< draft-ietf-v6ops-ipv6-ehs-packet-drops-00.txt   draft-ietf-v6ops-ipv6-ehs-packet-drops-01.txt >
IPv6 Operations Working Group (v6ops) F. Gont IPv6 Operations Working Group (v6ops) F. Gont
Internet-Draft SI6 Networks Internet-Draft SI6 Networks
Intended status: Informational N. Hilliard Intended status: Informational N. Hilliard
Expires: February 1, 2021 INEX Expires: April 17, 2021 INEX
G. Doering G. Doering
SpaceNet AG SpaceNet AG
W. Kumari W. Kumari
Google Google
G. Huston G. Huston
APNIC APNIC
W. Liu W. Liu
Huawei Technologies Huawei Technologies
July 31, 2020 October 14, 2020
Operational Implications of IPv6 Packets with Extension Headers Operational Implications of IPv6 Packets with Extension Headers
draft-ietf-v6ops-ipv6-ehs-packet-drops-00 draft-ietf-v6ops-ipv6-ehs-packet-drops-01
Abstract Abstract
This document summarizes the operational implications of IPv6 This document summarizes the operational implications of IPv6
extension headers, and attempts to analyze reasons why packets with extension headers, and attempts to analyze reasons why packets with
IPv6 extension headers may be dropped in the public Internet. IPv6 extension headers may be dropped in the public Internet.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
skipping to change at page 1, line 41 skipping to change at page 1, line 41
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on February 1, 2021. This Internet-Draft will expire on April 17, 2021.
Copyright Notice Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Disclaimer . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Disclaimer . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Previous Work on IPv6 Extension Headers . . . . . . . . . . . 3 3. Background Information . . . . . . . . . . . . . . . . . . . 3
4. Packet Forwarding Engine Constraints . . . . . . . . . . . . 5 4. Previous Work on IPv6 Extension Headers . . . . . . . . . . . 5
5. Requirement to Process Layer-3/layer-4 information in 5. Packet Forwarding Engine Constraints . . . . . . . . . . . . 7
Intermediate Systems . . . . . . . . . . . . . . . . . . . . 6 5.1. Recirculation . . . . . . . . . . . . . . . . . . . . . . 8
5.1. ECMP and Hash-based Load-Sharing . . . . . . . . . . . . 6 6. Requirement to Process Layer-3/layer-4 information in
5.2. Enforcing infrastructure ACLs . . . . . . . . . . . . . . 7 Intermediate Systems . . . . . . . . . . . . . . . . . . . . 8
5.3. DDoS Management and Customer Requests for Filtering . . . 7 6.1. ECMP and Hash-based Load-Sharing . . . . . . . . . . . . 8
6. Operational Implications . . . . . . . . . . . . . . . . . . 8 6.2. Enforcing infrastructure ACLs . . . . . . . . . . . . . . 9
6.1. Inability to Find Layer-4 Information . . . . . . . . . . 8 6.3. DDoS Management and Customer Requests for Filtering . . . 9
6.2. Route-Processor Protection . . . . . . . . . . . . . . . 8 6.4. Network Intrusion Detection and Prevention . . . . . . . 10
6.3. Inability to Perform Fine-grained Filtering . . . . . . . 8 6.5. Firewalling . . . . . . . . . . . . . . . . . . . . . . . 10
6.4. Security Concerns Associated with IPv6 Extension Headers 8 7. Operational Implications . . . . . . . . . . . . . . . . . . 11
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 7.1. Inability to Find Layer-4 Information . . . . . . . . . . 11
8. Security Considerations . . . . . . . . . . . . . . . . . . . 10 7.2. Route-Processor Protection . . . . . . . . . . . . . . . 11
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10 7.3. Inability to Perform Fine-grained Filtering . . . . . . . 12
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 10 7.4. Security Concerns Associated with IPv6 Extension Headers 12
10.1. Normative References . . . . . . . . . . . . . . . . . . 10 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
10.2. Informative References . . . . . . . . . . . . . . . . . 11 9. Security Considerations . . . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 13
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
11.1. Normative References . . . . . . . . . . . . . . . . . . 14
11.2. Informative References . . . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19
1. Introduction 1. Introduction
IPv6 Extension Headers (EHs) allow for the extension of the IPv6 IPv6 Extension Headers (EHs) allow for the extension of the IPv6
protocol, and provide support for core functionality such as IPv6 protocol, and provide support for core functionality such as IPv6
fragmentation. However, common implementation limitations suggest fragmentation. However, common implementation limitations suggest
that EHs present a challenge for IPv6 packet routing equipment and that EHs present a challenge for IPv6 packet routing equipment and
middle-boxes, and evidence exists that IPv6 packets with EHs may be middle-boxes, and evidence exists that IPv6 packets with EHs may be
intentionally dropped in the public Internet in some network intentionally dropped in the public Internet in some network
deployments. deployments.
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intentionally drop packets containing IPv6 Extension Headers. intentionally drop packets containing IPv6 Extension Headers.
o Highlight areas where current IPv6 support by networking devices o Highlight areas where current IPv6 support by networking devices
maybe sub-optimal, such that the aforementioned support is maybe sub-optimal, such that the aforementioned support is
improved. improved.
o Highlight operational issues associated with IPv6 extension o Highlight operational issues associated with IPv6 extension
headers, such that those issues are considered in IETF headers, such that those issues are considered in IETF
standardization efforts. standardization efforts.
Section 3 of this document summarizes the previous work that has been Section 3 provides background information about the IPv6 packet
carried out in the area of IPv6 extension headers. Section 4 structure and associated implications. Section 4 of this document
discuses packet forwarding engine constraints in modern routers. summarizes the previous work that has been carried out in the area of
Section 5 discusses why modern routers and middle-boxes may need to IPv6 extension headers. Section 5 discusses packet forwarding engine
access Layer-4 information to make a forwarding decision. Finally, constraints in contemporary routers. Section 6 discusses why
Section 6 discusses the operational implications of IPv6 EHs. contemporary routers and middle-boxes may need to access Layer-4
information to make a forwarding decision. Finally, Section 7
discusses the operational implications of IPv6 EHs.
2. Disclaimer 2. Disclaimer
This document analyzes the operational challenges represented by This document analyzes the operational challenges represented by
packets that employ IPv6 Extension Headers, and documents some of the packets that employ IPv6 Extension Headers, and documents some of the
operational reasons for which these packets may be dropped in the operational reasons why these packets may be dropped in the public
public Internet. This document IS NOT a recommendation to drop such Internet. This document is not a recommendation to drop such
packets, but rather an analysis of why they are dropped. packets, but rather an analysis of why they are dropped.
