< draft-ietf-v6ops-ipv6-ehs-packet-drops-06.txt   draft-ietf-v6ops-ipv6-ehs-packet-drops-07.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: October 10, 2021 INEX Expires: December 11, 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
April 8, 2021 June 9, 2021
Operational Implications of IPv6 Packets with Extension Headers Operational Implications of IPv6 Packets with Extension Headers
draft-ietf-v6ops-ipv6-ehs-packet-drops-06 draft-ietf-v6ops-ipv6-ehs-packet-drops-07
Abstract Abstract
This document summarizes the operational implications of IPv6 This document summarizes the operational implications of IPv6
extension headers specified in the IPv6 protocol specification extension headers specified in the IPv6 protocol specification
(RFC8200), and attempts to analyze reasons why packets with IPv6 (RFC8200), and attempts to analyze reasons why packets with IPv6
extension headers are often dropped in the public Internet. extension headers are often dropped in the public Internet.
Status of This Memo Status of This Memo
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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 October 10, 2021. This Internet-Draft will expire on December 11, 2021.
Copyright Notice Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Disclaimer . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Background Information . . . . . . . . . . . . . . . . . . . 3 3. Disclaimer . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Previous Work on IPv6 Extension Headers . . . . . . . . . . . 5 4. Background Information . . . . . . . . . . . . . . . . . . . 3
5. Packet Forwarding Engine Constraints . . . . . . . . . . . . 7 5. Previous Work on IPv6 Extension Headers . . . . . . . . . . . 5
5.1. Recirculation . . . . . . . . . . . . . . . . . . . . . . 8 6. Packet Forwarding Engine Constraints . . . . . . . . . . . . 7
6. Requirement to Process Layer-3/layer-4 information in 6.1. Recirculation . . . . . . . . . . . . . . . . . . . . . . 8
7. Requirement to Process Layer-3/layer-4 information in
Intermediate Systems . . . . . . . . . . . . . . . . . . . . 8 Intermediate Systems . . . . . . . . . . . . . . . . . . . . 8
6.1. ECMP and Hash-based Load-Sharing . . . . . . . . . . . . 8 7.1. ECMP and Hash-based Load-Sharing . . . . . . . . . . . . 8
6.2. Enforcing infrastructure ACLs . . . . . . . . . . . . . . 9 7.2. Enforcing infrastructure ACLs . . . . . . . . . . . . . . 9
6.3. DDoS Management and Customer Requests for Filtering . . . 9 7.3. DDoS Management and Customer Requests for Filtering . . . 10
6.4. Network Intrusion Detection and Prevention . . . . . . . 10 7.4. Network Intrusion Detection and Prevention . . . . . . . 10
6.5. Firewalling . . . . . . . . . . . . . . . . . . . . . . . 10 7.5. Firewalling . . . . . . . . . . . . . . . . . . . . . . . 11
7. Operational Implications . . . . . . . . . . . . . . . . . . 11 8. Operational and Security Implications . . . . . . . . . . . . 12
7.1. Inability to Find Layer-4 Information . . . . . . . . . . 11 8.1. Inability to Find Layer-4 Information . . . . . . . . . . 12
7.2. Route-Processor Protection . . . . . . . . . . . . . . . 11 8.2. Route-Processor Protection . . . . . . . . . . . . . . . 12
7.3. Inability to Perform Fine-grained Filtering . . . . . . . 12 8.3. Inability to Perform Fine-grained Filtering . . . . . . . 12
7.4. Security Concerns Associated with IPv6 Extension Headers 12 8.4. Security Concerns Associated with IPv6 Extension Headers 12
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
9. Security Considerations . . . . . . . . . . . . . . . . . . . 13 10. Security Considerations . . . . . . . . . . . . . . . . . . . 14
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 14 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 14
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 14 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
11.1. Normative References . . . . . . . . . . . . . . . . . . 14 12.1. Normative References . . . . . . . . . . . . . . . . . . 14
11.2. Informative References . . . . . . . . . . . . . . . . . 15 12.2. Informative References . . . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19 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 are middle-boxes, and evidence exists that IPv6 packets with EHs are
intentionally dropped in the public Internet in some network intentionally dropped in the public Internet in some circumstances.
deployments.
