A YANG Data Model for Fabric Topology in Data Center NetworksHuawei101 Software Avenue, Yuhua DistrictNanjingJiangsu210012Chinazhuangyan.zhuang@huawei.comHuawei101 Software Avenue, Yuhua DistrictNanjingJiangsu210012Chinashidanian@huawei.comChina Mobile32 Xuanwumen West Ave, Xicheng DistrictBeijingBeijing100053Chinagurong_cmcc@outlook.comPacket Designhari@packetdesign.com
RTG Area
I2RS Working GroupRFCRequest for CommentsI-DInternet-DraftThis document defines a YANG data model for fabric topology in Data Center Network.Normally, a data center (DC) network is composed of single or multiple fabrics which are also known as PODs (Points Of Delivery). These fabrics may be heterogeneous due to implementation of different technologies when a DC network is upgraded or new techniques and features are enrolled. For example, Fabric A may use VXLAN while Fabric B may use VLAN within a DC network. Likewise, an existing fabric may use VXLAN while a new fabric, for example a fabric introduced for DC upgrade and expansion, may implement a technique discussed in NVO3 WG, such as Geneve [I-D. draft-ietf-nvo3-geneve]. The configuration and management of such DC networks with heterogeneous fabrics will result in considerable complexity, requiring a fair amount of sophistication.Luckily, for a DC network, a fabric can be considered as an atomic structure for management purposes. From this point of view, the management of the DC network can be decomposed into a set of tasks to manage each fabric separately, as well as the fabric interconnections. This way, the overall management task becomes very flexible and makes it easy to expand and adopt to DC networks that evolve over time.As a basis for DC fabric management, this document defines a YANG data model [6020][7950] for fabric-based data center topology. To do so, it augments the generic network and network topology data models defined in [I-D.ietf-i2rs-yang-network-topo] with information that is specific to Data Center fabric networks. The model defines the generic configuration and operational state for a fabric-based network topology, which can subsequently be extended by vendors with vendor-specific information as needed. The model can be used by a network controller to represent its view of the fabric topology that it controls and expose this view to network administrators or applications for DC network management. Within the context of topology architecture defined in [I-D.ietf-i2rs-yang-network-topo] and [I.D. draft-ietf-i2rs-usecase-reqs-summary], this model can also be treated as an application of the I2RS network topology model [I-D.ietf-i2rs-yang-network-topo] in the scenario of Data center network management. It can also act as a service topology when mapping network elements at the fabric layer to elements of other topologies, such as L3 topologies as defined in [I.D. draft-ietf-i2rs-yang-l3-topology].By using the fabric topology model defined in this document, people can treat a fabric as a holistic entity and focus on characteristics of a fabric (such as encapsulation type, gateway type, etc.) as well as its connections to other fabrics while putting the underlay topology aside. As such, clients can consume the topology information at the fabric level with no need to be aware of the entire set of links and nodes in the corresponding underlay networks. A fabric topology can be configured by a network administrator using the controller by adding physical devices and links into a fabric. Alternatively, fabric topology can be learned from the underlay network infrastructure.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 [RFC2119].
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.
Fabric: also known as a POD, is a module of network, compute, storage, and application components that work together to deliver networking services. It represents a repeatable design pattern. Its components maximize the modularity, scalability, and manageability of data centers.This section provides an overview of the data center fabric topology model and its relationship with other topology models.The relationship of the DC fabric topology model and other topology models is shown in the following figure.From the perspective of resource management and service provisioning for a data center network, the fabric topology model augments the basic network topology model with definitions and features specific to a DC fabric, to provide common configuration and operations for heterogeneous fabrics.The fabric topology model module is designed to be generic and can be applied to data center fabrics built with different technologies, such as VLAN, VXLAN etc. The main purpose of this module is to configure and manage fabrics and their connections. It provides a fabric-based topology view for data center applications.
