Internet DRAFT - draft-ietf-bfd-unsolicited

draft-ietf-bfd-unsolicited







Network Working Group                                            E. Chen
Internet-Draft                                        Palo Alto Networks
Intended status: Standards Track                                 N. Shen
Expires: 29 October 2023                                          Zededa
                                                               R. Raszuk
                                                                  Arrcus
                                                               R. Rahman
                                                               Graphiant
                                                           27 April 2023


              Unsolicited BFD for Sessionless Applications
                     draft-ietf-bfd-unsolicited-16

Abstract

   For operational simplification of "sessionless" applications using
   Bidirectional Forwarding Detection (BFD), in this document we present
   procedures for "unsolicited BFD" that allow a BFD session to be
   initiated by only one side, and established without explicit per-
   session configuration or registration by the other side (subject to
   certain per-interface or global policies).

   We also introduce a new YANG module to configure and manage
   "unsolicited BFD".  The YANG module in this document is based on YANG
   1.1 as defined in RFC 7950 and conforms to the Network Management
   Datastore Architecture (NMDA) as described in RFC 8342.  This
   document augments RFC 9314.

Requirements Language

   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.

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/.





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   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 29 October 2023.

Copyright Notice

   Copyright (c) 2023 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  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Procedures for Unsolicited BFD  . . . . . . . . . . . . . . .   4
   3.  State Variables . . . . . . . . . . . . . . . . . . . . . . .   5
   4.  YANG Data Model . . . . . . . . . . . . . . . . . . . . . . .   5
     4.1.  Unsolicited BFD Hierarchy . . . . . . . . . . . . . . . .   5
     4.2.  Unsolicited BFD Module  . . . . . . . . . . . . . . . . .   6
     4.3.  Data Model Example  . . . . . . . . . . . . . . . . . . .  11
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  13
   6.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  13
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  13
     7.1.  BFD Protocol Security Considerations  . . . . . . . . . .  13
     7.2.  BFD Protocol Authentication Considerations  . . . . . . .  14
     7.3.  YANG Module Security Considerations . . . . . . . . . . .  14
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  15
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  15
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  17
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  17











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1.  Introduction

   The current implementation and deployment practice for BFD ([RFC5880]
   and [RFC5881]) usually requires BFD sessions be explicitly configured
   or registered on both sides.  This requirement is not an issue when
   an application like BGP [RFC4271] has the concept of a "session" that
   involves both sides for its establishment.  However, this requirement
   can be operationally challenging when the prerequisite "session" does
   not naturally exist between two endpoints in an application.
   Simultaneous configuration and coordination may be required on both
   sides for BFD to take effect.  For example:

   *  When BFD is used to keep track of the "liveness" of the nexthop of
      static routes.  Although only one side may need the BFD
      functionality, currently both sides need to be involved in
      specific configuration and coordination and in some cases static
      routes are created unnecessarily just for BFD.
   *  When BFD is used to keep track of the "liveness" of the third-pary
      nexthop of BGP routes received from the Route Server [RFC7947] at
      an Internet Exchange Point (IXP).  As the third-party nexthop is
      different from the peering address of the Route Server, for BFD to
      work, currently two routers peering with the Route Server need to
      have routes and nexthops from each other (although indirectly via
      the Route Server).

   Clearly it is beneficial and desirable to reduce or eliminate
   unnecessary configurations and coordination in these "sessionless"
   applications using BFD.

   In this document we present procedures for "unsolicited BFD" that
   allow a BFD session to be initiated by only one side, and established
   without explicit per-session configuration or registration by the
   other side (subject to certain per-interface or global policies).

   Unsolicited BFD impacts only the initiation of BFD sessions.  There
   is no change to all the other procedures specified in [RFC5880] such
   as, but not limited to, the Echo function and Demand mode.

   With "unsolicited BFD" there is potential risk for excessive resource
   usage by BFD from "unexpected" remote systems.  To mitigate such
   risks, several mechanisms are recommended in the Security
   Considerations section.

