Introducing Resource Awareness to SR Segments
draft-ietf-spring-resource-aware-segments-02

Document Type Active Internet-Draft (spring WG)
Authors Jie Dong  , Stewart Bryant  , Takuya Miyasaka  , Yongqing Zhu  , Fengwei Qin  , Zhenqiang Li  , Francois Clad 
Last updated 2021-02-22
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SPRING Working Group                                             J. Dong
Internet-Draft                                       Huawei Technologies
Intended status: Standards Track                               S. Bryant
Expires: August 26, 2021                          Futurewei Technologies
                                                             T. Miyasaka
                                                        KDDI Corporation
                                                                  Y. Zhu
                                                           China Telecom
                                                                  F. Qin
                                                                   Z. Li
                                                            China Mobile
                                                                 F. Clad
                                                           Cisco Systems
                                                       February 22, 2021

             Introducing Resource Awareness to SR Segments
              draft-ietf-spring-resource-aware-segments-02

Abstract

   This document describes the mechanism to associate network resource
   attributes to Segment Routing Identifiers (SIDs).  Such SIDs are
   referred to as resource-aware SIDs in this document.  The resource-
   aware SIDs retain their original forwarding semantics, but with the
   additional semantics to identify the set of network resources
   available for the packet processing action.  The resource-aware SIDs
   can therefore be used to build SR paths or virtual networks with a
   set of reserved network resources.  The proposed mechanism is
   applicable to both segment routing with MPLS data plane (SR-MPLS) and
   segment routing with IPv6 data plane (SRv6).

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
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   This Internet-Draft will expire on August 26, 2021.

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Copyright Notice

   Copyright (c) 2021 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
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  Segments with Resource Awareness  . . . . . . . . . . . . . .   3
     2.1.  SR-MPLS . . . . . . . . . . . . . . . . . . . . . . . . .   4
     2.2.  SRv6  . . . . . . . . . . . . . . . . . . . . . . . . . .   6
   3.  Control Plane Considerations  . . . . . . . . . . . . . . . .   7
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   6.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .   9
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   9
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   9
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   9
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  12

1.  Introduction

   Segment Routing (SR) [RFC8402] specifies a mechanism to steer packets
   through an ordered list of segments.  A segment is referred to by its
   Segment Identifier (SID).  With SR, explicit source routing can be
   achieved without introducing per-path state into the network.
   Compared with RSVP-TE [RFC3209], currently SR does not have the
   capability of reserving network resources or identifying a set of
   network resources reserved for individual services or customers.
   Although a centralized controller can have a global view of network
   state and can provision different services using different SR paths,
   in data packet forwarding it still relies on traditional DiffServ QoS
   mechanism [RFC2474] [RFC2475] to provide coarse-grained traffic
   differentiation in the network.  While such kind of mechanism may be
   sufficient for some types of services, some customers or services may
   require a set of dedicated network resources to be allocated in the

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   network to achieve resource isolation from other customers/services
   in the same network.  Also note the number of such customers or
   services can be larger than the number of traffic classes available
   with DiffServ QoS.

   This document extends the SR paradigm without the need of defining
   new SID types by associating SIDs with network resource attributes.
   These resource-aware SIDs retain their original functionality, with
   the additional semantics of identifying the set of network resources
   available for the packet processing action.  One typical type of the
   network resource is the link bandwidth and the associated
   buffer/queuing/scheduling resources, but it is also possible to
   associate SR SIDs with other types of resources (e.g., processing or
   storage resources).  On a particular network segment, multiple
   resource-aware SIDs can be allocated, each of which represents a
   subset of network resources allocated in the network to meet the
   requirement of individual customers or services.  The allocation of
   network resources on network segments can be done either via local
   configuration or via a centralized controller.  Other approaches are
   possible such as use of a control protocol signaling, but they are
   for further study.  Each set of network resources can be associated
   with one or multiple resource-aware SIDs.  These resource-aware SIDs
   can be used to build SR paths with a set of reserved network
   resources, which can be used to carry service traffic which requires
   dedicated network resources along the path.  The resource-aware SIDs
   can also be used to build SR based virtual networks for services with
   the required network topology and resource attributes.  The proposed
   mechanism is applicable to SR with both MPLS data plane (SR-MPLS) and
   IPv6 data plane (SRv6).

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
   BCP14 RFC 2119 [RFC2119] RFC 8174 [RFC8174] when, and only when, they
   appear in all capitals, as shown here.

