PCE Q. Xiong Internet-Draft S. Peng Intended status: Standards Track ZTE Corporation Expires: 11 April 2022 V. Beeram T. Saad Juniper Networks M. Koldychev Cisco Systems 8 October 2021 PCEP Extensions for Topology Filter draft-xpbs-pce-topology-filter-00 Abstract This document proposes a set of extensions for PCEP to support the topology filter during path computation. 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 11 April 2022. Copyright Notice Copyright (c) 2021 IETF Trust and the persons identified as the document authors. All rights reserved. Xiong, et al. Expires 11 April 2022 [Page 1] Internet-Draft PCEP Extensions for Topology Filter October 2021 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. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 1.2. Requirements Language . . . . . . . . . . . . . . . . . . 3 2. Topology Filter . . . . . . . . . . . . . . . . . . . . . . . 4 2.1. Topology Reference . . . . . . . . . . . . . . . . . . . 4 2.2. Filters . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. PCEP Extensions . . . . . . . . . . . . . . . . . . . . . . . 4 3.1. TOPOLOGY Object . . . . . . . . . . . . . . . . . . . . . 4 3.1.1. Source Protocol TLV . . . . . . . . . . . . . . . . . 5 3.1.2. Multi-topology TLV . . . . . . . . . . . . . . . . . 6 3.1.3. Area TLV . . . . . . . . . . . . . . . . . . . . . . 6 3.1.4. Algorithm TLV . . . . . . . . . . . . . . . . . . . . 7 3.2. IRO Object . . . . . . . . . . . . . . . . . . . . . . . 7 3.2.1. Link ID . . . . . . . . . . . . . . . . . . . . . . . 7 3.2.2. Admin Group . . . . . . . . . . . . . . . . . . . . . 8 3.2.3. Source Protocol . . . . . . . . . . . . . . . . . . . 8 3.3. XRO Object . . . . . . . . . . . . . . . . . . . . . . . 9 3.3.1. Link ID . . . . . . . . . . . . . . . . . . . . . . . 9 3.3.2. Admin Group . . . . . . . . . . . . . . . . . . . . . 9 3.3.3. Source Protocol . . . . . . . . . . . . . . . . . . . 10 3.4. Procedures . . . . . . . . . . . . . . . . . . . . . . . 11 4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 11 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 5.1. TOPOLOGY Object . . . . . . . . . . . . . . . . . . . . . 11 5.2. IRO Object . . . . . . . . . . . . . . . . . . . . . . . 11 5.3. XRO Object . . . . . . . . . . . . . . . . . . . . . . . 12 6. Security Considerations . . . . . . . . . . . . . . . . . . . 12 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 7.1. Normative References . . . . . . . . . . . . . . . . . . 12 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13 Xiong, et al. Expires 11 April 2022 [Page 2] Internet-Draft PCEP Extensions for Topology Filter October 2021 1. Introduction [RFC5440] describes the Path Computation Element 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 always perform path computation based on the network topology information collected through BGP-LS [RFC7752]. BGP-LS can get multiple link-state data from multiple IGP instance, or multiple virtual topologies from a single IGP instance. It is necessary to restrict the PCE to a sub-topology during path computation. The PCE MUST take the topology constraint into consideration during path computation. The sub-topology may be considered as a TE topology or a specific IGP domain. As defined in draft-bestbar-teas-yang-topology-filter, a topology filter is a data construct that can be applied on either a native topology or a user specified topology. The topology filter can be viewed as a set of filtering rules to construct the sub- topology. The topology filter specifies the topology reference or a set of include-any, include-all and exclude filtering rules. 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], [RFC7752] and [RFC8795]. 1.2. 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 RFC 2119 [RFC2119]. Xiong, et al. Expires 11 April 2022 [Page 3] Internet-Draft PCEP Extensions for Topology Filter October 2021 2. Topology Filter As defined in draft-bestbar-teas-yang-topology-filter, a topology filter is a data construct that can be applied on either a native topology or a user specified topology. The topology filter can be viewed as a set of filtering rules to construct the sub-topology. The topology filter specifies the topology reference or a set of include-any, include-all and exclude filtering rules. 2.1. Topology Reference The topology reference indicates the topology on which the existing referenced filtering rules need to be applied. The referenced topology could be a predefined TE topology or a specific IGP domain. As defined in RFC7752, the IGP domain has a unique IGP representation by using the combination of Area-ID, Router-ID, Protocol-ID, Multi- Topology ID, and Instance-ID. This document defines TOPOLOGY object and new TLVs for the topology filiter such as Source Protocol TLV, Multi-Topology ID, Area-ID and Algorithm TLV. 2.2. Filters The topology filters carries a list of filters. Each filter specifies a set of include-any, include-all and exclude filtering rules that can be applied on the native topology. The filtering rules specify the a set of constraints on the topology, that are to be used to compute path at PCE. This document proposes a set of extensions for IRO and XRO objext and defines new subobjects such as Link ID, Link affinity and Source Protocol. 