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draft-ietf-netconf-udp-notif-17.xml
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<?xml version="1.0" encoding="US-ASCII"?>
<!DOCTYPE rfc>
<?rfc toc="yes"?>
<?rfc tocompact="yes"?>
<?rfc tocdepth="3"?>
<?rfc tocindent="yes"?>
<?rfc symrefs="yes"?>
<?rfc sortrefs="yes"?>
<?rfc comments="yes"?>
<?rfc inline="yes"?>
<?rfc compact="yes"?>
<?rfc subcompact="no"?>
<rfc category="std" docName="draft-ietf-netconf-udp-notif-17"
ipr="trust200902" consensus="true" submissionType="IETF">
<front>
<title abbrev="UDP-Notif">UDP-based Transport for Configured
Subscriptions</title>
<author fullname="Guangying Zheng" initials="G." surname="Zheng">
<organization>Huawei</organization>
<address>
<postal>
<street>101 Yu-Hua-Tai Software Road</street>
<city>Nanjing</city>
<code/>
<region>Jiangsu</region>
<country>China</country>
</postal>
<phone/>
<facsimile/>
<email>[email protected]</email>
</address>
</author>
<author fullname="Tianran Zhou" initials="T." surname="Zhou">
<organization>Huawei</organization>
<address>
<postal>
<street>156 Beiqing Rd., Haidian District</street>
<city>Beijing</city>
<region/>
<code/>
<country>China</country>
</postal>
<phone/>
<facsimile/>
<email>[email protected]</email>
<uri/>
</address>
</author>
<author fullname="Thomas Graf" initials="T." surname="Graf">
<organization>Swisscom</organization>
<address>
<postal>
<street>Binzring 17</street>
<city>Zuerich 8045</city>
<region/>
<code/>
<country>Switzerland</country>
</postal>
<phone/>
<facsimile/>
<email>[email protected]</email>
<uri/>
</address>
</author>
<author fullname="Pierre Francois" initials="P." surname="Francois">
<organization>INSA-Lyon</organization>
<address>
<postal>
<street/>
<city>Lyon</city>
<region/>
<code/>
<country>France</country>
</postal>
<phone/>
<facsimile/>
<email>[email protected]</email>
<uri/>
</address>
</author>
<author fullname="Alex Huang Feng" initials="A." surname="Huang Feng">
<organization>INSA-Lyon</organization>
<address>
<postal>
<street/>
<city>Lyon</city>
<region/>
<code/>
<country>France</country>
</postal>
<phone/>
<facsimile/>
<email>[email protected]</email>
<uri/>
</address>
</author>
<author fullname="Paolo Lucente" initials="P." surname="Lucente">
<organization>NTT</organization>
<address>
<postal>
<street>Siriusdreef 70-72</street>
<city>Hoofddorp, WT 2132</city>
<region/>
<code/>
<country>NL</country>
</postal>
<phone/>
<facsimile/>
<email>[email protected]</email>
<uri/>
</address>
</author>
<date day="1" month="December" year="2024"/>
<workgroup>NETCONF</workgroup>
<abstract>
<t>This document describes a UDP-based protocol for YANG notifications
to collect data from network nodes. A shim header is proposed to
facilitate the data streaming directly from the publishing process on
network processor of line cards to receivers. The objective is to
provide a lightweight approach to enable higher frequency and less
performance impact on publisher and receiver processes compared to
already established notification mechanisms.</t>
</abstract>
<note title="Requirements Language">
<t>The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP 14
<xref target="RFC2119"/> <xref target="RFC8174"/> when, and only when,
they appear in all capitals, as shown here.</t>
</note>
</front>
<middle>
<section title="Introduction">
<t>The mechanism to support a subscription of a continuous and
customized stream of updates from a YANG datastore <xref
target="RFC8342"/> is defined in <xref target="RFC8639"/> and <xref
target="RFC8641"/> and is abbreviated as Sub-Notif. Requirements for
Subscription to YANG Datastores are defined in <xref
target="RFC7923"/>.</t>
<t>The mechanism separates the management and control of subscriptions
from the transport used to deliver the data. Three transport mechanisms,
namely <xref target="RFC8640">NETCONF transport</xref>, <xref
target="RFC8650">RESTCONF transport</xref>, and <xref
target="I-D.ietf-netconf-https-notif">HTTPS transport</xref> have been
defined so far for such notification messages.</t>
<t>While powerful in their features and general in their architecture,
the currently available transport mechanisms need to be complemented to
