rfc9144xml2.original.xml   rfc9144.xml 
<?xml version="1.0"?> <?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE rfc SYSTEM "rfc2629.dtd" []>
<?rfc comments="yes"?>
<?rfc compact="no"?>
<?rfc inline="yes"?>
<?rfc sortrefs="yes"?>
<?rfc subcompact="no"?>
<?rfc symrefs="yes"?>
<?rfc toc="yes"?>
<?rfc tocdepth="5"?>
<?rfc tocindent="yes"?>
<?rfc tocompact="yes"?>
<rfc category="std" docName="draft-ietf-netmod-nmda-diff-12" ipr="trust200902"> <!DOCTYPE rfc [
<!ENTITY nbsp "&#160;">
<!ENTITY zwsp "&#8203;">
<!ENTITY nbhy "&#8209;">
<!ENTITY wj "&#8288;">
]>
<front> <rfc xmlns:xi="http://www.w3.org/2001/XInclude" docName="draft-ietf-netmod-nmda-
<title abbrev="">Comparison of NMDA datastores</title> diff-12" number="9144" ipr="trust200902" obsoletes="" updates="" submissionType=
"IETF" category="std" consensus="true" xml:lang="en" sortRefs="true" symRefs="tr
ue" tocInclude="true" tocDepth="5"
version="3">
<author fullname="Alexander Clemm" initials="A." <front>
surname="Clemm"> <title abbrev="NMDA Datastores">Comparison of Network Management Datastore A
<organization>Futurewei</organization> rchitecture (NMDA) Datastores</title>
<address> <seriesInfo name="RFC" value="9144"/>
<author fullname="Alexander Clemm" initials="A." surname="Clemm">
<organization>Futurewei</organization>
<address>
<postal> <postal>
<street>2330 Central Expressway</street> <street>2330 Central Expressway</street>
<city>Santa Clara,</city> <city>Santa Clara</city>
<country>USA</country> <region>CA</region>
<code>CA 95050</code> <country>United States of America</country>
<code>95050</code>
</postal> </postal>
<phone></phone> <phone/>
<email>ludwig@clemm.org</email> <email>ludwig@clemm.org</email>
</address> </address>
</author> </author>
<author fullname="Yingzhen Qu" initials="Y." surname="Qu">
<author fullname="Yingzhen Qu" initials="Y." <organization>Futurewei</organization>
surname="Qu"> <address>
<organization>Futurewei</organization>
<address>
<postal> <postal>
<street>2330 Central Expressway</street> <street>2330 Central Expressway</street>
<city>Santa Clara,</city> <city>Santa Clara</city>
<country>USA</country> <region>CA</region>
<code>CA 95050</code> <country>United States of America</country>
<code>95050</code>
</postal> </postal>
<phone></phone> <phone/>
<email>yqu@futurewei.com</email> <email>yqu@futurewei.com</email>
</address> </address>
</author> </author>
<author fullname="Jeff Tantsura" initials="J." surname="Tantsura">
<author fullname="Jeff Tantsura" initials="J." <organization>Microsoft</organization>
surname="Tantsura"> <address>
<organization>Microsoft</organization>
<address>
<email>jefftant.ietf@gmail.com</email> <email>jefftant.ietf@gmail.com</email>
</address> </address>
</author> </author>
<author fullname="Andy Bierman" initials="A." surname="Bierman">
<author fullname="Andy Bierman" initials="A." <organization>YumaWorks</organization>
surname="Bierman"> <address>
<organization>YumaWorks</organization>
<address>
<email>andy@yumaworks.com</email> <email>andy@yumaworks.com</email>
</address> </address>
</author> </author>
<date /> <date year="2021" month="December" />
<abstract>
<t>
This document defines an RPC operation to compare management datastores
that comply with the NMDA architecture.
</t>
</abstract>
</front>
<middle> <keyword>Troubleshooting</keyword>
<section anchor="intro" title="Introduction"> <keyword>YANG RPC</keyword>
<keyword>YANG Data Model</keyword>
<t> <abstract>
The revised Network Management Datastore Architecture (NMDA) <xref t <t>
arget="RFC8342"/> introduces a set of new datastores that each hold YANG-defined This document defines a Remote Procedure Call (RPC) operation to compare
data <xref target="RFC7950"/> and represent a different “viewpoint” on the data management datastores that comply with the Network Management Datastore Archite
that is maintained by a server. New YANG datastores that are introduced include cture (NMDA).
&lt;intended&gt;, which contains validated configuration data that a client app </t>
lication intends to be in effect, and &lt;operational&gt;, which contains operat </abstract>
ional state data (such as statistics) as well as configuration data that is actu </front>
ally in effect. <middle>
</t> <section anchor="intro" numbered="true" toc="default">
<t> <name>Introduction</name>
NMDA introduces in effect a concept of “lifecycle” for management da <t>
ta, distinguishing between data that is part of a configuration that was supplie The revised NMDA <xref target="RFC8342" format="default"/> introduce
d by a user, configuration data that has actually been successfully applied and s a set of new datastores that each hold YANG-defined data <xref target="RFC7950
that is part of the operational state, and overall operational state that includ " format="default"/> and represent a different "viewpoint" on the data that is m
es applied configuration data as well as status and statistics. aintained by a server. New YANG datastores that are introduced include &lt;inten
</t> ded&gt;, which contains validated configuration data that a client application i
<t> ntends to be in effect, and &lt;operational&gt;, which contains operational stat
e data (such as statistics) as well as configuration data that is actually in ef
fect.
</t>
<t>
NMDA introduces, in effect, a concept of "lifecycle" for management
data, distinguishing between data that is part of a configuration that was suppl
ied by a user, configuration data that has actually been successfully applied an
d that is part of the operational state, and the overall operational state that
includes applied configuration data as well as status and statistics.
</t>
<t>
As a result, data from the same management model can be reflected in multiple datastores. Clients need to specify the target datastore to be specif ic about As a result, data from the same management model can be reflected in multiple datastores. Clients need to specify the target datastore to be specif ic about
which viewpoint of the data they want to access. For example, a cli which viewpoint of the data they want to access. For example, a cli
ent application can differentiate whether they are interested in the configurati ent application can differentiate whether they are interested in the configurati
on supplied to a server and that is supposed to be in effect, or the configurati on that is supplied to a server and is supposed to be in effect or the configura
on that has been applied and is actually in effect on the server. tion that has been applied and is actually in effect on the server.
