Internet DRAFT - draft-ietf-opsec-ipv6-eh-filtering

draft-ietf-opsec-ipv6-eh-filtering







opsec                                                            F. Gont
Internet-Draft                                                   EdgeUno
Intended status: Informational                                    W. Liu
Expires: 4 November 2022                             Huawei Technologies
                                                              3 May 2022


    Recommendations on the Filtering of IPv6 Packets Containing IPv6
                  Extension Headers at Transit Routers
                 draft-ietf-opsec-ipv6-eh-filtering-10

Abstract

   This document analyzes the security implications of IPv6 Extension
   Headers and associated IPv6 options.  Additionally, it discusses the
   operational and interoperability implications of discarding packets
   based on the IPv6 Extension Headers and IPv6 options they contain.
   Finally, it provides advice on the filtering of such IPv6 packets at
   transit routers for traffic not directed to them, for those cases
   where such filtering is deemed as necessary.

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 https://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 4 November 2022.

Copyright Notice

   Copyright (c) 2022 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 (https://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



Gont & Liu               Expires 4 November 2022                [Page 1]

Internet-Draft     Filtering of IPv6 packets with EHs           May 2022


   extracted from this document must include Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology and Assumptions Employed in This Document . . . .   4
     2.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   4
     2.2.  Applicability Statement . . . . . . . . . . . . . . . . .   4
     2.3.  Router Default Behavior and Features  . . . . . . . . . .   4
   3.  IPv6 Extension Headers  . . . . . . . . . . . . . . . . . . .   5
     3.1.  General Discussion  . . . . . . . . . . . . . . . . . . .   5
     3.2.  General Security Implications . . . . . . . . . . . . . .   6
     3.3.  Rationale for Our Advice on the Handling of IPv6 Packets
           with Specific IPv6 Extension Headers  . . . . . . . . . .   6
     3.4.  Summary of Advice on the Handling of IPv6 Packets with
           Specific IPv6 Extension Headers . . . . . . . . . . . . .   6
     3.5.  Advice on the Handling of IPv6 Packets with Specific IPv6
           Extension Headers . . . . . . . . . . . . . . . . . . . .   7
     3.6.  Advice on the Handling of Packets with Unknown IPv6
           Extension Headers . . . . . . . . . . . . . . . . . . . .  16
   4.  IPv6 Options  . . . . . . . . . . . . . . . . . . . . . . . .  17
     4.1.  General Discussion  . . . . . . . . . . . . . . . . . . .  17
     4.2.  General Security Implications of IPv6 Options . . . . . .  17
     4.3.  Summary of Advice on the Handling of IPv6 Packets with
           Specific IPv6 Extension Headers . . . . . . . . . . . . .  18
     4.4.  Advice on the Handling of Packets with Specific IPv6
           Options . . . . . . . . . . . . . . . . . . . . . . . . .  19
     4.5.  Advice on the handling of Packets with Unknown IPv6
           Options . . . . . . . . . . . . . . . . . . . . . . . . .  32
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  32
   6.  Privacy Considerations  . . . . . . . . . . . . . . . . . . .  32
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  32
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  33
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  33
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  33
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  37
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  39

1.  Introduction

   IPv6 Extension Headers (EHs) allow for the extension of the IPv6
   protocol, and provide support for core functionality such as IPv6
   fragmentation.  However, common implementation limitations suggest
   that EHs present a challenge for IPv6 packet routing equipment,
   particularly when the IPv6 header chain needs to be processed for
   e.g. enforcing ACLs or implementing other functions [RFC9098].



Gont & Liu               Expires 4 November 2022                [Page 2]

Internet-Draft     Filtering of IPv6 packets with EHs           May 2022


   Several studies (e.g.  [Huston-2022], [I-D.vyncke-v6ops-james], and
   [RFC7872]) suggest that there is widespread dropping of IPv6 packets
   that contain IPv6 Extension Headers (EHs).  In some cases, such
   packet drops occur at transit routers.  While some operators are
   known to intentionally drop packets that contain IPv6 EHs, it is
   possible that some of the measured packet drops are the result of
   inappropriate advice in this area.

   This document analyzes both the general security implications of IPv6
   EHs, as well as the security implications of specific EH and Option
   types.  It also provides advice on the filtering of IPv6 packets
   based on the IPv6 EHs and the IPv6 options they contain.  Since
   various protocols may use IPv6 EHs (possibly with IPv6 options),
   discarding packets based on the IPv6 EHs or IPv6 options they contain
   can have implications on the proper functioning of such protocols.
   Thus, this document also attempts to discuss the operational and
   interoperability implications of such filtering policies.

   The resulting packet filtering policy typically depends on where in
   the network such policy is enforced: when the policy is enforced in a
   transit network, the policy typically follows a "deny-list" approach,
   where only packets with clear negative implications are dropped.  On
   the other hand, when the policy is enforced closer to the destination
   systems, the policy typically follows an "accept-list" approach,
   where only traffic that is expected to be received is allowed.  The
   advice in this document is aimed only at transit routers that may
   need to enforce a filtering policy based on the EHs and IPv6 options
   a packet may contain, following a "deny-list" approach, and hence is
   likely to be much more permissive than a filtering policy to be
   employed at e.g. the edge of an enterprise network.  The advice in
   this document is meant to improve the current situation of the
   dropping of packets with IPv6 EHs in the Internet [RFC7872] in such
   cases where packets are being dropped due to inappropriate or missing
   guidelines.

   This document is similar in nature to [RFC7126], which addresses the
   same problem for the IPv4 case.  However, in IPv6, the problem space
   is compounded by the fact that IPv6 specifies a number of IPv6 EHs,
   and a number of IPv6 options which may be valid only when included in
   specific EH types.

   This document completes and complements the considerations for
   protecting the control plane from packets containing IP options that
   can be found in [RFC6192].







Gont & Liu               Expires 4 November 2022                [Page 3]

Internet-Draft     Filtering of IPv6 packets with EHs           May 2022


   Section 2 specifies the terminology and conventions employed
   throughout this document.  Section 3 discusses IPv6 EHs and provides
   advice in the area of filtering IPv6 packets that contain such IPv6
   EHs.  Section 4 discusses IPv6 options and provides advice in the
   area of filtering IPv6 packets that contain such options.

2.  Terminology and Assumptions Employed in This Document

2.1.  Terminology

   The terms "permit" (allow the traffic), "drop" (drop with no
   notification to sender), and "reject" (drop with appropriate
   notification to sender) are employed as defined in [RFC3871].
   Throughout this document we also employ the term "discard" as a
   generic term to indicate the act of discarding a packet, irrespective
   of whether the sender is notified of such drops, and irrespective of
   whether the specific filtering action is logged.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

2.2.  Applicability Statement

   This document provides advice on the filtering of IPv6 packets with
   EHs at transit routers for traffic not explicitly destined to them,
   for cases in which such filtering is deemed as necessary.

2.3.  Router Default Behavior and Features

   This document assumes that nodes comply with the requirements in
   [RFC7045].  Namely,

      "If a forwarding node discards a packet containing a standard IPv6
      extension header, it MUST be the result of a configurable policy
      and not just the result of a failure to recognise such a header.
      This means that the discard policy for each standard type of
      extension header MUST be individually configurable.  The default
      configuration SHOULD allow all standard extension headers."

   The advice provided in this document is only meant to guide an
   operator in configuring forwarding devices, and is not to be
   interpreted as advice regarding default configuration settings for
   network devices.  That is, this document provides advice with respect
   to operational policies, but does not change the implementation
   defaults required by [RFC7045].



Gont & Liu               Expires 4 November 2022                [Page 4]

Internet-Draft     Filtering of IPv6 packets with EHs           May 2022


   We recommend that configuration options are made available to govern
   the processing of each IPv6 EH type and each IPv6 option type.  Such
   configuration options should include the following possible settings:

   *  Permit this IPv6 EH or IPv6 Option type.

   *  Drop packets containing this IPv6 EH or option type.

   *  Reject packets containing this IPv6 EH or option type (where the
      packet drop is signaled with an ICMPv6 error message).

   *  Rate-limit traffic containing this IPv6 EH or option type.

   *  Ignore this IPv6 EH or option type (as if it was not present) and
      process the packet according the rules for the remaining headers.
      We note that if a packet carries forwarding information (e.g., in
      an IPv6 Routing Header) this might be an inappropriate or
      undesirable action.

   We note that special care needs to be taken when devices log packet
   drops/rejects.  Devices should count the number of packets dropped/
   rejected, but the logging of drop/reject events should be limited so
   as to not overburden device resources.

   Finally, we note that when discarding packets, it is generally
   desirable that the sender be signaled of the packet drop, since this
   is of use for trouble-shooting purposes.  However, throughout this
   document (when recommending that packets be discarded) we generically
   refer to the action as "discard" without specifying whether the
   sender is signaled of the packet drop.

