NETCONF Client and Server ModelsJuniper Networkskwatsen@juniper.netCisco Networksgarywu@cisco.comJacobs University Bremenj.schoenwaelder@jacobs-university.de
Operations
NETCONF Working GroupThis document defines two YANG modules, one module to
configure a NETCONF client and the other module to configure
a NETCONF server. Both modules support both the SSH and
TLS transport protocols, and support both standard NETCONF
and NETCONF Call Home connections.This draft contains many placeholder values that need to be replaced
with finalized values at the time of publication. This note summarizes
all of the substitutions that are needed. No other RFC Editor
instructions are specified elsewhere in this document.This document contains references to other drafts in progress, both in
the Normative References section, as well as in body text throughout.
Please update the following references to reflect their final RFC assignments:
I-D.ietf-netconf-keystoreI-D.ietf-netconf-ssh-client-serverI-D.ietf-netconf-tls-client-serverArtwork in this document contains shorthand references to drafts in
progress. Please apply the following replacements:
XXXX --> the assigned RFC value for this draftYYYY --> the assigned RFC value for I-D.ietf-netconf-ssh-client-serverZZZZ --> the assigned RFC value for I-D.ietf-netconf-tls-client-serverArtwork in this document contains placeholder values for the date of publication of this
draft. Please apply the following replacement:
2017-06-13 --> the publication date of this draftThe following Appendix section is to be removed prior to publication:
Appendix A. Change LogThis document defines two YANG modules,
one module to configure a NETCONF client and the other module to
configure a NETCONF server. Both modules support both the SSH and
TLS transport protocols, and support both standard NETCONF and NETCONF
Call Home connections.NETCONF is defined by . SSH is defined by
, , and
. TLS is defined by .
NETCONF Call Home is defined by ).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 .A simplified graphical representation of the data models
is used in this document. The meaning of the symbols in
these diagrams is as follows:
Brackets "[" and "]" enclose list keys.Braces "{" and "}" enclose feature names, and indicate
that the named feature must be present for the subtree
to be present.Abbreviations before data node names: "rw" means
configuration (read-write) and "ro" state data
(read-only).Symbols after data node names: "?" means an optional
node, "!" means a presence container, and "*" denotes a
list and leaf-list.Parentheses enclose choice and case nodes, and case
nodes are also marked with a colon (":").Ellipsis ("...") stands for contents of subtrees that
are not shown.The NETCONF client model presented in this section supports both clients
initiating connections to servers, as well as clients listening
for connections from servers calling home.This model supports both the SSH and TLS transport
protocols, using the SSH client and TLS client groupings defined in
and
respectively.All private keys and trusted certificates are held in the
keystore model defined in .YANG feature statements are used to enable implementations to advertise
which parts of the model the NETCONF client supports.Note: all lines are folded at column 71 with no '\' character.The following example illustrates configuring a NETCONF
client to initiate connections, using both the SSH and TLS
transport protocols, as well as listening for call-home
connections, again using both the SSH and TLS transport
protocols.This example is consistent with the examples presented in
Section 2.2 of .This YANG module imports YANG types from and .The NETCONF server model presented in this section supports servers
both listening for connections as well as initiating call-home
connections.This model supports both the SSH and TLS transport
protocols, using the SSH server and TLS server groupings defined in
and
respectively.All private keys and trusted certificates are held in the
keystore model defined in .YANG feature statements are used to enable implementations to advertise
which parts of the model the NETCONF server supports.Note: all lines are folded at column 71 with no '\' character.The following example illustrates configuring a NETCONF server
to listen for NETCONF client connections using both the SSH and
TLS transport protocols, as well as configuring call-home to two
NETCONF clients, one using SSH and the other using TLS.This example is consistent with the examples presented in
Section 2.2 of .This YANG module imports YANG types from and .Editorial: this section is a hold over from before, previously called
"Objectives". It was only written two support the "server" (not the "client").
The question is if it's better to add the missing "client" parts, or remove
this section altogether.The primary purpose of the YANG modules defined herein is
to enable the configuration of the NETCONF client and servers.
This scope includes the following objectives:The YANG module should support all current NETCONF
transports, namely NETCONF over SSH ,
NETCONF over TLS , and to be
extensible to support future transports as necessary.Because implementations may not support all transports,
the modules should use YANG "feature" statements
so that implementations can accurately advertise which
transports are supported.Servers may have a multiplicity of host-keys or server-certificates
from which subsets may be selected for specific uses. For instance,
a NETCONF server may want to use one set of SSH host-keys when listening
on port 830, and a different set of SSH host-keys when calling
home. The data models provided herein should enable configuration
of which keys to use on a per-use basis.When a certificate is used to authenticate a NETCONF client,
there is a need to configure the server to know how to authenticate the
certificates. The server should be able to authenticate the client's
certificate either by using path-validation to a configured trust anchor
or by matching the client-certificate to one previously configured.When a client certificate is used for TLS client authentication,
the NETCONF server must be able to derive a username from the
authenticated certificate. Thus the modules defined herein should enable
this mapping to be configured.The NETCONF protocols were originally defined as having the
server opening a port to listen for client connections. More recently
the NETCONF working group defined support for call-home
(), enabling the server to
initiate the connection to the client. Thus the modules defined herein
should enable configuration for both listening for connections and
calling home. Because implementations may not support both listening
for connections and calling home, YANG "feature" statements
should be used so that implementation can accurately
advertise the connection types it supports.The following objectives only pertain to call home connections.A NETCONF server may be managed by more than one NETCONF client.