   The procedure described in this document could be applied to BFD for
   Multihop paths [RFC5883].  However, because of security risks, this
   document applies only to BFD for single IP hops [RFC5881].





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   Compared to the "Seamless BFD" [RFC7880], this proposal involves only
   minor procedural enhancements to the widely deployed BFD itself.
   Thus, we believe that this proposal is inherently simpler in the
   protocol itself and deployment.  As an example, it does not require
   the exchange of BFD discriminators over an out-of-band channel before
   BFD session bring-up.

   When BGP Add-Path [RFC7911] is deployed at an IXP using a Route
   Server, multiple BGP paths (when they exist) can be made available to
   the clients of the Route Server as described in [RFC7947].
   Unsolicited BFD can be used by BGP route selection's Route
   Resolvability Condition Section 9.1.2.1 of [RFC4271] to exclude
   routes where the NEXT_HOP is not reachable using the procedures
   specified in this document.

2.  Procedures for Unsolicited BFD

   With "unsolicited BFD", one side takes the "Active role" and the
   other side takes only the "Passive role" as described in [RFC5880],
   section 6.1.

   Passive unsolicited BFD support MUST be disabled by default, and MUST
   require explicit configuration to be enabled.  On the passive side,
   the following BFD parameters, from [RFC5880] section 6.8.1 SHOULD be
   configurable:

   *  bfd.DesiredMinTxInterval
   *  bfd.RequiredMinRxInterval
   *  bfd.DetectMult

   The passive side MAY also choose to use the values of the parameters
   above that the active side uses in its BFD Control packets.  However,
   the bfd.LocalDiscr value MUST be selected by the passive side to
   allow multiple unsolicited BFD sessions.

   The active side starts sending the BFD Control packets as specified
   in [RFC5880].  The passive side does not send BFD Control packets
   initially, it sends BFD Control packets only after it has received
   BFD Control packets from the active side.

   When the passive side receives a BFD Control packet from the active
   side with 0 as "Your Discriminator" and does not find an existing BFD
   session, the passive side SHOULD create a matching BFD session toward
   the active side, unless not permitted by local configuration or
   policy.






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   When the passive side receives an incoming BFD Control packet on a
   numbered interface, the source address of that packet MUST belong to
   the subnet of the interface on which the BFD packet is received, else
   the BFD control packet MUST NOT be processed.

   The passive side MUST then start sending BFD Control packets and
   perform the necessary procedure for bringing up, maintaining and
   tearing down the BFD session.  If the BFD session fails to get
   established within a certain amount of time (which is implementation
   specific but has to be at least equal to the local failure detection
   time), or if an established BFD session goes down, the passive side
   MUST stop sending BFD Control packets and SHOULD delete the BFD
   session created until BFD Control packets are initiated by the active
   side again.

   When an Unsolicited BFD session goes down, an implementation may
   retain the session state for a period of time.  Retaining this state
   can be useful for operational purposes.

3.  State Variables

   This document defines a new state variable called Role.

   bfd.Role

   The role of the local system during BFD session initialization, as
   per [RFC5880], section 6.1.  Possible values are Active or Passive.

4.  YANG Data Model

   This section extends the YANG data model for BFD [RFC9314] to cover
   unsolicited BFD.  The new module imports [RFC8349] since the "bfd"
   container in [RFC9314] is under "control-plane-protocol".  The YANG
   module in this document conforms to the Network Management Datastore
   Architecture (NMDA) [RFC8342].

4.1.  Unsolicited BFD Hierarchy

   Configuration for unsolicited BFD parameters for IP single-hop
   sessions can be done at 2 levels:

   *  Globally, i.e. for all interfaces.
   *  For specific interfaces.  This requires support for the
      "unsolicited-params-per-interface" feature.

   If configuration exists at both levels, per-interface configuration
   takes precedence over global configuration.




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   For operational data, a new "role" leaf node has been added for BFD
   IP single-hop sessions.

