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Versions: 00 01 02 03

HIP                                                         R. Moskowitz
Internet-Draft                                            HTT Consulting
Updates: 8046 (if approved)                                      S. Card
Intended status: Standards Track                         A. Wiethuechter
Expires: 5 October 2020                                    AX Enterprize
                                                            3 April 2020


                         Fast HIP Host Mobility
                  draft-moskowitz-hip-fast-mobility-03

Abstract

   This document describes mobility scenarios and how to aggressively
   support them in HIP.  The goal is minimum lag in the mobility event.

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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   This Internet-Draft will expire on 5 October 2020.

Copyright Notice

   Copyright (c) 2020 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
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   Please review these documents carefully, as they describe your rights
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   as described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Simplified BSD License.





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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terms and Definitions . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Requirements Terminology  . . . . . . . . . . . . . . . .   3
     2.2.  Definitions . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Problem Space . . . . . . . . . . . . . . . . . . . . . . . .   3
     3.1.  Time to complete move . . . . . . . . . . . . . . . . . .   3
     3.2.  Apriori move knowledge  . . . . . . . . . . . . . . . . .   4
   4.  Enhanced availability of VIA_RVS  . . . . . . . . . . . . . .   4
   5.  Single move mobility  . . . . . . . . . . . . . . . . . . . .   4
     5.1.  Piggybacking impact on transport window size  . . . . . .   5
     5.2.  Environment . . . . . . . . . . . . . . . . . . . . . . .   5
     5.3.  Scenario 1: Neither host has data to transmit . . . . . .   5
     5.4.  Scenario 2: Host A has data to transmit . . . . . . . . .   5
       5.4.1.  IPv6 datagram + HIP UPDATE > MTU  . . . . . . . . . .   5
       5.4.2.  IPv6 datagram + HIP UPDATE <= MTU . . . . . . . . . .   6
     5.5.  Scenario 3: Host B has data to transmit . . . . . . . . .   6
       5.5.1.  IPv6 datagram + HIP UPDATE > MTU  . . . . . . . . . .   6
       5.5.2.  IPv6 datagram + HIP UPDATE <= MTU . . . . . . . . . .   6
   6.  Double-Jump mobility  . . . . . . . . . . . . . . . . . . . .   6
     6.1.  Environment . . . . . . . . . . . . . . . . . . . . . . .   6
     6.2.  Shotgunning UPDATEs . . . . . . . . . . . . . . . . . . .   7
     6.3.  Neither host has data to transmit . . . . . . . . . . . .   7
     6.4.  Either host has data to transmit  . . . . . . . . . . . .   7
       6.4.1.  IPv6 datagram + HIP UPDATE > MTU  . . . . . . . . . .   7
       6.4.2.  IPv6 datagram + HIP UPDATE <= MTU . . . . . . . . . .   7
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   9.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   8
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     10.1.  Normative References . . . . . . . . . . . . . . . . . .   8
     10.2.  Informative References . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   This document expands on HIP Host Mobility [RFC8046] to describe a
   set of mobility scenarios that can be addressed by mechanisms that
   accelerate the basic HIP mobility UPDATE exchange.

   HIP Host Mobility [RFC8046] performs a return address validation to
   ensure that the UPDATE address is reachable by the peer.  Two reasons
   are given for this approach: middleboxes blocking return reachability
   and malicious peers providing false address updates to flood a
   target.





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   The approach here is to start using the new address while it is being
   validated.  Worst case is a few packets are lost or sent to a wrong
   target.  These are acceptable risks while gaining a fast address
   update that works in most cases.

   One mechanism used is to piggyback data using Next Header even while
   the mobile peer address is flagged UNVERIFIED.  This is practical as
   the new peer address is authenticated by the HIP_MAC in UPDATE.  The
   UPDATE can neither be forged nor can it be replayed.  The
   verification is more to ensure reverse reachability particularly
   across NATs and firewalls.

   Another mechanism expands the use of the VIA_RVS parameter to
   "shotgun" mobility UPDATEs.  These and other optimizations will be
   covered in detail.

2.  Terms and Definitions

2.1.  Requirements Terminology

   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.

2.2.  Definitions

   MTU:  The Maximum Transmit Unit or maximum number of bytes in a
      datagram that the Interface supports.

   SPI:  The Security Parameter Index.

3.  Problem Space

3.1.  Time to complete move

   Most mobility environments are built with a "break then make" model
   for connectivity.  Thus there is measurable time between the old
   address being unusable and the new address being functional.  Adding
   mobility convergence times just further aggravates the delay which
   negatively impacts the user experience.

   The "make then break" model for connectivity is supported via HIP
   multihoming and is the subject of a separate recommendation.

   HIP mobility relies on a 3 packet UPDATE exchange which in some cases
   can be optimized to 2 packets.  This can be further delayed in a



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   "double-jump" scenario with waiting for the direct connection to fail
   before falling over to contacting the peer's RVS.  These processes
   have resulted in other technologies to be preferred over HIP as they
   have faster convergence even if they achieve this while sacrificing
   security.

