YANG Data Model for Segment RoutingCisco Systemsslitkows.ietf@gmail.comFutureweiyingzhen.qu@futurewei.comCisco Systems301 Mindenhall WayCaryNC27513United States of Americaacee@cisco.comVMware, Incpushpasis.ietf@gmail.comJuniper Networksjefftant.ietf@gmail.comSPRING Working Groupmpls
This document defines three YANG data models. The first is for
Segment Routing (SR) configuration and operation, which is to be
augmented by different Segment Routing data planes. The next is a
YANG data model that defines a collection of generic types and groupings
for SR. The third module defines the configuration and operational states
for the Segment Routing MPLS data plane.
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
.
Copyright Notice
Copyright (c) 2021 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
() 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
. Introduction
. Terminology and Notation
. Tree Diagram
. Prefixes in Data Node Names
. Design of the Data Model
. Configuration
. IGP Control-Plane Configuration
. IGP Interface Configuration
. Adjacency SID (Adj-SID) Properties
. Bundling
. Protection
. State Data
. Notifications
. YANG Modules
. YANG Module for Segment Routing
. YANG Module for Segment Routing Common Types
. YANG Module for Segment Routing MPLS
. Security Considerations
. IANA Considerations
. References
. Normative References
. Informative References
. Configuration Examples
. SR-MPLS with IPv4
. SR-MPLS with IPv6
Acknowledgements
Authors' Addresses
Introduction
This document defines three YANG data models
. The first one is for
Segment Routing (SR)
configuration and operation.
This document does not define the IGP extensions to support SR, but the second
module defines generic
groupings to be reused by IGP extension modules. The reason for this design choice
is to not require implementations to support all IGP extensions. For example, an implementation
may support the IS-IS extension but not the OSPF extension.
The third YANG data model
defines a module that is intended to be used on network
elements to configure or operate the SR MPLS data
plane .
The YANG modules in this document conform to the Network Management
Datastore Architecture (NMDA) .
Terminology and NotationThe key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED",
"MAY", and "OPTIONAL" in this document are to be interpreted as
described in BCP 14
when, and only when, they appear in all capitals, as shown here.Tree DiagramTree diagrams used in this document follow the notation defined in
.Prefixes in Data Node NamesIn this document, names of data nodes, actions, and other
data model objects are often used without a prefix, as long as
it is clear from the context in which YANG module each name is
defined. Otherwise, names are prefixed using the standard prefix
associated with the corresponding YANG module, as shown in .
Prefixes and Corresponding YANG Modules
Prefix
YANG module
Reference
if
ietf-interfaces
rt
ietf-routing
rt-types
ietf-routing-types
yang
ietf-yang-types
inet
ietf-inet-types
Design of the Data ModelThe ietf-segment-routing YANG module augments the routing container in the
ietf-routing model and defines generic
SR configuration and operational state. This module is
augmented by modules supporting different data planes.Module ietf-segment-routing-mpls augments ietf-segment-routing and
supports SR-MPLS data plane configuration and operational state.Module ietf-segment-routing-common defines generic types and groupings
that SHOULD be reused by IGP extension modules.
module: ietf-segment-routing
augment /rt:routing:
+--rw segment-routing
module: ietf-segment-routing-mpls
augment /rt:routing/sr:segment-routing:
+--rw sr-mpls
+--rw bindings
| +--rw mapping-server {mapping-server}?
| | +--rw policy* [name]
| | +--rw name string
| | +--rw entries
| | +--rw mapping-entry* [prefix algorithm]
| | +--rw prefix inet:ip-prefix
| | +--rw value-type? enumeration
| | +--rw start-sid uint32
| | +--rw range? uint32
| | +--rw algorithm identityref
| +--rw connected-prefix-sid-map
| | +--rw connected-prefix-sid* [prefix algorithm]
| | +--rw prefix inet:ip-prefix
| | +--rw value-type? enumeration
| | +--rw start-sid uint32
| | +--rw range? uint32
| | +--rw algorithm identityref
| | +--rw last-hop-behavior? enumeration
| +--rw local-prefix-sid
| +--rw local-prefix-sid* [prefix algorithm]
| +--rw prefix inet:ip-prefix
| +--rw value-type? enumeration
| +--rw start-sid uint32
| +--rw range? uint32
| +--rw algorithm identityref
+--rw srgb
| +--rw srgb* [lower-bound upper-bound]
| +--rw lower-bound uint32
| +--rw upper-bound uint32
+--rw srlb
| +--rw srlb* [lower-bound upper-bound]
| +--rw lower-bound uint32
| +--rw upper-bound uint32
+--ro label-blocks* []
| +--ro lower-bound? uint32
| +--ro upper-bound? uint32
| +--ro size? uint32
| +--ro free? uint32
| +--ro used? uint32
| +--ro scope? enumeration
+--ro sid-db
+--ro sid* [target sid source source-protocol binding-type]
+--ro target string
+--ro sid uint32
+--ro algorithm? uint8
+--ro source inet:ip-address
+--ro used? boolean
+--ro source-protocol -> /rt:routing
/control-plane-protocols
/control-plane-protocol/name
+--ro binding-type enumeration
+--ro scope? enumeration
notifications:
+---n segment-routing-srgb-collision
| +--ro srgb-collisions* []
| +--ro lower-bound? uint32
| +--ro upper-bound? uint32
| +--ro routing-protocol? -> /rt:routing
| /control-plane-protocols
| /control-plane-protocol/name
| +--ro originating-rtr-id? router-or-system-id
+---n segment-routing-global-sid-collision
| +--ro received-target? string
| +--ro new-sid-rtr-id? router-or-system-id
| +--ro original-target? string
| +--ro original-sid-rtr-id? router-or-system-id
| +--ro index? uint32
| +--ro routing-protocol? -> /rt:routing
| /control-plane-protocols
| /control-plane-protocol/name
+---n segment-routing-index-out-of-range
+--ro received-target? string
+--ro received-index? uint32
+--ro routing-protocol? -> /rt:routing
/control-plane-protocols
/control-plane-protocol/name
Configuration
The module ietf-segment-routing-mpls augments the "/rt:routing/sr:segment-routing:"
with an sr-mpls container. This container defines all the configuration
parameters related to the SR MPLS data plane.
