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
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Internet-Drafts are draft documents valid for a maximum of six months
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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/
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Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
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extracted from this document must include Revised BSD License text as
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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].
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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].
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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].
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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
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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.
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+=========================+==========================+===========+
| 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)
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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]
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* 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.
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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.
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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)
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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.
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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]
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* 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.
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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].
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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.
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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]).
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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 |
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+-------------------------------+----------------------+-----------+
| 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.
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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].
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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.
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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.
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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.
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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].
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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
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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].
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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)
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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.
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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.
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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].
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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.
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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.
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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>.
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[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>.
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[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>.
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[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>.
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[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>.
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[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>.
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[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
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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
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