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Versions: 00

RTG Working Group                                               A. Clemm
Internet-Draft                                         P. Pillay-Esnault
Intended status: Standards Track                             U. Chunduri
Expires: January 9, 2020                                       Futurewei
                                                            July 8, 2019


            Preferred Path Routing (PPR) OAM and Accounting
                       draft-cpc-rtgwg-ppr-oam-00

Abstract

   This document defines OAM and traffic accounting capabilities for
   Preferred Path Routing (PPR) for IS-IS and OSPF protocols.
   Specifically, this document specifies OAM capabilities that allow to
   assert proper PPR connectivity and to trace PPR path information.  In
   addition, a set of statistics and operational data to facilitate PPR
   traffic accounting on a per-PPR path basis are defined.  This
   includes a number of Information Elements that extend IPFIX to export
   path information, as well as a YANG Data Model to be used in
   conjunction with management and control protocols.  Collectively the
   capabilities defined in this document provide network operators with
   the necessary means to ensure proper working of their PPR
   deployments.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC2119 [RFC2119],
   RFC8174 [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/.

   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."




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   This Internet-Draft will expire on January 9, 2020.

Copyright Notice

   Copyright (c) 2019 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 Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Key Words . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Definition and Acronyms . . . . . . . . . . . . . . . . . . .   4
   4.  PPR Ping and Trace Functionality  . . . . . . . . . . . . . .   4
     4.1.  PPR Trace Functionality in Strict Mode  . . . . . . . . .   6
     4.2.  PPR Trace Functionality in Loose Mode . . . . . . . . . .   7
   5.  Traffic Accounting through IGP PPR-Attribute Sub-TLVs . . . .   8
   6.  Path Statistics and IP[F/P]IX . . . . . . . . . . . . . . . .   9
   7.  A YANG Data Model for PPR Monitoring  . . . . . . . . . . . .  11
     7.1.  Motivation and Overview . . . . . . . . . . . . . . . . .  11
     7.2.  YANG Data Model . . . . . . . . . . . . . . . . . . . . .  13
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  16
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  16
     9.1.  IGP Path Attributes . . . . . . . . . . . . . . . . . . .  16
     9.2.  IPFIX Information Elements  . . . . . . . . . . . . . . .  16
     9.3.  YANG Data Model . . . . . . . . . . . . . . . . . . . . .  16
   10. Security Considerations . . . . . . . . . . . . . . . . . . .  17
     10.1.  Path Trace and Ping  . . . . . . . . . . . . . . . . . .  17
     10.2.  IGPs and IPFIX . . . . . . . . . . . . . . . . . . . . .  17
     10.3.  YANG Data Model  . . . . . . . . . . . . . . . . . . . .  18
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  18
     11.1.  Normative References . . . . . . . . . . . . . . . . . .  18
     11.2.  Informative References . . . . . . . . . . . . . . . . .  20
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  21








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1.  Introduction

   Preferred Path Routing (PPR) allows to route packets along a custom
   path on the basis of a path identifier (PPR-ID) as opposed to
   individual segments in the packet.  Interior Gateway Protocols (IGPs)
   nodes compute nexthops based on the path description for the prefix
   and take proper forwarding actions for the paths that they are a part
   of.  PPR may be used with different data planes, e.g.  IPv4, IPv6,
   MPLS, SRv6.  Dissemination and nexthop computation of path
   information is described in
   [I-D.chunduri-lsr-isis-preferred-path-routing] and
   [I-D.chunduri-lsr-ospf-preferred-path-routing].

   In order to operate, administer, and maintain PPR deployments,
   network operators must be given tools that allow them to ensure that
   PPR is working as expected and that allow them to troubleshoot any
   potential problems.  This includes assessing whether remote
   destinations can indeed be reached as intended using a given
   preferred path, and to verify path elements along the path being
   taken.  Traditionally, ping (ICMP echo request on IP networks, LSP
   ping in MPLS networks) and traceroute operations are used for those
   purposes.  In order to facilitate operation of PPR, analogous
   capabilities with PPR-specific extensions are useful which are
   defined in this document.

