The IPv6 Unrecognized Option
draft-bonica-6man-unrecognized-opt-01
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draft-bonica-6man-unrecognized-opt-01
6man R. Bonica
Internet-Draft Juniper Networks
Intended status: Standards Track J. Leddy
Expires: December 10, 2018 Comcast
June 8, 2018
The IPv6 Unrecognized Option
draft-bonica-6man-unrecognized-opt-01
Abstract
This document describes a method by which a source node can determine
whether the underlying network can a) convey a packet that contains
IPv6 destination options from itself to a destination node, and b)
convey an ICMPv6 Parameter Problem message in the reverse direction.
In order to support this method, this document defines a new IPv6
option, called the Unrecognized option. The Unrecognized option is
not recognized by any destination node and always elicits an ICMPv6
Parameter Problem message.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on December 10, 2018.
Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
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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
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3
3. The Unrecognized Option . . . . . . . . . . . . . . . . . . . 4
4. Application . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Non-Implementation . . . . . . . . . . . . . . . . . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . 5
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
9.1. Normative References . . . . . . . . . . . . . . . . . . 6
9.2. Informative References . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
In IPv6 [RFC8200], optional internet-layer information is encoded in
extension headers that are placed between the IPv6 header and the
upper-layer header. Two of the extension headers specified in
[RFC8200], the Hop-by-Hop Options header and the Destination Options
header, carry a variable number of "options". Each option contains
the following fields:
o Option Type - 8-bit identifier of the type of option.
o Opt Data Len - 8-bit unsigned integer. Length of the Option Data
field of this option, in octets.
o Option Data - Variable-length field. Option-Type-specific data.
The Option Type identifiers are encoded so that their highest-order 2
bits specify the action that must be taken if the processing IPv6
node does not recognize the option. Actions follow:
o 00 - Skip over this option and continue processing the header.
o 01 - Discard the packet.
o 10 - Discard the packet and, regardless of whether or not the
packet's Destination Address was a multicast address, send an
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ICMPv6 [RFC4443] Parameter Problem, Code 2, message to the
packet's Source Address, pointing to the unrecognized Option Type.
o 11 - Discard the packet and, only if the packet's Destination
Address was not a multicast address, send an ICMPv6 Parameter
Problem, Code 2, message to the packet's Source Address, pointing
to the unrecognized Option Type.
Several upper-layer protocols [RFC6275] [I-D.leddy-6man-truncate]
emit packets that contain IPv6 destination options. These protocols
rely the underlying network to forward packets that contain IPv6
destination options.
A subset of those protocols emit IPv6 destination options with high-
order bits equal to "10" and "11". These IPv6 destination options
elicit ICMP Parameter Problem messages from destination nodes that do
not recognize them. The above-mentioned protocols perform better
when the network can convey ICMPv6 Parameter Problem messages from
the destination node to the source node.
Operational experience [RFC7872] reveals that a significant number of
networks drop packets that contain IPv6 destination options.
Likewise, many networks drop ICMP Parameter Problem messages.
This document describes a method by which a source node can determine
whether the underlying network can:
o Convey a packet that contains IPv6 destination options from itself
to a destination node.
o Convey an ICMPv6 Parameter Problem message in the reverse
direction.
In order to support this method, this document defines a new IPv6
option, called the Unrecognized option. The Unrecognized option is
not recognized by any destination node and always elicits an ICMPv6
Parameter Problem message.
2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
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3. The Unrecognized Option
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Type | Opt Data Len | Option Data
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
Figure 1
Figure 1 depicts the Unrecognized Option.
Option fields are as follows:
o Option Type - Unrecognized Option. Value TBD by IANA. See Notes
below.
o Opt Data Len - Length of Option Data, measured in bytes.
o Option Data - MUST be set to zero on transmission. MUST be
ignored on receipt.
The Unrecognized option MUST NOT be implemented on any node. It must
be unrecognized on all nodes so that it elicits an ICMP Parameter
Problem message.