3.2.  Apriori move knowledge

   A HIP Host that has the potential to 'move' (acquire a new address
   for an interface) during the lifetime of a HIP association SHOULD be
   registered to an RVS.  Such a HIP host SHOULD always inform its peer
   of its RVS address, as it may experience a "Double-Jump" move as in
   Section 6.

   In an RVS assisted base exchange, the Responder ensures the Initiator
   knows its RVS with the VIA_RVS parameter in the R1 as specified in
   HIP Rendezvous Extension [RFC8004].  However, the Responder has no
   mechanism to learn the Initiator's RVS address.  Additionally, it is
   possible for an Initiator to directly contact the Responder and thus
   not learn about the Responder's RVS in the base exchange.

   A host may not publish its RVS if it does not wish to be easily
   discovered.  It still should notify its peers of its RVS if it
   expects to be found in some move scenarios.

   The HIP base exchange needs to include more RVS information.

4.  Enhanced availability of VIA_RVS

   The VIA_RVS parameter is defined in HIP Rendezvous Extension
   [RFC8004] for use in R1, but only identifies the Responder's RVS to
   the Initiator when the I1 was routed through the RVS.

   Firstly, a Responder SHOULD always provide its VIA_RVS information in
   R1 even when the I1 came directly from the Initiator.  Secondly, the
   Initiator SHOULD always provide its VIA_RVS information in I2.  The
   VIA_RVS address is always maintained as part of the HIT to IP
   addressing information.  Through these two expansions in the
   availability of VIA_RVS, the hosts are assured to possess their
   peer's RVS address to "shotgun" UPDATEs and thus accelerate mobility.

5.  Single move mobility

   Data traffic between host A and B may use ESP with HIP [RFC7402] or
   any other tunneling protocol.  In ESP the relationship of the tunnel
   SAs with the HIP SA puts a high level of trust on the following fast
   mobility.




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5.1.  Piggybacking impact on transport window size

   The following sections define the operation of a HIP UPDATE payload
   followed by some transport (e.g.  TCP or UDP) payload in a single IP
   datagram.  This multicontent IP datagram works best with a smaller
   window size for the higher layer.  The normal operation is to compare
   the size of the transport datagram plus HIP UPDATE payload and ensure
   it is less than the MTU.  An implementation may be able to adjust the
   transport window size downward so that the higher layer could still
   fill it and the whole piece then still fit within the MTU.

5.2.  Environment

   *  Host A is mobile.

   *  Host B may be mobile, but not changing IP address at this time.

   *  Only Host A is moving in the network and changing its IP address.

   *  Host A and B share a HIP Security Association.

   *  Host A and B are registered to a RVS server, not necessarily the
      same and each has the others RVS address.

5.3.  Scenario 1: Neither host has data to transmit

   Host A triggers a HIP mobility UPDATE with Locator to inform Host B
   of new address.  Host B, upon validating Host A HIP UPDATE, continues
   with Address Verification.

5.4.  Scenario 2: Host A has data to transmit

5.4.1.  IPv6 datagram + HIP UPDATE > MTU

   Host A triggers a HIP mobility UPDATE with Locator to inform Host B
   of new address.  As the UPDATE + datagram would exceed the MTU, the
   datagram is sent separately after receipt of the HIP UPDATE from Host
   B.

   The HIP UPDATE packets vary in length as follows:

   Move notification:  302 bytes - UPDATE(ESP_INFO, LOCATOR, SEQ, HMAC,
      HIP_SIGNATURE)

   Move verification:  286 bytes - UPDATE(ESP_INFO, SEQ, ACK, HMAC,
      HIP_SIGNATURE, ECHO_REQUEST_UNSIGNED)





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   Verification ack:  262 bytes - UPDATE(ESP_INFO, ACK, HMAC,
      HIP_SIGNATURE, ECHO_RESPONSE_UNSIGNED)

5.4.2.  IPv6 datagram + HIP UPDATE <= MTU

   Host A sends HIP UPDATE with Locator to inform Host B of new address.
   Datagram is appended to HIP UPDATE using Next Header.  Host B, upon
   validating Host A HIP UPDATE, sends next header to proper module and
   continues with Address Verification.  This datagram is processed even
   though the address is UNVERIFIED.

   The ESP anti-replay window managed by its envelope sequence number
   can protect against replayed UPDATE+ESP packets prior to address
   verification.

5.5.  Scenario 3: Host B has data to transmit

   After Host B receives a HIP mobility UPDATE from A it has data to
   send to A.  Or Host B may have been sending data to Host A while Host
   A was moving.  The old data may have been lost; for example the data
   is over UDP with no keepalives during the move time.  The old data
   may be in a retransmission state; for example the data is over TCP.
   Or the data reached the interface from the higher layer at the same
   time that the HIP UPDATE with new locator was successfully processed.