   In addition, for purposes of traffic accounting and ongoing
   operations, it can be very useful to maintain certain PPR statistics.
   This allows, for example, to assess times and volume when traffic
   over preferred paths is occurring.  This document defines new PPR
   path attributes as defined in Section 5 and this can be optionally
   signaled for the preferred paths selectively to account for the
   traffic on every path segment (where critical SLAs are needed).
   IPFIX is commonly used to maintain and export flow-specific
   information from any node in the network.  This document introduces a
   number of new IPFIX Information Elements that are useful in
   conjunction with PPR.

   Some of the same statistics maintained on a per-flow basis may be
   useful to maintain not just for the duration of a flow, but for the
   lifetime of the path.  That information is considered part of regular
   management information and subject to specification as part of a YANG
   data model.

2.  Key Words

   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



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   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

3.  Definition and Acronyms

   o  IE: IPFIX Information Element

   o  IGP: Interior Gateway Protocol

   o  IPFIX: IP Flow Information eXport

   o  IS-IS Link State PDU

   o  PPR: Preferred Path Routing/Route

   o  PPR-ID: Preferred Path Route Identifier, a data plane identifier

   o  SRH: Segment Routing Header - IPv6 routing Extension header

   o  SRv6: Segment Routing with Ipv6 data plane with SRH

   o  TE: Traffic Engineering

4.  PPR Ping and Trace Functionality

   Ping and Trace capabilities depend on the underlying data plane being
   used for the PPR path.  Different mechanisms exist for each of those
   data planes.  As PPR support does not require any change in the
   existing dataplane, for each of those cases, existing ping and trace
   core mechanisms continue to work seamlessly without modification:

      IPv4 data plane: ICMP [RFC792]

      IPv6 data plane: ICMPv6 [RFC4443]

      MPLS data plane: LSP Ping [RFC8287]

      SRv6 data plane: Mechanism under development

   To manage PPR, network operators may require additional information
   that is specific to PPR.  For example, PPR may be installed by
   different IGPs(OSPF/ISIS) and supports two types of paths:

   (1)  Strict: where all the nodes on the path are specified and the
        traffic is forwarded at every single hop to the next node
        defined in the path.





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   (2)  Loose: where not all nodes are described in the path.  There are
        section(s) of the path that are unspecified and the packets are
        forwarded based on the local router forwarding until the next
        node in the path description.

   The current mechanisms need to be enhanced to carry the PPR specific
   mechanism but otherwise it has minimal changes.  In this section, a
   simple topology is shown in Figure 1 is used to illustrate the
   different traces of PPR paths described in the subsequent sub
   sections below.


                       1 __R9___R10__ 1
                        /     1      \
              R1-------R2             R3------R4
                        \_____R11____/
                        2            2

                Figure 1. Topology example

   PPR paths from topology
   PPR-ID: (strict) ->  R1, R2, R3, R11, R4

   PPR-ID: (Loose) ->  R1, R2, R3, R4
   The section between R2-R3 is loose.
   The best path is via R9 and 10. Path is R1, R2, (R9, R10), R3, R4
   Node   Node IPaddr     SPF Cost to R3
   R1      1.1.1.1
   R2      2.2.2.2       costs via R9+R10=3, via R11=4
   R3      3.3.3.3
   R4      4.4.4.4
   R9      9.9.9.9
   R10     10.10.10.10
   R11     11.11.11.11


   The classic ping to a destination relying on the forwarding path
   works seamlessly as the PPR path is installed via IGPs.  The PPR-ID
   is the same as the destination address/label in different dataplanes,
   therefore the existing ping mechanism remains unchanged in a network
   supporting PPR.

   However, the traceroute output should display more PPR specific
   information such as whether or not the path from a node is loose or
   strict, or the source of the protocol that installed a PPR-ID or the
   dataplane information.  In order to support PPR-specific trace
   information, a few additional capabilities are needed.