This document has the following goals: This document has the following goals:
o Raise awareness about the operational and security implications of o Raise awareness about the operational and security implications of
IPv6 Extension Headers specified in [RFC8200], and present reasons IPv6 Extension Headers specified in [RFC8200], and present reasons
why some networks resort to intentionally dropping packets why some networks resort to intentionally dropping packets
containing IPv6 Extension Headers. 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 provides background information about the IPv6 packet Section 4 provides background information about the IPv6 packet
structure and associated implications. Section 4 of this document structure and associated implications. Section 5 of this document
summarizes the previous work that has been carried out in the area of summarizes the previous work that has been carried out in the area of
IPv6 extension headers. Section 5 discusses packet forwarding engine IPv6 extension headers. Section 6 discusses packet forwarding engine
constraints in contemporary routers. Section 6 discusses why constraints in contemporary routers. Section 7 discusses why
contemporary routers and middle-boxes may need to access Layer-4 intermediate systems may need to access Layer-4 information to make a
information to make a forwarding decision. Finally, Section 7 forwarding decision. Finally, Section 8 discusses the operational
discusses the operational implications of IPv6 EHs. implications of IPv6 EHs.
2. Disclaimer 2. Terminology
This document uses the term "intermediate system" to describe both
routers and middle-boxes, when there is no need to distinguish
between the two and where the important issue is that the device
being discussed forwards packets.
3. 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 why these packets are often dropped in the public operational reasons why these packets are often dropped in the 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 currently dropped. packets, but rather an analysis of why they are currently dropped.
3. Background Information 4. Background Information
It is useful to compare the basic structure of IPv6 packets against It is useful to compare the basic structure of IPv6 packets against
that of IPv4 packets, and analyze the implications of the two that of IPv4 packets, and analyze the implications of the two
different packet structures. different packet structures.
IPv4 packets have a variable-length header size, that allows for the IPv4 packets have a variable-length header size, that allows for the
use of IPv4 "options" -- optional information that may be of use by use of IPv4 "options" -- optional information that may be of use by
nodes processing IPv4 packets. The IPv4 header length is specified nodes processing IPv4 packets. The IPv4 header length is specified
in the IHL header field of the mandatory IPv4 header, and must be in 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 the range from 20 octets (the minimum IPv4 header size) to 60 octets
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Figure 1: IPv4 Packet Structure Figure 1: IPv4 Packet Structure
IPv6 took a different approach to the IPv6 packet structure. Rather IPv6 took a different approach to the IPv6 packet structure. Rather
than employing a variable-length header as IPv4 does, IPv6 employs a than employing a variable-length header as IPv4 does, IPv6 employs a
linked-list-like packet structure, where a mandatory fixed-length linked-list-like packet structure, where a mandatory fixed-length
IPv6 header is followed by an arbitrary number of optional extension IPv6 header is followed by an arbitrary number of optional extension
headers, with the upper-layer header being the last header in the headers, with the upper-layer header being the last header in the
IPv6 header chain. Each extension header typically specifies its IPv6 header chain. Each extension header typically specifies its
length (unless it is implicit from the extension header type), and length (unless it is implicit from the extension header type), and
the "next header" type that follows in the IPv6 IPv6 header chain. the "next header" type that follows in the IPv6 header chain.
NH NH, EH-length NH, EH-length NH NH, EH-length NH, EH-length
+-------+ +------+ +-------+ +-------+ +------+ +-------+
| | | | | | | | | | | |
| v | v | v | v | v | v
+-------------+-------------+-//-+---------------+--------------+ +-------------+-------------+-//-+---------------+--------------+
| | | | | | | | | | | |
| IPv6 | Ext. | | Ext. | Upper-Layer | | IPv6 | Ext. | | Ext. | Upper-Layer |
| header | Header | | Header | Protocol | | header | Header | | Header | Protocol |
| | | | | | | | | | | |
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the number of IPv6 EHs that may be present in a packet. the number of IPv6 EHs that may be present in a packet.
Therefore, there is no upper-limit regarding "how deep into the Therefore, there is no upper-limit regarding "how deep into the
IPv6 packet" the upper-layer may be found. IPv6 packet" the upper-layer may be found.
o The only way for a node to obtain the upper-layer protocol type or 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 find the upper-layer protocol header is to parse and process the
entire IPv6 header chain, in sequence, starting from the mandatory entire IPv6 header chain, in sequence, starting from the mandatory
IPv6 header, until the last header in the IPv6 header chain is IPv6 header, until the last header in the IPv6 header chain is
found. found.
