Network Working Group A. Shaikh
Internet-Draft Google
Intended status: Informational R. Shakir
Expires: September 10, 2015 BT
K. D'Souza
AT&T
L. Fang
Microsoft
March 9, 2015
Operational Structure and Organization of YANG Models
draft-openconfig-netmod-model-structure-00
Abstract
This document presents an approach for organizing YANG models in a
comprehensive structure that defines how individual models may be
composed to configure and operate network infrastructure and
services. The structure is itself represented as a YANG model rooted
at a device, with all of the related component models logically
organized in a way that is operationally intuitive.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on September 10, 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
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publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
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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.
1. Introduction
The large number of configuration models recently published cover
much of networking protocols and technology and, in theory, enable a
programmatic, model-driven approach for configuring network devices.
These models have been largely developed individually and in
isolation, however, making it challenging to use them together to
fully configure a device, or manage a set of devices comprising a
service. For example, standard models for interface management
[RFC7223] and system management [RFC7317] are available but there is
no guidance for how they should be used together, or combined with
other models for routing protocols, ACLs, etc. to form a complete
model. Recently, some frameworks (e.g., [RTG-CFG] and [RTG-POLICY])
that tie models together have been developed, but they are
incomplete, covering only a subset of related models.
1.1. Goals and approach
In this document, we describe a structure for organizing YANG
[RFC6020] models that is broadly applicable to physical and virtual
devices. Individual models are composed such that the data they
define can be accessed in a predictable and operationally intuitive
way that is common across implementations. This organization enables
several important capabilities:
o a common schema to access data related to all aspects of a device
o an extensible structure that makes it clear where additional
models or data should be fit (e.g., using YANG augmentation or
imports)
o a place for including metadata that provides useful information
about the corresponding individual models, such as which
organization provides them, which vendors support them, or which
version of the model is deployed
o a common infrastructure model layer on which higher layer service
models can be built, for example by specifying which models are
needed to provide the service
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o an ability to express an instance of the structure consisting of
models that have been validated to work together (i.e., with
information about sources of the models, their versions, etc.), so
that operators can easily identify a set of models that is known
to be mutually consistent
Our approach is to organize the models describing various aspects of
network infrastructure, including devices and their subsystems, and
relevant protocols operating at the link and network layers. The
proposal does not consider a common model for higher level network
services, nor does it specify details of how hardware-related data
should be organized. Both of these are challenging to standardize --
services are subject to operational and business considerations that
vary across network operators, and hardware models are necessarily
dependent on specific platform features and architecture -- and are
thus out of scope of this document. We instead consider the set of
models that are commonly used by network operators, and suggest a
corresponding organization.
As with other models developed from an operator perspective, the
intent is not to be exhaustive by including all possible models in
the overall structure, whether currently available or not. We focus
on components that are deemed most useful for network operators
across a variety of use cases. We recognize, however, that
additional models will be needed in some cases, and this structure is
useful for describing how new models can be fit into the overall
structure.
2. Model overview
The model organization can itself be thought of as a "meta- model",
in that it describes the relationships between individual models. We
choose to represent it also as simple YANG model consisting of lists
and containers to serve as anchor points for the corresponding
individual models.
As shown below, our model is rooted at a "device", which represents a
network router, switch, or similar device. The model is applicable
to both physical, hardware-based devices, as well as software-based
devices such as virtual network functions (VNFs). It does not follow
the hierarchy of any particular implementation, and hence is vendor-
neutral. Nevertheless, the structure should be familiar to network
operators and also readily mapped to vendor implementations.
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+--rw device
+--rw info
| +--rw device-type?
| ...
+--rw hardware
+--rw system
| ...
+--rw interfaces
| ...
+--rw acl
+--rw qos
+--rw logical-routers
...
The key subsystems are represented at the top level of the device,
including, system-wide configuration, interfaces, and routing
instances. The info section can be used for basic device information
such as its type (e.g., physical or virtual), vendor, and model. For
physical devices, the hardware container is intended to be a
placeholder for platform-specific configuration and operational state
data. For example, a common structure for the hardware model might
include chassis, linecards, and ports, but we leave this unspecified.
