



PCE                                                             Q. Xiong
Internet-Draft                                                   S. Peng
Intended status: Standards Track                         ZTE Corporation
Expires: 8 November 2026                                       V. Beeram
                                                        Juniper Networks
                                                                 T. Saad
                                                           Cisco Systems
                                                            M. Koldychev
                                                       Ciena Corporation
                                                              7 May 2026


 Path Computation Element Communication Protocol (PCEP) Extensions for
                            Topology Filter
                   draft-ietf-pce-topology-filter-01

Abstract

   A topology filter is a data construct that is used to filter network
   topologies.  The Path Computation Element (PCE) MUST take into
   account the topology related constraints during the path computation.
   This document proposes a set of extensions for Path Computation
   Element Communication Protocol (PCEP) to support the topology filter.

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."

   This Internet-Draft will expire on 8 November 2026.

Copyright Notice

   Copyright (c) 2026 IETF Trust and the persons identified as the
   document authors.  All rights reserved.






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   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
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
     1.2.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  Topology Filter with PCE  . . . . . . . . . . . . . . . . . .   4
   3.  PCEP Extensions . . . . . . . . . . . . . . . . . . . . . . .   4
     3.1.  TOPOLOGY-FILTER Object  . . . . . . . . . . . . . . . . .   4
       3.1.1.  IGP Domain Identifier . . . . . . . . . . . . . . . .   5
         3.1.1.1.  Protocol ID TLV . . . . . . . . . . . . . . . . .   5
         3.1.1.2.  Multi-topology ID TLV . . . . . . . . . . . . . .   6
         3.1.1.3.  Algorithm ID TLV  . . . . . . . . . . . . . . . .   7
         3.1.1.4.  Domain ID TLV . . . . . . . . . . . . . . . . . .   7
       3.1.2.  TE Topology Identifier  . . . . . . . . . . . . . . .   7
         3.1.2.1.  Provider ID TLV . . . . . . . . . . . . . . . . .   7
         3.1.2.2.  Client ID TLV . . . . . . . . . . . . . . . . . .   8
         3.1.2.3.  Topology ID TLV . . . . . . . . . . . . . . . . .   8
       3.1.3.  Filtering Rules . . . . . . . . . . . . . . . . . . .   9
         3.1.3.1.  Admin Group Filtering Rules . . . . . . . . . . .   9
         3.1.3.2.  Information Source Filtering Rules  . . . . . . .  10
     3.2.  OPEN Object . . . . . . . . . . . . . . . . . . . . . . .  13
       3.2.1.  TOPOLOGY-FILTER-CAPABILITY TLV  . . . . . . . . . . .  13
   4.  Operation . . . . . . . . . . . . . . . . . . . . . . . . . .  15
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  15
     5.1.  PCEP Object . . . . . . . . . . . . . . . . . . . . . . .  16
     5.2.  PCEP TLVs . . . . . . . . . . . . . . . . . . . . . . . .  16
     5.3.  PCEP-Error Object . . . . . . . . . . . . . . . . . . . .  18
     5.4.  Flags in the TOPOLOGY-FILTER-CAPABILITY TLV . . . . . . .  18
     5.5.  Flags in the Info Source sub-TLV  . . . . . . . . . . . .  19
   6.  Operational Considerations  . . . . . . . . . . . . . . . . .  19
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  19
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  20
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  20
     9.1.  Infomative References . . . . . . . . . . . . . . . . . .  20
     9.2.  Normative References  . . . . . . . . . . . . . . . . . .  20
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  23






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1.  Introduction

   [RFC5440] describes the Path Computation Element Computation Protocol
   (PCEP) which is used between a Path Computation Element (PCE) and a
   Path Computation Client (PCC) (or other PCE) to enable computation of
   Multi-protocol Label Switching (MPLS) for Traffic Engineering Label
   Switched Path (TE LSP).  PCEP Extensions for the Stateful PCE Model
   [RFC8231] describes a set of extensions to PCEP to enable active
   control of MPLS-TE and Generalized MPLS (GMPLS) tunnels.  As depicted
   in [RFC4655], a PCE MUST be able to compute the path of a TE LSP by
   operating on the TED and considering bandwidth and other constraints
   applicable to the TE LSP service request.

