A YANG Data Model for Layer 3 Topologies
RFC 8346
| Document | Type | RFC - Proposed Standard (March 2018) | |
|---|---|---|---|
| Authors | Alexander Clemm , Jan Medved , Robert Varga , Xufeng Liu , Hariharan Ananthakrishnan , Nitin Bahadur | ||
| Last updated | 2022-12-08 | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Formats | |||
| Additional resources | Mailing list discussion | ||
| IESG | Responsible AD | Alia Atlas | |
| Send notices to | (None) |
RFC 8346
quot;Augmentation parameters apply only for networks with
L3 Unicast topology";
}
description
"L3 Unicast node-level attributes ";
uses l3t:l3-node-attributes;
}
augment "/nw-s:networks/nw-s:network/nt-s:link" {
when "../nw-s:network-types/l3t-s:l3-unicast-topology" {
description
"Augmentation parameters apply only for networks with
L3 Unicast topology";
}
description
"Augments topology link attributes";
uses l3t:l3-link-attributes;
}
augment "/nw-s:networks/nw-s:network/nw-s:node/"
+"nt-s:termination-point" {
when "../../nw-s:network-types/l3t-s:l3-unicast-topology" {
description
"Augmentation parameters apply only for networks with
L3 Unicast topology";
}
Clemm, et al. Standards Track [Page 22]
RFC 8346 YANG Data Model for L3 Topologies March 2018
description "Augments topology termination point configuration";
uses l3t:l3-termination-point-attributes;
}
notification l3-node-event {
description
"Notification event for L3 node";
leaf l3-event-type {
type l3t:l3-event-type;
description
"Event type";
}
uses nw-s:node-ref;
uses l3t:l3-unicast-topology-type;
uses l3t:l3-node-attributes;
}
notification l3-link-event {
description
"Notification event for L3 link";
leaf l3-event-type {
type l3t:l3-event-type;
description
"Event type";
}
uses nt-s:link-ref;
uses l3t:l3-unicast-topology-type;
uses l3t:l3-link-attributes;
}
notification l3-prefix-event {
description
"Notification event for L3 prefix";
leaf l3-event-type {
type l3t:l3-event-type;
description
"Event type";
}
uses nw-s:node-ref;
uses l3t:l3-unicast-topology-type;
container prefix {
description
"Contains L3 prefix attributes";
uses l3t:l3-prefix-attributes;
}
}
notification termination-point-event {
description
"Notification event for L3 termination point";
leaf l3-event-type {
type l3t:l3-event-type;
Clemm, et al. Standards Track [Page 23]
RFC 8346 YANG Data Model for L3 Topologies March 2018
description
"Event type";
}
uses nt-s:tp-ref;
uses l3t:l3-unicast-topology-type;
uses l3t:l3-termination-point-attributes;
}
}
<CODE ENDS>
Appendix B. Extending the Model
The model can be extended for specific Layer 3 Unicast types.
Examples include OSPF and IS-IS topologies. This appendix introduces
a YANG module that defines a simple topology model for OSPF. This
module is intended to serve as an example that illustrates how the
general topology model can be refined across multiple levels. It
does not constitute a full-fledged OSPF topology model, which may be
more comprehensive and refined than the model that is described here.
B.1. Example OSPF Topology
B.1.1. Model Overview
The following model shows how the Layer 3 Unicast topology model can
be extended, in this case, to cover OSPF topologies. For this
purpose, a set of augmentations are introduced in a separate YANG
module, "example-ospf-topology", whose structure is depicted in the
following diagram. As before, the notation syntax follows [RFC8340].
Note that one of the lines has been wrapped to adhere to the
72-character line limitation of RFCs.
Clemm, et al. Standards Track [Page 24]
RFC 8346 YANG Data Model for L3 Topologies March 2018
module: example-ospf-topology
augment /nw:networks/nw:network/nw:network-types/
l3t:l3-unicast-topology:
+--rw ospf!
augment /nw:networks/nw:network/l3t:l3-topology-attributes:
+--rw ospf-topology-attributes
+--rw area-id? area-id-type
augment /nw:networks/nw:network/nw:node/l3t:l3-node-attributes:
+--rw ospf-node-attributes
+--rw (router-type)?
| +--:(abr)
| | +--rw abr? empty
| +--:(asbr)
| | +--rw asbr? empty
| +--:(internal)
| | +--rw internal? empty
| +--:(pseudonode)
| +--rw pseudonode? empty
+--rw dr-interface-id? uint32
augment /nw:networks/nw:network/nt:link/l3t:l3-link-attributes:
+--rw ospf-link-attributes
augment /l3t:l3-node-event:
+---- ospf!