4. Previous Work on IPv6 Extension Headers 5. Previous Work on IPv6 Extension Headers
Some of the operational implications of IPv6 Extension Headers have Some of the operational and security implications of IPv6 Extension
been discussed at the IETF: Headers have been discussed at the IETF:
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.
o [I-D.kampanakis-6man-ipv6-eh-parsing] describes how o [I-D.kampanakis-6man-ipv6-eh-parsing] describes how
inconsistencies in the way IPv6 packets with extension headers are inconsistencies in the way IPv6 packets with extension headers are
parsed by different implementations could result in evasion of parsed by different implementations could result in evasion of
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o [PMTUD-Blackholes] and [Linkova-Gont-IEPG90] presented some o [PMTUD-Blackholes] and [Linkova-Gont-IEPG90] presented some
preliminary measurements regarding the extent to which packet preliminary measurements regarding the extent to which packet
containing IPv6 EHs are dropped in the public Internet. containing IPv6 EHs are dropped in the public Internet.
o [RFC7872] presents more comprehensive results and documents the o [RFC7872] presents more comprehensive results and documents the
methodology used to obtain these results. methodology used to obtain these 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.
5. Packet Forwarding Engine Constraints 6. Packet Forwarding Engine Constraints
Most contemporary carrier-grade routers use dedicated hardware (e.g., Most contemporary carrier-grade routers use dedicated hardware, e.g.
ASICs or NPUs) to determine how to forward packets across their application-specific integrated circuits (ASICs) or network
internal fabrics (see [IEPG94-Scudder] and [APNIC-Scudder] for processing units (NPUs), to determine how to forward packets across
their internal fabrics (see [IEPG94-Scudder] and [APNIC-Scudder] for
details). One of the common methods of handling next-hop lookup is details). One of the common methods of handling next-hop lookup is
to send a small portion of the ingress packet to a lookup engine with to send a small portion of the ingress packet to a lookup engine with
specialised hardware (e.g., ternary CAM or Reduced Latency DRAM) to specialised hardware, e.g. ternary content-addressable memory (TCAM)
or reduced latency dynamic random-access memory (RLDRAM), to
determine the packet's next-hop. Technical constraints mean that determine the packet's next-hop. Technical constraints mean that
there is a trade-off between the amount of data sent to the lookup there is a trade-off between the amount of data sent to the lookup
engine and the overall packet forwarding rate of the lookup engine. engine and the overall packet forwarding rate of the lookup engine.
If more data is sent, the lookup engine can inspect further into the If more data is sent, the lookup engine can inspect further into the
packet, but the overall packet forwarding rate of the system will be packet, but the overall packet forwarding rate of the system will be
reduced. If less data is sent, the overall packet forwarding rate of reduced. If less data is sent, the overall packet forwarding rate of
the router will be increased but the packet lookup engine may not be the router will be increased but the packet lookup engine may not be
able to inspect far enough into a packet to determine how it should able to inspect far enough into a packet to determine how it should
be handled. be handled.
NOTE: NOTE:
For example, some contemporary high-end routers are known to For example, some contemporary high-end routers are known to
inspect up to 192 bytes, while others are known to parse up to 384 inspect up to 192 bytes, while others are known to parse up to 384
bytes of header. bytes of header.
If a hardware forwarding engine on a contemporary router cannot make If a hardware forwarding engine on a contemporary router cannot make
a 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. Section 6 discusses some of the reasons for which a the packet. Section 7 discusses some of the reasons for which a
contemporary router might need to access layer-4 information to make contemporary router might need to access layer-4 information to make
a forwarding decision. a forwarding 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 contemporary router architectures as a result of unfeasible on most contemporary router architectures as a result of
the vast difference between the hardware forwarding capacity of the 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. Other platforms may have a separate software forwarding plane. Other platforms may have a separate software
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plane and the control plane. However, the limited CPU resources of plane and the control plane. However, the limited CPU resources of
this software-based forwarding plane, as well as the limited this software-based forwarding plane, as well as the limited
bandwidth of the associated link results in similar throughput bandwidth of the associated link results in similar throughput
constraints. constraints.
If an IPv6 header chain is sufficiently long that it exceeds the If an IPv6 header chain is sufficiently long that it exceeds the
packet look-up capacity of the router, the router might be unable to packet look-up capacity of the router, the router might be unable to
determine how the packet should be handled, and thus could resort to determine how the packet should be handled, and thus could resort to
dropping the packet. dropping the packet.