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   A PPR Trace is initiated from a node, using the PPR-ID as a
   parameter.  The trace will then traverse the PPR path of the
   specified PPR-ID.  In addition to the information that would be
   returned with a regular trace, PPR-specific information is returned
   from PPR nodes that are encountered along the path.  For each PPR
   node, the following information is returned:

   (1)  Node Information: Provides the loopback identifier of the node
        (TBD).

   (2)  Loose-or-strict-or-none: Indicates whether the path from that
        node is loose or strict, or whether the node is PPR-capable but
        not one of the nodes designated in the path.  The latter can be
        the case for transit nodes on a loose segment of the path.

   (3)  PPR-Origin Protocol: Indicates the protocol that installed the
        PPR-ID in the FIB.

   (4)  PPR-ID: Indicates the PPR-ID of the packet as received.  This is
        needed in case of a loose path, leading to encapsulated PPR-ID,
        described further in Section 4.2.

   These PPR specific information will be carried in ICMP data.  These
   extensions are TBD for the various dataplanes.

4.1.  PPR Trace Functionality in Strict Mode

   The PPR strict mode indicates the PPR path on a hop by hop basis.  As
   the PPR-ID represents a strict path to be followed, the ingress node
   should increment the TTL for the PPR-ID until all the egress node has
   returned all individual intermediate segments completely traced.

   The PPR specific enhancements additional information are returned as
   part of trace information.  The strict path to be trace is PPR-
   ID=4.4.4.5 represents the path (R1, R2, R11, R3, R4).  An example of
   the output for traceroute for PPR-IS in IPV4 dataplane is given
   below:














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     >traceroute 4.4.4.5

     traceroute to 4.4.4.5 (192.4.4.5), 30 hops max, 40 byte packets
     1  1.1.1.1 (192.1.1.1)  6.819 ms  1.370 ms  1.281 ms
        PPR: ID:4.4.4.5 Mode=Strict Origin=IS-IS

     2  2.2.2.2 (192.1.1.2)  4.437 ms  1.987 ms  2.335 ms
        PPR: ID:4.4.4.5 Mode=Strict Origin=IS-IS

     3  11.11.11.11 (192.11.11.11)  9.830 ms  11.696 ms  5.478 ms
        PPR: ID:4.4.4.5 Mode=Strict Origin=IS-IS

     4  3.3.3.3 (192.3.3.3)  9.448 ms  5.096 ms  7.518 ms
        PPR: ID:4.4.4.5 Mode=Strict Origin=IS-IS

     5  4.4.4.4 (192.3.3.4)  9.448 ms  5.096 ms  7.518 ms
        PPR: ID:4.4.4.5 Mode=Strict Origin=IS-IS

     Figure 2 Enhanced traceroute Output example


   The output for IPv6 and MPLS traceroute should be augmented to
   display the PPR-ID specific parameters as shown above.

4.2.  PPR Trace Functionality in Loose Mode

   The PPR loose path functionality allows greater flexibility by
   letting the IGP calculate the best path on a loose section of the
   path described for PPR-ID.  The traditional traceroute requires
   additional enhancement for the PPR trace to perform correctly . Per
   Figure 1, the loose path example is R1, R2,(R9, R10), R3, R4 where ()
   represents the loose section of the path.  An example of the output
   for traceroute for PPR-IS in IPV4 dataplane is given below:


















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     >traceroute 4.4.4.5

     traceroute to 4.4.4.5 (192.4.4.5), 30 hops max, 40 byte packets

     1  1.1.1.1 (192.1.1.1)  6.819 ms  1.370 ms  1.281 ms
        PPR: ID:4.4.4.5 Mode=Strict Origin=OSPF

     2  2.2.2.2 (192.1.1.2)  4.437 ms  1.987 ms  2.335 ms
        PPR: ID:4.4.4.5 Mode=Loose Origin=OSPF Multipaths=0

            1 9.9.9.9 (192.9.9.9)  9.830 ms  11.696 ms  5.478 ms
              PPR: ID:4.4.4.5 Mode=None Origin=OSPF