The sr-mpls configuration is split into global configuration and interface configuration.
The global configuration includes:
Bindings:
Defines Prefix to Segment Identifier (Prefix-SID) mappings.
The operator can control
advertisement of Prefix-SIDs independently for IPv4 and IPv6. Two
types of mappings are available:
Mapping-server:
Maps prefixes that are not local to a SID. Configuration of bindings does not
automatically allow advertisement of those
bindings. Advertisement must be controlled by each
routing-protocol instance (see ). Multiple mapping policies
may be defined.
Connected prefixes:
Maps connected prefixes to a SID. Advertisement of the mapping
will be done by IGP when enabled for SR (see ). The SID value can be expressed as an index (default) or an absolute
value. The "last-hop-behavior" configuration dictates the MPLS Penultimate Hop Popping (PHP)
behavior: "explicit-null", "php", or "non-php".
Segment Routing Global Block (SRGB):
Defines a list of label
blocks represented by a pair of lower-bound/upper-bound labels.
The SRGB is also agnostic to the control plane used. So, all local
routing-protocol instances will have to advertise the same SRGB.
Segment Routing Local Block (SRLB):
Defines a list of label
blocks represented by a pair of lower-bound/upper-bound labels reserved for local SIDs.
IGP Control-Plane Configuration
Support of SR extensions for a particular IGP control plane is achieved by augmenting routing-protocol configuration with SR extensions.
This augmentation SHOULD be part of the routing-protocol YANG modules as not to create any dependency for implementations to support SR extensions for all routing protocols.
This module defines groupings that SHOULD be used by IGP SR modules.
The "sr-control-plane" grouping defines the generic global configuration for the IGP.The "enabled" leaf enables SR extensions for the
routing-protocol instance.The "bindings" container controls the routing-protocol instance's
advertisement of local bindings and the processing of received
bindings.IGP Interface ConfigurationThe interface configuration is part of the "igp-interface" grouping and includes Adjacency SID (Adj-SID) properties.Adjacency SID (Adj-SID) PropertiesBundling
In case of parallel IP links between routers, an additional Adj-SID may be advertised representing more than one adjacency (i.e.,
a bundle of adjacencies). The "advertise-adj-group-sid" configuration
controls for which group(s) an additional Adj-SID is advertised.
The "advertise-adj-group-sid" is a list of group IDs. Each group ID will identify interfaces that are bundled together.
+-------+ +------+
| | ------- L1 ---- | |
| R1 | ------- L2 ---- | R2 |
| | ------- L3 ---- | |
| | ------- L4 ---- | |
+-------+ +------+
In the figure above, R1 and R2 are interconnected by four links. A routing protocol adjacency is established on each link.
The operator would like to create Adj-SIDs that represent bundles of links. We can imagine two different bundles: L1/L2 and L3/L4.
To achieve this behavior, the operator will configure a "group-id" X for interfaces L1 and L2 and a "group-id" Y for interfaces L3 and L4.
This will result in R1 advertising an additional Adj-SID for each adjacency. For example, an Adj-SID with a value of 400 will be added to L1 and L2, and
an Adj-SID with a value of 500 will be added to L3 and L4. As L1/L2 and L3/L4 do not share the same "group-id", a different SID value will be allocated.
Protection
The "advertise-protection" defines how protection for an interface
is advertised. It does not control the activation or deactivation of
protection. If the "single" option is used, a single Adj-SID will be
advertised for the interface. If the interface is protected, the
B-Flag for the Adj-SID advertisement will be set. If the "dual"
option is used and if the interface is protected, two Adj-SIDs will
be advertised for the interface adjacencies. One Adj-SID will always
have the B-Flag set, and the other will have the B-Flag clear.
This
option is intended to be used in the case of traffic engineering
where a path must use either protected segments or unprotected
segments.
State Data
The operational state contains information reflecting the usage of
allocated SRGB labels.
It also includes a list of all global SIDs, their associated
bindings, and other information, such as the associated source protocol and
algorithm.Notifications
The model defines the following notifications for SR.
segment-routing-srgb-collision:
Raised when control-plane-advertised SRGB blocks have conflicts
segment-routing-global-sid-collision:
Raised when a control-plane-advertised index is already associated with another target (in
this version, the only defined targets are IPv4 and IPv6 prefixes)
segment-routing-index-out-of-range:
Raised when a control-plane-advertised index falls outside the range of SRGBs configured for
the network device
YANG ModulesThere are three YANG modules included in this document. The following RFCs are not referenced in the document text but
are referenced in the ietf-segment-routing.yang, ietf-segment-routing-common.yang,
and/or ietf-segment-routing-mpls.yang modules:
, ,
, ,
, ,
and .YANG Module for Segment Routing
ietf-segment-routing.yang:
This module defines a generic framework
for Segment Routing (SR), and it is to be augmented by models for different
SR data planes.
module ietf-segment-routing {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-segment-routing";
prefix sr;
import ietf-routing {
prefix rt;
reference "RFC 8349: A YANG Data Model for Routing
Management (NMDA Version)";
}
organization
"IETF SPRING - SPRING Working Group";
contact
"WG Web: <https://datatracker.ietf.org/wg/spring/>
WG List: <mailto:spring@ietf.org>
Author: Stephane Litkowski
<mailto:slitkows.ietf@gmail.com>
Author: Yingzhen Qu
<mailto:yingzhen.qu@futurewei.com>
Author: Acee Lindem
<mailto:acee@cisco.com>
Author: Pushpasis Sarkar
<mailto:pushpasis.ietf@gmail.com>
Author: Jeff Tantsura
<jefftant.ietf@gmail.com>
";
description
"This YANG module defines a generic framework for Segment
Routing (SR). It is to be augmented by models for different
SR data planes.