   The tree diagram below uses the graphical representation of data
   models, as defined in [RFC8340].


module: ietf-bfd-unsolicited

  augment /rt:routing/rt:control-plane-protocols
          /rt:control-plane-protocol/bfd:bfd/bfd-ip-sh:ip-sh:
    +--rw unsolicited?
       +--rw local-multiplier?                 multiplier
       +--rw (interval-config-type)?
          +--:(tx-rx-intervals)
          |  +--rw desired-min-tx-interval?    uint32
          |  +--rw required-min-rx-interval?   uint32
          +--:(single-interval) {single-minimum-interval}?
             +--rw min-interval?               uint32
  augment /rt:routing/rt:control-plane-protocols
          /rt:control-plane-protocol/bfd:bfd/bfd-ip-sh:ip-sh
          /bfd-ip-sh:interfaces:
    +--rw unsolicited
       +--rw enabled?                          boolean
       +--rw local-multiplier?                 bfd-types:multiplier {bfd-unsol:unsolicited-params-per-interface}?
       +--rw (interval-config-type)? {bfd-unsol:unsolicited-params-per-interface}?
          +--:(tx-rx-intervals)
          |  +--rw desired-min-tx-interval?    uint32
          |  +--rw required-min-rx-interval?   uint32
          +--:(single-interval) {bfd-types:single-minimum-interval}?
             +--rw min-interval?               uint32
  augment /rt:routing/rt:control-plane-protocols
          /rt:control-plane-protocol/bfd:bfd/bfd-ip-sh:ip-sh
          /bfd-ip-sh:sessions/bfd-ip-sh:session:
    +--ro role?   bfd-unsol:role


4.2.  Unsolicited BFD Module


   <CODE BEGINS> file "ietf-bfd-unsolicited@2023-04-22.yang"
   module ietf-bfd-unsolicited {

     yang-version 1.1;

     namespace "urn:ietf:params:xml:ns:yang:ietf-bfd-unsolicited";

     prefix "bfd-unsol";



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     // RFC Ed.: replace occurences of YYYY with actual RFC numbers
     // and remove this note

     import ietf-bfd-types {
       prefix "bfd-types";
       reference
         "RFC 9314: YANG Data Model for Bidirectional Forwarding
          Detection (BFD)";
     }

     import ietf-bfd {
       prefix "bfd";
       reference
         "RFC 9314: YANG Data Model for Bidirectional Forwarding
          Detection (BFD)";
     }

     import ietf-bfd-ip-sh {
       prefix "bfd-ip-sh";
       reference
         "RFC 9314: YANG Data Model for Bidirectional Forwarding
          Detection (BFD)";
     }

     import ietf-routing {
       prefix "rt";
       reference
         "RFC 8349: A YANG Data Model for Routing Management
          (NMDA version)";
     }

     organization "IETF BFD Working Group";

     contact
       "WG Web:   <https://datatracker.ietf.org/wg/bfd/>
        WG List:  <rtg-bfd@ietf.org>

        Editors:  Enke Chen (enchen@paloaltonetworks.com),
                  Naiming Shen (naiming@zededa.com),
                  Robert Raszuk (robert@raszuk.net),
                  Reshad Rahman (reshad@yahoo.com)";

     description
       "This module contains the YANG definition for BFD unsolicited
        as per RFC YYYY.

        Copyright (c) 2023 IETF Trust and the persons
        identified as authors of the code.  All rights reserved.



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        Redistribution and use in source and binary forms, with or
        without modification, is permitted pursuant to, and subject
        to the license terms contained in, the Revised BSD License
        set forth in Section 4.c of the IETF Trust's Legal Provisions
        Relating to IETF Documents
        (http://trustee.ietf.org/license-info).

