LISP Map Server Reliable Transport
draft-kouvelas-lisp-map-server-reliable-transport-04

Network Working Group                                          C. Cassar
Internet-Draft                                                  J. Leong
Intended status: Experimental                                   D. Lewis
Expires: March 29, 2018                                    Cisco Systems
                                                             I. Kouvelas
                                                    Arista Networks Inc.
                                                               J. Arango
                                                               Microsoft
                                                      September 25, 2017


                   LISP Map Server Reliable Transport
        draft-kouvelas-lisp-map-server-reliable-transport-04.txt

Abstract

   The communication between LISP ETRs and Map-Servers is based on
   unreliable UDP message exchange coupled with periodic message
   transmission in order to maintain soft state.  The drawback of
   periodic messaging is the constant load imposed on both the ETR and
   the Map-Server.  New use cases for LISP have increased the amount of
   state that needs to be communicated with requirements that are not
   satisfied by the current mechanism.  This document introduces the use
   of a reliable transport for ETR to Map-Server communication in order
   to eliminate the periodic messaging overhead, while providing
   reliability, flow-control and endpoint liveness detection.

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 March 29, 2018.








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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
   (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
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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Requirements Notation . . . . . . . . . . . . . . . . . . . .   3
   3.  Message Format  . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  Session Establishment . . . . . . . . . . . . . . . . . . . .   5
   5.  Error Notifications . . . . . . . . . . . . . . . . . . . . .   5
   6.  EID Prefix Registration . . . . . . . . . . . . . . . . . . .   7
     6.1.  Reliable Mapping Registration Messages  . . . . . . . . .   7
       6.1.1.  Registration Message  . . . . . . . . . . . . . . . .   8
       6.1.2.  Registration Acknowledgement Message  . . . . . . . .   8
       6.1.3.  Registration Rejection Message  . . . . . . . . . . .   9
       6.1.4.  Registration Refresh Message  . . . . . . . . . . . .  10
       6.1.5.  Mapping Notification Message  . . . . . . . . . . . .  12
     6.2.  ETR Behavior  . . . . . . . . . . . . . . . . . . . . . .  13
     6.3.  Map-Server Behavior . . . . . . . . . . . . . . . . . . .  17
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  18
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  18
     8.1.  LISP Reliable Transport Message Types . . . . . . . . . .  18
     8.2.  Transport Protocol Port Numbers . . . . . . . . . . . . .  18
   9.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  18
   10. Normative References  . . . . . . . . . . . . . . . . . . . .  19
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  19

1.  Introduction

   The communication channel between LISP ETRs and Map-Servers is based
   on unreliable UDP message exchange [RFC6833].  Where required,
   reliability is pursued through periodic retransmissions that maintain
   soft state on the peer.  Map-Register messages are retransmitted
   every minute by an ETR and the Map-Server times out its state if the
   state is not refreshed for three successive periods.  When
   registering multiple EID-Prefixes, the ETR includes multiple mapping



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   records in the Map-Register message.  Packet size limitations provide
   an upper bound to the number of mapping records that can be placed in
   each Map-Register message.  When the ETR has more EID-Prefixes to
   register than can be packed in a single Map-Register message, the
   mapping records for the EID-Prefixes are split across multiple Map-
   Register messages.

   The drawback of the periodic registration is the constant load that
   it introduces on both the ETR and the Map-Server.  The ETR uses
   resources to periodically build and transmit the Map-Register
   messages, and to process the resulting Map-Notify messages issued by
   the Map-Server.  The Map-Server uses resources to process the
   received Map-Register messages, update the corresponding registration
   state, and build and transmit the matching Map-Notify messages.  When
   the number of EID-Prefixes to be registered by an ETR is small, the
   resulting load imposed by periodic registrations may not be
   significant.  The ETR will only transmit a single Map-Register
   message each period that contains a small number of mapping records.