support data publications at high frequency with low overhead. This is
important for network nodes that feature a distributed architecture with sparse
resources on components specialized for packet forwarding. The currently
available transports are TCP-based requiring the maintenance of connections,
states and retransmissions, which is not necessary for high-frequency continuous
notification content, typically published directly from network processors on line cards.</t>
<t>This document specifies a transport option for Sub-Notif that
leverages UDP. Specifically, it facilitates the distributed data
collection mechanism described in <xref
target="I-D.ietf-netconf-distributed-notif"/>. In the case of publishing
from multiple network processors on multiple line cards, centralized
designs require data to be internally forwarded from those network
processors to the push server, presumably on a route processor, which
then combines the individual data items into a single consolidated
stream. The centralized data collection mechanism can result in a
performance bottleneck, especially when large amounts of data are
involved.</t>
<t>What is needed is a mechanism that allows for directly publishing
from multiple network processors on line cards, without passing them
through an additional processing stage for internal consolidation. The
proposed UDP-based transport allows for such a distributed data
publishing approach.</t>
<t><list style="symbols">
<t>Firstly, a UDP approach reduces the burden of maintaining a large
pool of active TCP connections at the receiver, notably in cases
where it collects data from network processors on line cards from a
large amount of network nodes.</t>
<t>Secondly, as no connection state needs to be maintained, UDP
encapsulation can be easily implemented by the hardware of the
publication streamer, which further improves performance.</t>
<t>Ultimately, such advantages allow for a larger data analysis
feature set, as more voluminous, finer grained data sets can be
streamed to the receiver.</t>
</list></t>
<t>The transport described in this document can be used for transmitting
notification messages over both IPv4 and IPv6.</t>
<t>This document describes the notification mechanism. It is intended to
be used in conjunction with <xref target="RFC8639"/>, extended by <xref
target="I-D.ietf-netconf-distributed-notif"/>.</t>
<t><xref target="sec_transport"/> describes the control of the proposed
transport mechanism. <xref target="sec_ups_transport"/> details the
notification mechanism and message format. <xref target="sec_options"/>
describes the use of options in the notification message header. <xref
target="sec_applicability"/> covers the applicability of the proposed
mechanism. <xref target="sec_dtls_udp_notif"/> describes a mechanism to
secure the protocol in open networks.</t>
</section>
<section anchor="sec_transport"
title="Configured Subscription to UDP-Notif">
<t>This section describes how the proposed mechanism can be controlled
using subscription channels based on NETCONF or RESTCONF.</t>
<t>As specified in Sub-Notif, configured subscriptions contain the location
information of all the receivers, including the IP address and the port number,
so that the publisher can actively send UDP-Notif messages to the corresponding
receivers.</t>
<t>Note that receivers MAY NOT be already up and running when the
configuration of the subscription takes effect on the monitored network
node. The first message MUST be a separate subscription-started
notification to indicate the Receiver that the stream has started
flowing. Then, the notifications can be sent immediately without delay.
All the subscription state notifications, as defined in Section 2.7 of
<xref target="RFC8639"/>, MUST be encapsulated in separate notification
messages.</t>
<t>Note also that the receiver nodes can be different from the nodes
managing the subscription. Therefore, publishers MAY NOT be aware of
the capabilities supported by the receivers.</t>
</section>
<section anchor="sec_ups_transport" title="UDP-Based Transport">
<t>In this section, we specify the UDP-Notif Transport behavior. <xref
target="sec_design"/> describes the general design of the solution.
