[Docs] [txt|pdf] [Tracker] [Email] [Diff1] [Diff2] [Nits]

Versions: 00 01

LSR Working Group                                            U. Chunduri
Internet-Draft                                                     Y. Qu
Intended status: Standards Track                              Huawei USA
Expires: January 3, 2019                                        R. White
                                                                LinkedIn
                                                             J. Tantsura
                                                          Nuage Networks
                                                            L. Contreras
                                                              Telefonica
                                                            July 2, 2018


                  Preferred Path Routing (PPR) in OSPF
           draft-chunduri-lsr-ospf-preferred-path-routing-01

Abstract

   This document specifies a Preferred Path Routing (PPR) mechanism to
   simplify the path description of data plane traffic in Segment
   Routing (SR) deployments with OSPFv2 and OSPFv3 protocols.  PPR aims
   to mitigate the MTU and data plane processing issues that may result
   from SR packet overheads; and also supports traffic measurement,
   accounting statistics and further attribute extensions along the
   paths.  Preferred Path Routing is achieved through the addition of
   descriptions to OSPF advertised prefixes, and mapping those to a PPR
   data-plane identifier.

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




Chunduri, et al.         Expires January 3, 2019                [Page 1]


Internet-Draft    Preferred Path Routing (PPR) in OSPF         July 2018


   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 January 3, 2019.

Copyright Notice

   Copyright (c) 2018 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
     1.1.  Acronyms  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  OSPFv2 PPR TLV  . . . . . . . . . . . . . . . . . . . . . . .   4
     2.1.  PPR-Flags . . . . . . . . . . . . . . . . . . . . . . . .   6
     2.2.  PPR-Prefix Sub-TLV  . . . . . . . . . . . . . . . . . . .   6
     2.3.  PPR-ID Sub-TLV  . . . . . . . . . . . . . . . . . . . . .   7
     2.4.  PPR-PDE Sub-TLV . . . . . . . . . . . . . . . . . . . . .   9
     2.5.  PPR-Attributes Sub-TLV  . . . . . . . . . . . . . . . . .  10
   3.  OSPFv3 PPR TLV  . . . . . . . . . . . . . . . . . . . . . . .  11
     3.1.  OSPFv3 PPR-Prefix Sub-TLV . . . . . . . . . . . . . . . .  13
     3.2.  OSPFv3 PPR-ID Sub-TLVs  . . . . . . . . . . . . . . . . .  13
     3.3.  OSPFv3 PPR-PDE Sub-TLV  . . . . . . . . . . . . . . . . .  15
     3.4.  OSPFv3 PPR-Attributes Sub-TLV . . . . . . . . . . . . . .  17
   4.  Other Considerations  . . . . . . . . . . . . . . . . . . . .  18
   5.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  18
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  18
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  19
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  19
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  19
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  19
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  21








Chunduri, et al.         Expires January 3, 2019                [Page 2]


Internet-Draft    Preferred Path Routing (PPR) in OSPF         July 2018


1.  Introduction

   In a network implementing Segment Routing (SR), packets are steered
   through the network using Segment Identifiers (SIDs) carried in the
   packet header.  Each SID uniquely identifies a segment as defined in
   [I-D.ietf-spring-segment-routing].  SR capabilities are defined for
   MPLS and IPv6 data planes called SR-MPLS and SRv6 respectively.

   In SR-MPLS, a segment is encoded as a label and an ordered list of
   segments is encoded as a stack of labels on the data packet.  In
   SRv6, a segment is encoded as an IPv6 address, with in a new type of
   IPv6 hop-by-hop routing header/extension header (EH) called SRH
   [I-D.ietf-6man-segment-routing-header], where an ordered list of IPv6
   addresses/segments is encoded in SRH.

   The issues caused by the large SID depth, and existing methods for
   mitigation are introduced in
   [I-D.chunduri-lsr-isis-preferred-path-routing] section 1.2 and 1.3.
   To mitigate these issues , and also to facilitate forwarding plane a
   mechanism to identify the path with a corresponding data plane
   identifier for accounting of traffic for SR paths, this draft
   proposes a new OSPFv2 PPR TLV (Section 2), OSPFv3 PPR TLV (Section 3)
   to use the path with a corresponding data plane identifier.

   Preferred Path Routing means enabling route computation based on the
   specific path described along with the prefix as opposed to shortest
   path towards the prefix.  This also further described in Section 2 of
   [I-D.chunduri-lsr-isis-preferred-path-routing].