</t> </t>
<t>Due to the fact that data can propagate from one datastore to ano <t>Due to the fact that data can propagate from one datastore to another,
ther, it is possible for differences between datastores to occur. Some of this it is possible for differences between datastores to occur. Some of this is ent
is entirely expected, as there may be a time lag between when a configuration is irely expected, as there may be a time lag between when a configuration is given
given to the device and reflected in &lt;intended&gt;, until when it actually t to the device and reflected in &lt;intended&gt; until when it actually takes ef
akes effect and is reflected in &lt;operational&gt;. However, there may be case fect and is reflected in &lt;operational&gt;. However, there may be cases when
s when a configuration item that was to be applied may not actually take effect a configuration item that was to be applied may not actually take effect at all
at all or needs an unusually long time to do so. This can be the case due to ce or needs an unusually long time to do so. This can be the case due to certain c
rtain conditions not being met, certain parts of the configuration not propagati onditions not being met, certain parts of the configuration not propagating beca
ng because they are considered inactive, resource dependencies not being resolve use they are considered inactive, resource dependencies not being resolved, or e
d, or even implementation errors in corner conditions. ven implementation errors in corner conditions.
</t> </t>
<t>When configuration that is in effect is different from configurat <t>When the configuration that is in effect is different from the configur
ion that was applied, many issues can result. It becomes more difficult to oper ation that was applied, many issues can result. It becomes more difficult to op
ate the network properly due to limited visibility of actual operational status erate the network properly due to limited visibility of the actual operational s
which makes it more difficult to analyze and understand what is going on in the tatus, which makes it more difficult to analyze and understand what is going on
network. Services may be negatively affected (for example, degrading or breakin in the network. Services may be negatively affected (for example, degrading or
g a customer service) and network resources may be misallocated. breaking a customer service), and network resources may be misallocated.
</t> </t>
<t> <t>
Applications can potentially analyze any differences between two dat Applications can potentially analyze any differences between two dat
astores by retrieving the contents from both datastores and comparing them. How astores by retrieving the contents from both datastores and comparing them. How
ever, in many cases this will be at the same time costly and extremely wasteful. ever, in many cases, this will be both costly and extremely wasteful.
</t> </t>
<t> <t>
This document introduces a YANG data model which defines RPCs, inten This document introduces a YANG data model that defines RPCs
ded to be used in conjunction with NETCONF <xref target="RFC6241"/> or RESTCONF intended to be used in conjunction with NETCONF <xref target="RFC6241" format
<xref target="RFC8040"/>, that allow a client to request a server to compare two ="default"/> or RESTCONF <xref target="RFC8040" format="default"/>. These RPCs a
NMDA datastores and report any differences. llow a client to request a server to compare two NMDA datastores and report any
</t> differences.
</t>
</section>
<section numbered="true" toc="default">
<name>Key Words</name>
<t>
The key words "<bcp14>MUST</bcp14>", "<bcp14>MUST NOT</bcp14>", "<bcp14>REQU
IRED</bcp14>", "<bcp14>SHALL</bcp14>", "<bcp14>SHALL
NOT</bcp14>", "<bcp14>SHOULD</bcp14>", "<bcp14>SHOULD NOT</bcp14>", "<bcp14>
RECOMMENDED</bcp14>", "<bcp14>NOT RECOMMENDED</bcp14>",
"<bcp14>MAY</bcp14>", and "<bcp14>OPTIONAL</bcp14>" in this document are to
be interpreted as
described in BCP&nbsp;14 <xref target="RFC2119"/> <xref target="RFC8174"/>
when, and only when, they appear in all capitals, as shown here.
</t>
</section> </section>
<section title="Key Words"> <section anchor="Overview" numbered="true" toc="default">
<t>The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL <name>Data Model Overview</name>
NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", <t>
"MAY", and "OPTIONAL" in this document are to be interpreted as The core of the solution is a new management operation, &lt;compare&gt;, tha
described in BCP 14 <xref target="RFC2119"/> <xref target="RFC8174"/> t compares the data tree contents of two datastores. The operation checks wheth
when, and only when, they er there are any differences in values or in data nodes that are contained in ei
appear in all capitals, as shown here. ther datastore and returns any differences as output. The output is returned in
</t> the format specified in YANG Patch <xref target="RFC8072" format="default"/>.
</section> </t>
<t>
<section title="Definitions and Acronyms">
<t>
<list style="empty">
<t>NMDA: Network Management Datastore Architecture</t>
<t>RPC: Remote Procedure Call</t>
</list>
</t>
</section>
<section title="Data Model Overview" anchor="Overview">
<t>
The core of the solution is a new management operation, &lt;compare&gt;, tha
t compares the data tree contents of two datastores. The operation checks wheth
er there are any differences in values or in data nodes that are contained in ei
ther datastore, and returns any differences as output. The output is returned i
n the format specified in YANG-Patch <xref target="RFC8072"/>.
</t>
<t>
The YANG data model defines the &lt;compare&gt; operation as a new RPC. The operation takes the following input parameters: The YANG data model defines the &lt;compare&gt; operation as a new RPC. The operation takes the following input parameters:
<list style="symbols"> </t>
<t>source: The source identifies the datastore that will serve as the re <dl spacing="normal">
ference for the comparison, for example &lt;intended&gt;.</t> <dt>source:</dt><dd> The source identifies the datastore to serve as the
<t>target: The target identifies the datastore to compare against the so reference for the comparison -- for example, &lt;intended&gt;.</dd>
urce, for example &lt;operational&gt;.</t> <dt>target:</dt><dd> The target identifies the datastore to compare agai
<t>filter-spec: This is a choice between different filter constructs to nst the source -- for example, &lt;operational&gt;.</dd>
identify the parts of the datastore to be retrieved. It acts as a node selector <dt>filter-spec:</dt><dd> This is a choice between different filter cons
that specifies which data nodes are within the scope of the comparison and whic tructs to identify the parts of the datastore to be retrieved. It acts as a nod
h nodes are outside the scope. This allows a comparison operation to be applied e selector that specifies which data nodes are within the scope of the compariso
only to a specific part of the datastore that is of interest, such as a particu n and which nodes are outside the scope. This allows a comparison operation to
lar subtree. Note, the filter does not allow expressions that match against dat be applied only to a specific part of the datastore that is of interest, such as
a node values, since this may incur implementation difficulties and is not requi a particular subtree. Note that the filter does not allow expressions that mat
red for normal use cases. </t> ch against data node values, since this may incur implementation difficulties an
<t>all: When set, this parameter indicates that all differences should d is not required for normal use cases. </dd>
be included, including differences pertaining to schema nodes that exist in only <dt>all:</dt><dd> When set, this parameter indicates that all difference
one of the datastores. When this parameter is not included, a prefiltering ste s should be included, including differences pertaining to schema nodes that exis
p is automatically applied to exclude data from the comparison that does not per t in only one of the datastores. When this parameter is not included, a prefilt
tain to both datastores: if the same schema node is not present in both datastor ering step is automatically applied to exclude data from the comparison that doe
es, then all instances of that schema node and all its descendants are excluded s not pertain to both datastores: if the same schema node is not present in both
from the comparison. This allows client applications to focus on the differences datastores, then all instances of that schema node and all its descendants are
that constitute true mismatches of instance data without needing to specify mor excluded from the comparison. This allows client applications to focus on the di
e complex filter constructs.</t> fferences that constitute true mismatches of instance data without needing to sp
<t>report-origin: When set, this parameter indicates that origin metadat ecify more complex filter constructs.</dd>
a should be included as part of RPC output. <dt>report-origin:</dt><dd> When set, this parameter indicates that orig
in metadata should be included as part of RPC output.