<xref target="sec_ups_format"/> specifies the UDP-Notif message format
and <xref target="sec_encoding"/> describes the encoding of the message
payload. <!-- <xref target="sec_options"/> describes a generic optional sub TLV
format. <xref target="sec_fragmentation"/> uses such options to provide
a segmentation solution for large UDP-Notif message payloads. --></t>
<section anchor="sec_design" title="Design Overview">
<t>As specified in Sub-Notif, the YANG data is encapsulated in a
NETCONF/RESTCONF notification message, which is then encapsulated and
carried using a transport protocols such as TLS or HTTP2. This
document defines a UDP based transport. <xref
target="fig_ups_message"/> illustrates the structure of an UDP-Notif
message.</t>
<t><list style="symbols">
<t>The Message Header contains information that facilitate the
message transmission before deserializing the notification
message.</t>
<t>Notification Message is the encoded content that is transported
by the publication stream. The common encoding methods are listed
in <xref target="sec_ups_format"/>. The structure of the
Notification Message is defined in Section 2.6 of <xref
target="RFC8639"/> and a YANG model has been proposed in <xref
target="I-D.ahuang-netconf-notif-yang"/>. <xref
target="I-D.ietf-netconf-notification-messages"/> proposes a
structure to send bundled notifications in a single message.</t>
</list></t>
<t><figure anchor="fig_ups_message" title="UDP-Notif Message Overview">
<artwork align="center"><![CDATA[
+-------+ +--------------+ +--------------+
| UDP | | Message | | Notification |
| | | Header | | Message |
+-------+ +--------------+ +--------------+
]]></artwork>
</figure></t>
<t/>
</section>
<section anchor="sec_ups_format"
title="Format of the UDP-Notif Message Header">
<t>The UDP-Notif Message Header contains information that facilitate
the message transmission before deserializing the notification
message. The data format is shown in <xref
target="fig_ups_header"/>.</t>
<figure anchor="fig_ups_header"
title="UDP-Notif Message Header Format">
<artwork align="center"><![CDATA[
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-----+-+-------+---------------+-------------------------------+
| Ver |S| MT | Header Len | Message Length |
+-----+-+-------+---------------+-------------------------------+
| Message Publisher ID |
+---------------------------------------------------------------+
| Message ID |
+---------------------------------------------------------------+
~ Options ~
+---------------------------------------------------------------+
]]></artwork>
</figure>
<t/>
<t>The Message Header contains the following field:</t>
<t><list style="symbols">
<t>Ver indicates the UDP-Notif protocol header version. The values
are allocated by the IANA registry "UDP-Notif header version". The
current header version number is 1.</t>
<t>S represents the space of media type specified in the MT field.
When S is unset, MT represents the standard media types as defined
in this document. When S is set, MT represents a private space to
be freely used for non standard encodings. When S is set, the
Private Encoding Option defined in <xref target="sec_enc_opt"/>
SHOULD be present in the UDP-Notif message header.</t>
<t>MT is a 4 bit identifier to indicate the media type used for
the Notification Message. 16 types of encoding can be expressed.
When the S bit is unset, the following values apply:<list
style="symbols">
<t>0: Reserved;</t>
<t>1: application/yang-data+json <xref target="RFC8040"/></t>
<t>2: application/yang-data+xml <xref target="RFC8040"/></t>
<t>3: application/yang-data+cbor <xref target="RFC9254"/></t>
</list></t>
<t>Header Len is the length of the message header in octets,
including both the fixed header and the options.</t>
<t>Message Length is the total length of the UDP-Notif message
within one UDP datagram, measured in octets, including the message
header. When the Notification Message is segmented using the
Segmentation Options defined in <xref target="sec_fragmentation"/>
the Message Length is the total length of the current, segmented
UDP-Notif message, not the length of the entire Notification
message.</t>
<t>Message Publisher ID is a 32-bit identifier defined in <xref
target="I-D.ietf-netconf-distributed-notif"/>. This identifier is
unique to the publisher node and identifies the publishing process
of the node to allow the disambiguation of an information source.
Message unicity is obtained from the conjunction of the Message
Publisher ID and the Message ID field described below. If Message
Publisher ID unicity is not preserved through the collection
domain, the source IP address of the UDP datagram SHOULD be used
in addition to the Message Publisher ID to identify the
information source. If a transport layer relay is used, Message
Publisher ID unicity must be preserved through the collection
domain.</t>
<t>The Message ID is generated continuously by the publisher of
UDP-Notif messages. A publisher MUST use different Message ID
values for different messages generated with the same Message
Publisher ID. Note that the main purpose of the Message ID is to
reconstruct messages which are segmented using the segmentation
option described in section <xref target="sec_fragmentation"/>.
