NETCONF over QUIC

Introduction The Network Configuration Protocol (NETCONF) defines a mechanism through which the configuration of network devices can be installed, manipulated, and deleted. NETCONF can be conceptually partitioned into four layers: content, operation, message and security transport layers. The Secure Transport layer provides a communication path between the client and server. NETCONF can be layered over any transport protocol that provides a set of basic requirements, such as:

NETCONF is connection-oriented, requiring a persistent connection between peers. This connection MUST provide reliable and sequenced data delivery. NETCONF connections are long-lived, persisting between protocol operations.
NETCONF connections MUST provide authentication, data integrity, confidentiality, and replay protection. NETCONF depends on the transport protocol for this capability.

The NETCONF protocol is not bound to any particular transport protocol, but allows a mapping to define how it can be implemented over any specific protocol. However, because of the connection-oriented feature, almost all of the current secure transport protocols used by NETCONF are TCP based. As is well known, TCP has some shortcomings such as head-of-line blocking. QUIC () conforms to the above requirements, therefore is also an appropriate transport protocol for NETCONF. Moreover, QUIC provides the following additional benefits not present in the other NETCONF transports:

Single connection can be long lived and support multiple NETCONF RPC calls and responses within the same connection, using streams. This is very useful for a network management control station who is regularly monitoring devices and therefore having a long lived connection requires way less resources on both peers.
1 RTT initial handshake that includes TLS.
Adaptable to more difficult environments such as those with long delays (, .

Therefore, QUIC is a proper transport protocol for the secure transport layer of NETCONF. This document specifies how to use QUIC as the secure transport protocol for NETCONF.

Terminology and Definitions The key words "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 .

Connection Management

Connection establishment QUIC connections are established as described in . During connection establishment, support is indicated by selecting the ALPN token registered for NETCONF over QUIC (see ) in the cryptographic handshake.

Early data The QUIC protocol uses TLS 1.3 messages to secure the transport. This means that Early data (aka 0-RTT data) is supported. Early data (aka 0-RTT data) is a mechanism defined in TLS 1.3 that allows a client to send data ("early data") as part of the first flight of messages to a server. Note that TLS 1.3 can be used without early data as per Appendix F.5 of . In fact, early data is permitted by TLS 1.3 only when the client and server share a Pre-Shared Key (PSK), either obtained externally or via a previous handshake. The client uses the PSK to authenticate the server and to encrypt the early data. As noted in Section 2.3 of , the security properties for early data are weaker than those for subsequent TLS-protected data. In particular, early data is not forward secret, and there is no protection against the replay of early data between connections. Appendix E.5 of requires applications not use early data without a profile that defines its use. This document specifies that NETCONF over QUIC implementations MUST NOT use early data.

Connection Termination

QUIC Connection Termination Process The typical QUIC connection termination process is described in

Considerations for Connection Termination When a NETCONF session is implemented based on a QUIC connection, the idle timeout should be set appropriately in order to keep the QUIC connection persistent even if the NETCONF session is idle. In some cases, disabling it may be a possible option. When a NETCONF server receives a <close-session> request, it will gracefully close the NETCONF session. The server SHOULD close the associated QUIC connection. When a NETCONF entity receives a <kill-session> request for an open session, it SHOULD close the associated QUIC connection. When a NETCONF entity is detecting the interruption of the QUIC connection, it SHOULD send a <close-session> request to the peer NETCONF entity. When a stateless reset event occurs, nothing needs to be done by either the client or the server.

Stream mapping and usage The NETCONF protocol layers specified in are presented in Figure 1.

NETCONF Protocol Layers | | | | | | | +-------------+ +-----------------+ | | | | +-------------+ +-----------------+ +----------------+ (2) | Messages | | , | | | | | | | | | +-------------+ +-----------------+ +----------------+ | | | +-------------+ +-----------------------------------------+ (1) | Secure | | SSH, TLS, ... | | Transport | | | +-------------+ +-----------------------------------------+ ]]> shows that there are two kinds of main data flow exchanged between client and server:

Configuration data from client to server.
Notification data from server to client.

The two kinds of data flow need to be mapped into QUIC streams. QUIC Streams provide a lightweight, ordered byte-stream abstraction to an application. Streams can be unidirectional or bidirectional meanwhile streams can be initiated by either the client or the server. Unidirectional streams carry data in one direction: from the initiator of the stream to its peer. Bidirectional streams allow for data to be sent in both directions. QUIC uses Stream ID to identify the stream. The least significant bit (0x1) of the stream ID identifies the initiator of the stream. The second least significant bit (0x2) of the stream ID distinguishes between bidirectional streams (with the bit set to 0) and unidirectional streams. There are four types of streams which are described in . And Table 1 also describes the four types of streams Stream Acronym Types

Acronym	Stream Type
C-BD	Client-Initiated, Bidirectional
S-BD	Server-Initiated, Bidirectional
C-UN	Client-Initiated, Unidirectional
S-UN	Server-Initiated, Unidirectional

Bidirectional Stream Between client and server NETCONF protocol uses an RPC-based communication model. Configuration data from client to server is exchanged based on '<rpc>' (the client initiating) and '<rpc-reply>' (sent by the server) and so on. The messages used to exchange configuration data MUST be mapped into one bidirectional stream whose acronym is 'C-BD' according to Table 1. Since RPC processing is serialized and ordered within a session ( section 4.5), a bidirectional stream MUST be used for each NETCONF session.

Unidirectional Stream from server to client There are some notification data exchanged between the client and the server. Notification is an server initiated message indicating that a certain event has been recognized by the server. Notification messages are initiated by the server and no reply is needed from the client. So the messages used to exchange notification data MUST be mapped into one unidirectional stream whose acronym is 'S-UN' according to Table 1.

