Operational Security Capabilities for                    K. Chittimaneni
IPv6 Network Infrastructure                                       Google
Internet-Draft                                                   M. Kaeo
Intended status: Informational                                       ISC
Expires: January 17, 2013                                      E. Vyncke
                                                           Cisco Systems
                                                           July 16, 2012

         Operational Security Considerations for IPv6 Networks


   Network managers know how to operate securely IPv4 network: whether
   it is the Internet or an enterprise internal network.  IPv6 presents
   some new security challenges.  RFC 4942 describes the security issues
   in the protocol but network managers need also a more practical,
   operation-minded best common practices.

   This document analyzes the operational security issues in all places
   of a network (service providers, enterprises 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 January 17, 2013.

Copyright Notice

   Copyright (c) 2012 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

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   (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 . . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.1.  Requirements Language  . . . . . . . . . . . . . . . . . .  4
   2.  Generic Security Considerations  . . . . . . . . . . . . . . .  4
     2.1.  Addressing Architecture  . . . . . . . . . . . . . . . . .  4
       2.1.1.  Overall Structure  . . . . . . . . . . . . . . . . . .  4
       2.1.2.  Use of ULAs  . . . . . . . . . . . . . . . . . . . . .  5
       2.1.3.  Point-to-Point Links . . . . . . . . . . . . . . . . .  5
       2.1.4.  Privacy Addresses  . . . . . . . . . . . . . . . . . .  5
       2.1.5.  DHCP/DNS Considerations  . . . . . . . . . . . . . . .  6
     2.2.  Link Layer Security  . . . . . . . . . . . . . . . . . . .  6
       2.2.1.  SeND and CGA . . . . . . . . . . . . . . . . . . . . .  6
       2.2.2.  DHCP Snooping  . . . . . . . . . . . . . . . . . . . .  7
       2.2.3.  ND/RA Rate Limiting  . . . . . . . . . . . . . . . . .  7
       2.2.4.  ND/RA Filtering  . . . . . . . . . . . . . . . . . . .  8
     2.3.  Control Plane Security . . . . . . . . . . . . . . . . . .  9
       2.3.1.  Control Protocols  . . . . . . . . . . . . . . . . . . 10
       2.3.2.  Management Protocols . . . . . . . . . . . . . . . . . 10
       2.3.3.  Packet Exceptions  . . . . . . . . . . . . . . . . . . 11
     2.4.  Routing Security . . . . . . . . . . . . . . . . . . . . . 11
       2.4.1.  Authenticating Neighbors/Peers . . . . . . . . . . . . 12
       2.4.2.  Securing Routing Updates Between Peers . . . . . . . . 12
       2.4.3.  Route Filtering  . . . . . . . . . . . . . . . . . . . 12
     2.5.  Logging/Monitoring . . . . . . . . . . . . . . . . . . . . 13
       2.5.1.  Data Sources . . . . . . . . . . . . . . . . . . . . . 14
       2.5.2.  Use of Collected Data  . . . . . . . . . . . . . . . . 17
       2.5.3.  Summary  . . . . . . . . . . . . . . . . . . . . . . . 18
     2.6.  Transition/Coexistence Technologies  . . . . . . . . . . . 19
       2.6.1.  Dual Stack . . . . . . . . . . . . . . . . . . . . . . 19
       2.6.2.  Tunneling Mechanisms . . . . . . . . . . . . . . . . . 19
       2.6.3.  Translation Mechanisms . . . . . . . . . . . . . . . . 22
     2.7.  General Device Hardening . . . . . . . . . . . . . . . . . 23
   3.  Enterprises Specific Security Considerations . . . . . . . . . 23
     3.1.  External Security Considerations:  . . . . . . . . . . . . 24
     3.2.  Internal Security Considerations:  . . . . . . . . . . . . 24
   4.  Service Providers Security Considerations  . . . . . . . . . . 25
     4.1.  BGP  . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
       4.1.1.  Remote Triggered Black Hole  . . . . . . . . . . . . . 25