The Message ID values SHOULD be incremented by one for each
successive message originated with the same Message Publisher ID,
so that message loss can be detected. When the last value (2^32-1)
of Message ID has been generated, the Message ID wraps around and
restarts at 0. Different subscribers MAY share the same Message ID
sequence.</t>
<t>Options is a variable-length field in the TLV format. When the
Header Length is larger than 12 octets, which is the length of the
fixed header, Options TLVs follow directly after the fixed message
header (i.e., Message ID). The details of the options are
described in <xref target="sec_options"/>.</t>
</list></t>
<t>All the binary fields MUST be encoded in network byte order (big
endian).</t>
<t/>
</section>
<section anchor="sec_encoding" title="Data Encoding">
<t>UDP-Notif message data can be encoded in CBOR, XML or JSON format.
It is conceivable that additional encodings may be supported in the
future. This can be accomplished by augmenting the subscription data
model with additional identity statements used to refer to requested
encodings.</t>
<t>Private encodings can be using the S bit of the header. When the S
bit is set, the value of the MT field is left to be defined and agreed
upon by the users of the private encoding. An option is defined in
<xref target="sec_enc_opt"/> for more verbose encoding descriptions
than what can be described with the MT field.</t>
<t>Implementation MAY support multiple encoding methods per
subscription. When bundled notifications are supported between the
publisher and the receiver, only subscribed notifications with the
same encoding can be bundled in a given message.</t>
</section>
</section>
<section anchor="sec_options" title="Options">
<t>All the options are defined with the following format, illustrated in
<xref target="fig_ups_message_options"/>.</t>
<t><figure anchor="fig_ups_message_options"
title="Generic Option Format">
<artwork align="center"><![CDATA[
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+---------------+---------------+--------------------------------
| Type | Length | Variable-length data
+---------------+---------------+--------------------------------]]></artwork>
</figure></t>
<t><list style="symbols">
<t>Type: 1 octet describing the option type;</t>
<t>Length: 1 octet representing the total number of octets in the
TLV, including the Type and Length fields;</t>
<t>Variable-length data: 0 or more octets of TLV Value.</t>
</list></t>
<t>When more than one option is used in the UDP-Notif header, options
MUST be ordered by the Type value. Messages with unordered options MAY
be dropped by the Receiver.</t>
<section anchor="sec_fragmentation" title="Segmentation Option">
<t>The UDP payload length is limited to 65527 bytes (65535 - 8 bytes).
Application level headers will make the actual payload shorter. Even
though binary encodings such as CBOR may not require more space than what
is left, more voluminous encodings such as JSON and XML may suffer from
this size limitation. Although IPv4 and IPv6 publishers can fragment
outgoing packets exceeding their Maximum Transmission Unit (MTU),
fragmented IP packets may not be desired for operational and
performance reasons.</t>
<t>Consequently, implementations of the mechanism SHOULD provide a
configurable max-segment-size option to control the maximum size of a
UDP-Notif segment.</t>
<figure anchor="fig_frag_option" title="Segmentation Option Format">
<artwork align="center"><![CDATA[
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+---------------+---------------+-----------------------------+-+
| Type | Length | Segment Number |L|
+---------------+---------------+-----------------------------+-+
]]></artwork>
</figure>
<t>The Segmentation Option is to be included when the message content
is segmented into multiple segments. Different segments of one message
share the same Message ID. An illustration is provided in <xref
target="fig_frag_option"/>. The fields of this TLV are:</t>
<t><list style="symbols">
<t>Type: Generic option field which indicates a Segmentation
Option. The Type value is to be assigned TBD1.</t>
<t>Length: Generic option field which indicates the length of this
option in octets. It is a fixed value of 4 octets for the Segmentation
Option.</t>
<t>Segment Number: 15-bit value indicating the sequence number of
the current segment. The first segment of a segmented message has
a Segment Number value of 0. The Segment Number cannot wrap around.</t>
<t>L: is a flag to indicate whether the current segment is the
last one of the message. When 0 is set, the current segment is not
the last one. When 1 is set, the current segment is the last one,
meaning that the total number of segments used to transport this
message is the value of the current Segment Number + 1.</t>
</list></t>
<t>An implementation of this specification SHOULD NOT rely on IP
fragmentation by default to carry large messages. An implementation of
this specification SHOULD either restrict the size of individual
messages carried over this protocol, or support the segmentation
option. The implementor or user SHOULD configure the max-segment-size
so that the size of a UDP-Notif segment and the size of the IP layer
together does not exceed the MTU of the egress interface.</t>
<t>When a message has multiple options and is segmented using the
described mechanism, all the options MUST be present on the first
segment ordered by the options Type. The rest of segmented messages
MAY include all the options ordered by options type.</t>
<t>The receiver SHOULD support the reception of unordered segments.