            2 10.10.10.10 (192.9.9.10)  4.230 ms  4.633 ms  5.789 ms
              PPR: ID:4.4.4.5 Mode=None Origin=OSPF

     3  3.3.3.3 (192.3.3.3)  9.448 ms  5.096 ms  7.518 ms
        PPR: ID:4.4.4.5 Mode=Strict Origin =OSPF

     4  4.4.4.4 (192.3.3.4)  9.448 ms  5.096 ms  7.518 ms
        PPR: ID:4.4.4.5 Mode=Strict Origin=OSPF

     Figure 3 Enhanced traceroute Output example


   The output for IPv6 and MPLS traceroute should be augmented to
   display the PPR-ID, Mode and Origin.

   As the loose path functionality does not preclude the presence of
   equal cost multiple paths (ECMPs), the well documented limitations
   and solutions for classic traceroute applies here as well.  For
   operational purposes, it might be of value to list all the
   multipaths.  To acheive this the node just before the loose section
   MAY initiate a recursive traceroute to aggregate that information and
   send it with their ICMP Echo Reply message.

5.  Traffic Accounting through IGP PPR-Attribute Sub-TLVs

   Traffic for certain PPRs may have more stringent requirement w.r.t
   accounting for critical SLAs (e.g. 5G non-eMBB slice) and should
   account for any link/node failures along the path.  Presence of
   "Packet Traffic Accounting" and "Traffic Statistics" Sub-TLVs below
   in IGP PPR-TLV instructs all the respective nodes along the path to
   provision the hardware and to account for the respective traffic
   statistics.  Traffic accounting should happen, when the actual data
   traffic hits for the PPR-ID in the forwarding plane.  This capability
   allows more granular and dynamic enablement of traffic statistics for
   only certain PPRs as needed.



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   As instruction for creating and deleting the traffic accounting for
   PPRs happen through IGP message processing, respective IGP's control
   plane security (Section 10) options are applicable to the PPR-TLV and
   Sub-TLVs thereof.

   PPR-Attribute Sub-TLVs describe the attributes of that particular
   path.  The following path attribute Sub-TLVs are defined for
   respective IGP PPR-TLV [I-D.chunduri-lsr-isis-preferred-path-routing]
   and [I-D.chunduri-lsr-ospf-preferred-path-routing].

   o  Type 10 (Suggested Value - IANA TBD): Packet Traffic accounting
      Sub-TLV.  Length 0 and has no value field.  Specifies to create a
      counter to count number of packets forwarded on this PPR-ID on
      each node in the path description.

   o  Type 11 (Suggested Value - IANA TBD): Traffic statistics in Bytes
      Sub-TLV.  Length 0 and has no value field.  Specifies to create a
      counter to count number of bytes forwarded on this PPR-ID
      specified in the network header (e.g.  IPv4, IPv6) on each node in
      the path description.

   How the accumulated traffic accounting information is distributed to
   a central entity is out of scope of this document.  One can use any
   method (e.g.  RESTCONF, Yang PUSH, gRPC) to extract the PPR-ID
   traffic accounting information from various nodes along the path.

6.  Path Statistics and IP[F/P]IX

   Network providers will appreciate the ability to collect certain
   statistics about PPR path usage, including how much traffic a PPR
   path carries and at what times from any node in the network.  Such
   statistics can be useful to account for the degree of usage of a path
   and provide additional operational insights, including (for example)
   usage patterns and trending information.

   One mechanism that is traditionally used to collect traffic
   statistics is IPFIX (IP Flow Information eXport [RFC7011].  IPFIX
   supports a very rich set of Information Elements containing various
   statistics, far more in fact than will be required for PPR path
   statistics.  However, those statistics are collected only a per-flow
   basis.

   In order to be able to collect statistics on a per-path basis, a set
   of new IPFIX Information Elements need to be defined that allow to
   capture a PPR-ID.  In addition, these new IPFIX Information Elements
   need to be able to serve as a flow key.  This allows separate IPFIX
   cache entries to be created on a per-path basis, and to export the
   corresponding records as IPFIX records.  Of course, the records



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   exported do not refer to flows but to paths - IPFIX thus becomes de-
   facto extended to become IPPIX - IP Path Information eXport.