+---- ospf-node-attributes
+---- (router-type)?
| +--:(abr)
| | +---- abr? empty
| +--:(asbr)
| | +---- asbr? empty
| +--:(internal)
| | +---- internal? empty
| +--:(pseudonode)
| +---- pseudonode? empty
+---- dr-interface-id? uint32
augment /l3t:l3-link-event:
+---- ospf!
+---- ospf-link-attributes
The module augments "ietf-l3-unicast-topology" as follows:
o A new topology type for an OSPF topology is introduced.
o Additional topology attributes are defined in a new grouping that
augments l3-topology-attributes of the "ietf-l3-unicast-topology"
module. The attributes include an OSPF area-id identifying the
OSPF area.
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RFC 8346 YANG Data Model for L3 Topologies March 2018
o Additional data objects for nodes are introduced by augmenting the
l3-node-attributes of the "ietf-l3-unicast-topology" module. New
objects include router-type and dr-interface-id for pseudonodes.
o Links are augmented with OSPF link attributes.
In addition, the module extends notifications for events concerning
Layer 3 nodes and links with OSPF attributes.
It should be noted that the model defined here represents topology
and is intended as an example. It does not define how to configure
OSPF routers or interfaces.
B.1.2. OSPF Topology YANG Module
The OSPF Topology YANG module is specified below. As mentioned, the
module is intended as an example for how the Layer 3 Unicast topology
model can be extended to cover OSPF topologies, but it is not
normative. Accordingly, the module is not delimited with
<CODE BEGINS> and <CODE ENDS> tags.
file "example-ospf-topology@2017-12-16.yang"
module example-ospf-topology {
yang-version 1.1;
namespace "urn:example:example-ospf-topology";
prefix "ex-ospft";
import ietf-yang-types {
prefix "yang";
}
import ietf-network {
prefix "nw";
}
import ietf-network-topology {
prefix "nt";
}
import ietf-l3-unicast-topology {
prefix "l3t";
}
description
"This module is intended as an example for how the
Layer 3 Unicast topology model can be extended to cover
OSPF topologies.";
typedef area-id-type {
type yang:dotted-quad;
description
"Area ID type.";
}
grouping ospf-topology-type {
Clemm, et al. Standards Track [Page 26]
RFC 8346 YANG Data Model for L3 Topologies March 2018
description
"Identifies the OSPF topology type.";
container ospf {
presence "indicates OSPF Topology";
description
"Its presence identifies the OSPF topology type.";
}
}
augment "/nw:networks/nw:network/nw:network-types/"
+ "l3t:l3-unicast-topology" {
description
"Defines the OSPF topology type.";
uses ospf-topology-type;
}
augment "/nw:networks/nw:network/l3t:l3-topology-attributes" {
when "../nw:network-types/l3t:l3-unicast-topology/" +
"ex-ospft:ospf" {
description
"Augments only for OSPF topology";
}
description
"Augments topology configuration";
container ospf-topology-attributes {
description
"Contains topology attributes";
leaf area-id {
type area-id-type;
description
"OSPF area ID";
}
}
}
augment "/nw:networks/nw:network/nw:node/l3t:l3-node-attributes" {
when "../../nw:network-types/l3t:l3-unicast-topology/" +
"ex-ospft:ospf" {
description
"Augments only for OSPF topology";
}
description
"Augments node configuration";
uses ospf-node-attributes;
}
augment "/nw:networks/nw:network/nt:link/l3t:l3-link-attributes" {
when "../../nw:network-types/l3t:l3-unicast-topology/" +
"ex-ospft:ospf" {
description
"Augments only for OSPF topology";
}
Clemm, et al. Standards Track [Page 27]
