BIER Working Group R. Chen Internet-Draft ZTE Corporation Intended status: Standards Track Fangwei. Hu Expires: 21 March 2024 Individual Zheng. Zhang Xianxia. Dai ZTE Corporation Mahesh. Sivakumar Juniper networks 18 September 2023 YANG Data Model for BIER Protocol draft-ietf-bier-bier-yang-08 Abstract This document defines a YANG data model that can be used to configure and manage devices supporting Bit Index Explicit Replication"(BIER). The YANG module in this document conforms to the Network Management Datastore Architecture (NMDA). 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 21 March 2024. Copyright Notice Copyright (c) 2023 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/ license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights Chen, et al. Expires 21 March 2024 [Page 1] Internet-Draft BIER YANG September 2023 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 . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 1.3. Tree Diagrams . . . . . . . . . . . . . . . . . . . . . . 3 1.4. Prefixes in Data Node Names . . . . . . . . . . . . . . . 3 2. Design of Data Model . . . . . . . . . . . . . . . . . . . . 4 3. Module Structure . . . . . . . . . . . . . . . . . . . . . . 4 4. Configuration . . . . . . . . . . . . . . . . . . . . . . . . 5 5. IGP Control-Plane Configuration . . . . . . . . . . . . . . . 6 6. Notifications . . . . . . . . . . . . . . . . . . . . . . . . 6 7. YANG Module for BIER . . . . . . . . . . . . . . . . . . . . 7 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 9. Security Considerations . . . . . . . . . . . . . . . . . . . 17 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 17 11. Normative References . . . . . . . . . . . . . . . . . . . . 17 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18 1. Introduction [RFC8279] describes a new architecture for the forwarding of multicast data packets. Known as "Bit Index Explicit Replication"(BIER), that architecture provides optimal forwarding of multicast data packets through a "multicast domain". YANG [RFC7950] is a data modeling language that was introduced to model the configuration and operational state of a device managed using network management protocols such as the Network Configuration Protocol (NETCONF) [RFC6241] or RESTCONF [RFC8040]. YANG is now also being used as a component of other management interfaces, such as command-line interfaces (CLIs). This document defines a YANG data model that can be used to configure and manage devices supporting Bit Index Explicit Replication"(BIER). The YANG module in this document conforms to the Network Management Datastore Architecture (NMDA). Chen, et al. Expires 21 March 2024 [Page 2] Internet-Draft BIER YANG September 2023 1.1. 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. 1.2. Terminology The terminology for describing YANG data models is found in [RFC7950]. The following abbreviations are used in this document and the defined model: BIER: Bit Index Explicit Replication [RFC8279] BFR: Bit Forwarding Router [RFC8279] BIFT: Bit Index Forwarding Table [RFC8279] BSL: BitStringLength [RFC8279] >SI: Set Identifier [RFC8279] IS-IS: Intermediate System-to-Intermediate System OSPF: Open Shortest Path First 1.3. Tree Diagrams Tree diagrams used in this document follow the notation defined in [RFC8340]. 1.4. Prefixes in Data Node Names In this document, names of data nodes, actions, and other data model objects are often used without a prefix, as long as the context clearly indicates the YANG module in which each name is defined. Otherwise, names are prefixed using the standard prefix associated with the corresponding YANG module, as shown in Table 1. Chen, et al. Expires 21 March 2024 [Page 3] Internet-Draft BIER YANG September 2023 +========+=================+===========+ | Prefix | YANG Module | Reference | +========+=================+===========+ | yang | ietf-yang-types | [RFC6991] | +--------+-----------------+-----------+ | inet | ietf-inet-types | [RFC6991] | +--------+-----------------+-----------+ | if | ietf-interfaces | [RFC8343] | +--------+-----------------+-----------+ | rt | ietf-routing | [RFC8349] | +--------+-----------------+-----------+ Table 1: Prefixes and Corresponding YANG Modules 2. Design of Data Model The data model can be used to configure and manage BIER protocol [RFC8279] features. The operational state data and statistics can be retrieved by this model. The protocol-specific notifications are also defined in the model. This model is used to consistently provision the BIER parameters for one or more BIER subdomains across all BFIR/BFR/BFER. This configuration will also be read by BIER enabled IGPs, such as IS-IS [RFC8401] ，OSPFv2 [RFC8444] and OSPFv3[I-D.ietf-bier-ospfv3-extensions] to learn the BIER parameters. In scenarios where the IGP protocol is not used/available, this model defines the writeable BIFT and all BFIR/BFR/BFER can get the BIFT directly from the controller, or by any other ways such as configuration. 