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Versions: (draft-pignataro-intarea-gre-ipv6) 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 RFC 7676

Intarea Working Group                                       C. Pignataro
Internet-Draft                                             Cisco Systems
Updates: 2784 (if approved)                                    R. Bonica
Intended status: Standards Track                        Juniper Networks
Expires: September 28, 2015                                  S. Krishnan
                                                                Ericsson
                                                          March 27, 2015


          IPv6 Support for Generic Routing Encapsulation (GRE)
                     draft-ietf-intarea-gre-ipv6-04

Abstract

   Generic Routing Encapsulation (GRE) can be used to carry any network-
   layer payload protocol over any network-layer delivery protocol.  GRE
   procedures are specified for IPv4, used as either the payload or
   delivery protocol.  However, GRE procedures are not specified for
   IPv6.

   This document specifies GRE procedures for IPv6, used as either the
   payload or delivery protocol.  It updates the GRE specification, RFC
   2784.

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].

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 28, 2015.





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Copyright Notice

   Copyright (c) 2015 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.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  GRE Header Fields . . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Checksum Present  . . . . . . . . . . . . . . . . . . . .   3
     2.2.  Protocol Type . . . . . . . . . . . . . . . . . . . . . .   3
   3.  IPv6 as a GRE Payload . . . . . . . . . . . . . . . . . . . .   4
     3.1.  MTU Considerations  . . . . . . . . . . . . . . . . . . .   4
   4.  IPv6 as a GRE Delivery Protocol . . . . . . . . . . . . . . .   5
     4.1.  Checksum Considerations . . . . . . . . . . . . . . . . .   5
     4.2.  MTU Considerations  . . . . . . . . . . . . . . . . . . .   5
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   6
   8.  Normative References  . . . . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   Generic Routing Encapsulation (GRE) [RFC2784] [RFC2890] can be used
   to carry any network-layer payload protocol over any network-layer
   delivery protocol.  GRE procedures are specified for IPv4 [RFC0791],
   used as either the payload or delivery protocol.  However, GRE
   procedures are not specified for IPv6 [RFC2460].

   This document specifies GRE procedures for IPv6, used as either the
   payload or delivery protocol.  It updates RFC 2784 [RFC2784].  Like
   RFC 2784, this specification describes GRE how has been implemented
   by several vendors.






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1.1.  Terminology

   The following terms are specific to GRE and are taken from [RFC2784]:

   o  GRE delivery header - an IPv4 or IPv6 header whose source address
      represents the GRE ingress node and whose destination address
      represents the GRE egress node.  The GRE delivery header
      encapsulates a GRE header.

   o  GRE header - the GRE protocol header.  The GRE header is
      encapsulated in the GRE delivery header and encapsulates GRE
      payload.

   o  GRE payload - a network layer packet that is encapsulated by the
      GRE header.

   The following terms are specific MTU discovery:

   o  path MTU (PMTU) - the minimum MTU of all the links in a path
      between a source node and a destination node.  If the source and
      destination node are connected through equal cost multipath
      (ECMP), the PMTU is equal to the minimum link MTU of all links
      contributing to the multipath.

   o  Path MTU Discovery (PMTUD) - A procedure for dynamically
      discovering the PMTU between two nodes on the Internet.  PMTUD
      procedures for IPv6 are defined in [RFC1981].

2.  GRE Header Fields

   This document does not change the GRE header format or any behaviors
   specified by [RFC2784] or [RFC2890].

2.1.  Checksum Present

   When the delivery protocol is IPv6, the GRE ingress router SHOULD set
   the Checksum Present field to zero.  GRE egress routers MUST accept
   either a value of zero or one in this field.  If the GRE egress
   router receives a value of one, it MUST use that information to
   calculate the GRE header length.  It MUST also use the checksum to
   verify packet integrity.

2.2.  Protocol Type

   The Protocol Type field contains the protocol type of the payload
   packet.  Protocol Types are defined in [ETYPES].  An implementation
   receiving a packet containing a Protocol Type which is not listed in
   [ETYPES] SHOULD discard the packet.



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3.  IPv6 as a GRE Payload

   When the GRE payload is IPv6, the Protocol Type field in the GRE
   header MUST be set to 0x86DD.

3.1.  MTU Considerations

   The GRE ingress router maintains an estimate of the GRE MTU (GMTU).
   The GMTU is equal to the PMTU associated with the path between the
   GRE ingress and the GRE egress, minus the GRE overhead.  The GRE
   overhead is the combined length of the GRE and IP delivery headers.

   The GRE ingress router obtains a PMTU estimate using any of the
   following:

   o  System defaults

   o  Configuration

   o  PMTUD

   When the GRE ingress receives an IPv6 payload packet whose length is
   less than or equal to the GMTU, it can encapsulate and forward the
   packet without fragmentation of any kind.  In this case, the GRE
   ingress router MUST NOT fragment the payload or delivery packets.

