Internet DRAFT - draft-wilton-netmod-interface-properties
draft-wilton-netmod-interface-properties
Network Working Group R. Wilton, Ed.
Internet-Draft Cisco Systems
Intended status: Standards Track July 3, 2017
Expires: January 4, 2018
Interface Properties for YANG Data Models
draft-wilton-netmod-interface-properties-00
Abstract
This document specifies a better way to restrict interface YANG
schema nodes to only those types of interfaces that the nodes are
applicable to.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on January 4, 2018.
Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
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.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Problem Definition . . . . . . . . . . . . . . . . . . . . . 3
4. Interface Property Identities . . . . . . . . . . . . . . . . 4
5. Potential issues and considerations: . . . . . . . . . . . . 4
6. YANG Modules . . . . . . . . . . . . . . . . . . . . . . . . 4
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
8. Security Considerations . . . . . . . . . . . . . . . . . . . 7
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 7
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
10.1. Normative References . . . . . . . . . . . . . . . . . . 7
10.2. Informative References . . . . . . . . . . . . . . . . . 7
Appendix A. Examples of possible updates to iana-if-types.yang . 7
Appendix B. Example of interface properties usage in ietf-
interfaces-common.yang . . . . . . . . . . . . . . . 10
Appendix C. Example of interface properties usage in ietf-
interfaces-ethernet-like.yang . . . . . . . . . . . 15
Appendix D. Example of interface properties usage in ietf-
interfaces.yang . . . . . . . . . . . . . . . . . . 17
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 21
1. Introduction
This document introduces the concept of generic interface property
identities in YANG [RFC7950] data models to solve the problem of how
to restrict interface configuration and state schema nodes to the
appropriate types of interfaces. E.g., it is desirable to restrict
MAC address configuration and state schema nodes to only those types
of interfaces that use Ethernet framing, and hence for which MAC
address configuration may be applicable. This document defines a set
of common interface property YANG identities (e.g., Ethernet-like),
and proposes that the iana-interface-type identities in iana-if-
type.yang are updated to also derive from the interface property
identities (a backwards compatible change). Interface based YANG
schema nodes can then be made conditional on the interface property
identities rather than being conditional on a hardcoded set of IANA
interface types. This approach also allows newly defined interface
types to reuse published standard interface YANG schema nodes just by
deriving from the appropriate interface property identities, and
without requiring new revisions of those published standard YANG
modules each time a new IANA interface type is defined.
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2. Terminology
This document defines the following terms:
o interface property identity: A YANG identity that defines a
particular generic interface related property that generally
relates to multiple interface type identities defined in iana-
interface-type.yang. An example of such a property is
'Ethernet-like'.
3. Problem Definition
The YANG language offers the "when" statement that can be used to
make nodes conditional on some particular X-Path expression.
In the case, of interface related configuration, the when statement
can be used to explicitly list all the iana-interface-type identities
that an interface's 'type' leaf may take.
However, the current solution is not ideal for several reasons:
o Explicitly listing the interface types is somewhat unwieldy,
particularly in the case that a schema node may apply to many
interfaces. When faced with this scenario, YANG model authors
sometimes decide that it is better to keep the model simple and
just allow the schema node to be used regardless of interface
type.
o Explicly listing the inteface types has the further problem that
the model cannot easily be extended to handle new interface types.
If a new interface type is introduced then to reuse the same
interface related schema nodes requires that all of the applicable
model when statements must be updated to reference the new IANA
interface type identity.
o The current solution does not really work for bespoke vendor
specific interface types. Even though the proprietrary interface
types may be defined in the IANA interface type identity list, it
is unlikely that it would be acceptable to update a standards
based YANG model to reference a proprietrary interface type.
Requiring bespoke interfaces to use separate similar configuration
and state nodes makes the models less generic and more tedious to
use by clients.
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4. Interface Property Identities
This draft introduces "Interface Property Identities". These are a
set of YANG identities that describe properties that could be
associated with multiple different types of interface.