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     4.2.  Transition Mechanism . . . . . . . . . . . . . . . . . . . 25
       4.2.1.  6PE and 6VPE . . . . . . . . . . . . . . . . . . . . . 25
       4.2.2.  6rd  . . . . . . . . . . . . . . . . . . . . . . . . . 25
       4.2.3.  DS-lite  . . . . . . . . . . . . . . . . . . . . . . . 25
     4.3.  Lawful Intercept . . . . . . . . . . . . . . . . . . . . . 25
   5.  Residential Users Security Considerations  . . . . . . . . . . 25
   6.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 26
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 26
   8.  Security Considerations  . . . . . . . . . . . . . . . . . . . 26
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 27
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 27
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 27
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 31

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1.  Introduction

   Running an IPv6 network is new for most operators not only because
   they are not yet used to large scale IPv6 network 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].  Moreover, for end-users that usually
   combination in a single box Customer Premice Equipment (CPE) of
   firewall and Network Address and Port Translation [RFC3022] has lead
   to the common feeling that NATPT equals security and with IPv6 NATPT
   is no more needed.

   The deployment of IPv6 network is commonly done with the dual-stack
   technique [RFC4213] which also leads to specific security issues.

   This document complements [RFC4942] by listing all security issues
   when operating a network.

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.

2.  Generic Security Considerations

2.1.  Addressing Architecture

   IPv6 address allocations and overall architecture are an import part
   of securing IPv6.

2.1.1.  Overall Structure

   Once an address allocation has been assigned, there should be some
   thought given to an overall address allocation plan.  A structured
   address allocation plan can lead to more concise and simpler firewall
   filtering rules.  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
   network filters to permit or deny services between geographic

   An important consideration for manually configured addressing is to
   make them hard to guess whenever possible.  When manually configuring

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   interface ID's, the more common forms of starting at the beginning or
   end of a subnet boundary (i.e using a 1 or FF for routers) should be
   avoided.  This will make any potential reconnaissance attack attempt
   much more difficult.  Although some common multicast groups are
   defined for important networked devices and use of commonly repeated
   addresses make it easy figure out what the name servers, routers or
   other critical devices are, a non-random manual address scheme also
   makes it easy for a potential attacker using a "dictionary attack" of
   commonly used interface IDs to find your critical infrastructure.

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.  However, in practice some
   environments have chosen to create ULAs as a /32.  While ULAs can be
   useful for infrastructure hiding, it may create an issue in future if
   the decision at some point is to make the machines using ULAs
   globally reachable.  This would require renumbering or perhaps even
   stateful IPv6 Network Address Translation (NAT).  The latter would
   again be problematic in trying to track specific machines that may
   source malware.  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

   RFC3627 indicates that the use of a /64 is the best solution for
   point-to-point links while a /112 can be used if that's not possible.
   However, in current deployments where it is felt that using a /64 is
   wasteful for point-to-point links, many opt to use a /127 or /126
   subnet boundary and create manually defined IPv6 addresses for the
   point-to-point or tunnel endpoints.

2.1.4.  Privacy Addresses

   Randomly generating an interface ID, as described in RFC 3041, is
   part of stateless autoconfiguration and used to address some security
   concerns.  Stateless autoconfiguration relies on the automatically
   generated EUI-64 node address, which together with the /64 prefix
   make up the global unique IPv6 address.  The EUI-64 address is
   generated from the MAC address.  Since MAC addresses for specific
   vendor equipment can be know, it may be easy for a potential attacker
   to perform a more directed intelligent scan to try and ascertain
   specific vendor device reachability for exploitation.  Privacy
   addressing attempts to mitigate this threat.

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   As privacy addressing could also be used to hide illegal and unsavory
   activities, privacy addressing can be assigned, audited, and
   controlled in managed enterprise networks via DHCPv6.

   Some people also feel that stateless addressing means that we may not
   know addresses operating in our networks ahead of time in order to to
   build access control lists (ACLs) of authorized users.  While privacy
   addresses are truly generated randomly to protect against user
   tracking, but assuming that nodes use the EUI-64 format for global
   addressing, a list of expected pre-authorized host addresses can be

2.1.5.  DHCP/DNS Considerations

   Some text

2.2.  Link Layer Security

   Link layer security is quite possibly the most important and visible
   security consideration for most operators.  IPv6 relied heavily on
   the Neighbor Discovery protocol (NDP) [RFC4861] to perform a variety
   of link operations such as discovering other nodes not he 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

2.2.1.  SeND and CGA

   The original NDP specification called for using IPsec to protect
   Neighbor Discovery messages.  However, manually configuring security
   associations among multiple hosts on a large network can be very
   challenging.  SEcure Neighbor Discovery (SEND), as described in
   [RFC3971], is a mechanism designed to secure ND messages without
   having to rely on manual IPsec configuration.  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 address.  A new NDP option, the CGA option, 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

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   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.