   In some LISP deployments, a large set of EID-Prefixes must be
   registered by each ETR (e.g. mobility, database redistribution).  Use
   cases with a large set of EID-Prefixes behind an ETR will result in a
   much higher load.  An example is LISP mobility deployments where EID-
   Prefixes are limited to host entries.  ETRs may have thousands of
   hosts to register resulting in hundreds of Map-Register and Map-
   Notify messages per registration period.

   A transport is required for the ETR to Map-Server communication that
   provides reliability, flow-control and endpoint liveness
   notifications.  This document describes the use of TCP or SCTP as a
   LISP reliable transport.  The initial application for the LISP
   reliable transport session is the support of scalable EID prefix
   registration.  The reliable session mechanism is defined to be
   extensible so that it can support additional LISP communication
   requirements as they arise using a single reliable transport session
   between an ETR and a Map-Server.  The use of the reliable transport
   session for EID prefix registration is an alternative and does not
   replace the existing UDP based mechanism.

2.  Requirements Notation

   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].







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3.  Message Format

   A single LISP reliable transport session may carry information for
   multiple LISP applications.  One such application is the registration
   of EID to RLOC mappings that operates over a session between an ETR
   and a Map-Server.  Communication over a session is based on the
   exchange of messages.  This document defines a base set of messages
   to support session establishment and management.  It also defines the
   messages for the EID to RLOC mapping registration application.

   To support protocol extensibility when new applications, or
   extensions to existing applications are introduced, the messages are
   based on a TLV format.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             Type              |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           Message ID                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Message Data                       ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Message End Marker                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                     Reliable transport message format

   o  Type: 16 bit type field identifying the message type.

   o  Length: 16 bit field that provides the total size of the message
      in octets including the length, type and end marker fields.  The
      length allows the receiver to locate the next message in the TCP
      stream.  The minimum value of the length field is 8.

   o  ID: A 32-bit value that identifies the message.  May be used by
      the receiver to identify the message in replies or notification
      messages.

   o  Data: Type specific message contents.

   o  End Marker: A 32-bit message end marker that must be set to
      0x9FACADE9.  The End Marker is used by the receiver to validate
      that it has correctly parsed or skipped a message and provides a
      method to detect formatting errors.  Note that message data may
      also contain this marker, and that the marker itself is not
      sufficient for parsing the message.




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   The base message format does not indicate how the peer should deal
   with the message in cases where the message type is not supported/
   understood.  This is best dealt with by the application.  For
   example, in case an error notification is returned, or an expected
   acknowledgement message is not received, the application might choose
   various courses of action; from simply logging that the feature is
   not supported, all the way to tearing the relationship with the peer
   down for the feature, or for all LISP features.

4.  Session Establishment

   To ensure backwards compatibility, the map server and ETR MUST
   communicate via unreliable UDP messages until a TCP session between
   the two is successfully established.

   The map server authenticates the ETR with the authentication data
   contained in the first UDP map-register message it receives from the
   ETR.  Once the ETR is authenticated, the map server performs a
   passive open by listening on TCP port 4342, and does not qualify the
   remote port.  As a security measure, the map server accepts TCP
   connections only from those ETRs that have been authenticated via UDP
   map-register messages.

   The ETR assumes the active role of the TCP session establishment by
   connecting to the map server once it has received a UDP map-notify
   message.

   When a TCP session goes down, UDP authentication must take place
   before a new TCP session is established.  The map-server will not
   accept a connection from the ETR until a UDP map-register has been
   received.  Similarly, the ETR will not attempt to establish a session
   with the map server until an UDP map-notify message has been
   received.

   A single reliable transport session is established between the map
   server and the ETR to cover all communication needs.  For example, an
   ETR that has EID prefix registrations for multiple EID instances and
   EID address families will only establish a single session with the
   map server.

5.  Error Notifications

   The error notification message is used to communicate base reliable
   transport session communication errors.  LISP applications making use
   of the reliable transport session and having to communicate
   application specific errors must define their own messages to do so.
   An error notification is issued when the receiver of a message does
   not recognize the message type or cannot parse the message contents.



