One document matched: draft-ietf-netconf-server-model-02.xml
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<rfc category="std"
ipr="trust200902"
docName="draft-ietf-netconf-server-model-02" >
<front>
<title abbrev="NETCONF Server Configuration Model">NETCONF Server Configuration Model</title>
<author initials="K.W." surname="Watsen" fullname="Kent Watsen">
<organization>Juniper Networks</organization>
<address>
<email>kwatsen@juniper.net</email>
</address>
</author>
<author initials="J.S." surname="Schoenwaelder" fullname="Juergen Schoenwaelder">
<organization>Jacobs University Bremen</organization>
<address>
<email>j.schoenwaelder@jacobs-university.de</email>
</address>
</author>
<date month="September" year="2014"/>
<area>Operations</area>
<workgroup>NETCONF Working Group</workgroup>
<keyword>netconf-server</keyword>
<abstract>
<t>This draft defines a NETCONF server configuration data model.
This data model enables configuration of the NETCONF service
itself, including which transports it supports, what ports
they listen on, whether they support device-initiated
connections, and associated parameters.</t>
</abstract>
</front>
<middle>
<section title="Introduction">
<t>This draft defines a NETCONF <xref target="RFC6241"/> server
configuration data model.
This data model enables configuration of the NETCONF service
itself, including which transports are supported, what ports
does the server listen on, whether call-home is supported, and
associated parameters.</t>
<section title="Terminology">
<t>The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL",
"SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
and "OPTIONAL" in this document are to be interpreted as
described in RFC 2119 <xref target="RFC2119"/>.</t>
</section>
<section title="Tree Diagrams">
<t>A simplified graphical representation of data models
is used in this document. The meaning of the symbols in
these diagrams is as follows:
<list style="symbols">
<t>Brackets "[" and "]" enclose list keys.</t>
<t>Abbreviations before data node names: "rw" means
configuration (read-write) and "ro" state data
(read-only).</t>
<t>Symbols after data node names: "?" means an optional
node, "!" means a presence container, and "*" denotes a
list and leaf-list.</t>
<t>Parentheses enclose choice and case nodes, and case
nodes are also marked with a colon (":").</t>
</list>
</t>
</section>
</section>
<section title="Objectives">
<t>The primary purpose of the YANG module defined herein is
to enable the configuration of the NETCONF service on the
device. This scope includes the following objectives:</t>
<section title="Support all NETCONF Transports">
<t>The YANG module should support all current NETCONF
transports, namely NETCONF over SSH <xref
target="RFC6242"/> and NETCONF over TLS <xref
target="I-D.ietf-netconf-rfc5539bis"/>, and be extensible
to support future transports as necessary.</t>
<t>Since implementations may not support all transports,
the module should use YANG "feature" statements
so that implementations can accurately advertise which
transports are supported.</t>
</section>
<section title="Align Transport-Specific Configurations">
<t>While each transport is unique in its protocol and
may have some distinct configurations, there remains
a significant overlap between them. Thus the YANG module
should use "grouping" statements so that the
common aspects can be configured similarly.</t>
</section>
<section title="Support both Listening for Connections and Call Home">
<t>NETCONF has always supported the server opening
a port to listen for client connections. More recently
the NETCONF working group defined support for call-home
(<xref target="I-D.ietf-netconf-rfc5539bis"/> and
<xref target="draft-ieft-netconf-reverse-ssh"/>). The
module should configure both listening for connections
and call-home.</t>
<t>Since implementations may not support both listening for
connections and call home, YANG "feature" statements
should be used so that implementation can accurately
advertise the connection types it supports.</t>
</section>
<section title="For Call Home Connections">
<t>The following objectives only pertain to call home
connections.</t>
<section title="Support More than One Application">
<t>A device may be managed by more than one northbound
application. For instance, a deployment may have one
application for provisioning and another for fault
monitoring. Therefore, when it is desired for a device
to initiate call home connections, it should be able to
do so for more than one application.</t>
</section>
<section title="Support Applications Having More than One Server">
<t>An application managing a device may implement a
high-availability strategy employing a multiplicity of
active and/or passive servers. Therefore, when it is
desired for a device to initiate call home connections,
it should be able to connect to any of the applications
servers.</t>
</section>
<section title="Support a Reconnection Strategy">
<t>Assuming an application has more than one server, then
it becomes necessary to configure how a device should
reconnect to the application should it lose its
connection to the application's servers.