5.1. Recirculation 6.1. Recirculation
Although TLV chains are amenable to iterative processing on Although TLV chains are amenable to iterative processing on
architectures that have packet look-up engines with deep inspection architectures that have packet look-up engines with deep inspection
capabilities, some packet forwarding engines manage IPv6 Extension capabilities, some packet forwarding engines manage IPv6 Extension
Header chains using recirculation. This approach processes Extension Header chains using recirculation. This approach processes Extension
Headers one at a time: when processing on one Extension Header is Headers one at a time: when processing on one Extension Header is
completed, the packet is looped back through the processing engine completed, the packet is looped back through the processing engine
again. This recirculation process continues repeatedly until there again. This recirculation process continues repeatedly until there
are no more Extension Headers left to be processed. are no more Extension Headers left to be processed.
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limited look-up capability, because it allows arbitrarily long header limited look-up capability, because it allows arbitrarily long header
chains to be processed without the complexity and cost associated chains to be processed without the complexity and cost associated
with packet forwarding engines which have deep look-up capabilities. with packet forwarding engines which have deep look-up capabilities.
However, recirculation can impact the forwarding capacity of However, recirculation can impact the forwarding capacity of
hardware, as each packet will pass through the processing engine hardware, as each packet will pass through the processing engine
multiple times. Depending on configuration, the type of packets multiple times. Depending on configuration, the type of packets
being processed, and the hardware capabilities of the packet being processed, and the hardware capabilities of the packet
forwarding engine, this could impact data-plane throughput forwarding engine, this could impact data-plane throughput
performance on the router. performance on the router.
6. Requirement to Process Layer-3/layer-4 information in Intermediate 7. Requirement to Process Layer-3/layer-4 information in Intermediate
Systems Systems
The following subsections discuss some of the reasons for which The following subsections discuss some of the reasons for which
contemporary routers and middle-boxes may need to process Layer-3/ intermediate systems may need to process Layer-3/layer-4 information
layer-4 information to make a forwarding decision. to make a forwarding decision.
6.1. ECMP and Hash-based Load-Sharing 7.1. ECMP and Hash-based Load-Sharing
In the case of ECMP (equal cost multi path) load sharing, the router In the case of equal cost multi-path (ECMP) load sharing, the
on the sending side of the link needs to make a decision regarding intermediate system needs to make a decision regarding which of its
which of the links to use to forward a given packet. Since round- interfaces to use to forward a given packet. Since round-robin usage
robin usage of the links is usually avoided to prevent packet of the links is usually avoided to prevent packet reordering,
reordering, forwarding engines need to use a mechanism that will forwarding engines need to use a mechanism that will consistently
consistently forward the same data streams down the same forwarding forward the same data streams down the same forwarding paths. Most
paths. Most forwarding engines achieve this by calculating a simple forwarding engines achieve this by calculating a simple hash using an
hash using an n-tuple gleaned from a combination of layer-2 through n-tuple gleaned from a combination of layer-2 through to layer-4
to layer-4 packet header information. This n-tuple will typically packet header information. This n-tuple will typically use the src/
use the src/dst MAC address, src/dst IP address, and if possible dst MAC address, src/dst IP address, and if possible further layer-4
further layer-4 src/dst port information. src/dst port information.
In the IPv6 world, flows are expected to be identified by means of In the IPv6 world, flows are expected to be identified by means of
the IPv6 Flow Label [RFC6437]. Thus, ECMP and Hash-based Load- the IPv6 Flow Label [RFC6437]. Thus, ECMP and Hash-based Load-
Sharing should be possible without the need to process the entire Sharing should be possible without the need to process the entire
IPv6 header chain to obtain upper-layer information to identify IPv6 header chain to obtain upper-layer information to identify
flows. [RFC7098] discusses how the IPv6 Flow Label can be used to flows. [RFC7098] discusses how the IPv6 Flow Label can used to
enhance layer 3/4 load distribution and balancing for large server enhance layer 3/4 load distribution and balancing for large server
farms. farms.
Historically, many IPv6 implementations failed to set the Flow Label, Historically, many IPv6 implementations failed to set the Flow Label,
and hash-based ECMP/load-sharing devices also did not employ the Flow and hash-based ECMP/load-sharing devices also did not employ the Flow
Label for performing their task. While support of [RFC6437] is Label for performing their task. While support of [RFC6437] is
currently widespread for current versions of all popular host currently widespread for current versions of all popular host
implementations, there is still only marginal usage of the IPv6 Flow implementations, there is still only marginal usage of the IPv6 Flow
Label for ECMP and load balancing [Cunha-2020]. A contributing Label for ECMP and load balancing [Cunha-2020]. A contributing
factor could be the issues that have been found in host factor could be the issues that have been found in host
implementations and middle-boxes [Jaeggli-2018]. implementations and middle-boxes [Jaeggli-2018].