   Any prefix advertised with a path description from any node in the
   network is called Preferred Path Route.  A PPR could be an SR path,
   an explicitly provisioned Fast Re-Route (FRR) path or a service
   chained path.  A PPR can be signaled by any node, which receives the
   SR path computed by a central controller, or by operator by
   statically configuring the same on a node in the network.

   With corresponding data plane, Section 4 mechanism as in [I-
   D.chunduri-isis-preferred-path-routing], reduces the SID stack in the
   data plane with a single PPR ID.

1.1.  Acronyms

   EL       -  Entropy Label

   ELI      -  Entropy Label Indicator

   MPLS     -  Multi Protocol Label Switching




Chunduri, et al.         Expires January 3, 2019                [Page 3]


Internet-Draft    Preferred Path Routing (PPR) in OSPF         July 2018


   MSD      -  Maximum SID Depth

   MTU      -  Maximum Transferrable Unit

   NSP      -  Non Shortest Path

   SID      -  Segment Identifier

   SPF      -  Shortest Path First

   SR       -  Segment Routing

   SRH      -  Segment Routing Header

   SR-MPLS  -  Segment Routing with MPLS data plane

   SRv6     -  Segment Routing with Ipv6 data plane with SRH

   SRH      -  IPv6 Segment Routing Header

   TE       -  Traffic Engineering

2.  OSPFv2 PPR TLV

   Extended Prefix Opaque LSAs defined in [RFC7684] are used for
   advertisements of PPRs.  This section describes the encoding of PPR
   TLV.  This TLV can be seen as having 4 logical section viz., encoding
   of the OSPFv2 Prefix, encoding of PPR-ID, encoding of path
   description with an ordered PDE Sub-TLVs and a set of optional PPR
   attribute Sub-TLVs, which can be used to describe one or more
   parameters of the path.  Multiple OSPF PPR TLVs MAY be advertised in
   each OSPF Extended Prefix Opaque LSA, but all TLVs included in a
   single OSPF Extended Prefix Opaque LSA MUST have the same flooding
   scope.

   The PPR TLV has Type TBD (suggested value xxx), and has the following
   format:














Chunduri, et al.         Expires January 3, 2019                [Page 4]


Internet-Draft    Preferred Path Routing (PPR) in OSPF         July 2018


        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             |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |        PPR-Flags              |     AF       | Reserved       |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |             PPR-Prefix Sub-TLV (variable size)                |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |              PPR-ID   Sub-TLV (variable size)                 |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                  PPR-PDE Sub-TLVs (variable)                  |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                PPR-Attribute Sub-TLVs(variable)               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                      Figure 1: OSPFV2 PPR TLV Format

   o  Type - TBD (IANA)from OSPF Extended Prefix Opaque LSA registry.

   o  Length - Total length of the value field in bytes (variable).

   o  PPR-Flags - 2 Octet flags for this TLV are described below.

   o  AF - Address family for the prefix.  Currently, the only supported
      value is 0 for IPv4 unicast.  The inclusion of address family in
      this TLV allows for future extension.

   o  Reserved - 1 Octet reserved bits for future use.  Reserved bits
      MUST be reset on transmission and ignored on receive.

   o  PPR-Prefix - This is a variable size Sub-TLV, which represents the
      prefix for which path description is being attached to.  This is
      defined in Section 2.2.

   o  PPR-ID - This is a variable size Sub-TLV, which represents the
      data plane or forwarding identifier of the PPR.  This is defined
      in Section 2.3.

   o  PPR-PDEs - Variable number of ordered PDE Sub-TLVs which
      represents the path.  This is defined in Section 2.4.

   o  PPR-Attributes - Variable number of PPR-Attribute Sub-TLVs which
      represent the path attributes.  These are defined in Section 2.5.







Chunduri, et al.         Expires January 3, 2019                [Page 5]


Internet-Draft    Preferred Path Routing (PPR) in OSPF         July 2018


2.1.  PPR-Flags

   Flags: 2 octet field of PPR TLV has following flags defined:

        NSPF ID Flags Format
           0  1  2  3  4  5  6  7                      15
           +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
           |IA|A |   Reserved                              |
           +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+

   w=Where:

      IA-Flag: Inter-Area flag.  If set, advertisement is of inter-area
      type.  An Area Boarder Router (ABR) that is advertising the OSPF
      PPR TLV between areas MUST set this bit.

      A: The originator of the PPR TLV MUST set the A bit in order to
      signal that the prefixes and PPR-IDs advertised in the PPR TLV are
      directly connected to the originators.  If this bit is not set,
      this allows any other node in the network advertise this TLV on
      behalf of the originating node of the "OSPF Prefix".  If PPR TLV
      is propagated to other areas the A-flag MUST be cleared.  In case
      if the originating node of the prefix has to be disambiguated for
      any reason including, if it is a Multi Homed Prefix (MHP) or
      propagated to a different OSPF area, then PPR-Attribute Sub-TLV
      Source Router ID SHOULD be included.