3. Module Structure The ietf-bier YANG module augments the routing container in the ietf- routing model [RFC8349] with a BIER container and defines generic BIER configuration and operational state. This module is augmented by modules supporting different data planes. module: ietf-bier augment /rt:routing: +--rw bier +--rw sub-domain* [sub-domain-id address-family] | +--rw sub-domain-id uint8 | +--rw address-family identityref | +--rw bfr-prefix? inet:ip-prefix | +--rw underlay-protocol-type? underlay-protocol-type | +--rw mt-id? uint16 Chen, et al. Expires 21 March 2024 [Page 4] Internet-Draft BIER YANG September 2023 | +--rw bfr-id? uint16 | +--rw bsl? bsl | +--rw igp-algorithm? uint8 | +--rw bier-algorithm? uint8 | +--rw load-balance-num? uint8 | +--rw encapsulation* [bsl encapsulation-type] | +--rw bsl uint16 | +--rw encapsulation-type identityref | +--rw max-si? uint8 | +--rw in-bift-id? | +--rw:(in-bift-id-base) | | +--rw in-bift-id-base? uint32 | +--rw (in-bift-id-encoding) | +--rw in-bift-id-encoding boolean +--rw bift* [bfr-id] +--rw bfr-id bsl +--rw birt-bitstringlength* [bsl] +--rw bsl bsl +--rw bfr-nbr* [bfr-nbr] +--rw bfr-nbr inet:ip-prefix +--rw encapsulation-type? identityref +--rw our-bift-id? +--rw:(out-bift-id) | +--rw out-bift-id? uint32 +--rw:(out-bift-id-encoding) +--rw out-bift-id-encoding boolean notifications: +---n bfr-id-collision | +--ro bfr-id-collisions*[] | +--ro received-bfr-id? uint16 +---n bfr-id-out-of-range | +--ro received-bfr-id? uint16 +---n bfr-zero | +--ro ipv4-bfr-prefix? inet:ipv4-prefix | +--ro ipv6-bfr-prefix? inet:ipv6-prefix +---n sub-domain-id-collision +--ro received-sub-domain-id? uint16 +--ro received-mt-id? uint16 4. Configuration The ietf-bier YANG module augments the routing container in the ietf- routing model [RFC8349] with a BIER container and defines generic BIER configuration. It includes: Chen, et al. Expires 21 March 2024 [Page 5] Internet-Draft BIER YANG September 2023 sub-domain:Defines the relevant BIER information of the BIER subdomain, such as configuring the BIER domain identifier, configuring the BFR prefix in the BIER subdomain, configuring the Underlay protocol for advertising BIER information, etc. It contains two in-bift-id generation methods, one is direct configuration, the other is calculated based on . The leaf "in-bift-id" is the first BIFT-id of the BIFT-id range. The "BIFT-id range" is the set of 20-bit values beginning with the in-bift-id and ending with (in-bift-id + (Max SI)).The leaf "in-bift-id-encoding" is defined as a boolean, used to enable or disable whether to calculate in-bift-id based on < BSL,SD,SI>. bift: Defines the Bit Index Forwarding Table. The grouping "bfr-nbr" is to define the BFR neighbor, and it contains two bift-id generation methods, one is direct configuration, the other is calculated based on < BSL,SD,SI>. The leaf "out-bift-id-encoding" is defined as a boolean, used to enable or disable whether to calculate out-bift-id based on < BSL,SD,SI>. 5. IGP Control-Plane Configuration Support of BIER extensions for a particular IGP control plane is achieved by augmenting routing-protocol configuration with BIER extensions. This augmentation SHOULD be part of the routing-protocol YANG modules as not to create any dependency for implementations to support BIER extensions for all routing protocols. This module defines groupings that SHOULD be used by IGP BIER modules. The "enabled" leaf enables BIER extensions for the routing-protocol instance. The "sub-domain" container controls the routing-protocol instance's advertisement of the relevant BIER information of the BIER subdomain and the processing of received the relevant BIER information of the BIER subdomain. 