In the fabric topology module, a fabric is modeled as a node of a network, as such the fabric-based data center network consists of a set of fabric nodes and their connections. The following depicts a snippet of the definitions to show the main structure of the model. The notation syntax follows [I-D.draft-ietf-netmod-yang-tree-diagrams].The fabric topology module augments the generic ietf-network and ietf-network-topology modules as follows:A new topology type "ietf-fabric-topology" is introduced and added under the "network-types" container of the ietf-network module.Fabric is defined as a node under the network/node container. A new container "fabric-attributes" is defined to carry attributes for a fabric such as gateway mode, fabric types, involved device nodes, and links.Termination points (in network topology module) are augmented with fabric port attributes defined in a container. The "termination-point" here is used to represent a fabric "port" that provides connections to other nodes, such as an internal device, another fabric externally, or end hosts. Details of the fabric node and the fabric termination point extension will be explained in the following sections.As an atomic network, a fabric itself is composed of a set of network elements i.e. devices, and related links. The configuration of a fabric is contained under the "fabric-attributes" container depicted as follows. The notation syntax follows [I-D.draft-ietf-netmod-yang-tree-diagrams].In the module, additional data objects for fabric nodes are introduced by augmenting the "node" list of the network module. New objects include fabric name, type of the fabric, descriptions of the fabric as well as a set of options defined in an "options" container. The "options" container includes the gateway-mode type (centralized or distributed) and traffic-behavior (whether an Access Control Lists (ACLs) is needed for the traffic). Also, it includes a list of device-nodes and related links as supporting-nodes to form a fabric network. These device nodes and links are represented as leaf-refs of existing nodes and links in the underlay topology. For the device-node, the "role" object is defined to represent the role of a device within the fabric, such as "SPINE" or "LEAF", which should work together with the gateway-mode.Since a fabric can be considered as a node, "termination-points" can represent fabric "ports" that connect to other fabrics, end hosts, as well as devices inside the fabric.As such, the set of "termination-points" of a fabric indicate all connections of the fabric, including its internal connections, interconnections with other fabrics, and connections to end hosts.The structure of fabric ports is as follows. The notation syntax follows [I-D.draft-ietf-netmod-yang-tree-diagrams].The structure of fabric ports is as follows:It augments the termination points (in network topology module) with fabric port attributes defined in a container.New nodes are defined for fabric ports including fabric name, role of the port within the fabric (internal port, external port to outside network, access port to end hosts), port type (l2 interface, l3 interface, etc). By defining the device-port as a tp-ref, a fabric port can be mapped to a device node in the underlay network.Also, a new container for tunnel-options is introduced to present the tunnel configuration on a port.The termination point information is learned from the underlay networks, not configured by the fabric topology layer.This document registers the following namespace URIs in the "IETF XML Registry" [RFC3688]: URI: urn:ietf:params:xml:ns:yang:ietf-dc-fabric-types
Registrant Contact: The IESG.
XML: N/A; the requested URI is an XML namespace.
URI: urn:ietf:params:xml:ns:yang:ietf-dc-fabric-topology
Registrant Contact: The IESG.
XML: N/A; the requested URI is an XML namespace.
URI: urn:ietf:params:xml:ns:yang:ietf-dc-fabric-topology-state
Registrant Contact: The IESG.
XML: N/A; the requested URI is an XML namespace.
This document registers the following YANG modules in the "YANG
Module Names" registry [RFC6020]:
NOTE TO THE RFC EDITOR: In the list below, please replace references
to "draft-ietf-i2rs-yang-dc-fabric-network-topology-03 (RFC form)" with RFC number
when published (i.e. RFC xxxx).
