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Versions: 00 01 02 draft-ietf-tsvwg-gre-in-udp-encap

Network Working Group                                     E. Crabbe, Ed.
Internet-Draft                                                    Google
Intended status: Standards Track                            L. Yong, Ed.
Expires: April 24, 2014                                       Huawei USA
                                                              X. Xu, Ed.
                                                     Huawei Technologies
                                                        October 21, 2013


               Generic UDP Encapsulation for IP Tunneling
                  draft-yong-tsvwg-gre-in-udp-encap-02

Abstract

   This document describes a method of encapsulating arbitrary protocols
   within GRE and UDP headers.  In this encapsulation, the source UDP
   port may be used as an entropy field for purposes of loadbalancing
   while the payload protocol may be identified by the GRE Protocol
   Type.

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 April 24, 2014.









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Copyright Notice

   Copyright (c) 2013 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
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Procedures  . . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Encapsulation Considerations  . . . . . . . . . . . . . . . .   6
   5.  Backward Compatibility  . . . . . . . . . . . . . . . . . . .   7
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
     7.1.  Vulnerability . . . . . . . . . . . . . . . . . . . . . .   7
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   8
   9.  Contributing Authors  . . . . . . . . . . . . . . . . . . . .   8
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .   9
     10.1.  Normative References . . . . . . . . . . . . . . . . . .   9
     10.2.  Informative References . . . . . . . . . . . . . . . . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  10

1.  Introduction

   Load balancing, or more specifically, statistical multiplexing of
   traffic using Equal Cost Multi-Path (ECMP) and/or Link Aggregation
   Groups (LAGs) in IP networks is a widely used technique for creating
   higher capacity networks out of lower capacity links.  Most existing
   routers in IP networks are already capable of distributing IP traffic
   flows over ECMP paths and/or LAGs on the basis of a hash function
   performed on flow invariant fields in IP packet headers and their
   payload protocol headers.  Specifically, when the IP payload is a
   User Datagram Protocol (UDP)[RFC0768] or Transmission Control
   Protocol (TCP) packet, router hash functions frequently operate on
   the five-tuple of the source IP address, the destination IP address,
   the source port, the destination port, and the protocol/next-header





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   Several tunneling techniques are in common use in IP networks, such
   as Generic Routing Encapsulation (GRE) [RFC2784], MPLS [RFC4023] and
   L2TPv3 [RFC3931].  GRE is an increasingly popular encapsulation
   choice, especially in environments where MPLS is unavailable or
   unnecessary.  Unfortunately, use of common GRE endpoints may reduce
   the entropy available for use in load balancing, especially in
   environments where the GRE Key field [RFC2890] is not readilly
   available for use as entropy in forwarding decisions.

   This document defines a generic GRE-in-UDP encapsulation for
   tunneling arbitrary network protocol payloads across an IP network
   environment where ECMP or LAGs are used.  The GRE header provides
   payload protocol de-multiplexing by way of it's protocol type field
   [RFC2784] while the UDP header provides additional entropy by way of
   it's source port.

   This encapsulation method requires no changes to the transit IP
   network.  Hash functions in most existing IP routers may utilize and
   benefit from the use of a GRE-in-UDP tunnel without needing any
   change or upgrade to to their ECMP implementations.  The
   encapsulation mechanism is applicable to a variety of IP networks
   including Data Center and wide area networks.

2.  Terminology

   The terms defined in [RFC0768] are used in this document.

3.  Procedures

   When a tunnel ingress device conforming to this document receives a
   packet, the ingress MUST encapsulate the packet in UDP and GRE
   headers and set the destination port of the UDP header to [TBD]
   Section 6.  he ingress device must also insert the payload protocol
   type in the GRE Protocol Type field.  The ingress device SHOULD set
   the UDP source port based on flow invariant fields from the payload
   header, otherwise it should be set to a randomly selected constant
   value, e.g. zero, to avoid packet flow reordering.  How a tunnel
   ingress generates entropy from the payload is outside the scope of
   this document.  The tunnel ingress MUST encode its own IP address as
   the source IP address and the egress tunnel endpoint IP address.  The
   TTL field in the IP header must be set to a value appropriate for
   delivery of the encapsulated packet to the tunnel egress endpoint.

   When the tunnel egress receives a packet, it must remove the outer
   UDP and GRE headers.  Section 5 describes the error handling when
   this entity is not instantiated at the tunnel egress.





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   To simplify packet processing at the tunnel egress, packets destined
   to this assigned UDP destination port [TBD] SHOULD have their UDP
   checksum and Sequence flags set to zero because the egress tunnel
   only needs to identify this protocol.  Although IPv6 [RFC2460]
   restricts the processing a packet with the UDP checksum of zero,
   [RFC6935] and [RFC6936] relax this constraint to allow the zero UDP
   checksum.

   The tunnel ingress may set the GRE Key Present, Sequence Number
   Present, and Checksum Present bits and asscociated fields in the GRE
   header defined by [RFC2784] and [RFC2890].