3. Previous Work on IPv6 Extension Headers 3. Background Information
It is useful to compare the basic structure of IPv6 packets against
that of IPv4 packets, and analyze the implications of the two
different packet structures.
IPv4 packets have a variable-length header size, that allows for the
use of IPv4 "options" -- optional information that may be of use by
nodes processing IPv4 packets. The IPv4 header length is specified
in the IHL header field of the mandatory IPv4 header, and must be in
the range from 20 octets (the minimum IPv4 header size) to 60 octets
(accommodating at most 40 octets of options). The upper-layer
protocol type is specified via the "Protocol" field of the mandatory
IPv4 header.
Protocol, IHL
+--------+
| |
| v
+------//-----+------------------------+
| | |
| IPv4 | Upper-Layer |
| Header | Protocol |
| | |
+-----//------+------------------------+
variable length
<------------->
Figure 1: IPv4 Packet Structure
IPv6 took a different approach to the IPv6 packet structure. Rather
than employing a variable-length header as IPv4 does, IPv6 employs a
linked-list-like packet structure, where a mandatory fixed-length
IPv6 header is followed by an arbitrary number of optional extension
headers, with the upper-layer header being the last header in the
IPv6 header chain. Each extension header typically specifies its
length (unless it is implicit from the extension header type), and
the "next header" type that follows in the IPv6 IPv6 header chain.
NH NH, EH-length NH, EH-length
+-------+ +------+ +-------+
| | | | | |
| v | v | v
+-------------+-------------+-//-+---------------+--------------+
| | | | | |
| IPv6 | Ext. | | Ext. | Upper-Layer |
| header | Header | | Header | Protocol |
| | | | | |
+-------------+-------------+-//-+---------------+--------------+
fixed length variable number of EHs & length
<------------> <-------------------------------->
Figure 2: IPv6 Packet Structure
This packet structure has the following implications:
o [RFC8200] requires the entire IPv6 header chain to be contained in
the first fragment of a packet, therefore limiting the IPv6
extension header chain to the size of the Path-MTU.
o Other than the Path-MTU constraints, there are no other limits to
the number of IPv6 EHs that may be present in a packet.
Therefore, there is no upper-limit regarding "how deep into the
IPv6 packet" the upper-layer may be found.
o The only way for a node to obtain the upper-layer protocol type or
find the upper-layer protocol header is to parse and process the
entire IPv6 header chain, in sequence, starting from the mandatory
IPv6 header, until the last header in the IPv6 header chain is
found.
4. Previous Work on IPv6 Extension Headers
Some of the operational implications of IPv6 Extension Headers have Some of the operational implications of IPv6 Extension Headers have
been discussed in IETF circles: been discussed in IETF circles:
o [I-D.taylor-v6ops-fragdrop] discusses a rationale for which o [I-D.taylor-v6ops-fragdrop] discusses a rationale for which
operators drop IPv6 fragments. operators drop IPv6 fragments.
o [I-D.wkumari-long-headers] discusses possible issues arising from o [I-D.wkumari-long-headers] discusses possible issues arising from
"long" IPv6 header chains. "long" IPv6 header chains.
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extension headers with the goal of providing a common and extension headers with the goal of providing a common and
consistent parsing methodology for IPv6 implementations. consistent parsing methodology for IPv6 implementations.
o [I-D.ietf-opsec-ipv6-eh-filtering] analyzes the security o [I-D.ietf-opsec-ipv6-eh-filtering] analyzes the security
implications of IPv6 EHs, and the operational implications of implications of IPv6 EHs, and the operational implications of
dropping packets that employ IPv6 EHs and associated options. dropping packets that employ IPv6 EHs and associated options.
o [RFC7113] discusses how some popular RA-Guard implementations are o [RFC7113] discusses how some popular RA-Guard implementations are
subject to evasion by means of IPv6 extension headers. subject to evasion by means of IPv6 extension headers.
o [I-D.ietf-intarea-frag-fragile] analyzes the fragility introduced o [RFC8900] analyzes the fragility introduced by IP fragmentation.
by IP fragmentation.
A number of recent RFCs have discussed issues related to IPv6 A number of recent RFCs have discussed issues related to IPv6
extension headers, specifying updates to a previous revision of the extension headers, specifying updates to a previous revision of the
IPv6 standard ([RFC2460]), many of which have now been incorporated IPv6 standard ([RFC2460]), many of which have now been incorporated
into the current IPv6 core standard ([RFC8200]) or the IPv6 Node into the current IPv6 core standard ([RFC8200]) or the IPv6 Node
Requirements ([RFC8504]). Namely, Requirements ([RFC8504]). Namely,
o [RFC5095] discusses the security implications of Routing Header o [RFC5095] discusses the security implications of Routing Header
Type 0 (RTH0), and deprecates it. Type 0 (RTH0), and deprecates it.
o [RFC5722] analyzes the security implications of overlapping o [RFC5722] analyzes the security implications of overlapping
fragments, and provides recommendations in this area. fragments, and provides recommendations in this area.
o [RFC7045] clarifies how intermediate nodes should deal with IPv6 o [RFC7045] clarifies how intermediate nodes should deal with IPv6
extension headers. extension headers.
o [RFC7112] discusses the issues arising in a specific fragmentation o [RFC7112] discusses the issues arising in a specific fragmentation
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o [RFC7739] discusses the security implications of predictable o [RFC7739] discusses the security implications of predictable
fragment Identification values, and provides recommendations for fragment Identification values, and provides recommendations for
the generation of these values. the generation of these values.
o [RFC6980] analyzes the security implications of employing IPv6 o [RFC6980] analyzes the security implications of employing IPv6
fragmentation with Neighbor Discovery for IPv6, and formally fragmentation with Neighbor Discovery for IPv6, and formally
recommends against such usage. recommends against such usage.
Additionally, [RFC8200] has relaxed the requirement that "all nodes Additionally, [RFC8200] has relaxed the requirement that "all nodes
examine and process the Hop-by-Hop Options header" from [RFC2460], by examine and process the Hop-by-Hop Options header" from [RFC2460], by
specifying that only to nodes that have been explicitly configured to specifying that only nodes that have been explicitly configured to
process the Hop-by-Hop Options header are required to do so. process the Hop-by-Hop Options header are required to do so.