When this parameter is omitted, origin metadata in comparisons that invo lve When this parameter is omitted, origin metadata in comparisons that invo lve
&lt;operational&gt; is by default omitted. &lt;operational&gt; is by default omitted.
Note that origin metadata only applies to &lt;operational&gt; it is ther Note that origin metadata only applies to &lt;operational&gt;; it is the
efore also omitted in comparisons that do not involve &lt;operational&gt; regard refore also omitted in comparisons that do not involve &lt;operational&gt; regar
less of whether or not the parameter is set. dless of whether or not the parameter is set.
</t> </dd>
</list> </dl>
</t> <t>
<t>
The operation provides the following output parameter: The operation provides the following output parameter:
<list style="symbols"> </t>
<t>differences: This parameter contains the list of differences. Those di <dl spacing="normal">
fferences are encoded per the YANG-Patch data model defined in RFC8072. When a <dt>differences:</dt><dd> This parameter contains the list of difference
datastore node in the source of the comparison is not present in the target of t s. Those differences are encoded per the YANG Patch data model defined in <xref
he comparison, this can be indicated either as a "delete" or as a "remove" in th target="RFC8072"/>. When a datastore node in the source of the comparison is n
e patch as there is no differentiation between those operations for the purposes ot present in the target of the comparison, this can be indicated either as a "d
of the comparison. The YANG-Patch data model is augmented to indicate the value elete" or as a "remove" in the patch as there is no differentiation between thos
of source datastore nodes in addition to the patch itself that would need to be e operations for the purposes of the comparison.
applied to the source to produce the target. When the target datastore is &lt The YANG Patch data model is augmented to indicate the value of source datastore
;operational&gt; and the input parameter "report-origin" is set, "origin" metada nodes in addition to the patch itself that would need to be applied to the sour
ta is included as part of the patch. Including origin metadata can help in some ce to produce the target. When the target datastore is &lt;operational&gt; and
cases explain the cause of a difference, for example when a data node is part of the input parameter "report-origin" is set, origin metadata is included as part
&lt;intended&gt; but the origin of the same data node in &lt;operational&gt; is of the patch. Including origin metadata can help explain the cause of a differe
reported as "system".</t> nce in some cases -- for example, when a data node is part of &lt;intended&gt; b
</list> ut the origin of the same data node in &lt;operational&gt; is reported as "syste
</t> m".</dd>
</dl>
<t>The data model is defined in the ietf-nmda-compare YANG <t>The data model is defined in the ietf-nmda-compare YANG
module. Its structure is shown in the following figure. The notation syn tax module. Its structure is shown in the following figure. The notation syn tax
follows <xref target="RFC8340"/>.</t> follows <xref target="RFC8340" format="default"/>.</t>
<t> <figure>
<figure align="center" <name>Structure of ietf-nmda-compare</name>
title="Structure of ietf-nmda-compare">
<artwork align="left"> <sourcecode name="" type="yangtree" ><![CDATA[
module: ietf-nmda-compare module: ietf-nmda-compare
rpcs: rpcs:
+---x compare +---x compare
+---w input +---w input
| +---w source identityref | +---w source identityref
| +---w target identityref | +---w target identityref
| +---w all? empty | +---w all? empty
| +---w report-origin? empty | +---w report-origin? empty
| +---w (filter-spec)? | +---w (filter-spec)?
| +--:(subtree-filter) | +--:(subtree-filter)
| | +---w subtree-filter? | | +---w subtree-filter?
| +--:(xpath-filter) | +--:(xpath-filter)
| +---w xpath-filter? yang:xpath1.0 {nc:xpath}? | +---w xpath-filter? yang:xpath1.0 {nc:xpath}?
+--ro output +--ro output
+--ro (compare-response)? +--ro (compare-response)?
+--:(no-matches) +--:(no-matches)
| +--ro no-matches? empty | +--ro no-matches? empty
+--:(differences) +--:(differences)
+--ro differences +--ro differences
+--ro yang-patch +--ro yang-patch
+--ro patch-id string +--ro patch-id string
+--ro comment? string +--ro comment? string
+--ro edit* [edit-id] +--ro edit* [edit-id]
+--ro edit-id string +--ro edit-id string
+--ro operation enumeration +--ro operation enumeration
+--ro target target-resource-offset +--ro target target-resource-offset
+--ro point? target-resource-offset +--ro point? target-resource-offset
+--ro where? enumeration +--ro where? enumeration
+--ro value? +--ro value?
+--ro source-value? +--ro source-value?
</artwork> ]]></sourcecode>
</figure></t> </figure>
</section> </section>
<section numbered="true" toc="default">
<name>YANG Data Model</name>
<section title="YANG Data Model">
<t> <t>
<figure> This YANG module includes references to <xref target="RFC6991"/>, <xref target=
<artwork><![CDATA[ "RFC8342"/>, <xref target="RFC8072"/>,
<CODE BEGINS> file "ietf-nmda-compare@2021-08-06.yang" and <xref target="RFC6241"/>.