5.5.1.  IPv6 datagram + HIP UPDATE > MTU

   Host B sends the HIP UPDATE validation followed by the IPv6 datagram.
   Host B may place the address in ACTIVE state or wait from HIP UPDATE
   confirmation from Host A.

5.5.2.  IPv6 datagram + HIP UPDATE <= MTU

   Host B sends the HIP UPDATE validation within the IPv6 datagram.
   Host B may place the address in ACTIVE state or wait from HIP UPDATE
   confirmation from Host A.

6.  Double-Jump mobility

   The HIP mobility UPDATE will fail without the use of RVS.  In fact
   both RVS are needed for both UPDATEs to find its peer.  This is why
   the "shotgun" acceleration SHOULD always be used when the peer's RVS
   is known.

6.1.  Environment

   *  Both host A and B are mobile.




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   *  Host A and B share a HIP Security Association.

   *  Both hosts move in the network and change their IP addresses.
      Before either receives the others HIP mobility UPDATE.

   *  Host A and B are registered to a RVS server, not necessarily the
      same and each has the others RVS address.

6.2.  Shotgunning UPDATEs

   Shotgunning is the process of sending the same UPDATE to more than
   one LOCATOR.  In particular it refers to sending the UPDATE to at
   least the peer's last known IP address and to its RVS address learned
   from the VIA_RVS for either the R1 or I2 packet.

   A host MUST be prepared to receive and discard multiple HIP mobility
   UPDATEs.  The duplicates will be readily identified as having the
   same SEQ (UPDATE sequence umber).

   Shotgunning SHOULD always be used when an RVS is known.  A peer never
   knows of a "double-jump" event until after it receives its peer's
   UPDATE.

6.3.  Neither host has data to transmit

   Host A triggers a HIP mobility UPDATE with Locator to inform Host B
   of new address.  Host B, upon validating Host A HIP UPDATE, continues
   with Address Verification.

   No attempt should be made to piggyback the two UPDATE processes.
   They may run simultaneously but not in the same IP datagrams.

6.4.  Either host has data to transmit

   The following acceleration advice presents a number of challenges.
   The best rule of thumb is to send the data as soon as possible.

6.4.1.  IPv6 datagram + HIP UPDATE > MTU

   Same process as Section 6.3

6.4.2.  IPv6 datagram + HIP UPDATE <= MTU

   Host A sends HIP UPDATE with Locator to inform Host B of new address.
   Datagram is appended to HIP UPDATE using Next Header.  Host B, may
   have already sent a datagram with its original HIP UPDATE.  If since
   then a receipt of Host A's UPDATE it has more data to transmit, upon
   validating Host A HIP UPDATE, sends next header to proper module and



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   continues with Address Verification.  This datagram is processed even
   though the address is UNVERIFIED.

7.  IANA Considerations

   The following change to the "Host Identity Protocol (HIP) Parameters"
   registries has been made:

   The PAYLOAD_MIC parameter used here is defined in HICCUPS which is an
   Experimental RFC.  Here it is being used in a Standards Track
   document.

8.  Security Considerations

   HIP fast mobility does not introduce any new security considerations
   beyond that in HIP Host Mobility [RFC8046].  If anything its
   requirement to know and use the RVS for a peer improve the frequency
   of a successful mobility notification.

9.  Acknowledgments

   The term "shotgun" for fast mobility comes from the InfraHIP project.
   The HIP UPDATE lengths were supplied by Jeff Ahrenholz.

   Sue Hares of Huawei and Jeff Ahrenholz of Tempered Networks
   contributed to the clarity in this document.

10.  References

10.1.  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>.

   [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>.

10.2.  Informative References

   [RFC7402]  Jokela, P., Moskowitz, R., and J. Melen, "Using the
              Encapsulating Security Payload (ESP) Transport Format with
              the Host Identity Protocol (HIP)", RFC 7402,
              DOI 10.17487/RFC7402, April 2015,
              <https://www.rfc-editor.org/info/rfc7402>.




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   [RFC8004]  Laganier, J. and L. Eggert, "Host Identity Protocol (HIP)
              Rendezvous Extension", RFC 8004, DOI 10.17487/RFC8004,
              October 2016, <https://www.rfc-editor.org/info/rfc8004>.

   [RFC8046]  Henderson, T., Ed., Vogt, C., and J. Arkko, "Host Mobility
              with the Host Identity Protocol", RFC 8046,
              DOI 10.17487/RFC8046, February 2017,
              <https://www.rfc-editor.org/info/rfc8046>.

Authors' Addresses

   Robert Moskowitz
   HTT Consulting
   Oak Park, MI 48237
   United States of America

   Email: rgm@labs.htt-consult.com


   Stuart W. Card
   AX Enterprize
   4947 Commercial Drive
   Yorkville, NY 13495
   United States of America

   Email: stu.card@axenterprize.com


   Adam Wiethuechter
   AX Enterprize
   4947 Commercial Drive
   Yorkville, NY 13495
   United States of America

   Email: adam.wiethuechter@axenterprize.com
















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