NETCONF G. Zheng Internet-Draft T. Zhou Intended status: Standards Track Huawei Expires: April 6, 2021 T. Graf Swisscom P. Francois INSA-Lyon P. Lucente NTT October 3, 2020 UDP-based Transport for Configured Subscriptions draft-ietf-netconf-udp-notif-00 Abstract This document describes an UDP-based notification mechanism to collect data from networking devices. A shim header is proposed to facilitate the streaming of data directly from line cards to a collector. The objective is to rely on a lightweight approach to allow for higher frequency and better transit performance compared to already established notification mechanisms. Requirements Language 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 [RFC2119]. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on April 6, 2021. Zheng, et al. Expires April 6, 2021 [Page 1] Internet-Draft ietf-udp-notif October 2020 Copyright Notice Copyright (c) 2020 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Configured Subscription to UDP-Notif . . . . . . . . . . . . 4 3. UDP-Based Transport . . . . . . . . . . . . . . . . . . . . . 4 3.1. Design Overview . . . . . . . . . . . . . . . . . . . . . 4 3.2. Format of the UDP-Notif Message Header . . . . . . . . . 5 3.3. Options . . . . . . . . . . . . . . . . . . . . . . . . . 6 3.3.1. Fragmentation Option . . . . . . . . . . . . . . . . 6 3.4. Data Encoding . . . . . . . . . . . . . . . . . . . . . . 7 4. Congestion Control . . . . . . . . . . . . . . . . . . . . . 8 5. Applicability . . . . . . . . . . . . . . . . . . . . . . . . 8 6. A YANG Data Model for Management of UDP-Notif . . . . . . . . 8 7. YANG Module . . . . . . . . . . . . . . . . . . . . . . . . . 9 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 9. Security Considerations . . . . . . . . . . . . . . . . . . . 12 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 12 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 11.1. Normative References . . . . . . . . . . . . . . . . . . 12 11.2. Informative References . . . . . . . . . . . . . . . . . 14 11.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 14 1. Introduction Sub-Notif [RFC8639] defines a mechanism that lets a collector subscribe to the publication of YANG-defined data maintained in a YANG [RFC7950] datastore. The mechanism separates the management and control of subscriptions from the transport used to deliver the data. Three transport mechanisms, namely NETCONF transport [RFC8640], RESTCONF transport [RFC8650], and HTTPS transport [I-D.ietf-netconf-https-notif] have been defined so far for such notification messages. Zheng, et al. Expires April 6, 2021 [Page 2] Internet-Draft ietf-udp-notif October 2020 While powerful in its features and general in their architecture, the currently available transport mechanisms need to be complemented to support data publications at high velocity from devices that feature a distributed architecture. The currently available transports are based on TCP and lack the efficiency needed to continuously send notifications at high velocity. This document specifies a transport option for Sub-Notif that leverages UDP. Specifically, it facilitates the distributed data collection mechanism described in [I-D.unyte-netconf-distributed-notif]. In the case of data originating from multiple line cards, centralized designs require data to be internally forwarded from those line cards 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. What is needed is the support for a mechanism that allows for directly pushing multiple substreams, e.g. one from each line card, without passing them through an additional processing stage for internal consolidation. The proposed UDP-based transport allows for such a distributed data collection approach. o Firstly, a UDP approach reduces the burden of maintaining a large amount of active TCP connections at the collector, notably in cases where it collects data from the line cards of a large amount of networking devices. o Secondly, as no connection state needs to be maintained, UDP encapsulation can be easily implemented by the hardware of the publication streamer, which will further improve performance. o Ultimately, such advantages allow for a larger data analysis feature set, as more voluminous, finer grained data sets can be streamed to the collector. The transport described in this document can be used for transmitting notification messages over both IPv4 and IPv6. This document describes the notification mechanism. It is intended to be used in conjunction with [RFC8639], extended by [I-D.unyte-netconf-distributed-notif]. Section 2 describes the control of the proposed transport mechanism. Section 3 details the notification mechanism and message format. Section 4 discusses congestion control. Section 5 covers the applicability of the proposed mechanism. Zheng, et al. Expires April 6, 2021 [Page 3] Internet-Draft ietf-udp-notif October 2020 2. Configured Subscription to UDP-Notif This section describes how the proposed mechanism can be controlled using subscription channels based on NETCONF or RESTCONF. Following the usual approach of 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. Note that receivers MAY NOT be already up and running when the configuration of the subscription takes effect on the monitored device. 