      Reserved: Reserved bits for future use.  Reserved bits MUST be
      reset on transmission and ignored on receive.

2.2.  PPR-Prefix Sub-TLV

   The structure of PPR-Prefix, for which path description is attached
   to is as follows:

        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               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |     MT-ID     | Prefix Length | Mask Length   |  Reserved     |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       //           OSPFv2 Prefix (variable)                          //
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |            PPR-Prefix  Sub-TLVs (variable)                    |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                    Figure 2: PPR-Prefix Sub-TLV Format



Chunduri, et al.         Expires January 3, 2019                [Page 6]


Internet-Draft    Preferred Path Routing (PPR) in OSPF         July 2018


   o  Type - TBD (See IANA for suggested value) from OSPFv2 PPR TLV
      Section 2 Sub-TLV registry.

   o  Length - Total length of the value field in bytes (variable).

   o  MT-ID - Multi-Topology ID (as defined in [RFC4915]).

   o  Prefix Len - contains the length of the prefix in bits.  Only the
      most significant octets of the Prefix are encoded.

   o  Mask Length - The length of the prefix in bits.  Only the most
      significant octets of the Prefix are encoded.

   o  OSPFv2 Prefix - represents the OSPFv2 prefix at the tail-end of
      the advertised PPR.  For the address family IPv4 unicast, the
      prefix itself is encoded as a 32-bit value.  The default route is
      represented by a prefix of length 0.

   o  PPR-Prefix Sub-TLVs - TBD.  It has 2 octet type, 2 octet length
      and value field is defined per type.

2.3.  PPR-ID Sub-TLV

   This represents the actual data plane identifier in the packet and
   could be of any data plane as defined in PPR-ID-type field.  Both
   OSPF Prefix and PPR-ID MUST belong to a same node in the network.

        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             |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |     PPR-ID Flags              | PPR-ID Type   | PPR-ID Length |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |PPR-ID Mask Len|  Algo         | PPR-ID                       //
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       //                 PPR-ID (cont., variable size)               //
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                      Figure 3: PPR-ID Sub-TLV Format

   o  Type - TBD (See IANA for suggested value) from OSPFv2 PPR TLV
      Section 2 Sub-TLV registry.

   o  Length - Total length of the value field in bytes (variable).

   o  PPR-ID Type - Data plane type of PPR-ID.  This is a new registry
      (TBD IANA) for this Sub-TLV and the defined types are as follows:



Chunduri, et al.         Expires January 3, 2019                [Page 7]


Internet-Draft    Preferred Path Routing (PPR) in OSPF         July 2018


   a.  Type: 1 MPLS SID/Label

   b.  Type: 2 Native IPv4 Address/Prefix

   o  PPR-ID Flags - 2 Octet field for PPR-ID flags:

        PPR-ID Flags Format

            0 1 2 3 4 5 6 7             15
           +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
           |L|A| Reserved                  |
           +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   1.  L - If set, the PPR path is a Loose-PPR.  If the flag is unset,
       then the path described is a Strict-PPR.  A Strict-PPR lists
       every single node or adjacency in the path description from
       source to the destination.

   2.  A - If set, all non-PPR path nodes in the OSPF area MUST add a
       FIB entry for the PPR-ID with NH set to the shortest path NH for
       the prefix being advertised.  The use of this is TBD.  By default
       this MUST be unset.

   3.  Reserved - Reserved bits for future use.  Reserved bits MUST be
       reset on transmission and ignored on receive.

   o  PPR-ID Length - Length of the PPR-ID field in octets and this
      depends on the PPR-ID type.  See PPR-ID below for the length of
      this field and other considerations.

   o  PPR-ID Mask Len - It is applicable for only for PPR-ID Type 2.
      For Type 1 this value MUST be set to zero.  It contains the length
      of the PPR-ID Prefix in bits.  Only the most significant octets of
      the Prefix are encoded.  This is needed, if PPR-ID followed is an
      IPv4 Prefix instead of 4 octet Address respectively.

   o  Algo - 1 octet value represents the SPF algorithm.  Algorithm
      registry is as defined in
      [I-D.ietf-ospf-segment-routing-extensions].

   o  PPR-ID - This is the Preferred Path forwarding identifier that
      would be on the data packet.  The value of this field is variable
      and it depends on the PPR-ID Type - for Type 1, this is and MPLS
      SID/Label.  For Type 2 this is a 4 byte IPv4 address.






