A YANG Data Model for MPLS BaseJuniper Networkstsaad@juniper.netCisco Systems, Inc.skraza@cisco.comCisco Systems, Inc.rgandhi@cisco.comVolta Networksxufeng.liu.ietf@gmail.comJuniper Networksvbeeram@juniper.netMPLS YANG Data ModelMPLS ModelMPLS RIBMPLS Routing Information BaseThis document contains a specification of the MPLS base YANG data model. The MPLS
base YANG data model serves as a base framework for configuring and managing an MPLS
switching subsystem on an MPLS-enabled router. It is expected that other MPLS
YANG data models (e.g., MPLS Label Switched Path (LSP) static, LDP, or RSVP-TE
YANG data models) will augment the MPLS base YANG data model.
IntroductionA core routing YANG data model is defined in ; it provides a basis
for the development of routing data models for specific Address Families (AFs).
Specifically, defines a model for a generic Routing Information
Base (RIB) that is AF agnostic. also defines two
instances of RIBs based on the generic RIB model for IPv4 and IPv6 AFs.The MPLS base model defined in this document augments the generic RIB model
defined in with additional data that enables MPLS
forwarding for one or more specific destination prefixes present in one or more AF RIBs, as described in
the MPLS architecture document .The MPLS base model also defines a new instance of the generic RIB YANG data model as
defined in to store native MPLS routes. The native MPLS RIB
instance stores one or more routes that are not associated with other AF instance RIBs
(such as IPv4 or IPv6 instance RIBs) but are enabled for MPLS forwarding.
Examples of such native MPLS routes are routes programmed by RSVP on
one or more transit MPLS routers along the path of a Label Switched Path (LSP). Other examples are
MPLS routes that cross-connect to specific Layer 2 adjacencies, such as Layer 2
Attachment Circuits (ACs); or Layer 3 adjacencies, such as Segment Routing
(SR) Adjacency Segments (Adj-SIDs) as described in .The MPLS base YANG data model serves as a basis for future development of MPLS YANG data
models covering MPLS features and subsystems that are more
sophisticated. The main
purpose is to provide essential building blocks for other YANG data models involving
different control-plane protocols and MPLS functions.To this end, it is expected that the MPLS base data model will be augmented by
a number of other YANG modules developed by the IETF (e.g., by the TEAS and MPLS Working
Groups).The YANG module defined in this document conforms to the Network Management Datastore
Architecture (NMDA) .TerminologyThe terminology for describing YANG data models is found in .Acronyms and Abbreviations
MPLS:
Multiprotocol Label Switching
RIB:
Routing Information Base
LSP:
Label Switched Path
LSR:
Label Switching Router
NHLFE:
Next Hop Label Forwarding Entry
MPLS Base ModelThis document describes the "ietf-mpls" YANG module, which provides base components
of the MPLS data model. It is expected that other MPLS YANG modules will
augment the "ietf-mpls" YANG module for other MPLS extensions to provision
LSPs (e.g., MPLS static, MPLS LDP, or MPLS RSVP-TE LSPs).Model OverviewThis document models MPLS-labeled routes as an
augmentation of the generic routing RIB data model as defined in .
For example, IP prefix routes (e.g., routes stored in IPv4 or IPv6 RIBs) are
augmented to carry additional data to enable them for MPLS forwarding.
This document also defines a new instance of the generic RIB model defined in
to store one or more native MPLS routes (described further in
) by extending the identity "address-family" defined in
with a new "mpls" identity;
see .
Model OrganizationRelationship between MPLS ModulesThe "ietf-mpls" YANG module defines the following identities:
mpls:
Identity that extends the "address-family" identity of RIB
instances, as defined in , to represent the native MPLS RIB instance.
label-block-alloc-mode:
A base YANG identity for one or more supported label-block allocation modes.
The "ietf-mpls" YANG module contains the following high-level types
and groupings:
mpls-operations-type:
An enumeration type that represents support for possible MPLS operation types (impose-and-forward, pop-and-forward, pop-impose-and-forward, and pop-and-lookup).
nhlfe-role:
An enumeration type that represents the role of the
Next Hop Label Forwarding Entry (NHLFE).
nhlfe-single-contents:
A YANG grouping that describes a single NHLFE and its associated parameters as described in the MPLS architecture document . This grouping is
specific to the case when a single next hop is associated with the route.
The NHLFE is used when forwarding a labeled packet. It contains the following information:
The packet's next hop. For "nhlfe-single-contents", only a single next hop is expected, while for
"nhlfe-multiple-contents", multiple next hops are possible.