A number of studies have measured the extent to which packets A number of studies have measured the extent to which packets
employing IPv6 extension headers are dropped in the public Internet: employing IPv6 extension headers are dropped in the public Internet:
o [PMTUD-Blackholes], [Gont-IEPG88], [Gont-Chown-IEPG89], and o [PMTUD-Blackholes], [Gont-IEPG88], [Gont-Chown-IEPG89], and
[Linkova-Gont-IEPG90] presented some preliminary measurements [Linkova-Gont-IEPG90] presented some preliminary measurements
regarding the extent to which packet containing IPv6 EHs are regarding the extent to which packet containing IPv6 EHs are
dropped in the public Internet. dropped in the public Internet.
o [RFC7872] presents more comprehensive results and documents the o [RFC7872] presents more comprehensive results and documents the
methodology for obtaining the presented results. methodology for obtaining the presented results.
o [Huston-2017] and [Huston-2020] measured packet drops resulting o [Huston-2017] and [Huston-2020] measured packet drops resulting
from IPv6 fragmentation when communicating with DNS servers. from IPv6 fragmentation when communicating with DNS servers.
4. Packet Forwarding Engine Constraints 5. Packet Forwarding Engine Constraints
Most modern routers use dedicated hardware (e.g. ASICs or NPUs) to Most contemporary routers use dedicated hardware (e.g. ASICs or
determine how to forward packets across their internal fabrics (see NPUs) to determine how to forward packets across their internal
[IEPG94-Scudder] and [APNIC-Scudder] for details). One of the common fabrics (see [IEPG94-Scudder] and [APNIC-Scudder] for details). One
methods of handling next-hop lookup is to send a small portion of the of the common methods of handling next-hop lookup is to send a small
ingress packet to a lookup engine with specialised hardware (e.g. portion of the ingress packet to a lookup engine with specialised
ternary CAM or RLDRAM) to determine the packet's next-hop. Technical hardware (e.g. ternary CAM or RLDRAM) to determine the packet's next-
constraints mean that there is a trade-off between the amount of data hop. Technical constraints mean that there is a trade-off between
sent to the lookup engine and the overall performance of the lookup the amount of data sent to the lookup engine and the overall
engine. If more data is sent, the lookup engine can inspect further performance of the lookup engine. If more data is sent, the lookup
into the packet, but the overall performance of the system will be engine can inspect further into the packet, but the overall
reduced. If less data is sent, the overall performance of the router performance of the system will be reduced. If less data is sent, the
will be increased but the packet lookup engine may not be able to overall performance of the router will be increased but the packet
inspect far enough into a packet to determine how it should be lookup engine may not be able to inspect far enough into a packet to
handled. determine how it should be handled.
NOTE: NOTE:
For example, current high-end routers can use up to 192 bytes of For example, contemporary high-end routers can use up to 192 bytes
header (Cisco ASR9000 Typhoon) or 384 bytes of header (Juniper MX of header (Cisco ASR9000 Typhoon) or 384 bytes of header (Juniper
Trio). MX Trio).
If a hardware forwarding engine on a modern router cannot make a If a hardware forwarding engine on a contemporary router cannot make
forwarding decision about a packet because critical information is a forwarding decision about a packet because critical information is
not sent to the look-up engine, then the router will normally drop not sent to the look-up engine, then the router will normally drop
the packet. the packet.
NOTE: NOTE:
Section 6 discusses some of the reasons for which a contemporary
Section 5 discusses some of the reasons for which a modern router router might need to access layer-4 information to make a
might need to access layer-4 information to make a forwarding forwarding decision.
decision.
Historically, some packet forwarding engines punted packets of this Historically, some packet forwarding engines punted packets of this
form to the control plane for more in-depth analysis, but this is form to the control plane for more in-depth analysis, but this is
unfeasible on most current router architectures as a result of the unfeasible on most current router architectures as a result of the
vast difference between the hardware forwarding capacity of the vast difference between the hardware forwarding capacity of the
router and processing capacity of the control plane and the size of router and processing capacity of the control plane and the size of
the management link which connects the control plane to the the management link which connects the control plane to the
forwarding plane. forwarding plane.
If an IPv6 header chain is sufficiently long that its header exceeds If an IPv6 header chain is sufficiently long that its header exceeds
the packet look-up capacity of the router, then it may be dropped due the packet look-up capacity of the router, then it may be dropped due
to hardware inability to determine how it should be handled. to hardware inability to determine how it should be handled.
5. Requirement to Process Layer-3/layer-4 information in Intermediate 5.1. Recirculation
Although TLV chains are amenable to iterative processing on
architectures which have packet look-up engines with deep inspection
capabilities, some packet forwarding engines manage IPv6 Extension
Header chains using recirculation. This approach processes Extension
Headers one at a time: when processing on one Extension Header is
completed, the packet is looped back through the processing engine
again. This recirculation process continues repeatedly until there
are no more Extension Headers left to be processed.
Recirculation is typically used on packet forwarding engines with
limited look-up capability, as it allows arbitrarily long header
chains to be processed without the complexity and cost associated
with packet forwarding engines which have deep look-up capabilities.
However, recirculation can impact the forwarding capacity of
hardware, as each packet will pass through the processing engine
multiple times. Depending on configuration, the type of packets
being processed, and the hardware capabilities of the packet
forwarding engine, this may impact data-plane throughput performance
on the router.
6. Requirement to Process Layer-3/layer-4 information in Intermediate
Systems Systems
The following subsections discuss some of reasons for which modern The following subsections discuss some of reasons for which
routers and middle-boxes may need to process Layer-3/layer-4 contemporary routers and middle-boxes may need to process Layer-3/
information to make a forwarding decision. layer-4 information to make a forwarding decision.
