NETCONF E. Voit Internet-Draft E. Nilsen-Nygaard Intended status: Standards Track Cisco Systems Expires: November 19, 2018 A. Clemm Huawei A. Bierman YumaWorks May 18, 2018 RESTCONF and HTTP Transport for Event Notifications draft-ietf-netconf-restconf-notif-05 Abstract This document defines RESTCONF, HTTP2, and HTTP1.1 bindings for the transport of subscription requests and corresponding push updates. Being subscribed may be either publisher defined event streams or nodes/subtrees of YANG Datastores. 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 November 19, 2018. Copyright Notice Copyright (c) 2018 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 Voit, et al. Expires November 19, 2018 [Page 1] Internet-Draft RESTCONF-Notif May 2018 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 . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Dynamic Subscription . . . . . . . . . . . . . . . . . . . . 3 3.1. Transport Connectivity . . . . . . . . . . . . . . . . . 4 3.2. Discovery . . . . . . . . . . . . . . . . . . . . . . . . 4 3.3. RESTCONF RPCs and HTTP Status Codes . . . . . . . . . . . 4 3.4. Call Flow for HTTP2 . . . . . . . . . . . . . . . . . . . 6 3.5. Call flow for HTTP1.1 . . . . . . . . . . . . . . . . . . 8 4. Configured Subscription . . . . . . . . . . . . . . . . . . . 10 4.1. Transport Connectivity . . . . . . . . . . . . . . . . . 10 4.2. Call Flow . . . . . . . . . . . . . . . . . . . . . . . . 11 5. QoS Treatment . . . . . . . . . . . . . . . . . . . . . . . . 12 6. Mandatory JSON and datastore support . . . . . . . . . . . . 12 7. Notification Messages . . . . . . . . . . . . . . . . . . . . 12 8. YANG Tree . . . . . . . . . . . . . . . . . . . . . . . . . . 12 9. YANG module . . . . . . . . . . . . . . . . . . . . . . . . . 13 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15 11. Security Considerations . . . . . . . . . . . . . . . . . . . 16 12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 17 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 17 13.1. Normative References . . . . . . . . . . . . . . . . . . 17 13.2. Informative References . . . . . . . . . . . . . . . . . 19 Appendix A. RESTCONF over GRPC . . . . . . . . . . . . . . . . . 19 Appendix B. Examples . . . . . . . . . . . . . . . . . . . . . . 19 B.1. Dynamic Subscriptions . . . . . . . . . . . . . . . . . . 20 B.1.1. Establishing Dynamic Subscriptions . . . . . . . . . 20 B.1.2. Modifying Dynamic Subscriptions . . . . . . . . . . . 22 B.1.3. Deleting Dynamic Subscriptions . . . . . . . . . . . 24 B.2. Configured Subscriptions . . . . . . . . . . . . . . . . 25 B.2.1. Creating Configured Subscriptions . . . . . . . . . . 25 B.2.2. Modifying Configured Subscriptions . . . . . . . . . 28 B.2.3. Deleting Configured Subscriptions . . . . . . . . . . 30 B.3. Subscription State Notifications . . . . . . . . . . . . 31 B.3.1. subscription-started and subscription-modified . . . 31 B.3.2. subscription-completed, subscription-resumed, and replay-complete . . . . . . . . . . . . . . . . . . . 32 B.3.3. subscription-terminated and subscription-suspended . 32 Appendix C. Changes between revisions . . . . . . . . . . . . . 33 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 34 Voit, et al. Expires November 19, 2018 [Page 2] Internet-Draft RESTCONF-Notif May 2018 1. Introduction Mechanisms to support event subscription and push are defined in [I-D.draft-ietf-netconf-subscribed-notifications]. Enhancements to [I-D.draft-ietf-netconf-subscribed-notifications] which enable YANG datastore subscription and push are defined in [I-D.ietf-netconf-yang-push]. This document provides a transport specification for these protocols over RESTCONF [RFC8040] and HTTP. Driving these requirements is [RFC7923]. The streaming of notifications encapsulating the resulting information push can be done with either HTTP1.1 [RFC7231] or HTTP2 [RFC7540]. 2. Terminology 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]. The following terms use the definitions from [I-D.draft-ietf-netconf-subscribed-notifications]: configured subscription, dynamic subscription, event stream, notification message, publisher, receiver, subscriber, and subscription. Other terms reused include datastore, which is defined in [RFC8342], and HTTP2 stream which maps to the definition of "stream" within [RFC7540], Section 2. [ note to the RFC Editor - please replace XXXX within this document with the number of this document ] 3. Dynamic Subscription This section provides specifics on how to establish and maintain dynamic subscriptions over HTTP 1.1 and HTTP2 via signaling messages transported over RESTCONF [RFC8040]. Subscribing to event streams is accomplished in this way via a RESTCONF POST into RPCs defined