</t>
<sourcecode name="ietf-nmda-compare@2021-11-17.yang" type="yang" markers="
true"><![CDATA[
module ietf-nmda-compare { module ietf-nmda-compare {
yang-version 1.1; yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-nmda-compare"; namespace "urn:ietf:params:xml:ns:yang:ietf-nmda-compare";
prefix cmp; prefix cmp;
import ietf-yang-types { import ietf-yang-types {
prefix yang; prefix yang;
reference "RFC 6991: Common YANG Data Types"; reference
"RFC 6991: Common YANG Data Types";
} }
import ietf-datastores { import ietf-datastores {
prefix ds; prefix ds;
reference "RFC 8342: Network Management Datastore reference
Architecture (NMDA)"; "RFC 8342: Network Management Datastore
Architecture (NMDA)";
} }
import ietf-yang-patch { import ietf-yang-patch {
prefix ypatch; prefix ypatch;
reference "RFC 8072: YANG Patch Media Type"; reference
"RFC 8072: YANG Patch Media Type";
} }
import ietf-netconf { import ietf-netconf {
prefix nc; prefix nc;
reference "RFC6241: Network Configuration Protocol (NETCONF)"; reference
"RFC 6241: Network Configuration Protocol (NETCONF)";
} }
organization "IETF"; organization
"IETF NETMOD (Network Modeling) Working Group";
contact contact
"WG Web: <https://datatracker.ietf.org/wg/netconf/> "WG Web: <https://datatracker.ietf.org/wg/netmod/>
WG List: <mailto:netconf@ietf.org> WG List: <mailto:netmod@ietf.org>
Author: Alexander Clemm Author: Alexander Clemm
<mailto:ludwig@clemm.org> <mailto:ludwig@clemm.org>
Author: Yingzhen Qu Author: Yingzhen Qu
<mailto:yqu@futurewei.com> <mailto:yqu@futurewei.com>
Author: Jeff Tantsura Author: Jeff Tantsura
<mailto:jefftant.ietf@gmail.com> <mailto:jefftant.ietf@gmail.com>
skipping to change at line 233 skipping to change at line 222
<mailto:ludwig@clemm.org> <mailto:ludwig@clemm.org>
Author: Yingzhen Qu Author: Yingzhen Qu
<mailto:yqu@futurewei.com> <mailto:yqu@futurewei.com>
Author: Jeff Tantsura Author: Jeff Tantsura
<mailto:jefftant.ietf@gmail.com> <mailto:jefftant.ietf@gmail.com>
Author: Andy Bierman Author: Andy Bierman
<mailto:andy@yumaworks.com>"; <mailto:andy@yumaworks.com>";
description description
"The YANG data model defines a new operation, <compare>, that "The YANG data model defines a new operation, <compare>, that
can be used to compare NMDA datastores. can be used to compare NMDA datastores.
Copyright (c) 2021 IETF Trust and the persons identified as Copyright (c) 2021 IETF Trust and the persons identified as
authors of the code. All rights reserved. authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with or Redistribution and use in source and binary forms, with or
without modification, is permitted pursuant to, and subject to without modification, is permitted pursuant to, and subject to
the license terms contained in, the Simplified BSD License set the license terms contained in, the Revised BSD License set
forth in Section 4.c of the IETF Trust's Legal Provisions forth in Section 4.c of the IETF Trust's Legal Provisions
Relating to IETF Documents Relating to IETF Documents
(https://trustee.ietf.org/license-info). (https://trustee.ietf.org/license-info).
This version of this YANG module is part of This version of this YANG module is part of RFC 9144; see the
draft-ietf-netmod-nmda-diff-12; see the RFC itself for full RFC itself for full legal notices.";
legal notices.
NOTE TO RFC EDITOR: Please replace above reference to
draft-ietf-netmod-nmda-diff-12 with RFC number when published
(i.e. RFC xxxx).";
revision 2021-08-06 { revision 2021-11-17 {
description description
"Initial revision. "Initial revision.";
NOTE TO RFC EDITOR:
(1)Please replace the above revision date to
the date of RFC publication when published.
(2) Please replace the date in the file name
(ietf-nmda-compare@2021-08-06.yang) to the date of RFC
publication.
(3) Please replace the following reference to
draft-ietf-netmod-nmda-diff-12 with RFC number when published
(i.e. RFC xxxx).";
reference reference
"draft-ietf-netmod-nmda-diff-12: Comparison of NMDA "RFC 9144: Comparison of Network Management Datastore
datastores"; Architecture (NMDA) Datastores";
} }
/* RPC */ /* RPC */
rpc compare { rpc compare {
description description
"NMDA datastore compare operation."; "NMDA datastore compare operation.";
input { input {
leaf source { leaf source {
type identityref { type identityref {
base ds:datastore; base ds:datastore;
} }
mandatory true; mandatory true;
description description
skipping to change at line 299 skipping to change at line 274
} }
mandatory true; mandatory true;
description description
"The target datastore to be compared."; "The target datastore to be compared.";
} }
leaf all { leaf all {
type empty; type empty;
description description
"When this leaf is provided, all data nodes are compared, "When this leaf is provided, all data nodes are compared,
whether their schema node pertains to both datastores or whether their schema node pertains to both datastores or
not. When this leaf is omitted, a prefiltering step is not. When this leaf is omitted, a prefiltering step is
automatically applied that excludes data nodes from the automatically applied that excludes data nodes from the
comparison that can occur in only one datastore but not comparison that can occur in only one datastore but not
the other. Specifically, if one of the datastores the other. Specifically, if one of the datastores
(source or target) contains only configuration data and (source or target) contains only configuration data and
the other datastore is <operational>, data nodes for the other datastore is <operational>, data nodes for
which config is false are excluded from the comparison."; the config that is false are excluded from the
comparison.";
} }
leaf report-origin { leaf report-origin {
type empty; type empty;
description description
"When this leaf is provided, origin metadata is "When this leaf is provided, origin metadata is
included as part of RPC output. When this leaf is included as part of RPC output. When this leaf is
omitted, origin metadata in comparisons that involve omitted, origin metadata in comparisons that involve
<operational> is by default omitted."; <operational> is by default omitted.";
} }
choice filter-spec { choice filter-spec {
description description
"Identifies the portions of the datastores to be "Identifies the portions of the datastores to be
compared."; compared.";
anydata subtree-filter { anydata subtree-filter {
description description
"This parameter identifies the portions of the "This parameter identifies the portions of the
target datastore to retrieve."; target datastore to retrieve.";
reference "RFC 6241, Section 6."; reference
"RFC 6241, Section 6.";
} }
leaf xpath-filter { leaf xpath-filter {
if-feature nc:xpath; if-feature "nc:xpath";
type yang:xpath1.0; type yang:xpath1.0;
description description
"This parameter contains an XPath expression "This parameter contains an XPath expression
identifying the portions of the target identifying the portions of the target
datastore to retrieve."; datastore to retrieve.";
reference "RFC 6991: Common YANG Data Types"; reference
"RFC 6991: Common YANG Data Types";
} }
} }
} }
output { output {
choice compare-response { choice compare-response {
description description
"Comparison results."; "Comparison results.";
leaf no-matches { leaf no-matches {
type empty; type empty;
description description
"This leaf indicates that the filter did not match "This leaf indicates that the filter did not match
anything and nothing was compared."; anything and nothing was compared.";
} }
container differences { container differences {
description description
"The list of differences, encoded per RFC8072 with an "The list of differences, encoded per RFC 8072 with an
augmentation to include source values where applicable. augmentation to include source values where applicable.