Chunduri, et al.         Expires January 3, 2019                [Page 8]


Internet-Draft    Preferred Path Routing (PPR) in OSPF         July 2018


2.4.  PPR-PDE Sub-TLV

   This is a new Sub-TLV type in PPR TLV Section 2 and is called as PPR
   Path Description Element (PDE).  PPR-PDEs are used to describe the
   path in the form of set of contiguous and ordered Sub-TLVs, where
   first Sub-TLV represents (the top of the stack in MPLS data plane or)
   first node/segment of the path.  These set of ordered Sub-TLVs can
   have both topological SIDs and non-topological SIDs (e.g., service
   segments).

        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             |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | PPR-PDE Type  |  PDE-ID Type  |  PDE-ID Len   | Reserved      |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |     PPR-PDE Flags             | PDE-ID Value                 //
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       //             PDE-ID Value (Contd., Variable size)            //
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                  PPR-PDE  Sub-TLVs (variable)                 |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                     Figure 4: PPR-PDE Sub-TLV Format

   o  Type - TBD (See IANA for suggested value) from OSPFv2 PPR TLV
      Section 2 Sub-TLV registry.

   o  Length - Total length of the value field in bytes (variable).

   o  PPR-PDE Type - This is a new registry (TBD IANA) for this Sub-TLV
      and the defined types are as follows:

   a.  Type: 1 Topological

   b.  Type: 2 Non-Topological

   o  PDE-ID Type - 1 Octet PDE-forwarding IDentifier Type.  This is a
      new registry (TBD IANA) for this Sub-TLV and the defined types and
      corresponding PDE-ID Len, PDE-ID Value are as follows:

   a.  Type 1: SID/Label Sub-TLV as defined in
       [I-D.ietf-ospf-segment-routing-extensions].  PDE-ID Len and PDE-
       ID Value fields are per Section 2.1 of the referenced document.

   b.  Type 2: SR-MPLS Prefix SID.  PDE-ID Len and PDE-ID Value are same
       as Type 1.



Chunduri, et al.         Expires January 3, 2019                [Page 9]


Internet-Draft    Preferred Path Routing (PPR) in OSPF         July 2018


   c.  Type 3: SR-MPLS Adjacency SID.  PDE-ID Len and PDE-ID Value are
       same as Type 1.

   d.  Type 4: IPv4 Address.  PDE-ID Len is 4 bytes and PDE-ID Value is
       4 bytes IPv4 address encoded similar to IPv4 Prefix described in
       Section 2.2.

   o  PDE-ID Len - 1 Octet.  Length of PDE-ID field.

   o  Reserved - 1 Octet reserved bits for future use.  Reserved bits
      MUST be reset on transmission and ignored on receive.

   o  PPR-PDE Flags - 2 Octet flags for this TLV are described below:

        PPR-PDE Flags Format

            0 1 2 3 4 5 6 7...            15
           +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
           |L|D|   Reserved                |
           +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   1.  L: This bit indicates the type of next "Topological PDE-ID" in
       the path description and overrides the L bit in Section 2.3.  If
       set, the next PDE is Loose.  If this flag is unset, the next
       Topological PDE is Strict Type.

   2.  D: By default this bit MUST be unset.  This bit MUST be set only
       for PPR-PDE Type is Topological and this PDE represents the PDE-
       ID corresponding to the PPR-Prefix Section 2.2.

   3.  Reserved: Reserved bits for future use.  Reserved bits MUST be
       reset on transmission and ignored on receive.

   o  PPR-PDE Sub-TLVs - TBD.  It has 2 octet type, 2 octet length and
      value field is defined per type.

2.5.  PPR-Attributes Sub-TLV

   PPR-Attribute Sub-TLVs describe the attributes of the path.  The
   following Sub-TLVs draw from a new registry for Sub-TLV numbers; this
   registry is to be created by IANA, and administered using the first
   come first serve process:

   o  Type 1 (Suggested Value - IANA TBD): This is Packet Traffic
      accounting Sub-TLV.  Length 0 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.



Chunduri, et al.         Expires January 3, 2019               [Page 10]


Internet-Draft    Preferred Path Routing (PPR) in OSPF         July 2018


   o  Type 2 (Suggested Value - IANA TBD): This is Traffic statistics in
      Bytes Sub-TLV.  Length 0 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.

   o  Type 3 (Suggested Value - IANA TBD): PPR-Metric Sub-TLV.  Length 4
      bytes, and Value is metric of this path represented through the
      PPR-ID.  Different nodes can advertise the same PPR-ID for the
      same Prefix with a different set of PPR-PDE Sub-TLVs and the
      receiving node MUST consider the lowest metric value (TBD more, on
      what happens when metric is same for two different set of PPR-PDE
      Sub-TLVs).