Mapping of QUIC connection, QUIC stream, and NETCONF session The relationship among NETCONF sessions, QUIC streams and QUIC connections is illustrted as follows.

One NETCONF session is allowed per QUIC connection.
The NETCONF sessions, except subscriptions, runs over a QUIC bidi-stream.
NETCONF Notifications and Subscribed Notifications runs over one QUIC uni-stream per subscription.

The notifications refer to messages corresonding to a subscription from server to client after the subscription process is over.

Call home considerations

protocol-layering perspective The following diagram illustrates call home from a protocol-layering perspective based on QUIC:

Call Home Sequence Diagram based on QUIC | | | | | | 2. NETCONF over QUIC | |<-----------------------------------| | | | | | 3. NETCONF/RESTCONF | |<-----------------------------------| | | Note: Arrows point from the "client" to the "server" at each protocol layer. ]]> This diagram makes the following points:

The NETCONF/RESTCONF server begins by initiating a QUIC connection to the NETCONF/RESTCONF client.
Using this QUIC connection, the NETCONF/RESTCONF client initiates a NETCONF/RESTCONF session to the NETCONF/RESTCONF server.

RFC8071 Call Home Specific Case In the case of Call home feature, where the NETCONF server initiates the transport connection to the NETCONF client, will be used as follows: - the Client, referred in the Table, means the QUIC initiating party, therefore the NETCONF server and - the Server means the QUIC receiving party, therefore the NETCONF client.

Endpoint Authentication Since QUIC uses TLS 1.3 this is used to verify server identity and client identity.

Server Identity A server's identity MUST be verified according to .

Client Identity A client's identity MUST be verified according to .

Framing In order to mitigate delimiter injection attacks chunked framing as defined in is required for NETCONF over QUIC. The <hello> message MUST be followed by the character sequence RFC 5539 assumes that the end-of-message (EOM) sequence, ]]>]]>>. Upon reception of the <hello> message, the receiving peer's QUIC layer conceptually passes the <hello> message to the Messages layer. If the :base:1.1 capability is advertised by both peers, the chunked framing mechanism defined in Section 4.2 of [] is used for the remainder of the NETCONF session. Otherwise, the old end-of-message-based mechanism (see Section 4.3 of []) is used.

Overview of YANG Module This document defines one YANG module that augments the NETCONF YANG groupings with the QUIC transport YANG groupings . This section presents an overview of the YANG Module.

The "netconf-client" augmentation The following tree diagram illustrates the augmentation of the QUIC client grouping into the NETCONF client container:

Comments:

This augmentation to the "ncc:transport" container in "ietf-netconf-client.yang" adds a "quic" case with a "quic" container which uses the "quicc:quic-client" grouping.
Note that the if-feature "quic-initiate" conditions if the "quic" container is available in the schema.

The "netconf-server" augmentation The following tree diagram illustrates the augmentation of the QUIC server grouping into the NETCONF server container:

Comments:

This augmentation to the "ncs:transport" container in "ietf-netconf-server.yang" adds a "quic" case with a "quic" container which uses the "quics:quic-server" grouping.
Note that the if-feature "quic-listen" conditions if the "quic" container is available in the schema.

YANG Module This YANG module has normative references to and . <CODE BEGINS> file "ietf-netconf-quic@YYYY-MM-DD.yang"

Error codes

Transport Error Codes Error codes of secure transport layer are specified in []. There are not new transport Error Codes defined for NETCONF over QUIC.

Application Error Codes According to [], management of application error codes is left to application protocols. and application error codes can be used by RESET_STREAM Frame and STOP_SENDING Frame. Application error codes for NETCONF over QUIC are listed as follows:

NO_NETCONF PROTOCOL ERROR (0x00): no NETCONF errors happens.
NETCONF CLOSE SESSION_ERROR (0x01): The peer tries to close a session which is not initiated by it.
NETCONF CLOSE STREAM ERROR (0x02): The peer tries to close a bidirectional stream when the NETCONF session is active.

Security Considerations The security considerations described throughout and apply here as well. This document requires verification of server identity and client identity according to . If invalid data or malformed messages are encountered, a robust implementation of this document MUST silently discard the message without further processing and then stop the NETCONF session.

IANA Considerations This document creates a new registration for the identification of NETCONF over QUIC in the "Application Layer Protocol Negotiation (ALPN) Protocol IDs registry established in . The "noq" string identifies NETCONF over QUIC:

Protocol: NETCONF over QUIC
Identification Sequence: 0x6e 0x6f 0x71 ("noq")
Specification: This document

This document also requests IANA to reserve a UDP port for 'NETCONF over QUIC':

Service Name: netconf-quic
Transport Protocol(s): UDP
Assignee: IESG iesg@ietf.org
Contact: IETF Chair chair@ietf.org
Description: NETCONF protocol over QUIC transport
Reference: RFC AAAA
Port number: 831
Assignment Notes: Port 831 is currently assigned to netconf-beep, but a de-assignment is requested in .

Service Name: netconf-ch-quic
Transport Protocol(s): UDP
Assignee: IESG iesg@ietf.org
Contact: IETF Chair chair@ietf.org
Description: NETCONF Call Home (QUIC)
Reference: RFC AAAA
Port number: 4335

Acknowledgements The authors would like to acknowledge the contributors Yang Kou, Xueshun Wang, Kent Watsen, Jeffrey Haas, Balázs Lengyel, Robert Wilton, Huaimo Chen, Lifen Zhou, Andy Bierman, Sean Turner, and Joe Clarke for their beneficial comments. The authors would like to acknowledge the very useful feedback from an early implementor: Adolfo Ochagavia.