3.  IPv6 Extension Headers

3.1.  General Discussion

   IPv6 [RFC8200] EHs allow for the extension of the IPv6 protocol.
   Since both IPv6 EHs and upper-layer protocols share the same
   namespace ("Next Header" registry/namespace), [RFC7045] identifies
   which of the currently assigned Internet Protocol numbers identify
   IPv6 EHs vs. upper-layer protocols.  This document discusses the
   filtering of packets based on the IPv6 EHs (as specified by
   [RFC7045]) they contain.

      NOTE: [RFC8200] specifies that non-fragmented IPv6 datagrams and
      IPv6 First-Fragments must contain the entire IPv6 header chain
      [RFC7112].  Therefore, intermediate systems can enforce the
      filtering policies discussed in this document, or resort to simply
      discarding the offending packets when they fail to comply with the



Gont & Liu               Expires 4 November 2022                [Page 5]

Internet-Draft     Filtering of IPv6 packets with EHs           May 2022


      requirements in [RFC8200].  We note that, in order to implement
      filtering rules on the fast path, it may be necessary for the
      filtering device to limit the depth into the packet that can be
      inspected before giving up.  In circumstances where such a
      limitation exists, it is recommended that implementations provide
      a configuration option that specifies whether to discard packets
      if the aforementioned limit is encountered.  Operators may then
      determine according to their own circumstances how such packets
      will be handled.

3.2.  General Security Implications

   In some device architectures, IPv6 packets that contain IPv6 EHs can
   cause the corresponding packets to be processed on the slow path, and
   hence may be leveraged for the purpose of Denial of Service (DoS)
   attacks [RFC9098] [Cisco-EH] [FW-Benchmark].

   Operators are urged to consider the IPv6 EH and IPv6 options handling
   capabilities of their devices as they make deployment decisions in
   the future.

3.3.  Rationale for Our Advice on the Handling of IPv6 Packets with
      Specific IPv6 Extension Headers

   *  IPv6 Packets with IPv6 Extension Headers (or options) that are not
      expected to traverse transit routers should be dropped.

   *  IPv6 Packets with IPv6 Extension Headers (or options) that are
      only expected to traverse transit routers when a specific
      technology is employed, should be permitted (or dropped) based on
      the knowledge regarding the use of such technology in transit
      provider in question (i.e. permit the packets if the technology is
      employed, or drop them)

   *  IPv6 Packets with IPv6 Extension Headers (or options) that
      represent a concrete attack vector to network infrastructure
      devices should be dropped.

   *  IPv6 packets with any other IPv6 Extension headers (or options)
      should be permitted.  This is an intentional trade-off made to
      minimize ossification.

3.4.  Summary of Advice on the Handling of IPv6 Packets with Specific
      IPv6 Extension Headers

   This section summarizes the advice provided in Section 3.5, providing
   references to the specific sections in which a detailed analysis can
   be found.



Gont & Liu               Expires 4 November 2022                [Page 6]

Internet-Draft     Filtering of IPv6 packets with EHs           May 2022


    +=========================+==========================+===========+
    |         EH type         |     Filtering policy     | Reference |
    +=========================+==========================+===========+
    | IPv6 Hop-by-Hop Options |      Drop or Ignore      |  Section  |
    |        (Proto=0)        |                          |   3.5.1   |
    +-------------------------+--------------------------+-----------+
    | Routing Header for IPv6 | Drop only RHT0 and RHT1. |  Section  |
    |        (Proto=43)       |  Permit other RH Types   |   3.5.2   |
    +-------------------------+--------------------------+-----------+
    |   Fragment Header for   |          Permit          |  Section  |
    |     IPv6 (Proto=44)     |                          |   3.5.3   |
    +-------------------------+--------------------------+-----------+
    |  Encapsulating Security |          Permit          |  Section  |
    |    Payload (Proto=50)   |                          |   3.5.4   |
    +-------------------------+--------------------------+-----------+
    |  Authentication Header  |          Permit          |  Section  |
    |        (Proto=51)       |                          |   3.5.5   |
    +-------------------------+--------------------------+-----------+
    | Destination Options for |          Permit          |  Section  |
    |     IPv6 (Proto=60)     |                          |   3.5.6   |
    +-------------------------+--------------------------+-----------+
    |     Mobility Header     |          Permit          |  Section  |
    |       (Proto=135)       |                          |   3.5.7   |
    +-------------------------+--------------------------+-----------+
    |  Host Identity Protocol |          Permit          |  Section  |
    |       (Proto=139)       |                          |   3.5.8   |
    +-------------------------+--------------------------+-----------+
    |      Shim6 Protocol     |          Permit          |  Section  |
    |       (Proto=140)       |                          |   3.5.9   |
    +-------------------------+--------------------------+-----------+
    | Use for experimentation |           Drop           |  Section  |
    |  and testing (Proto=253 |                          |   3.5.10  |
    |         and 254)        |                          |           |
    +-------------------------+--------------------------+-----------+

        Table 1: Summary of Advice on the Handling of IPv6 Packets
                   with Specific IPv6 Extension Headers

3.5.  Advice on the Handling of IPv6 Packets with Specific IPv6
      Extension Headers

3.5.1.  IPv6 Hop-by-Hop Options (Protocol Number=0)









Gont & Liu               Expires 4 November 2022                [Page 7]

Internet-Draft     Filtering of IPv6 packets with EHs           May 2022


3.5.1.1.  Uses

   The Hop-by-Hop Options header is used to carry optional information
   that may be examined by every node along a packet's delivery path.
   It is expected that nodes will examine the Hop-by-Hop Options header
   if explicitly configured to do so.

   NOTE: A previous revision of the IPv6 core specification, [RFC2460],
   originally required that all nodes examined and processed the Hop-by-
   Hop Options header.  However, even before the publication of
   [RFC8200] a number of implementations already provided the option of
   ignoring this header unless explicitly configured to examine it.

3.5.1.2.  Specification

   This EH is specified in [RFC8200].  As of May 2022, the following
   options have been specified for the Hop-by-Hop Options EH:

   *  Type 0x00: Pad1 [RFC8200]

   *  Type 0x01: PadN [RFC8200]

   *  Type 0x05: Router Alert [RFC2711]

   *  Type 0x07: CALIPSO [RFC5570]

   *  Type 0x08: SMF_DPD [RFC6621]

   *  Type 0x23: RPL Option [RFC9008]

   *  Type 0x26: Quick-Start [RFC4782]

   *  Type 0x4D: (Deprecated)

   *  Type 0x63: RPL Option [RFC6553]

   *  Type 0x6D: MPL Option [RFC7731]

   *  Type 0x8A: Endpoint Identification (Deprecated)
      [draft-ietf-nimrod-eid]

   *  Type 0xC2: Jumbo Payload [RFC2675]

   *  Type 0xEE: IPv6 DFF Header [RFC6971]

   *  Type 0x1E: RFC3692-style Experiment [RFC4727]

   *  Type 0x3E: RFC3692-style Experiment [RFC4727]



Gont & Liu               Expires 4 November 2022                [Page 8]

Internet-Draft     Filtering of IPv6 packets with EHs           May 2022


   *  Type 0x5E: RFC3692-style Experiment [RFC4727]

   *  Type 0x7E: RFC3692-style Experiment [RFC4727]

   *  Type 0x9E: RFC3692-style Experiment [RFC4727]

   *  Type 0xBE: RFC3692-style Experiment [RFC4727]

   *  Type 0xDE: RFC3692-style Experiment [RFC4727]

   *  Type 0xFE: RFC3692-style Experiment [RFC4727]

3.5.1.3.  Specific Security Implications

   Legacy nodes that process this extension header might be subject to
   Denial of Service attacks.

   NOTE: While [RFC8200] has removed this requirement, the deployed base
   may still reflect the classical behavior for a while, and hence the
   potential security problems of this EH are still of concern.

3.5.1.4.  Operational and Interoperability Impact if Blocked

   Discarding packets containing a Hop-by-Hop Options EH would break any
   of the protocols that rely on it for proper functioning.  For
   example, it would break RSVP [RFC2205] and multicast deployments, and
   would cause IPv6 jumbograms to be discarded.

3.5.1.5.  Advice

   Nodes implementing [RFC8200] would already ignore this extension
   header unless explicitly required to process it.  For legacy
   ([RFC2460]) nodes, the recommended configuration for the processing
   of these packets depends on the features and capabilities of the
   underlying platform, the configuration of the platform, and also the
   deployment environment of the platform.  On platforms that allow
   forwarding of packets with HBH Options on the fast path, we recommend
   that packets with a HBH Options EH be forwarded as normal.
   Otherwise, on platforms in which processing of packets with a IPv6
   HBH Options EH is carried out in the slow path, and an option is
   provided to rate-limit these packets, we recommend that this option
   be selected.  Finally, when packets containing a HBH Options EH are
   processed in the slow-path, and the underlying platform does not have
   any mitigation options available for attacks based on these packets,
   we recommend that such platforms discard packets containing IPv6 HBH
   Options EHs.





Gont & Liu               Expires 4 November 2022                [Page 9]

Internet-Draft     Filtering of IPv6 packets with EHs           May 2022


   Finally, we note that RPL (Routing Protocol for Low-Power and Lossy
   Networks) routers [RFC6550] must not discard packets based on the
   presence of an IPv6 Hop-by-Hop Options EH, as this would break RPL.