        This version of this YANG module is part of RFC YYYY; see
        the RFC itself for full legal notices.";

     reference "RFC YYYY";

     revision 2023-04-22 {
       description
         "Initial revision.";
       reference
         "RFC YYYY: Unsolicited BFD for Sessionless Applications.";
     }

     /*
      * Feature definitions
      */
     feature unsolicited-params-per-interface {
       description
         "This feature indicates that the server supports per-interface
          parameters for unsolicited sessions.";
       reference
         "RFC YYYY: Unsolicited BFD for Sessionless Applications.";
     }

     /*
      * Type Definitions
      */
     identity role {
       description
         "Base identity from which all roles are derived.
          Role of local system during BFD session initialization.";
     }
     identity active {
       base "bfd-unsol:role";
       description "Active role";
       reference
         "RFC5880: Bidirectional Forwarding Detection (BFD),
          Section 6.1";
     }
     identity passive {
       base "bfd-unsol:role";
       description "Passive role";



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       reference
         "RFC5880: Bidirectional Forwarding Detection (BFD),
          Section 6.1";
     }

     /*
      * Augments
      */
      augment "/rt:routing/rt:control-plane-protocols/"
            + "rt:control-plane-protocol/bfd:bfd/bfd-ip-sh:ip-sh" {
        description
          "Augmentation for BFD unsolicited parameters";
        container unsolicited {
          description
            "BFD IP single-hop unsolicited top level container";
          uses bfd-types:base-cfg-parms;
        }
      }

      augment "/rt:routing/rt:control-plane-protocols/"
            + "rt:control-plane-protocol/bfd:bfd/bfd-ip-sh:ip-sh/"
            + "bfd-ip-sh:interfaces" {
        description
          "Augmentation for BFD unsolicited on IP single-hop interface";
        container unsolicited {
          description
            "BFD IP single-hop interface unsolicited top level
             container";
          leaf enabled {
            type boolean;
            default false;
            description
              "BFD unsolicited enabled on this interface.";
          }
          /*
           * The following is the same as bfd-types:base-cfg-parms, but
           * without default values (for inheritance)
           */
          leaf local-multiplier {
            if-feature bfd-unsol:unsolicited-params-per-interface;
            type bfd-types:multiplier;
            description
              "Multiplier transmitted by the local system. Defaults to
               ../../unsolicited/local-multiplier.
               A multiplier configured under an interface takes precedence
               over the mulitiplier configured at the global level.";
          }




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          choice interval-config-type {
            if-feature bfd-unsol:unsolicited-params-per-interface;
            description
              "Two interval values or one value used for both transmit and
               receive. Defaults to ../../unsolicited/interval-config-type.
               An interval configured under an interface takes precedence
               over any interval configured at the global level.";
            case tx-rx-intervals {
              leaf desired-min-tx-interval {
                type uint32;
                units "microseconds";
                description
                  "Desired minimum transmit interval of control packets.";
              }
              leaf required-min-rx-interval {
                type uint32;
                units "microseconds";
                description
                  "Required minimum receive interval of control packets.";
              }
            }
            case single-interval {
              if-feature "bfd-types:single-minimum-interval";
              leaf min-interval {
                type uint32;
                units "microseconds";
                description
                  "Desired minimum transmit interval and required
                   minimum receive interval of control packets.";
              }
            }
          }
        }
      }

     augment "/rt:routing/rt:control-plane-protocols/"
           + "rt:control-plane-protocol/bfd:bfd/bfd-ip-sh:ip-sh/"
           + "bfd-ip-sh:sessions/bfd-ip-sh:session" {
       description
         "Augmentation for BFD unsolicited on IP single-hop session";
         leaf role {
           type identityref {
             base "bfd-unsol:role";
           }
           config false;
           description "Role.";
         }
     }



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   }
   <CODE ENDS>

4.3.  Data Model Example

   This section shows an example on how to configure the passive end of
   unsolicited BFD:

   *  We have global BFD IP single-hop unsolicited configuration with a
      local-multiplier of 2 and min-interval at 50ms
   *  BFD IP single-hop unsolicited is enabled on interface eth0, with a
      local-multiplier of 3 and min-interval at 250 ms
   *  BFD IP single-hop unsolicited is enabled on interface eth1.  Since
      there is no parameter configuration for eth1, it inherits from the
      global configuration.




