Of primary interest is if the device should
start with first server defined in a user-ordered
list of servers or with the last server it was connected
to. Secondary settings might specify the frequency of
attempts and number of attempts per server. Therefore,
a reconnection strategy should be configurable.</t>
</section>
<section title="Support both Persistent and Periodic Connections">
<t>Applications may vary greatly on how frequently they
need to interact with a device, how responsive interactions
with devices need to be, and how many simultaneous connections
they can support. Some applications may need a persistent
connection to devices to optimize real-time interactions,
while others are satisfied with periodic interactions and
reduced resources required. Therefore, when it is necessary
for devices to initiate connections, the type of connection
desired should be configured.</t>
</section>
<section title="Reconnection Strategy for Periodic Connections">
<t>The reconnection strategy should apply to both
persistent and periodic connections. How it
applies to periodic connections becomes clear when
considering that a periodic "connection" is
a logical connection to a single server. That is,
the periods of unconnectedness are intentional as
opposed to due to external reasons. A periodic
"connection" should always reconnect to
the same server until it is no longer able to, at
which time the reconnection strategy guides how to
connect to another server.</t>
</section>
<section anchor="keepalives" title="Keep-Alives for Persistent Connections">
<t>If a persistent connection is desired, it is the
responsibility of the connection-initiator to actively
test the aliveness of the connection. The connection
initiator must immediately work to reestablish a
persistent connection as soon as the connection is
lost. How often the connection should be tested is
driven by applications requirements, and therefore
keep-alive settings should be configurable on a
per-application basis.</t>
</section>
<section title="Customizations for Periodic Connections">
<t>If a periodic connection is desired, it is necessary
for the device to know how often it should connect. This
delay essentially determines how long the
application might have to wait to send data to the device.
This setting does not constrain how often the
device must wait to send data to the application, as the
device should immediately connect to the application
whenever it has data to send to it.</t>
<t>A common communication pattern is that one data
transmission is many times closely followed by
another. For instance, if the device needs to send a
notification message, there's a high probability that
it will send another shortly thereafter. Likewise,
the application may have a sequence of pending messages
to send. Thus, it should be possible for a device to
hold a connection open until some amount of time of no
data being transmitted as transpired.</t>
</section>
</section>
</section>
<section title="Data Model">
<section title="Overview">
<t>To enable transports to configure listening on one
or more ports in a common way, the following subtree is defined.
This subtree defines SSH and TLS specific containers, each
of which refines the default listening port appropriately.
Further, each of these transport specific containers use a
feature statement, enabling NETCONF servers to accurately
advertise what they support.</t>
<t>
<figure>
<artwork><![CDATA[
INSERT_TEXT_FROM_FILE(refs/listen-tree.txt)
]]></artwork>
</figure>
</t>
<t>To enable transports to configure initiating connections
to remote applications in a common way, the following subtree is
defined. This subtree configures a list of appliacations,
each with some transport-specific configuration augmented in.
Each of the transport specific containers use a feature
statement, enabling NETCONF servers to accurately advertise
what they support.</t>
<t>
<figure>
<artwork><![CDATA[
INSERT_TEXT_FROM_FILE(refs/call-home-tree.txt)
]]></artwork>
</figure>
</t>
<t>The following subtree illustrates how this YANG module
enables authentication of TLS client certificates and
mapping TLS clients to NETCONF user names. More
specifically, the "trusted-ca-certs" and
"trusted-client-certs" containers are used to authenticate
TLS client certificates, while "cert-maps" and "psk-maps"
are used to map TLS clients to NETCONF user names.
</t>
<t>
<figure>
<artwork><![CDATA[
INSERT_TEXT_FROM_FILE(refs/tls-client-auth-tree.txt)
]]></artwork>
</figure>
</t>
</section>
<section title="YANG Module">
<t>This YANG module imports YANG types from <xref
target="RFC6991"/>, <xref target="RFC6536"/>, and
<xref target="draft-ietf-netmod-snmp-cfg"/>.</t>
<t>
<figure>
<!--<preamble>The YANG Module</preamble>-->
<artwork><![CDATA[
RFC Ed.: update the date below with the date of RFC publication
and remove this note.
<CODE BEGINS> file "ietf-netconf-server@YYYY-MM-DD.yang"
INSERT_TEXT_FROM_FILE(ietf-netconf-server.yang)
<CODE ENDS>
]]></artwork>
</figure>
</t>
</section>
</section>
<section title="Keep-Alives for SSH and TLS">
<t>One the objectives listed above, <xref target="keepalives">
Keep-Alives for Persistent Connections</xref> indicates a need
for a "keep-alive" mechanism. This section specifies how the
NETCONF keep-alive mechanism is to be implemented.</t>
<t>Both SSH and TLS have the ability to support keep-alives.