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   The notification includes the offending message type and ID and as
   much of the offending message data as the notification sender wishes
   to.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           Type = 16           |            Length             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           Message ID                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Error Code    |                   Reserved                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Offending Message Type     |    Offending Message Length   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Offending Message ID                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                    Offending Message Data                   ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Message End Marker                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                     Error Notification message format

   o  Error Code: An 8 bit field identifying the type of error that
      occurred.  Defined errors are:

      *  Unrecognized message type.

      *  Message format error.

   o  Reserved: Set to zero by the sender and ignored by the receiver.

   o  Offending Message Type: 16 bit type field identifying the message
      type of the offending message that triggered this error
      notification.  This is copied from the Type field of the offending
      message.

   o  Offending Message Length: 16 bit field that provides the total
      size of the offending message in octets.  This is copied from the
      Length field of the offending message.

   o  Offending Message ID: A 32-bit field that is set to the Message ID
      field of the offending message.

   o  Offending Message Data: The Data from the offending message that
      triggered this error notification.  The sender of the notification
      may include as much of the original data as is deemed necessary.



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      The length of the Offending Message Data field is not provided by
      the Offending Message Length field and is determined by
      subtracting the size of the other fields in the message from the
      Length field.  It is valid to not include any of the offending
      message data when sending an error notification.

   o  End Marker: A 32-bit message end marker that must be set to
      0x9FACADE9.  The End Marker is used by the receiver to validate
      that it has correctly parsed or skipped a message and provides a
      method to detect formatting errors.  Note that message data may
      also contain this marker, and that the marker itself is not
      sufficient for parsing the message.

   An error notification cannot be the offending message in another
   error notification and MUST NOT trigger such a message.

6.  EID Prefix Registration

   EID prefix registration uses the reliable transport session between
   an ETR and a Map-Server to communicate the ETR local EID database EID
   to RLOC mappings to the Map-Server.  In contrast to the UDP based
   periodic registration, mapping information over the reliable
   transport session is only sent when there is new information
   available for the Map-Server.  The Map-Server does not maintain a
   timer to expire registrations communicated over the reliable
   transport session.  Instead an explicit de-registration (a
   registration carrying a zero TTL) is needed to delete the state
   maintained by the Map-Server.

   The key used to identify registration mapping records in the ETR to
   Map-Server communication is the EID prefix.  The prefix may be
   specified using an LCAF encoding that includes an EID instance ID.

   When the reliable transport session goes down, registration mappings
   learned by the Map-Server are treated as periodic UDP registrations
   and a timer is used to expire them after 3 minutes.  During this
   period UDP based registrations or the re-establishment of the
   reliable transport session and subsequent communication of a new
   mapping can update the EID prefix mapping state.

6.1.  Reliable Mapping Registration Messages

   This section defines the LISP reliable transport session messages
   used to communicate local EID database registrations between the ETR
   and the Map-Server.






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6.1.1.  Registration Message

   The reliable transport registration message is used to communicate
   EID to RLOC mapping registrations from the ETR to the Map-Server.  To
   increase code reuse, the "Message Data" field uses the same format as
   the UDP Map-Registers but without the IP and UDP headers.  A reliable
   registration message MUST contain a single mapping-record.  The map
   server MUST discard any reliable registration message that contains
   more than one mapping record.

   The reliable transport session is authenticated by means of the
   session establishment procedure.  Thus, although the Map-Register
   MUST carry the authentication data, it is up to the map server to
   determine if each individual reliable registration message should be
   authenticated.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           Type = 17           |            Length             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           Message ID                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Map-Register message                   ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ...                    Map-Register message                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Message End Marker                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                        Registration message format

6.1.2.  Registration Acknowledgement Message

   The Acknowledgement message is sent from the Map-Server to the ETR to
   confirm successful registration of an EID prefix previously
   communicated by a reliable transport session Registration message.
   The Registration Acknowledgement message does not carry a mapping
   record (the map servers view of the mapping).  This is accomplished
   by the LISP reliable transport Map Notification message.