The existing IANA interface type identities are then selectively
updated to also derive from one or more of these interface property
identities. The YANG module upgrade rules in [RFC7950] allow for the
interface type identities to derive from additional identities in a
fully backwards compatible way.
YANG modules that define interface specific nodes can then use the
YANG 1.1 derived-from() macro in the 'when' statement xpath
expression to indicate that the node applies to all interfaces that
inherit from the specified interface property.
As new IANA interface types are defined they can derive from the
interface property identities and hence acquire the interface
specific YANG nodes that have been defined in existing YANG modules
without requiring any changes beyond the device updating to use the
latest iana-if-types YANG file.
Similarly, vendor specific interface types can also inherit from the
interface property identities and also acquire access to the
appropriate interface configuration nodes.
As required, new interface property identities can also be defined,
again in a backwards compatible way.
5. Potential issues and considerations:
o Would IANA be willing to manage the new interface property types?
o iana-interface-types.yang would need to be YANG 1.1. Would this
be an issue?
o Need to define a suitable set of base interface properties.
o Need to then apply the set of base interface properties to
appropriate interface types. Coordination between vendors may be
required to get a reasonable base coverage.
6. YANG Modules
<CODE BEGINS> file "iana-if-property-type@2017-06-27.yang"
module iana-if-property-type {
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namespace "urn:ietf:params:xml:ns:yang:iana-if-property-type";
prefix ianaifp;
organization "IANA";
contact "";
description
"This YANG module defines YANG identities for IANA-registered
interface property types.
This YANG module is maintained by IANA.
The latest revision of this YANG module can be obtained from
the IANA web site.
Requests for new values should be made to IANA via
email (iana&iana.org).
Copyright (c) 2017 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
(http://trustee.ietf.org/license-info).
The initial version of this YANG module is part of XXX;
see the RFC itself for full legal notices.";
reference
"IANA 'interface property definitions' registry.";
revision 2017-06-27 {
description
"Initial revision";
reference
"RFC XXX: IANA Interface Property Type YANG Module";
}
identity iana-if-property-type {
description
"Base identity from which specific interface property types are
derived.";
}
identity physical {
base iana-if-property-type;
description
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"This property represents an interface that has a physical
hardware representation, or is modelled as such.";
}
identity virtual {
base iana-if-property-type;
description
"This property represents an interface that has no external
physical hardware representation, and is used to represent
interfaces that are created via configuration.";
}
identity sub-interface {
base iana-if-property-type;
description
"This property represents an interface that is a child
interface that is parented to another interface.";
}
identity point-to-point {
base iana-if-property-type;
description
"This property represents an interface that is always
point-to-point, i.e. the interface can only ever be connected
to a single other interface, and hence broadcast and multicast
packet statistics do not make sense.";
}
identity multicast {
base iana-if-property-type;
description
"This property represents an interface that could have multiple
end points, e.g. like an Ethernet interface. Such an
interface could have separate broadcast and multicast packet
counters.";
}
identity ethernet-like {
base iana-if-property-type;
description
"This property represents an interface that is similar in
behaviour to an Ethernet interface, and uses Ethernet
framing.";
}
}
<CODE ENDS>
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7. IANA Considerations
This draft proposes that IANA also manage a new registry of
"interface properties" alongside the existing "interface type"
registry, and to
extend the "interface type" registry to also derive from interface
properties identities.
8. Security Considerations
This document discusses an approach how to structure interface
related YANG schema. It has no security impact on the Internet.
9. Acknowledgments
This document arose from discussions with Martin Bjorklund, Ladislav
Lhotka, and Vladimir Vassilev on the Netmod WG alias.
10. References
10.1. Normative References
[RFC7224] Bjorklund, M., "IANA Interface Type YANG Module",
RFC 7224, DOI 10.17487/RFC7224, May 2014,
<http://www.rfc-editor.org/info/rfc7224>.
[RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
RFC 7950, DOI 10.17487/RFC7950, August 2016,
<http://www.rfc-editor.org/info/rfc7950>.
10.2. Informative References
[RFC7223] Bjorklund, M., "A YANG Data Model for Interface
Management", RFC 7223, DOI 10.17487/RFC7223, May 2014,
<http://www.rfc-editor.org/info/rfc7223>.
Appendix A. Examples of possible updates to iana-if-types.yang
The example-iana-if-type.yang module illustrates the type of updates
that would be made to iana-if-types.yang to make use of interface
properties.
<CODE BEGINS> file "example-iana-if-type@2017-06-27.yang"
module example-iana-if-type {
yang-version "1.1";
namespace "urn:ietf:params:xml:ns:yang:example-iana-if-type";
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prefix ianaift;
import ietf-interfaces {
prefix if;
}
import iana-if-property-type {
prefix ianaifp;
}
// Full description, etc elided for clarity.
organization "IANA";
contact "";
description
"This example module illustrates how iana-if-type.yang could
be extended to use interface properties.";
reference
"IANA 'ifType definitions' registry.
<http://www.iana.org/assignments/smi-numbers>";
revision 2017-06-27 {
description
"Initial example of how IANA if type could be extended";
reference
"Taken from draft-rwilton-netmod-interface-properties-00";
}
// Previous revision statements elided for clarity.
identity iana-interface-type {
base if:interface-type;
description
"This identity is used as a base for all interface types
defined in the 'ifType definitions' registry.";
}
// Most identies elided for clarity, some are retained to
// illustrate how the interface properties are defined.
identity other {
base iana-interface-type;
description
"None of the following";
}
identity ethernetCsmacd {
base iana-interface-type;
base ianaifp:physical;
base ianaifp:multicast;
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base ianaifp:ethernet-like;
description
"For all Ethernet-like interfaces, regardless of speed,
as per RFC 3635.";
reference
"RFC 3635 - Definitions of Managed Objects for the
Ethernet-like Interface Types";
}
identity ieee8023adLag {
base iana-interface-type;
base ianaifp:virtual;
base ianaifp:multicast;
base ianaifp:ethernet-like;
description
"IEEE 802.3ad Link Aggregate.";
}
identity atm {
base iana-interface-type;
base ianaifp:physical;
base ianaifp:multicast;
description
"ATM cells.";
}
identity atmSubInterface {
base iana-interface-type;
base ianaifp:virtual;
base ianaifp:sub-interface;
base ianaifp:multicast;
description
"ATM Sub Interface.";
}
identity l2vlan {
base iana-interface-type;
base ianaifp:virtual;
base ianaifp:sub-interface;
base ianaifp:multicast;
description
"Layer 2 Virtual LAN using 802.1Q.";
}
identity pos {
base iana-interface-type;
base ianaifp:point-to-point;
description
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"Packet over SONET/SDH Interface.";
}
identity irb {
base iana-interface-type;
base ianaifp:virtual;
base ianaifp:multicast;
base ianaifp:ethernet-like;
description
"Integrated Routing and Bridging interface, also known as an
SVI or BVI interface.
Note, not currently defined in if-type.yang";
}
}
<CODE ENDS>
Appendix B. Example of interface properties usage in ietf-interfaces-
common.yang
The ietf-interfaces-common module defines various interface
configuration nodes that are applicable to different types of
interfaces and hence would benefit from interface properties.