   A PCE may perform path computation based on the network topology
   information collected through BGP-LS [RFC9552] or YANG [RFC8776].  It
   can get multiple link-state data from multiple IGP instance, or
   multiple virtual topologies from a single IGP instance.  As described
   in [I-D.ietf-teas-yang-topology-filter], a topology may be associated
   with an Network Resource Partition (NRP) as per [RFC9543].  In other
   cases, a topology related constraints are also specified for TE path
   computation.  For example, a path may be computed within a network
   topology such as a specified topology, a topology associated with a
   specific IGP domain, a topology learnt from a specific TE information
   source, and a topology defined by the application of one or more
   topology filters.  The PCE SHOULD also consider the topology related
   constraints to construct the topology filter during the path
   computation.

   As defined in [I-D.ietf-teas-yang-topology-filter], a topology filter
   is a data construct that is used to filter network topologies.  This
   document proposes a set of extensions for PCEP to support the
   topology filter during path computation.

1.1.  Terminology

   The terminology is defined as [RFC5440], [RFC9552] and [RFC8795].

1.2.  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.







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2.  Topology Filter with PCE

   [I-D.ietf-teas-yang-topology-filter] defined a construct for topology
   filters and the filtering rules to specify a set of topology
   constraints and the YANG model can be applied in centrallized
   controller.  And in PCE scenarios, a path is required to be computed
   within a topology which may apply the topology filters to construct
   the topology.  So the PCE MUST consider the corresponding topology
   related constraints and filtering rules during path computation.

   As defined in [I-D.ietf-teas-yang-topology-filter], a logical
   topology can be associated with an NRP as per [RFC9543] and an NRP
   can be identified using NRP Identifier (NRP-ID) as per
   [I-D.ietf-teas-ns-ip-mpls].  An NRP TLV which carries the NRP-ID can
   be used to filter the NRP topology as per [I-D.ietf-pce-pcep-nrp]
   section 2.1.

   Furthermore, as per [I-D.ietf-teas-yang-topology-filter], a topology
   filter specifies the topology reference and/or a set of filtering
   rules that can be applied on either the native topology or a user
   specified topology.  The topology reference indicates a predefined TE
   topology or a specific IGP domain.  A TE topology can be identified
   from a global scope such as a Provider ID, a Client ID, a Topology ID
   as per [RFC8776].  An IGP domain has a unique IGP representation by
   using the combination of Area-ID, Router-ID, Protocol-ID, Multi-
   Topology Identifier (MT-ID), and BGP-LS Instance-ID as per [RFC9552].

   The filtering rules specify a set of constraints on the topology
   including include-any, include-all and exclude.  A set of attributes
   that can be used as rules to filter the topology such as link
   affinity, link name, node prefix, AS number and TE information
   source.  The filtering rules of these attributes can be used to
   compute path at PCE.

3.  PCEP Extensions

3.1.  TOPOLOGY-FILTER Object

   This document defines a new TOPOLOGY-FILTER object to carry the
   topology filter.  The TOPOLOGY-FILTER object is optional and
   specifies the specific topology to be taken into account by the PCE
   during path computation.  The TOPOLOGY-FILTER object must be
   presented once and other TOPOLOGY-FILTER objects MUST be ignored if
   multiple TOPOLOGY-FILTER objects appreared.

   TOPOLOGY-FILTER Object-Class is TBD1.

   TOPOLOGY-FILTER Object-Type is TBD2.



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   The format of the TOPOLOGY-FILTER object body is:

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |               Reserved                        |     Flags     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      //                      Optional TLVs                          //
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                Figure 1: TOPOLOGY-FILTER Body Object Format

   Reserved (24 bits): This field MUST be set to zero on transmission
   and MUST be ignored on receipt.

   Flags (8 bits): No flags are currently defined.  Unassigned flags
   MUST be set to zero on transmission and MUST be ignored on receipt.

   The format of optional TLVs is defined in [RFC5440] and may be used
   to carry topology filter information as defined in following
   sections.  The existing topology constraints TLVs could also be
   reused such as Algorithm ID TLV and Domain ID TLV.  These TLVs can be
   carried but each type can only be presented once.  And it MUST be
   applied to filter the resources that match all presenting TLVs at the
   same time.

3.1.1.  IGP Domain Identifier

   A specific IGP domain can be identified by a combination of Protocol
   ID, Instance ID, MT-ID as per [RFC9552] and Division ID as per
   [RFC8685] and Algorithm ID as per [I-D.ietf-pce-sid-algo].  This
   document defines some TLVs for topology filter to identify an IGP
   domain within a referenced topology.  The Protocol ID TLV is
   mandatory to identify an IGP domain and others are optional to carry
   the additional information to further filter permitted resources
   within the domain.

