RFC 8960 PROPOSED STANDARD MPLS · YANG · MANAGEMENT
MPLS YANG: A YANG Data Model for MPLS Base
A standard YANG model that lets management tools configure and read the MPLS forwarding function of a router.
RFC EDITOR
Saad, T., Raza, K., Gandhi, R., Liu, X., and V. Beeram, "A YANG Data Model for MPLS Base", RFC 8960, DOI 10.17487/RFC8960, December 2020, <https://www.rfc-editor.org/info/rfc8960>.
BIBTEX
@misc{rfc8960,
series = {Request for Comments},
number = 8960,
howpublished = {RFC 8960},
publisher = {RFC Editor},
doi = {10.17487/RFC8960},
url = {https://www.rfc-editor.org/info/rfc8960},
author = {T. Saad and K. Raza and R. Gandhi and X. Liu and V. Beeram},
title = {{A YANG Data Model for MPLS Base}},
pagetotal = 29,
year = 2020,
month = dec,
} RFC text
Contents
Internet Engineering Task Force (IETF) T. Saad
Request for Comments: 8960 Juniper Networks
Category: Standards Track K. Raza
ISSN: 2070-1721 R. Gandhi
Cisco Systems, Inc.
X. Liu
Volta Networks
V. Beeram
Juniper Networks
December 2020
A YANG Data Model for MPLS Base
Abstract
This 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.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc8960.
Copyright Notice
Copyright (c) 2020 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
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
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.
Table of Contents
1. Introduction
1.1. Terminology
1.2. Acronyms and Abbreviations
2. MPLS Base Model
2.1. Model Overview
2.2. Model Organization
2.3. Model Design
2.4. Model Tree Diagram
2.5. MPLS Base YANG Module
3. IANA Considerations
4. Security Considerations
5. References
5.1. Normative References
5.2. Informative References
Appendix A. Data Tree Instance Example
Acknowledgments
Contributors
Authors' Addresses
1. Introduction
A core routing YANG data model is defined in [RFC8349]; it provides a
basis for the development of routing data models for specific Address
Families (AFs). Specifically, [RFC8349] defines a model for a
generic Routing Information Base (RIB) that is AF agnostic.
[RFC8349] 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 [RFC8349] 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
[RFC3031].
The MPLS base model also defines a new instance of the generic RIB
YANG data model as defined in [RFC8349] 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 [RFC8402].
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) [RFC8342].
1.1. Terminology
The terminology for describing YANG data models is found in
[RFC7950].
1.2. 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
2. MPLS Base Model
This 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).
2.1. Model Overview
This document models MPLS-labeled routes as an augmentation of the
generic routing RIB data model as defined in [RFC8349]. 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 [RFC8349] to store one or more native MPLS routes
(described further in Section 2.3) by extending the identity
"address-family" defined in [RFC8349] with a new "mpls" identity; see
Section 3 of [RFC8349].
2.2. Model Organization
Routing +---------------+ v: import
YANG module | ietf-routing | o: augment
+---------------+
o
|
v
MPLS base +-----------+ v: import
YANG module | ietf-mpls | o: augment
+-----------+
o o------+
| \
v v
+-------------------+ +---------------------+
MPLS static | ietf-mpls-static@ | | ietf-mpls-ldp.yang@ | . .
LSP YANG +-------------------+ +---------------------+
module
@: not in this document; shown for illustration only
Figure 1: Relationship between MPLS Modules
The "ietf-mpls" YANG module defines the following identities:
mpls:
Identity that extends the "address-family" identity of RIB
instances, as defined in [RFC8349], 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
[RFC3031]. 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:
1. 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.
2. The operation to perform on the packet's label stack. This can
be one of the following operations:
a. Replace the label at the top of the label stack with one or
more specified new labels.
b. Pop the label stack.
c. 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.
d. Push one or more labels onto an unlabeled packet.
