Internet DRAFT - draft-ietf-6man-hbh-header-handling
draft-ietf-6man-hbh-header-handling
IPv6 Maintenance F. Baker
Internet-Draft Cisco Systems
Updates: 2460,7045 (if approved) R. Bonica
Intended status: Standards Track Juniper Networks
Expires: September 17, 2016 March 16, 2016
IPv6 Hop-by-Hop Options Extension Header
draft-ietf-6man-hbh-header-handling-03
Abstract
This document clarifies requirements for IPv6 routers with respect to
the Hop-by-Hop (HBH) Options Extension Header. These requirements
are applicable to all IPv6 routers, regardless of whether they
maintain a strict separation between forwarding and control plane
hardware. In this respect, this document updates RFC 2460 and RFC
7045.
This document also describes forwarding plane procedures for
processing the HBH Options Extension Header. These procedures are
applicable to implementations that maintain a strict separation
between forwarding and control plane implementations.
The procedures described herein satisfy the above mentioned
requirements by processing HBH Options on the forwarding plane to the
greatest degree possible. If a packet containing HBH Options must be
dispatched to the control plane, it is rate limited before
dispatching. In order to comply with the requirements of this
specification, implementations may execute the procedures described
herein or any other procedures that result in compliant behavior.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on September 17, 2016.
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Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 4
2. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Proposed Procedures . . . . . . . . . . . . . . . . . . . . . 6
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
5. Security Considerations . . . . . . . . . . . . . . . . . . . 7
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
7.1. Normative References . . . . . . . . . . . . . . . . . . 7
7.2. Informative References . . . . . . . . . . . . . . . . . 8
Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 9
Appendix B. HBH Options . . . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
In IPv6 [RFC2460], optional Internet-layer information is encoded in
extension headers that may be placed between the IPv6 header and the
upper-layer header. Currently, eleven extension headers are defined.
Among them is the Hop-by-Hop (HBH) Options Extension header. Unlike
any other extension header, the HBH Options Extension header is
examined by every node that a packet visits en route to its
destination.
The HBH Extension Header contains one or more HBH Options. Each HBH
Option contains a type identifier. Appendix B of this document
provides a list of currently defined HBH options.
Some HBH Options contain information that is useful to a router's
forwarding plane. In this document, we call these options "HBH
forwarding options". Among these is the Jumbo Payload Option
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[RFC2675]. The Jumbo Payload Option indicates the payload length of
the packet that carries it. While this information is required to
forward the packet, it can be discarded as soon as the packet has
been forwarded.
By contrast, other HBH Options contain information that is useful to
a router's control plane. In this document, we call these options
"HBH control options". Among these is the Router Alert Option
[RFC2711]. The Router Alert Option informs transit routers that the
packet carrying it contains information to be consumed by the
router's control plane. In many cases, this information is used to
forward subsequent packets.
Finally, the Pad and Pad1 options contain no information at all.
These are included to ensure word-alignment of subsequent options and
headers.
Many modern routers maintain a strict separation between forwarding
plane hardware and control plane hardware. In these routers,
forwarding plane bandwidth is plentiful, while control plane
bandwidth is constrained. In order to protect scarce control plane
resources, these routers enforce policies the restrict access from
the from the forwarding plane to the control plane. Effective
policies address packets containing the HBH Options Extension header,
because HBH control options require access from the forwarding plane
to the control plane.
Many network operators perceive HBH Options to be a breach of the
separation between the forwarding and control planes
[I-D.ietf-v6ops-ipv6-ehs-in-real-world]. Therefore, some network
operators discard all packets containing the HBH Options Extension
Header, while others forward the packets but ignore the HBH Options.
Still other operators severely rate-limit packets containing the HBH
Options Extension Header. In addition, some (notably older)
implementations send all packets containing a HBH header to the
control plane even if they contain only pad options, resulting in an
effect DoS on the router and inconsistent drops among those packets
due to rate limiting or other factors.