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 [RFC8639], MUST be encapsulated in separate notification messages. 3. UDP-Based Transport In this section, we specify the UDP-Notif Transport behaviour. Section 3.1 describes the general design of the solution. Section 3.2 specifies the UDP-Notif message format. Section 3.3 describes a generic optional sub TLV format. Section 3.3.1 uses such options to provide a fragmentation solution for large UDP-Notif message payloads. Section 3.4 describes the encoding of the message payload. 3.1. Design Overview As specified in Sub-Notif, the telemetry data is encapsulated in the NETCONF/RESTCONF notification message, which is then encapsulated and carried using transport protocols such as TLS or HTTP2. Figure 1 illustrates the the structure of an UDP-Notif message. o The Message Header contains information that facilitate the message transmission before deserializing the notification message. o Notification Message is the encoded content that the publication stream transports. The common encoding methods include GPB [1], CBOR [RFC7049], JSON, and XML. [I-D.ietf-netconf-notification-messages] describes the structure of the Notification Message for single notifications and bundled notifications. Zheng, et al. Expires April 6, 2021 [Page 4] Internet-Draft ietf-udp-notif October 2020 +-------+ +--------------+ +--------------+ | UDP | | Message | | Notification | | | | Header | | Message | +-------+ +--------------+ +--------------+ Figure 1: UDP-Notif Message Overview 3.2. Format of the UDP-Notif Message Header The UDP-Notif Message Header contains information that facilitate the message transmission before deserializing the notification message. The data format is shown in Figure 2. 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 +-------+-------+---------------+-------------------------------+ | Vers. | ET | Header Len | Message Length | +-------+-------+---------------+-------------------------------+ | Message-Generator-ID | +---------------------------------------------------------------+ | Message ID | +---------------------------------------------------------------+ ~ Options ~ +---------------------------------------------------------------+ Figure 2: UDP-Notif Message Header Format The Message Header contains the following field: o Version represents the PDU (Protocol Data Unit) encoding version. The initial version value is 0. o ET is a 4 bit identifier to indicate the encoding type used for the Notification Message. 16 types of encoding can be expressed: * 0: GPB; * 1: CBOR; * 2: JSON; * 3: XML; * others are reserved. o Header Length is the length of the message header in octets, including both the fixed header and the options. Zheng, et al. Expires April 6, 2021 [Page 5] Internet-Draft ietf-udp-notif October 2020 o Message Length is the total length of the message within one UDP datagram, measured in octets, including the message header. o Message-Generator-ID is a 32-bit identifier of the process which created the notification message. This allows disambiguation of an information source, such as the identification of different line cards sending the notification messages. The source IP address of the UDP datagrams SHOULD NOT be interpreted as the identifier for the host that originated the UDP-Notif message. Indeed, the streamer sending the UDP-Notif message could be a relay for the actual source of data carried within UDP-Notif messages. o The Message ID is generated continuously by the sender of UDP- Notif messages. Different subscribers share the same Message ID sequence. o 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 the following section. 3.3. Options All the options are defined with the following format, illustrated in Figure 3. 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 +---------------+---------------+-------------------------------- Figure 3: Generic Option Format o Type: 1 octet describing the option type; o Length: 1 octet of the TLV Length, including the Type and Length fields; o Variable-length data: 0 or more octets of TLV Value. 3.3.1. Fragmentation Option The UDP payload length is limited to 65535. Application level headers will make the actual payload shorter. Even though binary encodings such as GPB and CBOR may not require more space than what Zheng, et al. Expires April 6, 2021 [Page 6] Internet-Draft ietf-udp-notif October 2020 is left, more voluminous encodings such as JSON and XML may suffer from this size limitation. Although IPv4 and IPv6 senders can fragment outgoing packets exceeding their Maximum Transmission Unit(MTU), fragmented IP packets may not be desired for operational and performance reasons. Consequently, implementations of the mechanism SHOULD provide a configurable max-fragment-size option to control the maximum size of a payload. 