3.5.2.  Routing Header for IPv6 (Protocol Number=43)

3.5.2.1.  Uses

   The Routing header is used by an IPv6 source to list one or more
   intermediate nodes to be "visited" on the way to a packet's
   destination.

3.5.2.2.  Specification

   This EH is specified in [RFC8200].  [RFC2460] had originally
   specified the Routing Header Type 0, which was later obsoleted by
   [RFC5095], and thus removed from [RFC8200].

   At of May 2022, the following Routing Types have been specified:

   *  Type 0: Source Route (DEPRECATED) [RFC2460] [RFC5095]

   *  Type 1: Nimrod (DEPRECATED)

   *  Type 2: Type 2 Routing Header [RFC6275]

   *  Type 3: RPL Source Route Header [RFC6554]

   *  Type 4: Segment Routing Header (SRH) [RFC8754]

   *  Types 5-252: Unassigned

   *  Type 253: RFC3692-style Experiment 1 [RFC4727]

   *  Type 254: RFC3692-style Experiment 2 [RFC4727]

   *  Type 255: Reserved

3.5.2.3.  Specific Security Implications

   The security implications of RHT0 have been discussed in detail in
   [Biondi2007] and [RFC5095].  RHT1 was never widely implemented.  The
   security implications of RHT2, RHT3, and RHT4 (SRH) are discussed in
   [RFC6275], [RFC6554], and [RFC8754], respectively.







Gont & Liu               Expires 4 November 2022               [Page 10]

Internet-Draft     Filtering of IPv6 packets with EHs           May 2022


3.5.2.4.  Operational and Interoperability Impact if Blocked

   Blocking packets containing a RHT0 or RHT1 has no operational
   implications, since both have been deprecated.  Blocking packets with
   a RHT2 would break Mobile IPv6.  Packets with a RHT3 may be safely
   blocked at RPL domain boundaries, since RHT3 headers are employed
   within a single RPL domain.  Blocking packets with a RHT4 (SRH) will
   break Segment Routing (SR) deployments, if the filtering policy is
   enforced on packets being forwarded within an SR domain.

3.5.2.5.  Advice

   Intermediate systems should discard packets containing a RHT0, RHT1,
   or RHT3.  Other routing header types should be permitted, as required
   by [RFC7045].

3.5.3.  Fragment Header for IPv6 (Protocol Number=44)

3.5.3.1.  Uses

   This EH provides the fragmentation functionality for IPv6.

3.5.3.2.  Specification

   This EH is specified in [RFC8200].

3.5.3.3.  Specific Security Implications

   The security implications of the Fragment Header range from Denial of
   Service attacks (e.g. based on flooding a target with IPv6 fragments)
   to information leakage attacks [RFC7739].

3.5.3.4.  Operational and Interoperability Impact if Blocked

   Blocking packets that contain a Fragment Header will break any
   protocol that may rely on fragmentation (e.g., the DNS [RFC1034]).
   However, IP fragmentation is known to introduce fragility to Internet
   communication [RFC8900].

3.5.3.5.  Advice

   Intermediate systems should permit packets that contain a Fragment
   Header.

3.5.4.  Encapsulating Security Payload (Protocol Number=50)






Gont & Liu               Expires 4 November 2022               [Page 11]

Internet-Draft     Filtering of IPv6 packets with EHs           May 2022


3.5.4.1.  Uses

   This EH is employed for the IPsec suite [RFC4303].

3.5.4.2.  Specification

   This EH is specified in [RFC4303].

3.5.4.3.  Specific Security Implications

   Besides the general implications of IPv6 EHs, this EH could be
   employed to potentially perform a DoS attack at the destination
   system by wasting CPU resources in validating the contents of the
   packet.

3.5.4.4.  Operational and Interoperability Impact if Blocked

   Discarding packets that employ this EH would break IPsec deployments.

3.5.4.5.  Advice

   Intermediate systems should permit packets containing the
   Encapsulating Security Payload EH.

3.5.5.  Authentication Header (Protocol Number=51)

3.5.5.1.  Uses

   The Authentication Header can be employed for provide authentication
   services in IPv4 and IPv6.

3.5.5.2.  Specification

   This EH is specified in [RFC4302].

3.5.5.3.  Specific Security Implications

   Besides the general implications of IPv6 EHs, this EH could be
   employed to potentially perform a DoS attack at the destination
   system by wasting CPU resources in validating the contents of the
   packet.

3.5.5.4.  Operational and Interoperability Impact if Blocked

   Discarding packets that employ this EH would break IPsec deployments.






Gont & Liu               Expires 4 November 2022               [Page 12]

Internet-Draft     Filtering of IPv6 packets with EHs           May 2022


3.5.5.5.  Advice

   Intermediate systems should permit packets containing an
   Authentication Header.

3.5.6.  Destination Options for IPv6 (Protocol Number=60)

3.5.6.1.  Uses

   The Destination Options header is used to carry optional information
   that needs be examined only by a packet's destination node(s).

3.5.6.2.  Specification

   This EH is specified in [RFC8200].  As of May 2022, the following
   options have been specified for this EH:

   *  Type 0x00: Pad1 [RFC8200]

   *  Type 0x01: PadN [RFC8200]

   *  Type 0x04: Tunnel Encapsulation Limit [RFC2473]

   *  Type 0x0F: IPv6 Performance and Diagnostic Metrics (PDM) [RFC8250]

   *  Type 0x4D: (Deprecated)

   *  Type 0xC9: Home Address [RFC6275]

   *  Type 0x8A: Endpoint Identification (Deprecated)
      [draft-ietf-nimrod-eid]

   *  Type 0x8B: ILNP Nonce [RFC6744]

   *  Type 0x8C: Line-Identification Option [RFC6788]

   *  Type 0x1E: RFC3692-style Experiment [RFC4727]

   *  Type 0x3E: RFC3692-style Experiment [RFC4727]

   *  Type 0x5E: RFC3692-style Experiment [RFC4727]

   *  Type 0x7E: RFC3692-style Experiment [RFC4727]

   *  Type 0x9E: RFC3692-style Experiment [RFC4727]

   *  Type 0xBE: RFC3692-style Experiment [RFC4727]




Gont & Liu               Expires 4 November 2022               [Page 13]

Internet-Draft     Filtering of IPv6 packets with EHs           May 2022


   *  Type 0xDE: RFC3692-style Experiment [RFC4727]

   *  Type 0xFE: RFC3692-style Experiment [RFC4727]

3.5.6.3.  Specific Security Implications

   No security implications are known, other than the general
   implications of IPv6 EHs.  For a discussion of possible security
   implications of specific options specified for the DO header, please
   see the Section 4.4.

3.5.6.4.  Operational and Interoperability Impact if Blocked

   Discarding packets that contain a Destination Options header would
   break protocols that rely on this EH type for conveying information,
   including protocols such as ILNP [RFC6740] and Mobile IPv6 [RFC6275],
   and IPv6 tunnels that employ the Tunnel Encapsulation Limit option.

3.5.6.5.  Advice

   Intermediate systems should permit packets that contain a Destination
   Options Header.

3.5.7.  Mobility Header (Protocol Number=135)

3.5.7.1.  Uses

   The Mobility Header is an EH used by mobile nodes, correspondent
   nodes, and home agents in all messaging related to the creation and
   management of bindings in Mobile IPv6.

3.5.7.2.  Specification

   This EH is specified in [RFC6275].

3.5.7.3.  Specific Security Implications

   A thorough security assessment of the security implications of the
   Mobility Header and related mechanisms can be found in Section 15 of
   [RFC6275].

3.5.7.4.  Operational and Interoperability Impact if Blocked

   Discarding packets containing this EH would break Mobile IPv6.







Gont & Liu               Expires 4 November 2022               [Page 14]

Internet-Draft     Filtering of IPv6 packets with EHs           May 2022


3.5.7.5.  Advice

   Intermediate systems should permit packets containing this EH.

3.5.8.  Host Identity Protocol (Protocol Number=139)

3.5.8.1.  Uses

   This EH is employed with the Host Identity Protocol (HIP), a protocol
   that allows consenting hosts to securely establish and maintain
   shared IP-layer state, allowing separation of the identifier and
   locator roles of IP addresses, thereby enabling continuity of
   communications across IP address changes.

3.5.8.2.  Specification

   This EH is specified in [RFC7401].

3.5.8.3.  Specific Security Implications

   The security implications of the HIP header are discussed in detail
   in Section 8 of [RFC6275].

3.5.8.4.  Operational and Interoperability Impact if Blocked

   Discarding packets that contain the Host Identity Protocol would
   break HIP deployments.

3.5.8.5.  Advice

   Intermediate systems should permit packets that contain a Host
   Identity Protocol EH.

3.5.9.  Shim6 Protocol (Protocol Number=140)

3.5.9.1.  Uses

   This EH is employed by the Shim6 [RFC5533] Protocol.

3.5.9.2.  Specification

   This EH is specified in [RFC5533].

