008.

              Kaeo, , Green, , Bound, , and Pouffary, "North American
              IPv6 Task Force Technology Report - IPv6 Security
              Technology Paper", 2006,

   [NIST]     Frankel, , Graveman, , Pearce, , and Rooks, "Guidelines
              for the Secure Deployment of IPv6", 2010,

   [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, DOI 10.17487/RFC0826, November 1982,

   [RFC2131]  Droms, R., "Dynamic Host Configuration Protocol",
              RFC 2131, DOI 10.17487/RFC2131, March 1997,

   [RFC2529]  Carpenter, B. and C. Jung, "Transmission of IPv6 over IPv4
              Domains without Explicit Tunnels", RFC 2529,
              DOI 10.17487/RFC2529, March 1999,

   [RFC2740]  Coltun, R., Ferguson, D., and J. Moy, "OSPF for IPv6",
              RFC 2740, DOI 10.17487/RFC2740, December 1999,

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   [RFC2784]  Farinacci, D., Li, T., Hanks, S., Meyer, D., and P.
              Traina, "Generic Routing Encapsulation (GRE)", RFC 2784,
              DOI 10.17487/RFC2784, March 2000,

   [RFC2827]  Ferguson, P. and D. Senie, "Network Ingress Filtering:
              Defeating Denial of Service Attacks which employ IP Source
              Address Spoofing", BCP 38, RFC 2827, DOI 10.17487/RFC2827,
              May 2000, <http://www.rfc-editor.org/info/rfc2827>.

   [RFC2866]  Rigney, C., "RADIUS Accounting", RFC 2866,
              DOI 10.17487/RFC2866, June 2000,

   [RFC3056]  Carpenter, B. and K. Moore, "Connection of IPv6 Domains
              via IPv4 Clouds", RFC 3056, DOI 10.17487/RFC3056, February
              2001, <http://www.rfc-editor.org/info/rfc3056>.

   [RFC3068]  Huitema, C., "An Anycast Prefix for 6to4 Relay Routers",
              RFC 3068, DOI 10.17487/RFC3068, June 2001,

   [RFC3315]  Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins,
              C., and M. Carney, "Dynamic Host Configuration Protocol
              for IPv6 (DHCPv6)", RFC 3315, DOI 10.17487/RFC3315, July
              2003, <http://www.rfc-editor.org/info/rfc3315>.

   [RFC3627]  Savola, P., "Use of /127 Prefix Length Between Routers
              Considered Harmful", RFC 3627, DOI 10.17487/RFC3627,
              September 2003, <http://www.rfc-editor.org/info/rfc3627>.

   [RFC3756]  Nikander, P., Ed., Kempf, J., and E. Nordmark, "IPv6
              Neighbor Discovery (ND) Trust Models and Threats",
              RFC 3756, DOI 10.17487/RFC3756, May 2004,

   [RFC3924]  Baker, F., Foster, B., and C. Sharp, "Cisco Architecture
              for Lawful Intercept in IP Networks", RFC 3924,
              DOI 10.17487/RFC3924, October 2004,

   [RFC3964]  Savola, P. and C. Patel, "Security Considerations for
              6to4", RFC 3964, DOI 10.17487/RFC3964, December 2004,

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   [RFC3971]  Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander,
              "SEcure Neighbor Discovery (SEND)", RFC 3971,
              DOI 10.17487/RFC3971, March 2005,

   [RFC3972]  Aura, T., "Cryptographically Generated Addresses (CGA)",
              RFC 3972, DOI 10.17487/RFC3972, March 2005,

   [RFC4193]  Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
              Addresses", RFC 4193, DOI 10.17487/RFC4193, October 2005,

   [RFC4293]  Routhier, S., Ed., "Management Information Base for the
              Internet Protocol (IP)", RFC 4293, DOI 10.17487/RFC4293,
              April 2006, <http://www.rfc-editor.org/info/rfc4293>.

   [RFC4301]  Kent, S. and K. Seo, "Security Architecture for the
              Internet Protocol", RFC 4301, DOI 10.17487/RFC4301,
              December 2005, <http://www.rfc-editor.org/info/rfc4301>.

   [RFC4364]  Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
              Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February
              2006, <http://www.rfc-editor.org/info/rfc4364>.