3.1.1.1.  Protocol ID TLV

   The Protocol ID TLV is mandatory to identify an IGP domain and it is
   defined to carry the Protocol ID and Instance ID.

   The format of the Protocol ID TLV is :






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        0                   1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |         Type=TBD3             |            Length=12          |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |  Protocol-ID  |                  Reserved                     |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                         Instance-ID                           |
       |                         (64 bits)                             |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                         Figure 2: Protocol ID TLV

   The code point for the TLV type is TBD3.  The TLV length is 12
   octets.

   Protocol-ID (8 bits): defined in [RFC9552] section 5.2.

   Instance-ID (64 bits): defined in [RFC9552] section 5.2.

   Reserved: This fields MUST be set to zero on transmission and MUST be
   ignored on receipt.

3.1.1.2.  Multi-topology ID TLV

   The Multi-topology ID TLV is optional and is defined to carry the MT-
   ID.

   The format of the Multi-topology ID TLV is :


       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=TBD4             |            Length=4           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |R R R R|   Multi-Topology-ID   |          Reserved             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                      Figure 3: Multi-topology ID TLV

   The code point for the TLV type is TBD4.  The TLV length is 4 octets.

   Multi-Topology-ID (12 bits): it indicates the IS-IS MT-ID as defined
   in Sections 7.1 and 7.2 of [RFC5120] or the OSPF MT-ID as defined in
   Section 3.7 of [RFC4915].



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   Reserved (16 bits): This field MUST be set to zero on transmission
   and MUST be ignored on receipt.

3.1.1.3.  Algorithm ID TLV

   The Algorithm ID TLV is optional and is defined to carry the
   Algorithm ID.

   The Algorithm ID TLV MAY be inserted so as to provide the Flex-algo
   plane information for the computed path.  The format of the TLV is
   defined in [I-D.ietf-pce-sid-algo] section 4.4.

   The Algorithm ID is a filter constraint for IGP domain iderntifier
   and it will based on the Flex-algo participation only.  It is valid
   to do path computation for different algorithms using SR-Algorithm
   TLV as defined in [I-D.ietf-pce-sid-algo].

3.1.1.4.  Domain ID TLV

   The Domain ID TLV is optional and is defined to carry the Domain-ID.

   The Domain ID TLV MAY be inserted so as to identify the domains
   served by the PCE.  The format of the TLV is defined in [RFC8685]
   section 3.2.2.

3.1.2.  TE Topology Identifier

   This document defines some TE Topology Identifier TLVs for topology
   filter to identify a predefined TE topology within a referenced
   topology.

3.1.2.1.  Provider ID TLV

   The Provider ID TLV is optional and the format is as following shown:


       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=TBD5             |            Length=4           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           Provider-ID                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



                         Figure 4: Provider ID TLV




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   The code point for the TLV type is TBD5.  The TLV length is 4 octets.

   Provider-ID (32 bits): an identifier to uniquely identify a provider
   as defined in [RFC8776].

3.1.2.2.  Client ID TLV

   The Client ID TLV is optional and the format is as following shown:


       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=TBD6             |            Length=4           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           Client-ID                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                          Figure 5: Client ID TLV

   The code point for the TLV type is TBD6.  The TLV length is 4 octets.

   Client-ID (32 bits): an identifier to uniquely identify a client as
   defined in [RFC8776].

3.1.2.3.  Topology ID TLV

   The Topology ID TLV is optional and the format is as following shown:


       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=TBD7             |            Length=4           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           Topology-ID                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



                         Figure 6: Topology ID TLV

   The code point for the TLV type is TBD7.  The TLV length is 4 octets.

   Topology-ID (32 bits): an identifier for a topology as defined in
   [RFC8776].




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3.1.3.  Filtering Rules

   This document defines some TLVs for Filtering Rules of topology
   filter to carry a set of constrains on the topology by include-any,
   include-all and exclude.

3.1.3.1.  Admin Group Filtering Rules

3.1.3.1.1.  Include-Any Admin Group TLV

   The Include-Any Admin Group TLV is used to include the links with
   include-any rule that is used during the path calculation.


       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=TBD8             |            Length=variable    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                      Extended Admin Group                     |
      +-                                                             -+
      |                            ...                                |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                   Figure 7: Include-Any Admin Group TLV

   The code point for the TLV type is TBD8.  The length is variable and
   depends on the size of the Extended Admin Group.  It MUST be a
   multiple of 4 octets.