   Flow records that have a PPR-ID as flow key SHALL be terminated and
   exported in the following events and/or per configurable policy:

   o  When no packet has not been observed on a path for a time interval
      defined by a flow inactivity timer.

   o  When the flow has reached a certain age, defined by a flow
      termination timer.

   A flow record for path is created when a packet on a path is detected
   and no flow entry for that PPR-ID exists.  I.e., flow records are not
   created and maintained for every PPR-ID that is known to the Network
   Element, only to PPR-IDs that are "active".

   The following new IPFIX Information Elements need to be added:

   o  pprid-ipv4, with ipv4address as abstract data type.

   o  pprid-ipv6, with ipv6address as abstract data type.

   o  pprid-mpls, with unsigned32 as abstract data type.

   o  pprid-srv6, which is for further study.

   Each of those fields need to be able to be supported as a flow key
   field.

   The following statistics, as represented through corresponding
   Information Elements, will be of particular interest to export as
   part of IPFIX records with a PPR-ID as flow key:

   o  IE 1: octetDeltaCount - the number of octets on this path

   o  IE 2: packetDeltaCount - the number of incoming packets on this
      path

   o  IE 3: deltaFlowCount - the number of original flows routed via
      this path

   o  IE 21: flowEndSysUpTime - the relative time stamp of the last
      packet of the path flow (i.e. end of the observation period that
      is covered by the record)






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   o  IE 22: flowStartSysUpTime - the relative time stamp of the first
      packet of the path flow (i.e. beginning of the observation period
      that is covered by the record)

   o  IE 132: droppedOctetDeltaCount - the number of octets of the path
      flow that were dropped by the node (during the observation period
      covered by the record).

   o  IE 133: droppedPacketDeltaCount - the number of packets of the
      path flow that were dropped by the node (during the observation
      period covered by the record).

   Because a path's packets traverse every hop on the path, the observed
   path statistics are expected to generally be the same on every node
   across the path.  Network providers may therefore choose to configure
   IPFIX path information export only on certain routers, for example at
   the network edge.  That said, in certain circumstances it may make
   sense to export statistics from multiple nodes on a path and compare
   records for any discrepancies in order to diagnose or isolate
   operational anomalies (such as occurrence of packet loss).

7.  A YANG Data Model for PPR Monitoring

7.1.  Motivation and Overview

   In addition to exporting path flow statistics, network providers need
   to be able to retrieve operational information about PPR paths as a
   whole.  This includes information about when a path was created, how
   it came into being, and statistics maintained over the entire
   lifetime of the path (i.e. since its creation).  For this purpose, a
   YANG Data Model for PPR Monitoring is defined, "ppr-statistics".  The
   model is depicted in the following tree diagram.  The tree diagram
   follows the notation defined in [RFC8340]


















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   module: ietf-ppr-statistics
      +--ro ppr-stats
         +--ro num-pprs?   uint32
         +--ro ppr* [ppr-id]
            +--ro ppr-id                 ppr-id
            +--ro ppr-creation-time?     yang:date-and-time
            +--ro loose-or-strict?       ppr-path-type
            +--ro ppr-origin?            ppr-origin-proto
            +--ro ppr-packets?           uint64
            +--ro ppr-dropped-packets?   uint64
            +--ro ppr-octets?            uint64
            +--ro ppr-active-flows?      uint32

    Figure 1: Tree diagram for establish-subscription-datastore-error-
                                   info

   The data model contains the following:

   o  num-pprs: indicates the number of currently active PPRs on the
      node.

   o  ppr: the list of PPRs configured on the node, indexed by ppr-id,
      with the following entries:

      *  ppr-creation-time: indicates the time the PPR came into being.

      *  loose-or-strict: indicates whether the PPR is loose or strict.