The implementation of the receiver SHOULD provide an option to discard
the received segments if, after some time, one of the segments is still
missing and the reassembly of the message is not possible. If the receiver
collects a segment more than once, the implementation SHOULD drop the
duplicate segment.</t>
</section>
<section anchor="sec_enc_opt" title="Private Encoding Option">
<t>The space to describe private encodings in the MT field of the
UDP-Notif header being limited, an option is provided to describe
custom encodings. The fields of this option are as follows.</t>
<figure anchor="fig_enc_option" title="Private Encoding Option Format">
<artwork align="center"><![CDATA[
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+---------------+---------------+--------------------------------
| Type | Length | Variable length enc. descr.
+---------------+---------------+--------------------------------
]]></artwork>
</figure>
<t><list style="symbols">
<t>Type: Generic option field which indicates a Private Encoding
Option. The Type value is to be assigned TBD2.</t>
<t>Length: Generic option field which indicates the length of this
option in octets. It is a variable value.</t>
<t>Enc. Descr: The description of the private encoding used for
this message. The values to be used for such private encodings is
left to be defined by the users of private encodings.</t>
</list></t>
<t>This option SHOULD only be used when the S bit of the header is
set, as providing a private encoding description for standard
encodings is meaningless.</t>
</section>
</section>
<section anchor="sec_applicability" title="Applicability">
<t>In this section, we provide an applicability statement for the
proposed mechanism, following the recommendations of <xref
target="RFC8085"/>.</t>
<t>The proposed mechanism falls in the category of UDP applications
"designed for use within the network of a single network operator or on
networks of an adjacent set of cooperating network operators, to be
deployed in controlled environments", as defined in <xref
target="RFC8085"/>. Implementations of the proposed mechanism SHOULD
thus follow the recommendations in place for such specific applications.
In the following, we discuss recommendations on congestion control,
message size guidelines, reliability considerations and security
considerations.</t>
<t>The main use case of the proposed mechanism is the collection of
statistical metrics for accounting purposes, where potential loss is not
a concern, but should however be reported (such as IPFIX Flow Records
exported with UDP <xref target="RFC7011"/>). Such metrics are typically
exported in a periodical subscription as described in Section 3.1 of
<xref target="RFC8641"/>.</t>
<section anchor="sec_congestion_control" title="Congestion Control">
<t>The proposed application falls into the category of applications
performing transfer of large amounts of data. It is expected that the
operator using the solution configures QoS on its related flows. As
per <xref target="RFC8085"/>, such applications MAY choose not to
implement any form of congestion control, but follow the following
principles.</t>
<t>It is NOT RECOMMENDED to use the proposed mechanism over
congestion-sensitive network paths. The only environments where
UDP-Notif is expected to be used are managed networks. The deployments
require that the network path has been explicitly provisioned to
handle the traffic through traffic engineering mechanisms, such as
rate limiting or capacity reservations.</t>
<t>Implementation of the proposal SHOULD NOT push unlimited amounts of
traffic by default, and SHOULD require the users to explicitly
configure such a mode of operation.</t>
<t>Burst mitigation through packet pacing is RECOMMENDED. Disabling
burst mitigation SHOULD require the users to explicitly configure such
a mode of operation.</t>
<t>Applications SHOULD monitor packet losses and provide means to the
user for retrieving information on such losses. The UDP-Notif Message
ID can be used to deduce congestion based on packet loss detection.