   Extended Administrative Group: Extended Administrative Group as
   defined in [RFC7308].

3.1.3.1.2.  Include-All Admin Group TLV

   The Include-All Admin Group TLV is used to include the links with
   include-all rule that is used during the path calculation.













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       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Type=TBD9             |            Length=variable    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                      Extended Admin Group                     |
      +-                                                             -+
      |                            ...                                |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                   Figure 8: Include-All Admin Group TLV

   The code point for the TLV type is TBD9.  The length is variable and
   depends on the size of the Extended Admin Group.  It MUST be a
   multiple of 4 octets.

   Extended Administrative Group: Extended Administrative Group as
   defined in [RFC7308].

3.1.3.1.3.  Exclude Admin Group TLV

   The Exclude Admin Group TLV is used to exclude the links that is used
   during the path calculation.


       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=TBD10            |            Length=variable    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                      Extended Admin Group                     |
      +-                                                             -+
      |                            ...                                |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                     Figure 9: Exclude Admin Group TLV

   The code point for the TLV type is TBD10.  The length is variable and
   depends on the size of the Extended Admin Group.  It MUST be a
   multiple of 4 octets.

   Extended Administrative Group: Extended Administrative Group as
   defined in [RFC7308].

3.1.3.2.  Information Source Filtering Rules




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3.1.3.2.1.  Include-Any Information Source TLV

   The Include-Any Information Source TLV is used to include the IGP
   topology information source with include-any rule that is used during
   the path calculation.


       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=TBD11            |            Length=variable    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                  List of Info Source sub-TLVs                 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


               Figure 10: Include-Any Information Source TLV

   The code point for the TLV type is TBD11.  The length is variable.

   sub-TLVs: Include-Any Information Source TLV will carry a list of
   Info Source sub-TLVs with 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=TBD12            |         Length                |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |  Protocol-ID  |    Flags  |I|D|          Reserved             |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                          Instance-ID                          |
       |                           (64 bits)                           |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | Domain Type   |                  Reserved                     |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       //                          Domain-ID                          //
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                       Figure 11: Info Source sub-TLV

   The code point for the sub-TLV type is TBD12.  The sub-TLV length is
   variable.

   Protocol-ID (8 bits): defined in [RFC9552] section 5.2.



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   Instance-ID (64 bits): defined in [RFC9552] section 5.2.

   Domain Type (8 bits): defined in [RFC8685] section 3.2.2.

   Domain-ID (variable): defined in [RFC8685] section 3.2.2.

   The value comprises a single field -- Flags (8 bits):

   I (Instance ID bit): If set, will signal that the Instance-ID field
   is present.

   D (Instance ID bit): If set, will signal that the Domain-ID field is
   present.

   The Protocol-ID is mandatory for the Info Source sub-TLV.

3.1.3.2.2.  Include-All Information Source TLV

   The Include-All Information Source TLV is used to include the IGP
   topology information source with include-all rule that is used during
   the path calculation.


       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=TBD13            |            Length=variable    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                 List of Info Source sub-TLVs                  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


               Figure 12: Include-All Information Source TLV

   The code point for the TLV type is TBD13.  The length is variable.

   sub-TLVs: Include-All Information Source TLV will carry a list of
   Info Source sub-TLVs.

3.1.3.2.3.  Exclude Information Source TLV

   The Exclude Information Source TLV is used to exclude the IGP
   topology information source that is used during the path calculation.








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       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         Type=TBD14            |            Length=variable    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                 List of Info Source sub-TLVs                  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                 Figure 13: Exclude Information Source TLV

   The code point for the TLV type is TBD14.  The length is variable.

   sub-TLVs: Exclude Information Source TLV will carry a list of Info
   Source sub-TLVs.

3.2.  OPEN Object

3.2.1.  TOPOLOGY-FILTER-CAPABILITY TLV

   A PCEP speaker indicates whether it supports topology related
   constraints path computation using a new PCEP capability called
   "TOPOLOGY-FILTER-CAPABILITY".  When the PCEP session is created, it
   sends an OPEN message with an OPEN Object containing the TOPOLOGY-
   FILTER-CAPABILITY TLV.

   The TOPOLOGY-FILTER-CAPABILITY TLV is an optional TLV in OPEN object
   [RFC5440] to exchange the topology filter capability of PCEP
   speakers.  Its format is shown in the following figure:



       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=TBD15      |              Length=4         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                         Flags               |I|G|T|C|P|D|A|M|S|
      +---------------------------------------------------------------+

              Figure 14: TOPOLOGY-FILTER-CAPABILITY TLV Format

   The type of the TLV is TBD1, and it has a fixed length of 4 octets.