5.1. ECMP and Hash-based Load-Sharing 6.1. ECMP and Hash-based Load-Sharing
In the case of ECMP (equal cost multi path) load sharing, the router In the case of ECMP (equal cost multi path) load sharing, the router
on the sending side of the link needs to make a decision regarding on the sending side of the link needs to make a decision regarding
which of the links to use for a given packet. Since round-robin which of the links to use for a given packet. Since round-robin
usage of the links is usually avoided in order to prevent packet usage of the links is usually avoided in order to prevent packet
reordering, forwarding engines need to use a mechanism which will reordering, forwarding engines need to use a mechanism which will
consistently forward the same data streams down the same forwarding consistently forward the same data streams down the same forwarding
paths. Most forwarding engines achieve this by calculating a simple paths. Most forwarding engines achieve this by calculating a simple
hash using an n-tuple gleaned from a combination of layer-2 through hash using an n-tuple gleaned from a combination of layer-2 through
to layer-4 packet header information. This n-tuple will typically to layer-4 packet header information. This n-tuple will typically
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Clearly, widespread support of [RFC6437] would relieve middle-boxes Clearly, widespread support of [RFC6437] would relieve middle-boxes
from having to process the entire IPv6 header chain, making Flow from having to process the entire IPv6 header chain, making Flow
Label-based ECMP and Hash-based Load-Sharing [RFC6438] feasible. Label-based ECMP and Hash-based Load-Sharing [RFC6438] feasible.
While support of [RFC6437] is currently widespread for current While support of [RFC6437] is currently widespread for current
versions of all popular host implementations, there is still only versions of all popular host implementations, there is still only
marginal usage of the IPv6 Flow Label for ECMP and load balancing marginal usage of the IPv6 Flow Label for ECMP and load balancing
[Cunha-2020] -- possibly as a result of issues that have been found [Cunha-2020] -- possibly as a result of issues that have been found
in host implementations and middle-boxes [Jaeggli-2018]. in host implementations and middle-boxes [Jaeggli-2018].
5.2. Enforcing infrastructure ACLs 6.2. Enforcing infrastructure ACLs
Generally speaking, infrastructure ACLs (iACLs) drop unwanted packets Generally speaking, infrastructure ACLs (iACLs) drop unwanted packets
destined to parts of a provider's infrastructure, because they are destined to parts of a provider's infrastructure, because they are
not operationally needed and can be used for attacks of different not operationally needed and can be used for attacks of different
sorts against the router's control plane. Some traffic needs to be sorts against router control planes. Some traffic needs to be
differentiated depending on layer-3 or layer-4 criteria to achieve a differentiated depending on layer-3 or layer-4 criteria to achieve a
useful balance of protection and functionality, for example: useful balance of protection and functionality, for example:
o Permit some amount of ICMP echo (ping) traffic towards the o Permit some amount of ICMP echo (ping) traffic towards a router's
router's addresses for troubleshooting. addresses for troubleshooting.
o Permit BGP sessions on the shared network of an exchange point o Permit BGP sessions on the shared network of an exchange point
(potentially differentiating between the amount of packets/seconds (potentially differentiating between the amount of packets/seconds
permitted for established sessions and connection establishment), permitted for established sessions and connection establishment),
but do not permit other traffic from the same peer IP addresses. but do not permit other traffic from the same peer IP addresses.
5.3. DDoS Management and Customer Requests for Filtering 6.3. DDoS Management and Customer Requests for Filtering
The case of customer DDoS protection and edge-to-core customer The case of customer DDoS protection and edge-to-core customer
protection filters is similar in nature to the infrastructure ACL protection filters is similar in nature to the infrastructure ACL
protection. Similar to infrastructure ACL protection, layer-4 ACLs protection. Similar to infrastructure ACL protection, layer-4 ACLs
generally need to be applied as close to the edge of the network as generally need to be applied as close to the edge of the network as
possible, even though the intent is usually to protect the customer possible, even though the intent is usually to protect the customer
edge rather than the provider core. Application of layer-4 DDoS edge rather than the provider core. Application of layer-4 DDoS
protection to a network edge is often automated using Flowspec protection to a network edge is often automated using Flowspec
[RFC5575]. [RFC5575].
skipping to change at page 8, line 5 skipping to change at page 10, line 11
ports 80 and 443 could be subject to a volumetric DDoS attack using ports 80 and 443 could be subject to a volumetric DDoS attack using
NTP and DNS packets with randomised source IP address, thereby NTP and DNS packets with randomised source IP address, thereby
rendering traditional [RFC5635] source-based real-time black hole rendering traditional [RFC5635] source-based real-time black hole
mechanisms useless. In this situation, DDoS protection ACLs could be mechanisms useless. In this situation, DDoS protection ACLs could be
configured to block all UDP traffic at the network edge without configured to block all UDP traffic at the network edge without
impairing the web server functionality in any way. Thus, being able impairing the web server functionality in any way. Thus, being able
to block arbitrary protocols at the network edge can avoid DDoS- to block arbitrary protocols at the network edge can avoid DDoS-
related problems both in the provider network and on the customer related problems both in the provider network and on the customer
edge link. edge link.
6. Operational Implications 6.4. Network Intrusion Detection and Prevention
6.1. Inability to Find Layer-4 Information Network Intrusion Detection Systems (NIDS) examine network traffic
and try to identify traffic patterns that can be correlated to
network-based attacks. These systems generally inspect application-
layer traffic (if possible), but at the bare minimum inspect layer-4
flows. When attack activity is inferred, the operator is signaled of
the potential intrusion attempt.
As discussed in Section 5, modern routers and middle-boxes that need Network Intrusion Prevention Systems (IPS) operate similarly to
to find the layer-4 header must process the entire IPv6 extension NIDS's, but they may also prevent intrusions by reacting to detected
header chain. When such devices are unable to obtain the required attack attempts by e.g. triggering packet filtering policies at
information, they may simply resort to dropping the corresponding firewalls and other devices.
packets.
6.2. Route-Processor Protection Use of extension headers may result problematic for NIDS/IPS, since:
Most modern routers have a fast hardware-assisted forwarding plane o Extension headers increase the complexity of resulting traffic,
and a loosely coupled control plane, connected together with a link and the associated work and system requirements to process it.
that has much less capacity than the forwarding plane could handle.
Traffic differentiation cannot be done by the control plane side, o Use of unknown extension headers may prevent an NIDS/IPS to
because this would overload the internal link connecting the process layer-4 information
o Use of IPv6 fragmentation requires a stateful fragment-reassembly
operation, even for decoy traffic employing forged source
addresses (see e.g. [nmap]).
As a result, in order to increase the efficiency or effectiveness of
these systems, packets employing IPv6 extension headers may be
dropped at the network ingress point(s) of networks that deploy these
systems.
6.5. Firewalling
Firewalls enforce security policies by means of packet filtering.
These systems generally inspect layer-3 and layer-4 traffic, and may
also examine application-layer traffic flows.