2.  Segments with Resource Awareness

   In segment routing architecture [RFC8402], several types of segments
   are defined to represent either topological or service instructions.
   A topological segment can be a node segment or an adjacency segment.
   A service segment may be associated with specific service functions
   for service chaining purpose.  This document introduces additional
   resource semantics to these existing types of SIDs, so that the SIDs
   can be used to identify the topology or service functions, and also

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   the set of network resources allocated on the network segments for
   packet processing.

   This section describes the mechanisms of using SR SIDs to identify
   the additional resource information associated with SR paths or
   virtual networks based on the two SR data plane instantiations: SR-
   MPLS and SRv6.  The mechanisms to identify the forwarding path or
   network topology with SIDs as defined in [RFC8402] can be reused, and
   the control plane can be based on [RFC4915], [RFC5120] and
   [I-D.ietf-lsr-flex-algo].

2.1.  SR-MPLS

   As specified in [RFC8402], an IGP Adjacency Segment (Adj-SID) is an
   SR segment attached to a unidirectional adjacency or a set of
   unidirectional adjacencies.  An IGP Prefix Segment (Prefix-SID) is an
   SR segment attached to an IGP prefix, which identifies an instruction
   to forward the packet along the path computed using the routing
   algorithm in the associated topology.  An IGP node segment is an IGP-
   Prefix segment that identifies a specific router (e.g., a loopback).
   As described in [I-D.ietf-spring-segment-routing-central-epe] and
   [I-D.ietf-idr-bgpls-segment-routing-epe], BGP PeerAdj SID is used as
   an instruction to steer over a local interface towards a specific
   peer node in a peering Autonomous System (AS).  These types of SIDs
   can be extended to represent both topological instructions and the
   set of network resources allocated for packet processing following
   the instruction.  The MPLS instantiation of Segment Routing is
   specified in [RFC8660].

   A resource-aware Adj-SID represents a subset of the resources (e.g.
   bandwidth and the associated buffer/queuing/scheduling resources) of
   a given link, thus each resource-aware Adj-SID is associated with its
   own set of TE attributes.

   For one IGP link, multiple resource-aware Adj-SIDs SHOULD be
   allocated, each of which is associated with a subset of the link
   resources allocated on the link.  For one inter-domain link, multiple
   BGP PeerAdj SIDs MAY be allocated, each of which is associated with a
   subset of the link resources allocated on the inter-domain link.  The
   resource-aware Adj-SIDs MAY be associated with a specific network
   topology and/or algorithm, so that it is used only for resource-aware
   SR paths computed within the topology and/or algorithm.

   Note this per-segment resource allocation complies to the SR
   paradigm, which avoids introducing per-path state into the network.
   Several approaches can be used to partition the link resource, such
   as [FLEXE], Layer-2 logical sub-interfaces, dedicated queues, etc.

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   The detailed mechanism of link resource partitioning is out of scope
   of this document.

   A resource-aware Prefix-SID is associated with a network topology
   and/or algorithm in which the attached node participates, and in
   addition, a resource-aware prefix-SID is associated with a set of
   network resources (e.g. bandwidth and the associated buffer/queuing/
   scheduling resources) allocated on each node and link participating
   in the same topology and/or algorithm.  Such set of network resources
   can be used for forwarding packets with this resource-aware prefix-
   SID along the paths computed in the associated topology and/or
   algorithm.

   Although it is possible that each resource-aware prefix-SID is
   associated with a set of dedicated resources in the network, this
   implies the overhead with per-prefix resource reservation in both
   control plane signaling and data plane states, and if network
   resources are allocated for one prefix on all the possible paths, it
   is likely some resources will be wasted.  A practical approach is
   that a common set of network resources are allocated by each network
   node and link participating in a topology and/or algorithm, and are
   associated with a group of resource-aware prefix-SIDs of the same
   topology and/or algorithm.  Such a common set of network resources
   constitutes a resource group.  For a given <topology, algorithm>
   tuple, there can be one or multiple resource groups, the resource
   groups which are associated with the same <topology, algorithm> tuple
   shares the SPF computation result.