3.5.9.3.  Specific Security Implications

   The specific security implications are discussed in detail in
   Section 16 of [RFC5533].




Gont & Liu               Expires 4 November 2022               [Page 15]

Internet-Draft     Filtering of IPv6 packets with EHs           May 2022


3.5.9.4.  Operational and Interoperability Impact if Blocked

   Discarding packets that contain this EH will break Shim6.

3.5.9.5.  Advice

   Intermediate systems should permit packets containing this EH.

3.5.10.  Use for experimentation and testing (Protocol Numbers=253 and
         254)

3.5.10.1.  Uses

   These IPv6 EHs are employed for performing RFC3692-Style experiments
   (see [RFC3692] for details).

3.5.10.2.  Specification

   These EHs are specified in [RFC3692] and [RFC4727].

3.5.10.3.  Specific Security Implications

   The security implications of these EHs will depend on their specific
   use.

3.5.10.4.  Operational and Interoperability Impact if Blocked

   For obvious reasons, discarding packets that contain these EHs limits
   the ability to perform legitimate experiments across IPv6 routers.

3.5.10.5.  Advice

   Operators should determine according to their own circumstances
   whether to discard packets containing these EHs.

3.6.  Advice on the Handling of Packets with Unknown IPv6 Extension
      Headers

   We refer to IPv6 EHs that have not been assigned an Internet Protocol
   Number by IANA (and marked as such) in [IANA-PROTOCOLS] as "unknown
   IPv6 extension headers" ("unknown IPv6 EHs").

3.6.1.  Uses

   New IPv6 EHs may be specified as part of future extensions to the
   IPv6 protocol.





Gont & Liu               Expires 4 November 2022               [Page 16]

Internet-Draft     Filtering of IPv6 packets with EHs           May 2022


   Since IPv6 EHs and Upper-layer protocols employ the same namespace,
   it is impossible to tell whether an unknown "Internet Protocol
   Number" is being employed for an IPv6 EH or an Upper-Layer protocol.

3.6.2.  Specification

   The processing of unknown IPv6 EHs is specified in [RFC7045].

3.6.3.  Specific Security Implications

   For obvious reasons, it is impossible to determine specific security
   implications of unknown IPv6 EHs.

3.6.4.  Operational and Interoperability Impact if Blocked

   As noted in [RFC7045], discarding unknown IPv6 EHs may slow down the
   deployment of new IPv6 EHs and transport protocols.  The
   corresponding IANA registry ([IANA-PROTOCOLS]) should be monitored
   such that filtering rules are updated as new IPv6 EHs are
   standardized.

   We note that since IPv6 EHs and upper-layer protocols share the same
   numbering space, discarding unknown IPv6 EHs may result in packets
   encapsulating unknown upper-layer protocols being discarded.

3.6.5.  Advice

   Operators should determine according to their own circumstances
   whether to discard packets containing unknown IPv6 EHs.

4.  IPv6 Options

4.1.  General Discussion

   The following subsections describe specific security implications of
   different IPv6 options, and provide advice regarding filtering
   packets that contain such options.

4.2.  General Security Implications of IPv6 Options

   The general security implications of IPv6 options are closely related
   to those discussed in Section 3.2 for IPv6 EHs.  Essentially, packets
   that contain IPv6 options might need to be processed by an IPv6
   router's general-purpose CPU,and hence could present a DDoS risk to
   that router's general-purpose CPU (and thus to the router itself).
   For some architectures, a possible mitigation would be to rate-limit
   the packets that are to be processed by the general-purpose CPU (see
   e.g.  [Cisco-EH]).



Gont & Liu               Expires 4 November 2022               [Page 17]

Internet-Draft     Filtering of IPv6 packets with EHs           May 2022


4.3.  Summary of Advice on the Handling of IPv6 Packets with Specific
      IPv6 Extension Headers

   This section summarizes the advice provided in Section 3.5, providing
   references to the specific sections in which a detailed analysis can
   be found.

   +===============================+======================+===========+
   |             Option            |   Filtering policy   | Reference |
   +===============================+======================+===========+
   |        Pad1 (Type=0x00)       |        Permit        |  Section  |
   |                               |                      |   4.4.1   |
   +-------------------------------+----------------------+-----------+
   |        PadN (Type=0x01)       |        Permit        |  Section  |
   |                               |                      |   4.4.2   |
   +-------------------------------+----------------------+-----------+
   |   Tunnel Encapsulation Limit  |        Permit        |  Section  |
   |          (Type=0x04)          |                      |   4.4.3   |
   +-------------------------------+----------------------+-----------+
   |    Router Alert (Type=0x05)   |   Permit based on    |  Section  |
   |                               | needed functionality |   4.4.4   |
   +-------------------------------+----------------------+-----------+
   |      CALIPSO (Type=0x07)      |   Permit based on    |  Section  |
   |                               | needed functionality |   4.4.5   |
   +-------------------------------+----------------------+-----------+
   |      SMF_DPD (Type=0x08)      |   Permit based on    |  Section  |
   |                               | needed functionality |   4.4.6   |
   +-------------------------------+----------------------+-----------+
   |     PDM Option (Type=0x0F)    |        Permit        |  Section  |
   |                               |                      |   4.4.7   |
   +-------------------------------+----------------------+-----------+
   |     RPL Option (Type=0x23)    |        Permit        |  Section  |
   |                               |                      |   4.4.8   |
   +-------------------------------+----------------------+-----------+
   |    Quick-Start (Type=0x26)    |        Permit        |  Section  |
   |                               |                      |   4.4.9   |
   +-------------------------------+----------------------+-----------+
   |     Deprecated (Type=0x4D)    |         Drop         |  Section  |
   |                               |                      |   4.4.10  |
   +-------------------------------+----------------------+-----------+
   |     MPL Option (Type=0x6D)    |        Permit        |  Section  |
   |                               |                      |   4.4.12  |
   +-------------------------------+----------------------+-----------+
   |    Jumbo Payload (Type=0C2)   |   Permit based on    |  Section  |
   |                               | needed functionality |   4.4.16  |
   +-------------------------------+----------------------+-----------+
   |     RPL Option (Type=0x63)    |   Drop in non-RPL    |  Section  |
   |                               |       routers        |   4.4.11  |



Gont & Liu               Expires 4 November 2022               [Page 18]

Internet-Draft     Filtering of IPv6 packets with EHs           May 2022


   +-------------------------------+----------------------+-----------+
   |    Endpoint Identification    |         Drop         |  Section  |
   |          (Type=0x8A)          |                      |   4.4.13  |
   +-------------------------------+----------------------+-----------+
   |     ILNP Nonce (Type=0x8B)    |        Permit        |  Section  |
   |                               |                      |   4.4.14  |
   +-------------------------------+----------------------+-----------+
   |   Line-Identification Option  |         Drop         |  Section  |
   |          (Type=0x8C)          |                      |   4.4.15  |
   +-------------------------------+----------------------+-----------+
   |    Home Address (Type=0xC9)   |        Permit        |  Section  |
   |                               |                      |   4.4.17  |
   +-------------------------------+----------------------+-----------+
   |       IP_DFF (Type=0xEE)      |   Permit based on    |  Section  |
   |                               | needed functionality |   4.4.18  |
   +-------------------------------+----------------------+-----------+
   |    RFC3692-style Experiment   |   Permit based on    |  Section  |
   |   (Types = 0x1E, 0x3E, 0x5E,  | needed functionality |   4.4.19  |
   | 0x7E, 0x9E, 0xBE, 0xDE, 0xFE) |                      |           |
   +-------------------------------+----------------------+-----------+

     Table 2: Summary of Advice on the Handling of IPv6 Packets with
                          Specific IPv6 options

4.4.  Advice on the Handling of Packets with Specific IPv6 Options

   The following subsections contain a description of each of the IPv6
   options that have so far been specified, a summary of the security
   implications of each of such options, a discussion of possible
   interoperability implications if packets containing such options are
   discarded, and specific advice regarding whether packets containing
   these options should be permitted.

4.4.1.  Pad1 (Type=0x00)

4.4.1.1.  Uses

   This option is used when necessary to align subsequent options and to
   pad out the containing header to a multiple of 8 octets in length.

4.4.1.2.  Specification

   This option is specified in [RFC8200].

4.4.1.3.  Specific Security Implications

   None.




Gont & Liu               Expires 4 November 2022               [Page 19]

Internet-Draft     Filtering of IPv6 packets with EHs           May 2022


4.4.1.4.  Operational and Interoperability Impact if Blocked

   Discarding packets that contain this option would potentially break
   any protocol that relies on IPv6 options.

4.4.1.5.  Advice

   Intermediate systems should not discard packets based on the presence
   of this option.

4.4.2.  PadN (Type=0x01)

4.4.2.1.  Uses

   This option is used when necessary to align subsequent options and to
   pad out the containing header to a multiple of 8 octets in length.

4.4.2.2.  Specification

   This option is specified in [RFC8200].

4.4.2.3.  Specific Security Implications

   Because of the possible size of this option, it could be leveraged as
   a large-bandwidth covert channel.