As with NIDS/IPS (Section 6.4), use of IPv6 extension headers may
represent a challenge to network firewalls, since:
o Extension headers increase the complexity of resulting traffic,
and the associated work and system requirements to process it (see
e.g. [Zack-FW-Benchmark]).
o Use of unknown extension headers may prevent an NIDS/IPS to
process layer-4 information
o Use of IPv6 fragmentation requires a stateful fragment-reassembly
operation, even for decoy traffic employing forged source
addresses (see e.g. [nmap]).
Additionally, a common firewall filtering policy is the so-called
"default deny", where all traffic is blocked (by default), and only
expected traffic is added to an "allow/accept list".
As a result, whether because of the challenges represented by
extension headers or because the use of IPv6 extension headers has
not been explicitly allowed, packets employing IPv6 extension headers
may be dropped by network firewalls.
7. Operational Implications
7.1. Inability to Find Layer-4 Information
As discussed in Section 6, contemporary routers and middle-boxes that
need to find the layer-4 header must process the entire IPv6
extension header chain. When such devices are unable to obtain the
required information, they may simply resort to dropping the
corresponding packets.
7.2. Route-Processor Protection
Most contemporary routers have a fast hardware-assisted forwarding
plane and a loosely coupled control plane, connected together with a
link that has much less capacity than the forwarding plane could
handle. Traffic differentiation cannot be done by the control plane
side, because this would overload the internal link connecting the
forwarding plane to the control plane. forwarding plane to the control plane.
The Hop-by-Hop Options header has been particularly challenging The Hop-by-Hop Options header has been particularly challenging since
since, in most (if not all) implementations, it has typically caused in most circumstances, the corresponding packet is punted to the
the corresponding packet to be punted to a software path. As a control plane for processing. As a result, operators usually drop
result, operators usually drop IPv6 packets containing this extension IPv6 packets containing this extension header. Please see [RFC6192]
header. Please see [RFC6192] for advice regarding protection of the for advice regarding protection of the router control plane.
router control plane.
6.3. Inability to Perform Fine-grained Filtering 7.3. Inability to Perform Fine-grained Filtering
Some router implementations lack fine-grained filtering of IPv6 Some router implementations lack fine-grained filtering of IPv6
extension headers. For example, an operator may want to drop packets extension headers. For example, an operator may want to drop packets
containing Routing Header Type 0 (RHT0) but may only be able to containing Routing Header Type 0 (RHT0) but may only be able to
filter on the extension header type (Routing Header). As a result, filter on the extension header type (Routing Header). As a result,
the operator may end up enforcing a more coarse filtering policy the operator may end up enforcing a more coarse filtering policy
(e.g. "drop all packets containing a Routing Header" vs. "only drop (e.g. "drop all packets containing a Routing Header" vs. "only drop
packets that contain a Routing Header Type 0"). packets that contain a Routing Header Type 0").
6.4. Security Concerns Associated with IPv6 Extension Headers 7.4. Security Concerns Associated with IPv6 Extension Headers
The security implications of IPv6 Extension Headers generally fall The security implications of IPv6 Extension Headers generally fall
into one or more of these categories: into one or more of these categories:
o Evasion of security controls o Evasion of security controls
o DoS due to processing requirements o DoS due to processing requirements
o DoS due to implementation errors o DoS due to implementation errors
skipping to change at page 9, line 4 skipping to change at page 12, line 27
The security implications of IPv6 Extension Headers generally fall The security implications of IPv6 Extension Headers generally fall
into one or more of these categories: into one or more of these categories:
o Evasion of security controls o Evasion of security controls
o DoS due to processing requirements o DoS due to processing requirements
o DoS due to implementation errors o DoS due to implementation errors
o Extension Header-specific issues o Extension Header-specific issues
Unlike IPv4 packets where the upper-layer protocol can be trivially Unlike IPv4 packets where the upper-layer protocol can be trivially
found by means of the "IHL" ("Internet Header Length") IPv4 header found by means of the "IHL" ("Internet Header Length") IPv4 header
field, the structure of IPv6 packets is more flexible and complex, field, the structure of IPv6 packets is more flexible and complex,
and may represent a challenge for devices that need to find this and may represent a challenge for devices that need to find this
information, since locating upper-layer protocol information requires information, since locating upper-layer protocol information requires
that all IPv6 extension headers be examined. This has presented that all IPv6 extension headers be examined. This has presented
implementation difficulties, and packet filtering mechanisms that implementation difficulties, and packet filtering mechanisms that
require upper-layer information (even if just the upper layer require upper-layer information (even if just the upper layer
protocol type) have been found to be trivially evasible by inserting protocol type) can be trivially circumvented by inserting IPv6
IPv6 Extension Headers between the main IPv6 header and the upper Extension Headers between the main IPv6 header and the upper layer
layer protocol. [RFC7113] describes this issue for the RA-Guard protocol. [RFC7113] describes this issue for the RA-Guard case, but
case, but the same techniques can be employed to circumvent other the same techniques can be employed to circumvent other IPv6 firewall
IPv6 firewall and packet filtering mechanisms. Additionally, and packet filtering mechanisms. Additionally, implementation
implementation inconsistencies in packet forwarding engines may inconsistencies in packet forwarding engines may result in evasion of
result in evasion of security controls security controls [I-D.kampanakis-6man-ipv6-eh-parsing] [Atlasis2014]
[I-D.kampanakis-6man-ipv6-eh-parsing] [Atlasis2014] [BH-EU-2014]. [BH-EU-2014].
Packets that use IPv6 Extension Headers may have a negative Packets with attached IPv6 Extension Headers may impact performance
performance impact on the handling devices. Unless appropriate on routers that forward them. Unless appropriate mitigations are put
mitigations are put in place (e.g., packet dropping and/or rate- in place (e.g., packet dropping and/or rate-limiting), an attacker
limiting), an attacker could simply send a large amount of IPv6 could simply send a large amount of IPv6 traffic employing IPv6
traffic employing IPv6 Extension Headers with the purpose of Extension Headers with the purpose of performing a Denial of Service
performing a Denial of Service (DoS) attack (see Section 6 for (DoS) attack (see Section 7 for further details).
further details).
