Network Working Group L.Contreras Internet Draft Telefonica I+D Intended status: Standard Track J. Bi Expires: August 2015 Tsinghua University Andrew Qu Mediatek Yiyong Zha Huawei Technologies February 6, 2015 A YANG Data Model for Network Topologies draft-contreras-supa-yang-network-topo-03 Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html This Internet-Draft will expire on August 6, 2015. Copyright Notice Copyright (c) 2015 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 (http://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 Contreras, et al. Expires August 6, 2015 [Page 1] Internet-Draft A YANG Data Model for Network Topologies February 2015 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. Abstract This document defines a YANG data model for network topologies. Table of Contents 1. Introduction .......................................'...... 2 2. Conventions used in this document ......................... 3 3. Terminology ...............................'............... 4 4. Network topology model overview ........................... 4 4.1. Topology information model ............................. 4 4.2. Topology data model .................................... 6 4.3. Topology data model structure .......................... 7 4.4. Main building blocks ................................... 9 4.4.1. Virtual topology ................................... 10 5. SUPA topology YANG model ................................. 11 6. Security Considerations .................................. 25 7. IANA Considerations ...................................... 25 8. Acknowledgments '......................................... 25 9. References ..'............................................ 25 9.1. Normative References .................................. 25 9.2. Informative References ................................ 25 1. Introduction This document introduces a YANG data model for network topologies. The model allows an application to have a holistic view of an entire network. In order to capture information that is specific to a particular type of network topology, the data model contains elements such as nodes and links that constitute a topology graph, as well as termination points which are contained in the nodes that actually terminate links of the graph, more specifically, termination points can also be gathered in the clients as well as servers. Besides, in order to provide views at different network layers, the network topology information model has a "layer" property to indicate the layer where the topology underlays. Now the "layer" property has three values: [editor's note: wireless is also important, and will be taken into account later], physical, datalink and network including IP and MPLS can be extended to layer 4, 5 and 7. The data model is generic in nature and can depict the network topology in the specific network layer as the application expects. As a result, the data model can be applied to any type of network topology. Contreras, et al. Expires August 6, 2015 [Page 2] Internet-Draft A YANG Data Model for Network Topologies February 2015 Topology model abstracts the elements of a network, and provides a holistic view of the whole network to applications. Based on the topology model and vendor-neutral policy configurations, service management can configure policies based on the service request at the network level rather than the device level. SUPA (Simplified Use of Policy Abstractions) could translate the policy configuration from network level to device level, and deploy the policy configuration to the network. More specifically, from service management's point of view: With knowledge of the underlying network such as the topology of the infrastructure, either physical or logical, service management can deploy a policy/service to the network devices. Here the topology data model is the information of the underlying network that from controller. From the controller's point of view: The controller is responsible for maintaining the infrastructure information, and it provides this information to service management with the topology information model. The detail procedure of how to use the topology information when mapping the service to device can be found in SUPA mapping draft. The data model is mainly defined in a YANG module named "topology", which contains a generic network topology model. It models a graph set of "connected" network elements, such as links, nodes, termination points, external nodes, external termination points, and external links. External nodes, external termination points and external links may not exist in a specific topology. Technically, a subset of the topology can be virtualized as one node, shown as the node container in the next few sections. The model is also capable of depicting the topology at different layers, thus a network can be represented in the way as applications expect. In another word, different users or applications may have different views of the topology. 