This YANG module conforms to the Network Management
Datastore Architecture (NMDA), as described in RFC 8242.
The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL
NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'NOT RECOMMENDED',
'MAY', and 'OPTIONAL' in this document are to be interpreted as
described in BCP 14 (RFC 2119) (RFC 8174) when, and only when,
they appear in all capitals, as shown here.
Copyright (c) 2021 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 9020;
see the RFC itself for full legal notices.";
reference
"RFC 9020: YANG Data Model for Segment Routing.";
revision 2021-05-26 {
description
"Initial version";
reference
"RFC 9020: YANG Data Model for Segment Routing.";
}
augment "/rt:routing" {
description
"This module augments the routing data model (RFC 8349)
with Segment Routing (SR).";
container segment-routing {
description
"Segment Routing configuration. This container
is to be augmented by models for different SR
data planes.";
reference
"RFC 8402: Segment Routing Architecture.";
}
}
}
YANG Module for Segment Routing Common Types
ietf-segment-routing-common.yang:
This module defines a collection of generic types and
groupings for SR, as defined in .
module ietf-segment-routing-common {
yang-version 1.1;
namespace
"urn:ietf:params:xml:ns:yang:ietf-segment-routing-common";
prefix sr-cmn;
import ietf-inet-types {
prefix inet;
reference
"RFC 6991: Common YANG Data Types";
}
organization
"IETF SPRING - SPRING Working Group";
contact
"WG Web: <https://datatracker.ietf.org/wg/spring/>
WG List: <mailto:spring@ietf.org>
Author: Stephane Litkowski
<mailto:slitkows.ietf@gmail.com>
Author: Yingzhen Qu
<mailto:yingzhen.qu@futurewei.com>
Author: Acee Lindem
<mailto:acee@cisco.com>
Author: Pushpasis Sarkar
<mailto:pushpasis.ietf@gmail.com>
Author: Jeff Tantsura
<jefftant.ietf@gmail.com>
";
description
"This YANG module defines a collection of generic types and
groupings for Segment Routing (SR), as described in RFC 8402.
This YANG module conforms to the Network Management
Datastore Architecture (NMDA), as described in RFC 8242.
The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL
NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'NOT RECOMMENDED',
'MAY', and 'OPTIONAL' in this document are to be interpreted as
described in BCP 14 (RFC 2119) (RFC 8174) when, and only when,
they appear in all capitals, as shown here.
Copyright (c) 2021 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 9020;
see the RFC itself for full legal notices.";
reference
"RFC 9020: YANG Data Model for Segment Routing";
revision 2021-05-26 {
description
"Initial version";
reference
"RFC 9020: YANG Data Model for Segment Routing";
}
feature sid-last-hop-behavior {
description
"Configurable last-hop behavior.";
reference
"RFC 8660: Segment Routing with the MPLS Data Plane";
}
identity prefix-sid-algorithm {
description
"Base identity for prefix-sid algorithm.";
reference
"RFC 8402: Segment Routing Architecture";
}
identity prefix-sid-algorithm-shortest-path {
base prefix-sid-algorithm;
description
"Shortest Path First (SPF) Prefix-SID algorithm. This
is the default algorithm.";
}
identity prefix-sid-algorithm-strict-spf {
base prefix-sid-algorithm;
description
"This algorithm mandates that the packet is forwarded
according to the ECMP-aware SPF algorithm.";
}
grouping srlr {
description
"Grouping for SR Label Range configuration.";
leaf lower-bound {
type uint32;
description
"Lower value in the label range.";
}
leaf upper-bound {
type uint32;
must '../lower-bound < ../upper-bound' {
error-message
"The upper-bound must be greater than the lower-bound.";
description
"The value must be greater than lower-bound.";
}
description
"Upper value in the label range.";
}
}
grouping srgb {
description
"Grouping for SR Global Label Range.";
list srgb {
key "lower-bound upper-bound";
ordered-by user;
description
"List of global blocks to be advertised.";
uses srlr;
}
}
grouping srlb {
description
"Grouping for SR Local Block Range.";
list srlb {
key "lower-bound upper-bound";
ordered-by user;
description
"List of SRLBs.";
uses srlr;
}
}
grouping sid-value-type {
description
"Defines how the SID value is expressed.";
leaf value-type {
type enumeration {
enum index {
description
"The value will be interpreted as an index.";
}
enum absolute {
description
"The value will become interpreted as an absolute
value.";
}
}
default "index";
description
"This leaf defines how the value must be interpreted.";
}
}
grouping prefix-sid {
description
"This grouping defines configuration of a Prefix-SID.";
leaf prefix {
type inet:ip-prefix;
description
"Connected Prefix-SID.";
}
uses prefix-sid-attributes;
}
grouping ipv4-sid {
description
"Grouping for an IPv4 Prefix-SID.";
leaf prefix {
type inet:ipv4-prefix;
description
"Connected IPv4 Prefix-SID.";
}
uses prefix-sid-attributes;
}
grouping ipv6-sid {
description
"Grouping for an IPv6 Prefix-SID.";
leaf prefix {
type inet:ipv6-prefix;
description
"Connected IPv6 Prefix-SID.";
}
uses prefix-sid-attributes;
}
grouping last-hop-behavior {
description
"Defines last-hop behavior.";
leaf last-hop-behavior {
if-feature "sid-last-hop-behavior";
type enumeration {
enum explicit-null {
description
"Use explicit-null for the SID.";
}
enum no-php {
description
"Do not use MPLS Penultimate Hop Popping (PHP)
for the SID.";
}
enum php {
description
"Use MPLS PHP for the SID.";
}
}
description
"Configure last-hop behavior.";
}
}
grouping prefix-sid-attributes {
description
"Grouping for Segment Routing (SR) prefix attributes.";
uses sid-value-type;
leaf start-sid {
type uint32;
mandatory true;
description
"Value associated with prefix. The value must be
interpreted in the context of sid-value-type.";
}
leaf range {
type uint32;
description
"Indicates how many SIDs can be allocated.";
}
leaf algorithm {
type identityref {
base prefix-sid-algorithm;
}
description
"Prefix-SID algorithm.";
}
}
}
YANG Module for Segment Routing MPLS
ietf-segment-routing-mpls.yang:
This module defines the configuration
and operational states for the Segment Routing MPLS data plane.