4.4.2.4.  Operational and Interoperability Impact if Blocked

   Discarding packets that contain this option would potentially break
   any protocol that relies on IPv6 options.

4.4.2.5.  Advice

   Intermediate systems should not discard IPv6 packets based on the
   presence of this option.

4.4.3.  Tunnel Encapsulation Limit (Type=0x04)

4.4.3.1.  Uses

   The Tunnel Encapsulation Limit option can be employed to specify how
   many further levels of nesting the packet is permitted to undergo.

4.4.3.2.  Specification

   This option is specified in [RFC2473].





Gont & Liu               Expires 4 November 2022               [Page 20]

Internet-Draft     Filtering of IPv6 packets with EHs           May 2022


4.4.3.3.  Specific Security Implications

   Those described in [RFC2473].

4.4.3.4.  Operational and Interoperability Impact if Blocked

   Discarding packets based on the presence of this option could result
   in tunnel traffic being discarded.

4.4.3.5.  Advice

   Intermediate systems should not discard packets based on the presence
   of this option.

4.4.4.  Router Alert (Type=0x05)

4.4.4.1.  Uses

   The Router Alert option [RFC2711] is employed by a number of
   protocols, including the Resource reSerVation Protocol (RSVP)
   [RFC2205], Multicast Listener Discovery (MLD) [RFC2710] [RFC3810],
   Multicast Router Discovery (MRD) [RFC4286], and General Internet
   Signaling Transport (GIST) [RFC5971].  Its usage is discussed in
   detail in [RFC6398].

4.4.4.2.  Specification

   This option is specified in [RFC2711].

4.4.4.3.  Specific Security Implications

   Since this option causes the contents of the packet to be inspected
   by the handling device, this option could be leveraged for performing
   DoS attacks.  The security implications of the Router Alert option
   are discussed in detail in [RFC6398].

4.4.4.4.  Operational and Interoperability Impact if Blocked

   Discarding packets that contain this option would break any protocols
   that rely on them, such as RSVP and multicast deployments.  Please
   see Section 4.4.4.3 for further details.

4.4.4.5.  Advice

   Packets containing this option should be permitted in environments
   where support for RSVP, multicast routing, or similar protocols is
   desired.




Gont & Liu               Expires 4 November 2022               [Page 21]

Internet-Draft     Filtering of IPv6 packets with EHs           May 2022


4.4.5.  CALIPSO (Type=0x07)

4.4.5.1.  Uses

   This option is used for encoding explicit packet Sensitivity Labels
   on IPv6 packets.  It is intended for use only within Multi-Level
   Secure (MLS) networking environments that are both trusted and
   trustworthy.

4.4.5.2.  Specification

   This option is specified in [RFC5570].

4.4.5.3.  Specific Security Implications

   Presence of this option in a packet does not by itself create any
   specific new threat.  Packets with this option ought not normally be
   seen on the global public Internet.

4.4.5.4.  Operational and Interoperability Impact if Blocked

   If packets with this option are discarded or if the option is
   stripped from the packet during transmission from source to
   destination, then the packet itself is likely to be discarded by the
   receiver because it is not properly labeled.  In some cases, the
   receiver might receive the packet but associate an incorrect
   sensitivity label with the received data from the packet whose
   CALIPSO was stripped by a middle-box (such as a packet-scrubber).
   Associating an incorrect sensitivity label can cause the received
   information either to be handled as more sensitive than it really is
   ("upgrading") or as less sensitive than it really is ("downgrading"),
   either of which is problematic.  As noted in [RFC5570], IPsec
   [RFC4301] [RFC4302] [RFC4303] can be employed to protect the CALIPSO
   option.

4.4.5.5.  Advice

   Recommendations for handling the CALIPSO option depend on the
   deployment environment, rather than whether an intermediate system
   happens to be deployed as a transit device (e.g., IPv6 transit
   router).

   Explicit configuration is the only method via which an intermediate
   system can know whether that particular intermediate system has been
   deployed within a Multi-Level Secure (MLS) environment.  In many
   cases, ordinary commercial intermediate systems (e.g., IPv6 routers
   and firewalls) are the majority of the deployed intermediate systems
   inside an MLS network environment.



Gont & Liu               Expires 4 November 2022               [Page 22]

Internet-Draft     Filtering of IPv6 packets with EHs           May 2022


   For Intermediate systems that DO NOT implement [RFC5570], there
   should be a configuration option to EITHER (a) drop packets
   containing the CALIPSO option OR (b) to ignore the presence of the
   CALIPSO option and forward the packets normally.  In non-MLS
   environments, such intermediate systems should have this
   configuration option set to (a) above.  In MLS environments, such
   intermediate systems should have this option set to (b) above.  The
   default setting for this configuration option should be set to (a)
   above, because MLS environments are much less common than non-MLS
   environments.

   For Intermediate systems that DO implement [RFC5570], there should be
   configuration options (a) and (b) from the preceding paragraph and
   also a third configuration option (c) to process packets containing a
   CALIPSO option as per [RFC5570].  When deployed in non-MLS
   environments, such intermediate systems should have this
   configuration option set to (a) above.  When deployed in MLS
   environments, such intermediate systems should have this set to (c).
   The default setting for this configuration option MAY be set to (a)
   above, because MLS environments are much less common than non-MLS
   environments.

4.4.6.  SMF_DPD (Type=0x08)

4.4.6.1.  Uses

   This option is employed in the (experimental) Simplified Multicast
   Forwarding (SMF) for unique packet identification for IPv6 I-DPD, and
   as a mechanism to guarantee non-collision of hash values for
   different packets when H-DPD is used.

4.4.6.2.  Specification

   This option is specified in [RFC6621].

4.4.6.3.  Specific Security Implications

   None.  The use of transient numeric identifiers is subject to the
   security and privacy considerations discussed in
   [I-D.irtf-pearg-numeric-ids-generation].

4.4.6.4.  Operational and Interoperability Impact if Blocked

   Dropping packets containing this option within a MANET domain would
   break SMF.  However, dropping such packets at the border of such
   domain would have no negative impact.





Gont & Liu               Expires 4 November 2022               [Page 23]

Internet-Draft     Filtering of IPv6 packets with EHs           May 2022


4.4.6.5.  Advice

   Intermediate systems that are not within a MANET domain should
   discard packets that contain this option.

4.4.7.  PDM (Type=0x0F)

4.4.7.1.  Uses

   This option is employed to convey sequence numbers and timing
   information in IPv6 packets as a basis for measurements.

4.4.7.2.  Specification

   This option is specified in [RFC8250].

4.4.7.3.  Specific Security Implications

   Those specified in [RFC8250].  Additionally, since the options
   employs transient numeric identifiers, implementations may be subject
   to the issues discussed in [I-D.irtf-pearg-numeric-ids-generation].

4.4.7.4.  Operational and Interoperability Impact if Blocked

   Dropping packets containing this option will result in negative
   interoperaiblity implications for traffic employing this option as a
   basis for measurements.

4.4.7.5.  Advice

   Intermediate systems should not discard packets based on the presence
   of this option.

4.4.8.  RPL Option (Type=0x23)

4.4.8.1.  Uses

   The RPL Option provides a mechanism to include routing information
   with each datagram that an RPL router forwards.

4.4.8.2.  Specification

   This option is specified in [RFC9008].

4.4.8.3.  Specific Security Implications

   Those described in [RFC9008].




Gont & Liu               Expires 4 November 2022               [Page 24]

Internet-Draft     Filtering of IPv6 packets with EHs           May 2022


4.4.8.4.  Operational and Interoperability Impact if Blocked

   This option can survive outside of an RPL instance.  As a result,
   discarding packets based on the presence of this option would break
   some use cases for RPL (see [RFC9008]).

4.4.8.5.  Advice

   Intermediate systems should not discard IPv6 packets based on the
   presence of this option.

4.4.9.  Quick-Start (Type=0x26)

4.4.9.1.  Uses

   This IP Option is used in the specification of Quick-Start for TCP
   and IP, which is an experimental mechanism that allows transport
   protocols, in cooperation with routers, to determine an allowed
   sending rate at the start and, at times, in the middle of a data
   transfer (e.g., after an idle period) [RFC4782].

4.4.9.2.  Specification

   This option is specified in [RFC4782], on the "Experimental" track.

4.4.9.3.  Specific Security Implications

   Section 9.6 of [RFC4782] notes that Quick-Start is vulnerable to two
   kinds of attacks:

   *  attacks to increase the routers' processing and state load, and,

   *  attacks with bogus Quick-Start Requests to temporarily tie up
      available Quick-Start bandwidth, preventing routers from approving
      Quick-Start Requests from other connections.

   We note that if routers in a given environment do not implement and
   enable the Quick-Start mechanism, only the general security
   implications of IP options (discussed in Section 4.2) would apply.

4.4.9.4.  Operational and Interoperability Impact if Blocked

   The Quick-Start functionality would be disabled, and additional
   delays in TCP's connection establishment (for example) could be
   introduced.  (Please see Section 4.7.2 of [RFC4782].)  We note,
   however, that Quick-Start has been proposed as a mechanism that could
   be of use in controlled environments, and not as a mechanism that
   would be intended or appropriate for ubiquitous deployment in the



Gont & Liu               Expires 4 November 2022               [Page 25]

Internet-Draft     Filtering of IPv6 packets with EHs           May 2022


   global Internet [RFC4782].