   The value comprises a single field -- Flags (32 bits):






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   S (Source Protocol ID Capability bit): If set, will signal that the
   PCE or the PCC supports the Protocol ID TLV of the topology filter
   capability in section 3.1.1.1.

   M (Multi-topology ID Capability bit): If set, will signal that the
   PCE or the PCC supports the Multi-topology ID TLV of the topology
   filter capability in section 3.1.1.2.  The S bit MUST be also set
   when M bit is set.

   A (Algorithm ID Capability bit): If set, will signal that the PCE or
   the PCC supports the topology filter capability and the Algorithm ID
   TLV can be carried in TOPOLOGY-FILTER object as per section 3.1.1.3.
   The S bit MUST be also set when A bit is set.

   D (Domain ID Capability bit): If set, will signal that the PCE or the
   PCC supports the topology filter capability and the Domain ID TLV can
   be carried in TOPOLOGY-FILTER object as per section 3.1.1.4.  The S
   bit MUST be also set when D bit is set.

   P (Provider ID Capability bit): If set, will signal that the PCE or
   the PCC supports the Provider ID TLV of the topology filter
   capability in section 3.1.2.1.

   C (Client ID Capability bit): If set, will signal that the PCE or the
   PCC supports the Client ID TLV of the topology filter capability in
   section 3.1.2.2.

   T (Topology ID Capability bit): If set, will signal that the PCE or
   the PCC supports the Topology ID TLV of the topology filter
   capability in section 3.1.2.3.

   G (Admin Group Capability bit): If set, will signal that the PCE or
   the PCC supports the Admin Group filtering rules TLVs of the topology
   filter capability in section 3.1.3.1.

   I (Information Source Capability bit): If set, will signal that the
   PCE or the PCC supports the Information Source filtering rules TLVs
   of the topology filter capability in section 3.1.3.2.

   Unassigned bits MUST be set to 0 on transmission and MUST be ignored
   on receipt.










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4.  Operation

   The PCE could perform path computation based on the topology
   identified by the topology filter that can be applied on either the
   native topology or a user specified topology.  When the Protocol ID
   TLV is absent with other TLVs presenting as IGP domain identifiers,
   the receiving PCEP speaker MUST respond with a PCErr message with
   Error-Type 19 (Invalid Operation) and Error-Value TBD16 (Protocol ID
   is absent).  The absence of the IGP Domain Identifier TLVs and TE
   Topology Identifier TLVs indicate that the PCE should compute within
   a native topology and only Filtering Rules TLVs are applied as the
   filtering rules.

   A PCC MAY insert a TOPOLOGY-FILTER object in PCReq message to
   indicate the specific topology that MUST be considered by the PCE
   during path computation.  The PCE MAY ignore the object when P flag
   is cleared based on rules describedas per section 7.2 in [RFC5440].
   The PCE will compute the path with the constrains with the filtering
   rules and reply the result to the PCC with a PCRep message.  The
   TOPOLOGY-FILTER object can be carried within a PCRep message in case
   of unsuccessful path computation.  In this unsuccessful case, the
   PCRep message also contains a NO-PATH object, and the TOPOLOGY-FILTER
   object is used to indicate the set of topology filter constriants
   that could not be satisfied.

   In stateful mode, the following procedures apply:

   For PCC-initiated LSPs: A PCC MAY include a TOPOLOGY-FILTER object in
   a PCRpt message when delegating an LSP to the PCE, to indicate the
   topology filter constraints that MUST be applied during path
   computation.  The PCE SHOULD include the TOPOLOGY-FILTER object in a
   PCUpd message only when path computation cannot be completed because
   the referenced topology or domain is not known to the PCE; in that
   case the PCUpd MUST also include a empty ERO to indicate the failure.
   If path computation succeeds, the PCE MAY omit the TOPOLOGY-FILTER
   object from PCUpd.

   For PCE-initiated LSPs: A PCE MAY include a TOPOLOGY-FILTER object in
   a PCInitiate message.  The PCC MUST reflect the TOPOLOGY-FILTER
   object in the corresponding PCRpt message and in all subsequent PCRpt
   messages for the same LSP.