   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

2.2.2.  DHCP Snooping

   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
   nodes.  DHCP plays an important role in any large network by
   providing robust stateful autoconfiguration and autoregistration of
   DNS Host Names.  Misconfigured (rogue) or malicious DHCP servers can
   be leveraged to attack IPv6 nodes either by denying nodes from
   getting a valid address/prefix or by disseminating incorrect
   information to end nodes for malicious purposes.  Some of these
   scenarios are discussed in [RFC3315]

   The Source Address Validation Improvements (SAVI) group is currently
   working on ways to mitigate the effects of such attacks.
   [I-D.ietf-savi-dhcp] would help in creating bindings between a DHCPv4
   [RFC2131]/DHCPv6 [RFC3315] assigned source IP address and a binding
   anchor [I-D.ietf-savi-framework] on SAVI (Source Address Validation
   Improvements) device.  [RFC6620] describes how to glean similar
   bindings when DHCP is not used.  The bindings can be used to filter
   packets generated on the local link with forged source IP address.

2.2.3.  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

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   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
   mplementation improvements and operational mitigation techniques that
   may be used to mitigate or alleviate the impact of such attacks.

   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
   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-energy-aware-nd]

2.2.4.  ND/RA Filtering

   Router Advertising 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] 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.  This mechanism is commonly employed as a first line of
   defense against common attack vectors.

   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.

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   [I-D.ietf-v6ops-ra-guard-implementation] describes such evasion
   techniques, and provides advice to RA-Guard implementers such that
   the aforementioned evasion vectors can be eliminated.

   [I-D.gont-6man-nd-extension-headers] attempts to analyze the security
   implications of using IPv6 Extension Headers with Neighbor Discovery
   (ND) messages.  The ultimate goal of this doc is to update RFC 4861
   such that use of the IPv6 Fragmentation Header is forbidden in all
   Neighbor Discovery messages, thus allowing for simple and effective
   measures to counter Neighbor Discovery attacks.

2.3.  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
   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

   This section will consider several classes of control packets:

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   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.

2.3.1.  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

   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 which 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.

2.3.2.  Management Protocols

   This class includes: SSH, SNMP, syslog, IPfix, 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

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   configuration obviously depends on the power of the Route Processor.

2.3.3.  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.  See

   On some routers, not everything can be done by the specialized data
   plane hardware.. then some packets are '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.

   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 with 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.

2.4.  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

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2.4.1.  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 passwords,
   which allows routers to authenticate each other prior to establishing
   a routing relationship.  Most open standard protocols, with the
   notable exception of OSPFv3, are able to provide this type of
   authentication mechanism.

   OSPFv3 relies 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
   images (both of which often come with added financial cost) to
   provide such functionality.  [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 authentication key.

2.4.2.  Securing Routing Updates Between Peers

   IPv6 mandates the provisioning of IPSEC capability in all nodes.
   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, most key management mechanisms are designed for a one-
   to-one communication model.  However, in a protocol such as OSPFv3
   where adjacencies are formed on a one-to-many basis, IPSEC key
   management becomes difficult to maintain.

2.4.3.  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.,

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

   o  Discard packets from and to bogon and reserved space

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   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

2.5.  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 [RFC5102]also known as IPfix;

   o  use of SNMP MIB [RFC4293];

   o  use of the Neighbor cache;

   o  use of stateful DHCPv6 [RFC3315] lease cache.

   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 to do:

   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?

   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, ...)

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2.5.1.  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 more details 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 (or filter) in
   order to canonicalize all IPv6 addresses.