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    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           Type = 18           |            Length             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           Message ID                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Prefix-Length |       EID-Prefix-AFI          | EID-Prefix  ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Message End Marker                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                Registration Acknowledgement message format

   o  Prefix-Length: Mask length for the EID prefix.

   o  EID-Prefix AFI: Address family identifier for the EID prefix in
      the following field.

   o  EID-Prefix: The EID prefix from the received Registration.

6.1.3.  Registration Rejection Message

   The Registration Rejection Message is sent by the map server to the
   ETR to indicate that the registration of a specific EID prefix is
   being rejected or withdrawn.  A rejection refers to a recently-sent
   registration that is being immediately rejected.  A withdrawal refers
   to a previously accepted registration that is no longer acceptable,
   perhaps due to a configuration change in the map-server.  The ETR
   must keep track of rejected EID prefixes and be prepared to re-
   register their mappings when requested through a registration refresh
   message.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           Type = 19           |            Length             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           Message ID                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Reason    |           Reserved            | Prefix-Length |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |        EID-Prefix-AFI         |          EID-Prefix         ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Message End Marker                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                   Registration Rejection message format



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   o  Reason: Code identifying the reason for which the Map-Server
      rejected or withdrew the registration.

      *  1 - Not a valid site EID prefix.

      *  2 - Authentication failure.

      *  3 - Locator set not allowed.

      *  4 - Used to cover reason that's not defined.

   o  Reserved: This field is reserved for future use.  Set to zero by
      the sender and ignored by the receiver.

   o  Prefix-Length: Mask length for the EID prefix.

   o  EID-Prefix-AFI: Address family identifier for the EID prefix in
      the following field.

   o  EID-Prefix: The EID prefix being rejected or withdrawn.

6.1.4.  Registration Refresh Message

   Sent by the Map-Server to the ETR to request the (re-)transmission of
   EID prefix database mapping Registration messages.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           Type = 20           |            Length             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           Message ID                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Scope    |R|          Reserved           | Prefix-Length |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |        EID-Prefix-AFI         |          EID-Prefix         ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Message End Marker                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                    Registration Refresh message format

   o  Scope: Determines the set of registrations being refreshed.

      *  0 - All prefixes under all address families under all EID
         instances are being refreshed.  When using this scope the
         Prefix-Length, EID-Prefix-AFI, and EID-Prefix fields MUST be
         omitted.  That is, the Message End Marker follows immediately



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         after the Reserved field.  The total length of the message MUST
         be 15 bytes.

      *  1 - All prefixes under all address families under a single EID
         instance are being refreshed.  The Prefix-Length MUST be set to
         zero, EID-Prefix-AFI MUST be set to LCAF type, the EID-Prefix
         encodes the LCAF Instance ID, the LCAF address AFI MUST be set
         to UNSPECIFIED.  The total length of the message MUST be 30
         bytes.

      *  2 - All prefixes under a single address family under a single
         EID instance are being refreshed.  The Prefix-Length MUST be
         set to zero, the EID-Prefix-AFI MUST be set to LCAF type and
         the EID-Prefix MUST encode the Instance ID.  The LCAF address
         AFI MUST specify the address family to refresh, the actual
         address SHOULD be set to zero.

      *  3 - All prefixes covered by a specific EID prefix in a single
         EID instance is being refreshed.  The Prefix-Length, EID-
         Prefix-AFI and EID prefix MUST be encoded accordingly.

      *  4 - A specific EID prefix in a single EID instance is being
         refreshed.  The Prefix-Length, EID-Prefix-AFI and EID prefix
         MUST be encoded accordingly.

      The map-server has the flexibility to control the granularity of
      the refresh by issuing refresh with different scopes.  It can send
      a single refresh with a coarse scope or send individual refreshes
      with narrower scope.  The ETR MUST be able to process all scopes
      to ensure the map-server registration states are synchronized with
      the ETR.

   o  R: Request from the ETR to only refresh registrations that have
      been previously rejected by the Map-Server.  If the R bit is set
      then the scope cannot have a value of 3 and the EID-Prefix and
      Prefix-Length fields must be omitted.

   o  Reserved: This field is reserved for future use.  Set to zero by
      the sender and ignored by the receiver.

   o  Prefix-Length: Mask length for the EID prefix.  Refer to scope for
      more details.

   o  EID-Prefix-AFI: Address family identifier for the EID prefix in
      the following field.  Refer to scope for more details.

   o  EID-Prefix: The EID prefix being refreshed.  Refer to scope for
      more details.