[RFC7045] legitimizes the current state of affairs, severely limiting
the utility of HBH options. In the words of RFC 7045:
"The IPv6 Hop-by-Hop Options header SHOULD be processed by
intermediate forwarding nodes as described in RFC2460. However,
it is to be expected that high-performance routers will either
ignore it or assign packets containing it to a slow processing
path. Designers planning to use a Hop-by-Hop option need to be
aware of this likely behaviour."
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This document clarifies requirements for IPv6 routers with respect to
the HBH Options Extension Header. These requirements are applicable
to all IPv6 routers, regardless of whether they maintain a strict
separation between forwarding and control plane hardware. In this
respect, this document updates RFC 2460 and RFC 7045.
This document also describes forwarding plane procedures for
processing the HBH Options Extension Header. These procedures are
applicable to implementations that maintain a strict separation
between forwarding and control plane hardware.
The procedures described herein satisfy the above mentioned
requirements by processing HBH Options on the forwarding plane to the
greatest degree possible. If a packet containing HBH Options must be
dispatched to the control plane, it is rate limited before
dispatching. In order to comply with the requirements of this
specification, implementations can execute the procedures described
herein or any other procedures that result in compliant behavior.
1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
2. Requirements
This section clarifies requirements for IPv6 routers with respect to
the HBH Options Extension Header. These requirements are applicable
to all IPv6 routers, regardless of whether they maintain a strict
separation between forwarding and control plane hardware.
o REQ1: Implementations MUST NOT discard otherwise forwardable
packets because they contain the HBH Options Extension header.
However, an implementation MAY be configured to discard packets
containing the HBH Options Extension Header, so long as this is
not the default behavior.
o REQ 2: Implementations MUST process unrecognized HBH Options as
described in Section 4.2 of RFC 2460. If an implementation
receives a packet that contains an unrecognized HBH Option, that
implementation MUST examine the first two bits of the HBH Option
Type indicator. Those bits determine whether the implementation
a) continues to process the packet, b) discards the packet without
sending an ICMP message or c) discards the packet and sends an
ICMP message.
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o REQ 3: Unrecognized HBH Options MUST be evaluated sequentially.
For example, assume that an implementation receives a packet that
carries two unrecognized HBH Options. The Type indicator of the
first unrecognized option begins with 01 while the Type indicator
of the second unrecognized option begins with 10. In this case,
the implementation MUST discard the packet without sending an ICMP
message to the source. However, if the Type indicator of the
first unrecognized option begins with 10 and the Type indicator of
the second unrecognized option begins with 01, the implementation
MUST discard the packet and send and ICMP Parameter Problem
message to the source.
o REQ 4: Implementations MUST protect themselves against denial of
service attacks that are propagated through HBH Options. These
protections MUST be enabled by default, without special
configuration.
o REQ 5: The originator of a packet MAY insert the HBH Options
Extension header between the IPv6 header and the upper-layer
header. It MAY also insert HBH Options inside of the HBH Options
header. Transit routers MUST NOT insert the HBH Options Extension
header between the IPv6 header and the upper-layer header.
Furthermore, they MUST NOT add or delete HBH Options inside of the
HBH Options Extension header.
o REQ 6: Implementations SHOULD support a configuration option that
limits the set of HBH Options that they recognize. For example,
assume that an implementation recognizes a particular HBH Option.
Using this configuration option, an operator can cause the
implementation to behave as if it does not recognize that option.
This MAY be configured a side effect of other functionality. For
example, an implementation might not recognize the Router Alert
Option unless a protocol that relies on the Router Alert Option
(e.g., RSVP) is configured.
o REQ 7: The HBH Options Extension Header can contain as many as
2056 bytes. Some implementation are not capable of processing
extension headers of that length
[I-D.gont-v6ops-ipv6-ehs-packet-drops]. When an implementation
receives a packet that it cannot process due to its HBH Options
Extension Header length, the implementation MUST discard the
packet and send an ICMP Parameter Problem message to the packet
source. ICMP Parameter Problem Code MUST be "Long Extension
Header" (value TBD) and the ICMP Parameter Problem Pointer MUST
contain the offset of HBH Options Extension Header.