3. PCEP Extensions 3.1. TOPOLOGY Object This document defines a new TOPOLOGY object to carry the topology filter. The TOPOLOGY object is optional and specifies the sub-topology to be taken into account by the PCE during path computation. The TOPOLOGY object can be carried within a PCReq message, or a PCRep message in case of unsuccessful path computation. TOPOLOGY Object-Class is TBD1. TOPOLOGY Object-Type is TBD2. The format of the TOPOLOGY object body is: Xiong, et al. Expires 11 April 2022 [Page 4] Internet-Draft PCEP Extensions for Topology Filter October 2021 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 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 section. 3.1.1. Source Protocol TLV The Source Protocol TLV is optional and is defined to carry the protocol ID and Instance ID. The format of the Source Protocol 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=TBD3 | Length=12 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Protocol-ID | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Instance-ID | | (64 bits) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: Source Protocol TLV The code point for the TLV type is TBD3. The TLV length is 12 octets. Xiong, et al. Expires 11 April 2022 [Page 5] Internet-Draft PCEP Extensions for Topology Filter October 2021 Protocol-ID (8 bits): defined in [RFC7752] section 3.2. IS-IS [RFC8202] and OSPF [RFC6549] MAY run multiple routing protocol instances identified by the Protocol-ID over the same link. Reserved (24 bits): This field MUST be set to zero on transmission and MUST be ignored on receipt. Instance-ID (64 bits): defined in [RFC7752] section 3.2. 3.1.2. Multi-topology TLV The Multi-topology TLV is optional and is defined to carry the multi- topology ID. The format of the Multi-topology 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 TLV The code point for the sub-TLV type is TBD4. The sub-TLV length is 4 octets. Multi-Topology ID (12 bits): Semantics of the IS-IS MT-ID are defined in Section 7.2 of [RFC5120]. Semantics of the OSPF MT-ID are defined in Section 3.7 of [RFC4915]. As defined in section 3.2.1.5 of [RFC7752], if the value is derived from OSPF, then the upper 9 bits MUST be set to 0. Bits R are reserved and SHOULD be set to 0 when originated and ignored on receipt. Reserved (16 bits): This field MUST be set to zero on transmission and MUST be ignored on receipt. 3.1.3. Area TLV The Area TLV is optional and is defined to carry the Area ID. The format of the Area TLV is : Xiong, et al. Expires 11 April 2022 [Page 6] Internet-Draft PCEP Extensions for Topology Filter October 2021 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // Area ID (variable) // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 4: Area TLV The code point for the TLV type is TBD3. The TLV length is variable. Area-ID: Area identifier as defined in RFC7752. 3.1.4. Algorithm TLV The Algorithm TLV is optional and is defined to carry the Algorithm ID. The Algorithm 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 draft-tokar-pce-sid-algo-04 section 3.4. 3.2. IRO Object As per [RFC5440], IRO can be used to specify that the computed path needs to traverse a set of specified network elements or abstract nodes. This document proposed a set of extensions for topology filter. 3.2.1. Link ID The Link ID is used to include the link that is used during the path calculation. The Link ID subobject is defined: 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 | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Link ID (4 bytes) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 5: Link ID subobject in IRO Xiong, et al. Expires 11 April 2022 [Page 7] Internet-Draft PCEP Extensions for Topology Filter October 2021 The code point for the TLV type is TBD6. The TLV length is 12 octets. Link ID (32bits ): defined in IS-IS RFC5307 and OSPF RFC3630. 3.2.2. Admin Group The Admin Group is used to include 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=TBD7 | Length | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Extended Admin Group | +- -+ | ... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 6: Admin Group subobject in IRO The code point for the TLV type is TBD7. The TLV length is variable. Extended Administrative Group: Extended Administrative Group as defined in [RFC7308]. 3.2.3. Source Protocol The format of the Source Protocol subobject 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=TBD8 | Length | Reserved | Protocol-ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Instance-ID | | (64 bits) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 7: Source Protocol subobject in IRO The code point for the TLV type is TBD8. The TLV length is 12 octets. Xiong, et al. Expires 11 April 2022 [Page 8] Internet-Draft PCEP Extensions for Topology Filter October 2021 Protocol-ID (8 bits): defined in [RFC7752] section 3.2. IS-IS [RFC8202] and OSPF [RFC6549] MAY run multiple routing protocol instances identified by the Protocol-ID over the same link. Reserved (24 bits): This field MUST be set to zero on transmission and MUST be ignored on receipt. Instance-ID (64 bits): defined in [RFC7752] section 3.2. 3.3. XRO Object As per [RFC5521], XRO is an optional object used to specify exclusion of certain abstract nodes or resources from the whole path. This document proposed a set of extensions for topology filter. 3.3.1. Link ID The Link ID is used to exclude the link that is used during the path calculation. The Link ID subobject is defined: 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 | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Link ID (4 bytes) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 8: Link ID subobject in XRO The code point for the TLV type is TBD9. The TLV length is 12 octets. Link ID (32bits ): defined in IS-IS RFC5307 and OSPF RFC3630. 