Using these mechanisms, the keep-alive messages are sent inside
the encrypted tunnel, thus thwarting spoof attacks.</t>
<section title="SSH">
<t>The SSH keep-alive solution that is expected to be used
when configured using the data model defined in this document
is ubiquitous in practice, though never being explicitly defined
in an RFC. The strategy used is to purposely send a malformed
request message with a flag set to ensure a response. More
specifically, per section 4 of <xref target="RFC4253"/>, either
SSH peer can send a SSH_MSG_GLOBAL_REQUEST message with "want
reply" set to '1' and that, if there is an error, will get back
a SSH_MSG_REQUEST_FAILURE response. Similarly, section 5 of
<xref target="RFC4253"/> says that either SSH peer can send a
SSH_MSG_CHANNEL_REQUEST message with "want reply" set to '1'
and that, if there is an error, will get back a
SSH_MSG_CHANNEL_FAILURE response.</t>
<t>To ensure that the request will fail, current implementations
send an invalid "request name" or "request type", respectively.
Abiding to the extensibility guidelines specified in Section 6
of <xref target="RFC4251"/>, these implementations use the
"name@domain". For instance, when configured to send keep-alives,
OpenSSH sends the string "keepalive@openssh.com". In order to
remain compatible with existing implementations, this draft does
not require a specific "request name" or "request type" string
be used.</t>
</section>
<section title="TLS">
<t>The TLS keep-alive solution is defined in <xref target="RFC6520"/>.
This solution allows both peers to advertise if they can
receive heartbeat request messages from its peer.
For standard NETCONF over TLS connections, devices SHOULD
advertise "peer_allowed_to_send", as per <xref target="RFC6520"/>.
This advertisement is not a "MUST" in order to grandfather
existing NETCONF over TLS implementations.
For NETCONF over TLS Call Home, the network management
system MUST advertise "peer_allowed_to_send" per
<xref target="RFC6520"/>. This is a "MUST" so as to ensure
devices can depend in it always being there for call home
connections, which is conveniently when keep-alives are
needed the most.</t>
</section>
</section>
<section title="Security Considerations">
<t>The YANG modules defined in this memo are designed to be
accessed via the NETCONF protocol <xref target="RFC6241"/>.
Authorization for access to specific portions of conceptual
data and operations within this module is provided by the
NETCONF access control model (NACM) <xref target="RFC6536"/>.</t>
<t>There are a number of data nodes defined in the
"ietf-netconf-server" and "ietf-system-tls-auth" YANG
modules which 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 and read operations to
these data nodes can have a negative effect on network
operations. It is thus important to control write
and read access to these data nodes. Below are the
data nodes and their sensitivity/vulnerability.</t>
<t>ietf-netconf-server:
<list style="symbols">
<t>None.</t>
</list>
</t>
<t>ietf-system-tls-auth:
<list style="symbols">
<t>/system/authentication/tls/psk-maps/psk-map/user-name:
This leaf node contains a user name that some deployments
may consider sensitive information.</t>
<t>/system/authentication/tls/psk-maps/psk-map/key: This
leaf node contains a shared key that remote clients use
to authenticate themselves to the system. This value
should not be readable or writable by anyone by default.</t>
</list>
</t>
</section>
<section title="IANA Considerations">
<t>This document registers two URIs in the IETF XML
registry <xref target="RFC2119"/>. Following the format in
<xref target="RFC3688"/>, the following registrations are
requested:</t>
<t>
<figure>
<artwork><![CDATA[
URI: urn:ietf:params:xml:ns:yang:ietf-netconf-server
Registrant Contact: The NETCONF WG of the IETF.
XML: N/A, the requested URI is an XML namespace.
URI: urn:ietf:params:xml:ns:yang:ietf-system-tle-auth
Registrant Contact: The NETCONF WG of the IETF.
XML: N/A, the requested URI is an XML namespace.
]]></artwork>
</figure>
</t>
<t>This document registers two YANG modules in the
YANG Module Names registry <xref target="RFC6020"/>.</t>
<t>
<figure>
<artwork><![CDATA[
name: ietf-netconf-server
namespace: urn:ietf:params:xml:ns:yang:ietf-netconf-server
prefix: ncserver
reference: RFC XXXX
name: ietf-system-tls-auth
namespace: urn:ietf:params:xml:ns:yang:ietf-system-tls-auth
prefix: sys-tls-auth
reference: RFC XXXX
]]></artwork>
</figure>
</t>
</section>
<section title="Other Considerations">
<t>The YANG module define herein does not itself support
virtual routing and forwarding (VRF). It is expected that
external modules will augment in VRF designations when needed.</t>
</section>
<section title="Acknowledgements">
<t>The authors would like to thank for following for
lively discussions on list and in the halls (ordered
by last name): Andy Bierman, Martin Bjorklund,
Benoit Claise, David Lamparter, Alan Luchuk, Ladislav Lhotka,
Radek Krejci, Tom Petch, and Phil Shafer.</t>
<t>
Juergen Schoenwaelder and was partly funded by Flamingo, a
Network of Excellence project (ICT-318488) supported by the
European Commission under its Seventh Framework Programme.
