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6man                                                           R. Bonica
Internet-Draft                                          Juniper Networks
Intended status: Standards Track                                J. Leddy
Expires: February 11, 2019                                       Comcast
                                                         August 10, 2018


                         The IPv6 Probe Option
                 draft-bonica-6man-unrecognized-opt-03

Abstract

   This document defines a new IPv6 option, called the Probe option.
   The Probe option elicits an ICMPv6 Parameter Problem message from all
   nodes that process it.  When a node sends a packet that contains the
   Probe option and receives an ICMPv6 Parameter Problem message in
   response, it has verified the network's ability to convey packets
   that contain the Probe option.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
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   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
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   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 February 11, 2019.

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
   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



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   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 Probe Option  . . . . . . . . . . . . . . . . . . . . . .   4
   4.  Discovering Network Capabilities  . . . . . . . . . . . . . .   5
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   6
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   6
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   In IPv6 [RFC8200], optional internet-layer information is encoded in
   extension headers.  Two extension headers, the Hop-by-Hop Options
   header and the Destination Options header, contain a variable number
   of options.  Each option contains the following fields:

   o  Option Type

   o  Opt Data Length

   o  Option Data

   The Option Type identifiers are encoded so that their highest-order 2
   bits specify the action to be taken if the processing node does not
   recognize the option.  Encodings follow:

   o  00 - Skip over the option and continue processing the header.

   o  01 - Discard the packet.

   o  10 - Discard the packet and send an 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.





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   Several upper-layer protocols [RFC6275] [I-D.leddy-6man-truncate]
   emit packets that contain IPv6 destination options.  These protocols
   rely the network to convey packets that contain the IPv6 Destination
   Options header.

   A subset of those protocols emit IPv6 destination options with high-
   order bits equal to "10" and "11".  These IPv6 destination options
   elicit ICMPv6 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 all packets that contain the IPv6 Destination Options
   header.  Similarly, a significant number of networks allow packets
   that contain the IPv6 Destination Options header, but only if
   Destination Options header does not exceed a specific size.  Finally,
   many networks drop all ICMP Parameter Problem messages.

   This document describes procedures by which a source node can
   discover relevant capabilities of the network that connects it to a
   destination node.  Using these procedures, the source node can
   determine:

   o  Whether the network can convey a packet containing a Destination
      Options header of a specific size from the source node to a
      destination node.

   o  Whether the network can convey an ICMPv6 Parameter Problem message
      from the destination node to the source node.

   In order to support the above-mentioned procedures, this document
   defines a new IPv6 option, called the Probe option.  The Probe option
   elicits an ICMPv6 Parameter Problem message from all nodes that
   process it.  It elicits an IPv6 Parameter Problem message, regardless
   of whether the processing node recognizes the option.  When a source
   node sends a packet that contains the Probe option and receives an
   ICMPv6 Parameter Problem message in response, it has verified the
   above-mentioned network capabilities.

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 Probe 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 Probe Option.

   Option fields are as follows:

   o  Option Type - Probe 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 Opt Data Len and Option Data fields can be used to expand the
   Probe Option and the Destination Options header that contains it to a
   required length.  See Section 4 for details.

   A packet MAY contain multiple instances of the Probe option.  In
   IPv6, the maximum size of a Destination Options header is 2048 bytes,
   while the maximum size of an option instance is only 256 bytes.
   Therefore, multiple instances of the Probe option are required to
   expand the Destination Options header beyond 256 bytes.

   All nodes process the Probe option as follows, regardless of whether
   they recognize the option:

   o  Discard the packet.

   o  Send an ICMPv6 Parameter Problem, Code 2, message to the packet's
      Source Address, pointing to the unrecognized Option Type.

   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 Probe option.  The required
   action is to discard the packet and send an ICMPv6 Parameter Problem,
   Code 2, message to the packet's Source Address, pointing to the Probe
   Option Type.




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   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.  Discovering Network Capabilities

   Assume that a source node needs to determine whether the network can
   convey a packet from itself to a destination node.  The packet
   contains a Destination Options header whose length is N bytes.  As
   per [RFC8200], the Destination Options header length must be a
   multiple of 8.  Therefore, N must be a multiple of 8.

   The source node executes the following procedure:

   o  Set a short timer (e.g., one or two seconds).

   o  Send a probe packet.

   o  Wait for either a) an ICMPv6 Parameter Problem message that
      matches the probe packet, or b) timer expiration

   The probe packet contains an IPv6 Destination Options header and the
   IPv6 Destination Options header contains one or more instances of
   Probe option.  The number of Probe option instances and the length of
   Option Data in each instance are chosen so that the Destination
   Options header length will be equal to N.

   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 Probe 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 source node receives an ICMP Parameter Problem message that
   matches the probe, both of the following statements are true:

   o  The network can convey a packet containing a Destination Options
      header of a specific size from the source node to a destination
      node.

   o  The network can convey an ICMPv6 Parameter Problem message from
      the destination node to the source node.

   If the timer expires, at least one of the following statements is
   true:



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   o  The network cannot convey a packet containing a Destination
      Options header of a specific size from the source node to a
      destination node.

   o  The network cannot convey an ICMPv6 Parameter Problem message from
      the destination node to the source node.

   o  Either the probe or the ICMPv6 Parameter Problem message was lost
      due to a transient issue (e.g., congestion).

   As noted above, transient issues can cause false negative results.
   Therefore, this procedure MAY be repeated after initial failure.

5.  Security Considerations

   This document introduces no new security vulnerabilities.  Any
   security vulnerabilities exposed by the Probe option are currently
   exposed by all undefined or unrecognized option types.  This is
   because the Probe option elicits the same behavior as an undefined or
   unrecognized option

6.  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
   "Probe".  The "act" bits are 10 and the "chg" bit is 0.

7.  Acknowledgements

   Thanks to Ross Callon, Fernando Gont and Jinmei Tatuya for their
   careful review of this document.

8.  References

8.1.  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>.



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   [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>.

8.2.  Informative References

   [I-D.leddy-6man-truncate]
              Leddy, J. and R. Bonica, "IPv6 Packet Truncation", draft-
              leddy-6man-truncate-04 (work in progress), June 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>.

   [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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