When a datastore node in the source is not present in When a datastore node in the source is not present in
the target, this can be indicated either as a 'delete' the target, this can be indicated either as a 'delete'
or as a 'remove' as there is no difference between or as a 'remove' as there is no difference between
them for the purposes of the comparison."; them for the purposes of the comparison.";
uses ypatch:yang-patch { uses ypatch:yang-patch {
augment "yang-patch/edit" { augment "yang-patch/edit" {
description description
"Provide the value of the source of the patch, "Provides the value of the source of the patch,
respectively of the comparison, in addition to respectively of the source of the comparison, in
the target value, where applicable."; addition to the target value, where applicable.";
anydata source-value { anydata source-value {
when "../operation = 'delete'" when "../operation = 'delete'"
+ "or ../operation = 'merge'" + "or ../operation = 'merge'"
+ "or ../operation = 'move'" + "or ../operation = 'move'"
+ "or ../operation = 'replace'" + "or ../operation = 'replace'"
+ "or ../operation = 'remove'"; + "or ../operation = 'remove'";
description description
"The anydata 'value' is only used for 'delete', "The anydata 'value' is only used for 'delete',
'move', 'merge', 'replace', and 'remove' 'move', 'merge', 'replace', and 'remove'
operations."; operations.";
} }
reference "RFC 8072: YANG Patch Media Type"; reference
"RFC 8072: YANG Patch Media Type";
} }
} }
} }
} }
} }
} }
} }
<CODE ENDS>
]]></artwork></figure>
</t>
</section> ]]></sourcecode>
</section>
<section title="Example"> <section numbered="true" toc="default">
<t> <name>Example</name>
The following example compares the difference between &lt;operational&gt; and &l <t>
t;intended&gt; for a subtree under "interfaces". The subtree contains a subset o The following example compares the difference between &lt;operational&gt; and &l
f objects that are defined in a YANG data model for the management of interfaces t;intended&gt; for a subtree under "interfaces". The subtree contains a subset o
defined in <xref target="RFC8343"/>. For the purposes of understanding the sub f objects that are defined in a YANG data model for the management of interfaces
sequent example, the following excerpt of the data model whose instantiation is defined in <xref target="RFC8343" format="default"/>. For the purposes of unde
the basis of the comparison is provided: rstanding the subsequent example, the following excerpt of the data model whose
<figure> instantiation is the basis of the comparison is provided:
<artwork align="left"><![CDATA[ </t>
<sourcecode name="" type="yang"><![CDATA[
container interfaces { container interfaces {
description description
"Interface parameters."; "Interface parameters.";
list interface { list interface {
key "name"; key "name";
leaf name { leaf name {
type string; type string;
description description
"The name of the interface". "The name of the interface.";
} }
leaf description { leaf description {
type string; type string;
description description
"A textual description of the interface."; "A textual description of the interface.";
} }
leaf enabled { leaf enabled {
type boolean; type boolean;
default "true"; default "true";
description description
"This leaf contains the configured, desired state of the "This leaf contains the configured, desired state of the
interface.";" interface.";
} }
} }
} }
]]></artwork> ]]></sourcecode>
</figure>
</t>
<t>
The contents of &lt;intended&gt; and &lt;operational&gt; datastores:
<figure>
<artwork align="left"><![CDATA[
//INTENDED <t>
The contents of &lt;intended&gt; and &lt;operational&gt; datastores in XML <xref
target="W3C.REC-xml-20081126"/>:
</t>
<sourcecode name="" type="xml"><![CDATA[
<!--INTENDED-->
<interfaces xmlns="urn:ietf:params:xml:ns:yang:ietf-interfaces"> <interfaces xmlns="urn:ietf:params:xml:ns:yang:ietf-interfaces">
<interface> <interface>
<name>eth0</name> <name>eth0</name>
<enabled>false</enabled> <enabled>false</enabled>
<description>ip interface</description> <description>ip interface</description>
</interface> </interface>
</interfaces> </interfaces>
]]></sourcecode>
//OPERATIONAL <sourcecode name="" type="xml"><![CDATA[
<!--OPERATIONAL-->
<interfaces <interfaces
xmlns="urn:ietf:params:xml:ns:yang:ietf-interfaces" xmlns="urn:ietf:params:xml:ns:yang:ietf-interfaces"
xmlns:or="urn:ietf:params:xml:ns:yang:ietf-origin"> xmlns:or="urn:ietf:params:xml:ns:yang:ietf-origin">
<interface or:origin="or:learned"> <interface or:origin="or:learned">
<name>eth0</name> <name>eth0</name>
<enabled>true</enabled> <enabled>true</enabled>
</interface> </interface>
</interfaces> </interfaces>
]]></artwork> ]]></sourcecode>
</figure> <t>
</t>
<t>
&lt;operational&gt; does not contain an instance for leaf "description" that is contained in &lt;intended&gt;. Another leaf, "enabled", has different values in the two datastores, being "true" in &lt;operational&gt; and "false" in &lt;inte nded&gt;. A third leaf, "name", is the same in both cases. The origin of the l eaf instances in &lt;operational&gt; is "learned", which may help explain the di screpancies. &lt;operational&gt; does not contain an instance for leaf "description" that is contained in &lt;intended&gt;. Another leaf, "enabled", has different values in the two datastores, being "true" in &lt;operational&gt; and "false" in &lt;inte nded&gt;. A third leaf, "name", is the same in both cases. The origin of the l eaf instances in &lt;operational&gt; is "learned", which may help explain the di screpancies.