module ietf-segment-routing-mpls {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-segment-routing-mpls";
prefix sr-mpls;
import ietf-inet-types {
prefix inet;
reference
"RFC 6991: Common YANG Data Types";
}
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-segment-routing {
prefix sr;
reference
"RFC 9020: YANG Data Model for Segment Routing";
}
import ietf-segment-routing-common {
prefix sr-cmn;
reference
"RFC 9020: YANG Data Model for Segment Routing";
}
organization
"IETF SPRING - SPRING Working Group";
contact
"WG Web: <https://datatracker.ietf.org/wg/spring/>
WG List: <mailto:spring@ietf.org>
Author: Stephane Litkowski
<mailto:slitkows.ietf@gmail.com>
Author: Yingzhen Qu
<mailto:yingzhen.qu@futurewei.com>
Author: Acee Lindem
<mailto:acee@cisco.com>
Author: Pushpasis Sarkar
<mailto:pushpasis.ietf@gmail.com>
Author: Jeff Tantsura
<jefftant.ietf@gmail.com>
";
description
"This YANG module defines a generic configuration model for
the Segment Routing MPLS data plane.
This YANG module conforms to the Network Management
Datastore Architecture (NMDA), as described in RFC 8242.
The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL
NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'NOT RECOMMENDED',
'MAY', and 'OPTIONAL' in this document are to be interpreted as
described in BCP 14 (RFC 2119) (RFC 8174) when, and only when,
they appear in all capitals, as shown here.
Copyright (c) 2021 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 9020;
see the RFC itself for full legal notices.";
reference
"RFC 9020: YANG Data Model for Segment Routing";
revision 2021-05-26 {
description
"Initial version";
reference
"RFC 9020: YANG Data Model for Segment Routing";
}
feature mapping-server {
description
"Support for Segment Routing Mapping Server (SRMS).";
reference
"RFC 8661: Segment Routing MPLS Interworking
with LDP";
}
feature protocol-srgb {
description
"Support for per-protocol Segment Routing Global Block
(SRGB) configuration.";
reference
"RFC 8660: Segment Routing with the MPLS
Data Plane";
}
typedef system-id {
type string {
pattern '[0-9A-Fa-f]{4}\.[0-9A-Fa-f]{4}\.[0-9A-Fa-f]{4}';
}
description
"This type defines an IS-IS system-id using a pattern.
An example system-id is 0143.0438.AEF0.";
}
typedef router-or-system-id {
type union {
type rt-types:router-id;
type system-id;
}
description
"OSPF/BGP router-id or IS-IS system ID.";
}
grouping sr-control-plane {
description
"Defines protocol configuration.";
container segment-routing {
description
"Segment Routing global configuration.";
leaf enabled {
type boolean;
default "false";
description
"Enables Segment Routing control-plane protocol
extensions.";
}
container bindings {
if-feature "mapping-server";
description
"Control of binding advertisement and reception.";
container advertise {
description
"Control advertisement of local mappings
in binding TLVs.";
leaf-list policies {
type leafref {
path "/rt:routing/sr:segment-routing/sr-mpls:sr-mpls"
+ "/sr-mpls:bindings/sr-mpls:mapping-server"
+ "/sr-mpls:policy/sr-mpls:name";
}
description
"List of binding advertisement policies.";
}
}
leaf receive {
type boolean;
default "true";
description
"Allow the reception and usage of binding TLVs.";
}
}
}
}
grouping igp-interface {
description
"Grouping for IGP interface configuration.";
container segment-routing {
description
"Container for SR interface configuration.";
container adjacency-sid {
description
"Adjacency SID (Adj-SID) configuration.";
reference
"RFC 8660: Segment Routing with the MPLS
Data Plane";
list adj-sids {
key "value";
uses sr-cmn:sid-value-type;
leaf value {
type uint32;
description
"Value of the Adj-SID.";
}
leaf protected {
type boolean;
default "false";
description
"It is used to protect the Adj-SID, e.g., using
IP Fast Reroute (IPFRR) or MPLS-FRR.";
}
leaf weight {
type uint8;
description
"The load-balancing factor over parallel adjacencies.";
reference
"RFC 8402: Segment Routing Architecture
RFC 8665: OSPF Extensions for Segment Routing
RFC 8667: IS-IS Extensions for Segment
Routing";
}
description
"List of Adj-SIDs and their configuration.";
}
list advertise-adj-group-sid {
key "group-id";
description
"Control advertisement of S-flag or G-flag. Enable
advertisement of a common Adj-SID for parallel
links.";
reference
"RFC 8665: OSPF Extensions for Segment Routing,
Section 6.1
RFC 8667: IS-IS Extensions for Segment
Routing, Section 2.2.1";
leaf group-id {
type uint32;
description
"The value is an internal value to identify a
group-ID. Interfaces with the same group-ID
will be bundled together.";
}
}
leaf advertise-protection {
type enumeration {
enum single {
description
"A single Adj-SID is associated with the
adjacency and reflects the protection
configuration.";
}
enum dual {
description
"Two Adj-SIDs will be associated with the adjacency