For instance, a deployment may have one client for provisioning and
another for fault monitoring. Therefore, when it is desired for a
server to initiate call home connections, it should be able to do
so to more than one client.A NETCONF client managing a NETCONF server may implement a
high-availability strategy employing a multiplicity of
active and/or passive endpoint. Therefore, when it is
desired for a server to initiate call home connections,
it should be able to connect to any of the client's endpoints.Assuming a NETCONF client has more than one endpoint, then
it becomes necessary to configure how a NETCONF server should
reconnect to the client should it lose its connection to one
the client's endpoints. For instance, the NETCONF server may
start with first endpoint defined in a user-ordered list of
endpoints or with the last endpoints it was connected to.NETCONF clients may vary greatly on how frequently they need
to interact with a NETCONF server, how responsive interactions
need to be, and how many simultaneous connections they can
support. Some clients may need a persistent connection to
servers to optimize real-time interactions, while others
prefer periodic interactions in order to minimize resource
requirements. Therefore, when it is necessary for server
to initiate connections, it should be configurable if the
connection is persistent or periodic.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.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 NETCONF client requirements, and therefore
keep-alive settings should be configurable on a
per-client basis.If a periodic connection is desired, it is necessary for
the NETCONF server to know how often it should connect. This
frequency determines the maximum amount of time a NETCONF
client may have to wait to send data to a server. A server may
connect to a client before this interval expires if desired
(e.g., to send data to a client).A denial of service (DoS) attack MAY occur if the NETCONF server limits the
maximum number of NETCONF sessions it will accept (i.e. the 'max-sessions' field
in the ietf-netconf-server module is not zero) and either the "hello-timeout"
or "idle-timeout" fields in ietf-netconf-server module have been set to indicate
the NETCONF server should wait forever (i.e. set to zero).The YANG module defined in this document uses groupings defined in
and
. Please see the Security
Considerations section in those documents for concerns related those groupings.The YANG module defined in this document is designed to be accessed via YANG
based management protocols, such as NETCONF and
RESTCONF . Both of these protocols have mandatory-to-implement
secure transport layers (e.g., SSH, TLS) with mutual authentication.The NETCONF access control model (NACM) provides the means
to restrict access for particular users to a pre-configured subset of all available
protocol operations and content.There are a number of data nodes defined in this YANG module that are
writable/creatable/deletable (i.e., config true, which is the default). These data
nodes may be considered sensitive or vulnerable in some network environments. Write
operations (e.g., edit-config) to these data nodes without proper protection can
have a negative effect on network operations. These are the subtrees and data nodes
and their sensitivity/vulnerability:
Some of the readable data nodes in this YANG module may be considered sensitive
or vulnerable in some network environments. It is thus important to control read
access (e.g., via get, get-config, or notification) to these data nodes. These are
the subtrees and data nodes and their sensitivity/vulnerability:
Some of the RPC operations in this YANG module may be considered sensitive or
vulnerable in some network environments. It is thus important to control access
to these operations. These are the operations and their sensitivity/vulnerability:
This document registers two URIs in the IETF XML
registry . Following the format in
, the following registrations are
requested:This document registers two YANG modules in the
YANG Module Names registry .
Following the format in , the
the following registrations are requested: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,
Mehmet Ersue, Balázs Kovács, David Lamparter, Alan Luchuk, Ladislav Lhotka,
Radek Krejci, Tom Petch, Phil Shafer, Sean Turner, and
Bert Wijnen.
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.
This draft was split out from draft-ietf-netconf-server-model-09.Added in previously missing ietf-netconf-client module.Added in new features 'listen' and 'call-home' so future transports
can be augmented in.Renamed "keychain" to "keystore".Added to ietf-netconf-client ability to connected to a cluster
of endpoints, including a reconnection-strategy.Added to ietf-netconf-client the ability to configure connection-type
and also keep-alive strategy.Updated both modules to accomodate new groupings in the ssh/tls
drafts.Refined use of tls-client-grouping to add a must statement
indicating that the TLS client must specify a client-certificate.Changed 'netconf-client' to be a grouping (not a container).