5.  IANA Considerations








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5.1.  PCEP Object

   IANA is requested to make new allocations within the "PCEP Objects"
   subregistry of the "Path Computation Element Protocol (PCEP) Numbers"
   registry:

           +==============+=======================+===========+
           | Object-Class |      Object-Type      | Reference |
           |    Value     |       Value:Name      |           |
           +==============+=======================+===========+
           |     TBD1     |      0: Reserved      |   [this   |
           |              |                       | document] |
           |              | TBD2: TOPOLOGY-FILTER |           |
           +--------------+-----------------------+-----------+

                                 Table 1

   Object-Type values are managed via the IETF Review policy as per
   [RFC8126].

5.2.  PCEP TLVs

   IANA is requested to make new allocations in the "PCEP TLV Type
   Indicators" registry:



























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   +================+================================+=================+
   | TLV Type Value |            TLV name            |    Reference    |
   +================+================================+=================+
   |      TBD3      |          Protocol ID           | [this document] |
   +----------------+--------------------------------+-----------------+
   |      TBD4      |       Multi-topology ID        | [this document] |
   +----------------+--------------------------------+-----------------+
   |      TBD5      |          Provider ID           | [this document] |
   +----------------+--------------------------------+-----------------+
   |      TBD6      |           Client ID            | [this document] |
   +----------------+--------------------------------+-----------------+
   |      TBD7      |          Topology ID           | [this document] |
   +----------------+--------------------------------+-----------------+
   |      TBD8      |        Filtering Rules         | [this document] |
   +----------------+--------------------------------+-----------------+
   |      TBD8      |    Include-Any Admin Group     | [this document] |
   +----------------+--------------------------------+-----------------+
   |      TBD9      |    Include-All Admin Group     | [this document] |
   +----------------+--------------------------------+-----------------+
   |     TBD10      |      Exclude Admin Group       | [this document] |
   +----------------+--------------------------------+-----------------+
   |     TBD11      |    Include-Any Information     | [this document] |
   |                |             Source             |                 |
   +----------------+--------------------------------+-----------------+
   |     TBD13      |    Include-All Information     | [this document] |
   |                |             Source             |                 |
   +----------------+--------------------------------+-----------------+
   |     TBD14      |   Exclude Information Source   | [this document] |
   +----------------+--------------------------------+-----------------+
   |     TBD15      |   TOPOLOGY-FILTER-CAPABILITY   | [this document] |
   |                |              TLV               |                 |
   +----------------+--------------------------------+-----------------+

                                  Table 2

   IANA is requested to make allocations for Info Source sub-TLV carried
   with the Filtering Rules TLVs, as follows:

             +=======+=====================+=================+
             | Value |       sub-TLV       |    Reference    |
             +=======+=====================+=================+
             | TBD12 | Info Source sub-TLV | [this document] |
             +-------+---------------------+-----------------+

                                  Table 3






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5.3.  PCEP-Error Object

   IANA is requested to make new allocations in the "PCEP-ERROR Object
   Error Types and Values" registry:

   +======================+===============================+===========+
   |      Error-Type      |          Error-Value          | Reference |
   +======================+===============================+===========+
   | 19-Invalid Operation | TBD16 - Protocol ID is absent |   [this   |
   |                      |                               | document] |
   +----------------------+-------------------------------+-----------+

                                 Table 4

5.4.  Flags in the TOPOLOGY-FILTER-CAPABILITY TLV

   IANA is requested to create a new registry called "Flags in TOPOLOGY-
   FILTER-CAPABILITY TLV" to manage the Flag field.  New values are to
   be assigned by "IETF review" [RFC8126].

     +=====+=======================================+=================+
     | Bit |              Description              |    Reference    |
     +=====+=======================================+=================+
     |  0  | S-flag: Source Protocol ID Capability | [this document] |
     +-----+---------------------------------------+-----------------+
     |  1  |  M-flag: Multi-topology ID Capability | [this document] |
     +-----+---------------------------------------+-----------------+
     |  2  |    A-flag: Algorithm ID Capability    | [this document] |
     +-----+---------------------------------------+-----------------+
     |  3  |      D-flag: Domain ID Capability     | [this document] |
     +-----+---------------------------------------+-----------------+
     |  4  |     P-flag: Provider ID Capability    | [this document] |
     +-----+---------------------------------------+-----------------+
     |  5  |      C-flag: Client ID Capability     | [this document] |
     +-----+---------------------------------------+-----------------+
     |  6  |     T-flag: Topology ID Capability    | [this document] |
     +-----+---------------------------------------+-----------------+
     |  7  |     G-flag: Admin Group Capability    | [this document] |
     +-----+---------------------------------------+-----------------+
     |  8  | I-flag: Information Source Capability | [this document] |
     +-----+---------------------------------------+-----------------+

                                  Table 5








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5.5.  Flags in the Info Source sub-TLV

   IANA is requested to create a new registry called "Flags in Info
   Source sub-TLV" to manage the Flag field.  New values are to be
   assigned by "IETF review" [RFC8126].