2. Conventions used in this document 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. In this document, these words will appear with that interpretation only when in ALL CAPS. Lower case uses of these words are not to be interpreted as carrying RFC-2119 significance. Contreras, et al. Expires August 6, 2015 [Page 3] Internet-Draft A YANG Data Model for Network Topologies February 2015 3. Terminology NETCONF: Network Configuration Protocol SUPA: Simplified Use of Policy Abstractions YANG: A data modeling language used to model configuration and state data manipulated by the NETCONF protocol. 4. Network topology model overview 4.1. Topology information model This section provides an overview of the network topology information model. As shown in figure 1, the information model is mainly focused on the hierarchy of the topology information. Topology information may be originated from network elements from different layers. Furthermore, SDN operation is basically the manipulation of managed object instances, the information model of network topology should be organized into a hierarchical manner in order to capture information that is specific to different network topology types. The scope of this document is focused on the generic and abstract topology model with certain typical models for specific topologies. Other topology models can be derived from the abstract one. Contreras, et al. Expires August 6, 2015 [Page 4] Internet-Draft A YANG Data Model for Network Topologies February 2015 +--------------------------------+ | | | SUPA topologies | | | +---^----------------^-------^---+ | | | | | | +-----------------+--------------+ | | | Network topology model | | | | | | | | IP MPLS | | | |------+------+------------------| | | | | | | | | | | | | | +----+-----------------------+ | IGP BGP | | | | | ^ ^ | | | Datalink topology model | | | | | | |----------------------------| | | | <----+ IEEE802.3 Ethernet PPP | | OSPF ISIS | | | | | ^ ^ | | | ATM token ring X.25 | | | | | | | | | | | | | +-------^--------------------+ | TE | | | +--------------------------^-----+ | | | | | | | | +----+-------+----------+---+ | | | Physical topology model | |---------------------------| | optical copper hub | | | | adapter repeater | | | +---------------------------+ Figure 1 Topology information model structure Physical topology: This type of topology consists of physical devices and the transmission medium among them such as physical link, optical and so on. Besides topology information those electrical and electronic specifications are also the components of this physical topology. Physical topology model is the base of all other topology models over physical topology model. Data-link topology: This type of topology focuses on network elements that are visible with the help of different data-link Contreras, et al. Expires August 6, 2015 [Page 5] Internet-Draft A YANG Data Model for Network Topologies February 2015 protocols and their characteristics. Meanwhile, virtual/logical link is running on this level to support the control plane which does not care physical media. It is over physical topology model and on the other hand, both IP and non-IP topology model can be over data link topology model. Network topology: This type of topology emphasizes network elements and connections that can be discovered by protocols in network stack. It can be further classified into different subordinate topologies according to the protocol used. Virtual topology will also be discussed in the section 4.4.1. 4.2. Topology data model The topology data model in figure 2 defines a network topology at a general level of abstraction. It models aspects such as nodes, links and termination point. The universal elements of the data model are as follows: A network at any layer can contain multiple topologies. Each topology is captured in its own list elements, distinguished via a topology ID. Topology: A topology is used to describe network entities and their relationships. Usually a topology may contain different nodes, links and termination point. A topology can be uniquely identified by its topology ID. A network can be represented by several different topologies which may be organized into hierarchical manners. Also, hierarchical fashioned controller architecture is equipped. In this way, the multi-controller case can be handled that different controller fetch the different layer of topology based on its demand. Node: A node, uniquely identified by its node ID in this topology, can represent one network entity either physical or logical. According to the controller scope that the nodes belong to, they can be referred as (internal) nodes or external nodes respectively. Link: A link, uniquely identified by its link ID, is a demonstration of the point-to-point connectivity between two nodes. It is expressed in a unidirectional manner and defines its direction with the help of its source and destination termination points. Similarly as nodes, links can be subcategorized into (internal) links or external links according to their controller