The NHLFE may also contain:
1. The data-link encapsulation to use when transmitting the packet.
2. The way to encode the label stack when transmitting the packet.
3. 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 [RFC3031]. 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 [RFC3031].
rib-active-route-mpls-input:
A YANG grouping for the augmentation to the "active-route" RPC
that is specific to the MPLS RIB instance.
2.3. Model Design
The MPLS routing model is based on the core routing data model
defined in [RFC8349]. Figure 2 shows the extensions introduced by
the MPLS base model on defined RIBs.
+-----------------+
| MPLS base model |
+-----------------+
____/ | |_____ |________
/ | \ \
/ | \ \
o o o +
+---------+ +---------+ +--------+ +-----------+
| RIB(v4) | | RIB(v6) | | RIB(x) | | RIB(mpls) |
+---------+ +---------+ +--------+ +-----------+
+: created by the MPLS base model
o: augmented by the MPLS base model
Figure 2: Relationship between MPLS Model and RIB Instances
As shown in Figure 2, 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 [RFC8349] 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 [RFC8402].
2.4. Model Tree Diagram
The MPLS base tree diagram, which follows the notation defined in
[RFC8340], is shown in Figure 3.
module: ietf-mpls
augment /rt:routing:
+--rw mpls
+--rw ttl-propagate? boolean
+--rw mpls-label-blocks
| +--rw mpls-label-block* [index]
| +--rw index string
| +--rw start-label? rt-types:mpls-label
| +--rw end-label? rt-types:mpls-label
| +--rw block-allocation-mode? identityref
| +--ro inuse-labels-count? yang:gauge32
+--rw interfaces
+--rw interface* [name]
+--rw name if:interface-ref
+--rw mpls-enabled? boolean
+--rw maximum-labeled-packet? uint32
augment /rt:routing/rt:ribs/rt:rib/rt:routes/rt:route:
+--ro mpls-enabled? boolean
+--ro mpls-local-label? rt-types:mpls-label
+--ro destination-prefix? -> ../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
Figure 3: MPLS Base Tree Diagram
2.5. MPLS Base YANG Module
This 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 [RFC8349]
* "ietf-routing-types" as defined in [RFC8294]
* "ietf-yang-types" as defined in [RFC6991]
* "ietf-interfaces" as defined in [RFC8343]
This YANG module also references the following RFCs in defining the
types, YANG groupings, and other features of the YANG module:
[RFC3031], [RFC3032], [RFC4090], [RFC5714], and [RFC7424].
<CODE BEGINS> file "ietf-mpls@2020-12-18.yang"
module ietf-mpls {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-mpls";
prefix mpls;
import ietf-routing {
prefix rt;
reference
"RFC 8349: A YANG Data Model for Routing Management
(NMDA Version)";
}
import ietf-routing-types {
prefix rt-types;
reference
"RFC 8294: Common YANG Data Types for the Routing Area";
}
import ietf-yang-types {
prefix yang;
reference
"RFC 6991: Common YANG Data Types";
}
import ietf-interfaces {
prefix if;
reference
"RFC 8343: A YANG Data Model for Interface Management";
}
organization
"IETF MPLS Working Group";
contact
"WG Web: <https://datatracker.ietf.org/wg/mpls/>
WG List: <mailto:mpls@ietf.org>
Editor: Tarek Saad
<mailto:tsaad@juniper.net>
Editor: Kamran Raza
<mailto:skraza@cisco.com>
Editor: Rakesh Gandhi
<mailto:rgandhi@cisco.com>
Editor: Xufeng Liu
<mailto:xufeng.liu.ietf@gmail.com>
Editor: Vishnu Pavan Beeram
<mailto:vbeeram@juniper.net>";
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;
}
}
<CODE ENDS>
Figure 4: MPLS Base YANG Module
3. IANA Considerations
This document registers the following URI in the "ns" subregistry of
the "IETF XML Registry" [RFC3688].
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 [RFC6020].