3.3.2. Admin Group The Admin Group is used to exclude the links that is used during the path calculation. Xiong, et al. Expires 11 April 2022 [Page 9] Internet-Draft PCEP Extensions for Topology Filter October 2021 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 | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Extended Admin Group | +- -+ | ... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 9: Admin Group subobject in XRO The code point for the TLV type is TBD10. The TLV length is variable. Extended Administrative Group: Extended Administrative Group as defined in [RFC7308]. 3.3.3. Source Protocol The format of the Source Protocol subobject 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=TBD11 | Length | Reserved | Protocol-ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Instance-ID | | (64 bits) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 10: Source Protocol subobject in XRO The code point for the TLV type is TBD11. The TLV length is 12 octets. Protocol-ID (8 bits): defined in [RFC7752] section 3.2. IS-IS [RFC8202] and OSPF [RFC6549] MAY run multiple routing protocol instances identified by the Protocol-ID over the same link. Reserved (24 bits): This field MUST be set to zero on transmission and MUST be ignored on receipt. Instance-ID (64 bits): defined in [RFC7752] section 3.2. Xiong, et al. Expires 11 April 2022 [Page 10] Internet-Draft PCEP Extensions for Topology Filter October 2021 3.4. Procedures A PCC MAY insert a TOPOLOGY object to indicate the sub-topology of an IGP domain that MUST be considered by the PCE. The PCE will perform path computation based on the sub-topology identified by the topology filter rules that can be applied on either the native topology or a user specified topology. The absence of the TLVs related topology reference indicates that the filtering rules are to be applied on the native topology. 4. Acknowledgements TBA 5. IANA Considerations 5.1. TOPOLOGY Object IANA is requested to make allocations for Topology Object from the registry, as follows: +======+=====================+==========================+ | Type | TLV | Reference | +======+=====================+==========================+ | TBD1 | Source Protocol TLV | [this document] | +------+---------------------+--------------------------+ | TBD2 | Multi-topology TLV | [this document] | +------+---------------------+--------------------------+ | TBD3 | Area TLV | [this document] | +------+---------------------+--------------------------+ | TBD4 | Algorithm TLV | draft-tokar-pce-sid-algo | +------+---------------------+--------------------------+ Table 1: TLVs for Topology Object 5.2. IRO Object IANA is requested to make allocations for IRO Object from the registry, as follows: Xiong, et al. Expires 11 April 2022 [Page 11] Internet-Draft PCEP Extensions for Topology Filter October 2021 +======+=================+=================+ | Type | Subobject | Reference | +======+=================+=================+ | TBD5 | Link ID | [this document] | +------+-----------------+-----------------+ | TBD6 | Admin Group | [this document] | +------+-----------------+-----------------+ | TBD7 | Source Protocol | [this document] | +------+-----------------+-----------------+ Table 2: Subobjects for IRO Object 5.3. XRO Object IANA is requested to make allocations for XRO Object from the registry, as follows: +=======+=================+=================+ | Type | Subobject | Reference | +=======+=================+=================+ | TBD8 | Link ID | [this document] | +-------+-----------------+-----------------+ | TBD9 | Admin Group | [this document] | +-------+-----------------+-----------------+ | TBD10 | Source Protocol | [this document] | +-------+-----------------+-----------------+ Table 3: Subobjects for XRO Object 6. Security Considerations TBA 7. References 7.1. Normative References [draft-ietf-lsr-flex-algo] "IGP Flexible Algorithm", July 2021, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC4655] "A Path Computation Element (PCE)-Based Architecture", August 2006, . Xiong, et al. Expires 11 April 2022 [Page 12] Internet-Draft PCEP Extensions for Topology Filter October 2021 [RFC4915] "Multi-Topology (MT) Routing in OSPF", June 2007, . [RFC5120] "M-ISIS: Multi Topology (MT) Routing in Intermediate System to Intermediate Systems (IS-ISs)", February 2008, . [RFC5440] "Path Computation Element (PCE) Communication Protocol (PCEP)", March 2009, . [RFC6549] "OSPFv2 Multi-Instance Extensions", March 2012, . [RFC7752] "North-Bound Distribution of Link-State and Traffic Engineering (TE) Information Using BGP", March 2016, . [RFC8174] "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", May 2017, . [RFC8202] "IS-IS Multi-Instance", June 2017, . [RFC8231] "Path Computation Element Communication Protocol (PCEP) Extensions for Stateful PCE", September 2017, . [RFC8795] "YANG Data Model for Traffic Engineering (TE) Topologies", August 2020, . 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 Xiong, et al. Expires 11 April 2022 [Page 13] Internet-Draft PCEP Extensions for Topology Filter October 2021 Email: peng.shaofu@zte.com.cn Vishnu Pavan Beeram Juniper Networks Email: vbeeram@juniper.net Tarek Saad Juniper Networks Email: tsaad@juniper.net Mike Koldychev Cisco Systems Canada Email: mkoldych@cisco.com Xiong, et al. Expires 11 April 2022 [Page 14]