Encapsulating IPsec ESP in UDP for Load-balancing
draft-xu-ipsecme-esp-in-udp-lb-12

Network Working Group                                              X. Xu
Internet-Draft                                              China Mobile
Intended status: Standards Track                                S. Hegde
Expires: 27 September 2024                              Juniper Networks
                                                             B. Pismenny
                                                                  Nvidia
                                                                D. Zhang
                                                                  L. Xia
                                                                  Huawei
                                                           M. Puttaswamy
                                                        Juniper Networks
                                                           26 March 2024

           Encapsulating IPsec ESP in UDP for Load-balancing
                   draft-xu-ipsecme-esp-in-udp-lb-12

Abstract

   IPsec Virtual Private Network (VPN) is widely used by enterprises to
   interconnect their geographical dispersed branch office locations
   across the Wide Area Network (WAN) or the Internet, especially in the
   Software-Defined-WAN (SD-WAN) era.  In addition, IPsec is also
   increasingly used by cloud providers to encrypt IP traffic traversing
   data center networks and data center interconnect WANs so as to meet
   the security and compliance requirements, especially in financial
   cloud and governmental cloud environments.  To fully utilize the
   bandwidth available in the data center network, the data center
   interconnect WAN or the Internet, load balancing of IPsec traffic
   over Equal Cost Multi-Path (ECMP) and/or Link Aggregation Group (LAG)
   is much attractive to those enterprises and cloud providers.  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
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

Xu, et al.              Expires 27 September 2024               [Page 1]
Internet-Draft  Encapsulating ESP in UDP for Load-balanc      March 2024

   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 27 September 2024.

Copyright Notice

   Copyright (c) 2024 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 Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

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

1.  Introduction

   IPsec Virtual Private Network (VPN) is widely used by enterprises to
   interconnect their geographical dispersed branch office locations
   across the Wide Area Network (WAN) or the Internet, especially in the
   Software-Defined-WAN (SD-WAN) era.  In addition, IPsec is also
   increasingly used by cloud providers to encrypt IP traffic traversing
   data center networks and data center interconnect WANs so as to meet
   the security and compliance requirements, especially in financial
   cloud and governmental cloud environments.  To fully utilize the

Xu, et al.              Expires 27 September 2024               [Page 2]
Internet-Draft  Encapsulating ESP in UDP for Load-balanc      March 2024

   bandwidth available in the WAN or the Internet, load balancing of
   IPsec traffic over Equal Cost Multi-Path (ECMP) and/or Link
   Aggregation Group (LAG) is much attractive to those enterprises and
   cloud providers.  Although the ESP SPI field within the IPsec packets
   can be used as the load-balancing key, but it cannot be used by
   legacy switches and routers.

   Since most existing switches within data center networks and 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 data center switches and 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.

   IPsec VPN gateways are usually implemented in the form of multi-core
   x86 servers, especially in the public cloud environment.  Receive
   Side Scaling (RSS) is a widely adopted network driver technology
   which spreads incoming TCP or UDP traffic across multiple CPUs by
   performing hash function on the network and/or transport layer
   headers, resulting in increased multi-core efficiency and processor
   cache utilization.  By encapsulating ESP in UDP, it would facilate
   RSS to distribute the received IPsec traffic more evenly across
   multiple CPU cores.

   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
   [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
   traversal purpose and therefore the source port is set to a constant
   value (i.e., 4500).  In addition, the ESP-in-UDP encapsulation as
   described in this document is applicable to both the tunnel mode ESP
   encapsulation and the transport mode ESP encapsulation.

Xu, et al.              Expires 27 September 2024               [Page 3]
Internet-Draft  Encapsulating ESP in UDP for Load-balanc      March 2024

   There are use cases that do not use NAT traversal such as multi-cloud
   WAN.  ESP-in-UDP encapsulation along with NAT traversal is out of
   scope in this document.

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
         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 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,

Xu, et al.              Expires 27 September 2024               [Page 4]
Internet-Draft  Encapsulating ESP in UDP for Load-balanc      March 2024

         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:

      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.

Xu, et al.              Expires 27 September 2024               [Page 5]
Internet-Draft  Encapsulating ESP in UDP for Load-balanc      March 2024

   Similar to all other IP-based tunneling technologies, ESP-in-UDP
   encapsulation introduces overheads and reduces the effective Maximum
   Transmission 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:

      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

   If source port is generated using inner packet parameters, care
   should be taken to not reveal those parameters.  Including some
   random bytes along with the inner packet parameters will ensure the
   information of inner IP header is not revealed.

Xu, et al.              Expires 27 September 2024               [Page 6]
Internet-Draft  Encapsulating ESP in UDP for Load-balanc      March 2024

   Because packets are traversing different paths and the ESP sequence
   number is assigned sequencially by the encapsulator irrespective of
   the packet flow, the receiver might receive packets out-of-order and
   end up dropping them as delayed/out-of-order packets.  Based on the
   network speed and load, administrator should be able to adjust the
   replay window size or entirely disable the replay check.

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>.

   [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>.

Xu, et al.              Expires 27 September 2024               [Page 7]
Internet-Draft  Encapsulating ESP in UDP for Load-balanc      March 2024

   [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
   China Mobile
   Email: xuxiaohu_ietf@hotmail.com

   Shraddha Hegde
   Juniper Networks
   Email: shraddha@juniper.net

   Boris Pismenny
   Nvidia
   Email: borisp@nvidia.com

   Dacheng Zhang
   Huawei
   Email: dacheng.zhang@huawei.com

   Liang Xia
   Huawei
   Email: frank.xialiang@huawei.com

Xu, et al.              Expires 27 September 2024               [Page 8]
Internet-Draft  Encapsulating ESP in UDP for Load-balanc      March 2024

   Mahendra Puttaswamy
   Juniper Networks
   Email: mpmahendra@juniper.net

Xu, et al.              Expires 27 September 2024               [Page 9]