      *  ppr-origin: indicates the way in which the PPR came into being,
         i.e. through which method or protocol it was created.

      *  ppr-packets: the number of packets that have forwarded on that
         path.  (Wrapping around to 0 when the maximum is reached, per
         modulo semantics).

      *  ppr-dropped packets: the number of packets on that path that
         have been dropped by this node.  (Wrapping around to 0 when the
         maximum is reached, per modulo semantics).

      *  ppr-octets: the number of octets that have been forwarded on
         that path.  (Wrapping aound to 0 when the maxium is reached,
         per modulo semantics).

      *  ppr-active-flows: The number of distinct flows that are
         currently active on that path.






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7.2.  YANG Data Model

   <CODE BEGINS> file "ietf-ppr-statistics@2019-07-08.yang"
     module ietf-ppr-statistics {

     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-ppr-statistics";

     prefix pprs;

     import ietf-yang-types {
       prefix yang;
     }

     import ietf-inet-types {
       prefix inet;
     }

     organization "IETF";
     contact
       "WG Web:   <http://tools.ietf.org/wg/rtgwg/>
        WG List:  <mailto:rtgwg@ietf.org>

        Author: Alexander Clemm
                <mailto:ludwig@clemm.org>

        Author: Padma Pillay-Esnault
                <mailto:padma@futurewei.com>

        Author: Uma Chunduri
                <mailto:uchundur@futurewei.com>";

     description
       "The YANG data model defines a set of statistics to be used for
        managing PPR.";

     revision 2019-07-08 {
       description
         "Initial revision";
       reference
         "RFC XXXX: Preferred Path Routing (PPR) OAM and Accounting";
     }

     typedef ppr-id {
       type union {
         type inet:ipv4-address;
         type inet:ipv6-address;
         type string {



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           length "4..32";
         }
       }
       description
         "Identifies a PPR.  Depending on the type of PPR, a different
         format is used.";
     }

     typedef ppr-origin-proto {
       type string;
       description
         "Identifies the source of the PPR, i.e. how the PPR came into
         being.  Different values are TBD and the type itself is
         subject to change.";
     }

     typedef ppr-path-type {
       type enumeration {
         enum loose {
           description "Path type is loose";
         }
         enum strict {
           description "Path type is strict";
         }
       }
       description
         "The type of PPR path - loose or strict.";
     }

     container ppr-stats {
       config false;
       description
         "Top-level container for PPR statistics.";
       leaf num-pprs {
         type uint32;
         description
           "The number of currently active PPRs on the node.";
       }
       list ppr {
         key "ppr-id";
         description
           "The list of currently active PPRs on the node.";
         leaf ppr-id {
           type ppr-id;
           description
             "The identifier of the PPR.";
         }
         leaf ppr-creation-time {



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           type yang:date-and-time;
           description
             "The precise time at which the PPR was created on the
             node.";
         }
         leaf loose-or-strict {
           type ppr-path-type;
           description
             "An indication whether the PPR is loose or strict.";
         }
         leaf ppr-origin {
           type ppr-origin-proto;
           description
             "The way in which the PPR came into being, i.e. through
             which method or protocol it was created.";
         }
         leaf ppr-packets {
           type uint64;
           description
             "The number of packets that have forwarded on that path.
             (Modulo semantics apply, i.e. the value of the leaf wraps
             around to 0 when the maximum uint64 is reached.)";
         }
         leaf ppr-dropped-packets {
           type uint64;
           description
             "The number of packets on that path that have been dropped
             by this node.  (Modulo semantics apply, i.e. the value of
             the leaf wraps around to 0 when the maximum uint64 is
             reached.)";
         }
         leaf ppr-octets {
           type uint64;
           description
             "The number of octets that have been forwarded on that
             path. (Modulo semantics apply, i.e. the value of the
             leaf wraps around to 0 when the maximum uint64 is
             reached.)";
         }
         leaf ppr-active-flows {
           type uint32;
           description
             "The number of distinct flows that are currently active
             on that path.";
         }
       }
     }
   }



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   <CODE ENDS>


8.  Acknowledgements

   tbd

9.  IANA Considerations

9.1.  IGP Path Attributes

   This document requests the following new code points in IANA PPR
   Attributes TLV code-point registry for IS-IS, OSPFv2 and OSPFv3
   protocols.  IS-IS PPR Attributes are defined in
   [I-D.chunduri-lsr-isis-preferred-path-routing] and OSPF PPR
   attributes are defined in
   [I-D.chunduri-lsr-isis-preferred-path-routing].