Hence the receiver can notify the Publisher to use a lower streaming
rate. The interaction to control the streaming rate on the Publisher
is out of the scope of this document.</t>
</section>
<section anchor="sec_message_size" title="Message Size">
<t><xref target="RFC8085"/> recommends not to rely on IP fragmentation
for messages whose size result in IP packets exceeding the MTU along
the path. The segmentation option of the current specification permits
segmentation of the UDP Notif message content without relying on IP
fragmentation. Implementation of the current specification SHOULD
allow for the configuration of the MTU.</t>
<t>It is RECOMMENDED that the size of a Notification Message is
small and segmentation does not result in segmenting the message into too
much segments to avoid dropping the entire message when there is a lost
segment. When a Notification Message is large, it is RECOMMENDED to use a
reliable transport such as HTTPS-notif
<xref target="I-D.ietf-netconf-https-notif"/>.</t>
</section>
<section anchor="sec_reliability" title="Reliability">
<t>A receiver implementation for this protocol SHOULD deal with
potential loss of packets carrying a part of segmented payload, by
discarding packets that were received, but cannot be re-assembled as a
complete message within a given amount of time. This time SHOULD be
configurable.</t>
</section>
</section>
<section anchor="sec_dtls_udp_notif" title="Secured layer for UDP-Notif">
<t>In unsecured networks, which are not authenticated and encrypted on
layers below transport, UDP-Notif messages MUST be secured or
encrypted. In this section, a mechanism using DTLS 1.3 to secure
UDP-Notif protocol is presented. The following sections defines the
requirements for the implementation of the secured layer of DTLS for
UDP-Notif. No DTLS 1.3 extensions are defined in this document.</t>
<t>The DTLS 1.3 protocol <xref target="RFC9147"/> is designed to meet
the requirements of applications that need to secure datagram transport.
Implementations using DTLS to secure UDP-Notif messages MUST use DTLS
1.3 protocol as defined in <xref target="RFC9147"/>.</t>
<t>When this security layer is used, the Publisher MUST always be a DTLS
client, and the Receiver MUST always be a DTLS server. The Receivers
MUST support accepting UDP-Notif Messages on the specified UDP port, but
MAY be configurable to listen on a different port. The Publisher MUST
support sending UDP-Notif messages to the specified UDP port, but MAY be
configurable to send messages to a different port. The Publisher MAY use
any source UDP port for transmitting messages.</t>
<section anchor="sec_session_lifecycle" title="Session lifecycle">
<t>This section describes the lifecycle of UDP-Notif messages when
they are excrypted using DTLS.</t>
<section title="DTLS Session Initiation">
<t>The Publisher initiates a DTLS connection by sending a DTLS
ClientHello to the Receiver. Implementations MAY support the denial
of service countermeasures defined by DTLS 1.3 if a given deployment
can ensure that DoS attacks are not a concern. When these
countermeasures are used, the Receiver responds with a DTLS
HelloRetryRequest containing a stateless cookie. The Publisher sends
a second DTLS ClientHello message containing the received cookie.
Details can be found in Section 5.1 of <xref target="RFC9147"/>.</t>
<t>When DTLS is implemented, the Publisher MUST NOT send any
UDP-Notif messages before the DTLS handshake has successfully
completed. Early data mechanism (also known as 0-RTT data) as
defined in <xref target="RFC9147"/> MUST NOT be used.</t>
<t>Implementations of this security layer MUST support DTLS 1.3
<xref target="RFC9147"/> and MUST support the mandatory to implement
cipher suite TLS_AES_128_GCM_SHA256 and SHOULD implement
TLS_AES_256_GCM_SHA384 and TLS_CHACHA20_POLY1305_SHA256 cipher
suites, as specified in TLS 1.3 <xref target="RFC8446"/>. If
additional cipher suites are supported, then implementations MUST
NOT negotiate a cipher suite that employs NULL integrity or
authentication algorithms.</t>
<t>Where confidentiality protection with DTLS is required,
implementations must negotiate a cipher suite that employs a
non-NULL encryption algorithm.</t>
</section>
<section title="Publish Data">
<t>When DTLS is used, all UDP-Notif messages MUST be published as
DTLS "application_data". It is possible that multiple UDP-Notif
messages are contained in one DTLS record, or that a publication
message is transferred in multiple DTLS records. The application
data is defined with the following ABNF <xref target="RFC5234"/>
expression:</t>
<t>APPLICATION-DATA = 1*UDP-NOTIF-FRAME</t>
<t>UDP-NOTIF-FRAME = MSG-LEN SP UDP-NOTIF-MSG</t>
<t>MSG-LEN = NONZERO-DIGIT *DIGIT</t>
<t>SP = %d32</t>
<t>NONZERO-DIGIT = %d49-57</t>
<t>DIGIT = %d48 / NONZERO-DIGIT</t>
<t>UDP-NOTIF-MSG is defined in <xref
target="sec_ups_transport"/>.</t>
<t>The Publisher SHOULD attempt to avoid IP fragmentation by using
the Segmentation Option in the UDP-Notif message.</t>
</section>
<section title="Session termination">
<t>A Publisher MUST close the associated DTLS connection if the
connection is not expected to deliver any UDP-Notif Messages later.