   This helps to reduce the dynamics in per-prefix resource allocation
   and adjustment, so that the network resource can be allocated based
   on planning and does not have to rely on dynamic signaling.  While
   when the set of nodes and links participate in a <topology,
   algorithm> tuple changes, the set of network resources allocated on
   specific nodes and links may need to be adjusted.  This means that
   the resources allocated to resource-aware Adj-SIDs on those links may
   have to be adjusted and new TE metrics for the associated Adj-SIDs
   re-advertised.

   For one IGP prefix, multiple resource-aware prefix-SIDs SHOULD be
   allocated.  Each resource-aware prefix-SID can be associated with a
   unique <topology, algorithm> tuple, in this case different <topology,
   algorithm> tuples can be used to distinguish the resource-aware
   prefix-SIDs for the same prefix.  In another case, for one IGP
   prefix, multiple resource-aware prefix-SIDs can be associated with
   the same <topology, algorithm> tuple, then an additional
   distinguisher needs to be introduced to distinguish different
   resource-aware prefix-SIDs associated with the same <topology,
   algorithm> but different groups of network resources.

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   A group of resource-aware Adj-SID and resource-aware Prefix-SIDs can
   be used to construct the SID lists to steer the traffic along the
   explicit paths (either strict or loose) and be processed using the
   set of network resources identified by the SIDs.

   In data packet forwarding, each resource-aware Adj-SID identifies
   both the next-hop and the set of resources used for packet processing
   on the outgoing interface.  Each resource-aware Prefix-SID identifies
   a path to the node which the prefix is attached to, and the common
   set of network resources used for packet forwarding on network nodes
   along the path.  The transit nodes determine the next-hop of the
   packet and the set of associated local resources based on the
   resource-aware prefix-SID, then forward the packet to the next-hop
   using the set of local resources.

   When the set of network resources allocated on the egress node also
   needs to be determined, It is RECOMMENDED that Penultimate Hop
   Popping (PHP) [RFC3031] be disabled, or the inner service label is
   used to infer the set of resources to be used for packet processing
   on the egress node of the SR path.

   This mechanism requires to allocate additional prefix-SIDs or adj-
   SIDs for network segments to identify different set of network
   resources.  As the number of resource groups increases, the number of
   SIDs would increase accordingly, while it should be noted that there
   is no per-path state introduced into the network.

2.2.  SRv6

   As specified in [I-D.ietf-spring-srv6-network-programming], an SRv6
   Segment Identifier (SID) is a 128-bit value which consists of a
   locator (LOC) and a function (FUNCT), optionally it may also contain
   additional arguments (ARG) immediately after the FUNCT.  The Locator
   part of the SID is routable and leads to the node which instantiates
   that SID, which means the Locator can be parsed by all nodes in the
   network.  The FUNCT part of the SID is an opaque identification of a
   local function bound to the SID, and the ARG bits of the SID can be
   used to encode additional information for the processing of the
   behavoir bound to the SID.  The FUNCT and ARG parts can only be
   parsed by the node which instantiates the SRv6 SID.

   For one SRv6 node, multiple resource-aware SRv6 LOCs SHOULD be
   allocated.  A resource-aware LOC is associated with a network
   topology and/or algorithm in which the node participates, and in
   addition, a resource-aware LOC is associated with a set of local
   resources (e.g.  bandwidth, processing and storage resources) on each
   node participating in the same topology and/or algorithm.  Such set
   of network resources are used to forward the packets with SIDs which

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   has the resource-aware LOC as its prefix, along the path computed
   with the associated topology and/or algorithm.  Similar to the
   resource-aware prefix-SIDs in SR-MPLS, a practical approach is that a
   common set of network resources are allocated by each network node
   and link participating in a topology and/or algorithm, and are
   associated with a group of resource-aware LOC of the same topology
   and/or algorithm.

   For one IGP link, the resource-aware SRv6 End.X SIDs are used to
   identify different set of link resources allocated.  Each resource-
   aware End.X SID SHOULD use a resource-aware LOC as its prefix.  SRv6
   SIDs for other types of functions MAY also be assigned as resource-
   aware SIDs, which can identify the set of network resources allocated
   by the node for executing the function.

   A group of resource-aware SRv6 SIDs can be used to construct the SID
   lists to steer the traffic along the explicit paths (either strict or
   loose) and be processed using the set of network resources identified
   by the SRv6 SIDs and Locators.