Name: ietf-mpls
Namespace: urn:ietf:params:xml:ns:yang:ietf-mpls
Prefix: mpls
Reference: RFC 8960
4. Security Considerations
The YANG module specified in this document defines a schema for data
that 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
[RFC8446].
The Network Configuration Access Control Model (NACM) [RFC8341]
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 [RFC3031] and [RFC3032]
apply for this document as well.
5. References
5.1. Normative References
[RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y.,
Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack
Encoding", RFC 3032, DOI 10.17487/RFC3032, January 2001,
<https://www.rfc-editor.org/info/rfc3032>.
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
DOI 10.17487/RFC3688, January 2004,
<https://www.rfc-editor.org/info/rfc3688>.
[RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for
the Network Configuration Protocol (NETCONF)", RFC 6020,
DOI 10.17487/RFC6020, October 2010,
<https://www.rfc-editor.org/info/rfc6020>.
[RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
and A. Bierman, Ed., "Network Configuration Protocol
(NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
<https://www.rfc-editor.org/info/rfc6241>.
[RFC6242] Wasserman, M., "Using the NETCONF Protocol over Secure
Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011,
<https://www.rfc-editor.org/info/rfc6242>.
[RFC6991] Schoenwaelder, J., Ed., "Common YANG Data Types",
RFC 6991, DOI 10.17487/RFC6991, July 2013,
<https://www.rfc-editor.org/info/rfc6991>.
[RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
RFC 7950, DOI 10.17487/RFC7950, August 2016,
<https://www.rfc-editor.org/info/rfc7950>.
[RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
<https://www.rfc-editor.org/info/rfc8040>.
[RFC8294] Liu, X., Qu, Y., Lindem, A., Hopps, C., and L. Berger,
"Common YANG Data Types for the Routing Area", RFC 8294,
DOI 10.17487/RFC8294, December 2017,
<https://www.rfc-editor.org/info/rfc8294>.
[RFC8340] Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
<https://www.rfc-editor.org/info/rfc8340>.
[RFC8341] Bierman, A. and M. Bjorklund, "Network Configuration
Access Control Model", STD 91, RFC 8341,
DOI 10.17487/RFC8341, March 2018,
<https://www.rfc-editor.org/info/rfc8341>.
[RFC8342] Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
and R. Wilton, "Network Management Datastore Architecture
(NMDA)", RFC 8342, DOI 10.17487/RFC8342, March 2018,
<https://www.rfc-editor.org/info/rfc8342>.
[RFC8343] Bjorklund, M., "A YANG Data Model for Interface
Management", RFC 8343, DOI 10.17487/RFC8343, March 2018,
<https://www.rfc-editor.org/info/rfc8343>.
[RFC8349] Lhotka, L., Lindem, A., and Y. Qu, "A YANG Data Model for
Routing Management (NMDA Version)", RFC 8349,
DOI 10.17487/RFC8349, March 2018,
<https://www.rfc-editor.org/info/rfc8349>.
[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
July 2018, <https://www.rfc-editor.org/info/rfc8402>.
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/info/rfc8446>.
5.2. Informative References
[RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
Label Switching Architecture", RFC 3031,
DOI 10.17487/RFC3031, January 2001,
<https://www.rfc-editor.org/info/rfc3031>.
[RFC4090] Pan, P., Ed., Swallow, G., Ed., and A. Atlas, Ed., "Fast
Reroute Extensions to RSVP-TE for LSP Tunnels", RFC 4090,
DOI 10.17487/RFC4090, May 2005,
<https://www.rfc-editor.org/info/rfc4090>.
[RFC5714] Shand, M. and S. Bryant, "IP Fast Reroute Framework",
RFC 5714, DOI 10.17487/RFC5714, January 2010,
<https://www.rfc-editor.org/info/rfc5714>.
[RFC7424] Krishnan, R., Yong, L., Ghanwani, A., So, N., and B.