3.  OSPFv3 PPR TLV

   The OSPFv3 PPR TLV s a top level TLV of the following LSAs defined in
   [I-D.ietf-ospf-ospfv3-lsa-extend].

      E-Intra-Area-Prefix-LSA

      E-Inter-Area-Prefix-LSA

      E-AS-External-LSA

      E-Type-7-LSA

   Multiple OSPFv3 PPR TLVs MAY be advertised in each LSA mentioned
   above.  The OSPFv3 PPR TLV has the following 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             |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |           PPR-Flags           |      AF       | Reserved      |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |          OSPFv3 PPR-Prefix Sub-TLV (variable size)            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |          PPR-ID     Sub-TLV (variable size)                   |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                  PPR-PDE Sub-TLVs (variable)                  |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                  PPR-Attribute Sub-TLVs(variable)             |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                      Figure 5: OSPFv3 PPR TLV Format



Chunduri, et al.         Expires January 3, 2019               [Page 11]


Internet-Draft    Preferred Path Routing (PPR) in OSPF         July 2018


   o  Type - TBD (IANA)from OSPF Extended Prefix Opaque LSA registry.

   o  Length - Total length of the value field in bytes (variable).

   o  PPR-Flags - 2 Octet flags for this TLV are described below.

   o  AF: Address family for the prefix.

   o

         AF: 0 - IPv4 unicast

         AF: 1 - IPv6 unicast

   o  Reserved - 1 Octet reserved bits for future use.  Reserved bits
      MUST be reset on transmission and ignored on receive.

   Flags: 2 octet field.  The following flags are defined:

        OSPFv3 PPR Flags Format

        0  1  2  3  4  5  6  7                       15
       +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
       |IA|A |        Rsrvd                            |
       +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+


      IA-Flag: Inter-Area flag.  If set, advertisement is of inter-area
      type.  An ABR that is advertising the OSPF PPR TLV between areas
      MUST set this bit.
      [I-D.ietf-ospf-ospfv3-segment-routing-extensions]

      A: The originator of the PPR TLV MUST set the A bit in order to
      signal that the prefixes and PPR-IDs advertised in the PPR TLV are
      directly connected to the originators.  If this bit is not set,
      this allows any other node in the network advertise this TLV on
      behalf of the originating node of the "OSPF Prefix".  If PPR TLV
      is propagated to other areas the A-flag MUST be cleared.  In case
      if the originating node of the prefix has to be disambiguated for
      any reason including, if it is a Multi Homed Prefix (MHP) or
      propagated to a different OSPF area, then PPR-Attribute Sub-TLV
      Source Router ID SHOULD be included.

      Rsrvd - reserved bits for future use.  Reserved bits MUST be reset
      on transmission and ignored on receive.






Chunduri, et al.         Expires January 3, 2019               [Page 12]


Internet-Draft    Preferred Path Routing (PPR) in OSPF         July 2018


3.1.  OSPFv3 PPR-Prefix Sub-TLV

   The structure of OSPFv3 PPR-Prefix, for which path description is
   attached to is as follows:

        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             |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | Prefix Length | Mask Length   |            Reserved           |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       //           OSPFv3 Prefix (variable)                          //
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |            PPR-Prefix  Sub-TLVs (variable)                    |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                Figure 6: OSPFv3 PPR-Prefix Sub-TLV Format

   o  Type - TBD (See IANA for suggested value) from OSPFv3 PPR TLV
      Section 3 Sub-TLV registry.

   o  Length - Total length of the value field in bytes (variable).

   o  Prefix Len - contains the length of the prefix in bits.  Only the
      most significant octets of the Prefix are encoded.

   o  Mask Length - The length of the prefix in bits.  Only the most
      significant octets of the Prefix are encoded.

   o  OSPFv3 Prefix - represents the OSPFv3 prefix at the tail-end of
      the advertised PPR.  For the address family IPv4 unicast, the
      prefix itself is encoded as a 32-bit value.  The default route is
      represented by a prefix of length 0.  For the address family (AF
      in OSPFv3 PPR TLV) in IPv6 unicast, the prefix, encoded as an even
      multiple of 32-bit words, padded with zeroed bits as necessary.
      This encoding consumes ((PrefixLength + 31) / 32) 32-bit words.

   o  PPR-Prefix Sub-TLVs - TBD.  It has 2 octet type, 2 octet length
      and value field is defined per type.