2.1. System model components
The system container includes a number of subsystems that are
typically configured globally for the device. Some of these, such as
DHCP, Ethernet CFM, or sampling configuration also may have data that
is associated with an interface. For simplicity, these relationships
are not represented in this structural model. The currently defined
subsystems are shown below:
+--rw device
+--rw system
+--rw dns
+--rw ntp
+--rw dhcp
+--rw syslog
+--rw ssh
+--rw stat-coll
+--rw oam
| +--rw snmp
| +--rw cfm
| +--rw twamp
+--rw aaa
| +--rw tacacs
| +--rw radius
+--rw users
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2.2. Interface model components
Interfaces are a crucial part of any network device's configuration
and operational state. They generally include a combination of raw
physical interfaces, link-layer interfaces, addressing configuration,
and logical interfaces that may not be tied to any physical
interface. Several system services, and layer 2 and layer 3
protocols may also associate configuration or operational state data
with different types of interfaces (these relationships are not shown
for simplicity). The interfaces container includes a number of
commonly used components as examples:
+--rw device
+--rw interfaces
+--rw ethernet
| +--rw aggregates
| +--rw vlans
| +--rw lfm
+--rw sonet-sdh
+--rw addressing
| +--rw ipv4
| | +--rw vrrp
| +--rw ipv6
| +--rw vrrp
+--rw tunnels
2.3. Logical routing instances
Logical routers represent the capability on some devices to partition
resources into independent logical routers. In physical devices,
some hardware features are shared across partitions, but routing
protocol instances, routing tables, and configuration are managed
separately. In virtual routers or VNFs, this may correspond to
establishing multiple logical instances using a single software
installation. The model supports configuration of multiple routing
instances on a single device by creating a list of logical routers,
each with their own configuration and operational state related to
routing and switching protocols, as shown below:
+--rw device
+--rw logical-routers
+--rw logical-router* [router-id]
+--rw router-id uint8
+--rw router-name? string
+--rw layer-2-protocols
| ...
+--rw layer-3-protocols
...
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2.4. VRFs and global routing configuration
Virtual routing and forwarding instances (VRFs) are commonly used to
isolate routing domains, for example to create virtual private
networks, each with their own active protocols and routing policies.
Devices also have a global instance of each routing protocol that may
also exchange routes with VRFs through routing policies. The model
describes protocols and policies for both VRF routing instances and
the global instance. The routing policy framework is expected to
follow [RTG-POLICY], which enables import / export policies to be
expressed with respect to a VRF, or the global routing instance.
+--rw device
+--rw logical-routers
+--rw logical-router* [router-id]
+--rw router-id
+--rw router-name?
+--rw layer-3-protocols
+--rw global
| ...
+--rw vrf* [vrf-name]
| ...
+--rw routing-policy
...
3. Populating the structural model
The structural model in this document describes how individual YANG
models may be used together to represent the configuration and
operational state for all parts of a physical or virtual device. It
does not, however, document the actual model in its entirety. In
this section, we outline an option for creating the full model and
also describe how it may be used.
3.1. Constructing the device model
One of the challenges in assembling existing YANG models is that they
are generally written with the assumption that each model is at the
root of the configuration or state tree. Combining models then
results in a multi-rooted tree that does not follow any logical
construction and makes it difficult to work with operationally. In
some cases, models explicitly reference other models (e.g., via
augmentation) to define a relationship, but this is the case for only
a few existing models.
Some examples include the interfaces [RFC7223] and IP management
[RFC7277] models, and proposed IS-IS [RTG-ISIS], OSPF [RTG-OSPF] and
routing configuration [RTG-CFG] models.
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3.2. Pull approach for model composition
To enable model composition, one possible approach is to avoid using
root-level containers in individual component models. Instead, the
top level container (and all other data definitions) can be enclosed
in a YANG 'grouping' statement so that when the model is imported by
another model, its location in the configuration tree can be
controlled by the importing YANG module with the 'uses' statement.
One advantage of this approach is that the importing module has the
flexibility to readily use the data definitions where the author
deems appropriate.
One obvious drawback is that individual models no longer contain any
of their own data definitions and must be used by a higher-level
model for their data nodes to become active. Some judgment as to
which models are more suited for inclusion in higher level models is
also necessary to decide when the corresponding YANG module should
contain only groupings. Another potential drawback is that this
approach does not define a common structure for models to fit
together, limiting interoperability due to implementations using
different structures. To address this, a top-level standard model
structure could be defined and updated to import new models into the
hierarchy as they are defined.