if the interface is protected. In this case, one
Adj-SID will be advertised with the backup-flag
set and the other with the backup-flag clear. In
the case where protection is not configured, a
single Adj-SID will be advertised with the
backup-flag clear.";
}
}
description
"If set, the Adj-SID refers to a protected adjacency.";
reference
"RFC 8665: OSPF Extensions for Segment Routing,
Section 6.1
RFC 8667: IS-IS Extensions for Segment
Routing, Section 2.2.1";
}
}
}
}
augment "/rt:routing/sr:segment-routing" {
description
"This augments the routing data model (RFC 8349)
with Segment Routing (SR) using the MPLS data plane.";
container sr-mpls {
description
"Segment Routing global configuration and
operational state.";
container bindings {
description
"List of bindings.";
container mapping-server {
if-feature "mapping-server";
description
"Configuration of mapping-server local entries.";
list policy {
key "name";
description
"List mapping-server policies.";
leaf name {
type string;
description
"Name of the mapping policy.";
}
container entries {
description
"IPv4/IPv6 mapping entries.";
list mapping-entry {
key "prefix algorithm";
description
"Mapping entries.";
uses sr-cmn:prefix-sid;
}
}
}
}
container connected-prefix-sid-map {
description
"Prefix-SID configuration.";
list connected-prefix-sid {
key "prefix algorithm";
description
"List of mappings of Prefix-SIDs to IPv4/IPv6
local prefixes.";
uses sr-cmn:prefix-sid;
uses sr-cmn:last-hop-behavior;
}
}
container local-prefix-sid {
description
"Local SID configuration.";
list local-prefix-sid {
key "prefix algorithm";
description
"List of local IPv4/IPv6 Prefix-SIDs.";
uses sr-cmn:prefix-sid;
}
}
}
container srgb {
description
"Global SRGB configuration.";
uses sr-cmn:srgb;
}
container srlb {
description
"Segment Routing Local Block (SRLB) configuration.";
uses sr-cmn:srlb;
}
list label-blocks {
config false;
description
"List of label blocks currently in use.";
leaf lower-bound {
type uint32;
description
"Lower bound of the label block.";
}
leaf upper-bound {
type uint32;
description
"Upper bound of the label block.";
}
leaf size {
type uint32;
description
"Number of indexes in the block.";
}
leaf free {
type uint32;
description
"Number of free indexes in the block.";
}
leaf used {
type uint32;
description
"Number of indexes in use in the block.";
}
leaf scope {
type enumeration {
enum global {
description
"Global SID.";
}
enum local {
description
"Local SID.";
}
}
description
"Scope of this label block.";
}
}
container sid-db {
config false;
description
"List of prefix and SID associations.";
list sid {
key "target sid source source-protocol binding-type";
ordered-by system;
description
"SID binding.";
leaf target {
type string;
description
"Defines the target of the binding. It can be a
prefix or something else.";
}
leaf sid {
type uint32;
description
"Index associated with the prefix.";
}
leaf algorithm {
type uint8;
description
"Algorithm to be used for the Prefix-SID.";
reference
"RFC 8665: OSPF Extensions for Segment Routing
RFC 8667: IS-IS Extensions for Segment
Routing
RFC 8669: Segment Routing Prefix Segment
Identifier Extensions to BGP";
}
leaf source {
type inet:ip-address;
description
"IP address of the router that owns the binding.";
}
leaf used {
type boolean;
description
"Indicates if the binding is installed in the
forwarding plane.";
}
leaf source-protocol {
type leafref {
path "/rt:routing/rt:control-plane-protocols/"
+ "rt:control-plane-protocol/rt:name";
}
description
"Routing protocol that owns the binding.";
}
leaf binding-type {
type enumeration {
enum prefix-sid {
description
"Binding is learned from a Prefix-SID.";
}
enum binding-tlv {
description
"Binding is learned from a binding TLV.";
}
}
description
"Type of binding.";
}
leaf scope {
type enumeration {
enum global {
description
"Global SID.";
}
enum local {
description
"Local SID.";
}
}
description
"SID scoping.";
}
}
}
}
}
notification segment-routing-srgb-collision {
description
"This notification is sent when SRGB blocks received from
different routers collide.";
list srgb-collisions {
description
"List of SRGB blocks that collide.";
leaf lower-bound {
type uint32;
description
"Lower value in the block.";
}
leaf upper-bound {
type uint32;
description
"Upper value in the block.";
}
leaf routing-protocol {
type leafref {
path "/rt:routing/rt:control-plane-protocols/"
+ "rt:control-plane-protocol/rt:name";
}
description
"Routing protocol reference for SRGB collision.";
}
leaf originating-rtr-id {
type router-or-system-id;
description
"Originating router ID of this SRGB block.";
}
}
}
notification segment-routing-global-sid-collision {
description
"This notification is sent when a new mapping is learned
containing a mapping where the SID is already used.