Khasnabish, "Mechanisms for Optimizing Link Aggregation
Group (LAG) and Equal-Cost Multipath (ECMP) Component Link
Utilization in Networks", RFC 7424, DOI 10.17487/RFC7424,
January 2015, <https://www.rfc-editor.org/info/rfc7424>.
[RFC7951] Lhotka, L., "JSON Encoding of Data Modeled with YANG",
RFC 7951, DOI 10.17487/RFC7951, August 2016,
<https://www.rfc-editor.org/info/rfc7951>.
Appendix A. Data Tree Instance Example
A simple network setup is shown in Figure 5. 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).
State on R1:
============
IPv4 Prefix MPLS Label
P1: 198.51.100.1/32 16001
P2: 198.51.100.2/32 16002
IPv6 Prefix MPLS Label
P3: 2001:db8:0:10::1/128 16003
P4: 2001:db8:0:10::2/128 16004
RSVP MPLS LSPv4-Tunnel:
Source: 198.51.100.3
Destination: 198.51.100.4
Tunnel-ID: 10
LSP-ID: 1
192.0.2.5/30
2001:db8:0:1::1/64
eth0
+---
/
+-----+
| R1 |
+-----+
\
+---
eth1
192.0.2.13/30
2001:db8:0:2::1/64
Figure 5: Example of Network Configuration
The instance data tree could then be illustrated as shown in
Figure 6, using JSON format [RFC7951]:
{
"ietf-routing:routing":{
"ribs":{
"rib":[
{
"name":"RIB-V4",
"address-family":
"ietf-ipv4-unicast-routing:v4ur:ipv4-unicast",
"routes":{
"route":[
{
"next-hop":{
"outgoing-interface":"eth0",
"ietf-mpls:mpls-label-stack":{
"entry":[
{
"id":1,
"label":16001,
"ttl":255
}
]
},
"ietf-ipv4-unicast-routing:next-hop-address":
"192.0.2.5"
},
"source-protocol":"ietf-isis:isis",
"ietf-mpls:mpls-enabled":true,
"ietf-mpls:mpls-local-label":16001,
"ietf-ipv4-unicast-routing:destination-prefix":
"198.51.100.1/32",
"ietf-mpls:route-context":"SID-IDX:1"
},
{
"next-hop":{
"next-hop-list":{
"next-hop":[
{
"outgoing-interface":"eth0",
"ietf-mpls:index":"1",
"ietf-mpls:backup-index":"2",
"ietf-mpls:role":"primary-and-backup",
"ietf-mpls:mpls-label-stack":{
"entry":[
{
"id":1,
"label":16002,
"ttl":255
}
]
},
"ietf-ipv4-unicast-routing:address":
"192.0.2.5"
},
{
"outgoing-interface":"eth1",
"ietf-mpls:index":"2",
"ietf-mpls:backup-index":"1",
"ietf-mpls:role":"primary-and-backup",
"ietf-mpls:mpls-label-stack":{
"entry":[
{
"id":1,
"label":16002,
"ttl":255
}
]
},
"ietf-ipv4-unicast-routing:address":
"192.0.2.13"
}
]
}
},
"source-protocol":"ietf-isis:isis",
"ietf-mpls:mpls-enabled":true,
"ietf-mpls:mpls-local-label":16002,
"ietf-ipv4-unicast-routing:destination-prefix":
"198.51.100.2/32",
"ietf-mpls:route-context":"SID-IDX:2"
}
]
}
},
{
"name":"RIB-V6",
"address-family":
"ietf-ipv6-unicast-routing:v6ur:ipv6-unicast",
"routes":{
"route":[
{
"next-hop":{
"outgoing-interface":"eth0",
"ietf-mpls:mpls-label-stack":{
"entry":[
{
"id":1,
"label":16003,
"ttl":255
}
]
},
"ietf-ipv6-unicast-routing:next-hop-address":
"2001:db8:0:1::1"
},