3.3. "Push" approach for model composition
An alternative approach is to develop a top level model which defines
the overall structure of the models, similar to the structure
described in Section 2. Individual models may augment the top level
model with their data nodes in the appropriate locations. The
drawback is the need for a pre-defined top level model structure. On
the other hand, when this top level model is standardized, it can
become the basis for a vendor-neutral way to manage devices, assuming
that the component models are supported by a given implementation.
One question in both approaches is what the root of the top- level
model should be. In this document we selected to base the mode at a
device because this layer should be common across many use cases and
implementations. Starting at a higher layer (e.g., services) makes
defining and agreeing on a common organization more challenging as
discussed in Section 1.1.
Ideally, one could consider a hybrid construction mechanism that
supports both styles of model composition. For example, a YANG
compiler directive could be used to indicate whether an individual
model should assume it is at the root, or whether it is meant for
inclusion in other higher-level models.
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4. Additional use cases
The goal of this document is to motivate the need for an overall
structure for YANG data models that allows all of the data to be
accessed in a common, logical way. With such a structure defined
itself as a simple YANG model, it is possible to consider additional
use cases.
4.1. Model catalog
YANG data models are being developed in a number of organizations,
including standards bodies such as IETF, ONF, and IEEE, as well as
open source projects and ad-hoc working groups. In addition to
understanding how these models can work together, another challenge
for users is the complexity of tracking which organization created a
given model, and the capabilities and coverage each model provides.
This becomes even more difficult when multiple overlapping models are
available for a particular component.
Such a catalog could also be locally defined by an operator to
describe the models needed to instantiate and manage different
services.
The idea of a model catalog is similar to service catalogs in
traditional IT environments. Service catalogs serve as a software-
based registries of available services with information needed to
discover and invoke available services.
The current model structure described in Section 2 focuses on
describing relationships between the models, however there are
several examples of additional metadata that could be captured for
each component model in the overall structural model:
o origin and responsible party for maintenance of the model with
contact information. In IETF standard models, the YANG
'organization' and 'contact' statement contents are a good
example, but this is not necessarily the case for models from
other sources.
o license under which the model is distributed, e.g., open source or
as part of a commercial license
o classification of the model, including its category / subcategory,
whether the model is intended to be used standalone, etc.
o model dependencies, e.g., a list of other modules that are
required
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o namespace information, including base namespace, prefixes, etc. to
enable importing the model
o pointer to the YANG code, if it is freely downloadable
o implementation information, for example, a list of available
implementations that support the model from vendors, open source
projects, etc.
o authentication information to allow users to verify that the model
they download does in fact originate from the stated organization
For such an approach to be useful, we also require a registration
system where model developers can register information about their
models, and update it as needed. The IANA XML Registry" [RFC3688]
provides a basic registry for YANG models, but the information is
somewhat limited and is currently targeted at IETF-standardized
models only. Further details on the proposal for such a registry may
be forthcoming in further revisions to this document.
4.2. Service-layer composition
The proposed structural model covers a wide variety of components and
protocols, and clearly not all of them are needed for all services.
Another envisioned use case for the structural model is the ability
to reference the set of models that are needed for specific use cases
or services. The intent is that the set would be based on best
operational practices as defined by users or operators who run such
services.
One approach for this would be to define a 'service overlay' model,
for example for Layer 3 VPN services, that defines the set of
required configuration and state models, such as VRFs, interfaces,
BGP, policy, ACLs, and QoS. Similar overlay models can be defined
for other services or use cases, for example, basic Internet
operations such as adding new peers or customers, or setting up Layer
2 VPNs. Note these overlay models may be complementary to actual
configuration models for such services, which may focus on providing
an abstracted set of configuration or operational state variables,
which would then be mapped onto device level variables. We leave
discussion of such mapping mechanisms to future revisions.
5. Security Considerations
The model structure described in this document does not define actual
configuration and state data, hence it is not directly responsible
for security risks.