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3. Proposed Procedures
This section describes forwarding plane procedures for processing the
HBH Options Extension Header. These procedures are applicable to
implementations that maintain a strict separation between forwarding
and control plane hardware.
The procedures described below process HBH Options on the forwarding
plane to the greatest degree possible. If a packet containing HBH
Options must be dispatched to the control plane, it is rate limited
before dispatching. In order to comply with the requirements of
Section 2, implementations can execute the procedures described
herein or any other procedures that result in compliant behavior.
Having received a packet containing the HBH Options Extension header,
the forwarding plane determines whether the HBH Options Extension
Header is too long for it to process. If so, the forwarding plane
discards the packet and sends an ICMP Parameter Problem message to
the packet source. ICMP Parameter Problem Code is set to "Long
Extension Header" and the ICMP Parameter Problem Pointer is set to
the offset of HBH Options Extension Header.
If the HBH Options Extension Header is not too long to process, the
forwarding plane hardware scans the header, assigning it to one of
the following classes:
o Discard
o Dispatch to control plane
o Forward, ignoring all HBH Option
o Forward, processing selected HBH Options
Forwarding plane hardware discards the packet if the HBH Options
Extension Header contains an unrecognized option whose Type indicator
begins with 01, 10 or 11. Forwarding plane hardware sends an ICMP
message if required. See Section 2 REQ 2 and REQ 3 for details.
If the packet is not discarded, and the HBH Options Extension header
contains at least one recognized control option, the forwarding plane
subjects the packet to a rate-limit and dispatches it to the control
plane
Otherwise, if the HBH Options Extension header contains only the
following option types, the packet is forwarded without further HBH
Option processing:
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o Pad or Pad1
o Unrecognized options whose Type indicator begins with 00
Otherwise, the forwarding plane process forwarding options and
forwards the packet
4. IANA Considerations
IANA is requested to assign a new entry to the ICMP Parameter Problem
Code registry. The name of this code is "Long Extension Header".
5. Security Considerations
This document contributes to the security of IPv6 routers, by
defining forwarding plane procedures for the processing of HBH
Options. These procedures are applicable to implementations that
maintain a strict separation between forwarding and control plane
hardware.
The procedures described below process HBH Options on the forwarding
plane to the greatest degree possible. If a packet containing HBH
Options must be dispatched to the control plane, it is rate limited
before dispatching.
6. Acknowledgements
This note grew out of a discussion among the author, Ole Troan, Mark
Townsley, Frank Brockners, and Shwetha Bhandari, and benefited from
comments by Dennis Ferguson, Brian Carpenter, Panos Kampanakis,
Jinmei Tatuya, and Joe Touch. Thanks to Fernando Gont for his
thoughtful review.
7. References
7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460,
December 1998, <http://www.rfc-editor.org/info/rfc2460>.
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[RFC7045] Carpenter, B. and S. Jiang, "Transmission and Processing
of IPv6 Extension Headers", RFC 7045,
DOI 10.17487/RFC7045, December 2013,
<http://www.rfc-editor.org/info/rfc7045>.
7.2. Informative References
[I-D.gont-v6ops-ipv6-ehs-packet-drops]
Gont, F., Hilliard, N., Doering, G., LIU, S., and W.
Kumari, "Operational Implications of IPv6 Packets with
Extension Headers", draft-gont-v6ops-ipv6-ehs-packet-
drops-03 (work in progress), March 2016.
[I-D.ietf-6man-rfc2460bis]
Deering, S. and B. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", draft-ietf-6man-rfc2460bis-03 (work
in progress), January 2016.
[I-D.ietf-roll-trickle-mcast]
Hui, J. and R. Kelsey, "Multicast Protocol for Low power
and Lossy Networks (MPL)", draft-ietf-roll-trickle-
mcast-12 (work in progress), June 2015.
[I-D.ietf-v6ops-ipv6-ehs-in-real-world]
Gont, F., Linkova, J., Chown, T., and S. LIU,
"Observations on the Dropping of Packets with IPv6
Extension Headers in the Real World", draft-ietf-v6ops-
ipv6-ehs-in-real-world-02 (work in progress), December
2015.