"source-protocol":"ietf-isis:isis",
"ietf-mpls:mpls-enabled":true,
"ietf-mpls:mpls-local-label":16003,
"ietf-ipv6-unicast-routing:destination-prefix":
"2001:db8:0:10::1/128",
"ietf-mpls:route-context":"SID-IDX:3"
},
{
"next-hop":{
"next-hop-list":{
"next-hop":[
{
"outgoing-interface":"eth0",
"ietf-mpls:index":"1",
"ietf-mpls:backup-index":"2",
"ietf-mpls:role":"primary-and-backup",
"ietf-mpls:mpls-label-stack":{
"entry":[
{
"id":1,
"label":16004,
"ttl":255
}
]
},
"ietf-ipv6-unicast-routing:address":
"2001:db8:0:1::1"
},
{
"outgoing-interface":"eth1",
"ietf-mpls:index":"2",
"ietf-mpls:backup-index":"1",
"ietf-mpls:role":"primary-and-backup",
"ietf-mpls:mpls-label-stack":{
"entry":[
{
"id":1,
"label":16004,
"ttl":255
}
]
},
"ietf-ipv6-unicast-routing:address":
"2001:db8:0:2::1"
}
]
}
},
"source-protocol":"ietf-isis:isis",
"ietf-mpls:mpls-enabled":true,
"ietf-mpls:mpls-local-label":16004,
"ietf-ipv6-unicast-routing:destination-prefix":
"2001:db8:0:10::2/128",
"ietf-mpls:route-context":"SID-IDX:4"
}
]
}
},
{
"name":"RIB-MPLS",
"address-family":"ietf-mpls:mpls:mpls",
"routes":{
"route":[
{
"next-hop":{
"outgoing-interface":"eth0",
"ietf-mpls:mpls-label-stack":{
"entry":[
{
"id":1,
"label":24002,
"ttl":255
}
]
},
"ietf-ipv4-unicast-routing:next-hop-address":
"192.0.2.5"
},
"source-protocol":"ietf-rsvp:rsvp",
"ietf-mpls:mpls-enabled":true,
"ietf-mpls:mpls-local-label":24001,
"ietf-mpls:destination-prefix":"24001",
"ietf-mpls:route-context":
"RSVP Src:198.51.100.3,Dst:198.51.100.4,T:10,L:1"
}
]
}
}
]
},
"ietf-mpls:mpls":{
"mpls-label-blocks":{
"mpls-label-block":[
{
"index":"mpls-srgb-label-block",
"start-label":16000,
"end-label":16500,
"block-allocation-mode":
"ietf-mpls:label-block-alloc-mode-manager"
}
]
},
"interfaces":{
"interface":[
{
"name":"eth0",
"mpls-enabled":true,
"maximum-labeled-packet":1488
},
{
"name":"eth1",
"mpls-enabled":true,
"maximum-labeled-packet":1488
}
]
}
}
}
}
Figure 6: Instance Data Tree Example
Acknowledgments
The authors would like to thank Xia Chen for her contributions to the
early draft revisions of this document.
Contributors
Igor Bryskin
Huawei Technologies
Email: i_bryskin@yahoo.com
Himanshu Shah
Ciena
Email: hshah@ciena.com
Authors' Addresses
Tarek Saad
Juniper Networks
Email: tsaad@juniper.net
Kamran Raza
Cisco Systems, Inc.
Email: skraza@cisco.com
Rakesh Gandhi
Cisco Systems, Inc.
Email: rgandhi@cisco.com
Xufeng Liu
Volta Networks
Email: xufeng.liu.ietf@gmail.com
Vishnu Pavan Beeram
Juniper Networks
Email: vbeeram@juniper.net
AI ELI5
On this page
PROBLEMOperators need one common, machine-readable way to configure and inspect the MPLS switching function on routers from different makers, and later MPLS features need a shared base to build on.