       +=====+==================================+=================+
       | Bit |           Description            |    Reference    |
       +=====+==================================+=================+
       |  0  | I-flag: Instance ID is presented | [this document] |
       +-----+----------------------------------+-----------------+
       |  1  |  D-flag: Domain ID is presented  | [this document] |
       +-----+----------------------------------+-----------------+

                                 Table 6

6.  Operational Considerations

   A PCE or PCC implementation MAY allow the topology filter capability
   advertisement supporting the PCEP extensions introduced in this
   document.  All manageability and operational requirements and
   considerations listed in [RFC5440] and [RFC8231], apply to this
   document.

   The PCEP extensions defined in this document do not impose any new
   requirements on other protocols but rely on the topology information
   from IGP, BGP-LS or YANG data model.

   A PCEP implementation supporting this document SHOULD allow the
   operator to view the topology filter capability defined in this
   document.  and take the topology constraints into account during the
   path computation especially the topology filtering rules which is
   defined in [I-D.ietf-teas-yang-topology-filter].

   The PCEP YANG module is defined in [I-D.ietf-pce-pcep-yang].  In
   future, this YANG module should be extended or augmented to provide
   the additional information relating to topology filter.

7.  Security Considerations

   This document defines a new Topology Filter Object, which do not
   introduce any new security considerations beyond those already listed
   in [RFC4655], [RFC5440], [RFC8231], [RFC8685] and
   [I-D.ietf-pce-sid-algo].

   The security considerations described in [RFC8795] and
   [I-D.ietf-teas-yang-topology-filter] apply to the topology filter
   described in this document as well.



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8.  Acknowledgements

   The authors would like to thank Dhruv Dhody, Andrew Stone and Samuel
   Sidor for their review, suggestions and comments to this document.

9.  References

9.1.  Infomative References

   [I-D.ietf-pce-pcep-yang]
              Dhody, D., Beeram, V. P., Hardwick, J., and J. Tantsura,
              "A YANG Data Model for Path Computation Element
              Communications Protocol (PCEP)", Work in Progress,
              Internet-Draft, draft-ietf-pce-pcep-yang-30, 26 January
              2025, <https://datatracker.ietf.org/doc/html/draft-ietf-
              pce-pcep-yang-30>.

   [I-D.ietf-teas-ns-ip-mpls]
              Saad, T., Beeram, V. P., Dong, J., Halpern, J. M., and S.
              Peng, "Realizing Network Slices in IP/MPLS Networks", Work
              in Progress, Internet-Draft, draft-ietf-teas-ns-ip-mpls-
              07, 28 February 2026,
              <https://datatracker.ietf.org/doc/html/draft-ietf-teas-ns-
              ip-mpls-07>.

   [RFC3209]  Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
              and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
              Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001,
              <https://www.rfc-editor.org/info/rfc3209>.

   [RFC9543]  Farrel, A., Ed., Drake, J., Ed., Rokui, R., Homma, S.,
              Makhijani, K., Contreras, L., and J. Tantsura, "A
              Framework for Network Slices in Networks Built from IETF
              Technologies", RFC 9543, DOI 10.17487/RFC9543, March 2024,
              <https://www.rfc-editor.org/info/rfc9543>.

9.2.  Normative References

   [I-D.ietf-pce-pcep-nrp]
              Dong, J., Fang, S., Xiong, Q., Peng, S., Han, L., Wang,
              M., Beeram, V. P., and T. Saad, "Path Computation Element
              Communication Protocol (PCEP) Extensions for Network
              Resource Partition (NRP)", Work in Progress, Internet-
              Draft, draft-ietf-pce-pcep-nrp-00, 6 November 2025,
              <https://datatracker.ietf.org/doc/html/draft-ietf-pce-
              pcep-nrp-00>.





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   [I-D.ietf-pce-sid-algo]
              Sidor, S., Rose, Z., Peng, S., Peng, S., and A. Stone,
              "Carrying SR-Algorithm in Path Computation Element
              Communication Protocol (PCEP)", Work in Progress,
              Internet-Draft, draft-ietf-pce-sid-algo-29, 15 October
              2025, <https://datatracker.ietf.org/doc/html/draft-ietf-
              pce-sid-algo-29>.