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However, each of the component models that provide the corresponding
configuration and state data should be considered sensitive from a
security standpoint since they generally manipulate aspects of
network configurations. Each component model should be carefully
evaluated to determine its security risks, along with mitigations to
reduce such risks.
6. IANA Considerations
This YANG model currently uses a temporary ad-hoc namespace. If it
is placed or redirected for the standards track, an appropriate
namespace URI will be registered in the IETF XML Registry" [RFC3688].
The YANG structure modules will be registered in the "YANG Module
Names" registry [RFC6020].
7. YANG module
The model structure is described by the YANG module below.
7.1. Model structure
<CODE BEGINS> file model-structure.yang
module model-structure {
yang-version "1";
// namespace
namespace "http://openconfig.net/yang/structure";
prefix "struct";
// import some basic types
// meta
organization "OpenConfig working group";
contact
"OpenConfig working group
netopenconfig@googlegroups.com";
description
"This module describes a model structure for YANG
configuration and operational state data models. Its intent is to
describe how individual device protocol and feature models fit
together and interact.";
revision "2015-03-06" {
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description
"Initial revision";
reference "TBD";
}
// extension statements
// feature statements
// identity statements
// typedef statements
// grouping statements
grouping info {
description
"base system information";
container info {
description
"This container is for base system information, including
device type (e.g., physcal or virtual), model, serial no.,
location, etc.";
leaf device-type {
//TODO: consider changing to an identity if finer grained
// device type classification is envisioned
type enumeration {
enum PHYSICAL {
description "physical or hardware device";
}
enum VIRTUAL {
description "virtual or software device";
}
}
description
"Type of the device, e.g., physical or virtual. This node
may be used to activate other containers in the model";
}
}
}
grouping hardware {
description
"hardware / vendor -specific data relevant to the platform";
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container hardware {
description
"This container is an anchor point for platform-specific
configuration and operational state data. It may be further
organized into chassis, linecards, ports, etc. It is
expected that vendor or platform-specific augmentations
would be used to populate this part of the device model";
}
}
grouping l2-protocol-members {
description "containers for each layer 2 protocol model";
container vsi {
description "virtual switch instance (or virtual forwarding
instance) for use in PWE3 / VPLS services";
}
container ipv6-ndp {
description "IPv6 neighbor discovery";
reference "RFC 4861 - Neighbor Discovery for IP version 6
(IPv6)";
}
container arp {
description "Address resolution protocol";
reference "STD 37 - An Ethernet Address Resolution Protocol";
}
container rstp {
description "rapid spanning tree protocol";
reference "IEEE 802.1D-2004";
}
container lldp {
description "link layer discovery protocol";
reference "IEEE 802.1AB";
}
container ptp {
description
"precision time protocol for time synchronization services.
PTP also typically requires per-interface configuration";
reference "IEEE 1588-2008";
}
}
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grouping l2-protocols {
description "Layer 2 protocol models";
container layer-2-protocols {
description "layer 2 protocols and features";
uses l2-protocol-members;
}
}
grouping igp-protocol-members {
description "containers for IGPs";
container is-is {
description "IS-IS IGP routing protocol";
reference "RFC 1195 - Use of OSI IS-IS for Routing in TCP/IP
and Dual Environments";
}
container ospf {
description "OSPF IGP routing protocols";
container ospf2 {
description "OSPF v2";
reference "RFC 2328 - OSPF Version 2";
}
container ospf3 {
description "OSPF v3";
reference "RFC 5340 - OSPF for IPv6";
}
}
container igp-common {
description "Common parameters for IGP protocols";
}
}
grouping l3-protocol-members-vrf {
description "containers for layer 3 protocol that are supported
in a VRF instance";
container bgp {
description "BGP 4";
reference "RFC 4271 - A Border Gateway Protocol 4 (BGP-4)";
}
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container igp {
description "interior gateway protocols";
uses igp-protocol-members;
}
container bfd {
description "bidirectional forwarding detection";