4.4.9.5.  Advice

   Intermediate systems should not discard IPv6 packets based on the
   presence of this option.

4.4.10.  Deprecated (Type=0x4D)

4.4.10.1.  Uses

   No information has been found about this option type.

4.4.10.2.  Specification

   No information has been found about this option type.

4.4.10.3.  Specific Security Implications

   No information has been found about this option type, and hence it
   has been impossible to perform the corresponding security assessment.

4.4.10.4.  Operational and Interoperability Impact if Blocked

   Unknown.

4.4.10.5.  Advice

   Intermediate systems should discard packets that contain this option.

4.4.11.  RPL Option (Type=0x63)

4.4.11.1.  Uses

   The RPL Option provides a mechanism to include routing information
   with each datagram that an RPL router forwards.

4.4.11.2.  Specification

   This option was originally specified in [RFC6553].  It has been
   deprecated by [RFC9008].

4.4.11.3.  Specific Security Implications

   Those described in [RFC9008].






Gont & Liu               Expires 4 November 2022               [Page 26]

Internet-Draft     Filtering of IPv6 packets with EHs           May 2022


4.4.11.4.  Operational and Interoperability Impact if Blocked

   This option is meant to be employed within an RPL instance.  As a
   result, discarding packets based on the presence of this option
   outside of an RPL instance will not result in interoperability
   implications.

4.4.11.5.  Advice

   Non-RPL routers should discard packets that contain an RPL option.

4.4.12.  MPL Option (Type=0x6D)

4.4.12.1.  Uses

   This option is used with the Multicast Protocol for Low power and
   Lossy Networks (MPL), that provides IPv6 multicast forwarding in
   constrained networks.

4.4.12.2.  Specification

   This option is specified in [RFC7731], and is meant to be included
   only in Hop-by-Hop Option headers.

4.4.12.3.  Specific Security Implications

   Those described in [RFC7731].

4.4.12.4.  Operational and Interoperability Impact if Blocked

   Dropping packets that contain an MPL option within an MPL network
   would break the Multicast Protocol for Low power and Lossy Networks
   (MPL).  However, dropping such packets at the border of such networks
   will have no negative impact.

4.4.12.5.  Advice

   Intermediate systems should not discard packets based on the presence
   of this option.  However, since this option has been specified for
   the Hop-by-Hop Options, such systems should consider the discussion
   in Section 3.5.1.

4.4.13.  Endpoint Identification (Type=0x8A)








Gont & Liu               Expires 4 November 2022               [Page 27]

Internet-Draft     Filtering of IPv6 packets with EHs           May 2022


4.4.13.1.  Uses

   The Endpoint Identification option was meant to be used with the
   Nimrod routing architecture [NIMROD-DOC], but has never seen
   widespread deployment.

4.4.13.2.  Specification

   This option is specified in [NIMROD-DOC].

4.4.13.3.  Specific Security Implications

   Undetermined.

4.4.13.4.  Operational and Interoperability Impact if Blocked

   None.

4.4.13.5.  Advice

   Intermediate systems should discard packets that contain this option.

4.4.14.  ILNP Nonce (Type=0x8B)

4.4.14.1.  Uses

   This option is employed by Identifier-Locator Network Protocol for
   IPv6 (ILNPv6) for providing protection against off-path attacks for
   packets when ILNPv6 is in use, and as a signal during initial
   network-layer session creation that ILNPv6 is proposed for use with
   this network-layer session, rather than classic IPv6.

4.4.14.2.  Specification

   This option is specified in [RFC6744].

4.4.14.3.  Specific Security Implications

   Those described in [RFC6744].

4.4.14.4.  Operational and Interoperability Impact if Blocked

   Discarding packets that contain this option will break INLPv6
   deployments.







Gont & Liu               Expires 4 November 2022               [Page 28]

Internet-Draft     Filtering of IPv6 packets with EHs           May 2022


4.4.14.5.  Advice

   Intermediate systems should not discard packets based on the presence
   of this option.

4.4.15.  Line-Identification Option (Type=0x8C)

4.4.15.1.  Uses

   This option is used by an Edge Router to identify the subscriber
   premises in scenarios where several subscriber premises may be
   logically connected to the same interface of an Edge Router.

4.4.15.2.  Specification

   This option is specified in [RFC6788].

4.4.15.3.  Specific Security Implications

   Those described in [RFC6788].

4.4.15.4.  Operational and Interoperability Impact if Blocked

   Since this option is meant to be employed in Router Solicitation
   messages, discarding packets based on the presence of this option at
   intermediate systems will result in no interoperability implications.

4.4.15.5.  Advice

   Intermediate devices should discard packets that contain this option.

4.4.16.  Jumbo Payload (Type=0XC2)

4.4.16.1.  Uses

   The Jumbo payload option provides the means of specifying payloads
   larger than 65535 bytes.

4.4.16.2.  Specification

   This option is specified in [RFC2675].

4.4.16.3.  Specific Security Implications

   There are no specific issues arising from this option, except for
   improper validity checks of the option and associated packet lengths.





Gont & Liu               Expires 4 November 2022               [Page 29]

Internet-Draft     Filtering of IPv6 packets with EHs           May 2022


4.4.16.4.  Operational and Interoperability Impact if Blocked

   Discarding packets based on the presence of this option will cause
   IPv6 jumbograms to be discarded.

4.4.16.5.  Advice

   An operator should permit this option only in specific scenarios in
   which support for IPv6 jumbograms is desired.

4.4.17.  Home Address (Type=0xC9)

4.4.17.1.  Uses

   The Home Address option is used by a Mobile IPv6 node while away from
   home, to inform the recipient of the mobile node's home address.

4.4.17.2.  Specification

   This option is specified in [RFC6275].

4.4.17.3.  Specific Security Implications

   No (known) additional security implications than those described in
   [RFC6275].

4.4.17.4.  Operational and Interoperability Impact if Blocked

   Discarding IPv6 packets based on the presence of this option will
   break Mobile IPv6.

4.4.17.5.  Advice

   Intermediate systems should not discard IPv6 packets based on the
   presence of this option.

4.4.18.  IP_DFF (Type=0xEE)

4.4.18.1.  Uses

   This option is employed with the (Experimental) Depth-First
   Forwarding (DFF) in Unreliable Networks.

4.4.18.2.  Specification

   This option is specified in [RFC6971].





Gont & Liu               Expires 4 November 2022               [Page 30]

Internet-Draft     Filtering of IPv6 packets with EHs           May 2022


4.4.18.3.  Specific Security Implications

   Those specified in [RFC6971].

4.4.18.4.  Operational and Interoperability Impact if Blocked

   Dropping packets containing this option within a routing domain that
   is running DFF would break DFF.  However, dropping such packets at
   the border of such domains will have no security implications.

4.4.18.5.  Advice

   Intermediate systems that do not operate within a routing domain that
   is running DFF should discard packets containing this option.

4.4.19.  RFC3692-style Experiment (Types = 0x1E, 0x3E, 0x5E, 0x7E, 0x9E,
         0xBE, 0xDE, 0xFE)

4.4.19.1.  Uses

   These options can be employed for performing RFC3692-style
   experiments.  It is only appropriate to use these values in
   explicitly configured experiments; they must not be shipped as
   defaults in implementations.

4.4.19.2.  Specification

   Specified in RFC 4727 [RFC4727] in the context of RFC3692-style
   experiments.

4.4.19.3.  Specific Security Implications

   The specific security implications will depend on the specific use of
   these options.

4.4.19.4.  Operational and Interoperability Impact if Blocked

   For obvious reasons, discarding packets that contain these options
   limits the ability to perform legitimate experiments across IPv6
   routers.

4.4.19.5.  Advice

   Operators should determine according to their own circumstances
   whether to discard packets containing these IPv6 options.






Gont & Liu               Expires 4 November 2022               [Page 31]

Internet-Draft     Filtering of IPv6 packets with EHs           May 2022


4.5.  Advice on the handling of Packets with Unknown IPv6 Options

   We refer to IPv6 options that have not been assigned an IPv6 option
   type in the corresponding registry ([IANA-IPV6-PARAM]) as "unknown
   IPv6 options".

4.5.1.  Uses

   New IPv6 options may be specified as part of future protocol work.

4.5.2.  Specification

   The processing of unknown IPv6 options is specified in [RFC8200].

4.5.3.  Specific Security Implications

   For obvious reasons, it is impossible to determine specific security
   implications of unknown IPv6 options.

4.5.4.  Operational and Interoperability Impact if Blocked

   Discarding unknown IPv6 options may slow down the deployment of new
   IPv6 options.  As noted in [draft-gont-6man-ipv6-opt-transmit], the
   corresponding IANA registry ([IANA-IPV6-PARAM] should be monitored
   such that IPv6 option filtering rules are updated as new IPv6 options
   are standardized.