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6.1.5.  Mapping Notification Message

   Mapping Notification messages communicate the Map-Server view of the
   mapping for an EID prefix and no longer serve as a registration
   acknowledgement.  Mapping Notifications do not need message level
   authentication as they are received over a reliable transport session
   to a known Map-Server.  Note that reliable transport Mapping
   Notification messages do not reuse the UDP Map-Notify message format.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           Type = 21           |            Length             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           Message ID                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       xTR-ID 128 bits                       ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       xTR-ID 128 bits                       ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       xTR-ID 128 bits                       ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       xTR-ID 128 bits                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       site-ID 64 bits                       ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       site-ID 64 bits                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                         Mapping Record                      ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ...                       Mapping Record                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Message End Marker                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                    Mapping Notification message format

   o  xTR-ID: xTR-ID taken from the last valid registration the map-
      server received for the EID-prefix conveyed in the mapping record.

   o  site-ID: site-ID taken from the last valid registration the map-
      server received for the EID-prefix conveyed in the mapping record.

   o  Mapping Record: Mapping record of the EID-prefix the map-server is
      conveying to the ETR.






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6.2.  ETR Behavior

   The ETR operates the following per EID prefix, per MS state machine
   that defines the reliable transport EID prefix registration behavior.

   There are five states:

   o  No state: The local EID database prefix does not exist.

   o  Periodic: The local EID database prefix is being periodically
      registered through UDP Map-Register messages as specified in [].

   o  Stable: From the ETR's perspective, no registrations are due to be
      sent to the peer.  The session to the peer is up, and the peer has
      either acknowledged the registration, or is expected to request a
      refresh in the future.

   o  AckWait: A Registration message for the prefix has been
      transmitted to the Map-Server and the ETR is waiting for either a
      Registration Acknowledge or Registration Rejected reply from the
      Map-Server.

   o  Reject: The reliable transport registration for the local EID
      database prefix was rejected by the Map-Server.  From the ETR's
      perspective, no registration is due to the peer AND the peer is
      known to have rejected the registration.

   The following events drive the state transitions:

   o  DB creation: The local EID database entry for the EID prefix is
      created.

   o  DB deletion: The local EID database entry for the EID prefix is
      deleted.

   o  DB change: The mapping contents or authentication information for
      the local EID database entry changes.

   o  Session up: The reliable transport session to the Map-Server is
      established.

   o  Session down: The reliable transport session the Map-Server goes
      down.

   o  Recv Refresh: A Registration refresh message is received from the
      Map-Server.





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   o  Recv ACK: A Registration Acknowledge message is received from the
      Map-Server.

   o  Recv Rejected: A Registration Rejected message is received from
      the Map-Server.

   o  Periodic timer: The timer that drives generation of periodic UDP
      Map-Register messages fires.

   The state machine is:









































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   +--------------------+--------------------------------------+
   |                    |              Prev State              |
   |  Event             +-------------------+------------------+
   |                    |   No state        |    Periodic      |
   +--------------------+-------------------+------------------+
   |  DB creation       |   -> Periodic     |    N/A           |
   |  [session down]    |   A1              |                  |
   +--------------------+-------------------+------------------+
   |  DB creation       |   -> AckWait      |    N/A           |
   |  [session up]      |   A2              |                  |
   +--------------------+-------------------+------------------+
   |  DB deletion       |   N/A             |    -> No state   |
   |                    |                   |    A3            |
   +--------------------+-------------------+------------------+
   |  DB change         |   N/A             |    -             |
   |                    |                   |    A1            |
   +--------------------+-------------------+------------------+
   |  Session up        |   -               |    -> Stable     |
   |                    |                   |    A4            |
   +--------------------+-------------------+------------------+
   |  Session down      |   -               |    N/A           |
   |                    |                   |                  |
   +--------------------+-------------------+------------------+
   |  Recv Refresh      |   -               |    N/A           |
   |                    |                   |                  |
   +--------------------+-------------------+------------------+
   |  Recv Refresh      |   -               |    N/A           |
   |  [rejected]        |                   |                  |
   +--------------------+-------------------+------------------+
   |  Recv ACK          |   -               |    N/A           |
   |                    |                   |                  |
   +--------------------+-------------------+------------------+
   |  Recv Rejection    |   -               |    N/A           |
   |                    |                   |                  |
   +--------------------+-------------------+------------------+
   |  Timer             |   N/A             |    -             |
   |                    |                   |    A5            |
   +--------------------+-------------------+------------------+