NOTE: NOTE:
In the most trivial case, a packet that includes a Hop-by-Hop In the most trivial case, a packet that includes a Hop-by-Hop
Options header might go through the slow forwarding path, and be Options header might go through the slow forwarding path, and be
processed by the router's CPU. Another possible case might be processed by the router's CPU. Another possible case might be
that in which a router that has been configured to enforce an ACL where a router that has been configured to enforce an ACL based on
based on upper-layer information (e.g., upper layer protocol or upper-layer information (e.g., upper layer protocol or TCP
TCP Destination Port), needs to process the entire IPv6 header Destination Port), needs to process the entire IPv6 header chain
chain (in order to find the required information), causing the (in order to find the required information), causing the packet to
packet to be processed in the slow path [Cisco-EH-Cons]. We note be processed in the slow path [Cisco-EH-Cons]. We note that, for
that, for obvious reasons, the aforementioned performance issues obvious reasons, the aforementioned performance issues may affect
may affect other devices such as firewalls, Network Intrusion other devices such as firewalls, Network Intrusion Detection
Detection Systems (NIDS), etc. [Zack-FW-Benchmark]. The extent Systems (NIDS), etc. [Zack-FW-Benchmark]. The extent to which
to which these devices are affected is typically implementation- these devices are affected is typically implementation-dependent.
dependent.
IPv6 implementations, like all other software, tend to mature with IPv6 implementations, like all other software, tend to mature with
time and wide-scale deployment. While the IPv6 protocol itself has time and wide-scale deployment. While the IPv6 protocol itself has
existed for over 20 years, serious bugs related to IPv6 Extension existed for over 20 years, serious bugs related to IPv6 Extension
Header processing continue to be discovered. Because there is Header processing continue to be discovered (see e.g. [Cisco-Frag1],
currently little operational reliance on IPv6 Extension headers, the [Cisco-Frag2], and [FreeBSD-SA]). Because there is currently little
corresponding code paths are rarely exercised, and there is the operational reliance on IPv6 Extension headers, the corresponding
potential for bugs that still remain to be discovered in some code paths are rarely exercised, and there is the potential for bugs
implementations. that still remain to be discovered in some implementations.
IPv6 Fragment Headers are employed to allow fragmentation of IPv6 IPv6 Fragment Headers are employed to allow fragmentation of IPv6
packets. While many of the security implications of the packets. While many of the security implications of the
fragmentation / reassembly mechanism are known from the IPv4 world, fragmentation / reassembly mechanism are known from the IPv4 world,
several related issues have crept into IPv6 implementations. These several related issues have crept into IPv6 implementations. These
range from denial of service attacks to information leakage, as range from denial of service attacks to information leakage, as
discussed in [RFC7739], [Bonica-NANOG58] and [Atlasis2012]). discussed in [RFC7739], [Bonica-NANOG58] and [Atlasis2012]).
7. IANA Considerations 8. IANA Considerations
There are no IANA registries within this document. The RFC-Editor There are no IANA registries within this document. The RFC-Editor
can remove this section before publication of this document as an can remove this section before publication of this document as an
RFC. RFC.
8. Security Considerations 9. Security Considerations
The security implications of IPv6 extension headers are discussed in The security implications of IPv6 extension headers are discussed in
Section 6.4. This document does not introduce any new security Section 7.4. This document does not introduce any new security
issues. issues.
9. Acknowledgements 10. Acknowledgements
The authors would like to thank (in alphabetical order) Mikael The authors would like to thank (in alphabetical order) Mikael
Abrahamsson, Fred Baker, Brian Carpenter, Tim Chown, Owen DeLong, Tom Abrahamsson, Fred Baker, Brian Carpenter, Tim Chown, Owen DeLong, Tom
Herbert, Lee Howard, Sander Steffann, Eduard Vasilenko, Eric Vyncke, Herbert, Lee Howard, Tom Petch, Sander Steffann, Eduard Vasilenko,
Jingrong Xie, and Andrew Yourtchenko, for providing valuable comments Eric Vyncke, Jingrong Xie, and Andrew Yourtchenko, for providing
on earlier versions of this document. valuable comments on earlier versions of this document.
Fernando Gont would like to thank Jan Zorz / Go6 Lab Fernando Gont would like to thank Jan Zorz / Go6 Lab
<http://go6lab.si/>, Jared Mauch, and Sander Steffann <https://go6lab.si/>, Jared Mauch, and Sander Steffann
<http://steffann.nl/>, for providing access to systems and networks <https://steffann.nl/>, for providing access to systems and networks
that were employed to perform experiments and measurements involving that were employed to perform experiments and measurements involving
packets with IPv6 Extension Headers. packets with IPv6 Extension Headers.
10. References 11. References
10.1. Normative References
[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 11.1. Normative References
(IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460,
December 1998, <https://www.rfc-editor.org/info/rfc2460>.
[RFC5095] Abley, J., Savola, P., and G. Neville-Neil, "Deprecation [RFC5095] Abley, J., Savola, P., and G. Neville-Neil, "Deprecation
of Type 0 Routing Headers in IPv6", RFC 5095, of Type 0 Routing Headers in IPv6", RFC 5095,
DOI 10.17487/RFC5095, December 2007, DOI 10.17487/RFC5095, December 2007,
<https://www.rfc-editor.org/info/rfc5095>. <https://www.rfc-editor.org/info/rfc5095>.
[RFC5722] Krishnan, S., "Handling of Overlapping IPv6 Fragments", [RFC5722] Krishnan, S., "Handling of Overlapping IPv6 Fragments",
RFC 5722, DOI 10.17487/RFC5722, December 2009, RFC 5722, DOI 10.17487/RFC5722, December 2009,
<https://www.rfc-editor.org/info/rfc5722>. <https://www.rfc-editor.org/info/rfc5722>.
skipping to change at page 11, line 37 skipping to change at page 15, line 5
[RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", STD 86, RFC 8200, (IPv6) Specification", STD 86, RFC 8200,
DOI 10.17487/RFC8200, July 2017, DOI 10.17487/RFC8200, July 2017,
<https://www.rfc-editor.org/info/rfc8200>. <https://www.rfc-editor.org/info/rfc8200>.
[RFC8504] Chown, T., Loughney, J., and T. Winters, "IPv6 Node [RFC8504] Chown, T., Loughney, J., and T. Winters, "IPv6 Node
Requirements", BCP 220, RFC 8504, DOI 10.17487/RFC8504, Requirements", BCP 220, RFC 8504, DOI 10.17487/RFC8504,
January 2019, <https://www.rfc-editor.org/info/rfc8504>. January 2019, <https://www.rfc-editor.org/info/rfc8504>.