</t> </t>
<t> <t>
RPC request to compare &lt;operational&gt; (source of the comparison) with &l RPC request to compare &lt;operational&gt; (source of the comparison) with &lt;i
t;intended&gt;(target of the comparison): ntended&gt; (target of the comparison):
<figure> </t>
<artwork align="left"><![CDATA[ <sourcecode name="" type="xml"><![CDATA[
<rpc message-id="101" <rpc message-id="101"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0"> xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<compare xmlns="urn:ietf:params:xml:ns:yang:ietf-nmda-compare" <compare xmlns="urn:ietf:params:xml:ns:yang:ietf-nmda-compare"
xmlns:ds="urn:ietf:params:xml:ns:yang:ietf-datastores"> xmlns:ds="urn:ietf:params:xml:ns:yang:ietf-datastores">
<source>ds:operational</source> <source>ds:operational</source>
<target>ds:intended</target> <target>ds:intended</target>
<report-origin/> <report-origin/>
<xpath-filter <xpath-filter
xmlns:if="urn:ietf:params:xml:ns:yang:ietf-interfaces"> xmlns:if="urn:ietf:params:xml:ns:yang:ietf-interfaces">
/if:interfaces /if:interfaces
</xpath-filter> </xpath-filter>
</compare> </compare>
</rpc> </rpc>
]]></artwork> ]]></sourcecode>
</figure> <t>
RPC reply when a difference is detected:
</t> </t>
<t> <sourcecode name="" type="xml"><![CDATA[
RPC reply, when a difference is detected:
<figure>
<artwork align="left"><![CDATA[
<rpc-reply <rpc-reply
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0" xmlns="urn:ietf:params:xml:ns:netconf:base:1.0"
message-id="101"> message-id="101">
<differences <differences
xmlns="urn:ietf:params:xml:ns:yang:ietf-nmda-compare" xmlns="urn:ietf:params:xml:ns:yang:ietf-nmda-compare"
xmlns:or="urn:ietf:params:xml:ns:yang:ietf-origin"> xmlns:or="urn:ietf:params:xml:ns:yang:ietf-origin">
<yang-patch> <yang-patch>
<patch-id>interface status</patch-id> <patch-id>interface status</patch-id>
<comment> <comment>
diff between operational (source) and intended (target) diff between operational (source) and intended (target)
</comment> </comment>
<edit> <edit>
<edit-id>1</edit-id> <edit-id>1</edit-id>
<operation>replace</operation> <operation>replace</operation>
<target>/ietf-interfaces:interface=eth0/enabled</target> <target>/ietf-interfaces:interface=eth0/enabled</target>
<value> <value>
<if:enabled>false<if:enabled> <if:enabled>false</if:enabled>
</value> </value>
<source-value> <source-value>
<if:enabled or:origin="or:learned">true</if:enabled> <if:enabled or:origin="or:learned">true</if:enabled>
</source-value> </source-value>
</edit> </edit>
<edit> <edit>
<edit-id>2</edit-id> <edit-id>2</edit-id>
<operation>create</operation> <operation>create</operation>
<target>/ietf-interfaces:interface=eth0/description</target> <target>/ietf-interfaces:interface=eth0/description</target>
<value> <value>
<if:description>ip interface<description> <if:description>ip interface</if:description>
</value> </value>
</edit> </edit>
</yang-patch> </yang-patch>
</differences> </differences>
</rpc-reply> </rpc-reply>
]]></artwork> ]]></sourcecode>
</figure> <t>
The same request in RESTCONF (using JSON format <xref target="RFC7951"/>):
</t> </t>
<t> <sourcecode name="" type="json"><![CDATA[
The same request in RESTCONF (using JSON format):
<figure>
<artwork align="left"><![CDATA[
POST /restconf/operations/ietf-nmda-compare:compare HTTP/1.1 POST /restconf/operations/ietf-nmda-compare:compare HTTP/1.1
Host: example.com Host: example.com
Content-Type: application/yang-data+json Content-Type: application/yang-data+json
Accept: application/yang-data+json Accept: application/yang-data+json
{ "ietf-nmda-compare:input" : { { "ietf-nmda-compare:input" : {
"source" : "ietf-datastores:operational", "source" : "ietf-datastores:operational",
"target" : "ietf-datastores:intended", "target" : "ietf-datastores:intended",
"report-origin" : null, "report-origin" : null,
"xpath-filter" : "/ietf-interfaces:interfaces" "xpath-filter" : "/ietf-interfaces:interfaces"
} }
} }
]]></artwork> ]]></sourcecode>
</figure> <t>
</t>
<t>
The same response in RESTCONF (using JSON format): The same response in RESTCONF (using JSON format):
<figure> </t>
<artwork align="left"><![CDATA[ <sourcecode name="" type="json"><![CDATA[
HTTP/1.1 200 OK HTTP/1.1 200 OK
Date: Thu, 24 Jan 2019 20:56:30 GMT Date: Thu, 24 Jan 2019 20:56:30 GMT
Server: example-server Server: example-server
Content-Type: application/yang-data+json Content-Type: application/yang-data+json
{ "ietf-nmda-compare:output" : { { "ietf-nmda-compare:output" : {
"differences" : { "differences" : {
"ietf-yang-patch:yang-patch" : { "ietf-yang-patch:yang-patch" : {
"patch-id" : "interface status", "patch-id" : "interface status",
"comment" : "diff between intended (source) and operational", "comment" : "diff between intended (source) and operational",
skipping to change at line 560 skipping to change at line 527
"@ietf-interfaces:interface/enabled" : { "@ietf-interfaces:interface/enabled" : {
"ietf-origin:origin" : "ietf-origin:learned" "ietf-origin:origin" : "ietf-origin:learned"
} }
} }
}, },
{ {
"edit-id" : "2", "edit-id" : "2",
"operation" : "create", "operation" : "create",
"target" : "/ietf-interfaces:interface=eth0/description", "target" : "/ietf-interfaces:interface=eth0/description",
"value" : { "value" : {
"ietf-interface:interface/description" : "ip interface" "ietf-interface:interface/description" : "ip interface"
} }
} }
] ]
} }
} }
} }
} }
]]></artwork> ]]></sourcecode>
</figure> </section>
</t> <section numbered="true" toc="default">
</section> <name>Performance Considerations</name>
<t>
<section title="Performance Considerations"> The &lt;compare&gt; operation can be computationally expensive. While responsib
<t> le client applications are expected to use the operation responsibly and sparing
The compare operation can be computationally expensive. While responsible clien ly only when warranted, implementations need to be aware of the fact that excess
t applications are expected to use the operation responsibly and sparingly only ive invocation of this operation will burden system resources and need to ensure
when warranted, implementations need to be aware of the fact that excessive invo that system performance will not be adversely impacted. One possibility for an
cation of this operation will burden system resources and need to ensure that sy implementation to mitigate against this is to limit the number of requests that
stem performance will not be adversely impacted. One possibility for an impleme are served to a client, or to any number of clients, in any one time interval,
ntation to mitigate against this is to limit the number of requests that are ser by rejecting requests made at a higher frequency than the implementation can rea
ved to a client, or to any number of clients, in any one time interval, by rejec sonably sustain.</t>
ting requests made at a higher frequency than the implementation can reasonably <t>
sustain.</t> While useful, tools such as YANG data models that allow for the monitorin
<t> g of server resources, system performance,
While useful, tools such as YANG Data Models that allow for the monitorin
g of server resources, system performance,
and statistics about RPCs and RPC rates are outside the scope of this document. and statistics about RPCs and RPC rates are outside the scope of this document.