It MUST send a DTLS close_notify alert before closing the
connection. A Publisher (DTLS client) MAY choose to not wait for the
Receiver's close_notify alert and simply close the DTLS connection.
Once the Receiver gets a close_notify from the Publisher, it MUST
reply with a close_notify.</t>
<t>When no data is received from a DTLS connection for a long time,
the Receiver MAY close the connection. Implementations SHOULD set
the timeout value to 10 minutes but application specific profiles
MAY recommend shorter or longer values. The Receiver (DTLS server)
MUST attempt to initiate an exchange of close_notify alerts with the
Publisher before closing the connection. Receivers that are
unprepared to receive any more data MAY close the connection after
sending the close_notify alert.</t>
<t>Although closure alerts are a component of TLS and so of DTLS,
they, like all alerts, are not retransmitted by DTLS and so may be
lost over an unreliable network.</t>
</section>
</section>
</section>
<section title="A YANG Data Model for Management of UDP-Notif">
<section title="YANG to configure UDP-Notif">
<t>The YANG model described in <xref target="sec_yang_model"/> defines
a new receiver instance for UDP-Notif transport. When this transport
is used, four new leaves and a dtls container allow configuring
UDP-Notif receiver parameters.</t>
<t>The source address of the UDP-Notif message can be configured using the
"source-address" leaf at the subscription level as defined in
<xref target="RFC8639" section="2.5" sectionFormat="of"/> or by setting
the leaf "local-address" using the YANG model proposed in this document.
When both are configured, the UDP-Notif message MUST use the address configured
in the "local-address" leaf defined in the YANG proposed in this document.
</t>
<t><figure>
<artwork><![CDATA[
module: ietf-udp-notif-transport
augment /sn:subscriptions/snr:receiver-instances
/snr:receiver-instance/snr:transport-type:
+--:(udp-notif)
+--rw udp-notif-receiver
+--rw remote-address inet:host
+--rw remote-port inet:port-number
+--rw local-address? inet:ip-address
| {local-binding-supported}?
+--rw local-port? inet:port-number
| {local-binding-supported}?
+--rw dtls! {dtls13}?
| +--rw client-identity!
| | +--rw (auth-type)
| | +--:(certificate) {client-ident-x509-cert}?
| | | ...
| | +--:(raw-public-key)
| | | {client-ident-raw-public-key}?
| | | ...
| | +--:(tls13-epsk) {client-ident-tls13-epsk}?
| | ...
| +--rw server-authentication
| | +--rw ca-certs! {server-auth-x509-cert}?
| | | +--rw (inline-or-truststore)
| | | ...
| | +--rw ee-certs! {server-auth-x509-cert}?
| | | +--rw (inline-or-truststore)
| | | ...
| | +--rw raw-public-keys! {server-auth-raw-public-key}?
| | | +--rw (inline-or-truststore)
| | | ...
| | +--rw tls13-epsks? empty
| | {server-auth-tls13-epsk}?
| +--rw hello-params {tlscmn:hello-params}?
| | +--rw tls-versions
| | | +--rw min? identityref
| | | +--rw max? identityref
| | +--rw cipher-suites
| | +--rw cipher-suite*
| | tlscsa:tls-cipher-suite-algorithm
| +--rw keepalives {tls-client-keepalives}?
| +--rw peer-allowed-to-send? empty
| +--rw test-peer-aliveness!
| +--rw max-wait? uint16
| +--rw max-attempts? uint8
+--rw enable-segmentation? boolean {segmentation}?