   When the GRE ingress receives an IPv6 payload packet whose length is
   greater than the GMTU, and the GMTU is greater than or equal to 1280
   octets, the GRE ingress router MUST:

   o  discard the IPv6 payload packet

   o  send an ICMPv6 Packet Too Big (PTB) [RFC4443] message to the IPv6
      payload packet source.  The MTU field in the ICMPv6 PTB message is
      set to the GMTU.

   The GRE ingress router MUST support a configuration option that
   determines how the GRE ingress behaves when it receives an IPv6
   payload packet whose length is greater than the GMTU, and the GMTU is
   less than 1280 octets.  In its default configuration, the GRE ingress
   router MUST:

   o  encapsulate the entire IPv6 packet in a single GRE header and IP
      delivery header

   o  fragment the delivery header, so that it can be reassembled by the
      GRE egress




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   However, in an alternative configuration, the GRE ingress MAY:

   o  discard the IPv6 packet

   o  send an ICMPv6 Packet Too Big (PTB) [RFC4443] message to the IPv6
      packet source.  The MTU field in the ICMPv6 PTB message is set to
      the GMTU.

4.  IPv6 as a GRE Delivery Protocol

   When the GRE delivery protocol is IPv6, the GRE header can
   immediately follow the GRE delivery header.  Alternatively, IPv6
   extension headers MAY be inserted between the GRE delivery header and
   the GRE header.

   If the GRE header immediately follows the GRE delivery header, the
   Next Header field in the IPv6 header of the GRE delivery packet MUST
   be set to 47.  If extension headers are inserted between the GRE
   delivery header and the GRE header, the Next Header field in the last
   IPv6 extension header MUST be set to 47.

4.1.  Checksum Considerations

   As stated in [RFC2784], the Checksum field contains the IP (one's
   complement) checksum sum of the all the 16 bit words in the GRE
   header and the payload packet.  Therefore, the checksum does not
   ensure the integrity of the IPv6 delivery header.

   Because the IPv6 delivery header does not include a checksum of its
   own, it is subject to corruption.  However, even if the delivery
   header is corrupted, to likelihood of that corruption resulting in
   misdelivery of the payload is extremely low.

4.2.  MTU Considerations

   "IPv6 requires that every link in the Internet have an MTU of 1280
   octets or greater.  On any link that cannot convey a 1280-octet
   packet in one piece, link-specific fragmentation and reassembly must
   be provided at a layer below IPv6" [RFC2460].

   IP adjacencies formed by GRE over IPv6 share this requirement.  The
   IP adjacency MUST have an MTU of 1280 octets or greater.  This
   requirement is fulfilled if all permissible paths between the GRE
   ingress and GRE egress have PMTU greater than the 1280 plus the GRE
   overhead.

   In case all permissible routes between the GRE ingress and GRE egress
   do not have PMTU greater than 1280 plus the GRE overhead,



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   implementations MUST be capable of fragmenting and reassembling the
   GRE delivery header, as described in Section 3.1.

5.  IANA Considerations

   This document makes no request of IANA.

6.  Security Considerations

   This document adds no additional security risks to GRE, beyond what
   is specified in [RFC2784].  It also does not provide any additional
   security for GRE.

7.  Acknowledgements

   The authors would like to thank Fred Baker, Dino Farinacci, Tom
   Herbert, Fred Templin, Joe Touch, Andrew Yourtchenko and Lucy Yong
   for their thorough review and useful comments.

8.  Normative References

   [ETYPES]   IANA, "ETHER TYPES", 2014,
              <http://www.iana.org/assignments/ieee-802-numbers/
              ieee-802-numbers.xhtml#ieee-802-numbers-1>.

   [RFC0791]  Postel, J., "Internet Protocol", STD 5, RFC 791, September
              1981.

   [RFC1981]  McCann, J., Deering, S., and J. Mogul, "Path MTU Discovery
              for IP version 6", RFC 1981, August 1996.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2460]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", RFC 2460, December 1998.

   [RFC2784]  Farinacci, D., Li, T., Hanks, S., Meyer, D., and P.
              Traina, "Generic Routing Encapsulation (GRE)", RFC 2784,
              March 2000.

   [RFC2890]  Dommety, G., "Key and Sequence Number Extensions to GRE",
              RFC 2890, September 2000.

   [RFC4443]  Conta, A., Deering, S., and M. Gupta, "Internet Control
              Message Protocol (ICMPv6) for the Internet Protocol
              Version 6 (IPv6) Specification", RFC 4443, March 2006.




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Authors' Addresses

   Carlos Pignataro
   Cisco Systems
   7200-12 Kit Creek Road
   Research Triangle Park, North Carolina  27709
   USA

   Email: cpignata@cisco.com


   Ron Bonica
   Juniper Networks
   2251 Corporate Park Drive
   Herndon, Virginia
   USA

   Email: rbonica@juniper.net


   Suresh Krishnan
   Ericsson
   8400 Decarie Blvd.
   Town of Mount Royal, QC
   Canada

   Phone: +1 514 345 7900 x42871
   Email: suresh.krishnan@ericsson.com























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