<CODE BEGINS> file "example-ietf-interfaces-common@2017-06-27.yang"
module example-ietf-interfaces-common {
yang-version 1.1;
namespace
"urn:ietf:params:xml:ns:yang:example-ietf-interfaces-common";
prefix if-cmn;
import ietf-interfaces {
prefix if;
}
import iana-if-type {
prefix ianaift;
}
import iana-if-property-type {
prefix ianaifp;
}
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organization
"IETF NETMOD (NETCONF Data Modeling Language) Working Group";
contact
"WG Web: <http://tools.ietf.org/wg/netmod/>
WG List: <mailto:netmod@ietf.org>
WG Chair: Lou Berger
<mailto:lberger@labn.net>
WG Chair: Kent Watsen
<mailto:kwatsen@juniper.net>
Editor: Robert Wilton
<mailto:rwilton@cisco.com>";
description
"Example of using when statements with interface properties";
revision 2017-06-27 {
description
"Examples of using when statements with interface properties";
reference "Internet draft: draft-ietf-netmod-intf-ext-yang-04";
}
feature bandwidth {
description "<description elided>";
reference "Section 3.1 Bandwidth";
}
feature carrier-delay {
description "<description elided>";
reference "Section 3.2 Carrier Delay";
}
feature dampening {
description "<description elided>";
reference "Section 3.3 Dampening";
}
feature loopback {
description "<description elided>";
reference "Section 3.5 Loopback";
}
feature configurable-l2-mtu {
description "<description elided>";
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reference "Section 3.6 MTU";
}
feature sub-interfaces {
description
"This feature indicates that the device supports the
instantiation of sub-interfaces. Sub-interfaces are defined
as logical child interfaces that allow features and forwarding
decisions to be applied to a subset of the traffic processed
on the specified parent interface.";
reference "Section 3.7 Sub-interface";
}
feature forwarding-mode {
description "<description elided>";
reference "Section 3.8 Forwarding Mode";
}
/*
* Define common identities to help allow interface types to be
* assigned properties.
*/
identity loopback {
description "Base identity for interface loopback options";
}
identity loopback-internal {
base loopback;
description "<description elided>";
}
identity loopback-line {
base loopback;
description "<description elided>";
}
identity loopback-connector {
base loopback;
description "<description elided>";
}
/*
* Augments the IETF interfaces model with a leaf to explicitly
* specify the bandwidth available on an interface.
*/
augment "/if:interfaces/if:interface" {
description
"Augments the IETF interface model with optional common
interface level commands that are not formally covered by any
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specific standard";
// Various features/nodes elided.
/*
* Various types of interfaces support a configurable layer 2
* encapsulation, any that are supported by YANG should be
* listed here.
*
* Different encapsulations can hook into the common encaps-type
* choice statement.
*/
container encapsulation {
when
"derived-from-or-self(../if:type, 'ianaifp:ethernet-like') or
derived-from-or-self(../if:type, 'ianaifp:sub-interface')" {
description
"All interface types that can have a configurable L2
encapsulation";
/*
* TODO - Should we introduce an abstract type to make this
* extensible to new interface types, or vendor
* specific interface types?
*/
}
description
"Holds the OSI layer 2 encapsulation associated with an
interface";
choice encaps-type {
description "Extensible choice of L2 encapsulations";
}
}
/*
* Various types of interfaces support loopback configuration,
* any that are supported by YANG should be listed here.
*/
leaf loopback {
when "derived-from(if:type, 'ianaifp:physical')" {
description
"Applies to all interfaces that derive from the physical
interface property.";
}
if-feature "loopback";
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type identityref {
base loopback;
}
description "Enables traffic loopback.";
}
/*
* Many types of interfaces support a configurable layer 2 MTU.
*/
leaf l2-mtu {
if-feature "configurable-l2-mtu";
type uint16 {
range "64 .. 65535";
}
description
"The maximum size of layer 2 frames that may be transmitted
or received on the interface (excluding any FCS overhead).
In the case of Ethernet interfaces it also excludes the
4-8 byte overhead of any known (i.e. explicitly matched by
a child sub-interface) 801.1Q VLAN tags.";
}
}
/*
* Add generic support for sub-interfaces.
*
* This should be extended to cover all interface types that are
* child interfaces of other interfaces.