Name: ietf-dc-fabric-types
Namespace: urn:ietf:params:xml:ns:yang:ietf-dc-fabric-types
Prefix: fabrictypes
Reference: draft-ietf-i2rs-yang-dc-fabric-network-topology-03.txt (RFC form)
Name: ietf-dc-fabric-topology
Namespace: urn:ietf:params:xml:ns:yang:ietf-dc-fabric-topology
Prefix: fabric
Reference: draft-ietf-i2rs-yang-dc-fabric-network-topology-03.txt (RFC form)
Name: ietf-dc-fabric-topology-state
Namespace: urn:ietf:params:xml:ns:yang:ietf-dc-fabric-topology-state
Prefix: sfabric
Reference: draft-ietf-i2rs-yang-dc-fabric-network-topology-03.txt (RFC form)
The YANG module defined in this document is designed to be accessed via network management protocols such as NETCONF [RFC6241] or RESTCONF [RFC8040]. The lowest NETCONF layer is the secure transport layer, and the mandatory-to-implement secure transport is Secure Shell (SSH) [RFC6242]. The lowest RESTCONF layer is HTTPS, and the mandatory-to-implement secure transport is TLS [RFC5246].The NETCONF access control model [RFC6536] provides the means to restrict access for particular NETCONF or RESTCONF users to a preconfigured subset of all available NETCONF or RESTCONF protocol operations and content. The subtrees and data nodes and their sensitivity/vulnerability in the ietf-dc-fabric-topology module are as follows:fabric-attributes: A malicious client could attempt to sabotage the configuration of important fabric attributes, such as device-nodes or type.Some of the readable data nodes in this YANG module may be considered sensitive or vulnerable in some network environments. It is thus important to control read access (e.g., via get, get-config, or notification) to these data nodes. The subtrees and data nodes and their sensitivity/vulnerability in the ietf-dc-fabric-topology module are as follows:fport-attributes: A malicious client could attempt to read the connections of fabrics without permission, such as device-port, name.We wish to acknowledge the helpful contributions, comments, and suggestions that were received from Alexander Clemm, Donald E. Eastlake, Xufeng Liu, Susan Hares, Wei Song, Luis M. Contreras and Benoit Claise.A YANG Data Model for Network TopologiesA YANG Data Model for Layer 3 TopologiesA Revised Conceptual Model for YANG DatastoresKey words for use in RFCs to Indicate Requirement LevelsTransport Layer Security (TLS) Protocol Version 1.2YANG - A Data Modeling Language for the Network Configuration
Protocol (NETCONF)Network Configuration Protocol (NETCONF)Using the NETCONF Protocol over Secure Shell (SSH)Network Configuration Protocol (NETCONF) Access Control ModelCommon YANG Data TypesThe YANG 1.1 Data Modeling LanguageRESTCONF ProtocolVirtual eXtensible Local Area Network (VXLAN): A Framework for Overlaying Virtualized Layer 2 Networks over Layer 3 NetworksGeneve: Generic Network Virtualization EncapsulationSummary of I2RS Use Case RequirementsYANG Tree DiagramsThe YANG module ietf-fabric-toplogy defined in this document augments two modules, ietf-network and ietf-network-topology, that are designed to be used in conjunction with implementations that support the Network Management Datastore Architecture (NMDA) defined in [I-D.draft-ietf-netmod-revised-datastores]. In order to allow implementations to use the model even in case when NMDA is not supported, a set of companion modules have been defined that represent a state model of networks and network topologies, ietf-network-state and ietf-network-topology-state, respectively. In order to be able to use the model for fabric topologies defined
in this in this document in conjunction with non-NMDA compliant implementations, a corresponding companion module needs to be introduced as well. This companion module, ietf-fabric-topology-state, mirrors ietf-fabric-topology. However, the module augments ietf-network-state (instead of ietf-network and ietf-network-topology) and all of its data nodes are non-configurable.Like ietf-network-state and ietf-network-topology-state, ietf-fabric-topology-state SHOULD NOT be supported by implementations that support NMDA. It is for this reason that the module is defined in the Appendix.The definition of the module follows below. As the structure of the
module mirrors that of its underlying module, the YANG tree is not
depicted separately.