   [I-D.ietf-teas-yang-topology-filter]
              Beeram, V. P., Saad, T., Gandhi, R., and X. Liu, "YANG
              Data Model for Topology Filter", Work in Progress,
              Internet-Draft, draft-ietf-teas-yang-topology-filter-02,
              19 October 2025, <https://datatracker.ietf.org/doc/html/
              draft-ietf-teas-yang-topology-filter-02>.

   [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>.

   [RFC3630]  Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
              (TE) Extensions to OSPF Version 2", RFC 3630,
              DOI 10.17487/RFC3630, September 2003,
              <https://www.rfc-editor.org/info/rfc3630>.

   [RFC4655]  Farrel, A., Vasseur, J.-P., and J. Ash, "A Path
              Computation Element (PCE)-Based Architecture", RFC 4655,
              DOI 10.17487/RFC4655, August 2006,
              <https://www.rfc-editor.org/info/rfc4655>.

   [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>.

   [RFC5120]  Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi
              Topology (MT) Routing in Intermediate System to
              Intermediate Systems (IS-ISs)", RFC 5120,
              DOI 10.17487/RFC5120, February 2008,
              <https://www.rfc-editor.org/info/rfc5120>.

   [RFC5307]  Kompella, K., Ed. and Y. Rekhter, Ed., "IS-IS Extensions
              in Support of Generalized Multi-Protocol Label Switching
              (GMPLS)", RFC 5307, DOI 10.17487/RFC5307, October 2008,
              <https://www.rfc-editor.org/info/rfc5307>.






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   [RFC5440]  Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
              Element (PCE) Communication Protocol (PCEP)", RFC 5440,
              DOI 10.17487/RFC5440, March 2009,
              <https://www.rfc-editor.org/info/rfc5440>.

   [RFC7308]  Osborne, E., "Extended Administrative Groups in MPLS
              Traffic Engineering (MPLS-TE)", RFC 7308,
              DOI 10.17487/RFC7308, July 2014,
              <https://www.rfc-editor.org/info/rfc7308>.

   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,
              <https://www.rfc-editor.org/info/rfc8126>.

   [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>.

   [RFC8231]  Crabbe, E., Minei, I., Medved, J., and R. Varga, "Path
              Computation Element Communication Protocol (PCEP)
              Extensions for Stateful PCE", RFC 8231,
              DOI 10.17487/RFC8231, September 2017,
              <https://www.rfc-editor.org/info/rfc8231>.

   [RFC8685]  Zhang, F., Zhao, Q., Gonzalez de Dios, O., Casellas, R.,
              and D. King, "Path Computation Element Communication
              Protocol (PCEP) Extensions for the Hierarchical Path
              Computation Element (H-PCE) Architecture", RFC 8685,
              DOI 10.17487/RFC8685, December 2019,
              <https://www.rfc-editor.org/info/rfc8685>.

   [RFC8776]  Saad, T., Gandhi, R., Liu, X., Beeram, V., and I. Bryskin,
              "Common YANG Data Types for Traffic Engineering",
              RFC 8776, DOI 10.17487/RFC8776, June 2020,
              <https://www.rfc-editor.org/info/rfc8776>.

   [RFC8795]  Liu, X., Bryskin, I., Beeram, V., Saad, T., Shah, H., and
              O. Gonzalez de Dios, "YANG Data Model for Traffic
              Engineering (TE) Topologies", RFC 8795,
              DOI 10.17487/RFC8795, August 2020,
              <https://www.rfc-editor.org/info/rfc8795>.

   [RFC9552]  Talaulikar, K., Ed., "Distribution of Link-State and
              Traffic Engineering Information Using BGP", RFC 9552,
              DOI 10.17487/RFC9552, December 2023,
              <https://www.rfc-editor.org/info/rfc9552>.




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Authors' Addresses

   Quan Xiong
   ZTE Corporation
   China
   Email: xiong.quan@zte.com.cn


   Shaofu Peng
   ZTE Corporation
   No.50 Software Avenue
   Nanjing
   Jiangsu, 210012
   China
   Email: peng.shaofu@zte.com.cn


   Vishnu Pavan Beeram
   Juniper Networks
   Email: vbeeram@juniper.net


   Tarek Saad
   Cisco Systems
   Email: tsaad.net@gmail.com


   Mike Koldychev
   Ciena Corporation
   Email: mkoldych@ciena.com





















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