   Sub-TLV #   Sub-TLV Name
   ---------   ---------------------------------------------------------

    10          Packet Traffic Accounting (Section 5)

    11         Traffic Statistics (Section 5)

          add capability for loose traceroute support.

9.2.  IPFIX Information Elements

   IANA is requested to add the following entries to the IPFIX
   Information Elements Registry:

   o  pprid-ipv4, with ipv4address as abstract data type.

   o  pprid-ipv6, with ipv6address as abstract data type.

   o  pprid-mpls, with unsigned32 as abstract data type.

   o  pprid-srv6, whose abstract data type is for further study.

9.3.  YANG Data Model

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

   URI: urn:ietf:params:xml:ns:yang:ietf-ppr-statistics
   Registrant Contact: The IESG.
   XML: N/A; the requested URI is an XML namespace.



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

   Name: ietf-ppr-statistics
   Namespace: urn:ietf:params:xml:ns:yang:ietf-ppr-statistics
   Prefix: pprs
   Reference: draft-cpc-rtgwg-ppr-oam-XX.txt (RFC form)

10.  Security Considerations

10.1.  Path Trace and Ping

   The ability to perform path traces and pings could be used by an
   attacker to discover details of a network.  In addition, excessive
   amounts of traces and pings could be used by an attacker to try and
   exhaust network resources.  Network providers therefore need to
   secure the ability to invoke trace and ping operations, requiring
   proper auhorization and authentication.  Likewise, trace or ping
   requests originating from an untrusted source from outside the
   network edge should be dropped at the ingress edge.

10.2.  IGPs and IPFIX

   Security concerns for IS-IS are addressed in [RFC5304] and [RFC5310].
   Further security analysis for IS-IS protocol is done in [RFC7645]
   with detailed analysis of various security threats and why [RFC5304]
   should not be used in the deployments.  Advertisement of the
   additional information defined in this document introduces no new
   security concerns in IS-IS protocol.  However as this extension is
   related to SR-MPLS and SRH data planes as defined in [I-D.ietf-
   spring-segment-routing], those particular data plane security
   considerations does apply here.

   Existing security extensions for OSPF protocol are described in
   [RFC2328] and [RFC7684] apply to the extensions specified in this
   document.  While OSPF is under a single administrative domain, there
   can be deployments where potential attackers have access to one or
   more networks in the OSPF routing domain.  In these deployments,
   stronger authentication mechanisms such as those specified in
   [RFC7474] SHOULD be used.

   This document also describes IPFX extensions that allow it to be used
   as a mechanism for IP Path Information Export.  IPFIX security
   considerations apply, which are detailed in [RFC7011] section 11.







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10.3.  YANG Data Model

   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 Network Configuration Access Control Model (NACM) [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.

   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.  The readable data nodes are
   defined under the container "ppr-stats".  The sensitivity/
   vulnerability concerns providing an unauthorized attacker with
   internals about the network, specifically exposure of PPR IDs that
   are installed on a network node and insight about the network traffic
   that occurs over these nodes.

11.  References

11.1.  Normative References

   [I-D.chunduri-lsr-isis-preferred-path-routing]
              Chunduri, U., Li, R., White, R., Tantsura, J., Contreras,
              L., and Y. Qu, "Preferred Path Routing (PPR) in IS-IS",
              draft-chunduri-lsr-isis-preferred-path-routing-03 (work in
              progress), May 2019.