   [RFC4380]  Huitema, C., "Teredo: Tunneling IPv6 over UDP through
              Network Address Translations (NATs)", RFC 4380,
              DOI 10.17487/RFC4380, February 2006,

   [RFC4381]  Behringer, M., "Analysis of the Security of BGP/MPLS IP
              Virtual Private Networks (VPNs)", RFC 4381,
              DOI 10.17487/RFC4381, February 2006,

   [RFC4443]  Conta, A., Deering, S., and M. Gupta, Ed., "Internet
              Control Message Protocol (ICMPv6) for the Internet
              Protocol Version 6 (IPv6) Specification", RFC 4443,
              DOI 10.17487/RFC4443, March 2006,

   [RFC4552]  Gupta, M. and N. Melam, "Authentication/Confidentiality
              for OSPFv3", RFC 4552, DOI 10.17487/RFC4552, June 2006,

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   [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, DOI 10.17487/RFC4659, September 2006,

   [RFC4798]  De Clercq, J., Ooms, D., Prevost, S., and F. Le Faucheur,
              "Connecting IPv6 Islands over IPv4 MPLS Using IPv6
              Provider Edge Routers (6PE)", RFC 4798,
              DOI 10.17487/RFC4798, February 2007,

   [RFC4861]  Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
              "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
              DOI 10.17487/RFC4861, September 2007,

   [RFC4864]  Van de Velde, G., Hain, T., Droms, R., Carpenter, B., and
              E. Klein, "Local Network Protection for IPv6", RFC 4864,
              DOI 10.17487/RFC4864, May 2007,

   [RFC4890]  Davies, E. and J. Mohacsi, "Recommendations for Filtering
              ICMPv6 Messages in Firewalls", RFC 4890,
              DOI 10.17487/RFC4890, May 2007,

   [RFC4941]  Narten, T., Draves, R., and S. Krishnan, "Privacy
              Extensions for Stateless Address Autoconfiguration in
              IPv6", RFC 4941, DOI 10.17487/RFC4941, September 2007,

   [RFC4942]  Davies, E., Krishnan, S., and P. Savola, "IPv6 Transition/
              Co-existence Security Considerations", RFC 4942,
              DOI 10.17487/RFC4942, September 2007,

   [RFC5157]  Chown, T., "IPv6 Implications for Network Scanning",
              RFC 5157, DOI 10.17487/RFC5157, March 2008,

   [RFC5214]  Templin, F., Gleeson, T., and D. Thaler, "Intra-Site
              Automatic Tunnel Addressing Protocol (ISATAP)", RFC 5214,
              DOI 10.17487/RFC5214, March 2008,

   [RFC5340]  Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF
              for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008,

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   [RFC5635]  Kumari, W. and D. McPherson, "Remote Triggered Black Hole
              Filtering with Unicast Reverse Path Forwarding (uRPF)",
              RFC 5635, DOI 10.17487/RFC5635, August 2009,

   [RFC5952]  Kawamura, S. and M. Kawashima, "A Recommendation for IPv6
              Address Text Representation", RFC 5952,
              DOI 10.17487/RFC5952, August 2010,

   [RFC5969]  Townsley, W. and O. Troan, "IPv6 Rapid Deployment on IPv4
              Infrastructures (6rd) -- Protocol Specification",
              RFC 5969, DOI 10.17487/RFC5969, August 2010,

   [RFC6092]  Woodyatt, J., Ed., "Recommended Simple Security
              Capabilities in Customer Premises Equipment (CPE) for
              Providing Residential IPv6 Internet Service", RFC 6092,
              DOI 10.17487/RFC6092, January 2011,

   [RFC6144]  Baker, F., Li, X., Bao, C., and K. Yin, "Framework for
              IPv4/IPv6 Translation", RFC 6144, DOI 10.17487/RFC6144,
              April 2011, <http://www.rfc-editor.org/info/rfc6144>.

   [RFC6146]  Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful
              NAT64: Network Address and Protocol Translation from IPv6
              Clients to IPv4 Servers", RFC 6146, DOI 10.17487/RFC6146,
              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,
              DOI 10.17487/RFC6147, April 2011,

   [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, DOI 10.17487/RFC6164, April 2011,

   [RFC6169]  Krishnan, S., Thaler, D., and J. Hoagland, "Security
              Concerns with IP Tunneling", RFC 6169,
              DOI 10.17487/RFC6169, April 2011,

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   [RFC6192]  Dugal, D., Pignataro, C., and R. Dunn, "Protecting the
              Router Control Plane", RFC 6192, DOI 10.17487/RFC6192,
              March 2011, <http://www.rfc-editor.org/info/rfc6192>.