                  xTR per EID prefix per MS state machine











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   +-----------------+-----------------------------------------------+
   |                 |                   Prev State                  |
   | Event           +---------------+---------------+---------------+
   |                 |    Stable     |   AckWait     |   Rejected    |
   +-----------------+---------------+---------------+---------------+
   | DB creation     | N/A           | N/A           | N/A           |
   |                 |               |               |               |
   +-----------------+---------------+---------------+---------------+
   | DB deletion     | -> No state   | -> No state   | -> No state   |
   |                 | A6            | A6            |               |
   +-----------------+---------------+---------------+---------------+
   | DB change       | -> AckWait    | -             | -> AckWait    |
   |                 | A2            | A2            | A2            |
   +-----------------+---------------+---------------+---------------+
   | Session up      | N/A           | N/A           | N/A           |
   |                 |               |               |               |
   +-----------------+---------------+---------------+---------------+
   | Session down    | -> Periodic   | -> Periodic   | -> Periodic   |
   |                 | A7            | A7            | A7            |
   +-----------------+---------------+---------------+---------------+
   | Recv Refresh    | -> AckWait    | -             | -> AckWait    |
   |                 | A2            | A2            | A2            |
   +-----------------+---------------+---------------+---------------+
   | Recv Refresh    | -             | -             | -> AckWait    |
   | [rejected]      |               | A2            | A2            |
   +-----------------+---------------+---------------+---------------+
   | Recv ACK        | -             | -> Stable     | -> AckWait    |
   |                 |               |               | A2            |
   +-----------------+---------------+---------------+---------------+
   | Recv Rejection  | -> Rejected   | -> Rejected   | -             |
   |                 |               |               |               |
   +-----------------+---------------+---------------+---------------+
   | Timer           | N/A           | N/A           | N/A           |
   |                 |               |               |               |
   +-----------------+---------------+---------------+---------------+

                  xTR per EID prefix per MS state machine

   Action descriptions:

   o  A1: Start periodic registration timer with zero delay.

   o  A2: Send Registration over reliable transport session.

   o  A3: Send UDP registration with zero TTL.

   o  A4: Stop periodic registration timer.




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   o  A7: Send UDP registration and start periodic registration timer
      with registration period.

   o  A6: Send Registration with TTL zero over reliable transport
      session.

   o  A7: Start periodic registration timer with registration period.

   All timer start actions must be jittered.

   When the reliable transport session is established the ETR moves the
   state machine into the Stable state without first registering the EID
   prefix over the reliable transport session.  The map server will send
   a refresh message with a scope of 0 that will trigger the
   registration message to be sent.  Because other applications may be
   using the reliable session, the refresh message signals the ETR that
   the map server supports reliable map registration messages.  This
   model will also allow future optimizations where the Map-Server may
   retain registration state from a previous instantiation of the
   reliable transport session with the ETR and only request the refresh
   of EID prefix state beyond some negotiated session progress marker.

   Aa Map-Server authentication key change is treated as a DB change
   event and will result in triggering a new Registration message to be
   transmitted.

6.3.  Map-Server Behavior

   Received registrations create/update or delete mapping state.

