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.comNetflixhari@netflix.com
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I2RS Working GroupYANGFabric TopologyData-Center NetworksThis document defines a YANG data model for fabric topology in
data-center networks and represents one possible view of the data-center
fabric. This document focuses on the data model only and does not
endorse any kind of network design that could be based on the
abovementioned model.A data-center (DC) network can be composed of single or multiple
fabrics, which are also known as Points Of Delivery (PODs). These fabrics
may be heterogeneous due to implementation of different technologies
when a DC network is upgraded or new techniques and features are rolled
out. For example, within a DC network, Fabric A may use Virtual eXtensible Local Area Network
(VXLAN) while Fabric B may use VLAN. 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 the NVO3 Working Group, such as
Geneve . The configuration and management
of such DC networks with heterogeneous fabrics could result in
considerable complexity.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. The advantage of
this method is to make the overall management tasks flexible and easy to
extend in the future.As a basis for DC fabric management, this document defines a YANG
data model for a possible view of the fabric-based
data-center topology. To do so, it augments the generic network and
network topology data models defined in 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 , this model can also be treated as an application of
the Interface to the Routing System (I2RS) network topology model 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 .By using the fabric topology model defined in this document, people
can treat a fabric as a holistic entity and focus on its characteristics
(such as encapsulation type and gateway type) 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", "NOT RECOMMENDED",
"MAY", and "OPTIONAL" in this document are to be interpreted as
described in BCP 14
when, and only when, they appear in all capitals, as shown here.
POD: 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.Fabric: composed of several PODs to form a data-center network.
This section provides an overview of the DC 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 .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 and VXLAN. 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 .The fabric topology module augments the generic ietf-network and
ietf-network-topology modules as follows:A new topology type, "ietf-dc-fabric-topology", is defined 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 the 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 (that is, a set of nodes and links that
composes a POD and also supports a single overlay/underlay instance),
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 .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, and 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 List (ACL) is needed for the traffic). Also, it includes a
list of device nodes and related links as "supporting-node" 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 and end hosts,
as well as devices inside the fabric.As such, the set of "termination-points" of a fabric indicate all
of its connections, 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 .This structure augments the termination points (in the 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), and port type (L2 interface, L3
interface). By defining the device port as a tp-ref, a fabric port can
be mapped to a device node in the underlay network.Additionally, 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 module imports typedefs from , and it
references and .This document registers the following namespace URIs in the "IETF XML
Registry" :URI:urn:ietf:params:xml:ns:yang:ietf-dc-fabric-typesRegistrant Contact: The IESG.XML: N/A; the requested URI is an XML namespace. URI:urn:ietf:params:xml:ns:yang:ietf-dc-fabric-topologyRegistrant Contact: The IESG.XML: N/A; the requested URI is an XML namespace.
URI:urn:ietf:params:xml:ns:yang:ietf-dc-fabric-topology-stateRegistrant 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 :
Name: ietf-dc-fabric-typesNamespace: urn:ietf:params:xml:ns:yang:ietf-dc-fabric-typesPrefix: fabrictypesReference: RFC 8542
Name: ietf-dc-fabric-topologyNamespace: urn:ietf:params:xml:ns:yang:ietf-dc-fabric-topologyPrefix: fabricReference: RFC 8542
Name: ietf-dc-fabric-topology-stateNamespace: urn:ietf:params:xml:ns:yang:ietf-dc-fabric-topology-statePrefix: sfabricReference: RFC 8542
The YANG module defined in this document is designed to be accessed
via network management protocols such as NETCONF or RESTCONF . The lowest
NETCONF layer is the secure transport layer, and
the mandatory-to-implement secure transport is Secure Shell (SSH)
. The lowest RESTCONF layer is HTTPS, and the
mandatory-to-implement secure transport is TLS .The Network Configuration Access Control Model (NACM) 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.There are a number of data nodes defined in this YANG module that are
writable/creatable/deletable (i.e., config true, which is the default). These
data nodes may be considered sensitive or vulnerable in some network
environments. Write operations (e.g., edit-config) to these data nodes
without proper protection can have a negative effect on network
operations. 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 and
name.Geneve: Generic Network Virtualization EncapsulationThe YANG module, ietf-dc-fabric-topology, 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 . In order to allow implementations to use the model
even in cases 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 document in conjunction with non-NMDA-compliant
implementations, a corresponding companion module needs to be introduced
as well. This companion module, ietf-dc-fabric-topology-state, mirrors
ietf-dc-fabric-topology. However, the ietf-dc-fabric-topology-state 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-dc-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. As the structure of the
module mirrors that of its underlying module, the YANG tree is not
depicted separately.We wish to acknowledge the helpful contributions, comments, and
suggestions that were received from Alexander Clemm, Donald
E. Eastlake 3rd, Xufeng Liu, Susan Hares, Wei Song, Luis
M. Contreras, and Benoit Claise.