The operation to perform on the packet's label stack. This
can be one of the following operations:
Replace the label at the top of the label stack with one or more
specified new labels.
Pop the label stack.
Replace the label at the top of the label stack with a
specified new label, and then push one or more specified new
labels onto the label stack.
Push one or more labels onto an unlabeled packet.
The NHLFE may also contain:
The data-link encapsulation to use when transmitting the packet.
The way to encode the label stack when transmitting the packet.
Any other information needed in order to properly dispose of
the packet.
nhlfe-multiple-contents:
A YANG grouping that describes a set of NHLFEs and their associated parameters as described in the MPLS architecture document . This grouping
is used when multiple next hops are associated with the route.
interfaces-mpls:
A YANG grouping that describes the list of MPLS-enabled interfaces on a device.
label-blocks:
A YANG grouping that describes the list of assigned MPLS label blocks and their properties.
rib-mpls-properties:
A YANG grouping for the augmentation of the generic RIB with MPLS label forwarding data as defined in .
rib-active-route-mpls-input:
A YANG grouping for the augmentation to the "active-route" RPC that is specific to the MPLS RIB instance.
Model DesignThe MPLS routing model is based on the core routing data model defined in .
shows the extensions introduced by the MPLS base model on defined RIBs.Relationship between MPLS Model and RIB InstancesAs shown in , the MPLS base YANG data model augments
defined instances of AF RIBs with additional data that enables MPLS
forwarding for destination prefixes stored in such RIBs. For example, an IPv4 prefix
stored in RIB(v4) is augmented to carry an MPLS local label and one or more per-next-hop
remote labels to enable MPLS forwarding for such a prefix.The MPLS base model also creates a separate instance of the generic RIB model
defined in to store one or more MPLS
native routes that are enabled for MPLS forwarding but are not stored in one or more other AF RIBs.Some examples of such native MPLS routes are:
Routes programmed by RSVP on Label Switching Routers (LSRs) along
the path of an LSP,
Routes that cross-connect an MPLS local label to a Layer 2 or
Layer 3 Virtual Routing and Forwarding (VRF) entity,
Routes that cross-connect an MPLS local label to a specific
Layer 2
adjacency or interface, such as Layer 2 Attachment Circuits (ACs), or
Routes that cross-connect an MPLS local label to a Layer 3 adjacency or interface,
such as MPLS Segment Routing (SR) Adjacency Segments (Adj-SIDs) or SR MPLS Binding SIDs as defined in .
Model Tree DiagramThe MPLS base tree diagram, which follows the notation defined in , is shown in .MPLS Base Tree Diagram ../mpls-local-label
+--ro route-context? string
augment /rt:routing/rt:ribs/rt:rib/rt:routes/rt:route/rt:next-hop
/rt:next-hop-options/rt:simple-next-hop:
+--ro mpls-label-stack
+--ro entry* [id]
+--ro id uint8
+--ro label? rt-types:mpls-label
+--ro ttl? uint8
+--ro traffic-class? uint8
augment /rt:routing/rt:ribs/rt:rib/rt:routes/rt:route/rt:next-hop
/rt:next-hop-options/rt:next-hop-list/rt:next-hop-list
/rt:next-hop:
+--ro index? string
+--ro backup-index? string
+--ro loadshare? uint16
+--ro role? nhlfe-role
+--ro mpls-label-stack
+--ro entry* [id]
+--ro id uint8
+--ro label? rt-types:mpls-label
+--ro ttl? uint8
+--ro traffic-class? uint8
augment /rt:routing/rt:ribs/rt:rib/rt:active-route/rt:input:
+---w destination-address? -> ../mpls-local-label
+---w mpls-local-label? rt-types:mpls-label
augment /rt:routing/rt:ribs/rt:rib/rt:active-route/rt:output
/rt:route/rt:next-hop/rt:next-hop-options
/rt:simple-next-hop:
+-- mpls-label-stack
+-- entry* [id]
+-- id uint8
+-- label? rt-types:mpls-label
+-- ttl? uint8
+-- traffic-class? uint8
augment /rt:routing/rt:ribs/rt:rib/rt:active-route/rt:output
/rt:route/rt:next-hop/rt:next-hop-options
/rt:next-hop-list/rt:next-hop-list/rt:next-hop:
+-- index? string
+-- backup-index? string
+-- loadshare? uint16
+-- role? nhlfe-role
+-- mpls-label-stack
+-- entry* [id]
+-- id uint8
+-- label? rt-types:mpls-label
+-- ttl? uint8
+-- traffic-class? uint8]]>MPLS Base YANG ModuleThis section describes the "ietf-mpls" YANG module, which provides base
components of the MPLS data model. Other YANG modules may import and augment
the MPLS base module to add feature-specific data.The "ietf-mpls" YANG module imports the following YANG modules:
"ietf-routing" as defined in
"ietf-routing-types" as defined in
"ietf-yang-types" as defined in
"ietf-interfaces" as defined in
This YANG module also references the following RFCs in defining the
types, YANG groupings, and other features of the YANG module:
,
,
, , and
.MPLS Base YANG Module
WG List:
Editor: Tarek Saad
Editor: Kamran Raza
Editor: Rakesh Gandhi
Editor: Xufeng Liu
Editor: Vishnu Pavan Beeram
";
description
"This YANG module defines the essential components for the
management of the MPLS subsystem. The model fully conforms
to the Network Management Datastore Architecture (NMDA).