   In addition IPv6 nodes MUST conform to the following:

   1.  the IPv6 tunnel ingress and egress SHOULD follow the node
       requirements specified in Section 4 of [RFC6936] and the usage
       requirements specified in Section 5 of [RFC6936]

   2.  IPv6 transit nodes SHOULD follow the requirements 9, 10, 11
       specified in Section 5 of [RFC6936].

   The format of the GRE-in-UDP encapsulation for both IPv4 and IPv6
   outer headersis shown in the followingfigures:

   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

   IPv4 Header:
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |Version|  IHL  |Type of Service|          Total Length         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Identification        |Flags|      Fragment Offset    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Time to Live |Protcol=17[UDP]|          Header Checksum      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Source IPv4 Address                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Destination IPv4 Address                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   UDP Header:
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Source Port = XXXX      |       Dest Port = TBD         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           UDP Length          |        UDP Checksum           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   GRE Header:



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   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |C| |K|S| Reserved0       | Ver |         Protocol Type         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Checksum (optional)      |       Reserved1 (Optional)    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                         Key (optional)                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 Sequence Number (Optional)                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



                      Figure 1: UDP+GRE IPv4 headers

   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

   IPv6 Header:
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |Version| Traffic Class |           Flow Label                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Payload Length        | NxtHdr=17[UDP]|   Hop Limit   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   +                                                               +
   |                                                               |
   +                     Outer Source IPv6 Address                 +
   |                                                               |
   +                                                               +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   +                                                               +
   |                                                               |
   +                  Outer Destination IPv6 Address               +
   |                                                               |
   +                                                               +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   UDP Header:
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Source Port = XXXX      |       Dest Port = TBD         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           UDP Length          |        UDP Checksum           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+




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   GRE Header:
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |C| |K|S| Reserved0       | Ver |         Protocol Type         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Checksum (optional)      |       Reserved1 (Optional)    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                         Key (optional)                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 Sequence Number (Optional)                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



                      Figure 2: UDP+GRE IPv6 headers

   The total overhead increase for a UDP+GRE tunnel without use of
   optional GRE fields, representing the lowest total overhead increase,
   is 32 bytes in the case of IPv4 and 52 bytes in the case of IPv6.
   The total overhead increase for a UDP+GRE tunnel with use of GRE Key,
   Sequence and Checksum Fields, representing the highest total overhead
   increase, is 44 bytes in the case of IPv4 and 64 bytes in the case of
   IPv6.

4.  Encapsulation Considerations

   GRE-in-UDP encapsulation allows the tunneled traffic to be unicast,
   broadcast, or multicast traffic.  Entropy may be generated from the
   header of tunneled unicast or broadcast/multicast packets at tunnel
   ingress.  The mapping mechanism between the tunneled multicast
   traffic and the multicast capability in the IP network is transparent
   and independent to the encapsulation and is outside the scope of this
   document.

   If tunnel ingress must perform fragmentation on a packet before
   encapsulation, it MUST use the same source UDP port for all packet
   fragments.  This ensures that the transit routers will forward the
   packet fragments on the same path.  GRE-in-UDP encapsulation
   introduces some overhead as mentioned in section 3, which reduces the
   effective Maximum Transmission Unit (MTU) size.  An operator should
   factor in this addition overhead bytes when considering an MTU size
   for the payload to reduce the likelihood of fragmentation.

   To ensure the tunneled traffic gets the same treatment over the IP
   network, prior to the encapsulation process, tunnel ingress should
   process the payload to get the proper parameters to fill into the IP
   header such as DiffServ [[RFC2983]].  Tunnel end points that support
   ECN MUST use the method described in [RFC6040] for ECN marking
   propagation.  This process is outside of the scope of this document.



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   Note that the IPv6 header [RFC2460] contains a flow label field that
   may be used for load balancing in an IPv6 network [RFC6438].  Thus in
   an IPv6 network, either GRE-in-UDP or flow labels may be used in
   order to improve load balancing performance.  Use of GRE-in-UDP
   encapsulation provides a unified hardware implementation for load
   balancing in an IP network independent of the IP version(s) in use.

5.  Backward Compatibility

   It is assumed that tunnel ingress routers must be upgraded in order
   to support the encapsulations described in this document.

   No change is required at transit routers to support forwarding of the
   encapsulation described in this document.

   If a router that is intended for use as a tunnel egress does not
   support the GRE-in-UDP encapsulation described in this document, it
   will not be listening on destination port [TBD].  In these cases, the
   router will conform to normal UDP processing and respond to the
   tunnel ingress with an ICMP message indicating "port unreachable"
   according to [RFC0792].  Upon receiving this ICMP message, the tunnel
   ingress MUST NOT continue to use GRE-in-UDP encapsulation toward this
   tunnel egress without management intervention.