   [RFC6204]  Singh, H., Beebee, W., Donley, C., Stark, B., and O.
              Troan, Ed., "Basic Requirements for IPv6 Customer Edge
              Routers", RFC 6204, DOI 10.17487/RFC6204, April 2011,

   [RFC6221]  Miles, D., Ed., Ooghe, S., Dec, W., Krishnan, S., and A.
              Kavanagh, "Lightweight DHCPv6 Relay Agent", RFC 6221,
              DOI 10.17487/RFC6221, May 2011,

   [RFC6264]  Jiang, S., Guo, D., and B. Carpenter, "An Incremental
              Carrier-Grade NAT (CGN) for IPv6 Transition", RFC 6264,
              DOI 10.17487/RFC6264, June 2011,

   [RFC6269]  Ford, M., Ed., Boucadair, M., Durand, A., Levis, P., and
              P. Roberts, "Issues with IP Address Sharing", RFC 6269,
              DOI 10.17487/RFC6269, June 2011,

   [RFC6296]  Wasserman, M. and F. Baker, "IPv6-to-IPv6 Network Prefix
              Translation", RFC 6296, DOI 10.17487/RFC6296, June 2011,

   [RFC6302]  Durand, A., Gashinsky, I., Lee, D., and S. Sheppard,
              "Logging Recommendations for Internet-Facing Servers",
              BCP 162, RFC 6302, DOI 10.17487/RFC6302, June 2011,

   [RFC6324]  Nakibly, G. and F. Templin, "Routing Loop Attack Using
              IPv6 Automatic Tunnels: Problem Statement and Proposed
              Mitigations", RFC 6324, DOI 10.17487/RFC6324, August 2011,

   [RFC6333]  Durand, A., Droms, R., Woodyatt, J., and Y. Lee, "Dual-
              Stack Lite Broadband Deployments Following IPv4
              Exhaustion", RFC 6333, DOI 10.17487/RFC6333, August 2011,

   [RFC6343]  Carpenter, B., "Advisory Guidelines for 6to4 Deployment",
              RFC 6343, DOI 10.17487/RFC6343, August 2011,

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   [RFC6434]  Jankiewicz, E., Loughney, J., and T. Narten, "IPv6 Node
              Requirements", RFC 6434, DOI 10.17487/RFC6434, December
              2011, <http://www.rfc-editor.org/info/rfc6434>.

   [RFC6459]  Korhonen, J., Ed., Soininen, J., Patil, B., Savolainen,
              T., Bajko, G., and K. Iisakkila, "IPv6 in 3rd Generation
              Partnership Project (3GPP) Evolved Packet System (EPS)",
              RFC 6459, DOI 10.17487/RFC6459, January 2012,

   [RFC6506]  Bhatia, M., Manral, V., and A. Lindem, "Supporting
              Authentication Trailer for OSPFv3", RFC 6506,
              DOI 10.17487/RFC6506, February 2012,

   [RFC6547]  George, W., "RFC 3627 to Historic Status", RFC 6547,
              DOI 10.17487/RFC6547, February 2012,

   [RFC6583]  Gashinsky, I., Jaeggli, J., and W. Kumari, "Operational
              Neighbor Discovery Problems", RFC 6583,
              DOI 10.17487/RFC6583, March 2012,

   [RFC6598]  Weil, J., Kuarsingh, V., Donley, C., Liljenstolpe, C., and
              M. Azinger, "IANA-Reserved IPv4 Prefix for Shared Address
              Space", BCP 153, RFC 6598, DOI 10.17487/RFC6598, April
              2012, <http://www.rfc-editor.org/info/rfc6598>.

   [RFC6620]  Nordmark, E., Bagnulo, M., and E. Levy-Abegnoli, "FCFS
              SAVI: First-Come, First-Served Source Address Validation
              Improvement for Locally Assigned IPv6 Addresses",
              RFC 6620, DOI 10.17487/RFC6620, May 2012,

   [RFC6666]  Hilliard, N. and D. Freedman, "A Discard Prefix for IPv6",
              RFC 6666, DOI 10.17487/RFC6666, August 2012,

   [RFC6810]  Bush, R. and R. Austein, "The Resource Public Key
              Infrastructure (RPKI) to Router Protocol", RFC 6810,
              DOI 10.17487/RFC6810, January 2013,

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   [RFC6964]  Templin, F., "Operational Guidance for IPv6 Deployment in
              IPv4 Sites Using the Intra-Site Automatic Tunnel
              Addressing Protocol (ISATAP)", RFC 6964,
              DOI 10.17487/RFC6964, May 2013,