</t>
</section>
</middle>
<back>
<references title="Normative References">
<reference anchor="RFC2119">
<front>
<title>
Key words for use in RFCs to Indicate Requirement Levels
</title>
<author initials="S.B." surname="Bradner"
fullname="Scott Bradner">
<organization>Harvard University</organization>
</author>
<date month="March" year="1997" />
</front>
<seriesInfo name="BCP" value="14" />
<seriesInfo name="RFC" value="2119" />
</reference>
<reference anchor="RFC4251">
<front>
<title>
The Secure Shell (SSH) Protocol Architecture
</title>
<author initials="T.Y." surname="Ylonen"
fullname="Tatu Ylonen">
<organization>
SSH Communications Security Corp
</organization>
</author>
<author initials="C.L." surname="Lonvick"
fullname="Chris Lonvick">
<organization>
Cisco Systems, Inc.
</organization>
</author>
<date month="January" year="2006" />
</front>
<seriesInfo name="RFC" value="4251" />
</reference>
<reference anchor="RFC4253">
<front>
<title>
The Secure Shell (SSH) Transport Layer Protocol
</title>
<author initials="T.Y." surname="Ylonen"
fullname="Tatu Ylonen">
<organization>
SSH Communications Security Corp
</organization>
</author>
<author initials="C.L." surname="Lonvick"
fullname="Chris Lonvick">
<organization>
Cisco Systems, Inc.
</organization>
</author>
<date month="January" year="2006" />
</front>
<seriesInfo name="RFC" value="4253" />
</reference>
<reference anchor="RFC6020">
<front>
<title>
YANG - A Data Modeling Language for the
Network Configuration Protocol (NETCONF)
</title>
<author initials="M." surname="Bjorklund"
fullname="Martin Bjorklund" role="editor">
<organization>Tail-f Systems</organization>
</author>
<date month="October" year="2010" />
</front>
<seriesInfo name="RFC" value="6020" />
</reference>
<reference anchor='RFC6520'>
<front>
<title>
Transport Layer Security (TLS) and Datagram Transport
Layer Security (DTLS) Heartbeat Extension
</title>
<author initials='R.S.' surname='Seggelmann'
fullname='Robin Seggleman'>
<organization>Muenster University of Applied Sciences</organization>
</author>
<author initials='M.T.' surname='Tuexen'
fullname='Michael Tuexen'>
<organization>Muenster University of Applied Sciences</organization>
</author>
<author initials='M.W.' surname='Williams'
fullname='Michael Williams'>
<organization>GWhiz Arts & Sciences</organization>
</author>
<date year='2012' month='February' />
</front>
<seriesInfo name='RFC' value='6520' />
</reference>
<reference anchor='RFC6536'>
<front>
<title>
Network Configuration Protocol (NETCONF) Access
Control Model
</title>
<author initials='A.' surname='Bierman'
fullname='A. Bierman'>
<organization>YumaWorks</organization>
</author>
<author initials='M.' surname='Bjorklund'
fullname='M. Bjorklund'>
<organization>Tail-f Systems</organization>
</author>
<date year='2012' month='March' />
</front>
<seriesInfo name='RFC' value='6536' />
</reference>
<reference anchor='RFC6991'>
<front>
<title>Common YANG Data Types</title>
<author initials='J.' surname='Schoenwaelder'
fullname='J. Schoenwaelder'>
<organization>Jacobs University</organization>
</author>
<date year='2013' month='July' />
</front>
<seriesInfo name='RFC' value='6991' />
</reference>
<reference anchor="RFC6241">
<front>
<title>NETCONF Configuration Protocol</title>
<author initials="R.E." surname="Enns"
fullname="Rob Enns" role="editor">
<organization>Juniper Networks</organization>
</author>
<author initials="M.B." surname="Bjorklund"
fullname="Martin Bjorklund" role="editor">
<organization>Tail-f Systems</organization>
</author>
<author initials="J.S." surname="Schoenwaelder"
fullname="Juergen Schoenwaelder" role="editor">
<organization>Jacobs University</organization>
</author>
<author initials="A.B." surname="Bierman"
fullname="Andy Bierman" role="editor">
<organization>Brocade</organization>
</author>