RFC 8346 YANG Data Model for L3 Topologies March 2018
description
"Augments link configuration";
uses ospf-link-attributes;
}
grouping ospf-node-attributes {
description
"OSPF node scope attributes";
container ospf-node-attributes {
description
"Contains node attributes";
choice router-type {
description
"Indicates router type";
case abr {
leaf abr {
type empty;
description
"The node is ABR";
}
}
case asbr {
leaf asbr {
type empty;
description
"The node is ASBR";
}
}
case internal {
leaf internal {
type empty;
description
"The node is internal";
}
}
case pseudonode {
leaf pseudonode {
type empty;
description
"The node is pseudonode";
}
}
}
leaf dr-interface-id {
when "../pseudonode" {
description
"Valid only for pseudonode";
}
type uint32;
Clemm, et al. Standards Track [Page 28]
RFC 8346 YANG Data Model for L3 Topologies March 2018
default "0";
description
"For pseudonodes, DR interface-id";
}
}
}
grouping ospf-link-attributes {
description
"OSPF link scope attributes";
container ospf-link-attributes {
description
"Contains OSPF link attributes";
}
} // ospf-link-attributes
augment "/l3t:l3-node-event" {
description
"OSPF node event";
uses ospf-topology-type;
uses ospf-node-attributes;
}
augment "/l3t:l3-link-event" {
description
"OSPF link event";
uses ospf-topology-type;
uses ospf-link-attributes;
}
}
Appendix C. An Example
This section contains an example of an instance data tree in JSON
encoding [RFC7951]. The example instantiates "ietf-l3-unicast-
topology" for the topology that is depicted in the following diagram.
There are three nodes: D1, D2, and D3. D1 has three termination
points: 1-0-1, 1-2-1, and 1-3-1. D2 has three termination points as
well: 2-1-1, 2-0-1, and 2-3-1. D3 has two termination points: 3-1-1
and 3-2-1. In addition, there are six links, two between each pair
of nodes, with one going in each direction.
Clemm, et al. Standards Track [Page 29]
RFC 8346 YANG Data Model for L3 Topologies March 2018
+------------+ +------------+
| D1 | | D2 |
/-\ /-\ /-\ /-\
| | 1-0-1 | |---------------->| | 2-1-1 | |
| | 1-2-1 | |<----------------| | 2-0-1 | |
\-/ 1-3-1 \-/ \-/ 2-3-1 \-/
| /----\ | | /----\ |
+---| |---+ +---| |---+
\----/ \----/
A | A |
| | | |
| | | |
| | +------------+ | |
| | | D3 | | |
| | /-\ /-\ | |
| +----->| | 3-1-1 | |-------+ |
+---------| | 3-2-1 | |<---------+
\-/ \-/
| |
+------------+
Figure 2: A Network Topology Example
The corresponding instance data tree is depicted below. Note that
some lines have been wrapped to adhere to the 72-character line
limitation of RFCs.
{
"ietf-network:networks": {
"network": [
{
"network-types": {
"ietf-l3-unicast-topology:l3-unicast-topology": {}
},
"network-id": "l3-topo-example",
"node": [
{
"node-id": "D1",
"termination-point": [
{
"tp-id": "1-0-1",
"ietf-l3-unicast-topology:
l3-termination-point-attributes": {
"unnumbered-id:": 101
}
},
{
"tp-id": "1-2-1",
Clemm, et al. Standards Track [Page 30]
RFC 8346 YANG Data Model for L3 Topologies March 2018
"ietf-l3-unicast-topology:
l3-termination-point-attributes": {
"unnumbered-id:": 121
}
},
{
"tp-id": "1-3-1",
"ietf-l3-unicast-topology:
l3-termination-point-attributes": {
"unnumbered-id:": 131
}
}
],
"ietf-l3-unicast-topology:l3-node-attributes": {
"router-id": ["203.0.113.1"]
}
},
{
"node-id": "D2",
"termination-point": [
{
"tp-id": "2-0-1",
"ietf-l3-unicast-topology:
l3-termination-point-attributes": {
"unnumbered-id:": 201
}
},
{
"tp-id": "2-1-1",
"ietf-l3-unicast-topology:
l3-termination-point-attributes": {
"unnumbered-id:": 211
}
},
{
"tp-id": "2-3-1",
"ietf-l3-unicast-topology:
l3-termination-point-attributes": {
"unnumbered-id:": 231
}
}
],
"ietf-l3-unicast-topology:l3-node-attributes": {
"router-id": ["203.0.113.2"]
}
},
{
"node-id": "D3",
Clemm, et al. Standards Track [Page 31]
RFC 8346 YANG Data Model for L3 Topologies March 2018
"termination-point": [
{
"tp-id": "3-1-1",
"ietf-l3-unicast-topology:
l3-termination-point-attributes": {
"unnumbered-id:": 311
}
},
{
"tp-id": "3-2-1",
"ietf-l3-unicast-topology:
l3-termination-point-attributes": {
"unnumbered-id:": 321
}
}
],
"ietf-l3-unicast-topology:l3-node-attributes": {
"router-id": ["203.0.113.3"]
}
}
],
"ietf-network-topology:link": [
{
"link-id": "D1,1-2-1,D2,2-1-1",
"source": {
"source-node": "D1",
"source-tp": "1-2-1"
}
"destination": {
"dest-node": "D2",
"dest-tp": "2-1-1"
},
"ietf-l3-unicast-topology:l3-link-attributes": {
"metric1": "100"
}
},
{
"link-id": "D2,2-1-1,D1,1-2-1",
"source": {
"source-node": "D2",
"source-tp": "2-1-1"
}
"destination": {
"dest-node": "D1",
"dest-tp": "1-2-1"
},
"ietf-l3-unicast-topology:l3-link-attributes": {
"metric1": "100"
Clemm, et al. Standards Track [Page 32]
RFC 8346 YANG Data Model for L3 Topologies March 2018
}
},
{
"link-id": "D1,1-3-1,D3,3-1-1",
"source": {
"source-node": "D1",
"source-tp": "1-3-1"
}
"destination": {
"dest-node": "D3",
"dest-tp": "3-1-1"
},
"ietf-l3-unicast-topology:l3-link-attributes": {
"metric1": "100"
}
},
{
"link-id": "D3,3-1-1,D1,1-3-1",
"source": {
"source-node": "D3",
"source-tp": "3-1-1"
}
"destination": {
"dest-node": "D1",
"dest-tp": "1-3-1"
},
"ietf-l3-unicast-topology:l3-link-attributes": {
"metric1": "100"
}
},
{
"link-id": "D2,2-3-1,D3,3-2-1",
"source": {
"source-node": "D2",
"source-tp": "2-3-1"
}
"destination": {
"dest-node": "D3",
"dest-tp": "3-2-1"
},
"ietf-l3-unicast-topology:l3-link-attributes": {
"metric1": "100"
}
},
{
"link-id": "D3,3-2-1,D2,2-3-1",
"source": {
"source-node": "D3",
Clemm, et al. Standards Track [Page 33]
RFC 8346 YANG Data Model for L3 Topologies March 2018
"source-tp": "3-2-1"
}
"destination": {
"dest-node": "D2",
"dest-tp": "2-3-1"
},
"ietf-l3-unicast-topology:l3-link-attributes": {
"metric1": "100"
}
}
]
}
]
}
}
Figure 3: Instance Data Tree
Acknowledgments
We wish to acknowledge the helpful contributions, comments, and
suggestions that were received from Alia Atlas, Andy Bierman, Benoit
Claise, Joel Halpern, Susan Hares, Ladislav Lhotka, Carl Moberg,
Carlos Pignataro, Juergen Schoenwaelder, Michal Vasco, and Kent
Watsen.
Contributors
The model presented in this document was contributed to by more
people than can be listed on the author list. Additional
contributors include:
o Vishnu Pavan Beeram, Juniper
o Igor Bryskin, Huawei
o Ken Gray, Cisco
o Aihua Guo, Huawei
o Tom Nadeau, Brocade
o Tony Tkacik
o Aleksandr Zhdankin, Cisco
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RFC 8346 YANG Data Model for L3 Topologies March 2018
Authors' Addresses
Alexander Clemm
Huawei USA - Futurewei Technologies Inc.
Santa Clara, CA
United States of America
Email: ludwig@clemm.org, alexander.clemm@huawei.com
Jan Medved
Cisco
Email: jmedved@cisco.com
Robert Varga
Pantheon Technologies SRO
Email: robert.varga@pantheon.tech
Xufeng Liu
Jabil
Email: xufeng.liu.ietf@gmail.com
Hariharan Ananthakrishnan
Packet Design
Email: hari@packetdesign.com
Nitin Bahadur
Bracket Computing
Email: nitin_bahadur@yahoo.com
Clemm, et al. Standards Track [Page 35]