4.5.5.  Advice

   Operators should determine according to their own circumstances
   whether to discard packets containing unknown IPv6 options.

5.  IANA Considerations

   This document has no actions for IANA.

6.  Privacy Considerations

   There are no privacy considerations associated with this document.

7.  Security Considerations

   This document provides advice on the filtering of IPv6 packets that
   contain IPv6 EHs (and possibly IPv6 options) at IPv6 transit routers.
   It is meant to improve the current situation of widespread dropping
   of such IPv6 packets in those cases where the drops result from
   improper configuration defaults, or inappropriate advice in this
   area.



Gont & Liu               Expires 4 November 2022               [Page 32]

Internet-Draft     Filtering of IPv6 packets with EHs           May 2022


   As discussed in Section Section 3.3 of this document, one of the
   underlying principles for the advice provided in this document is
   that IPv6 packets with specific EHs or options which may represent an
   attack vector for infrastructure devices should be dropped.  While
   this policy helps mitigate some specific attack vectors, the
   recommendations in this document will not help to mitigate
   vulnerabilities based on implementation errors [RFC9098].

   We also note that depending on the router architecture, attempts to
   filter packets ased on the presence of IPv6 EHs or options might
   itself represent an attack vector to network infrastructure devices
   [RFC9098].

8.  Acknowledgements

   The authors would like to thank Ron Bonica for his work on earlier
   versions of this document.

   The authors of this document would like to thank (in alphabetical
   order) Mikael Abrahamsson, Brian Carpenter, Tim Chown, Roman Danyliw,
   Darren Dukes, Lars Eggert, David Farmer, Mike Heard, Bob Hinden,
   Christian Huitema, Benjamin Kaduk, Erik Kline, Murray Kucherawy, Jen
   Linkova, Carlos Pignataro, Alvaro Retana, Maria Ines Robles,
   Zaheduzzaman Sarker, Donald Smith, Pascal Thubert, Ole Troan, Gunter
   Van De Velde, Eric Vyncke, and Robert Wilton, for providing valuable
   comments on earlier versions of this document.

   This document borrows some text and analysis from [RFC7126], authored
   by Fernando Gont, Randall Atkinson, and Carlos Pignataro.

   The authors would like to thank Warren Kumari and Eric Vyncke for
   their guidance during the publication process of this document.

   Fernando would also like to thank Brian Carpenter and Ran Atkinson
   who, over the years, have answered many questions and provided
   valuable comments that have benefited his protocol-related work
   (including the present document).

9.  References

9.1.  Normative References

   [RFC1034]  Mockapetris, P., "Domain names - concepts and facilities",
              STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987,
              <https://www.rfc-editor.org/info/rfc1034>.






Gont & Liu               Expires 4 November 2022               [Page 33]

Internet-Draft     Filtering of IPv6 packets with EHs           May 2022


   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC2205]  Braden, R., Ed., Zhang, L., Berson, S., Herzog, S., and S.
              Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1
              Functional Specification", RFC 2205, DOI 10.17487/RFC2205,
              September 1997, <https://www.rfc-editor.org/info/rfc2205>.

   [RFC2473]  Conta, A. and S. Deering, "Generic Packet Tunneling in
              IPv6 Specification", RFC 2473, DOI 10.17487/RFC2473,
              December 1998, <https://www.rfc-editor.org/info/rfc2473>.

   [RFC2675]  Borman, D., Deering, S., and R. Hinden, "IPv6 Jumbograms",
              RFC 2675, DOI 10.17487/RFC2675, August 1999,
              <https://www.rfc-editor.org/info/rfc2675>.

   [RFC2710]  Deering, S., Fenner, W., and B. Haberman, "Multicast
              Listener Discovery (MLD) for IPv6", RFC 2710,
              DOI 10.17487/RFC2710, October 1999,
              <https://www.rfc-editor.org/info/rfc2710>.

   [RFC2711]  Partridge, C. and A. Jackson, "IPv6 Router Alert Option",
              RFC 2711, DOI 10.17487/RFC2711, October 1999,
              <https://www.rfc-editor.org/info/rfc2711>.

   [RFC3692]  Narten, T., "Assigning Experimental and Testing Numbers
              Considered Useful", BCP 82, RFC 3692,
              DOI 10.17487/RFC3692, January 2004,
              <https://www.rfc-editor.org/info/rfc3692>.

   [RFC3810]  Vida, R., Ed. and L. Costa, Ed., "Multicast Listener
              Discovery Version 2 (MLDv2) for IPv6", RFC 3810,
              DOI 10.17487/RFC3810, June 2004,
              <https://www.rfc-editor.org/info/rfc3810>.

   [RFC4286]  Haberman, B. and J. Martin, "Multicast Router Discovery",
              RFC 4286, DOI 10.17487/RFC4286, December 2005,
              <https://www.rfc-editor.org/info/rfc4286>.

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

   [RFC4302]  Kent, S., "IP Authentication Header", RFC 4302,
              DOI 10.17487/RFC4302, December 2005,
              <https://www.rfc-editor.org/info/rfc4302>.



Gont & Liu               Expires 4 November 2022               [Page 34]

Internet-Draft     Filtering of IPv6 packets with EHs           May 2022


   [RFC4303]  Kent, S., "IP Encapsulating Security Payload (ESP)",
              RFC 4303, DOI 10.17487/RFC4303, December 2005,
              <https://www.rfc-editor.org/info/rfc4303>.

   [RFC4727]  Fenner, B., "Experimental Values In IPv4, IPv6, ICMPv4,
              ICMPv6, UDP, and TCP Headers", RFC 4727,
              DOI 10.17487/RFC4727, November 2006,
              <https://www.rfc-editor.org/info/rfc4727>.

   [RFC4782]  Floyd, S., Allman, M., Jain, A., and P. Sarolahti, "Quick-
              Start for TCP and IP", RFC 4782, DOI 10.17487/RFC4782,
              January 2007, <https://www.rfc-editor.org/info/rfc4782>.

   [RFC5095]  Abley, J., Savola, P., and G. Neville-Neil, "Deprecation
              of Type 0 Routing Headers in IPv6", RFC 5095,
              DOI 10.17487/RFC5095, December 2007,
              <https://www.rfc-editor.org/info/rfc5095>.

   [RFC5533]  Nordmark, E. and M. Bagnulo, "Shim6: Level 3 Multihoming
              Shim Protocol for IPv6", RFC 5533, DOI 10.17487/RFC5533,
              June 2009, <https://www.rfc-editor.org/info/rfc5533>.

   [RFC5570]  StJohns, M., Atkinson, R., and G. Thomas, "Common
              Architecture Label IPv6 Security Option (CALIPSO)",
              RFC 5570, DOI 10.17487/RFC5570, July 2009,
              <https://www.rfc-editor.org/info/rfc5570>.

   [RFC5971]  Schulzrinne, H. and R. Hancock, "GIST: General Internet
              Signalling Transport", RFC 5971, DOI 10.17487/RFC5971,
              October 2010, <https://www.rfc-editor.org/info/rfc5971>.

   [RFC6275]  Perkins, C., Ed., Johnson, D., and J. Arkko, "Mobility
              Support in IPv6", RFC 6275, DOI 10.17487/RFC6275, July
              2011, <https://www.rfc-editor.org/info/rfc6275>.

   [RFC6398]  Le Faucheur, F., Ed., "IP Router Alert Considerations and
              Usage", BCP 168, RFC 6398, DOI 10.17487/RFC6398, October
              2011, <https://www.rfc-editor.org/info/rfc6398>.

   [RFC6550]  Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J.,
              Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur,
              JP., and R. Alexander, "RPL: IPv6 Routing Protocol for
              Low-Power and Lossy Networks", RFC 6550,
              DOI 10.17487/RFC6550, March 2012,
              <https://www.rfc-editor.org/info/rfc6550>.






Gont & Liu               Expires 4 November 2022               [Page 35]

Internet-Draft     Filtering of IPv6 packets with EHs           May 2022


   [RFC6553]  Hui, J. and JP. Vasseur, "The Routing Protocol for Low-
              Power and Lossy Networks (RPL) Option for Carrying RPL
              Information in Data-Plane Datagrams", RFC 6553,
              DOI 10.17487/RFC6553, March 2012,
              <https://www.rfc-editor.org/info/rfc6553>.

   [RFC6554]  Hui, J., Vasseur, JP., Culler, D., and V. Manral, "An IPv6
              Routing Header for Source Routes with the Routing Protocol
              for Low-Power and Lossy Networks (RPL)", RFC 6554,
              DOI 10.17487/RFC6554, March 2012,
              <https://www.rfc-editor.org/info/rfc6554>.

   [RFC6621]  Macker, J., Ed., "Simplified Multicast Forwarding",
              RFC 6621, DOI 10.17487/RFC6621, May 2012,
              <https://www.rfc-editor.org/info/rfc6621>.

   [RFC6740]  Atkinson, RJ. and SN. Bhatti, "Identifier-Locator Network
              Protocol (ILNP) Architectural Description", RFC 6740,
              DOI 10.17487/RFC6740, November 2012,
              <https://www.rfc-editor.org/info/rfc6740>.