[RFC2675] Borman, D., Deering, S., and R. Hinden, "IPv6 Jumbograms",
RFC 2675, DOI 10.17487/RFC2675, August 1999,
<http://www.rfc-editor.org/info/rfc2675>.
[RFC2711] Partridge, C. and A. Jackson, "IPv6 Router Alert Option",
RFC 2711, DOI 10.17487/RFC2711, October 1999,
<http://www.rfc-editor.org/info/rfc2711>.
[RFC4302] Kent, S., "IP Authentication Header", RFC 4302,
DOI 10.17487/RFC4302, December 2005,
<http://www.rfc-editor.org/info/rfc4302>.
[RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)",
RFC 4303, DOI 10.17487/RFC4303, December 2005,
<http://www.rfc-editor.org/info/rfc4303>.
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[RFC4782] Floyd, S., Allman, M., Jain, A., and P. Sarolahti, "Quick-
Start for TCP and IP", RFC 4782, DOI 10.17487/RFC4782,
January 2007, <http://www.rfc-editor.org/info/rfc4782>.
[RFC5570] StJohns, M., Atkinson, R., and G. Thomas, "Common
Architecture Label IPv6 Security Option (CALIPSO)",
RFC 5570, DOI 10.17487/RFC5570, July 2009,
<http://www.rfc-editor.org/info/rfc5570>.
[RFC6398] Le Faucheur, F., Ed., "IP Router Alert Considerations and
Usage", BCP 168, RFC 6398, DOI 10.17487/RFC6398, October
2011, <http://www.rfc-editor.org/info/rfc6398>.
[RFC6553] Hui, J. and JP. Vasseur, "The Routing Protocol for Low-
Power and Lossy Networks (RPL) Option for Carrying RPL
Information in Data-Plane Datagrams", RFC 6553,
DOI 10.17487/RFC6553, March 2012,
<http://www.rfc-editor.org/info/rfc6553>.
[RFC6621] Macker, J., Ed., "Simplified Multicast Forwarding",
RFC 6621, DOI 10.17487/RFC6621, May 2012,
<http://www.rfc-editor.org/info/rfc6621>.
[RFC6971] Herberg, U., Ed., Cardenas, A., Iwao, T., Dow, M., and S.
Cespedes, "Depth-First Forwarding (DFF) in Unreliable
Networks", RFC 6971, DOI 10.17487/RFC6971, June 2013,
<http://www.rfc-editor.org/info/rfc6971>.
Appendix A. Change Log
RFC Editor: this section need not be published in any RFC.
Initial Version: October 2015: text copied from draft-baker-6man-
hbh-header-handling-03.txt and discussed in IETF 94
IETF 94 Update: Sections 2.2, 2..3, and 2.4 moved to an appendix
reflecting (negative) working group viewpoint on the modification
of packet length in flight.
The content of this document is likely to be subsumed into 2460bis
[I-D.ietf-6man-rfc2460bis], but is held separate for the present
discussion.
A new section 2.2 added detailing conceptual processing model for
HBH options.
version 2 Addressed editorial comments
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Appendix B. HBH Options
At this writing, there are several defined Hop-by-Hop options:
PAD Options: The PAD1 and PADn [RFC2460]
Router Alert Option: The IPv6 Router Alert Option [RFC2711]
[RFC6398]
Jumbo Payload: [RFC2675]
RPL Option: [RFC6553]
Quickstart Option [RFC4782]
Common Architecture Label IPv6 Security Option: [RFC5570]
SMF Option: [RFC6621]
MPL Option: [I-D.ietf-roll-trickle-mcast]
DFF Option: [RFC6971]
Authors' Addresses
Fred Baker
Cisco Systems
Santa Barbara, California 93117
USA
Email: fred@cisco.com
Ron Bonica
Juniper Networks
Herndon, Virginia 20171
USA
Email: rbonica@juniper.net
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