Clearly, widespread support of [RFC6437] would relieve middle-boxes Clearly, widespread support of [RFC6437] would relieve intermediate
from having to process the entire IPv6 header chain, making Flow systems from having to process the entire IPv6 header chain, making
Label-based ECMP and Load-Sharing [RFC6438] feasible. Flow Label-based ECMP and Load-Sharing [RFC6438] feasible.
6.2. Enforcing infrastructure ACLs If an intermediate system cannot determine consistent n-tuples for
calculating flow hashes, data streams are more likely to end up being
distributed unequally across ECMP and load-shared links. This may
lead to packet drops or reduced performance.
7.2. Enforcing infrastructure ACLs
Infrastructure ACLs (iACLs) drop unwanted packets destined to a Infrastructure ACLs (iACLs) drop unwanted packets destined to a
network's infrastructure IP addresses. Typically, iACLs are deployed network's infrastructure. Typically, iACLs are deployed because
because external direct access to a network's infrastructure external direct access to a network's infrastructure addresses is
addresses is operationally unnecessary, and can be used for attacks operationally unnecessary, and can be used for attacks of different
of different sorts against router control planes. To this end, sorts against router control planes. To this end, traffic usually
traffic usually needs to be differentiated on the basis of layer-3 or needs to be differentiated on the basis of layer-3 or layer-4
layer-4 criteria to achieve a useful balance of protection and criteria to achieve a useful balance of protection and functionality.
functionality. For example, an infrastructure may be configured with For example, an infrastructure may be configured with the following
the following policy: policy:
o Permit some amount of ICMP echo (ping) traffic towards a router's o Permit some amount of ICMP echo (ping) traffic towards a 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.
6.3. DDoS Management and Customer Requests for Filtering If a forwarding router cannot determine consistent n-tuples for
calculating flow hashes, data streams are more likely to end up being
distributed unequally across ECMP and load-shared links. This may
lead to packet drops or reduced performance.
If a network cannot deploy infrastructure ACLs, then the security of
the network may be compromised due to having more potential attack
vectors open.
7.3. 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 iACL protection. protection filters is similar in nature to the iACL protection.
Similar to iACL protection, layer-4 ACLs generally need to be applied Similar to iACL protection, layer-4 ACLs generally need to be applied
as close to the edge of the network as possible, even though the as close to the edge of the network as possible, even though the
intent is usually to protect the customer edge rather than the intent is usually to protect the customer edge rather than the
provider core. Application of layer-4 DDoS protection to a network provider core. Application of layer-4 DDoS protection to a network
edge is often automated using Flowspec [RFC5575]. edge is often automated using Flowspec [RFC5575].
For example, a web site that normally only handled traffic on TCP For example, a web site that normally only handled traffic on TCP
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.
6.4. Network Intrusion Detection and Prevention 7.4. Network Intrusion Detection and Prevention
Network Intrusion Detection Systems (NIDS) examine network traffic Network Intrusion Detection Systems (NIDS) examine network traffic
and try to identify traffic patterns that can be correlated to and try to identify traffic patterns that can be correlated to
network-based attacks. These systems generally inspect application- network-based attacks. These systems generally inspect application-
layer traffic (if possible), but at the bare minimum inspect layer-4 layer traffic (if possible), but at the bare minimum inspect layer-4
flows. When attack activity is inferred, the operator is notified of flows. When attack activity is inferred, the operator is notified of
the potential intrusion attempt. the potential intrusion attempt.
Network Intrusion Prevention Systems (IPS) operate similarly to Network Intrusion Prevention Systems (IPS) operate similarly to
NIDS's, but they can also prevent intrusions by reacting to detected NIDS's, but they can also prevent intrusions by reacting to detected
skipping to change at page 10, line 44 skipping to change at page 11, line 14
o Use of IPv6 fragmentation requires a stateful fragment-reassembly o Use of IPv6 fragmentation requires a stateful fragment-reassembly
operation, even for decoy traffic employing forged source operation, even for decoy traffic employing forged source
addresses (see e.g., [nmap]). addresses (see e.g., [nmap]).
As a result, in order to increase the efficiency or effectiveness of As a result, in order to increase the efficiency or effectiveness of
these systems, packets employing IPv6 extension headers are often these systems, packets employing IPv6 extension headers are often
dropped at the network ingress point(s) of networks that deploy these dropped at the network ingress point(s) of networks that deploy these
systems. systems.
