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Versions: 00                                                            
Network Working Group                                       D. Farinacci
Internet-Draft                                               lispers.net
Intended status: Experimental                                  V. Moreno
Expires: October 3, 2022                               P. Pillay-Esnault
                                                           April 1, 2022

                      LISP for Satellite Networks


   This specification describes how the LISP architecture and protocols
   can be used over satellite network systems.  The LISP overlay runs on
   earth using the satellite network system in space as the underlay.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on October 3, 2022.

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   document authors.  All rights reserved.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Definition of Terms . . . . . . . . . . . . . . . . . . . . .   5
   3.  Overview  . . . . . . . . . . . . . . . . . . . . . . . . . .   6
   4.  Mapping System  . . . . . . . . . . . . . . . . . . . . . . .   7
   5.  EID Mobility  . . . . . . . . . . . . . . . . . . . . . . . .   7
   6.  Satellite RLOCs and Underlay Routing  . . . . . . . . . . . .   7
   7.  Underlay Performance  . . . . . . . . . . . . . . . . . . . .   8
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     10.1.  Normative References . . . . . . . . . . . . . . . . . .   8
     10.2.  Informative References . . . . . . . . . . . . . . . . .   9
   Appendix A.  Acknowledgments  . . . . . . . . . . . . . . . . . .  10
   Appendix B.  Document Change Log  . . . . . . . . . . . . . . . .  10
     B.1.  Changes to draft-farinacci-lisp-satellite-network-00  . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  11

1.  Introduction

   This specification describes how a LISP overlay structure can run on
   top of a satellite network underlay.  The approach is similar to how
   [I-D.haindl-lisp-gb-atn] is used in Aeronautical Telecommunications
   Networks and [I-D.farinacci-lisp-mobile-network] is used in cellular

   This satellite deployment use-case requires no changes to the LISP
   architecture or standard protocol specifications.  In addition, any
   LISP implementations that run on a device with an existing satellite
   interface does not need to be upgraded.

   Even though an overlay should not concern itself with the operation
   of an underlay, the requirements from
   [I-D.lhan-problems-requirements-satellite-net] are considered but
   outside the scope of this document.

   The LISP overlay requirements are:

   1.  There will be no EID state in the satellite network underlay.

   2.  The satellite underlay is completely unaware of the overlay
       running over it.

   3.  The overlay requires the underlay network to deliver packets to
       RLOC addresses.

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   4.  The underlay network can transport IPv4 or IPv6 packets and can
       be dual-stack.

   5.  When path optimization in the underlay is available, an RLOC-
       record can be a source route of satellite hops.

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   The diagram below illustrates a 4 satellite system where each have
   Inter-Satellite-Links (ISLs) for connectivity between them and edge
   satellites with RF links to Ground Stations.  The EID connectivity to
   the xTRs is achieved via typical IP network connectivity where EIDs
   can be directly connected, one or more switch hops away, one or more
   router hops away, or any combination.

                             in space (underlay)
       |                                                              |
       |     sat     ISL     sat     ISL     sat     ISL     sat      |
       |    ))*((  -------  ))*((  -------  ))*((  -------  ))*((     |
       |      |                                               |       |
       |      |                                               |       |
       |      |up/down RF-link                 up/down RF-link|       |
       |      |                                               |       |
       |      |                                               |       |
              |                                               |
              |                                               |
              |               on earth (overlay)              |
       |      |                                               |       |
       |    GS-xTR             [mapping system]            GS-xTR     |
       |     /  \                                           /  \      |
       |    /    \                                         /    \     |
       |   /      \                                       /      \    |
       |  /        \                                     /        \   |
       | EIDs ... EIDs                                  EIDs ... EIDs |
       |                                                              |

                    Overlay on Earth, Underlay in Space

   The LISP mapping system runs on the earth-resident Internet and
   requires reachability by xTRs before LISP encapsulation can occur
   over the satellite network underlay.

   EIDs are known only to the overlay xTR nodes.  EIDs are not routable
   or require state in the satellite network.  This provides great value
   for scaling and EID mobility.

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2.  Definition of Terms

   Inter-Satellite-Links (ISLs):  are phased-array laser wireless links
      that transmit within or across orbits in space to other
      satellites.  They are different than satellite downlinks which are
      RF links to Ground-Stations.

   xTR:  is a LISP data-plane device. xTR is the general term for ITR,
      ETR, or RTR.  The formal and authoritative definition is in
      [I-D.ietf-lisp-rfc6830bis].  When a LISP xTR runs on a ground
      station device, it is called a GS-xTR.