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 | +-------------------------------+---------------+-------------+-+ | Fragment Number |L| +-------------------------------------------------------------+-+ Figure 4: Fragmentation Option Format The Fragmentation Option is to be included when the message content is fragmented into multiple pieces. Different fragments of one message share the same Message ID. An illustration is provided in Figure 4. The fields of this TLV are: o Type: indicates Fragmentation Option. The Type value is to be asigned. o Length: is a fixed value of 6 octets. o Fragment Number: indicates the sequence number of the current fragment. o L: is a flag to indicate whether the current fragment is the last one. When 0 is set, the current fragment is not the last one, hence more fragments are expected. When 1 is set, the current fragment is the last one. 3.4. Data Encoding UDP-Notif message data can be encoded in GPB, 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. Implementation MAY support multiple encoding methods per subscription. When bundled notifications are supported between the Zheng, et al. Expires April 6, 2021 [Page 7] Internet-Draft ietf-udp-notif October 2020 publisher and the receiver, only subscribed notifications with the same encoding can be bundled in a given message. 4. Congestion Control Congestion control mechanisms that respond to congestion by reducing traffic rates and establish a degree of fairness between flows that share the same path are vital to the stable operation of the Internet [RFC2914]. While efficient, UDP has no built-in congestion control mechanism. Because streaming telemetry can generate unlimited amounts of data, transferring this data over UDP may be considered problematic. 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. The UDP- Notif Message ID can be used to deduce congestion based on packet loss detection. Hence the collector can notify the device to use a lower streaming rate. The interaction to control the streaming rate on the device is out of the scope of this document. 5. Applicability The target application for UDP-Notif is the collection of data-plane information. The lack of reliability of the data streaming mechanism is thus considered acceptable as the mechanism is to be used in controlled environments, mitigating the risk of information loss, while allowing for publication of very large amounts of data. Moreover, in this context, sporadic events when incomplete data collection is provided is not critical for the proper management of the network. 6. A YANG Data Model for Management of UDP-Notif The YANG model defined in Section 9 has two leafs augmented into one place of Sub-Notif [RFC8639], plus one identity. module: ietf-udp-subscribed-notifications augment /sn:subscriptions/sn:subscription/sn:receivers/sn:receiver: +--rw address inet:ip-address +--rw port inet:port-number +--rw enable-fragment? boolean +--rw max-fragment-size? uint32 Zheng, et al. Expires April 6, 2021 [Page 8] Internet-Draft ietf-udp-notif October 2020 7. YANG Module file "ietf-udp-notif@2020-04-27.yang" module ietf-udp-notif { yang-version 1.1; namespace "urn:ietf:params:xml:ns:yang:ietf-udp-notif"; prefix un; import ietf-subscribed-notifications { prefix sn; reference "RFC 8639: Subscription to YANG Notifications"; } import ietf-inet-types { prefix inet; reference "RFC 6991: Common YANG Data Types"; } organization "IETF NETCONF (Network Configuration) Working Group"; contact "WG Web: WG List: Authors: Guangying Zheng Tianran Zhou Thomas Graf Pierre Francois Paolo Lucente "; description "Defines UDP-Notif as a supported transport for subscribed event notifications. Copyright (c) 2018 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 Simplified 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). Zheng, et al. Expires April 6, 2021 [Page 9] Internet-Draft ietf-udp-notif October 2020 This version of this YANG module is part of RFC XXXX; see the RFC itself for full legal notices."; revision 2020-04-27 { description "Initial version"; reference "RFC XXXX: UDP-based Notifications for Streaming Telemetry"; } identity udp-notif { base sn:transport; 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 7049."; reference "RFC 7049: Concise Binary Object Representation"; } identity encode-gpb { base sn:encoding; description "Encode data using GPB."; } grouping target-receiver { description "Provides a reusable description of a UDP-Notif target receiver."; leaf address { type inet:ip-address; mandatory true; description "IP address of target UDP-Notif receiver, which can be an IPv4 address or an IPV6 address."; } leaf port { type inet:port-number; mandatory true; description "Port number of target UDP-Notif receiver, if not specified, the system should use default port number."; Zheng, et al. Expires April 6, 2021 [Page 10] Internet-Draft ietf-udp-notif October 2020 } leaf enable-fragment { type boolean; default false; description "The switch for the fragment feature. When disabled, the publisher will not allow fragment for a very large data"; } leaf max-fragment-size { when "../enable-fragment = true"; type uint32; description "UDP-Notif provides a configurable max-fragment-size to control the size of each