reference "RFC 5880 - Bidirectional Forwarding Detection
(BFD)";
}
container pim {
description "protocol independent multicast";
reference "RFC 4601 - Protocol Independent Multicast -
Sparse Mode (PIM-SM): Protocol Specification (Revised)";
}
container igmp {
description "Internet group management protocol";
reference "RFC 3376 - Internet Group Management Protocol,
Version 3";
}
container static-routes {
description "static route that are manually created";
}
}
grouping l3-protocols-misc {
description "containers for other features operating at the
network layer";
}
grouping l3-protocols-mpls {
description "models related to MPLS and TE";
container mpls-te {
description "MPLS and traffic engineering";
container global {
description "global MPLS configuration";
}
container signaling {
description "MPLS signaling protocols";
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container rsvp {
description "RSVP signaling";
reference "RFC 3209 - RSVP-TE: Extensions to RSVP for LSP
Tunnels";
}
container segment-routing {
description "SR signaling";
reference "Segment Routing Architecture -
draft-filsfils-spring-segment-routing-04";
}
container ldp {
description "label distribution protocol";
reference "RFC 5036 - LDP Specification";
}
}
container label-switched-paths {
description "models for different types of LSPs";
container constrained-path {
description "traffic-engineered, or constrained path LSPs";
}
container igp-congruent {
description "LSPs that follow the IGP-computed path";
}
container static {
description "statically configured LSPs";
}
}
}
}
grouping l3-protocol-members {
description "containers for all layer 3 protocols";
uses l3-protocol-members-vrf;
uses l3-protocols-misc;
uses l3-protocols-mpls;
}
grouping l3-routing-policy {
description "containers for routing policy models";
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container common {
description "generic routing policy framework and
configuration parameters";
}
container bgp-policy {
description "BGP-specific routing policy parameters";
}
container igp-policy {
description "IGP routing policy knobs -- may include
policy parameters for specific IGPs";
}
container vrf-policy {
description "import/export policies for VRFs";
}
}
grouping l3-protocols {
description "Layer 3 protocol models";
container layer-3-protocols {
description "layer 3 protocols and features";
container global {
description "router-wide instance of each routing protocol";
uses l3-protocol-members;
}
list vrf {
key vrf-name;
description "list of VRF instances";
leaf vrf-name {
type string;
description "name or id of the routing instance / VRF";
}
uses l3-protocol-members-vrf;
}
container routing-policy {
description "models related to routing policy across
protocols and VRFs";
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uses l3-routing-policy;
}
}
}
grouping interface-ip-common {
description
"interface-specific configuration for IP interfaces, IPv4 and
IPv6";
container vrrp {
description "virtual router redundancy protocol";
reference "RFC 5798 - Virtual Router Redundancy Protocol
(VRRP) Version 3 for IPv4 and IPv6";
}
}
grouping interface-addr-families {
description
"containers for addr family-specific data attached
to interfaces";
container ipv4 {
description "IPv4 interfaces";
uses interface-ip-common;
}
container ipv6 {
description "IPv6 interfaces";
uses interface-ip-common;
}
}
grouping interfaces {
description "interface-related models";
container interfaces {
description "various interface models";
container ethernet {
description "Ethernet interface config, e.g., 10, 40,
100GBE";
container aggregates {
description "LAGs, LACP, etc. for Ethernet interfaces";
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reference "IEEE 802.1ad, 802.1AX";
}
container vlans {
description "VLANs, 802.1q, q-in-q, etc.";
reference "IEEE 802.1Q";
}
container lfm {
description
"Link-layer fault management for Ethernet interfaces";
reference "IEEE 802.3ah";
}
}
container sonet-sdh {
description "SONET/SDH interfaces";
reference
"SDH: ITU standards G.707, G.783, G.784, and G.803
SONET: ANSI standard T1.105";
}
container addressing {
description "addressing and other interface-specific data,
e.g., data plane protocols";
uses interface-addr-families;
}
container tunnels {
description
"logical tunnel interfaces incl. GRE, VxLAN, L2TP etc.";
}
}
}
grouping oam {
description "containers for features related to operations,
administration, and management";
container oam {
description "commonly use OAM functions on devices";
container snmp {
description "SNMP server information, e.g., allowed clients";
}