The notification generation must be throttled with at least
a 5-second gap between notifications.";
leaf received-target {
type string;
description
"Target received in the router advertisement that caused
the SID collision.";
}
leaf new-sid-rtr-id {
type router-or-system-id;
description
"Router ID that advertised the colliding SID.";
}
leaf original-target {
type string;
description
"Target already available in the database with the same SID
as the received target.";
}
leaf original-sid-rtr-id {
type router-or-system-id;
description
"Router ID for the router that originally advertised the
colliding SID, i.e., the instance in the database.";
}
leaf index {
type uint32;
description
"Value of the index used by two different prefixes.";
}
leaf routing-protocol {
type leafref {
path "/rt:routing/rt:control-plane-protocols/"
+ "rt:control-plane-protocol/rt:name";
}
description
"Routing protocol reference for colliding SID.";
}
}
notification segment-routing-index-out-of-range {
description
"This notification is sent when a binding is received
containing a segment index that is out of the local
configured ranges. The notification generation must be
throttled with at least a 5-second gap between
notifications.";
leaf received-target {
type string;
description
"A human-readable string representing the target
received in the protocol-specific advertisement
corresponding to the out-of-range index.";
}
leaf received-index {
type uint32;
description
"Value of the index received.";
}
leaf routing-protocol {
type leafref {
path "/rt:routing/rt:control-plane-protocols/"
+ "rt:control-plane-protocol/rt:name";
}
description
"Routing protocol reference for out-of-range indexed.";
}
}
}
Security ConsiderationsThe YANG modules specified in this document define 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 the modules
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:
/segment-routing
/segment-routing/mpls
/segment-routing/mpls/bindings -- Modification to the local bindings could result
in a Denial-of-Service (DoS) attack. An attacker may also try to create segment conflicts
(using the same segment identifier for different purposes) to redirect traffic within the
trusted domain. However, the traffic will remain within the trusted domain.
Redirection could be used to route the traffic to compromised nodes within
the trusted domain or to avoid certain security functions (e.g., firewall).
Refer to for a discussion of the SR-MPLS
trusted domain.
/segment-routing/mpls/srgb -- Modification of the Segment Routing Global
Block (SRGB) could be used to mount a DoS attack. For example, if the SRGB
size is reduced to a very small value, a lot of existing segments could no longer
be installed leading to a traffic disruption.
/segment-routing/mpls/srlb -- Modification of the Segment Routing Local Block (SRLB)
could be used to mount a DoS attack similar to those applicable to the SRGB.
Some of the readable data nodes in these YANG modules
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:
/segment-routing/mpls/bindings -- Knowledge of these data nodes can be used to
attack the local router with a Denial-of-Service (DoS) attack.
/segment-routing/mpls/sid-db -- Knowledge of these data nodes can be used to
attack the other routers in the SR domain with either a Denial-of-Service (DoS) attack or redirection traffic destined for those routers.
IANA ConsiderationsThis document registers a URI in the "IETF XML Registry"
. Following the format in ,
the following registration is requested to be made:
ReferencesNormative ReferencesKey words for use in RFCs to Indicate Requirement LevelsIn many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements.The IETF XML RegistryThis document describes an IANA maintained registry for IETF standards which use Extensible Markup Language (XML) related items such as Namespaces, Document Type Declarations (DTDs), Schemas, and Resource Description Framework (RDF) Schemas.YANG - A Data Modeling Language for the Network Configuration Protocol (NETCONF)YANG is a data modeling language used to model configuration and state data manipulated by the Network Configuration Protocol (NETCONF), NETCONF remote procedure calls, and NETCONF notifications. [STANDARDS-TRACK]Network Configuration Protocol (NETCONF)The Network Configuration Protocol (NETCONF) defined in this document provides mechanisms to install, manipulate, and delete the configuration of network devices. It uses an Extensible Markup Language (XML)-based data encoding for the configuration data as well as the protocol messages. The NETCONF protocol operations are realized as remote procedure calls (RPCs). This document obsoletes RFC 4741. [STANDARDS-TRACK]Using the NETCONF Protocol over Secure Shell (SSH)This document describes a method for invoking and running the Network Configuration Protocol (NETCONF) within a Secure Shell (SSH) session as an SSH subsystem. This document obsoletes RFC 4742. [STANDARDS-TRACK]Common YANG Data TypesThis document introduces a collection of common data types to be used with the YANG data modeling language. This document obsoletes RFC 6021.The YANG 1.1 Data Modeling LanguageYANG is a data modeling language used to model configuration data, state data, Remote Procedure Calls, and notifications for network management protocols. This document describes the syntax and semantics of version 1.1 of the YANG language. YANG version 1.1 is a maintenance release of the YANG language, addressing ambiguities and defects in the original specification. There are a small number of backward incompatibilities from YANG version 1. This document also specifies the YANG mappings to the Network Configuration Protocol (NETCONF).RESTCONF ProtocolThis document describes an HTTP-based protocol that provides a programmatic interface for accessing data defined in YANG, using the datastore concepts defined in the Network Configuration Protocol (NETCONF).Ambiguity of Uppercase vs Lowercase in RFC 2119 Key WordsRFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings.Common YANG Data Types for the Routing AreaThis document defines a collection of common data types using the YANG data modeling language. These derived common types are designed to be imported by other modules defined in the routing area.Network Configuration Access Control ModelThe standardization of network configuration interfaces for use with the Network Configuration Protocol (NETCONF) or the RESTCONF protocol requires a structured and secure operating environment that promotes human usability and multi-vendor interoperability. There is a need for standard mechanisms to restrict NETCONF or RESTCONF protocol access for particular users to a preconfigured subset of all available NETCONF or RESTCONF protocol operations and content. This document defines such an access control model.This document obsoletes RFC 6536.Network Management Datastore Architecture (NMDA)Datastores are a fundamental concept binding the data models written in the YANG data modeling language to network management protocols such as the Network Configuration Protocol (NETCONF) and RESTCONF. This document defines an architectural framework for datastores based on the experience gained with the initial simpler model, addressing requirements that