When defined, any such model should be general in nature and not limited to the RPC operation defined in this document. When defined, any such model should be general in nature and not limited to the RPC operation defined in this document.
</t> </t>
</section>
</section> <section numbered="true" toc="default">
<name>IANA Considerations</name>
<section title="IANA Considerations"> <section numbered="true" toc="default">
<section title="Updates to the IETF XML Registry"> <name>Update to the IETF XML Registry</name>
<t>This document registers one URI in the IETF XML registry <xref target="RFC368 <t>IANA has registered the following URI in the "IETF XML Registry" <xre
8"/>. Following the format in <xref target="RFC3688"/>, the following registrat f target="RFC3688" format="default"/>:
ion is requested:
<list>
<t>URI: urn:ietf:params:xml:ns:yang:ietf-nmda-compare</t>
<t>Registrant Contact: The IESG.</t>
<t>XML: N/A, the requested URI is an XML namespace.</t>
</list>
</t> </t>
</section> <dl spacing="compact">
<section title="Updates to the YANG Module Names Registry"> <dt>URI:</dt><dd>urn:ietf:params:xml:ns:yang:ietf-nmda-compare</dd>
<t> <dt>Registrant Contact:</dt><dd>The IESG.</dd>
This document registers a YANG module in the YANG Module Names <dt>XML:</dt><dd>N/A; the requested URI is an XML namespace.</dd>
registry <xref target="RFC6020"/>. Following the format in <xref target="RFC </dl>
6020"/>, the </section>
following registration is requested: <section numbered="true" toc="default">
<list> <name>Update to the YANG Module Names Registry</name>
<t>name: ietf-nmda-compare</t> <t>
<t>namespace: urn:ietf:params:xml:ns:yang:ietf-nmda-compare</t> IANA has registered the following YANG module in the "YANG Module Names"
<t>prefix: cmp</t> registry <xref target="RFC6020" format="default"/>:
<t>reference: draft-ietf-netmod-nmda-diff-12 (RFC form)</t>
</list>
</t> </t>
</section> <dl spacing="compact">
<dt>name:</dt><dd>ietf-nmda-compare</dd>
</section> <dt>namespace:</dt><dd>urn:ietf:params:xml:ns:yang:ietf-nmda-compare</
dd>
<section title="Security Considerations"> <dt>prefix:</dt><dd>cmp</dd>
<dt>reference:</dt><dd>RFC 9144</dd>
<t> </dl>
</section>
</section>
<section numbered="true" toc="default">
<name>Security Considerations</name>
<t>
The YANG module specified in this document defines a schema for data The YANG module specified in this document defines a schema for data
that is designed to be accessed via network management protocols such that is designed to be accessed via network management protocols such
as NETCONF <xref target="RFC6241"/> or RESTCONF <xref target="RFC8040"/>. Th e lowest NETCONF layer as NETCONF <xref target="RFC6241" format="default"/> or RESTCONF <xref target ="RFC8040" format="default"/>. The lowest NETCONF layer
is the secure transport layer, and the mandatory-to-implement secure is the secure transport layer, and the mandatory-to-implement secure
transport is Secure Shell (SSH) <xref target="RFC6242"/>. The lowest RESTCON transport is Secure Shell (SSH) <xref target="RFC6242" format="default"/>. T
F layer he lowest RESTCONF layer
is HTTPS, and the mandatory-to-implement secure transport is TLS <xref target is HTTPS, and the mandatory-to-implement secure transport is TLS <xref target
="RFC8446"/>. ="RFC8446" format="default"/>.
</t> </t>
<t> <t>
The NETCONF access control model <xref target="RFC8341"/> provides the means The Network Configuration Access Control Model (NACM) <xref target="RFC8341"
to format="default"/> provides the means to
restrict access for particular NETCONF or RESTCONF users to a restrict access for particular NETCONF or RESTCONF users to a
preconfigured subset of all available NETCONF or RESTCONF protocol preconfigured subset of all available NETCONF or RESTCONF protocol
operations and content. operations and content.
</t> </t>
<t>NACM specifies access for the server in its entirety and the same access rule <t>NACM specifies access for the server in its entirety, and the same acce
s apply to all datastores. ss rules apply to all datastores.