scope. Termination point: A termination point is used to describe the attachment relationship between a node and one of its links. It can be uniquely identified by the termination point ID in the Contreras, et al. Expires August 6, 2015 [Page 6] Internet-Draft A YANG Data Model for Network Topologies February 2015 corresponding node. One node may contain multiple termination points but one termination point only associates one link to the node. ExtNode, extLink and extTerminationPoint of a topology are also defined to depict nodes, links and terminationPoints which are not under the control of the controller in the topology. These elements have the same attributes as the internal elements of the topology. The node, link, and termination point also should be capable of being defined at different network layer. The design method of such elements will be described in following sections. An overview of the YANG module for topology is illustrated in the figure below. +-------------------------+ | | | Topology | | | +-+-+----+---------+--+-+-+ | | | | | | | | | | | | | | | | | | | | | | | | +------------+ | | | | | | | | | | +------------------+ | +-----+ | | +--------+ | | | | +-+ | | | | | | | | +--+---+ +--+---+ +----+------++---+---+ +---+---+ +-----+-----+ |link | |node | |termination||extLink| |extNode| |extTerminat| +------+ +------+ |Point |+-------+ +-------+ |ionPoint | +-----------+ +-----------+ Figure 2 Topology data model structure 4.3. Topology data model structure The structure of the topology data model, as defined in the YANG module "SUPA- topology ", is described as follow. Brackets denote list keys, "rw" denotes configuration data, "ro" denotes operational state data, "*" denotes the parameter that can have multiple instances, and "?" denotes optional parameters. The figure is intended to provide an overall structure of the topology data model. module: SUPA-topology Contreras, et al. Expires August 6, 2015 [Page 7] Internet-Draft A YANG Data Model for Network Topologies February 2015 +--rw topologies | +--rw topology* [topoId] | +--rw topoId string | +--rw topoName? string | +--rw layer enumeration +--rw nodes | +--rw node* [nodeId] | +--rw nodeId string | +--rw nodeName? string | +--rw nodeType? enumeration | +--rw adminStatus? enumeration | +--ro operStatus? enumeration | +--rw parentTopoID? string +--rw extnodes | +--rw extnode* [nodeId] | +--rw nodeId string | +--rw nodeName? string | +--rw nodeType? enumeration | +--rw adminStatus? enumeration | +--ro operStatus? enumeration | +--rw parentTopoID? string +--rw terminationpoints | +--rw terminationpoint* [tpId] | +--rw tpId string | +--rw tpName? string | +--rw nodeId? string +--rw extterminationpoints | +--rw extterminationpoint* [tpId] | +--rw tpId string | +--rw tpName? string | +--rw nodeId? string | +--rw parentTopoID? string +--rw links | +--rw link* [linkId] | +--rw linkId string | +--rw linkName? string | +--rw linkType? enumeration | +--rw direction? enumeration | +--rw adminStatus? enumeration | +--ro operStatus? enumeration | +--rw sourceNodeId string | +--rw sourceTpId string | +--rw destinationNodeId string | +--rw destinationTpId string | +--rw parentTopoID? string | +--rw linkTeAttrCfg | | +--rw maxReservableBandwidth? uint32 Contreras, et al. Expires August 6, 2015 [Page 8] Internet-Draft A YANG Data Model for Network Topologies February 2015 | | +--rw teIfMetric? uint32 | | +--rw srlg-values* [srlg-value] | | | +--rw srlg-value uint32 | | +--rw administrativeGroups | | +--rw color? uint32 | +--rw linkAttrRun | +--ro physicalBandwidth? uint32 +--rw extlinks +--rw extlink* [linkId] +--rw linkId string +--rw linkName? string +--rw linkType? enumeration +--rw direction? enumeration +--rw adminStatus? enumeration +--ro operStatus? enumeration +--rw sourceNodeId string +--rw sourceTpId string +--rw destinationNodeId string +--rw destinationTpId string +--rw parentTopoID? string +--rw linkTeAttrCfg | +--rw maxReservableBandwidth? uint32 | +--rw teIfMetric? uint32 | +--rw administrativeGroups | +--rw administrativeGroup* [affinityName] | +--rw affinityName string +--rw linkAttrRun +--ro physicalBandwidth? uint32 4.4. Main building blocks A network at any layer can contain multiple topologies. Each topology is captured from its own list of elements, distinguished via a topology ID. A network topology can also be consisted of multiple layers, and one topology reflects all these layers which are hierarchized. A topology can be viewed from a certain layer, e.g., optical indicates layer 0, physical indicates layer 1, datalink indicates layer 2 and IP indicates layer 3. The layer is captured underneath container "layer". This serves as container for a data model that indicates the topology in which network layer. More specifically, the relation of each topology model is that the up level topology model can be constructed over lower level topology model and the network topology model can use each of the topology model. All these layers together construct a unified topology. Contreras, et al. Expires August 