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Network Working Group                                              X. Xu
Internet-Draft                                                  D. Zhang
Intended status: Standards Track                                  L. Xia
Expires: May 28, 2018                                             Huawei
                                                       November 24, 2017


           Encapsulating IPsec ESP in UDP for Load-balancing
                   draft-xu-ipsecme-esp-in-udp-lb-01

Abstract

   IPsec Virtual Private Network (VPN) is widely used by enterprises to
   interconnect their geographical dispersed branch office locations
   across IP Wide Area Network (WAN) or the Internet, especially in the
   Software-Defined-WAN (SD-WAN) era.  To fully utilize the bandwidth
   available in IP WAN or the Internet, load balancing of traffic
   between different IPsec VPN sites over Equal Cost Multi-Path (ECMP)
   and/or Link Aggregation Group (LAG) is attractive to those
   enterprises deploying IPsec VPN solutions.  This document defines a
   method to encapsulate IPsec Encapsulating Security Payload (ESP)
   packets over UDP tunnels for improving load-balancing of IPsec ESP
   traffic.

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
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   Drafts is at https://datatracker.ietf.org/drafts/current/.

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   This Internet-Draft will expire on May 28, 2018.

Copyright Notice

   Copyright (c) 2017 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



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   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Encapsulation in UDP  . . . . . . . . . . . . . . . . . . . .   3
   4.  Processing Procedures . . . . . . . . . . . . . . . . . . . .   5
   5.  Congestion Considerations . . . . . . . . . . . . . . . . . .   5
   6.  Applicability Statements  . . . . . . . . . . . . . . . . . .   5
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   5
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     10.1.  Normative References . . . . . . . . . . . . . . . . . .   6
     10.2.  Informative References . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   IPsec Virtual Private Network (VPN) is widely used by enterprises to
   interconnect their geographical dispersed branch office locations
   across IP Wide Area Network (WAN) or the Internet, especially in the
   Software-Defined-WAN (SD-WAN) era.  To fully utilize the bandwidth
   available in IP WAN or the Internet, load balancing of traffic
   between different IPsec VPN sites over Equal Cost Multi-Path (ECMP)
   and/or Link Aggregation Group (LAG) is much attractive to those
   enterprises that deploy IPsec VPN solutions.  Since most existing
   core routers within IP WAN or the Internet can already support
   balancing IP traffic flows based on the hash of the five-tuple of UDP
   packets, by encapsulating IPsec Encapsulating Security Payload (ESP)
   packets over UDP tunnels with the UDP source port being used as an
   entropy field, it will enable existing core routers to perform
   efficient load-balancing of the IPsec ESP traffic without requiring
   any change to them.  Therefore, this specification defines a method
   of encapsulating IPsec ESP packets over UDP tunnels for improving
   load-balancing of IPsec ESP traffic.

   Encapsulating ESP in UDP, as defined in this document, can be used in
   both IPv4 and IPv6 networks.  IPv6 flow label has been proposed as an
   entropy field for load balancing in IPv6 network environment



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   [RFC6438].  However, as stated in [RFC6936], the end-to-end use of
   flow labels for load balancing is a long-term solution and therefore
   the use of load balancing using the transport header fields would
   continue until any widespread deployment is finally achieved.  As
   such, ESP-in-UDP encapsulation would still have a practical
   application value in the IPv6 networks during this transition
   timeframe.

   Note that the difference between the ESP-in-UDP encapsulation as
   proposed in this document and the ESP-in-UDP encapsulation as
   described in [RFC3948] is that the former uses the UDP tunnel for
   load-balancing improvement purpose and therefore the source port is
   used as an entropy field while the latter uses the UDP tunnel for NAT
   traverse purpose and therefore the source port is set to a constant
   value (i.e., 4500).  In addition, this document only discusses about
   the tunnel mode ESP encapsulation.

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 RFC 2119 [RFC2119].