   [I-D.chunduri-lsr-ospf-preferred-path-routing]
              Chunduri, U., Qu, Y., White, R., Tantsura, J., and L.
              Contreras, "Preferred Path Routing (PPR) in OSPF", draft-
              chunduri-lsr-ospf-preferred-path-routing-03 (work in
              progress), May 2019.

   [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>.






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

   [RFC4443]  Conta, A., Deering, S., and M. Gupta, Ed., "Internet
              Control Message Protocol (ICMPv6) for the Internet
              Protocol Version 6 (IPv6) Specification", STD 89,
              RFC 4443, DOI 10.17487/RFC4443, March 2006,
              <https://www.rfc-editor.org/info/rfc4443>.

   [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>.

   [RFC7011]  Claise, B., Ed., Trammell, B., Ed., and P. Aitken,
              "Specification of the IP Flow Information Export (IPFIX)
              Protocol for the Exchange of Flow Information", STD 77,
              RFC 7011, DOI 10.17487/RFC7011, September 2013,
              <https://www.rfc-editor.org/info/rfc7011>.

   [RFC8029]  Kompella, K., Swallow, G., Pignataro, C., Ed., Kumar, N.,
              Aldrin, S., and M. Chen, "Detecting Multiprotocol Label
              Switched (MPLS) Data-Plane Failures", RFC 8029,
              DOI 10.17487/RFC8029, March 2017,
              <https://www.rfc-editor.org/info/rfc8029>.

   [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>.

   [RFC8287]  Kumar, N., Ed., Pignataro, C., Ed., Swallow, G., Akiya,
              N., Kini, S., and M. Chen, "Label Switched Path (LSP)
              Ping/Traceroute for Segment Routing (SR) IGP-Prefix and
              IGP-Adjacency Segment Identifiers (SIDs) with MPLS Data
              Planes", RFC 8287, DOI 10.17487/RFC8287, December 2017,
              <https://www.rfc-editor.org/info/rfc8287>.

   [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>.





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11.2.  Informative References

   [RFC2328]  Moy, J., "OSPF Version 2", STD 54, RFC 2328,
              DOI 10.17487/RFC2328, April 1998,
              <https://www.rfc-editor.org/info/rfc2328>.

   [RFC5304]  Li, T. and R. Atkinson, "IS-IS Cryptographic
              Authentication", RFC 5304, DOI 10.17487/RFC5304, October
              2008, <https://www.rfc-editor.org/info/rfc5304>.

   [RFC5310]  Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R.,
              and M. Fanto, "IS-IS Generic Cryptographic
              Authentication", RFC 5310, DOI 10.17487/RFC5310, February
              2009, <https://www.rfc-editor.org/info/rfc5310>.

   [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>.

   [RFC7474]  Bhatia, M., Hartman, S., Zhang, D., and A. Lindem, Ed.,
              "Security Extension for OSPFv2 When Using Manual Key
              Management", RFC 7474, DOI 10.17487/RFC7474, April 2015,
              <https://www.rfc-editor.org/info/rfc7474>.

   [RFC7645]  Chunduri, U., Tian, A., and W. Lu, "The Keying and
              Authentication for Routing Protocol (KARP) IS-IS Security
              Analysis", RFC 7645, DOI 10.17487/RFC7645, September 2015,
              <https://www.rfc-editor.org/info/rfc7645>.

   [RFC7684]  Psenak, P., Gredler, H., Shakir, R., Henderickx, W.,
              Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute
              Advertisement", RFC 7684, DOI 10.17487/RFC7684, November
              2015, <https://www.rfc-editor.org/info/rfc7684>.

   [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>.

   [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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Authors' Addresses

   Alexander Clemm
   Futurewei
   2330 Central Expressway
   Santa Clara, CA  95050
   USA

   Email: ludwig@clemm.org


   Padma Pillay-Esnault
   Futurewei
   2330 Central Expressway
   Santa Clara, CA  95050
   USA

   Email: padma@futurewei.com


   Uma Chunduri
   Futurewei
   2330 Central Expressway
   Santa Clara, CA  95050
   USA

   Email: umac.ietf@gmail.com
























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