*/
augment "/if:interfaces/if:interface" {
when "derived-from(if:type, 'ianaifp:sub-interface')" {
description
"Applies to all interfaces that derive from the Ethernet-like
interface property.";
}
if-feature "sub-interfaces";
description
"Add a parent interface field to interfaces that model
sub-interfaces";
leaf parent-interface {
type if:interface-ref;
mandatory true;
description
"This is the reference to the parent interface of this
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sub-interface.";
}
}
}
<CODE ENDS>
Appendix C. Example of interface properties usage in ietf-interfaces-
ethernet-like.yang
The ietf-interfaces-ethernet-like module defines various interface
configuration nodes that are applicable to any interfaces that have
"Ethernet-like" semantics, and hence would benefit from interface
properties.
<CODE BEGINS> file "example-ietf-interfaces-ethernet-
like@2017-06-27.yang"
module example-ietf-interfaces-ethernet-like {
yang-version 1.1;
namespace
"urn:ietf:params:xml:ns:yang:" +
"example-ietf-interfaces-ethernet-like";
prefix ethlike;
import ietf-interfaces {
prefix if;
}
import ietf-yang-types {
prefix yang;
}
import iana-if-property-type {
prefix ianaifp;
}
organization
"IETF NETMOD (NETCONF Data Modeling Language) Working Group";
contact
"WG Web: <http://tools.ietf.org/wg/netmod/>
WG List: <mailto:netmod@ietf.org>
WG Chair: Lou Berger
<mailto:lberger@labn.net>
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WG Chair: Kent Watsen
<mailto:kwatsen@juniper.net>
Editor: Robert Wilton
<mailto:rwilton@cisco.com>";
description
"Example for when statements using interface properties.";
revision 2017-06-27 {
description
"Examples of using when statements with interface properties";
reference "Internet draft: draft-ietf-netmod-intf-ext-yang-04";
}
/*
* Configuration parameters for Ethernet-like interfaces.
*/
augment "/if:interfaces/if:interface" {
when "derived-from(if:type, 'ianaifp:ethernet-like')" {
description
"Applies to all interfaces that derive from the Ethernet-like
interface property.";
}
description
"Augment the interface model with configuration parameters for
all Ethernet-like interfaces";
container ethernet-like {
description "Contains configuration parameters for interfaces
that use Ethernet framing and expose an Ethernet
MAC layer.";
leaf mac-address {
type yang:mac-address;
description
"The configured MAC address of the interface.";
}
}
}
/*
* Operational state for Ethernet-like interfaces.
*/
augment "/if:interfaces-state/if:interface" {
when "derived-from(if:type, 'ianaifp:ethernet-like')" {
description
"Applies to all interfaces that derive from the Ethernet-like
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interface property.";
}
description
"Augments the interface model with operational state parameters
for all Ethernet-like interfaces.";
container ethernet-like {
description
"Contains operational state parameters for interfaces that use
Ethernet framing and expose an Ethernet MAC layer.";
leaf mac-address {
type yang:mac-address;
description
"The operational MAC address of the interface, if
applicable";
}
leaf bia-mac-address {
type yang:mac-address;
description
"The 'burnt-in' MAC address. I.e the default MAC address
assigned to the interface if none is explicitly
configured.";
}
container statistics {
description
"Packet statistics that apply to all Ethernet-like
interfaces";
leaf in-drop-unknown-dest-mac-pkts {
type yang:counter64;
units frames;
description "<long description elided>";
}
}
}
}
}
<CODE ENDS>
Appendix D. Example of interface properties usage in ietf-
interfaces.yang
Here is an example of how the ietf-interfaces.yang module could have
used interface properties to restrict multicast packet statistics to
only those interfaces that support it.