10.2. Informative References 11.2. Informative References
[APNIC-Scudder] [APNIC-Scudder]
Scudder, J., "Modern router architecture and IPv6", APNIC Scudder, J., "Modern router architecture and IPv6", APNIC
Blog, June 4, 2020, <https://blog.apnic.net/2020/06/04/ Blog, June 4, 2020, <https://blog.apnic.net/2020/06/04/
modern-router-architecture-and-ipv6/>. modern-router-architecture-and-ipv6/>.
[Atlasis2012] [Atlasis2012]
Atlasis, A., "Attacking IPv6 Implementation Using Atlasis, A., "Attacking IPv6 Implementation Using
Fragmentation", BlackHat Europe 2012. Amsterdam, Fragmentation", BlackHat Europe 2012. Amsterdam,
Netherlands. March 14-16, 2012, Netherlands. March 14-16, 2012,
skipping to change at page 12, line 18 skipping to change at page 15, line 32
<http://www.insinuator.net/2014/05/a-novel-way-of-abusing- <http://www.insinuator.net/2014/05/a-novel-way-of-abusing-
ipv6-extension-headers-to-evade-ipv6-security-devices/>. ipv6-extension-headers-to-evade-ipv6-security-devices/>.
[BH-EU-2014] [BH-EU-2014]
Atlasis, A., Rey, E., and R. Schaefer, "Evasion of High- Atlasis, A., Rey, E., and R. Schaefer, "Evasion of High-
End IDPS Devices at the IPv6 Era", BlackHat Europe 2014, End IDPS Devices at the IPv6 Era", BlackHat Europe 2014,
2014, <https://www.ernw.de/download/eu-14-Atlasis-Rey- 2014, <https://www.ernw.de/download/eu-14-Atlasis-Rey-
Schaefer-briefings-Evasion-of-HighEnd-IPS-Devices-wp.pdf>. Schaefer-briefings-Evasion-of-HighEnd-IPS-Devices-wp.pdf>.
[Bonica-NANOG58] [Bonica-NANOG58]
Bonica, R., "IPv6 Extension Headers in the Real World Bonica, R., "IPV6 FRAGMENTATION: The Case For
v2.0", NANOG 58. New Orleans, Louisiana, USA. June 3-5, Deprecation", NANOG 58. New Orleans, Louisiana, USA. June
2013, <https://www.nanog.org/sites/default/files/ 3-5, 2013, <https://www.nanog.org/sites/default/files/
mon.general.fragmentation.bonica.pdf>. mon.general.fragmentation.bonica.pdf>.
[Cisco-EH-Cons] [Cisco-EH-Cons]
Cisco, "IPv6 Extension Headers Review and Considerations", Cisco, "IPv6 Extension Headers Review and Considerations",
October 2006, October 2006,
<http://www.cisco.com/en/US/technologies/tk648/tk872/ <http://www.cisco.com/en/US/technologies/tk648/tk872/
technologies_white_paper0900aecd8054d37d.pdf>. technologies_white_paper0900aecd8054d37d.pdf>.
[Cisco-Frag1]
Cisco, "Cisco IOS Software IPv6 Virtual Fragmentation
Reassembly Denial of Service Vulnerability", September
2013, <http://tools.cisco.com/security/center/content/
CiscoSecurityAdvisory/cisco-sa-20130925-ipv6vfr>.
[Cisco-Frag2]
Cisco, "Cisco IOS XR Software Crafted IPv6 Packet Denial
of Service Vulnerability", June 2015,
<http://tools.cisco.com/security/center/content/
CiscoSecurityAdvisory/cisco-sa-20150611-iosxr>.
[Cunha-2020] [Cunha-2020]
Cunha, I., "IPv4 vs IPv6 load balancing in Internet Cunha, I., "IPv4 vs IPv6 load balancing in Internet
routes", NPS/CAIDA 2020 Virtual IPv6 Workshop, 2020, routes", NPS/CAIDA 2020 Virtual IPv6 Workshop, 2020,
<https://www.cmand.org/workshops/202006-v6/slides/ <https://www.cmand.org/workshops/202006-v6/slides/
cunha.pdf>. cunha.pdf>.
[FreeBSD-SA]
FreeBSD, "FreeBSD Security Advisory FreeBSD-SA-20:24.ipv6:
IPv6 Hop-by-Hop options use-after-free bug", September
2020, <https://www.freebsd.org/security/advisories/
FreeBSD-SA-20:24.ipv6.asc>.
[Gont-Chown-IEPG89] [Gont-Chown-IEPG89]
Gont, F. and T. Chown, "A Small Update on the Use of IPv6 Gont, F. and T. Chown, "A Small Update on the Use of IPv6
Extension Headers", IEPG 89. London, UK. March 2, 2014, Extension Headers", IEPG 89. London, UK. March 2, 2014,
<http://www.iepg.org/2014-03-02-ietf89/fgont-iepg-ietf89- <http://www.iepg.org/2014-03-02-ietf89/fgont-iepg-ietf89-
eh-update.pdf>. eh-update.pdf>.
[Gont-IEPG88] [Gont-IEPG88]
Gont, F., "Fragmentation and Extension header Support in Gont, F., "Fragmentation and Extension header Support in
the IPv6 Internet", IEPG 88. Vancouver, BC, Canada. the IPv6 Internet", IEPG 88. Vancouver, BC, Canada.
November 13, 2013, <http://www.iepg.org/2013-11-ietf88/ November 13, 2013, <http://www.iepg.org/2013-11-ietf88/
skipping to change at page 13, line 11 skipping to change at page 16, line 47
DNS", APNIC Blog, 2017, DNS", APNIC Blog, 2017,
<https://blog.apnic.net/2017/08/22/dealing-ipv6- <https://blog.apnic.net/2017/08/22/dealing-ipv6-
fragmentation-dns/>. fragmentation-dns/>.
[Huston-2020] [Huston-2020]
Huston, G., "Measurement of IPv6 Extension Header Huston, G., "Measurement of IPv6 Extension Header
Support", NPS/CAIDA 2020 Virtual IPv6 Workshop, 2020, Support", NPS/CAIDA 2020 Virtual IPv6 Workshop, 2020,
<https://www.cmand.org/workshops/202006-v6/ <https://www.cmand.org/workshops/202006-v6/
slides/2020-06-16-xtn-hdrs.pdf>. slides/2020-06-16-xtn-hdrs.pdf>.