Any subtrees to which a requestor does not have read access are silently Any subtrees to which a requestor does not have read access are silently
skipped and not included in the comparison.</t> skipped and not included in the comparison.</t>
<t> <t>
The RPC operation defined in this YANG module, "compare", may be considered The RPC operation defined in this YANG module, &lt;compare&gt;, may be consid ered
sensitive or vulnerable in some network environments. It is thus sensitive or vulnerable in some network environments. It is thus
important to control access to this operation. This is the sensitivity/vulne important to control access to this operation. This is the sensitivity/vulne
rability of RPC operation "compare": rability of RPC operation &lt;compare&gt;:
</t> </t>
<t> <t>
Comparing datastores for differences requires a certain amount of processing r Comparing datastores for differences requires a certain amount of processing r
esources at the server. An attacker could attempt to attack a server by making esources at the server. An attacker could attempt to attack a server by making
a high volume of comparison requests. Server implementations can guard against s a high volume of comparison requests. Server implementations can guard against s
uch scenarios in several ways. For one, they can implement the NETCONF access c uch scenarios in several ways. For one, they can implement the NACM in order to
ontrol model in order to require proper authorization for requests to be made. require proper authorization for requests to be made. Second, server implement
Second, server implementations can limit the number of requests that they serve ations can limit the number of requests that they serve to a client in any one t
to a client in any one time interval, rejecting requests made at a higher freque ime interval, rejecting requests made at a higher frequency than the implementat
ncy than the implementation can reasonably sustain. ion can reasonably sustain.
</t>
</section>
<section title="Acknowledgments">
<t>We thank Rob Wilton, Martin Bjorklund, Mahesh Jethanandani, Lou Berger, Kent
Watsen, Phil Shafer, Ladislav Lhotka, Tim Carey, and Reshad Rahman for valuable
feedback and suggestions.
</t> </t>
</section> </section>
</middle>
</middle> <back>
<references>
<back> <name>References</name>
<references>
<references title="Normative References"> <name>Normative References</name>
<?rfc include="reference.RFC.2119"?> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R
<?rfc include="reference.RFC.3688"?> FC.2119.xml"/>
<?rfc include="reference.RFC.6020"?> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R
<?rfc include="reference.RFC.6241"?> FC.3688.xml"/>
<?rfc include="reference.RFC.6242"?> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R
<?rfc include="reference.RFC.6991"?> FC.6020.xml"/>
<?rfc include="reference.RFC.7950"?> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R
<?rfc include="reference.RFC.8040"?> FC.6241.xml"/>
<?rfc include="reference.RFC.8072"?> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R
<?rfc include="reference.RFC.8174"?> FC.6242.xml"/>
<?rfc include="reference.RFC.8340"?> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R
<?rfc include="reference.RFC.8341"?> FC.6991.xml"/>
<?rfc include="reference.RFC.8342"?> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R
<?rfc include="reference.RFC.8446"?> FC.7950.xml"/>
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R
</references> FC.7951.xml"/>
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R
FC.8040.xml"/>
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R
FC.8072.xml"/>
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R
FC.8174.xml"/>
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R
FC.8340.xml"/>
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R
FC.8341.xml"/>
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R
FC.8342.xml"/>
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R
FC.8446.xml"/>
<references title="Informative References"> <reference anchor="W3C.REC-xml-20081126" target="https://www.w3.org/TR/2008/REC
<?rfc include="reference.RFC.8343"?> -xml-20081126" quoteTitle="true" derivedAnchor="W3C.REC-xml-20081126">
</references> <front>
<title>Extensible Markup Language (XML) 1.0 (Fifth Edition)</title>
<author initials="T." surname="Bray" fullname="Tim Bray">
<organization showOnFrontPage="true"/>
</author>
<author initials="J." surname="Paoli" fullname="Jean Paoli">
<organization showOnFrontPage="true"/>
</author>
<author initials="M." surname="Sperberg-McQueen" fullname="Michael S
perberg-McQueen">
<organization showOnFrontPage="true"/>
</author>
<author initials="E." surname="Maler" fullname="Eve Maler">
<organization showOnFrontPage="true"/>
</author>
<author initials="F." surname="Yergeau" fullname="Francois Yergeau">
<organization showOnFrontPage="true"/>
</author>
<date month="November" year="2008"/>
</front>
<refcontent>World Wide Web Consortium Recommendation REC-xml-20081126<
/refcontent>
</reference>
<section title="Possible Future Extensions"> </references>
<references>
<name>Informative References</name>
<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R
FC.8343.xml"/>
</references>
</references>
<section numbered="true" toc="default">
<name>Possible Future Extensions</name>
<t>It is conceivable to extend the &lt;compare&gt; operation with a number
of possible additional features in the future. </t>
<t>It is conceivable to extend the compare operation with a number of possib <t>
le additional features in the future. </t> Specifically, it is possible to define an extension with an optional feature
<t> for dampening. This will allow clients to specify a minimum time period for whi
Specifically, it is possible to define an extension with an optional feature ch a difference must persist for it to be reported. This will enable clients to
for dampening. This will allow clients to specify a minimum time period for w distinguish between differences that are only fleeting from ones that are not a
hich a difference must persist for it to be reported. This will enable clients nd that may represent a real operational issue and inconsistency within the devi
to distinguish between differences that are only fleeting from ones that are not ce.
and that may represent a real operational issue and inconsistency within the de </t>
vice. <t>For this purpose, an additional input parameter can be added to specify
</t> the dampening period. Only differences that pertain
<t>For this purpose, an additional input parameter can be added to specify t
he dampening period. Only differences that pertain
for at least the dampening time are reported. for at least the dampening time are reported.
A value of 0 or omission of the parameter indicates no A value of 0 or omission of the parameter indicates no
dampening. dampening.
Reporting of differences MAY correspondingly be delayed by the dampen Reporting of differences <bcp14>MAY</bcp14> correspondingly be delaye
ing period from the time the request is received. d by the dampening period from the time the request is received.
</t> </t>
<t> <t>
To implement this feature, a server implementation might run a comparison wh en the RPC is first invoked and temporarily store the result. Subsequently, it could wait until after the end of the dampening period to check whether the same differences are still observed. The differences that still persist are then re turned. To implement this feature, a server implementation might run a comparison wh en the RPC is first invoked and temporarily store the result. Subsequently, it could wait until after the end of the dampening period to check whether the same differences are still observed. The differences that still persist are then re turned.
</t> </t>
</section>
</section> <section numbered="false" toc="default">
</back> <name>Acknowledgments</name>
<t>We thank <contact fullname="Rob Wilton"/>, <contact fullname="Martin Bj
orklund"/>, <contact fullname="Mahesh Jethanandani"/>, <contact fullname="Lou Be
rger"/>, <contact fullname="Kent Watsen"/>, <contact fullname="Phil Shafer"/>, <
contact fullname="Ladislav Lhotka"/>, <contact fullname="Tim Carey"/>, and <cont
act fullname="Reshad Rahman"/> for their valuable feedback and suggestions.
</t>
</section>
</rfc> </back> </rfc>
 End of changes. 83 change blocks. 
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