3.2.  OSPFv3 PPR-ID Sub-TLVs

   This represents the actual data plane identifier in the packet and
   could be of any data plane as defined in PPR-ID-type field.  Both
   OSPF Prefix and PPR-ID MUST belong to a same node in the network.





Chunduri, et al.         Expires January 3, 2019               [Page 13]


Internet-Draft    Preferred Path Routing (PPR) in OSPF         July 2018


        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             |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |     PPR-ID Flags              | PPR-ID Type   | PPR-ID Length |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |PPR-ID Mask Len|  Algo         | PPR-ID                       //
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       //                 PPR-ID (cont, variable size)                //
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                  Figure 7: OSPFv3 PPR-ID Sub-TLV Format

   o  Type - TBD (See IANA for suggested value) from OSPFv3 PPR TLV
      Section 3 Sub-TLV registry.

   o  Length - Total length of the value field in bytes (variable).

   o  PPR-ID Type - Data plane type of PPR-ID.  This is a new registry
      (TBD IANA) for this Sub-TLV and the defined types are as follows:

   a.  Type: 1 MPLS SID/Label

   b.  Type: 2 Native IPv4 Address/Prefix

   c.  Type: 3 Native IPv6 Address/Prefix

   d.  Type: 4 IPv6 SID in SRv6 with SRH

   o  PPR-ID Flags - 2 Octet field for PPR-ID flags:

        PPR-ID Flags Format

          0 1 2 3 4 5 6 7             15
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |L|A| Rsrvd                     |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   1.  L - If set, the PPR path is a Loose-PPR.  If the flag is unset,
       then the path described is a Strict-PPR.  A Strict-PPR lists
       every single node or adjacency in the path description from
       source to the destination.

   2.  A - If set, all non-PPR path nodes in the OSPF area MUST add a
       FIB entry for the PPR-ID with NH set to the shortest path NH for




Chunduri, et al.         Expires January 3, 2019               [Page 14]


Internet-Draft    Preferred Path Routing (PPR) in OSPF         July 2018


       the prefix being advertised.  The use of this is TBD.  By default
       this MUST be unset.

   3.  Reserved - Reserved bits for future use.  Reserved bits MUST be
       reset on transmission and ignored on receive.

   o  PPR-ID Length - Length of the PPR-ID field in octets and this
      depends on the PPR-ID type.  See PPR-ID below for the length of
      this field and other considerations.

   o  PPR-ID Mask Len - It is applicable for only for PPR-ID Type 2, 3
      and 4.  For Type 1 this value MUST be set to zero.  It contains
      the length of the PPR-ID Prefix in bits.  Only the most
      significant octets of the Prefix are encoded.  This is needed, if
      PPR-ID followed is an IPv4/IPv6 Prefix instead of 4/16 octet
      Address respectively.

   o  Algo - 1 octet value represents the SPF algorithm.  Algorithm
      registry is as defined in
      [I-D.ietf-ospf-ospfv3-segment-routing-extensions].

   o  PPR-ID - This is the Preferred Path forwarding identifier that
      would be on the data packet.  The value of this field is variable
      and it depends on the PPR-ID Type - for Type 1, this is and MPLS
      SID/Label.  For Type 2 this is a 4 byte IPv4 address.  For Type 3
      this is a 16 byte IPv6 address.  For Type 2 and Type 3 encoding is
      similar to OSPF Prefix as specified in Section 2.2.  For Type 4,
      it is a 16 byte IPv6 SID.

3.3.  OSPFv3 PPR-PDE Sub-TLV

   This is a new Sub-TLV type in PPR TLV Section 3 and is called as PPR
   Path Description Element (PDE).  PPR-PDEs are used to describe the
   path in the form of set of contiguous and ordered Sub-TLVs, where
   first Sub-TLV represents (the top of the stack in MPLS data plane or)
   first node/segment of the path.  These set of ordered Sub-TLVs can
   have both topological SIDs and non-topological SIDs (e.g., service
   segments).