Copyright (c) 2020 IETF Trust and the persons identified as
authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with or
without modification, is permitted pursuant to, and subject to
the license terms contained in, the Simplified BSD License set
forth in Section 4.c of the IETF Trust's Legal Provisions
Relating to IETF Documents
(https://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC 8960; see the
RFC itself for full legal notices.";
revision 2020-12-18 {
description
"Initial revision.";
reference
"RFC 8960: A YANG Data Model for MPLS Base";
}
/* Identities */
identity mpls {
base rt:address-family;
description
"This identity represents the MPLS address family.";
}
identity mpls-unicast {
base mpls:mpls;
description
"This identity represents the MPLS unicast address family.";
}
identity label-block-alloc-mode {
description
"Base identity for label-block allocation mode.";
}
identity label-block-alloc-mode-manager {
base label-block-alloc-mode;
description
"Label-block allocation on the reserved block
is managed by the label manager.";
}
identity label-block-alloc-mode-application {
base label-block-alloc-mode;
description
"Label-block allocation on the reserved block
is managed by the application.";
}
/**
* Typedefs
*/
typedef mpls-operations-type {
type enumeration {
enum impose-and-forward {
description
"Operation to impose one or more outgoing labels and
forward to the next hop.";
}
enum pop-and-forward {
description
"Operation to pop the incoming label and forward to the
next hop.";
}
enum pop-impose-and-forward {
description
"Operation to pop the incoming label, impose one or more
outgoing labels, and forward to the next hop.";
}
enum swap-and-forward {
description
"Operation to swap the incoming label with the outgoing
label and forward to the next hop.";
}
enum pop-and-lookup {
description
"Operation to pop the incoming label and perform
a lookup.";
}
}
description
"Types of MPLS operations.";
}
typedef nhlfe-role {
type enumeration {
enum primary {
description
"The next hop acts as the primary for carrying traffic.";
}
enum backup {
description
"The next hop acts as the backup.";
}
enum primary-and-backup {
description
"The next hop simultaneously acts as both the primary and
the backup for carrying traffic.";
}
}
description
"Role of the next hop.";
}
grouping nhlfe-single-contents {
description
"A grouping that describes a single Next Hop Label Forwarding
Entry (NHLFE) and its associated parameters as described in
the MPLS architecture. This grouping is specific to the case
when a single next hop is associated with the route.";
uses rt-types:mpls-label-stack;
}
grouping nhlfe-multiple-contents {
description
"A grouping that describes a set of NHLFEs and their
associated parameters as described in the MPLS
architecture. This grouping is used when multiple next hops
are associated with the route.";
leaf index {
type string;
description
"A user-specified identifier utilized to uniquely
reference the next-hop entry in the next-hop list.
The value of this index has no semantic meaning
other than for referencing the entry.";
}
leaf backup-index {
type string;
description
"A user-specified identifier utilized to uniquely
reference the backup next-hop entry in the NHLFE list.
The value of this index has no semantic meaning
other than for referencing the entry.";
reference
"RFC 4090: Fast Reroute Extensions to RSVP-TE for LSP Tunnels
RFC 5714: IP Fast Reroute Framework";
}
leaf loadshare {
type uint16;
default "1";
description
"This value is used to compute a load share to perform
unequal load balancing when multiple outgoing next hops are
specified. A share is computed as a ratio of this number to
the total under all next hops.";
reference
"RFC 3031: Multiprotocol Label Switching Architecture,
Sections 3.11 and 3.12
RFC 7424: Mechanisms for Optimizing Link Aggregation Group
(LAG) and Equal-Cost Multipath (ECMP) Component Link
Utilization in Networks, Section 5.4";
}
leaf role {
type nhlfe-role;
description
"Role of the NHLFE.";
}
uses nhlfe-single-contents;
}
grouping interfaces-mpls {
description
"List of MPLS interfaces.";
container interfaces {
description
"List of MPLS-enabled interfaces.";
list interface {
key "name";
description
"MPLS-enabled interface entry.";
leaf name {
type if:interface-ref;
description
"A reference to the name of an interface in the system
that is to be enabled for MPLS.";
}
leaf mpls-enabled {
type boolean;
default "false";
description
"'true' if MPLS encapsulation is enabled on the
interface.