   Ground-Station (GS):  is a device on the ground that has wireless
      links to a satellite node in space
      [I-D.lhan-problems-requirements-satellite-net].  When a Ground-
      Station is an LISP xTR, it encapsulates and decapsulates packets
      sent and received on satellite links according to the forwarding
      procedures in [I-D.ietf-lisp-rfc6830bis] and
      [I-D.ietf-lisp-rfc6833bis].  A GS can also be part of the
      satellite network system but isn't deployed as a GS-xTR.  In this
      scenario, the GS is part of the underlay and assumes the satellite
      network system, with its attached ground stations, deliver RLOC
      addressed packets.  When a satellite is in relay mode (not using
      ISLs), a LISP RTR can be used to support traffic engineering where
      a GS-ITR encapsulates through a single satellite hop to a GS-RTR
      which decapsulates and re-encapsulates through another single
      satellite hop to a GS-ETR.  See [I-D.ietf-lisp-te] for details,
      and how LISP-TE can also be used with multiple satellite hops.

   source-GS-xTR:  is the LISP ITR which does a mapping system lookup to
      obtain and cache the destination-RLOC for the destination-EID.  It
      then encapsulates the packet and sends it on the uplink whatever
      satellite that is in coverage range.

   destination-GS-xTR:  is the LISP ETR which receives a LISP
      encapsulated packet on the downlink from the satellite that is in
      coverage range over it.  The outer header is stripped and packet
      is delivered to local EID on the ground.

   EID:  defined as an Endpoint-ID in [I-D.ietf-lisp-rfc6830bis].  An
      EID is assigned to devices that reside behind GS-xTRs and are
      registered to the LISP mapping system with a satellite network
      address which is used as an RLOC.

   RLOC:  defined as a Routing Locator in [I-D.ietf-lisp-rfc6830bis].
      Within the scope of this specification, the RLOC is the satellite
      network address of a GS-xTR where the satellite network knows how
      to forward packets to this RLOC address.

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3.  Overview

   Here is how a packet flow sequence occurs from a source-EID to a
   destination-EID when the underlay is a satellite network:

   1.  source-EID originates an IP packet to a destination-EID.  The
       addresses in the packet are EIDs.

   2.  The packet travels to the GS-xTR (source-GS-xTR) via traditional
       IP routing.

   3.  The source-GS-xTR does a map-cache lookup for destination-EID to
       obtain the RLOC for the destination-GS-xTR.

   4.  If map-cache lookup fails, a mapping system lookup is performed
       for destination-EID.

   5.  The source-GS-xTR LISP encapsulates the packet and sends it on
       the uplink to the satellite.  The RLOC addresses in the outer
       header are source-GS-xTR and destination-GS-xTR.

   6.  The satellite network delivers the packet to Ground-Station
       addressed as destination-GS-xTR.

   7.  The destination-GS-xTR decapsulates the LISP packet by stripping
       the outer header and delivering the packet to the destination-EID
       on the ground.

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4.  Mapping System

   The LISP mapping system holds EID-to-RLOC-set mappings.  They are
   kept up to date by GS-xTRs and all the mechanisms from
   [I-D.ietf-lisp-rfc6833bis] are available for use.  The mappings can
   contain RLOCs that are not GS-xTRs thereby allowing load-splitting
   between both satellite and terrestrial paths.  The RLOC-set can also
   contain multicast RLOCs that can be reachable via satellite or
   terrestrial paths.

   All of IPv4, IPv6, and MAC EIDs can be registered to the mapping
   system to create multi-address-family L3 overlays as well as L2
   overlays on the satellite underlay.  That is, GS-xTR RLOCs can be
   used with these EID address types.

   Since the satellite network is not required to carry all routes that
   are earth-based, the LISP critical infrastructure will not be
   reachable by satellite nodes.  Therefore, the mapping system must be
   earth-based so xTRs which are not GS-xTRs can register and lookup
   mappings.  Note the satellite network is only required to carry
   routes for GS-xTR addresses.

   When satellite connectivity changes from a GS-xTR within its coverage
   range, the RLOC of the GS-xTR does not change.  Therefore, there is
   no need to update the mapping system when this happens.  This
   provides more scale to the total system since the LISP overlay is
   providing a level of indirection.

5.  EID Mobility

   EID-mobility [I-D.ietf-lisp-eid-mobility] is supported so devices can
   roam to other xTRs and are found by mapping system updates for remote
   xTRs encapsulating to the EID.  GS-xTRs learn EIDs on the ground
   dynamically via the mechanisms in [I-D.ietf-lisp-eid-mobility].

6.  Satellite RLOCs and Underlay Routing

   The address format of a GS-xTR RLOC depends on the design of the
   satellite network system.  The LISP RLOC formatting is flexible to
   accommodate new address types such as GPS coordinate based addressing
   or other forms of satellite addressing
   [I-D.lhan-satellite-semantic-addressing].  The only requirement is
   that they are routable by the satellite network system.

   If the satellite network supports IP forwarding and IP addresses are
   assigned to the RF-links on the GS-xTRs, then the satellite network
   just needs to make these "attachment point addresses" routable in the
   satellite network routing system.  And if the satellite network

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   desires to scale the route state in its routing system, it can use
   prefix aggregation, a local design matter to the satellite network
   routing system.  When this is the case, the RLOC is a standard AFI
   encoded IPv4 or IPv6 address.

   If the satellite network underlay supports a source-routing
   mechanism, as suggested in [I-D.lhan-satellite-instructive-routing],
   the same approach can be used as a LISP overlay on a terrestrial
   underlay running Segment Routing [RFC8754].  The source-route is
   encoded in an RLOC-record stored in the mapping system that is
   formatted as a list of satellite hop addresses.