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container cfm {
description
"Ethernet connectivity fault management. Also includes
options that are associated with specific interfaces, such
as maintenance endpoint domains.";
reference "IEEE 802.1ag";
}
container twamp {
description
"Two-way active measurement protocol for measuring
round-trip IP layer performance.";
reference "RFC 5357 A Two-Way Active Measurement Protocol
(TWAMP)";
}
}
}
grouping system-services {
description "containers for system service models";
container dns {
description "domain name service and resolver configurration";
}
container ntp {
description "network time protocol configuration";
}
container dhcp {
description "dhcp and relay services";
}
container syslog {
description "syslog configuration";
}
container ssh {
description "ssh server configuration";
}
container stat-coll {
description
"mechanisms for data collection from devices, including
packet and flow-level sampling";
}
uses oam;
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}
grouping system-aaa {
description "AAA-related services";
container aaa {
description "authentication, authorization, and accounting";
container tacacs {
description "TACACS+ configuration";
}
container radius {
description "RADIUS";
reference "RFC 2865 - Remote Authentication Dial In User
Service (RADIUS)";
}
}
}
grouping system {
description "system-wide services";
container system {
description "system services";
uses system-services;
uses system-aaa;
container users {
description "local user configuration";
}
}
}
grouping acl {
description "forwarding rules";
container acl {
description "ACLs and packet forwarding rules";
}
}
grouping qos {
description "QoS features";
container qos {
description "QoS, including policing, shaping, etc.";
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}
}
// data definition statements
container device {
description "top-level anchor point for models. Device is a
generic L2/L3 network element";
uses info;
uses hardware;
uses system;
uses interfaces;
uses acl;
uses qos;
container logical-routers {
description "devices may support multiple logical router
instances";
list logical-router {
key router-id;
description "list of logical router instances";
leaf router-id {
type uint8; // expect a small number of logical routers
description "identifier of the logical router instance";
}
leaf router-name {
type string; // expect a small number of logical routers
description "identifier of the logical router instance";
}
uses l2-protocols;
uses l3-protocols;
}
}
}
// augment statements
// rpc statements
// notification statements
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}
<CODE ENDS>
8. References
8.1. Normative references
[RFC6020] Bjorklund, M., "YANG - A Data Modeling Language for the
Network Configuration Protocol (NETCONF)", RFC 6020,
October 2014.
[RFC7223] Bjorklund, M., "A YANG Data Model for Interface
Management", RFC 7223, May 2014.
[RFC7277] Bjorklund, M., "A YANG Data Model for IP Management", RFC
7277, June 2014.
[RFC7317] Bierman, A. and M. Bjorklund, "A YANG Data Model for
System Management", RFC 7317, August 2014.
[RFC3688] Mealling, M., "The IETF XML Registry", RFC 3688, January
2004.
8.2. Informative references
[RTG-CFG] Lhotka, L., "A YANG Data Model for Routing Management",
draft-ietf-netmod-routing-cfg-16 (work in progress),
October 2014.
[RTG-POLICY]
Shaikh, A., Shakir, R., D'Souza, K., and C. Chase,
"Routing Policy Configuration Model for Service Provider
Networks", draft-shaikh-rtgwg-policy-model-00 (work in
progress), January 2015.
[RTG-OSPF]
Yeung, D., Qu, Y., Zhang, J., and D. Bogdanovic, "Yang
Data Model for OSPF Protocol", draft-yeung-netmod-ospf-02
(work in progress), October 2014.
[RTG-ISIS]
Litkowski, S., Yeung, D., Lindem, A., Zhang, J., and L.
Lhotka, "YANG Data Model for ISIS protocol", draft-ietf-
isis-yang-isis-cfg-01 (work in progress), October 2014.
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Appendix A. Acknowledgements
The authors are grateful for valuable contributions to this document
and the associated models from: Deepak Bansal, Paul Borman, Chris
Chase, Josh George, Marcus Hines, and Jim Uttaro.
Authors' Addresses
Anees Shaikh
Google
1600 Amphitheatre Pkwy
Mountain View, CA 94043
US
Email: aashaikh@google.com
Rob Shakir
BT
pp. C3L, BT Centre
81, Newgate Street
London EC1A 7AJ
UK
Email: rob.shakir@bt.com
URI: http://www.bt.com/
Kevin D'Souza
AT&T
200 S. Laurel Ave
Middletown, NJ
US
Email: kd6913@att.com
Luyuan Fang
Microsoft
205 108th Ave. NE, Suite 400
Bellevue, WA
US
Email: lufang@microsoft.com
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