   In data packet forwarding, each resource-aware End.X SID identifies
   both the next-hop and the set of resources used for packet processing
   on the outgoing interface.  Each resource-aware Locator identifies
   the path to the node which the Locator is assigned to, and the set of
   network resources used for packet forwarding on network nodes along
   the path.  The transit nodes determine the next-hop of the packet and
   the set of associated local resources based on the resource-aware
   Locator, then forward the packet to the next-hop using the set of
   local resources.

   This mechanism requires to allocate additional SRv6 Locators and SIDs
   for network segments to identify different set of network resources.
   As the number of resource groups increases, the number of SRv6
   Locators and SIDs would increase accordingly, while it should be
   noted that there is no per-path state introduced into the network.

3.  Control Plane Considerations

   The mechanism described in this document makes use of a centralized
   controller to collect the information about the network
   (configuration, state, routing databases, etc.) as well as the
   service information (traffic matrix, performance statistics, etc.)
   for the planning of network resources based on service requirement.
   Then the centralized controller instructs the network nodes to
   allocate the network resources and associate the resources with the
   resource-aware SIDs.  The resource-aware SIDs can be either
   explicitly provisioned by the controller, or dynamically allocated by
   network nodes then reported to the controller.  The controller is

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   also responsible for the centralized computation and optimization of
   the SR paths with the topology, algorithm and network resource
   constraints.  The interaction between the controller and the network
   nodes can be based on PCEP [RFC5440], Netconf/YANG [RFC6241]
   [RFC7950] and BGP-LS [RFC7752].  In some scenarios, extensions to
   some of these protocols is needed, which are out of the scope of this
   document and will be specified in separate documents.  In some cases,
   a centralized controller may not be used, but this would complicate
   the operations and planning therefore not suggested.

   The distributed control plane is complementary to the centralized
   controller.  A distributed control plane can be used for the
   collection and distribution of the network topology and resource
   information associated with SIDs among network nodes, then some of
   the nodes can distribute the collected information to the centralized
   controller.  Distributed route computation for services with topology
   and/or resource constraints may also be needed on network nodes.  The
   distributed control plane may be based on [RFC4915], [RFC5120],
   [I-D.ietf-lsr-flex-algo] or the combination of some of them with
   necessary extensions.

   On network nodes, the support for a resource group and the
   information to associate packets with that resource group needs to be
   advertised in the control plane, so that all nodes have a consistent
   view of the resource group.  Given that resource management is a
   central function, the knowledge of the exact resources provided to a
   resource group needs to be known accurately by the relevant central
   control components (e.g.  PCE) and the network nodes.  This may be
   done by configuration, alternative protocols, or by advertisements in
   the IGP for collection by BGP-LS.  If there are related link
   advertisements, then consistency must be assured across that set of
   advertisements.  To advertise its support for a given resource group,
   a node would advertise the identifier of the resource group, the
   associated topology and algorithm, and potentially a set of TE
   metrics representing the common resources allocated to it.  The
   details will be described in a separate document.

4.  IANA Considerations

   This document makes no request of IANA.

   Note to RFC Editor: this section may be removed on publication as an
   RFC.

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5.  Security Considerations

   The security considerations of segment routing are applicable to this
   document.

   The Resource-aware SIDs may be used for provisioning of SR paths or
   virtual networks to carry traffic with latency as one of the SLA
   parameters.  By disrupting the latency of such traffic an attack can
   be directly targeted at the customer application, or can be targeted
   at the network operator by causing them to violate their SLA,
   triggering commercial consequences.  Dynamic attacks of this sort are
   not something that networks have traditionally guarded against, and
   networking techniques need to be developed to defend against this
   type of attack.  By rigorously policing ingress traffic and carefully
   provisioning the resources provided to such services, this type of
   attack can be prevented.  However care needs to be taken when
   providing shared resources, and when the network needs to be
   reconfigured as part of ongoing maintenance or in response to a
   failure.

   The details of the underlay network MUST NOT be exposed to third
   parties, to prevent attacks aimed at exploiting a shared resource.

6.  Contributors

   Zhenbin Li
   Email: lizhenbin@huawei.com

   Zhibo Hu
   Email: huzhibo@huawei.com

   Joel Halpern
   Email: jmh@joelhalpern.com

7.  Acknowledgements

   The authors would like to thank Mach Chen, Stefano Previdi, Charlie
   Perkins, Bruno Decraene, Loa Andersson, Alexander Vainshtein and John
   Drake for the valuable discussion and suggestions to this document.

8.  References

8.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

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   [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>.