were not well supported in the initial model. This document updates RFC 7950.A YANG Data Model for Interface ManagementThis document defines a YANG data model for the management of network interfaces. It is expected that interface-type-specific data models augment the generic interfaces data model defined in this document. The data model includes definitions for configuration and system state (status information and counters for the collection of statistics).The YANG data model in this document conforms to the Network Management Datastore Architecture (NMDA) defined in RFC 8342.This document obsoletes RFC 7223.A YANG Data Model for Routing Management (NMDA Version)This document specifies three YANG modules and one submodule. Together, they form the core routing data model that serves as a framework for configuring and managing a routing subsystem. It is expected that these modules will be augmented by additional YANG modules defining data models for control-plane protocols, route filters, and other functions. The core routing data model provides common building blocks for such extensions -- routes, Routing Information Bases (RIBs), and control-plane protocols.The YANG modules in this document conform to the Network Management Datastore Architecture (NMDA). This document obsoletes RFC 8022.Segment Routing ArchitectureSegment Routing (SR) leverages the source routing paradigm. A node steers a packet through an ordered list of instructions, called "segments". A segment can represent any instruction, topological or service based. A segment can have a semantic local to an SR node or global within an SR domain. SR provides a mechanism that allows a flow to be restricted to a specific topological path, while maintaining per-flow state only at the ingress node(s) to the SR domain.SR can be directly applied to the MPLS architecture with no change to the forwarding plane. A segment is encoded as an MPLS label. An ordered list of segments is encoded as a stack of labels. The segment to process is on the top of the stack. Upon completion of a segment, the related label is popped from the stack.SR can be applied to the IPv6 architecture, with a new type of routing header. A segment is encoded as an IPv6 address. An ordered list of segments is encoded as an ordered list of IPv6 addresses in the routing header. The active segment is indicated by the Destination Address (DA) of the packet. The next active segment is indicated by a pointer in the new routing header.The Transport Layer Security (TLS) Protocol Version 1.3This document specifies version 1.3 of the Transport Layer Security (TLS) protocol. TLS allows client/server applications to communicate over the Internet in a way that is designed to prevent eavesdropping, tampering, and message forgery.This document updates RFCs 5705 and 6066, and obsoletes RFCs 5077, 5246, and 6961. This document also specifies new requirements for TLS 1.2 implementations.Segment Routing with the MPLS Data PlaneSegment Routing (SR) leverages the source-routing paradigm. A node steers a packet through a controlled set of instructions, called segments, by prepending the packet with an SR header. In the MPLS data plane, the SR header is instantiated through a label stack. This document specifies the forwarding behavior to allow instantiating SR over the MPLS data plane (SR-MPLS).Segment Routing MPLS Interworking with LDPA Segment Routing (SR) node steers a packet through a controlled set of instructions, called segments, by prepending the packet with an SR header. A segment can represent any instruction, topological or service based. SR allows enforcing a flow through any topological path while maintaining per-flow state only at the ingress node to the SR domain.The Segment Routing architecture can be directly applied to the MPLS data plane with no change in the forwarding plane. This document describes how Segment Routing MPLS operates in a network where LDP is deployed and in the case where SR-capable and non-SR-capable nodes coexist.OSPF Extensions for Segment RoutingSegment Routing (SR) allows a flexible definition of end-to-end paths within IGP topologies by encoding paths as sequences of topological subpaths called "segments". These segments are advertised by the link-state routing protocols (IS-IS and OSPF).This document describes the OSPFv2 extensions required for Segment Routing.IS-IS Extensions for Segment RoutingSegment Routing (SR) allows for a flexible definition of end-to-end paths within IGP topologies by encoding paths as sequences of topological sub-paths, called "segments". These segments are advertised by the link-state routing protocols (IS-IS and OSPF).This document describes the IS-IS extensions that need to be introduced for Segment Routing operating on an MPLS data plane.Segment Routing Prefix Segment Identifier Extensions for BGPSegment Routing (SR) leverages the source-routing paradigm. A node steers a packet through an ordered list of instructions called "segments". A segment can represent any instruction, topological or service based. The ingress node prepends an SR header to a packet containing a set of segment identifiers (SIDs). Each SID represents a topological or service-based instruction. Per-flow state is maintained only on the ingress node of the SR domain. An "SR domain" is defined as a single administrative domain for global SID assignment.This document defines an optional, transitive BGP attribute for announcing information about BGP Prefix Segment Identifiers (BGP Prefix-SIDs) and the specification for SR-MPLS SIDs.Signaling Maximum SID Depth (MSD) Using the Border Gateway Protocol - Link StateThis document defines a way for a Border Gateway Protocol - Link State (BGP-LS) speaker to advertise multiple types of supported Maximum SID Depths (MSDs) at node and/or link granularity.Such advertisements allow entities (e.g., centralized controllers) to determine whether a particular Segment Identifier (SID) stack can be supported in a given network.Extensible Markup Language (XML) 1.1 (Second Edition)Informative ReferencesYANG Tree DiagramsThis document captures the current syntax used in YANG module tree diagrams. The purpose of this document is to provide a single location for this definition. This syntax may be updated from time to time based on the evolution of the YANG language.Handling Long Lines in Content of Internet-Drafts and RFCsThis document defines two strategies for handling long lines in width-bounded text content. One strategy, called the "single backslash" strategy, is based on the historical use of a single backslash ('\') character to indicate where line-folding has occurred, with the continuation occurring with the first character that is not a space character (' ') on the next line. The second strategy, called the "double backslash" strategy, extends the first strategy by adding a second backslash character to identify where the continuation begins and is thereby able to handle cases not supported by the first strategy. Both strategies use a self-describing header enabling automated reconstitution of the original content.Configuration ExamplesNote: '\' line wrapping per .SR-MPLS with IPv4The following is an XML example using the SR-MPLS YANG modules with IPv4 addresses.