+--rw max-segment-size? uint32 {segmentation}?
]]></artwork>
</figure></t>
</section>
<section anchor="sec_yang_model" title="YANG Module">
<t>This YANG module is used to configure, on a publisher, a receiver
willing to consume notification messages. This module augments the
"ietf-subscribed-notif-receivers" module to define a UDP-Notif
transport receiver. The grouping "udp-notif-receiver-grouping" defines
the necessary parameters to configure the transport defined in this
document using the generic "udp-client-grouping" grouping from the
"ietf-udp-client" module <xref target="I-D.ahuang-netconf-udp-client-server"/>
and the "tls-client-grouping" defined in the "ietf-tls-client" module
<xref target="I-D.ietf-netconf-tls-client-server"/>.</t>
<t><figure>
<artwork><![CDATA[
<CODE BEGINS> file "[email protected]"
module ietf-udp-notif-transport {
yang-version 1.1;
namespace
"urn:ietf:params:xml:ns:yang:ietf-udp-notif-transport";
prefix unt;
import ietf-subscribed-notifications {
prefix sn;
reference
"RFC 8639: Subscription to YANG Notifications";
}
import ietf-subscribed-notif-receivers {
prefix snr;
reference
"RFC YYYY: An HTTPS-based Transport for
Configured Subscriptions";
}
import ietf-udp-client {
prefix udpc;
reference
"RFC ZZZZ: YANG Grouping for UDP Clients and UDP Servers";
}
import ietf-tls-client {
prefix tlsc;
reference
"RFC TTTT: YANG Groupings for TLS Clients and TLS Servers";
}
import ietf-tls-common {
prefix tlscmn;
reference
"RFC TTTT: YANG Groupings for TLS Clients and TLS Servers";
}
organization "IETF NETCONF (Network Configuration) Working Group";
contact
"WG Web: <http:/tools.ietf.org/wg/netconf/>
WG List: <mailto:[email protected]>
Authors: Guangying Zheng
<mailto:[email protected]>
Tianran Zhou
<mailto:[email protected]>
Thomas Graf
<mailto:[email protected]>
Pierre Francois
<mailto:[email protected]>
Alex Huang Feng
<mailto:[email protected]>
Paolo Lucente
<mailto:[email protected]>";
description
"Defines a model for configuring UDP-Notif as a transport
for Configured Subscriptions.
Copyright (c) 2024 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 Revised BSD License set forth in Section
4.c of the IETF Trust's Legal Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC XXXX; see the RFC
itself for full legal notices.";
revision 2024-10-17 {
description
"Initial revision";
reference
"RFC XXXX: UDP-based Transport for Configured Subscriptions";
}
/*
* FEATURES
*/
feature encode-cbor {
description
"This feature indicates that CBOR encoding of notification
messages is supported.";
}
feature dtls13 {
description
"This feature indicates that DTLS 1.3 encryption of UDP
packets is supported.";
}
feature segmentation {
description
"This feature indicates segmentation of notification messages
is supported.";
}
/*
* IDENTITIES
*/
identity udp-notif {
base sn:transport;
base sn:configurable-encoding;
description
"UDP-Notif is used as transport for notification messages
and state change notifications.";
}
identity encode-cbor {
base sn:encoding;
description
"Encode data using CBOR as described in RFC 9254.";
reference
"RFC 9254: CBOR Encoding of Data Modeled with YANG";
}
grouping udp-notif-receiver-grouping {
description
"Provides a reusable description of a UDP-Notif target
receiver.";
uses udpc:udp-client-grouping {
refine remote-port {
mandatory true;
}
}
container dtls {
if-feature dtls13;
presence dtls;
uses tlsc:tls-client-grouping {
// Using tls-client-grouping without TLS1.2 parameters
// allowing only DTLS 1.3
refine "client-identity/auth-type/tls12-psk" {
// create the logical impossibility of enabling TLS1.2
if-feature "not tlsc:client-ident-tls12-psk";
}
refine "server-authentication/tls12-psks" {
// create the logical impossibility of enabling TLS1.2
if-feature "not tlsc:server-auth-tls12-psk";
}
refine "hello-params/tls-versions/min" {
must "not(derived-from-or-self(current(), "
+ "'tlscmn:tls12'))" {
error-message