'false' if MPLS encapsulation is disabled on the
interface.";
}
leaf maximum-labeled-packet {
type uint32;
units "octets";
description
"Maximum labeled packet size.";
reference
"RFC 3032: MPLS Label Stack Encoding, Section 3.2";
}
}
}
}
grouping globals {
description
"MPLS global configuration grouping.";
leaf ttl-propagate {
type boolean;
default "true";
description
"Propagate TTL between IP and MPLS.";
}
}
grouping label-blocks {
description
"Label-block allocation grouping.";
container mpls-label-blocks {
description
"Label-block allocation container.";
list mpls-label-block {
key "index";
description
"List of MPLS label blocks.";
leaf index {
type string;
description
"A user-specified identifier utilized to uniquely
reference an MPLS label block.";
}
leaf start-label {
type rt-types:mpls-label;
must '. <= ../end-label' {
error-message "'start-label' must be less than or equal "
+ "to 'end-label'";
}
description
"Label-block start.";
}
leaf end-label {
type rt-types:mpls-label;
must '. >= ../start-label' {
error-message "'end-label' must be greater than or "
+ "equal to 'start-label'";
}
description
"Label-block end.";
}
leaf block-allocation-mode {
type identityref {
base label-block-alloc-mode;
}
description
"Label-block allocation mode.";
}
leaf inuse-labels-count {
when "derived-from-or-self(../block-allocation-mode, "
+ "'mpls:label-block-alloc-mode-manager')";
type yang:gauge32;
config false;
description
"Number of labels in use in the label block.";
}
}
}
}
grouping rib-mpls-properties {
description
"A grouping of native MPLS RIB properties.";
leaf destination-prefix {
type leafref {
path "../mpls-local-label";
}
description
"MPLS destination prefix.";
}
leaf route-context {
type string;
description
"A context associated with the native MPLS route.";
}
}
grouping rib-active-route-mpls-input {
description
"A grouping applicable to native MPLS RIB 'active-route'
RPC input augmentation.";
leaf destination-address {
type leafref {
path "../mpls-local-label";
}
description
"MPLS native 'active-route' destination.";
}
leaf mpls-local-label {
type rt-types:mpls-label;
description
"MPLS local label.";
}
}
augment "/rt:routing" {
description
"MPLS augmentation.";
container mpls {
description
"MPLS container to be used as an augmentation target node
for the configuration of other MPLS sub-features, e.g.,
MPLS static Label Switched Paths (LSPs), MPLS LDP LSPs,
and Traffic Engineering MPLS LSP Tunnels.";
uses globals;
uses label-blocks;
uses interfaces-mpls;
}
}
/* Augmentation of MPLS routes */
augment "/rt:routing/rt:ribs/rt:rib/rt:routes/rt:route" {
description
"This augmentation is applicable to all MPLS routes.";
leaf mpls-enabled {
type boolean;
default "false";
description
"Indicates whether MPLS is enabled for this route.";
}
leaf mpls-local-label {
when "../mpls-enabled = 'true'";
type rt-types:mpls-label;
description
"MPLS local label associated with the route.";
}
uses rib-mpls-properties {
/* MPLS Address Family (AF) augmentation to the
native MPLS RIB */
when "derived-from-or-self(../../rt:address-family, "
+ "'mpls:mpls')" {
description
"This augment is valid only for routes of the native MPLS
RIB.";
}
}
}
/* MPLS simple-next-hop augmentation */
augment "/rt:routing/rt:ribs/rt:rib/rt:routes/rt:route/"
+ "rt:next-hop/rt:next-hop-options/rt:simple-next-hop" {
description
"Augments the 'simple-next-hop' case in IP unicast routes.";
uses nhlfe-single-contents {
when "/rt:routing/rt:ribs/rt:rib/rt:routes/rt:route"
+ "/mpls:mpls-enabled = 'true'";
}
}
/* MPLS next-hop-list augmentation */
augment "/rt:routing/rt:ribs/rt:rib/rt:routes/rt:route/"
+ "rt:next-hop/rt:next-hop-options/rt:next-hop-list/"
+ "rt:next-hop-list/rt:next-hop" {
description
"This leaf augments the 'next-hop-list' case of IP unicast
routes.";
uses nhlfe-multiple-contents {
when "/rt:routing/rt:ribs/rt:rib/rt:routes/rt:route"
+ "/mpls:mpls-enabled = 'true'";
}
}