Chunduri, et al.         Expires January 3, 2019               [Page 15]


Internet-Draft    Preferred Path Routing (PPR) in OSPF         July 2018


        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             |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | PPR-PDE Type  |  PDE-ID Type  |  PDE-ID Len   | Reserved      |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |     PPR-PDE Flags             | PDE-ID Value                 //
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       //             PDE-ID Value (Contd., Variable size)            //
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                  PPR-PDE  Sub-TLVs (variable)                 |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                  Figure 8: OSPFv3 PPR-PDE Sub-TLV Format

   o  Type - TBD (See IANA for suggested value) from OSPFv3 PPR TLV
      Section 3 Sub-TLV registry.

   o  Length - Total length of the value field in bytes (variable).

   o  PPR-PDE Type - This is a new registry (TBD IANA) for this Sub-TLV
      and the defined types are as follows:

   a.  Type: 1 Topological

   b.  Type: 2 Non-Topological

   o  PDE-ID Type - 1 Octet PDE-forwarding IDentifier Type.  This is a
      new registry (TBD IANA) for this Sub-TLV and the defined types and
      corresponding PDE-ID Len, PDE-ID Value are as follows:

   a.  Type 1: SID/Label Sub-TLV as defined in
       [I-D.ietf-ospf-segment-routing-extensions].  PED-ID Len and PDE-
       ID Value fields are per Section 2.1 of the referenced document.

   b.  Type 2: SR-MPLS Prefix SID.  PDE-ID Len and PDE-ID Value are same
       as Type 1.

   c.  Type 3: SR-MPLS Adjacency SID.  PDE-ID Len and PDE-ID Value are
       same as Type 1.

   d.  Type 4: IPv4 Address.  PDE-ID Len is 4 bytes and PDE-ID Value is
       4 bytes IPv4 address encoded similar to IPv4 Prefix described in
       Section 2.2.






Chunduri, et al.         Expires January 3, 2019               [Page 16]


Internet-Draft    Preferred Path Routing (PPR) in OSPF         July 2018


   e.  Type 5: IPv6 Address.  PDE-ID Len is 16 bytes and PDE-ID Value is
       16 bytes IPv6 address encoded similar to IPv6 Prefix described in
       Section 2.2.

   f.  Type 6: SRv6 Node SID as defined in
       [I-D.li-ospf-ospfv3-srv6-extensions].  PDE-ID Len and PDE-ID
       Value are as defined in SRv6 SID.

   g.  Type 7: SRv6 Adjacency-SID.  PDE-ID Len and PDE-ID Value are as
       defined in Type 6.

   o  PDE-ID Len - 1 Octet.  Length of PDE-ID field.

   o  Reserved - 1 Octet reserved bits for future use.  Reserved bits
      MUST be reset on transmission and ignored on receive.

   o  PPR-PDE Flags - 2 Octet flags for this TLV are described below:

        PPR-PDE Flags Format

          0 1 2 3 4 5 6 7...          15
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |L|D|   Rsrvd                   |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   1.  L - This bit indicates the type of next "Topological PDE-ID" in
       the path description and overrides the L bit in Section 3.2.  If
       set, the next PDE is Loose.  If this flag is unset, the next
       Topological PDE is Strict Type.

   2.  D - By default this bit MUST be unset.  This bit MUST be set only
       for PPR-PDE Type is Topological and this PDE represents the PDE-
       ID corresponding to the PPR-Prefix Section 3.1.

   3.  Rsrvd - Reserved bits for future use.  Reserved bits MUST be
       reset on transmission and ignored on receive.

   o  PPR-PDE Sub-TLVs - TBD.  It has 2 octet type, 2 octet length and
      value field is defined per type.

3.4.  OSPFv3 PPR-Attributes Sub-TLV

   PPR-Attribute Sub-TLVs describe the attributes of the path.  The
   following Sub-TLVs draw from a new registry for Sub-TLV numbers; this
   registry is to be created by IANA, and administered using the first
   come first serve process:




Chunduri, et al.         Expires January 3, 2019               [Page 17]


Internet-Draft    Preferred Path Routing (PPR) in OSPF         July 2018


   o  Type 1 (Suggested Value - IANA TBD): This is Packet Traffic
      accounting Sub-TLV.  Length 0 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 2 (Suggested Value - IANA TBD): This is Traffic statistics in
      Bytes Sub-TLV.  Length 0 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.

   o  Type 3 (Suggested Value - IANA TBD): PPR-Metric Sub-TLV.  Length 4
      bytes, and Value is metric of this path represented through the
      PPR-ID.  Different nodes can advertise the same PPR-ID for the
      same Prefix with a different set of PPR-PDE Sub-TLVs and the
      receiving node MUST consider the lowest metric value (TBD more, on
      what happens when metric is same for two different set of PPR-PDE
      Sub-TLVs).

4.  Other Considerations

   Please refer to [I-D.chunduri-isis-preferred-path-routing] section 4,
   5, 6 and 7.

5.  Acknowledgements

   Thanks to Richard Li, Alex Clemm, Padma Pillay-Esnault, Toerless
   Eckert, Kiran Makhijani and Lin Han for initial discussions on this
   topic.  Thanks to Kevin Smith and Stephen Johnson for various
   deployment scenarios applicability from ETSI WGs perspective.
   Authors also acknowledge Alexander Vainshtein for detailed
   discussions and suggestions on this topic.