   For example, this perl script can be used:
   #!/usr/bin/perl ?w
   use strict ;
   use Socket ;
   use Socket6 ;

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

   ## go through the file one line at a time
   while (my $line = <STDIN>) {
     @words = split /[ \n]/, $line ;
     foreach $word (@words) {
       $binary_address = inet_pton AF_INET6, $word ;
       if ($binary_address) {
         print inet_ntop AF_INET6, $binary_address ;
       } else {
         print $word ;
       print " " ;
     print "\n" ;

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   IPfix [RFC5102] 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

   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 IPv4
   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).

   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.

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   This is an important source of information because it is not trivial
   on a switch using the SAVI [I-D.ietf-savi-framework] algorithm to
   defeat the mapping between data-link layer address and IPv6 address.  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 world 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
   wireless interface while the client actually uses its wired interface
   to connect to the network).

   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.  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
   [I-D.ietf-savi-dhcp] algorithms.  Other Data Sources

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

   o  historical mapping of MAC address to RADIUS user authentication in
      a wireless network or an IPsec-based remote access VPN;

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

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2.5.2.  Use of Collected Data

   This section leverages the data collected as described before
   (Section 2.5.1) in order to achieve several security benefits.  Forensic

   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

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   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.  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 [RFC5102];

   o  change of traffic pattern (number of connection per second, number
      of connection per host...) with the use of IPfix [RFC5102]

2.5.3.  Summary

   While some data sources (IPfix, MIB, switch CAM tables, logs, ...)
   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

   The fact that there are multiple ways to express in a character
   string the same IPv6 address renders the use of filters mandatory

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   when correlation must be done.

2.6.  Transition/Coexistence Technologies

   Some text

2.6.1.  Dual Stack

   Dual stack has established itself as the preferred deployment choice
   for most network operators.  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 2.7

2.6.2.  Tunneling 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

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      clear-text IPv6 packet;

   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

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   IPv4 network.  ISATAP

   ISATAP tunnels [RFC5214] are mainly using 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 [I-D.templin-v6ops-isops].

   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]

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   They suffer from several technical issues as well as security issues
   [RFC3964].  Their use is no more recommended (see
   [I-D.ietf-v6ops-6to4-to-historic]).  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.  DS-Lite

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

   With the tunnel and encapsulation versions of Mapping of Address and
   Port (MAP [I-D.ietf-softwire-map]), the access network is purely an
   IPv6 network and MAP protocols are used to give IPv4 hosts on the
   subscriber network 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 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 [I-D.ietf-softwire-map]; notably, ensuring that the mapping of the
   IPv4 address and port are consistent with the configuration.

2.6.3.  Translation Mechanisms

   Some text  Carrier Grade Nat (CGN)

   Some text

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   Some text  DS-lite

   Some text

2.7.  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

   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

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   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 filtering traffic
   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-Spoof filtering

   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 2.2 be reviewed carefully and the
   recommendations be considered in-depth as well.

   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

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   device hardening guidelines are provided in Section 2.7

   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


4.1.1.  Remote Triggered Black Hole


4.2.  Transition Mechanism

   tbd: will need to reference the security considerations of relevant

4.2.1.  6PE and 6VPE


4.2.2.  6rd

   tbd. refer to 6rd section (Section

4.2.3.  DS-lite


4.3.  Lawful Intercept


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 networks have usually little clue about security or
   networking.  As most of the recent hosts, smartphones, tablets have
   all IPv6 enabled by default, IPv6 security is important for those

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   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.

   If the Residential Gateway has IPv6 connectivity, [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 restauring the end-to-end nature of the
      Internet for the IPv6 traffic but having a different security
      policy for IPv6 than for IPv4.

   [RFC6204] states that a clear choice must be given to the user to
   select one of those two policies.

6.  Acknowledgements

7.  IANA Considerations

   This memo includes no request to IANA.

8.  Security Considerations

   This memo attempts to give an overview of security considerations of
   operating an IPv6 network both in an IPv6-only network but also in a
   dual-stack environment.

9.  References

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9.1.  Normative References

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

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

   [RFC6105]  Levy-Abegnoli, E., Van de Velde, G., Popoviciu, C., and J.
              Mohacsi, "IPv6 Router Advertisement Guard", RFC 6105,
              February 2011.