/* MPLS RPC input augmentation */
augment "/rt:routing/rt:ribs/rt:rib/rt:active-route/rt:input" {
description
"Input MPLS augmentation for the 'active-route' action
statement.";
uses rib-active-route-mpls-input {
/* MPLS AF augmentation to the native MPLS RIB */
when "derived-from-or-self(../rt:address-family, "
+ "'mpls:mpls')" {
description
"This augment is valid only for routes of the native MPLS
RIB.";
}
}
}
/* MPLS RPC output augmentation */
augment "/rt:routing/rt:ribs/rt:rib/rt:active-route/"
+ "rt:output/rt:route/"
+ "rt:next-hop/rt:next-hop-options/rt:simple-next-hop" {
description
"Output MPLS augmentation for the 'active-route' action
statement.";
uses nhlfe-single-contents;
}
augment "/rt:routing/rt:ribs/rt:rib/rt:active-route/"
+ "rt:output/rt:route/"
+ "rt:next-hop/rt:next-hop-options/rt:next-hop-list/"
+ "rt:next-hop-list/rt:next-hop" {
description
"Output MPLS augmentation for the 'active-route' action
statement.";
uses nhlfe-multiple-contents;
}
}]]>IANA ConsiderationsThis document registers the following URI in the "ns" subregistry of the "IETF XML Registry"
.
URI:
urn:ietf:params:xml:ns:yang:ietf-mpls
Registrant Contact:
The MPLS WG of the IETF.
XML:
N/A; the requested URI is an XML namespace.
This document registers the following YANG module in the "YANG Module Names"
registry .
Name:
ietf-mpls
Namespace:
urn:ietf:params:xml:ns:yang:ietf-mpls
Prefix:
mpls
Reference:
RFC 8960
Security ConsiderationsThe YANG module specified in this document defines a schema for data
that 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. These are
the subtrees and data nodes and their sensitivity/vulnerability:
"/rt:routing/mpls:mpls/mpls:label-blocks":
There are data
nodes under this path that are writable, such as "start-label" and
"end-label". Write operations to those data nodes may result in
disruption to existing traffic.
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. These are the subtrees and data nodes and their
sensitivity/vulnerability:
"/rt:routing/rt:ribs/rt:rib/rt:routes/rt:route/rt:next-hop/rt:next-hop-options/rt:next-hop-list/rt:next-hop-list/rt:next-hop" and
"/rt:routing/rt:ribs/rt:rib/rt:active-route/rt:output/rt:route/rt:next-hop/rt:next-hop-options/rt:simple-next-hop":
These
two paths are augmented by additional MPLS leafs defined in this model. Access
to this information may disclose the next-hop information for the prefix route and/or other information.
Some of the RPC operations in this YANG module may be considered sensitive or
vulnerable in some network environments. It is thus important to control
access to these operations. These are the operations and their
sensitivity/vulnerability:
"/rt:routing/rt:ribs/rt:rib/rt:active-route/rt:input" and "/rt:routing/rt:ribs/rt:rib/rt:active-route/rt:output/rt:route":
These two paths are augmented
by additional MPLS data nodes that are defined in this model. Access to
those paths may disclose information about per-prefix routes and/or other
information; such disclosure may be used for further attacks.
The security considerations spelled out in and apply for this document as well.ReferencesNormative ReferencesInformative ReferencesData Tree Instance ExampleA simple network setup is shown in . R1 runs the IS-IS routing
protocol and learns about the reachability of two IPv4 prefixes
(P1: 198.51.100.1/32 and P2: 198.51.100.2/32) and two IPv6 prefixes
(P3: 2001:db8:0:10::1/128 and P4: 2001:db8:0:10::2/128). We also assume that
R1 learns about local and remote MPLS label bindings for each prefix
using IS-IS (e.g., using Segment Routing (SR) extensions).Example of Network ConfigurationThe instance data tree could then be
illustrated as shown in , using JSON format :Instance Data Tree ExampleAcknowledgmentsThe authors would like to thank for
her contributions to the early draft revisions of this document.ContributorsHuawei Technologiesi_bryskin@yahoo.comCienahshah@ciena.com