7.  Underlay Performance

   The RLOC probing procedures in [I-D.ietf-lisp-rfc6833bis] can provide
   underlay telemetry measurement [I-D.farinacci-lisp-telemetry] so the
   overlay can tell how well the satellite network is performing.  And
   if the underlay under performs or telemetry metrics change, the GS-
   xTR can select another RLOC, possibly to a terrestrial RLOC.

8.  Security Considerations

   There are no specific security considerations at this time for this
   use-case.  However, existing LISP security functionality documented
   in [I-D.ietf-lisp-rfc6833bis], [I-D.ietf-lisp-sec],
   [I-D.ietf-lisp-eid-anonymity], and [I-D.farinacci-lisp-ecdsa-auth]
   can be used when the LISP overlay runs over a satellite network

   Data-plane encryption can be used to make the satellite underlay more
   secure.  See LISP Data-Plane Confidentiality [RFC8061] for more
   details.  This solution can work when packets take multiple satellite
   hops and/or Ground-Station hops.

9.  IANA Considerations

   There are no requests for IANA at this time.

10.  References

10.1.  Normative References

              Farinacci, D., Fuller, V., Meyer, D., Lewis, D., and A.
              Cabellos, "The Locator/ID Separation Protocol (LISP)",
              draft-ietf-lisp-rfc6830bis-36 (work in progress), November

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              Farinacci, D., Maino, F., Fuller, V., and A. Cabellos,
              "Locator/ID Separation Protocol (LISP) Control-Plane",
              draft-ietf-lisp-rfc6833bis-30 (work in progress), November

              Maino, F., Ermagan, V., Cabellos, A., and D. Saucez,
              "LISP-Security (LISP-SEC)", draft-ietf-lisp-sec-25 (work
              in progress), December 2021.

   [RFC1700]  Reynolds, J. and J. Postel, "Assigned Numbers", RFC 1700,
              DOI 10.17487/RFC1700, October 1994,

   [RFC8061]  Farinacci, D. and B. Weis, "Locator/ID Separation Protocol
              (LISP) Data-Plane Confidentiality", RFC 8061,
              DOI 10.17487/RFC8061, February 2017,

   [RFC8754]  Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J.,
              Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header
              (SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020,

10.2.  Informative References

              Farinacci, D. and E. Nordmark, "LISP Control-Plane ECDSA
              Authentication and Authorization", draft-farinacci-lisp-
              ecdsa-auth-03 (work in progress), September 2018.

              Farinacci, D., Pillay-Esnault, P., and U. Chunduri, "LISP
              for the Mobile Network", draft-farinacci-lisp-mobile-
              network-14 (work in progress), March 2022.

              Farinacci, D., Ouissal, S., and E. Nordmark, "LISP Data-
              Plane Telemetry", draft-farinacci-lisp-telemetry-07 (work
              in progress), November 2021.

              Haindl, B., Lindner, M., Moreno, V., Comeras, M. P.,
              Maino, F., and B. Venkatachalapathy, "Ground-Based LISP
              for the Aeronautical Telecommunications Network", draft-
              haindl-lisp-gb-atn-07 (work in progress), March 2022.

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              Farinacci, D., Pillay-Esnault, P., and W. Haddad, "LISP
              EID Anonymity", draft-ietf-lisp-eid-anonymity-12 (work in
              progress), March 2022.

              Comeras, M. P., Ashtaputre, V., Maino, F., Moreno, V., and
              D. Farinacci, "LISP L2/L3 EID Mobility Using a Unified
              Control Plane", draft-ietf-lisp-eid-mobility-09 (work in
              progress), January 2022.

              Farinacci, D., Kowal, M., and P. Lahiri, "LISP Traffic
              Engineering Use-Cases", draft-ietf-lisp-te-10 (work in
              progress), March 2022.

              Han, L., Li, R., Retana, A., Chen, M., Su, L., and N.
              Wang, "Problems and Requirements of Satellite
              Constellation for Internet", draft-lhan-problems-
              requirements-satellite-net-02 (work in progress), February

              Han, L., Retana, A., and R. Li, "Semantic Address Based
              Instructive Routing for Satellite Network", draft-lhan-
              satellite-instructive-routing-00 (work in progress), March

              Han, L., Li, R., Retana, A., Chen, M., and N. Wang,
              "Satellite Semantic Addressing for Satellite
              Constellation", draft-lhan-satellite-semantic-
              addressing-01 (work in progress), March 2022.

Appendix A.  Acknowledgments

   The authors would like to thank the LISP working group for their
   review of this specification.  A special thank you goes to Lin Han
   for email discussions on this topic.

Appendix B.  Document Change Log

B.1.  Changes to draft-farinacci-lisp-satellite-network-00

   o  Initial posting April 2022.

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Authors' Addresses

   Dino Farinacci
   San Jose, CA

   Email: farinacci@gmail.com

   Victor Moreno
   Mountain View, CA

   Email: victor@magooit.com

   Padma Pillay-Esnault
   Santa Clara, CA

   Email: padma.ietf@gmail.com

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