<date month="June" year="2011" />
</front>
<seriesInfo name="RFC" value="6241" />
</reference>
<reference anchor="RFC6242">
<front>
<title>Using the NETCONF Protocol over Secure Shell (SSH)</title>
<author initials="M.W." surname="Wasserman"
fullname="Margaret Wasserman">
<organization>Painless Security, LLC</organization>
</author>
<date month="June" year="2011" />
</front>
<seriesInfo name="RFC" value="6242"/>
</reference>
<reference anchor='I-D.ietf-netconf-rfc5539bis'>
<front>
<title>
Using the NETCONF Protocol over Transport Layer
Security (TLS)
</title>
<author initials='M' surname='Badra'
fullname='Mohamad Badra'>
<organization>LIMOS Laboratory</organization>
</author>
<author initials='A' surname='Luchuk'
fullname='Alan Luchuk'>
<organization>SNMP Research, Inc.</organization>
</author>
<author initials='J' surname='Schönwälder'
fullname='Jürgen Schönwälder'>
<organization>Jacobs University</organization>
</author>
<date month='October' day='21' year='2013' />
</front>
<seriesInfo name='Internet-Draft'
value='draft-ietf-netconf-rfc5539bis-04' />
</reference>
<reference anchor='draft-ietf-netmod-snmp-cfg'>
<front>
<title>A YANG Data Model for SNMP Configuration</title>
<author initials='M' surname='Bjorklund'
fullname='Martin Bjorklund'>
<organization>Tail-f Systems</organization>
</author>
<author initials='J' surname='Schönwälder'
fullname='Jürgen Schönwälder'>
<organization>Jacobs University</organization>
</author>
<date month='November' day='5' year='2013' />
</front>
<seriesInfo name='Internet-Draft' value='draft-ietf-netmod-snmp-cfg-03' />
</reference>
<reference anchor='draft-ieft-netconf-reverse-ssh'>
<front>
<title>
NETCONF over SSH Call Home
</title>
<author initials='K.W.' surname='Watsen'
fullname='Kent Watsen'>
<organization>Juniper Networks</organization>
</author>
<date month='May' day='17' year='2014' />
</front>
<seriesInfo name='Internet-Draft'
value='draft-ieft-netconf-reverse-ssh-00' />
</reference>
<reference anchor='draft-ietf-netmod-system-mgmt'>
<front>
<title>
A YANG Data Model for System Management
</title>
<author initials='A.B.' surname='Bierman'
fullname='Andy Bierman'>
<organization>YumaWorks</organization>
</author>
<date month='May' day='14' year='2014' />
</front>
<seriesInfo name='Internet-Draft'
value='draft-ieft-netmod-system-mgmt-16' />
</reference>
</references>
<references title="Informative References">
<reference anchor="RFC3688">
<front>
<title>The IETF XML Registry</title>
<author initials="M.M." surname="Mealling"
fullname="Michael Mealling">
<organization>VeriSign Inc.</organization>
</author>
<date month="January" year="2004" />
</front>
<seriesInfo name="BCP" value="81" />
<seriesInfo name="RFC" value="3688"/>
</reference>
</references>
<section title="Examples">
<section title="SSH Transport Configuration">
<t>
<figure>
<artwork><![CDATA[
INSERT_TEXT_FROM_FILE(refs/ex-ssh.xml)
]]></artwork>
</figure>
</t>
</section>
<section title="TLS Transport Configuration">
<t>
<figure>
<artwork><![CDATA[
INSERT_TEXT_FROM_FILE(refs/ex-tls.xml)
]]></artwork>
</figure>
</t>
</section>
</section>
<section title="Change Log">
<section title="00 to 01">
<t>
<list style="symbols">
<t>Restructured document so it flows better</t>
<t>Added trusted-ca-certs and trusted-client-certs
objects into the ietf-system-tls-auth module</t>
</list>
</t>
</section>
<section title="01 to 02">
<t>
<list style="symbols">
<t>removed the "one-to-many" construct</t>
<t>removed "address" as a key field</t>
<t>removed "network-manager" terminology</t>
<t>moved open issues to github issues</t>
<t>brought TLS client auth back into model</t>
</list>
</t>
</section>
</section>
<section title="Open Issues">
<t>Please see: https://github.com/netconf-wg/server-model/issues.</t>
</section>
</back>
</rfc>
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