2.  Terminology

   This memo makes use of the terms defined in [RFC2401]and [RFC2406].

3.  Encapsulation in UDP

   ESP-in-UDP encapsulation format is shown as follows:

        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |    Source Port = Entropy      |        Dest Port = TBD1       |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |           UDP Length          |        UDP Checksum           |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       ~                           ESP Packet                          ~
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                Figure 1: ESP-in-UDP Encapsulation Format

      Source Port of UDP:

         This field contains a 16-bit entropy value that is generated by
         the encapsulator to uniquely identify a flow.  What constitutes



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         a flow is locally determined by the encapsulator and therefore
         is outside the scope of this document.  What algorithm is
         actually used by the encapsulator to generate an entropy value
         is outside the scope of this document.

         In case the tunnel does not need entropy, this field of all
         packets belonging to a given flow SHOULD be set to a randomly
         selected constant value so as to avoid packet reordering.

         To ensure that the source port number is always in the range
         49152 to 65535 (Note that those ports less than 49152 are
         reserved by IANA to identify specific applications/protocols)
         which may be required in some cases, instead of calculating a
         16-bit hash, the encapsulator SHOULD calculate a 14-bit hash
         and use those 14 bits as the least significant bits of the
         source port field while the most significant two bits SHOULD be
         set to binary 11.  That still conveys 14 bits of entropy
         information which would be enough as well in practice.

      Destination Port of UDP:



         This field is set to a value (TBD1) allocated by IANA to
         indicate that the UDP tunnel payload is an ESP packet.

      UDP Length:



         The usage of this field is in accordance with the current UDP
         specification [RFC0768].

      UDP Checksum:



         For IPv4 UDP encapsulation, this field is RECOMMENDED to be set
         to zero for performance or implementation reasons because the
         IPv4 header includes a checksum and use of the UDP checksum is
         optional with IPv4.  For IPv6 UDP encapsulation, the IPv6
         header does not include a checksum, so this field MUST contain
         a UDP checksum that MUST be used as specified in [RFC0768] and
         [RFC2460] unless one of the exceptions that allows use of UDP
         zero-checksum mode (as specified in [RFC6935]) applies.

      ESP Packet:




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         This field contains one ESP packet.

4.  Processing Procedures

   This ESP-in-UDP encapsulation causes ESP [RFC2406] packets to be
   forwarded across IP WAN via "UDP tunnels".  When performing ESP-in-
   UDP encapsulation by an IPsec VPN gateway, ordinary ESP encapsulation
   procedure is performed and then a formatted UDP header is inserted
   between ESP header and IP header.  The Source Port field of the UDP
   header is filled with an entropy value which is generated by the
   IPsec VPN gateway.  Upon receiving these UDP encapsulated packets,
   remote IPsec VPN gateway MUST decapsulate these packets by removing
   the UDP header and then perform ordinary ESP decapsulation procedure
   consequently.

   Similar to all other IP-based tunneling technologies, ESP-in-UDP
   encapsualtion introduces overheads and reduces the effective Maximum
   Transmision Unit (MTU) size.  ESP-in-UDP encapsulation may also
   impact Time-to-Live (TTL) or Hop Count (HC) and Differentiated
   Services (DSCP).  Hence, ESP-in-UDP MUST follow the corresponding
   procedures defined in [RFC2003].

   Encapsulators MUST NOT fragment ESP packet, and when the outer IP
   header is IPv4, encapsulators MUST set the DF bit in the outer IPv4
   header.  It is strongly RECOMMENDED that IP transit core be
   configured to carry an MTU at least large enough to accommodate the
   added encapsulation headers.  Meanwhile, it is strongly RECOMMENDED
   that Path MTU Discovery [RFC1191] [RFC1981] or Packetization Layer
   Path MTU Discovery (PLPMTUD) [RFC4821] is used to prevent or minimize
   fragmentation.

5.  Congestion Considerations

   TBD.