MECHANISMRFC 8960 defines the ietf-mpls YANG module. It adds MPLS data to the generic routing RIB model from RFC 8349, creates a native MPLS RIB instance, and defines label blocks, MPLS-enabled interfaces and next hop label forwarding entries.
WHY IT MATTERSIt is a Proposed Standard and a base framework: other MPLS YANG modules, such as static LSP, LDP or RSVP-TE models, are expected to augment it.
§1Why an MPLS Base Model
A core routing YANG model already exists in RFC 8349. It describes a generic Routing Information Base (RIB) that does not depend on the address family, plus instances for IPv4 and IPv6. RFC 8960 adds the MPLS part, following the MPLS architecture of RFC 3031.
Its stated purpose is to supply essential building blocks. It is meant as a base for future YANG modules covering more sophisticated MPLS features and for different control-plane protocols. The text expects other IETF modules, for example from the TEAS and MPLS Working Groups, to augment it. The module conforms to the Network Management Datastore Architecture (NMDA) of RFC 8342.
There is already a standard form for a router's routing table. This document adds the extra boxes needed for label-based forwarding, so later documents can keep adding to the same form.
§2Two Ways the Model Touches the RIB
The model works in two ways. First, it augments existing address-family RIBs. An IPv4 prefix in the IPv4 RIB, for example, can carry an MPLS local label and one or more per-next-hop remote labels, which enables MPLS forwarding for that prefix.
Second, it creates a new RIB instance for native MPLS routes, by extending the address-family identity from RFC 8349 with a new mpls identity. These are routes that are enabled for MPLS forwarding but are not stored in another address-family RIB.
The RFC gives these examples of native MPLS routes:
- Routes programmed by RSVP on the Label Switching Routers along an LSP.
- Routes that cross-connect a local label to a Layer 2 or Layer 3 VRF.
- Routes that cross-connect a local label to a Layer 2 adjacency such as an Attachment Circuit.
- Routes that cross-connect a local label to a Layer 3 adjacency such as a Segment Routing Adjacency Segment or Binding SID (RFC 8402).
The router already keeps a list of where to send packets. The model lets each entry also carry a sticker label, and it adds a separate list just for destinations that exist only as labels.
- Feature modulesStatic LSP, LDP and similar modules, not in this document
- ietf-mplsThe MPLS base module defined here
- ietf-routingThe core routing module from RFC 8349
§3Building Blocks of the ietf-mpls Module
The module defines two identities. mpls represents the native MPLS RIB, and label-block-alloc-mode is a base for label-block allocation modes. The module itself derives mpls-unicast from mpls, and two allocation modes: one where the label manager handles allocation within the reserved block, and one where the application does.
Two enumerations are defined. mpls-operations-type lists the operations impose-and-forward, pop-and-forward, pop-impose-and-forward, swap-and-forward and pop-and-lookup. nhlfe-role says whether a next hop is primary, backup or primary-and-backup.
The core data structure is the Next Hop Label Forwarding Entry (NHLFE), used when forwarding a labeled packet. It holds the packet's next hop and the operation to perform on the label stack: replace the top label, pop, replace and then push more labels, or push labels onto an unlabeled packet. It may also hold the data-link encapsulation, the way to encode the label stack and any other information needed to dispose of the packet. A single-next-hop grouping and a multiple-next-hop grouping are provided.
For multiple next hops, each entry has an index, a backup-index that refers to a backup entry (see RFC 4090 and RFC 5714), a loadshare value defaulting to 1 for unequal load balancing, and a role. A share is the ratio of an entry's number to the total across all next hops.
Each label entry is like a to-do card for the router: where to send the packet next, and what to do with its stack of stickers. Cards can also say who is the main route and who is the spare, and how to split traffic.