   [RFC6980]  Gont, F., "Security Implications of IPv6 Fragmentation
              with IPv6 Neighbor Discovery", RFC 6980,
              DOI 10.17487/RFC6980, August 2013,

   [RFC7011]  Claise, B., Ed., Trammell, B., Ed., and P. Aitken,
              "Specification of the IP Flow Information Export (IPFIX)
              Protocol for the Exchange of Flow Information", STD 77,
              RFC 7011, DOI 10.17487/RFC7011, September 2013,

   [RFC7012]  Claise, B., Ed. and B. Trammell, Ed., "Information Model
              for IP Flow Information Export (IPFIX)", RFC 7012,
              DOI 10.17487/RFC7012, September 2013,

   [RFC7039]  Wu, J., Bi, J., Bagnulo, M., Baker, F., and C. Vogt, Ed.,
              "Source Address Validation Improvement (SAVI) Framework",
              RFC 7039, DOI 10.17487/RFC7039, October 2013,

   [RFC7050]  Savolainen, T., Korhonen, J., and D. Wing, "Discovery of
              the IPv6 Prefix Used for IPv6 Address Synthesis",
              RFC 7050, DOI 10.17487/RFC7050, November 2013,

   [RFC7084]  Singh, H., Beebee, W., Donley, C., and B. Stark, "Basic
              Requirements for IPv6 Customer Edge Routers", RFC 7084,
              DOI 10.17487/RFC7084, November 2013,

   [RFC7112]  Gont, F., Manral, V., and R. Bonica, "Implications of
              Oversized IPv6 Header Chains", RFC 7112,
              DOI 10.17487/RFC7112, January 2014,

   [RFC7113]  Gont, F., "Implementation Advice for IPv6 Router
              Advertisement Guard (RA-Guard)", RFC 7113,
              DOI 10.17487/RFC7113, February 2014,

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   [RFC7166]  Bhatia, M., Manral, V., and A. Lindem, "Supporting
              Authentication Trailer for OSPFv3", RFC 7166,
              DOI 10.17487/RFC7166, March 2014,

   [RFC7217]  Gont, F., "A Method for Generating Semantically Opaque
              Interface Identifiers with IPv6 Stateless Address
              Autoconfiguration (SLAAC)", RFC 7217,
              DOI 10.17487/RFC7217, April 2014,

   [RFC7381]  Chittimaneni, K., Chown, T., Howard, L., Kuarsingh, V.,
              Pouffary, Y., and E. Vyncke, "Enterprise IPv6 Deployment
              Guidelines", RFC 7381, DOI 10.17487/RFC7381, October 2014,

   [RFC7404]  Behringer, M. and E. Vyncke, "Using Only Link-Local
              Addressing inside an IPv6 Network", RFC 7404,
              DOI 10.17487/RFC7404, November 2014,

   [RFC7454]  Durand, J., Pepelnjak, I., and G. Doering, "BGP Operations
              and Security", BCP 194, RFC 7454, DOI 10.17487/RFC7454,
              February 2015, <http://www.rfc-editor.org/info/rfc7454>.

   [RFC7513]  Bi, J., Wu, J., Yao, G., and F. Baker, "Source Address
              Validation Improvement (SAVI) Solution for DHCP",
              RFC 7513, DOI 10.17487/RFC7513, May 2015,

   [RFC7597]  Troan, O., Ed., Dec, W., Li, X., Bao, C., Matsushima, S.,
              Murakami, T., and T. Taylor, Ed., "Mapping of Address and
              Port with Encapsulation (MAP-E)", RFC 7597,
              DOI 10.17487/RFC7597, July 2015,

   [RFC7610]  Gont, F., Liu, W., and G. Van de Velde, "DHCPv6-Shield:
              Protecting against Rogue DHCPv6 Servers", BCP 199,
              RFC 7610, DOI 10.17487/RFC7610, August 2015,

              "Mapping the Great Void - Smarter scanning for IPv6",

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Authors' Addresses

   Kiran K. Chittimaneni
   Dropbox Inc.
   185 Berry Street, Suite 400
   San Francisco, CA  94107

   Email: kk@dropbox.com

   Merike Kaeo
   Double Shot Security
   3518 Fremont Ave N 363
   Seattle  98103

   Phone: +12066696394
   Email: merike@doubleshotsecurity.com

   Eric Vyncke
   De Kleetlaan 6a
   Diegem  1831

   Phone: +32 2 778 4677
   Email: evyncke@cisco.com

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