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<?xml version="1.0" encoding="UTF-8"?>
<config xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<interfaces xmlns="urn:ietf:params:xml:ns:yang:ietf-interfaces">
  <interface>
    <name>eth0</name>
    <type
        xmlns:ianaift="urn:ietf:params:xml:ns:yang:iana-if-type">ianaift:ethernetCsmacd</type>
  </interface>
  <interface>
    <name>eth1</name>
    <type
        xmlns:ianaift="urn:ietf:params:xml:ns:yang:iana-if-type">ianaift:ethernetCsmacd</type>
  </interface>
</interfaces>
<routing xmlns="urn:ietf:params:xml:ns:yang:ietf-routing">
  <control-plane-protocols>
    <control-plane-protocol>
      <type
          xmlns:bfd-types="urn:ietf:params:xml:ns:yang:ietf-bfd-types">bfd-types:bfdv1</type>
      <name>name:BFD</name>
      <bfd xmlns="urn:ietf:params:xml:ns:yang:ietf-bfd">
        <ip-sh xmlns="urn:ietf:params:xml:ns:yang:ietf-bfd-ip-sh">
          <unsolicited>
            <local-multiplier>2</local-multiplier>
            <min-interval>50000</min-interval>
          </unsolicited>
          <interfaces>
              <interface>eth0</interface>
              <unsolicited>
                <enabled>true</enabled>
                <local-multiplier>3</local-multiplier>
                <min-interval>250000</min-interval>
              </unsolicited>
          </interfaces>
          <interfaces>
              <interface>eth1</interface>
              <unsolicited>
                <enabled>true</enabled>
              </unsolicited>
          </interfaces>
        </ip-sh>
      </bfd>
    </control-plane-protocol>
  </control-plane-protocols>
</routing>
</config>





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5.  IANA Considerations

   This document registers the following namespace URI in the "IETF XML
   Registry" [RFC3688]:

   URI: urn:ietf:params:xml:ns:yang:ietf-bfd-unsolicited

   Registrant Contact: The IESG.

   XML: N/A; the requested URI is an XML namespace.

   This document registers the following YANG module in the "YANG Module
   Names" registry [RFC6020]:

   Name: ietf-bfd-unsolicited

   Namespace: urn:ietf:params:xml:ns:yang:ietf-bfd-unsolicited

   Prefix: bfd-unsol

   Reference: RFC YYYY

6.  Acknowledgments

   Authors would like to thank Acee Lindem, Alvaro Retana, Dan
   Romascanu, Derek Atkins, Greg Mirsky, Gyan Mishra, Henning Rogge,
   Jeffrey Haas, John Scudder, Lars Eggert, Magnus Westerlund, Mahesh
   Jethanandani, Murray Kucherawy, Raj Chetan, Robert Wilton, Roman
   Danyliw, Tom Petch, and Zaheduzzaman Sarker for their review and
   valuable input.

7.  Security Considerations

7.1.  BFD Protocol Security Considerations

   The same security considerations and protection measures as those
   described in [RFC5880] and [RFC5881] apply to this document.  In
   addition, with "unsolicited BFD" there is potential risk for
   excessive resource usage by BFD from "unexpected" remote systems.  To
   mitigate such risks, implementations of unsolicited BFD MUST:

   *  Limit the feature to specific interfaces, and to single-hop BFD
      sessions using the procedures from [RFC5082].  See Section 5 of
      [RFC5881] for the details of these procedures.
   *  Apply policy to process BFD packets only from certain subnets or
      hosts.





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   *  Deploy the feature only in an environment that does not offer
      anonymous participation.  Examples include an IXP, where the IXP
      operator will have a business relationship with all IXP
      participants, or between a provider and its customers.

7.2.  BFD Protocol Authentication Considerations

   Implementations of unsolicited BFD are RECOMMENDED to use BFD
   authentication; see [RFC5880].  If BFD authentication is used, the
   strongest BFD authentication mechanism that is supported MUST be
   used.