6, 2015 [Page 9] Internet-Draft A YANG Data Model for Network Topologies February 2015 A topology contains nodes, links, ternminationpoints, extNode, extLink and extTerminationPoint, and each of them is captured in their own lists. A node has a node ID. Node ID distinguishes the node from other nodes in the list. A node also has attributes such as nodeName, adminStatus, operStatus, and topoID, and the meaning of them can be found in the detailed topology YANG module in section 4. In addition, a node in a topology has three types: physical node, virtual node and container node. A "physical" node is a physical device, such as an actual router, an actual switch, and etc. A "virtual" node here denotes an abstraction of the physical node. More details of virtual node and virtual topology are in next section. A "container" node is an abstract node. A sub topology may be regarded as a container node to simplify the parent topology. The parent topology has a container node that maps a sub topology. The type is captured underneath container "nodeType". A termination point is a begin point or end point of a link, it is identified by a termination point ID. A termination point also has containers such as "topoId", "tpName", "tpType" and "tpId" whose descriptions can be found in section 4. A node has one or more termination points. A termination point can have different values under different scenarios, e.g. "ip" means the value for termination point is IP address. "interface" means interface name. "portId" means port identifier. A link is identified by a link ID, which uniquely identifies the link within the topology. Links are bidirectional or unidirectional. A link contains a "source" and a "destination". Both "source" and "destination" reference to a corresponding node, as well as a termination point on that node. External objects such as extNode, extLink and extTerminationPoint of a topology are objects not controlled by the controller which manage the topology. For example, a link is an internal link between nodes in the network managed by a SDN controller. An external link connects a node in the network managed by a SDN controller to a node in the network managed by the other SDN controller. A link is a connection line in a topology. An external link is a connection line between two different topologies. 4.4.1. Virtual topology Virtual topology is so important and has also been taken into account in the unified topology model. In real network,"data link topology' does not directly feed into control plane topology, since control Contreras, et al. Expires August 6, 2015 [Page 10] Internet-Draft A YANG Data Model for Network Topologies February 2015 plane calculation does not care media. Control plane works on logical/virtual links (software interface index with link capacity such as p2p, or p2mp, or 10G etc). So the virtual topology is the abstraction or aggregation of from the lower level topology to feed the high level topology. In virtual topology, a virtual node is a virtual isolated partition of a physical node or a group of physical nodes. For example a router can be divided into several sub-routers, each of which has external connections. In this way, from external view, each sub-router can be treated as a "virtual" node which simulates the pseudo node in the ISIS broadcast network. The pseudo node is not an actual router. With the pseudo nodes, the network topology is simplified and the LSP is shortened. 5. SUPA topology YANG model module SUPA-topology { namespace "http://"; prefix "SUPA-topology"; organization " "; contact " "; description " "; revision "2015-01-09"{ description "Initial revision."; } container topologies { list topology { key "topoId"; description "Network Topology"; leaf topoId { description "Topology ID"; config true; type string { length "1..32"; } } leaf topoName { description "Topology Name"; config true; type string { length "0..32"; } } Contreras, et al. Expires August 6, 2015 [Page 11] Internet-Draft A YANG Data Model for Network Topologies February 2015 leaf layer { description "layer"; config true; mandatory true; type enumeration { enum physical { value 1; description "L1"; } enum datalink { value 2; description "L2"; } enum network { value 3; description "L3"; } } } } } container nodes { list node { key "nodeId"; description "Topology Node"; leaf nodeId { description "Node Id"; config true; type string { length "0..32"; } } leaf nodeName { description "Node Name"; config true; type string { length "0..32"; } } leaf nodeType { description "Node Type"; Contreras, et al. Expires August 6, 2015 [Page 12] Internet-Draft A YANG Data Model for Network Topologies February 2015 config true; default physical; type enumeration { enum physical { value 0; description "physical"; } enum virtual { value 1; description "virtual"; } } } leaf adminStatus { description "administration status"; config true; default adminUp; type enumeration { enum adminDown { value 0; description "configured to be down"; } enum adminUp { value 1; description "configured