   [RFC6744]  Atkinson, RJ. and SN. Bhatti, "IPv6 Nonce Destination
              Option for the Identifier-Locator Network Protocol for
              IPv6 (ILNPv6)", RFC 6744, DOI 10.17487/RFC6744, November
              2012, <https://www.rfc-editor.org/info/rfc6744>.

   [RFC6788]  Krishnan, S., Kavanagh, A., Varga, B., Ooghe, S., and E.
              Nordmark, "The Line-Identification Option", RFC 6788,
              DOI 10.17487/RFC6788, November 2012,
              <https://www.rfc-editor.org/info/rfc6788>.

   [RFC6971]  Herberg, U., Ed., Cardenas, A., Iwao, T., Dow, M., and S.
              Cespedes, "Depth-First Forwarding (DFF) in Unreliable
              Networks", RFC 6971, DOI 10.17487/RFC6971, June 2013,
              <https://www.rfc-editor.org/info/rfc6971>.

   [RFC7045]  Carpenter, B. and S. Jiang, "Transmission and Processing
              of IPv6 Extension Headers", RFC 7045,
              DOI 10.17487/RFC7045, December 2013,
              <https://www.rfc-editor.org/info/rfc7045>.

   [RFC7112]  Gont, F., Manral, V., and R. Bonica, "Implications of
              Oversized IPv6 Header Chains", RFC 7112,
              DOI 10.17487/RFC7112, January 2014,
              <https://www.rfc-editor.org/info/rfc7112>.






Gont & Liu               Expires 4 November 2022               [Page 36]

Internet-Draft     Filtering of IPv6 packets with EHs           May 2022


   [RFC7401]  Moskowitz, R., Ed., Heer, T., Jokela, P., and T.
              Henderson, "Host Identity Protocol Version 2 (HIPv2)",
              RFC 7401, DOI 10.17487/RFC7401, April 2015,
              <https://www.rfc-editor.org/info/rfc7401>.

   [RFC7731]  Hui, J. and R. Kelsey, "Multicast Protocol for Low-Power
              and Lossy Networks (MPL)", RFC 7731, DOI 10.17487/RFC7731,
              February 2016, <https://www.rfc-editor.org/info/rfc7731>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8200]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", STD 86, RFC 8200,
              DOI 10.17487/RFC8200, July 2017,
              <https://www.rfc-editor.org/info/rfc8200>.

   [RFC8250]  Elkins, N., Hamilton, R., and M. Ackermann, "IPv6
              Performance and Diagnostic Metrics (PDM) Destination
              Option", RFC 8250, DOI 10.17487/RFC8250, September 2017,
              <https://www.rfc-editor.org/info/rfc8250>.

   [RFC8754]  Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J.,
              Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header
              (SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020,
              <https://www.rfc-editor.org/info/rfc8754>.

   [RFC8900]  Bonica, R., Baker, F., Huston, G., Hinden, R., Troan, O.,
              and F. Gont, "IP Fragmentation Considered Fragile",
              BCP 230, RFC 8900, DOI 10.17487/RFC8900, September 2020,
              <https://www.rfc-editor.org/info/rfc8900>.

   [RFC9008]  Robles, M.I., Richardson, M., and P. Thubert, "Using RPI
              Option Type, Routing Header for Source Routes, and IPv6-
              in-IPv6 Encapsulation in the RPL Data Plane", RFC 9008,
              DOI 10.17487/RFC9008, April 2021,
              <https://www.rfc-editor.org/info/rfc9008>.

9.2.  Informative References

   [Biondi2007]
              Biondi, P. and A. Ebalard, "IPv6 Routing Header Security",
              CanSecWest 2007 Security Conference, 2007,
              <http://www.secdev.org/conf/IPv6_RH_security-csw07.pdf>.






Gont & Liu               Expires 4 November 2022               [Page 37]

Internet-Draft     Filtering of IPv6 packets with EHs           May 2022


   [Cisco-EH] Cisco Systems, "IPv6 Extension Headers Review and
              Considerations",  Whitepaper. October 2006,
              <https://www.cisco.com/en/US/technologies/tk648/tk872/
              technologies_white_paper0900aecd8054d37d.pdf>.

   [draft-gont-6man-ipv6-opt-transmit]
              Gont, F., Liu, W., and R. Bonica, "Transmission and
              Processing of IPv6 Options",  IETF Internet Draft, work in
              progress, August 2014.

   [draft-ietf-nimrod-eid]
              Lynn, C.L., "Endpoint Identifier Destination
              Option",  IETF Internet Draft, draft-ietf-nimrod-eid-
              00.txt, November 1995.

   [FW-Benchmark]
              Zack, E., "Firewall Security Assessment and Benchmarking
              IPv6 Firewall Load Tests",  IPv6 Hackers Meeting #1,
              Berlin, Germany. June 30, 2013,
              <https://www.ipv6hackers.org/files/meetings/ipv6-hackers-
              1/zack-ipv6hackers1-firewall-security-assessment-and-
              benchmarking.pdf>.

   [Huston-2022]
              Huston, G. and J. Damas, "IPv6 Fragmentation and EH
              Behaviours",  IEPG Meeting - March 2022 @ IETF 113, March
              2022,
              <https://iepg.org/2022-03-20-ietf113/huston-v6frag.pdf>.

   [I-D.irtf-pearg-numeric-ids-generation]
              Gont, F. and I. Arce, "On the Generation of Transient
              Numeric Identifiers", Work in Progress, Internet-Draft,
              draft-irtf-pearg-numeric-ids-generation-08, 31 January
              2022, <https://www.ietf.org/archive/id/draft-irtf-pearg-
              numeric-ids-generation-08.txt>.

   [I-D.vyncke-v6ops-james]
              Vyncke, É., Léas, R., and J. Iurman, "Just Another
              Measurement of Extension header Survivability (JAMES)",
              Work in Progress, Internet-Draft, draft-vyncke-v6ops-
              james-01, 19 March 2022, <https://www.ietf.org/archive/id/
              draft-vyncke-v6ops-james-01.txt>.

   [IANA-IPV6-PARAM]
              Internet Assigned Numbers Authority, "Internet Protocol
              Version 6 (IPv6) Parameters", December 2013,
              <https://www.iana.org/assignments/ipv6-parameters/
              ipv6-parameters.xhtml>.



Gont & Liu               Expires 4 November 2022               [Page 38]

Internet-Draft     Filtering of IPv6 packets with EHs           May 2022


   [IANA-PROTOCOLS]
              Internet Assigned Numbers Authority, "Protocol Numbers",
              2014, <https://www.iana.org/assignments/protocol-numbers/
              protocol-numbers.xhtml>.

   [NIMROD-DOC]
              Nimrod Documentation Page,
              "http://ana-3.lcs.mit.edu/~jnc/nimrod/".

   [RFC2460]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460,
              December 1998, <https://www.rfc-editor.org/info/rfc2460>.

   [RFC3871]  Jones, G., Ed., "Operational Security Requirements for
              Large Internet Service Provider (ISP) IP Network
              Infrastructure", RFC 3871, DOI 10.17487/RFC3871, September
              2004, <https://www.rfc-editor.org/info/rfc3871>.

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

   [RFC7126]  Gont, F., Atkinson, R., and C. Pignataro, "Recommendations
              on Filtering of IPv4 Packets Containing IPv4 Options",
              BCP 186, RFC 7126, DOI 10.17487/RFC7126, February 2014,
              <https://www.rfc-editor.org/info/rfc7126>.

   [RFC7739]  Gont, F., "Security Implications of Predictable Fragment
              Identification Values", RFC 7739, DOI 10.17487/RFC7739,
              February 2016, <https://www.rfc-editor.org/info/rfc7739>.

   [RFC7872]  Gont, F., Linkova, J., Chown, T., and W. Liu,
              "Observations on the Dropping of Packets with IPv6
              Extension Headers in the Real World", RFC 7872,
              DOI 10.17487/RFC7872, June 2016,
              <https://www.rfc-editor.org/info/rfc7872>.

   [RFC9098]  Gont, F., Hilliard, N., Doering, G., Kumari, W., Huston,
              G., and W. Liu, "Operational Implications of IPv6 Packets
              with Extension Headers", RFC 9098, DOI 10.17487/RFC9098,
              September 2021, <https://www.rfc-editor.org/info/rfc9098>.

Authors' Addresses








Gont & Liu               Expires 4 November 2022               [Page 39]

Internet-Draft     Filtering of IPv6 packets with EHs           May 2022


   Fernando Gont
   EdgeUno
   Segurola y Habana 4310, 7mo Piso
   Villa Devoto
   Ciudad Autonoma de Buenos Aires
   Argentina
   Email: fernando.gont@edgeuno.com
   URI:   https://www.edgeuno.com


   Will (Shucheng) Liu
   Huawei Technologies
   Bantian, Longgang District
   Shenzhen
   518129
   P.R. China
   Email: liushucheng@huawei.com


































Gont & Liu               Expires 4 November 2022               [Page 40]