<routing xmlns="urn:ietf:params:xml:ns:yang:ietf-routing">
<segment-routing
xmlns="urn:ietf:params:xml:ns:yang:ietf-segment-routing">
<sr-mpls
xmlns="urn:ietf:params:xml:ns:yang:ietf-segment-routing-mpls">
<bindings>
<mapping-server>
<policy>
<name>mapping 1</name>
<entries>
<mapping-entry>
<prefix>198.51.100.0/24</prefix>
<algorithm xmlns:sr-cmn="urn:ietf:params:xml:ns:yang\
:ietf-segment-routing-common">\
sr-cmn:prefix-sid-algorithm-shortest-path\
</algorithm>
<start-sid>200</start-sid>
<range>100</range>
</mapping-entry>
</entries>
</policy>
</mapping-server>
<connected-prefix-sid-map>
<connected-prefix-sid>
<prefix>192.0.2.0/24</prefix>
<algorithm xmlns:sr-cmn="urn:ietf:params:xml:ns:yang:\
ietf-segment-routing-common">\
sr-cmn:prefix-sid-algorithm-strict-spf</algorithm>
<start-sid>100</start-sid>
<range>1</range>
<last-hop-behavior>php</last-hop-behavior>
</connected-prefix-sid>
</connected-prefix-sid-map>
</bindings>
<srgb>
<srgb>
<lower-bound>45000</lower-bound>
<upper-bound>55000</upper-bound>
</srgb>
</srgb>
</sr-mpls>
</segment-routing>
</routing>
The following is the same example using JSON format.
{
"ietf-routing:routing": {
"ietf-segment-routing:segment-routing": {
"ietf-segment-routing-mpls:sr-mpls": {
"bindings": {
"mapping-server": {
"policy": [
{
"name": "mapping 1",
"entries": {
"mapping-entry": [
{
"prefix": "198.51.100.0/24",
"algorithm": "ietf-segment-routing-common:\
prefix-sid-algorithm-shortest-path",
"start-sid": 200,
"range": 100
}
]
}
}
]
},
"connected-prefix-sid-map": {
"connected-prefix-sid": [
{
"prefix": "192.0.2.0/24",
"algorithm": "ietf-segment-routing-common:\
prefix-sid-algorithm-strict-spf",
"start-sid": 100,
"range": 1,
"last-hop-behavior": "php"
}
]
}
},
"srgb": {
"srgb": [
{
"lower-bound": 45000,
"upper-bound": 55000
}
]
}
}
}
}
}
SR-MPLS with IPv6The following is an XML example using the SR-MPLS YANG modules with IPv6 addresses.
<routing xmlns="urn:ietf:params:xml:ns:yang:ietf-routing">
<segment-routing
xmlns="urn:ietf:params:xml:ns:yang:ietf-segment-routing">
<sr-mpls
xmlns="urn:ietf:params:xml:ns:yang:ietf-segment-routing-mpls">
<bindings>
<mapping-server>
<policy>
<name>mapping 1</name>
<entries>
<mapping-entry>
<prefix>2001:db8:aaaa:bbbb::/64</prefix>
<algorithm xmlns:sr-cmn="urn:ietf:params:xml:ns:yang\
:ietf-segment-routing-common">\
sr-cmn:prefix-sid-algorithm-shortest-path\
</algorithm>
<start-sid>200</start-sid>
<range>100</range>
</mapping-entry>
</entries>
</policy>
</mapping-server>
<connected-prefix-sid-map>
<connected-prefix-sid>
<prefix>2001:db8:aaaa:cccc::/64</prefix>
<algorithm xmlns:sr-cmn="urn:ietf:params:xml:ns:yang:\
ietf-segment-routing-common">\
sr-cmn:prefix-sid-algorithm-strict-spf</algorithm>
<start-sid>100</start-sid>
<range>1</range>
<last-hop-behavior>php</last-hop-behavior>
</connected-prefix-sid>
</connected-prefix-sid-map>
</bindings>
<srgb>
<srgb>
<lower-bound>45000</lower-bound>
<upper-bound>55000</upper-bound>
</srgb>
</srgb>
</sr-mpls>
</segment-routing>
</routing>
The following is the same example using JSON format.
{
"ietf-routing:routing": {
"ietf-segment-routing:segment-routing": {
"ietf-segment-routing-mpls:sr-mpls": {
"bindings": {
"mapping-server": {
"policy": [
{
"name": "mapping 1",
"entries": {
"mapping-entry": [
{
"prefix": "2001:db8:aaaa:bbbb::/64",
"algorithm": "ietf-segment-routing-common:\
prefix-sid-algorithm-shortest-path",
"start-sid": 200,
"range": 100
}
]
}
}
]
},
"connected-prefix-sid-map": {
"connected-prefix-sid": [
{
"prefix": "2001:db8:aaaa:cccc::/64",
"algorithm": "ietf-segment-routing-common:\
prefix-sid-algorithm-strict-spf",
"start-sid": 100,
"range": 1,
"last-hop-behavior": "php"
}
]
}
},
"srgb": {
"srgb": [
{
"lower-bound": 45000,
"upper-bound": 55000
}
]
}
}
}
}
}
AcknowledgementsThe authors would like to thank , , , ,
, , and for their contributions.Thanks to and for
their thorough reviews and helpful comments.The authors would like to thank , , and for IESG
review and comments.Authors' AddressesCisco Systemsslitkows.ietf@gmail.comFutureweiyingzhen.qu@futurewei.comCisco Systems301 Mindenhall WayCaryNC27513United States of Americaacee@cisco.comVMware, Incpushpasis.ietf@gmail.comJuniper Networksjefftant.ietf@gmail.com