   In some environments, such as an Internet Exchange Points (IXPs), BFD
   authentication cannot be used because of the lack of coordination for
   the operation of the two endpoints of the BFD session.

   In other environments, such as when BFD is used to track the next hop
   of static routes, it is possible to use BFD authentication.  This
   comes with the extra cost of configuring matching keychains between
   the two endpoints.

7.3.  YANG Module Security Considerations

   The YANG module specified in this document defines a schema for data
   that is designed to be accessed via network management protocols such
   as NETCONF [RFC6241] or RESTCONF [RFC8040].  The lowest NETCONF layer
   is the secure transport layer, and the mandatory-to-implement secure
   transport is Secure Shell (SSH) [RFC6242].  The lowest RESTCONF layer
   is HTTPS, and the mandatory-to-implement secure transport is TLS
   [RFC8446].

   The NETCONF access control model [RFC8341] provides the means to
   restrict access for particular NETCONF or RESTCONF users to a
   preconfigured subset of all available NETCONF or RESTCONF protocol
   operations and content.

   There are a number of data nodes defined in this YANG module that are
   writable/creatable/deletable (i.e., config true, which is the
   default).  These data nodes may be considered sensitive or vulnerable
   in some network environments.  Write operations (e.g., edit-config)
   to these data nodes without proper protection can have a negative
   effect on network operations.  These are the subtrees and data nodes
   and their sensitivity/vulnerability:

   /routing/control-plane-protocols/control-plane-protocol/bfd/ip-sh
   /unsolicited:





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   *  data node "enabled" enables creation of unsolicited BFD IP single-
      hop sessions globally, i.e. on all interfaces.  See Section 7.1.
   *  data nodes local-multiplier, desired-min-tx-interval, required-
      min-rx-interval and min-interval all impact the parameters of the
      unsolicited BFD IP single-hop sessions.  Write operations to these
      nodes change the rates of BFD packet generation and detection time
      of the failures of a BFD session.

   /routing/control-plane-protocols/control-plane-protocol/bfd/ip-sh
   /interfaces/interface/unsolicited:

   *  data node "enabled" enables creation of unsolicited BFD IP single-
      hop sessions on a specific interface.  See Section 7.1.
   *  data nodes local-multiplier, desired-min-tx-interval, required-
      min-rx-interval and min-interval all impact the parameters of the
      unsolicited BFD IP single-hop sessions on the interface.

   Some of the readable data nodes in this YANG module may be considered
   sensitive or vulnerable in some network environments.  It is thus
   important to control read access (e.g., via get, get-config, or
   notification) to these data nodes.  These are the subtrees and data
   nodes and their sensitivity/vulnerability:

   /routing/control-plane-protocols/control-plane-protocol/bfd/ip-sh
   /sessions/session/role: access to this information discloses the role
   of the local system in the creation of the unsolicited BFD session.

8.  References

8.1.  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>.

   [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
              DOI 10.17487/RFC3688, January 2004,
              <https://www.rfc-editor.org/info/rfc3688>.

   [RFC5082]  Gill, V., Heasley, J., Meyer, D., Savola, P., Ed., and C.
              Pignataro, "The Generalized TTL Security Mechanism
              (GTSM)", RFC 5082, DOI 10.17487/RFC5082, October 2007,
              <https://www.rfc-editor.org/info/rfc5082>.

   [RFC5880]  Katz, D. and D. Ward, "Bidirectional Forwarding Detection
              (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010,
              <https://www.rfc-editor.org/info/rfc5880>.



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   [RFC5881]  Katz, D. and D. Ward, "Bidirectional Forwarding Detection
              (BFD) for IPv4 and IPv6 (Single Hop)", RFC 5881,
              DOI 10.17487/RFC5881, June 2010,
              <https://www.rfc-editor.org/info/rfc5881>.