9.2.  Informative References

              Chakrabarti, S., Nordmark, E., and M. Wasserman, "Energy
              Aware IPv6 Neighbor Discovery Optimizations",
              draft-chakrabarti-nordmark-energy-aware-nd-02 (work in
              progress), March 2012.

              Gont, F., "Security Implications of the Use of IPv6
              Extension Headers with IPv6 Neighbor Discovery",
              draft-gont-6man-nd-extension-headers-03 (work in
              progress), June 2012.

              Bi, J., Wu, J., Yao, G., and F. Baker, "SAVI Solution for
              DHCP", draft-ietf-savi-dhcp-14 (work in progress),
              July 2012.

              Wu, J., Bi, J., Bagnulo, M., Baker, F., and C. Vogt,
              "Source Address Validation Improvement Framework",
              draft-ietf-savi-framework-06 (work in progress),
              January 2012.

              Bush, R. and R. Austein, "The RPKI/Router Protocol",
              draft-ietf-sidr-rpki-rtr-26 (work in progress),
              February 2012.

              Troan, O., Dec, W., Li, X., Bao, C., Zhai, Y., Matsushima,
              S., and T. Murakami, "Mapping of Address and Port (MAP)",
              draft-ietf-softwire-map-01 (work in progress), June 2012.


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              Troan, O., "Request to move Connection of IPv6 Domains via
              IPv4 Clouds (6to4) to Historic status",
              draft-ietf-v6ops-6to4-to-historic-05 (work in progress),
              June 2011.

              Gont, F., "Implementation Advice for IPv6 Router
              Advertisement Guard (RA-Guard)",
              draft-ietf-v6ops-ra-guard-implementation-04 (work in
              progress), May 2012.

              Krishnan, S., "The case against Hop-by-Hop options",
              draft-krishnan-ipv6-hopbyhop-05 (work in progress),
              October 2010.

              Templin, F., "Operational Guidance for IPv6 Deployment in
              IPv4 Sites using ISATAP", draft-templin-v6ops-isops-17
              (work in progress), May 2012.

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

   [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.

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

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

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

   [RFC3022]  Srisuresh, P. and K. Egevang, "Traditional IP Network
              Address Translator (Traditional NAT)", RFC 3022,
              January 2001.

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   [RFC3056]  Carpenter, B. and K. Moore, "Connection of IPv6 Domains
              via IPv4 Clouds", RFC 3056, February 2001.

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

   [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.

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

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

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

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

   [RFC4213]  Nordmark, E. and R. Gilligan, "Basic Transition Mechanisms
              for IPv6 Hosts and Routers", RFC 4213, October 2005.

   [RFC4293]  Routhier, S., "Management Information Base for the
              Internet Protocol (IP)", RFC 4293, April 2006.

   [RFC4301]  Kent, S. and K. Seo, "Security Architecture for the
              Internet Protocol", RFC 4301, December 2005.

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

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

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

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

   [RFC4942]  Davies, E., Krishnan, S., and P. Savola, "IPv6 Transition/

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              Co-existence Security Considerations", RFC 4942,
              September 2007.

   [RFC5102]  Quittek, J., Bryant, S., Claise, B., Aitken, P., and J.
              Meyer, "Information Model for IP Flow Information Export",
              RFC 5102, January 2008.

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

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

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

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

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

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

   [RFC6192]  Dugal, D., Pignataro, C., and R. Dunn, "Protecting the
              Router Control Plane", RFC 6192, March 2011.

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

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

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

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

   [RFC6620]  Nordmark, E., Bagnulo, M., and E. Levy-Abegnoli, "FCFS

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              SAVI: First-Come, First-Served Source Address Validation
              Improvement for Locally Assigned IPv6 Addresses",
              RFC 6620, May 2012.

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

Authors' Addresses

   Kiran Kumar Chittimaneni
   1600 Amphitheater Pkwy
   Mountain View  94043

   Phone: +16502249772
   Email: kk@google.com

   Merike Kaeo
   950 Charter Street
   Redwood City  94063

   Phone: +12066696394
   Email: merike@doubleshotsecurity.com

   Eric Vyncke
   Cisco Systems
   De Kleetlaan 6a
   Diegem  1831

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

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