NOTE 1: The highest-order two bits of the Option Type (i.e., the
"act" bits) are 10. These bits specify the action taken by a
destination node that does not recognize Unrecognized option. The
required action is to discard the packet and, regardless of whether
or not the packet's Destination Address was a multicast address, send
an ICMPv6 Parameter Problem, Code 2, message to the packet's Source
Address, pointing to the unrecognized Option Type.
NOTE 2: The third highest-order bit of the Option Type (i.e., the
"chg" bit) is 0. This indicates that Option Data cannot be modified
along the path between the packet's source and its destination.
4. Application
Upper-layer protocols execute the following procedure:
o Set a short timer (e.g., two or three seconds).
o Send a probe packet.
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o Wait for either a) timer expiration or b) an ICMPv6 Parameter
Problem message that matches the probe packet.
The probe packet contains an IPv6 Destination Options header and the
IPv6 Destination Options header contains an Unrecognized option. The
Unrecognized Option MAY contain option data of any length. In order
to influence how the packet is routed to its destination, the probe
packet MAY contain upper-layer headers. However, because the packet
contains the Unrecognized option, it is always discarded and is never
delivered to an upper-layer protocol.
An ICMPv6 Parameter Problem message matches a probe packet if the
initial bytes of the probe packet appear in the ICMP Parameter
Problem message.
If the timer expires, one or both of the following is true:
o The underlying network cannot convey a packet that contains IPv6
destination options from itself to a destination node.
o The underlying network cannot convey an ICMPv6 Parameter Problem
message in the reverse direction
If a matching ICMPv6 Parameter Problem arrives, both of the following
are true:
o The underlying network can convey a packet that contains IPv6
destination options from itself to a destination node.
o The underlying network can convey an ICMPv6 Parameter Problem
message in the reverse direction
5. Non-Implementation
A stated above, the Unrecognized option MUST NOT be implemented on
any node. It must be unrecognized on all nodes so that it elicits an
ICMP Parameter Problem message.
The sole purpose of this document is to reserve a IPv6 Option Type,
so that the procedures described in Section 4, can be executed
without using an unassigned Option Type.
6. Security Considerations
Because this document introduces no new functionality, it introduces
no new security vulnerabilities.
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7. IANA Considerations
IANA is requested to allocate a codepoint from the Destination
Options and Hop-by-hop Options registry
(https://www.iana.org/assignments/ipv6-parameters/
ipv6-parameters.xhtml#ipv6-parameters-2). This option is called
"Unrecognized". The "act" bits are 10 and the "chg" bit is 0.
8. Acknowledgements
Thanks to Ross Callon for his careful review of this document.
9. References
9.1. 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,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC4443] Conta, A., Deering, S., and M. Gupta, Ed., "Internet
Control Message Protocol (ICMPv6) for the Internet
Protocol Version 6 (IPv6) Specification", STD 89,
RFC 4443, DOI 10.17487/RFC4443, March 2006,
<https://www.rfc-editor.org/info/rfc4443>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", STD 86, RFC 8200,
DOI 10.17487/RFC8200, July 2017,
<https://www.rfc-editor.org/info/rfc8200>.
9.2. Informative References
[I-D.leddy-6man-truncate]
Leddy, J. and R. Bonica, "Destination Originates Internet
Control Message Protocol (ICMP) Packet Too Big (PTB)
Messages", draft-leddy-6man-truncate-01 (work in
progress), May 2018.
[RFC6275] Perkins, C., Ed., Johnson, D., and J. Arkko, "Mobility
Support in IPv6", RFC 6275, DOI 10.17487/RFC6275, July
2011, <https://www.rfc-editor.org/info/rfc6275>.
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[RFC7872] Gont, F., Linkova, J., Chown, T., and W. Liu,
"Observations on the Dropping of Packets with IPv6
Extension Headers in the Real World", RFC 7872,
DOI 10.17487/RFC7872, June 2016,
<https://www.rfc-editor.org/info/rfc7872>.
Authors' Addresses
Ron Bonica
Juniper Networks
2251 Corporate Park Drive
Herndon, Virginia 20171
USA
Email: rbonica@juniper.net
John Leddy
Comcast
1717 John F Kennedy Blvd.
Philadelphia, PA 19103
USA
Email: john_leddy@comcast.com
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