6.5. Firewalling 7.5. Firewalling
Firewalls enforce security policies by means of packet filtering. Firewalls enforce security policies by means of packet filtering.
These systems usually inspect layer-3 and layer-4 traffic, but can These systems usually inspect layer-3 and layer-4 traffic, but can
often also examine application-layer traffic flows. often also examine application-layer traffic flows.
As with NIDS/IPS (Section 6.4), use of IPv6 extension headers can As with NIDS/IPS (Section 7.4), use of IPv6 extension headers can
represent a challenge to network firewalls, since: represent a challenge to network firewalls, since:
o Extension headers increase the complexity of resulting traffic, o Extension headers increase the complexity of resulting traffic,
and the associated work and system requirements to process it (see and the associated work and system requirements to process it, as
e.g., [Zack-FW-Benchmark]). outlined in [Zack-FW-Benchmark].
o Use of unknown extension headers can prevent firewalls from o Use of unknown extension headers can prevent firewalls from
processing layer-4 information. processing layer-4 information.
o Use of IPv6 fragmentation requires a stateful fragment-reassembly o Use of IPv6 fragmentation requires a stateful fragment-reassembly
operation, even for decoy traffic employing forged source operation, even for decoy traffic employing forged source
addresses (see e.g., [nmap]). addresses (see e.g., [nmap]).
Additionally, a common firewall filtering policy is the so-called Additionally, a common firewall filtering policy is the so-called
"default deny", where all traffic is blocked (by default), and only "default deny", where all traffic is blocked (by default), and only
expected traffic is added to an "allow/accept list". expected traffic is added to an "allow/accept list".
As a result, packets employing IPv6 extension headers are often As a result, packets employing IPv6 extension headers are often
dropped by network firewalls, either because of the challenges dropped by network firewalls, either because of the challenges
represented by extension headers or because the use of IPv6 extension represented by extension headers or because the use of IPv6 extension
headers has not been explicitly allowed. headers has not been explicitly allowed.
7. Operational Implications Note that although the data presented in [Zack-FW-Benchmark] were
several years old at the time of publication of this document, many
contemporary firewalls use comparable hardware and software
architecture, and consequently the conclusions of this benchmark are
still relevant, despite its age.
7.1. Inability to Find Layer-4 Information 8. Operational and Security Implications
As discussed in Section 6, routers and middle-boxes that need to find 8.1. Inability to Find Layer-4 Information
the layer-4 header must process the entire IPv6 extension header
chain. When such devices are unable to obtain the required
information, the forwarding device has the option to drop the packet
unconditionally, forward the packet unconditionally, or process the
packet outside the normal forwarding path. Forwarding packets
unconditionally will usually allow for the circumvention of security
controls (see e.g., Section 6.5), while processing packets outside of
the normal forwarding path will usually open the door to DoS attacks
(see e.g., Section 5). Thus, in these scenarios, devices often
simply resort to dropping such packets unconditionally.
7.2. Route-Processor Protection As discussed in Section 7, intermediate systems 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, the
forwarding device has the option to drop the packet unconditionally,
forward the packet unconditionally, or process the packet outside the
normal forwarding path. Forwarding packets unconditionally will
usually allow for the circumvention of security controls (see e.g.,
Section 7.5), while processing packets outside of the normal
forwarding path will usually open the door to DoS attacks (see e.g.,
Section 6). Thus, in these scenarios, devices often simply resort to
dropping such packets unconditionally.
8.2. Route-Processor Protection
Most contemporary carrier-grade routers have a fast hardware-assisted Most contemporary carrier-grade routers have a fast hardware-assisted
forwarding plane and a loosely coupled control plane, connected forwarding plane and a loosely coupled control plane, connected
together with a link that has much less capacity than the forwarding together with a link that has much less capacity than the forwarding
plane could handle. Traffic differentiation cannot be performed by plane could handle. Traffic differentiation cannot be performed by
the control plane, because this would overload the internal link the control plane, because this would overload the internal link
connecting the forwarding plane to the control plane. connecting the forwarding plane to the control plane.
The Hop-by-Hop Options header has been particularly challenging since The Hop-by-Hop Options header has been particularly challenging since
in most circumstances, the corresponding packet is punted to the in most circumstances, the corresponding packet is punted to the
control plane for processing. As a result, many operators currently control plane for processing. As a result, many operators drop IPv6
drop IPv6 packets containing this extension header. [RFC6192] packets containing this extension header [RFC7872]. [RFC6192]
provides advice regarding protection of a router's control plane. provides advice regarding protection of a router's control plane.