[I-D.ietf-intarea-frag-fragile]
Bonica, R., Baker, F., Huston, G., Hinden, R., Troan, O.,
and F. Gont, "IP Fragmentation Considered Fragile", draft-
ietf-intarea-frag-fragile-17 (work in progress), September
2019.
[I-D.ietf-opsec-ipv6-eh-filtering] [I-D.ietf-opsec-ipv6-eh-filtering]
Gont, F. and W. LIU, "Recommendations on the Filtering of Gont, F. and W. LIU, "Recommendations on the Filtering of
IPv6 Packets Containing IPv6 Extension Headers", draft- IPv6 Packets Containing IPv6 Extension Headers", draft-
ietf-opsec-ipv6-eh-filtering-06 (work in progress), July ietf-opsec-ipv6-eh-filtering-06 (work in progress), July
2018. 2018.
[I-D.kampanakis-6man-ipv6-eh-parsing] [I-D.kampanakis-6man-ipv6-eh-parsing]
Kampanakis, P., "Implementation Guidelines for parsing Kampanakis, P., "Implementation Guidelines for parsing
IPv6 Extension Headers", draft-kampanakis-6man-ipv6-eh- IPv6 Extension Headers", draft-kampanakis-6man-ipv6-eh-
parsing-01 (work in progress), August 2014. parsing-01 (work in progress), August 2014.
skipping to change at page 14, line 11 skipping to change at page 17, line 40
DNS", APNIC Blog, 2018, DNS", APNIC Blog, 2018,
<https://blog.apnic.net/2018/01/11/ipv6-flow-label-misuse- <https://blog.apnic.net/2018/01/11/ipv6-flow-label-misuse-
hashing/>. hashing/>.
[Linkova-Gont-IEPG90] [Linkova-Gont-IEPG90]
Linkova, J. and F. Gont, "IPv6 Extension Headers in the Linkova, J. and F. Gont, "IPv6 Extension Headers in the
Real World v2.0", IEPG 90. Toronto, ON, Canada. July 20, Real World v2.0", IEPG 90. Toronto, ON, Canada. July 20,
2014, <http://www.iepg.org/2014-07-20-ietf90/iepg- 2014, <http://www.iepg.org/2014-07-20-ietf90/iepg-
ietf90-ipv6-ehs-in-the-real-world-v2.0.pdf>. ietf90-ipv6-ehs-in-the-real-world-v2.0.pdf>.
[nmap] Fyodor, "Dealing with IPv6 fragmentation in the
DNS", Firewall/IDS Evasion and Spoofing,
<https://nmap.org/book/man-bypass-firewalls-ids.html>.
[PMTUD-Blackholes] [PMTUD-Blackholes]
De Boer, M. and J. Bosma, "Discovering Path MTU black De Boer, M. and J. Bosma, "Discovering Path MTU black
holes on the Internet using RIPE Atlas", July 2012, holes on the Internet using RIPE Atlas", July 2012,
<http://www.nlnetlabs.nl/downloads/publications/pmtu- <http://www.nlnetlabs.nl/downloads/publications/pmtu-
black-holes-msc-thesis.pdf>. black-holes-msc-thesis.pdf>.
[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>.
[RFC5575] Marques, P., Sheth, N., Raszuk, R., Greene, B., Mauch, J., [RFC5575] Marques, P., Sheth, N., Raszuk, R., Greene, B., Mauch, J.,
and D. McPherson, "Dissemination of Flow Specification and D. McPherson, "Dissemination of Flow Specification
Rules", RFC 5575, DOI 10.17487/RFC5575, August 2009, Rules", RFC 5575, DOI 10.17487/RFC5575, August 2009,
<https://www.rfc-editor.org/info/rfc5575>. <https://www.rfc-editor.org/info/rfc5575>.
[RFC5635] Kumari, W. and D. McPherson, "Remote Triggered Black Hole [RFC5635] Kumari, W. and D. McPherson, "Remote Triggered Black Hole
Filtering with Unicast Reverse Path Forwarding (uRPF)", Filtering with Unicast Reverse Path Forwarding (uRPF)",
RFC 5635, DOI 10.17487/RFC5635, August 2009, RFC 5635, DOI 10.17487/RFC5635, August 2009,
<https://www.rfc-editor.org/info/rfc5635>. <https://www.rfc-editor.org/info/rfc5635>.
skipping to change at page 15, line 15 skipping to change at page 18, line 49
[RFC7739] Gont, F., "Security Implications of Predictable Fragment [RFC7739] Gont, F., "Security Implications of Predictable Fragment
Identification Values", RFC 7739, DOI 10.17487/RFC7739, Identification Values", RFC 7739, DOI 10.17487/RFC7739,
February 2016, <https://www.rfc-editor.org/info/rfc7739>. February 2016, <https://www.rfc-editor.org/info/rfc7739>.
[RFC7872] Gont, F., Linkova, J., Chown, T., and W. Liu, [RFC7872] Gont, F., Linkova, J., Chown, T., and W. Liu,
"Observations on the Dropping of Packets with IPv6 "Observations on the Dropping of Packets with IPv6
Extension Headers in the Real World", RFC 7872, Extension Headers in the Real World", RFC 7872,
DOI 10.17487/RFC7872, June 2016, DOI 10.17487/RFC7872, June 2016,
<https://www.rfc-editor.org/info/rfc7872>. <https://www.rfc-editor.org/info/rfc7872>.
[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>.
[Zack-FW-Benchmark] [Zack-FW-Benchmark]
Zack, E., "Firewall Security Assessment and Benchmarking Zack, E., "Firewall Security Assessment and Benchmarking
IPv6 Firewall Load Tests", IPv6 Hackers Meeting #1, IPv6 Firewall Load Tests", IPv6 Hackers Meeting #1,
Berlin, Germany. June 30, 2013, Berlin, Germany. June 30, 2013,
<http://www.ipv6hackers.org/meetings/ipv6-hackers-1/zack- <https://www.ipv6hackers.org/files/meetings/ipv6-hackers-
ipv6hackers1-firewall-security-assessment-and- 1/zack-ipv6hackers1-firewall-security-assessment-and-
benchmarking.pdf>. benchmarking.pdf>.
Authors' Addresses Authors' Addresses
Fernando Gont Fernando Gont
SI6 Networks SI6 Networks
Segurola y Habana 4310, 7mo Piso Segurola y Habana 4310, 7mo Piso
Villa Devoto, Ciudad Autonoma de Buenos Aires Villa Devoto, Ciudad Autonoma de Buenos Aires
Argentina Argentina
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