   [RFC6020]  Bjorklund, M., Ed., "YANG - A Data Modeling Language for
              the Network Configuration Protocol (NETCONF)", RFC 6020,
              DOI 10.17487/RFC6020, October 2010,
              <https://www.rfc-editor.org/info/rfc6020>.

   [RFC6241]  Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
              and A. Bierman, Ed., "Network Configuration Protocol
              (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
              <https://www.rfc-editor.org/info/rfc6241>.

   [RFC6242]  Wasserman, M., "Using the NETCONF Protocol over Secure
              Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011,
              <https://www.rfc-editor.org/info/rfc6242>.

   [RFC8040]  Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
              Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
              <https://www.rfc-editor.org/info/rfc8040>.

   [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>.

   [RFC8340]  Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
              BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
              <https://www.rfc-editor.org/info/rfc8340>.

   [RFC8341]  Bierman, A. and M. Bjorklund, "Network Configuration
              Access Control Model", STD 91, RFC 8341,
              DOI 10.17487/RFC8341, March 2018,
              <https://www.rfc-editor.org/info/rfc8341>.

   [RFC8349]  Lhotka, L., Lindem, A., and Y. Qu, "A YANG Data Model for
              Routing Management (NMDA Version)", RFC 8349,
              DOI 10.17487/RFC8349, March 2018,
              <https://www.rfc-editor.org/info/rfc8349>.

   [RFC8446]  Rescorla, E., "The Transport Layer Security (TLS) Protocol
              Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
              <https://www.rfc-editor.org/info/rfc8446>.







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   [RFC9314]  Jethanandani, M., Ed., Rahman, R., Ed., Zheng, L., Ed.,
              Pallagatti, S., and G. Mirsky, "YANG Data Model for
              Bidirectional Forwarding Detection (BFD)", RFC 9314,
              DOI 10.17487/RFC9314, September 2022,
              <https://www.rfc-editor.org/info/rfc9314>.

8.2.  Informative References

   [RFC4271]  Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
              Border Gateway Protocol 4 (BGP-4)", RFC 4271,
              DOI 10.17487/RFC4271, January 2006,
              <https://www.rfc-editor.org/info/rfc4271>.

   [RFC5883]  Katz, D. and D. Ward, "Bidirectional Forwarding Detection
              (BFD) for Multihop Paths", RFC 5883, DOI 10.17487/RFC5883,
              June 2010, <https://www.rfc-editor.org/info/rfc5883>.

   [RFC7880]  Pignataro, C., Ward, D., Akiya, N., Bhatia, M., and S.
              Pallagatti, "Seamless Bidirectional Forwarding Detection
              (S-BFD)", RFC 7880, DOI 10.17487/RFC7880, July 2016,
              <https://www.rfc-editor.org/info/rfc7880>.

   [RFC7911]  Walton, D., Retana, A., Chen, E., and J. Scudder,
              "Advertisement of Multiple Paths in BGP", RFC 7911,
              DOI 10.17487/RFC7911, July 2016,
              <https://www.rfc-editor.org/info/rfc7911>.

   [RFC7947]  Jasinska, E., Hilliard, N., Raszuk, R., and N. Bakker,
              "Internet Exchange BGP Route Server", RFC 7947,
              DOI 10.17487/RFC7947, September 2016,
              <https://www.rfc-editor.org/info/rfc7947>.

   [RFC8342]  Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
              and R. Wilton, "Network Management Datastore Architecture
              (NMDA)", RFC 8342, DOI 10.17487/RFC8342, March 2018,
              <https://www.rfc-editor.org/info/rfc8342>.

Authors' Addresses

   Enke Chen
   Palo Alto Networks
   Email: enchen@paloaltonetworks.com


   Naiming Shen
   Zededa
   Email: naiming@zededa.com




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   Robert Raszuk
   Arrcus
   2077 Gateway Place
   San Jose, CA 95110
   United States of America
   Email: robert@raszuk.net


   Reshad Rahman
   Graphiant
   Canada
   Email: reshad@yahoo.com







































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