7.3. Inability to Perform Fine-grained Filtering 8.3. Inability to Perform Fine-grained Filtering
Some router implementations do not have support for fine-grained Some intermediate systems do not have support for fine-grained
filtering of IPv6 extension headers. For example, an operator that filtering of IPv6 extension headers. For example, an operator that
wishes to drop packets containing Routing Header Type 0 (RHT0), may wishes to drop packets containing Routing Header Type 0 (RHT0), may
only be able to filter on the extension header type (Routing Header). only be able to filter on the extension header type (Routing Header).
This could result in an operator enforcing a more coarse filtering This could result in an operator enforcing a more coarse filtering
policy (e.g., "drop all packets containing a Routing Header" vs. policy (e.g., "drop all packets containing a Routing Header" vs.
"only drop packets that contain a Routing Header Type 0"). "only drop packets that contain a Routing Header Type 0").
7.4. Security Concerns Associated with IPv6 Extension Headers 8.4. 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
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.
This can represent a challenge for devices that need to find this This can represent a challenge for devices that need to find this
skipping to change at page 12, line 48 skipping to change at page 13, line 28
protocol type) can be trivially circumvented by inserting IPv6 protocol type) can be trivially circumvented by inserting IPv6
Extension Headers between the main IPv6 header and the upper layer Extension Headers between the main IPv6 header and the upper layer
protocol. [RFC7113] describes this issue for the RA-Guard case, but protocol. [RFC7113] describes this issue for the RA-Guard case, but
the same techniques could be employed to circumvent other IPv6 the same techniques could be employed to circumvent other IPv6
firewall and packet filtering mechanisms. Additionally, firewall and packet filtering mechanisms. Additionally,
implementation inconsistencies in packet forwarding engines can implementation inconsistencies in packet forwarding engines can
result in evasion of security controls result in evasion of security controls
[I-D.kampanakis-6man-ipv6-eh-parsing] [Atlasis2014] [BH-EU-2014]. [I-D.kampanakis-6man-ipv6-eh-parsing] [Atlasis2014] [BH-EU-2014].
Sometimes packets with IPv6 Extension Headers can impact throughput Sometimes packets with IPv6 Extension Headers can impact throughput
performance on routers and middleboxes. Unless appropriate performance on intermediate systems. Unless appropriate mitigations
mitigations are put in place (e.g., packet dropping and/or rate- are put in place (e.g., packet dropping and/or rate-limiting), an
limiting), an attacker could simply send a large amount of IPv6 attacker could simply send a large amount of IPv6 traffic employing
traffic employing IPv6 Extension Headers with the purpose of IPv6 Extension Headers with the purpose of performing a Denial of
performing a Denial of Service (DoS) attack (see Section 7 for Service (DoS) attack (see Section 6.1 and Section 8 for further
further details). 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, to be Options header might go through the slow forwarding path, to be
processed by the router's CPU. Alternatively, a router configured processed by the router's CPU. Alternatively, a router configured
to enforce an ACL based on upper-layer information (e.g., upper to enforce an ACL based on upper-layer information (e.g., upper
layer protocol or TCP Destination Port) may need to process the layer protocol or TCP Destination Port) may need to process the
entire IPv6 header chain in order to find the required entire IPv6 header chain in order to find the required
information, thereby causing the packet to be processed in the information, thereby causing the packet to be processed in the
slow path [Cisco-EH-Cons]. We note that, for obvious reasons, the slow path [Cisco-EH-Cons]. We note that, for obvious reasons, the
aforementioned performance issues can affect other devices such as aforementioned performance issues can affect other devices such as
firewalls, Network Intrusion Detection Systems (NIDS), etc. firewalls, Network Intrusion Detection Systems (NIDS), etc.
[Zack-FW-Benchmark]. The extent to which performance is affected [Zack-FW-Benchmark]. The extent to which performance is affected
on these devices is implementation-dependent. on these devices is implementation-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 (see e.g., [Cisco-Frag1], Header processing continue to be discovered (see e.g., [Cisco-Frag],
[Cisco-Frag2], [Microsoft-SA], and [FreeBSD-SA]). Because there is [Microsoft-SA], and [FreeBSD-SA]). Because there is currently little
currently little operational reliance on IPv6 Extension headers, the operational reliance on IPv6 Extension headers, the corresponding
corresponding code paths are rarely exercised, and there is the code paths are rarely exercised, and there is the potential for bugs
potential for bugs that still remain to be discovered in some that still remain to be discovered in some implementations.