6. Notifications The model defines the following notifications for BIER. This module defines groupings that SHOULD be used by IGP BIER modules. bfr-id-collision: Raised when control-plane-advertised BFR ID have conflicts. Chen, et al. Expires 21 March 2024 [Page 6] Internet-Draft BIER YANG September 2023 bfr-id-out-of-range: Raised when control-plane-advertised BFR ID is larger than locally configured (bsl * max-si). bfr-zero: Raised when invalid value associated with prefix. sub-domain-id-collision: Raised when control-plane-advertised Sub domain ID have conflicts. 7. YANG Module for BIER file "ietf-bier@2023-09-16.yang" module ietf-bier { yang-version 1.1; namespace "urn:ietf:params:xml:ns:yang:ietf-bier"; prefix "bier"; import ietf-routing{ prefix "rt"; reference "RFC 8349: A YANG Data Model for Routing Management (NMDA Version)"; } import ietf-interfaces{ prefix "if"; reference "RFC 8343: A YANG Data Model for Interface Management"; } import ietf-inet-types{ prefix "inet"; reference "RFC 6991: Common YANG Data Types"; } import ietf-isis{ prefix "isis"; reference "RFC 9130: YANG Data Model for the IS-IS Protocol"; } import ietf-ospf{ prefix "ospf"; reference "RFC 9129: YANG Data Model for the OSPF Protocol"; } organization "IETF BIER(Bit Indexed Explicit Replication) Working Group"; contact "WG Web: <https://datatracker.ietf.org/wg/bier/> WG List: <mailto:bier@ietf.org> Chen, et al. Expires 21 March 2024 [Page 7] Internet-Draft BIER YANG September 2023 WG Chair: Tony Przygienda <mailto:tonysietf@gmail.com> WG Chair: Greg Shepherd <mailto:gjshep@gmail.com> Editor: Ran Chen <mailto:chen.ran@zte.com.cn> Editor: Fangwei Hu <mailto:hu.fangwei@zte.com.cn> Editor: Zheng Zhang <mailto:zhang.zheng@zte.com.cn> Editor: Xianxian Dai <mailto:dai.xianxian@zte.com.cn> Editor: Mahesh Sivakumar <mailto:masivaku@cisco.com> "; description "The YANG module defines a generic configuration model for BIER.; This YANG module conforms to the Network Management Datastore Architecture (NMDA), as described in RFC 8242. 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 (RFC 2119) (RFC 8174) when, and only when, they appear in all capitals, as shown here. Copyright (c) 2022 IETF Trust and the persons identified as authors of the code. All rights reserved. Redistribution and use in source and binary forms, with or without modification, is permitted pursuant to, and subject to the license terms contained in, the Revised BSD License set forth in Section 4.c of the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info). This version of this YANG module is part of RFC XXXX (https://www.rfc-editor.org/info/rfcXXXX); see the RFC itself for full legal notices."; reference "RFC XXXX: YANG Data Model for BIER"; Chen, et al. Expires 21 March 2024 [Page 8] Internet-Draft BIER YANG September 2023 revision 2023-09-12 { description "initial version."; reference "RFC XXXX: YANG Data Model for BIER "; } /* Identities */ identity bier-encapsulation{ description "Base identity for BIER encapsulation."; } identity bier-encapsulation-mpls { base bier-encapsulation; description "This identity represents MPLS encapsulation for bier."; } identity bier-encapsulation-ipv6 { base bier-encapsulation; description "This identity represents ipv6 encapsulation for bier."; } identity bier-encapsulation-ethernet { base bier-encapsulation; description "This identity represents ethernet encapsulation for bier."; } identity address-family { description "Base identity from which identities describing address families are derived."; } identity ipv4 { base address-family; description "This identity represents an IPv4 address family."; } identity ipv6 { base address-family; description "This identity represents an IPv6 address family."; } /* typedef */ Chen, et al. Expires 21 March 2024 [Page 9] Internet-Draft BIER YANG September 2023 typedef underlay-protocol-type { type enumeration { enum IS-IS { description "This BIER subdomains configuration can be read and advertise by BIER enabled IS-IS."; } enum OSPF { description "This BIER subdomains configuration can be read and advertise by BIER enabled OSPF."; } enum BGP { description "This BIER subdomains configuration can be read and advertise by BIER enabled BGP."; } } description "List of the underlay protocol to be supported."; } typedef bsl { type enumeration { enum IS-IS { description "This BIER subdomains configuration can be read and advertise by BIER enabled IS-IS."; } enum OSPF { description "This BIER subdomains configuration can be read and advertise by BIER enabled OSPF."; } enum BGP { description "This BIER subdomains configuration can be read and advertise by BIER enabled BGP."; } } description "list of the underlay protocol to be supported."; } augment "/rt:routing" { description "This augments