6.  Applicability Statements

   TBD.

7.  Acknowledgements

8.  IANA Considerations

   One UDP destination port number indicating ESP needs to be allocated
   by IANA:






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      Service Name: ESP-in-UDP Transport Protocol(s):UDP
      Assignee: IESG <iesg@ietf.org>
      Contact: IETF Chair <chair@ietf.org>.
      Description: Encapsulate ESP packets in UDP tunnels.
      Reference: This document.
      Port Number: TBD1 -- To be assigned by IANA.

9.  Security Considerations

   TBD.

10.  References

10.1.  Normative References

   [RFC0768]  Postel, J., "User Datagram Protocol", STD 6, RFC 768,
              DOI 10.17487/RFC0768, August 1980,
              <https://www.rfc-editor.org/info/rfc768>.

   [RFC1191]  Mogul, J. and S. Deering, "Path MTU discovery", RFC 1191,
              DOI 10.17487/RFC1191, November 1990,
              <https://www.rfc-editor.org/info/rfc1191>.

   [RFC1981]  McCann, J., Deering, S., and J. Mogul, "Path MTU Discovery
              for IP version 6", RFC 1981, DOI 10.17487/RFC1981, August
              1996, <https://www.rfc-editor.org/info/rfc1981>.

   [RFC2003]  Perkins, C., "IP Encapsulation within IP", RFC 2003,
              DOI 10.17487/RFC2003, October 1996,
              <https://www.rfc-editor.org/info/rfc2003>.

   [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>.

   [RFC2401]  Kent, S. and R. Atkinson, "Security Architecture for the
              Internet Protocol", RFC 2401, DOI 10.17487/RFC2401,
              November 1998, <https://www.rfc-editor.org/info/rfc2401>.

   [RFC2406]  Kent, S. and R. Atkinson, "IP Encapsulating Security
              Payload (ESP)", RFC 2406, DOI 10.17487/RFC2406, November
              1998, <https://www.rfc-editor.org/info/rfc2406>.

   [RFC2460]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460,
              December 1998, <https://www.rfc-editor.org/info/rfc2460>.




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   [RFC4821]  Mathis, M. and J. Heffner, "Packetization Layer Path MTU
              Discovery", RFC 4821, DOI 10.17487/RFC4821, March 2007,
              <https://www.rfc-editor.org/info/rfc4821>.

   [RFC6438]  Carpenter, B. and S. Amante, "Using the IPv6 Flow Label
              for Equal Cost Multipath Routing and Link Aggregation in
              Tunnels", RFC 6438, DOI 10.17487/RFC6438, November 2011,
              <https://www.rfc-editor.org/info/rfc6438>.

   [RFC6935]  Eubanks, M., Chimento, P., and M. Westerlund, "IPv6 and
              UDP Checksums for Tunneled Packets", RFC 6935,
              DOI 10.17487/RFC6935, April 2013,
              <https://www.rfc-editor.org/info/rfc6935>.

   [RFC6936]  Fairhurst, G. and M. Westerlund, "Applicability Statement
              for the Use of IPv6 UDP Datagrams with Zero Checksums",
              RFC 6936, DOI 10.17487/RFC6936, April 2013,
              <https://www.rfc-editor.org/info/rfc6936>.

10.2.  Informative References

   [RFC3948]  Huttunen, A., Swander, B., Volpe, V., DiBurro, L., and M.
              Stenberg, "UDP Encapsulation of IPsec ESP Packets",
              RFC 3948, DOI 10.17487/RFC3948, January 2005,
              <https://www.rfc-editor.org/info/rfc3948>.

Authors' Addresses

   Xiaohu Xu
   Huawei

   Email: xuxiaohu@huawei.com


   Dacheng Zhang
   Huawei

   Email: dacheng.zhang@huawei.com


   Liang Xia
   Huawei

   Email: frank.xialiang@huawei.com







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