to be up"; } } } leaf operStatus { description "running status"; config false; type enumeration { enum down { value 0; description "down"; } enum up { value 1; description "up"; } } } leaf parentTopoID { description "topology ID the node belongs to";one topology may belong to more than one parent topologies? config true; type string { Contreras, et al. Expires August 6, 2015 [Page 13] Internet-Draft A YANG Data Model for Network Topologies February 2015 length "0..32"; } } } } container extnodes { list extnode { key "nodeId"; description "External Nodes"; leaf nodeId { description "Node Id"; config true; type string { length "0..32"; } } leaf nodeName { description "Node Name"; config true; type string { length "0..32"; } } leaf nodeType { description "Node Type"; config true; default physical; type enumeration { enum physical { value 0; description "physical"; } enum virtual { value 1; description "virtual"; } } } leaf adminStatus { description "administration status"; config true; default adminUp; Contreras, et al. Expires August 6, 2015 [Page 14] Internet-Draft A YANG Data Model for Network Topologies February 2015 type enumeration { enum adminDown { value 0; description "configured to be down"; } enum adminUp { value 1; description "configured to be up"; } } } leaf operStatus { description "running status"; config false; type enumeration { enum down { value 0; description "down"; } enum up { value 1; description "up"; } } } leaf parentTopoID { description "topology ID the node belongs to"; config true; type string { length "0..32"; } } } } container terminationpoints { list terminationpoint { key "tpId"; description " "; leaf tpId { description "ID"; config true; type string { Contreras, et al. Expires August 6, 2015 [Page 15] Internet-Draft A YANG Data Model for Network Topologies February 2015 length "1..32"; } } leaf tpType { description "Type"; config true; type enumeration { enum down { value IP; description " the value for termination point is IP address"; value interface; description "interface name"; value portID; description "port identifier"; } } } leaf tpName { description "Name"; config true; type string { length "0..32"; } } leaf nodeId { description "the node ID the termination point belongs to"; config true; type string { length "1..32"; } } } } container extterminationpoints { list extterminationpoint { key "tpId"; description " "; leaf tpId { description "ID"; Contreras, et al. Expires August 6, 2015 [Page 16] Internet-Draft A YANG Data Model for Network Topologies February 2015 config true; type string { length "1..32"; } } leaf tpName { description "Name"; config true; type string { length "0..32"; } } leaf nodeId { description "the node ID the termination point belongs to"; config true; type string { length "1..32"; } } leaf parentTopoID { description "topology ID the termination point belongs to"; config true; type string { length "0..32"; } } } } container links { list link { key "linkId"; description "Link"; leaf linkId { description "Link Identifier"; config true; type string { length "0..32"; } } leaf linkName { Contreras, et al. Expires August 6, 2015 [Page 17] Internet-Draft A YANG Data Model for Network Topologies February 2015 description "Link Name"; config true; type string { length "0..32"; } } leaf linkType { description "Link Type"; config true; default physical; type enumeration { enum physical { value 0; description " "; } enum telink { value 1; description " "; } } } leaf direction { description "tunnel direction"; config true; default unidirectional; type enumeration { enum unidirectional { value 0; description "unidirectional"; } enum bidirectional { value 1; description "bidirectional"; } } } leaf adminStatus { description "administration status"; config true; default adminUp; type enumeration { enum adminDown { value 0; description "configured to be down"; } enum adminUp { value 1; Contreras, et al. Expires August 6, 2015 [Page 18] Internet-Draft A YANG Data Model for Network Topologies February 2015 description "configured to be up"; } } } leaf operStatus { description "running status"; config false; type enumeration { enum down { value 0; description "down"; } enum up { value 1; description "up"; } } } leaf sourceNodeId { description "Node Id"; config true; mandatory true; type string { length "1..32"; } } leaf sourceTpId { description "Source Termination Point Id"; config true; mandatory true; type string { length "1..32"; } } leaf destinationNodeId { description "Node Id"; config true; mandatory true; type string { length "1..32"; } } leaf destinationTpId { description "Destination Termination Point Id"; config true; mandatory true; type string { Contreras, et al. Expires August 6, 2015 [Page 19] Internet-Draft A YANG Data Model for Network Topologies February 2015 length "1..32"; } } leaf parentTopoID { description "topology ID the link belongs to"; config true; type string { length "0..32"; } } container linkTeAttrCfg { description "Link TE Attribute"; leaf maxReservableBandwidth { description "Max Reservable