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]).
8. IANA Considerations 9. IANA Considerations
This document has no IANA actions. This document has no IANA actions.
9. Security Considerations 10. Security Considerations
The security implications of IPv6 extension headers are discussed in The security implications of IPv6 extension headers are discussed in
Section 7.4. This document does not introduce any new security Section 8.4. This document does not introduce any new security
issues. issues.
10. Acknowledgements 11. Acknowledgements
The authors would like to thank (in alphabetical order) Mikael The authors would like to thank (in alphabetical order) Mikael
Abrahamsson, Fred Baker, Dale W. Carder, Brian Carpenter, Tim Chown, Abrahamsson, Fred Baker, Dale W. Carder, Brian Carpenter, Tim Chown,
Owen DeLong, Gorry Fairhurst, Guillermo Gont, Tom Herbert, Lee Owen DeLong, Gorry Fairhurst, Guillermo Gont, Tom Herbert, Lee
Howard, Tom Petch, Sander Steffann, Eduard Vasilenko, Eric Vyncke, Howard, Tom Petch, Sander Steffann, Eduard Vasilenko, Eric Vyncke,
Rob Wilton, Jingrong Xie, and Andrew Yourtchenko, for providing Rob Wilton, Jingrong Xie, and Andrew Yourtchenko, for providing
valuable comments 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
<https://go6lab.si/>, Jared Mauch, and Sander Steffann <https://go6lab.si/>, Jared Mauch, and Sander Steffann
<https://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.
11. References 12. References
11.1. Normative References 12.1. Normative References
[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 15, line 14 skipping to change at page 15, line 37
[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>.
11.2. Informative References 12.2. 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 16, line 5 skipping to change at page 16, line 29
Deprecation", NANOG 58. New Orleans, Louisiana, USA. June Deprecation", NANOG 58. New Orleans, Louisiana, USA. June
3-5, 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-Frag]
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 Cisco, "Cisco IOS XR Software Crafted IPv6 Packet Denial
of Service Vulnerability", June 2015, of Service Vulnerability", June 2015,
<http://tools.cisco.com/security/center/content/ <http://tools.cisco.com/security/center/content/
CiscoSecurityAdvisory/cisco-sa-20150611-iosxr>. 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>.
skipping to change at page 16, line 42 skipping to change at page 17, line 12
<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-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 at Transit IPv6 Packets Containing IPv6 Extension Headers at Transit
Routers", draft-ietf-opsec-ipv6-eh-filtering-07 (work in Routers", draft-ietf-opsec-ipv6-eh-filtering-07 (work in
progress), January 2021. progress), January 2021.
[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.
[I-D.taylor-v6ops-fragdrop] [I-D.taylor-v6ops-fragdrop]
Jaeggli, J., Colitti, L., Kumari, W., Vyncke, E., Kaeo, Jaeggli, J., Colitti, L., Kumari, W., Vyncke, E., Kaeo,
M., and T. Taylor, "Why Operators Filter Fragments and M., and T. Taylor, "Why Operators Filter Fragments and
What It Implies", draft-taylor-v6ops-fragdrop-02 (work in What It Implies", draft-taylor-v6ops-fragdrop-02 (work in
progress), December 2013. progress), December 2013.
[I-D.wkumari-long-headers] [I-D.wkumari-long-headers]
Kumari, W., Jaeggli, J., Bonica, R., and J. Linkova, Kumari, W., Jaeggli, J., Bonica, R. P., and J. Linkova,
"Operational Issues Associated With Long IPv6 Header "Operational Issues Associated With Long IPv6 Header
Chains", draft-wkumari-long-headers-03 (work in progress), Chains", draft-wkumari-long-headers-03 (work in progress),
June 2015. June 2015.
[IEPG94-Scudder] [IEPG94-Scudder]
Petersen, B. and J. Scudder, "Modern Router Architecture Petersen, B. and J. Scudder, "Modern Router Architecture
for Protocol Designers", IEPG 94. Yokohama, Japan. for Protocol Designers", IEPG 94. Yokohama, Japan.
November 1, 2015, <http://www.iepg.org/2015-11-01-ietf94/ November 1, 2015, <http://www.iepg.org/2015-11-01-ietf94/
IEPG-RouterArchitecture-jgs.pdf>. IEPG-RouterArchitecture-jgs.pdf>.
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