6.  IANA Considerations

   IANA is requested to make the following allocation: Service Name:
   GRE-in-UDP Transport Protocol(s): UDP Assignee: IESG iesg@ietf.org
   Contact: IETF Chair chair@ietf.org Description: GRE-in-UDP
   Encapsulation Reference: [This.I-D] Port Number: TBD Service Code: N/
   A Known Unauthorized Uses: N/A Assignment Notes: N/A

7.  Security Considerations

7.1.  Vulnerability

   Neither UDP nor GRE encapsulation effects security for the payload
   protocol.  When using GRE-in-UDP, Network Security in a network is
   similar to that of a network using GRE.

   Use of ICMP for signaling of the GRE-in-UDP encapsulation capability
   adds a security concern.  Tunnel ingress devices may want to validate
   the origin of ICMP Port Unreachable messages before taking action.
   The mechanism for performing this validation is out of the scope of
   this document.

   In an instance where the UDP src port is not set based et the flow
   invariant fields from the payload header, a random port SHOULD be



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   selected in order to minimize the vulnerability to off-path attacks.
   [RFC6056] How the src port randomization occurs is outside scope of
   this document.

8.  Acknowledgements

   The Authors would like to thank Vivek Kumar, Ron Bonica, Joe Touch,
   Ruediger Geib, Gorry Fairhurst, and David Black for their review and
   valuable input on this draft.

9.  Contributing Authors

   The following people all contributed significantly to this document
   and are listed below in alphabetical order:

   John E. Drake
   Juniper Networks

   Email: jdrake@juniper.net

   Adrian Farrel
   Juniper Networks

   Email: adrian@olddog.co.uk

   Vishwas Manral
   Hewlett-Packard Corp.
   3000 Hanover St, Palo Alto.

   Email: vishwas.manral@hp.com

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

   EMail: cpignata@cisco.com

   Yongbing Fan
   China Telecom
   Guangzhou, China.
   Phone: +86 20 38639121









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10.  References

10.1.  Normative References

   [RFC0768]  Postel, J., "User Datagram Protocol", STD 6, RFC 768,
              August 1980.

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

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

   [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.

   [RFC2983]  Black, D., "Differentiated Services and Tunnels", RFC
              2983, October 2000.

   [RFC5405]  Eggert, L. and G. Fairhurst, "Unicast UDP Usage Guidelines
              for Application Designers", BCP 145, RFC 5405, November
              2008.

   [RFC6040]  Briscoe, B., "Tunnelling of Explicit Congestion
              Notification", RFC 6040, November 2010.

   [RFC6335]  Cotton, M., Eggert, L., Touch, J., Westerlund, M., and S.
              Cheshire, "Internet Assigned Numbers Authority (IANA)
              Procedures for the Management of the Service Name and
              Transport Protocol Port Number Registry", BCP 165, RFC
              6335, August 2011.

   [RFC6438]  Carpenter, B. and S. Amante, "Using the IPv6 Flow Label
              for Equal Cost Multipath Routing and Link Aggregation in
              Tunnels", RFC 6438, November 2011.

   [RFC6935]  Eubanks, M., Chimento, P., and M. Westerlund, "IPv6 and
              UDP Checksums for Tunneled Packets", RFC 6935, April 2013.

   [RFC6936]  Fairhurst, G. and M. Westerlund, "Applicability Statement
              for the Use of IPv6 UDP Datagrams with Zero Checksums",
              RFC 6936, April 2013.





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10.2.  Informative References

   [RFC0792]  Postel, J., "Internet Control Message Protocol", STD 5,
              RFC 792, September 1981.

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

   [RFC3931]  Lau, J., Townsley, M., and I. Goyret, "Layer Two Tunneling
              Protocol - Version 3 (L2TPv3)", RFC 3931, March 2005.

   [RFC4023]  Worster, T., Rekhter, Y., and E. Rosen, "Encapsulating
              MPLS in IP or Generic Routing Encapsulation (GRE)", RFC
              4023, March 2005.

   [RFC4364]  Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
              Networks (VPNs)", RFC 4364, February 2006.

   [RFC4884]  Bonica, R., Gan, D., Tappan, D., and C. Pignataro,
              "Extended ICMP to Support Multi-Part Messages", RFC 4884,
              April 2007.

   [RFC6790]  Kompella, K., Drake, J., Amante, S., Henderickx, W., and
              L. Yong, "The Use of Entropy Labels in MPLS Forwarding",
              RFC 6790, November 2012.

Authors' Addresses

   Edward Crabbe (editor)
   Google
   1600 Amphitheatre Parkway
   Mountain View, CA  94102
   US

   Email: edward.crabbe@gmail.com


   Lucy Yong (editor)
   Huawei USA
   5340 Legacy Drive
   San Jose, TX  75025
   US

   Email: lucy.yong@huawei.com







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   Xiaohu Xu (editor)
   Huawei Technologies
   Beijing
   China

   Email: xuxiaohu@huawei.com













































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