§4Global, Interface and Label-Block Data
The module adds an mpls container under /routing. It is meant as the attachment point for other MPLS sub-features, such as static LSPs, LDP LSPs and Traffic Engineering LSP tunnels. It holds three things.
ttl-propagate, a boolean that defaults totrue, controls propagating TTL between IP and MPLS.mpls-label-blocksis a list keyed byindex, with astart-label, anend-label, ablock-allocation-modeand a read-onlyinuse-labels-count. Amustrule requires the start label to be less than or equal to the end label.interfaceslists interfaces by name, with ampls-enabledflag that defaults tofalseand amaximum-labeled-packetsize in octets (see RFC 3032).
On routes, the module adds mpls-enabled (default false) and mpls-local-label, which applies only when MPLS is enabled for the route. For native MPLS RIB routes it also adds destination-prefix and route-context. The label stack entries carry a label, a TTL and a traffic class. The active-route action is augmented as well, so a query can be made by MPLS local label on the native MPLS RIB.
There are three kinds of switches on the form: one master setting about countdown timers, a list of label ranges the router may hand out, and a list saying which network ports speak labels.
- routing
- mpls augmentation target for other MPLS modules
- ttl-propagate
- mpls-label-blocks
- mpls-label-block* start-label, end-label, allocation mode
- interfaces
- interface* mpls-enabled, maximum-labeled-packet
- mpls augmentation target for other MPLS modules
§5The Example Data Tree
Appendix A shows an example instance of the data tree in JSON, following RFC 7951. A router R1 has IPv4 and IPv6 prefixes with MPLS labels 16001 to 16004, two interfaces named eth0 and eth1, and an RSVP LSP tunnel with Tunnel-ID 10 and LSP-ID 1.
In the IPv4 RIB, a route for 198.51.100.1/32 is shown with mpls-enabled set to true, a local label of 16001 and a label stack entry with TTL 255. The example illustrates how ordinary IP routes are decorated with MPLS data rather than duplicated.
The appendix is a worked example: a sample router with a few labeled destinations, shown the way a management tool would see them.
§6Security and IANA
The module is accessed through NETCONF (RFC 6241) or RESTCONF (RFC 8040). The mandatory-to-implement transports are SSH for NETCONF and TLS for RESTCONF, and the Network Configuration Access Control Model (RFC 8341) can restrict who may do what.
The RFC calls out the writable start-label and end-label nodes under the label blocks: writing to them may disrupt existing traffic. Reading the augmented next-hop data, and using the active-route action, may disclose next-hop and per-prefix route information that could be used for further attacks. The security considerations of RFC 3031 and RFC 3032 also apply.
For IANA, the document registers the XML namespace urn:ietf:params:xml:ns:yang:ietf-mpls and the YANG module ietf-mpls with prefix mpls.
Because the form controls how a router sends traffic, only trusted people should be able to edit it, and even reading it could show an attacker the routes.
§7References
[RFC3031]RFC 3031Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol Label Switching Architecture", RFC 3031, January 2001.January 2001[RFC3032]RFC 3032Rosen, E., et al., "MPLS Label Stack Encoding", RFC 3032, January 2001.January 2001[RFC8349]RFC 8349Lhotka, L., Lindem, A., and Y. Qu, "A YANG Data Model for Routing Management (NMDA Version)", RFC 8349.March 2018[RFC8342]RFC 8342Bjorklund, M., et al., "Network Management Datastore Architecture (NMDA)", RFC 8342, March 2018.March 2018[RFC7950]RFC 7950Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language", RFC 7950, August 2016.August 2016[RFC8294]RFC 8294Liu, X., et al., "Common YANG Data Types for the Routing Area", RFC 8294, December 2017.December 2017[RFC8402]RFC 8402Filsfils, C., Ed., et al., "Segment Routing Architecture", RFC 8402.July 2018[RFC6241]RFC 6241Enns, R., Ed., et al., "Network Configuration Protocol (NETCONF)", RFC 6241, June 2011.June 2011[RFC8040]RFC 8040Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF Protocol", RFC 8040, January 2017.January 2017