   Earlier versions of draft-ietf-ospf-segment-routing-extensions have a
   mechanism to advertise EROs through Binding SID.

6.  IANA Considerations

   This document requests the following new TLV in IANA OSPFv2 and
   OSPFv3 TLV code-point registry as specified in Section 2 Section 3
   respectively .

        TLV #   Name
        -----   --------------
        TBD     PPR TLV






Chunduri, et al.         Expires January 3, 2019               [Page 18]


Internet-Draft    Preferred Path Routing (PPR) in OSPF         July 2018


   This document also requests IANA to create new registries for PPR TLV
   Flags field, PPR Flags, and PPR Sub-TLVs in PPR TLV as described in
   Section 2 and Section 3.

7.  Security Considerations

   Existing security extensions as 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.

   Advertisement of the additional information defined in this document
   introduces no new security concerns in OSPF 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.

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>.

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

   [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>.

8.2.  Informative 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-00 (work in
              progress), June 2018.








Chunduri, et al.         Expires January 3, 2019               [Page 19]


Internet-Draft    Preferred Path Routing (PPR) in OSPF         July 2018


   [I-D.ietf-6man-segment-routing-header]
              Filsfils, C., Previdi, S., Leddy, J., Matsushima, S., and
              d. daniel.voyer@bell.ca, "IPv6 Segment Routing Header
              (SRH)", draft-ietf-6man-segment-routing-header-14 (work in
              progress), June 2018.

   [I-D.ietf-ospf-ospfv3-lsa-extend]
              Lindem, A., Roy, A., Goethals, D., Vallem, V., and F.
              Baker, "OSPFv3 LSA Extendibility", draft-ietf-ospf-ospfv3-
              lsa-extend-23 (work in progress), January 2018.

   [I-D.ietf-ospf-ospfv3-segment-routing-extensions]
              Psenak, P., Filsfils, C., Previdi, S., Gredler, H.,
              Shakir, R., Henderickx, W., and J. Tantsura, "OSPFv3
              Extensions for Segment Routing", draft-ietf-ospf-ospfv3-
              segment-routing-extensions-13 (work in progress), May
              2018.

   [I-D.ietf-ospf-segment-routing-extensions]
              Psenak, P., Previdi, S., Filsfils, C., Gredler, H.,
              Shakir, R., Henderickx, W., and J. Tantsura, "OSPF
              Extensions for Segment Routing", draft-ietf-ospf-segment-
              routing-extensions-25 (work in progress), April 2018.

   [I-D.ietf-spring-segment-routing]
              Filsfils, C., Previdi, S., Ginsberg, L., Decraene, B.,
              Litkowski, S., and R. Shakir, "Segment Routing
              Architecture", draft-ietf-spring-segment-routing-15 (work
              in progress), January 2018.

   [I-D.li-ospf-ospfv3-srv6-extensions]
              Li, Z., Hu, Z., Cheng, D., Talaulikar, K., and P. Psenak,
              "OSPFv3 Extensions for SRv6", draft-li-ospf-
              ospfv3-srv6-extensions-01 (work in progress), March 2018.

   [RFC4915]  Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P.
              Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF",
              RFC 4915, DOI 10.17487/RFC4915, June 2007,
              <https://www.rfc-editor.org/info/rfc4915>.

   [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>.







Chunduri, et al.         Expires January 3, 2019               [Page 20]


Internet-Draft    Preferred Path Routing (PPR) in OSPF         July 2018


   [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>.

Authors' Addresses

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

   Email: uma.chunduri@huawei.com


   Yingzhen Qu
   Huawei USA
   2330 Central Expressway
   Santa Clara, CA  95050
   USA

   Email: yingzhen.qu@huawei.com


   Russ White
   LinkedIn
   Oak Island, NC  28465
   USA

   Email: russ@riw.us


   Jeff Tantsura
   Nuage Networks
   755 Ravendale Drive
   Mountain View, CA  94043
   USA

   Email: jefftant.ietf@gmail.com











Chunduri, et al.         Expires January 3, 2019               [Page 21]


Internet-Draft    Preferred Path Routing (PPR) in OSPF         July 2018


   Luis M. Contreras
   Telefonica
   Sur-3 building, 3rd floor
   Madrid  28050
   Spain

   Email: luismiguel.contrerasmurillo@telefonica.com












































Chunduri, et al.         Expires January 3, 2019               [Page 22]

Html markup produced by rfcmarkup 1.128b, available from https://tools.ietf.org/tools/rfcmarkup/