Bandwidth Attribute,kbps"; config true; default 0; type uint32 { range "0..4000000000"; } } leaf teIfMetric { description "TE-LINK metric"; config true; type uint32 { range "1..16777215"; } } list srlg-values { description "List of Shared Risk Link Group this interface belongs to."; key "srlg-value"; leaf srlg-value { description "Shared Risk Link Group value"; type uint32; } } container administrativeGroups { leaf color { description "Administrative group or color of the link"; type uint32; Contreras, et al. Expires August 6, 2015 [Page 20] Internet-Draft A YANG Data Model for Network Topologies February 2015 } } } container linkAttrRun { description "link value negotiated"; leaf physicalBandwidth { description "Physical Bandwidth,kbps"; config false; default 0; type uint32 { range "0..4000000000"; } } } } } container extlinks { list extlink { key "linkId"; description "External Links"; leaf linkId { description "Link Identifier"; config true; type string { length "0..32"; } } leaf linkName { description "Link Name"; config true; type string { length "0..32"; } } leaf linkType { description "Link Type"; config true; Contreras, et al. Expires August 6, 2015 [Page 21] Internet-Draft A YANG Data Model for Network Topologies February 2015 default physical; type enumeration { enum physical { value 0; description " "; } enum telink { value 1; description " "; } } } leaf direction { description "tunnel direction"; config true; default unidirectional; type enumeration { enum unidirectional { value 0; description "unidirectional"; } enum bidirectional { value 1; description "bidirectional"; } } } leaf adminStatus { description "administration status"; config true; default adminUp; type enumeration { enum adminDown { value 0; description "configured to be down"; } enum adminUp { value 1; description "configured to be up"; } } } leaf operStatus { description "running status"; config false; type enumeration { enum down { Contreras, et al. Expires August 6, 2015 [Page 22] Internet-Draft A YANG Data Model for Network Topologies February 2015 value 0; description "down"; } enum up { value 1; description "up"; } } } leaf sourceNodeId { description "Node Id"; config true; mandatory true; type string { length "1..32"; } } leaf sourceTpId { description "Source Termination Point Id"; config true; mandatory true; type string { length "1..32"; } } leaf destinationNodeId { description "Node Id"; config true; mandatory true; type string { length "1..32"; } } leaf destinationTpId { description "Destination Termination Point Id"; config true; mandatory true; type string { length "1..32"; } } leaf parentTopoID { description "topology ID the link belongs to"; config true; type string { length "0..32"; } Contreras, et al. Expires August 6, 2015 [Page 23] Internet-Draft A YANG Data Model for Network Topologies February 2015 } container linkTeAttrCfg { description "Link TE Attribute"; leaf maxReservableBandwidth { description "Max Reservable Bandwidth Attribute,kbps"; config true; default 0; type uint32 { range "0..4000000000"; } } leaf teIfMetric { description "TE-LINK metric"; config true; type uint32 { range "1..16777215"; } } container administrativeGroups { list administrativeGroup { key "affinityName"; description " A link may have one or more affinity name. Here is a group of those affinity information."; leaf affinityName { description "Affinity Name"; config true; type string { length "0..32"; } } } } } container linkAttrRun { description "link value negotiated"; leaf physicalBandwidth { Contreras, et al. Expires August 6, 2015 [Page 24] Internet-Draft A YANG Data Model for Network Topologies February 2015 description "Physical Bandwidth,kbps"; config false; default 0; type uint32 { range "0..4000000000"; } } } } } } 6. Security Considerations It will be considered in a future revision. 7. IANA Considerations 8. Acknowledgments The author would like to thank colleagues from China Mobile for their contributions on this work. 9. References 9.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC6020] Bjorklund, M., "YANG - A Data Modeling Language for the Network Configuration Protocol (NETCONF)", RFC 6020, October 2010. [RFC6021] Schoenwaelder, J., "Common YANG Data Types", RFC 6021, October 2010. 9.2. Informative References Contreras, et al. Expires August 6, 2015 [Page 25] Internet-Draft A YANG Data Model for Network Topologies February 2015 [APONF-architecture] C. Zhou, T. Tsou, Q. Sun, D. Lopez, G. Karagiannis, "APONF Architecture", IETF Internet draft, draft-zhou- aponf-architecture-00, June 2014 Authors' Addresses Luis M. Contreras Telefonica I+D Ronda de la Comunicacion, Sur-3 building, 3rd floor Madrid 28050 Spain Email: luismiguel.contrerasmurillo@telefonica.com URI: http://people.tid.es/LuisM.Contreras/ Jun Bi Tsinghua University Network Research Center, Tsinghua University Beijing 100084, China Email: junbi@tsinghua.edu.cn Andrew Qu MediaTek Email: andrew.qu@mediatek.com Yiyong Zha Huawei Technologies Email: zhayiyong@huawei.com Contreras, et al. Expires August 6, 2015 [Page 26]