   A refresh with global scope is sent when a session between the ETR
   and map-server is first established so the map-server can obtain the
   complete database contents from the ETR.  This refresh is also
   serving as a capability signaling from the map-server to the ETR that
   it can support reliable registration.

   Refresh for rejected registrations sent (R bit set) when a new EID
   prefix is configured on the Map-Server.

   Refresh is sent whenever authentication key is changed or EID prefix
   is deconfigured.  Upon reception of the registration map-server can
   decide whether to acknowledge the registration or issue rejection.

   Mapping Notification message sent whenever the mapping for a
   registered or more specific prefix for which notifications are
   requested changes.  ETR acknowledgement or rejection messaging for
   Mapping Notification is not required because the ETR decides how to
   process the message based on the registered mapping information.  If



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   the mapping information changes the resulting registration will
   trigger a new Mapping Notification message from the Map-Server.

7.  Security Considerations

   The LISP reliable transport session SHOULD be authenticated.  On
   controlled RLOC networks that can guarantee that the source RLOC
   address of data packets cannot be spoofed, the authentication check
   can be a source address validation on the reliable transport packets.
   When the RLOC network does not provide such guarantees, reliable
   transport authentication SHOULD be used.  Implementations SHOULD
   support the TCP Authentication Option (TCP-AO) [RFC5925] and SCTP
   Authenticated Chunks [RFC4895].

8.  IANA Considerations

8.1.  LISP Reliable Transport Message Types

   Assignment of new LISP reliable transport message types is done
   according to the "IETF Review" model defined in [RFC5266].

   The initial content of the registry should be as follows.

   Type         Name                                      Reference
   -----------  ----------------------------------------  --------------
   0-15         Reserved                                  This document
   16           Error Notification                        This document
   17           Registration Message                      This document
   18           Registration Acknowledgement Message      This document
   19           Registration Rejected Message             This document
   20           Registration Refresh Message              This document
   21           Mapping Notification Message              This document
   22-30        Reserved for EID membership distribution  TBD
   31-64999     Unassigned
   65000-65535  Reserved for Experimental Use

8.2.  Transport Protocol Port Numbers

   TCP port 4342 already reserved for LISP CONS that is now obsolete.
   Repurpose for reliable transport over TCP.  Reserve an SCTP port.

9.  Acknowledgments

   The authors would like to thank Noel Chiappa, Dino Farinacci, Jesper
   Skriver, Andre Pelletier and Les Ginsberg for their contributions to
   this document.





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10.  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>.

   [RFC5266]  Devarapalli, V. and P. Eronen, "Secure Connectivity and
              Mobility Using Mobile IPv4 and IKEv2 Mobility and
              Multihoming (MOBIKE)", BCP 136, RFC 5266,
              DOI 10.17487/RFC5266, June 2008, <https://www.rfc-
              editor.org/info/rfc5266>.

   [RFC6830]  Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "The
              Locator/ID Separation Protocol (LISP)", RFC 6830,
              DOI 10.17487/RFC6830, January 2013, <https://www.rfc-
              editor.org/info/rfc6830>.

   [RFC6833]  Fuller, V. and D. Farinacci, "Locator/ID Separation
              Protocol (LISP) Map-Server Interface", RFC 6833,
              DOI 10.17487/RFC6833, January 2013, <https://www.rfc-
              editor.org/info/rfc6833>.

Authors' Addresses

   Chris Cassar
   Cisco Systems
   10 New Square Park
   Bedfont Lakes, Feltham  TW14 8HA
   United Kingdom

   Email: ccassar@cisco.com


   Johnson Leong
   Cisco Systems
   Tasman Drive
   San Jose, CA  95134
   USA

   Email: joleong@cisco.com










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   Darrel Lewis
   Cisco Systems
   Tasman Drive
   San Jose, CA  95134
   USA

   Email: darlewis@cisco.com


   Isidor Kouvelas
   Arista Networks Inc.
   5453 Great America Parkway
   Santa Clara, CA  95054
   USA

   Email: isidor@kouvelas.net


   Jesus Arango
   Microsoft

   Email: jearango@microsoft.com





























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