message."; } } augment "/sn:subscriptions/sn:subscription/sn:receivers/sn:receiver" { description "This augmentation allows UDP-Notif specific parameters to be exposed for a subscription."; uses target-receiver; } } 8. IANA Considerations This RFC requests that IANA assigns one UDP port number in the "Registered Port Numbers" range with the service name "udp-notif". This port will be the default port for the UDP-based notification Streaming Telemetry (UDP-Notif) for NETCONF and RESTCONF. Below is the registration template following the rules of [RFC6335]. Service Name: udp-notif Transport Protocol(s): UDP Assignee: IESG Contact: IETF Chair Description: UDP-based Publication Streaming Telemetry Reference: RFC XXXX Port Number: PORT-X Zheng, et al. Expires April 6, 2021 [Page 11] Internet-Draft ietf-udp-notif October 2020 IANA is requested to assign a new URI from the IETF XML Registry [RFC3688]. The following URI is suggested: URI: urn:ietf:params:xml:ns:yang:ietf-udp-notif Registrant Contact: The IESG. XML: N/A; the requested URI is an XML namespace. This document also requests a new YANG module name in the YANG Module Names registry [RFC7950] with the following suggestion: name: ietf-udp-notif namespace: urn:ietf:params:xml:ns:yang:ietf-udp-notif prefix: un reference: RFC XXXX 9. Security Considerations TBD 10. Acknowledgements The authors of this documents would like to thank Alexander Clemm, Eric Voit, Huiyang Yang, Kent Watsen, Mahesh Jethanandani, Stephane Frenot, Timothy Carey, Tim Jenkins, and Yunan Gu for their constructive suggestions for improving this document. 11. References 11.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC2914] Floyd, S., "Congestion Control Principles", BCP 41, RFC 2914, DOI 10.17487/RFC2914, September 2000, . [RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, DOI 10.17487/RFC3688, January 2004, . [RFC4347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer Security", RFC 4347, DOI 10.17487/RFC4347, April 2006, . Zheng, et al. Expires April 6, 2021 [Page 12] Internet-Draft ietf-udp-notif October 2020 [RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", STD 68, RFC 5234, DOI 10.17487/RFC5234, January 2008, . [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS) Protocol Version 1.2", RFC 5246, DOI 10.17487/RFC5246, August 2008, . [RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed., and A. Bierman, Ed., "Network Configuration Protocol (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011, . [RFC6335] Cotton, M., Eggert, L., Touch, J., Westerlund, M., and S. Cheshire, "Internet Assigned Numbers Authority (IANA) Procedures for the Management of the Service Name and Transport Protocol Port Number Registry", BCP 165, RFC 6335, DOI 10.17487/RFC6335, August 2011, . [RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347, January 2012, . [RFC7049] Bormann, C. and P. Hoffman, "Concise Binary Object Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049, October 2013, . [RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language", RFC 7950, DOI 10.17487/RFC7950, August 2016, . [RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017, . [RFC8639] Voit, E., Clemm, A., Gonzalez Prieto, A., Nilsen-Nygaard, E., and A. Tripathy, "Subscription to YANG Notifications", RFC 8639, DOI 10.17487/RFC8639, September 2019, . [RFC8640] Voit, E., Clemm, A., Gonzalez Prieto, A., Nilsen-Nygaard, E., and A. Tripathy, "Dynamic Subscription to YANG Events and Datastores over NETCONF", RFC 8640, DOI 10.17487/RFC8640, September 2019, . Zheng, et al. Expires April 6, 2021 [Page 13] Internet-Draft ietf-udp-notif October 2020 [RFC8650] Voit, E., Rahman, R., Nilsen-Nygaard, E., Clemm, A., and A. Bierman, "Dynamic Subscription to YANG Events and Datastores over RESTCONF", RFC 8650, DOI 10.17487/RFC8650, November 2019, . 11.2. Informative References [I-D.ietf-netconf-https-notif] Jethanandani, M. and K. Watsen, "An HTTPS-based Transport for Configured Subscriptions", draft-ietf-netconf-https- notif-04 (work in progress), July 2020. [I-D.ietf-netconf-notification-messages] Voit, E., Jenkins, T., Birkholz, H., Bierman, A., and A. Clemm, "Notification Message Headers and Bundles", draft- ietf-netconf-notification-messages-08 (work in progress), November 2019. [I-D.unyte-netconf-distributed-notif] Zhou, T., Zheng, G., Voit, E., Graf, T., and P. Francois, "Subscription to Distributed Notifications", draft-unyte- netconf-distributed-notif-00 (work in progress), June 2020. 11.3. URIs [1] https://developers.google.com/protocol-buffers/ Authors' Addresses Guangying Zheng Huawei 101 Yu-Hua-Tai Software Road Nanjing, Jiangsu China Email: zhengguangying@huawei.com Tianran Zhou Huawei 156 Beiqing Rd., Haidian District Beijing China Email: zhoutianran@huawei.com Zheng, et al. Expires April 6, 2021 [Page 14] Internet-Draft ietf-udp-notif October 2020 Thomas Graf Swisscom Binzring 17 Zuerich 8045 Switzerland Email: thomas.graf@swisscom.com Pierre Francois INSA-Lyon Lyon France Email: pierre.francois@insa-lyon.fr Paolo Lucente NTT Siriusdreef 70-72 Hoofddorp, WT 2132 NL Email: paolo@ntt.net Zheng, et al. Expires April 6, 2021 [Page 15]