   [RFC8402]  Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
              Decraene, B., Litkowski, S., and R. Shakir, "Segment
              Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
              July 2018, <https://www.rfc-editor.org/info/rfc8402>.

   [RFC8660]  Bashandy, A., Ed., Filsfils, C., Ed., Previdi, S.,
              Decraene, B., Litkowski, S., and R. Shakir, "Segment
              Routing with the MPLS Data Plane", RFC 8660,
              DOI 10.17487/RFC8660, December 2019,
              <https://www.rfc-editor.org/info/rfc8660>.

8.2.  Informative References

   [FLEXE]    "Flex Ethernet Implementation Agreement", March 2016,
              <http://www.oiforum.com/wp-content/uploads/OIF-FLEXE-
              01.0.pdf>.

   [I-D.ietf-idr-bgpls-segment-routing-epe]
              Previdi, S., Talaulikar, K., Filsfils, C., Patel, K., Ray,
              S., and J. Dong, "BGP-LS extensions for Segment Routing
              BGP Egress Peer Engineering", draft-ietf-idr-bgpls-
              segment-routing-epe-19 (work in progress), May 2019.

   [I-D.ietf-lsr-flex-algo]
              Psenak, P., Hegde, S., Filsfils, C., Talaulikar, K., and
              A. Gulko, "IGP Flexible Algorithm", draft-ietf-lsr-flex-
              algo-13 (work in progress), October 2020.

   [I-D.ietf-spring-segment-routing-central-epe]
              Filsfils, C., Previdi, S., Dawra, G., Aries, E., and D.
              Afanasiev, "Segment Routing Centralized BGP Egress Peer
              Engineering", draft-ietf-spring-segment-routing-central-
              epe-10 (work in progress), December 2017.

   [I-D.ietf-spring-segment-routing-policy]
              Filsfils, C., Talaulikar, K., Voyer, D., Bogdanov, A., and
              P. Mattes, "Segment Routing Policy Architecture", draft-
              ietf-spring-segment-routing-policy-09 (work in progress),
              November 2020.

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   [I-D.ietf-spring-srv6-network-programming]
              Filsfils, C., Camarillo, P., Leddy, J., Voyer, D.,
              Matsushima, S., and Z. Li, "SRv6 Network Programming",
              draft-ietf-spring-srv6-network-programming-28 (work in
              progress), December 2020.

   [RFC2474]  Nichols, K., Blake, S., Baker, F., and D. Black,
              "Definition of the Differentiated Services Field (DS
              Field) in the IPv4 and IPv6 Headers", RFC 2474,
              DOI 10.17487/RFC2474, December 1998,
              <https://www.rfc-editor.org/info/rfc2474>.

   [RFC2475]  Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z.,
              and W. Weiss, "An Architecture for Differentiated
              Services", RFC 2475, DOI 10.17487/RFC2475, December 1998,
              <https://www.rfc-editor.org/info/rfc2475>.

   [RFC3031]  Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
              Label Switching Architecture", RFC 3031,
              DOI 10.17487/RFC3031, January 2001,
              <https://www.rfc-editor.org/info/rfc3031>.

   [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>.

   [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>.

   [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>.

   [RFC6241]  Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
              and A. Bierman, Ed., "Network Configuration Protocol
              (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
              <https://www.rfc-editor.org/info/rfc6241>.

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   [RFC7752]  Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and
              S. Ray, "North-Bound Distribution of Link-State and
              Traffic Engineering (TE) Information Using BGP", RFC 7752,
              DOI 10.17487/RFC7752, March 2016,
              <https://www.rfc-editor.org/info/rfc7752>.

   [RFC7950]  Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
              RFC 7950, DOI 10.17487/RFC7950, August 2016,
              <https://www.rfc-editor.org/info/rfc7950>.

Authors' Addresses

   Jie Dong
   Huawei Technologies

   Email: jie.dong@huawei.com

   Stewart Bryant
   Futurewei Technologies

   Email: stewart.bryant@gmail.com

   Takuya Miyasaka
   KDDI Corporation

   Email: ta-miyasaka@kddi.com

   Yongqing Zhu
   China Telecom

   Email: zhuyq8@chinatelecom.cn

   Fengwei Qin
   China Mobile

   Email: qinfengwei@chinamobile.com

   Zhenqiang Li
   China Mobile

   Email: li_zhenqiang@hotmail.com

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   Francois Clad
   Cisco Systems

   Email: fclad@cisco.com

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