routing-instance configuration with bier."; Chen, et al. Expires 21 March 2024 [Page 10] Internet-Draft BIER YANG September 2023 container bier{ description "bier subdomain configuration."; list sub-domain { key "sub-domain-id address-family"; description "The parameters of the BIER subdomain. " leaf sub-domain-id { type uint16; description "The bier sub-domain-id"; } leaf address-family { type identityref { base address-family; } mandatory true; description "Address family."; } leaf bfr-prefix { type inet:ip-prefix; description "the bfr prefix."; } leaf underlay-protocol-type { type underlay-protocol-type; description "List of the underlay protocol to be supported.."; } leaf mt-id { type uint16; description "The multi-topology identifier"; } leaf bfr-id { type uint16; description "Configure the unique BFR-id value within the BIER subdomain for the BFIR/BFER device, and BFR doesnot need a BFR-id, but for diagnostics purposes of the IGP, highly recommended to assign one - but beyond max-si*bls."; Chen, et al. Expires 21 March 2024 [Page 11] Internet-Draft BIER YANG September 2023 } leaf bsl { type bsl; description "The length of the bitstring in the BIER encapsulation within the BIER subdomain."; } leaf igp-algorithm { type uint8; default "0"; description "Calculation type value ranges from 0 to 255 both inclusive from the IGP Algorithm Types registry defined under Interior Gateway Protocol (IGP) Parameters IANA registries.If the required calculation type is Shortest Path First, the value 0 SHOULD appear in this field."; } leaf bier-algorithm { type uint8; description "Calculation type value ranges from 0 to 255 both inclusive from the BIER Algorithm registry.Specifies a BIER-specific Algorithm and BIER-specific Constraints used to either modify, enhance, or replace the calculation of underlay paths to reach other BFRs as defined by the IPA value as defined in RFC9272."; } leaf load-balance-num { type uint8; description "The multicast load balance num."; } list encapsulation { key "bsl encapsulation-type"; description "The BIER encapsulation type.When MPLS is used as the transport, the Bit Indexed Forwarding Table (BIFT) is identified by a MPLS Label. When non-MPLS transport is used, the BIFT is identified by a 20bit value."; leaf bsl{ type bsl; description "The length of the bitstring in the BIER encapsulation Chen, et al. Expires 21 March 2024 [Page 12] Internet-Draft BIER YANG September 2023 within the BIER subdomain."; } leaf encapsulation-type { type identityref { base bier-encapsulation; } description "The BIER encapsulation that can be used in either MPLS networks or non-MPLS networks."; } leaf max-si { type uint16; description "Maximum Set Identifier.The SI value in the subdomain is an integer from 0 to max-si."; } container in-bift-id { description "In BIFT-ID specification."; choice in-bift-id { default "in-bift-id-base"; description "Options for specifying in-bift-id"; case in-bift-id-base { leaf in-bift-id-base { type uint32; description "The first BIFT ID value, there are maximum SI+1 BIFT IDs in total as define in RFC8401."; } } case in-bift-id-encoding { leaf in-bift-id-encoding { type boolean; default "false"; description "setting this attribute to 'true' will enable calculation of in-bift-id based on ."; } } } } } } list bift { key "bfr-id"; description "BIER forwarding tabel." Chen, et al. Expires 21 March 2024 [Page 13] Internet-Draft BIER YANG September 2023 leaf bfr-id { type uint16; description "The unique BFR-id value within the BIER subdomain for the BFIR/BFER device."; } list birt-bitstringlength { key "bsl"; description "specify BSL's bfr-nbr, encapsulation-type and out-bift-id in the BIER forwarding tabel."; leaf bsl { type bsl; description "Configure the bitstring length in BIFT in the BIER subdomain"; } list bfr-nbr { key bfr-nbr; description "bfr-nbr."; leaf bfr-nbr { type inet:ip-prefix; description "bfr-nbr."; } leaf encapsulation-type { type identityref { base bier-encapsulation; } description "The BIER encapsulation that can be used in either MPLS networks or non-MPLS networks."; } container out-bift-id { description "Out BIFT-ID specification."; choice out-bift-id { default "out-bift-id"; description "Options for specifying out-bift-id"; case out-bift-id { leaf out-bift-id { type uint32; description "Configure the out-bift-id"; } } Chen, et al. Expires 21 March 2024 [Page 14] Internet-Draft BIER YANG September 2023 case out-bift-id-encoding { leaf out-bift-id-encoding { type boolean; default "false"; description "setting this attribute to 'true' will enable calculation of out-bift-id based on ."; } } } } } } } } } notification bfr-id-collision { description "This notification is sent when BFR-id received from different routers collide."; list bfr-id-collision { description "List of BFR-id that collide."; leaf received-bfr-id { type uint16; description "Value of the BFR-id received."; } } } notification bfr-id-out-of-range { description "This notification is sent when a BFR-id is received that is is larger than locally configured (bsl * max-si). The notification generation must be throttled with at least a 5-second gap between notifications."; leaf received-bfr-id { type uint16; description "Value of the BFR-id received."; } } notification bfr-zero { description "This notification is sent when an invalid value Chen, et al. Expires 21 March 2024 [Page 15] Internet-Draft BIER YANG September 2023 associated with prefix."; leaf ipv4-bfr-prefix { type inet:ipv4-prefix; description "BIER ipv4 bfr prefix"; } leaf ipv6-bfr-prefix{ type inet:ipv6-prefix; description "BIER ipv6 bfr prefix"; } } notification sub-domain-id-collision { description "This notification is sent when sub-domain-id received from different routers collide."; leaf received-sub-domain-id { type uint16; description "Value of the sub-domain-id received."; } leaf received-mt-id{ type uint16; description "Value of the multi-topology ID received.; } } } 8. IANA Considerations This document registers a URI in the "IETF XML Registry" [RFC3688]. Following the format in [RFC3688], the following registration is requested to be made: ID: yang:ietf-bier URI: urn:ietf:params:xml:ns:yang:ietf-bier Registrant Contact: The IESG. XML: N/A, the requested URI is an XML namespace. This document registers YANG modules in the "YANG Module Names"registry [RFC6020]. Chen, et al. Expires 21 March 2024 [Page 16] Internet-Draft BIER YANG September 2023 Name: ietf-bier Maintained by IANA: N Namespace: urn:ietf:params:xml:ns:yang:ietf-bier Prefix: bier Reference: RFC **** 9. Security Considerations TBD. 10. Acknowledgements TBD. 11. Normative References [I-D.ietf-bier-ospfv3-extensions] Psenak, P., Nainar, N. K., and I. Wijnands, "OSPFv3 Extensions for BIER", Work in Progress, Internet-Draft, draft-ietf-bier-ospfv3-extensions-07, 1 December 2022, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, DOI 10.17487/RFC3688, January 2004, . [RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for the Network Configuration Protocol (NETCONF)", RFC 6020, DOI 10.17487/RFC6020, October 2010, . [RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed., and A. Bierman, Ed., "Network Configuration Protocol (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011, . [RFC6991] Schoenwaelder, J., Ed., "Common YANG Data Types", RFC 6991, DOI 10.17487/RFC6991, July 2013, . Chen, et al. Expires 21 March 2024 [Page 17] Internet-Draft BIER YANG September 2023 [RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language", RFC 7950, DOI 10.17487/RFC7950, August 2016, . [RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC8279] Wijnands, IJ., "Multicast Using Bit Index Explicit Replication (BIER)", RFC 8279, DOI 10.17487/RFC8279, November 2017, . [RFC8340] Bjorklund, M., "YANG Tree Diagrams", RFC 8340, DOI 10.17487/RFC8340, March 2018, . [RFC8343] Bjorklund, M., "A YANG Data Model for Interface Management", RFC 8343, DOI 10.17487/RFC8343, March 2018, . [RFC8349] Lhotka, L., Lindem, A., and Y. Qu, "A YANG Data Model for Routing Management (NMDA Version)", RFC 8349, DOI 10.17487/RFC8349, March 2018, . [RFC8401] Ginsberg, L., Przygienda, T., Aldrin, S., and J. Zhang, "Bit Index Explicit Replication (BIER) Support via IS-IS", RFC 8401, DOI 10.17487/RFC8401, June 2018, . [RFC8444] Psenak, P., Wijnands, IJ., Dolganow, A., Przygienda, T., Zhang, J., and S. Aldrin, "OSPFv2 Extensions for Bit Index Explicit Replication (BIER)", RFC 8441, DOI 10.17487/RFC8441, November 2018, . Authors' Addresses Ran Chen ZTE Corporation Nanjing China Email: chen.ran@zte.com.cn Chen, et al. Expires 21 March 2024 [Page 18] Internet-Draft BIER YANG September 2023 Fangwei Hu Individual Shanghai China Email: hufwei@gmail.com Zheng Zhang ZTE Corporation Nanjing China Email: zhang.zheng@zte.com.cn Xianxian Dai ZTE Corporation Nanjing China Email: Dai.xianxian@zte.com.cn Mahesh Sivakumar Juniper networks Sunnyvale, CALIFORNIA 94089, United States Email: sivakumar.mahesh@gmail.com Chen, et al. Expires 21 March 2024 [Page 19]