<CODE BEGINS> file "example-ietf-interfaces@2017-06-27.yang"
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module example-ietf-interfaces {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:example-ietf-interfaces";
prefix if;
import ietf-yang-types {
prefix yang;
}
import "iana-if-property-type" {
prefix ianaifp;
}
organization
"IETF NETMOD (NETCONF Data Modeling Language) Working Group";
contact "<elided>";
description
"Example of when statements for refining interface statistics";
revision 2017-06-27 {
description
"Example of how some interface statistics could make use of
interface properties";
reference
"RFC 7223: A YANG Data Model for Interface Management";
}
/*
* Typedefs
*/
// interface-ref typedef elided.
typedef interface-state-ref {
type leafref {
path "/if:interfaces-state/if:interface/if:name";
}
description
"This type is used by data models that need to reference
the operationally present interfaces.";
}
/*
* Identities
*/
identity interface-type {
description
"Base identity from which specific interface types are
derived.";
}
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// Features elided.
// Configuration tree elided.
/*
* Operational state data nodes
*/
container interfaces-state {
config false;
description
"Data nodes for the operational state of interfaces.";
list interface {
key "name";
description
"The list of interfaces on the device.
System-controlled interfaces created by the system are
always present in this list, whether they are configured or
not.";
leaf name {
type string;
description
"The name of the interface.
A server implementation MAY map this leaf to the ifName
MIB object. Such an implementation needs to use some
mechanism to handle the differences in size and characters
allowed between this leaf and ifName. The definition of
such a mechanism is outside the scope of this document.";
reference
"RFC 2863: The Interfaces Group MIB - ifName";
}
leaf type {
type identityref {
base interface-type;
}
mandatory true;
description
"The type of the interface.";
reference
"RFC 2863: The Interfaces Group MIB - ifType";
}
// Various leaves elided.
container statistics {
description
"A collection of interface-related statistics objects.";
leaf discontinuity-time {
type yang:date-and-time;
mandatory true;
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description "<description elided>";
}
leaf in-octets {
type yang:counter64;
description "<description elided>";
reference
"RFC 2863: The Interfaces Group MIB - ifHCInOctets";
}
leaf in-unicast-pkts {
type yang:counter64;
description
"The number of packets, delivered by this sub-layer to a
higher (sub-)layer, that were not addressed to a
multicast or broadcast address at this sub-layer.
Discontinuities in the value of this counter can occur
at re-initialization of the management system, and at
other times as indicated by the value of
'discontinuity-time'.";
reference
"RFC 2863: The Interfaces Group MIB - ifHCInUcastPkts";
}
leaf in-broadcast-pkts {
when "derived-from(if:type, 'ianaifp:multicast')" {
description
"Applies to interfaces that inherit the multicast
interface property.";
}
type yang:counter64;
description
"The number of packets, delivered by this sub-layer to a
higher (sub-)layer, that were addressed to a broadcast
address at this sub-layer.
Discontinuities in the value of this counter can occur
at re-initialization of the management system, and at
other times as indicated by the value of
'discontinuity-time'.";
reference
"RFC 2863: The Interfaces Group MIB -
ifHCInBroadcastPkts";
}
leaf in-multicast-pkts {
when "derived-from(if:type, 'ianaifp:multicast')" {
description
"Applies to interfaces that inherit the multicast
interface property.";
}
Wilton Expires January 4, 2018 [Page 20]
Internet-Draft July 2017
type yang:counter64;
description
"The number of packets, delivered by this sub-layer to a
higher (sub-)layer, that were addressed to a multicast
address at this sub-layer. For a MAC-layer protocol,
this includes both Group and Functional addresses.
Discontinuities in the value of this counter can occur
at re-initialization of the management system, and at
other times as indicated by the value of
'discontinuity-time'.";
reference
"RFC 2863: The Interfaces Group MIB -
ifHCInMulticastPkts";
}
// Remaining counters elided.
}
}
}
}
<CODE ENDS>
Author's Address
Robert Wilton (editor)
Cisco Systems
Email: rwilton@cisco.com
Wilton Expires January 4, 2018 [Page 21]