within [I-D.draft-ietf-netconf-subscribed-notifications] Section 2.4. YANG datastore subscription is accomplished via augmentations to [I-D.draft-ietf-netconf-subscribed-notifications] as described within [I-D.ietf-netconf-yang-push] Section 4.4. Common across all HTTP based dynamic subscriptions is that a POST needs to be made against a specific URI on the Publisher. Subscribers cannot pre-determine the URI against which a subscription might exist on a publisher, as the URI will only exist after the "establish-subscription" has been accepted. There subscription URI Voit, et al. Expires November 19, 2018 [Page 3] Internet-Draft RESTCONF-Notif May 2018 will be determined and sent as part of the response to the "establish-subscription", and a subsequent POST to this URI will be done in order to start the flow of notification messages back to the subscriber. A subscription does not become ACTIVE as per Section 2.4.1. of [I-D.draft-ietf-netconf-subscribed-notifications] until the POST is received. 3.1. Transport Connectivity For a dynamic subscription, where an HTTP client session doesn't already exist, a new client session is initiated from the subscriber. If the subscriber is unsure if HTTP2 is supported by the publisher, HTTP1.1 will be used for initial messages, and these messages will include an HTTP version upgrade request as per [RFC7230], Section 6.7. If a publisher response indicates that HTTP2 is supported, HTTP2 will be used between subscriber and publisher for future HTTP interactions as per [RFC7540]. A subscriber SHOULD establish the HTTP session over TLS [RFC5246] in order to secure the content in transit. Without the involvement of additional protocols, neither HTTP1.1 nor HTTP2 sessions by themselves allow for a quick recognition of when the communication path has been lost with the publisher. Where quick recognition of the loss of a publisher is required, a subscriber SHOULD connect over TLS [RFC5246], and use a TLS heartbeat [RFC6520] to track HTTP session continuity. In the case where a TLS heartbeat is included, it should be sent just from receiver to publisher. Loss of the heartbeat MUST result in any subscription related TCP sessions between those endpoints being torn down. A subscriber can then attempt to re-establish. 3.2. Discovery Subscribers can learn what event streams a RESTCONF server supports by querying the "streams" container of ietf-subscribed- notification.yang. Subscribers can learn what datastores a RESTCONF server supports by following [I-D.draft-ietf-netconf-nmda-restconf]. 3.3. RESTCONF RPCs and HTTP Status Codes Specific HTTP responses codes as defined in [RFC7231] section 6 will indicate the result of RESTCONF RPC requests with publisher. An HTTP status code of 200 is the proper response to any successful RPC defined within [I-D.draft-ietf-netconf-subscribed-notifications] or [I-D.ietf-netconf-yang-push]. Voit, et al. Expires November 19, 2018 [Page 4] Internet-Draft RESTCONF-Notif May 2018 If a publisher fails to serve the RPC request for one of the reasons indicated in [I-D.draft-ietf-netconf-subscribed-notifications] Section 2.4.6 or [I-D.ietf-netconf-yang-push] Appendix A, this will be indicated by "406" status code transported in the HTTP response. When a "406" status code is returned, the RPC reply MUST include an "rpc-error" element per [RFC8040] Section 7.1 with the following parameter values: o an "error-type" node of "application". o an "error-tag" node of "operation-failed". o an "error-app-tag" node with the value being a string that corresponds to an identity associated with the error, as defined in [I-D.draft-ietf-netconf-subscribed-notifications] section 2.4.6 for general subscriptions, and [I-D.ietf-netconf-yang-push] Appendix A.1, for datastore subscriptions. The tag to use depends on the RPC for which the error occurred. Viable errors for different RPCs are as follows: RPC select an identity with a base ---------------------- ------------------------------ establish-subscription establish-subscription-error modify-subscription modify-subscription-error delete-subscription delete-subscription-error kill-subscription kill-subscription-error resynch-subscription resynch-subscription-error Each error identity will be inserted as the "error-app-tag" using JSON encoding following the form :. An example of such as valid encoding would be "ietf-subscribed- notifications:no-such-subscription". o In case of error responses to an "establish-subscription" or "modify-subscription" request there is the option of including an "error-info" node. This node may contain hints for parameter settings that might lead to successful RPC requests in the future. Following are the yang-data structures which may be returned: Voit, et al. Expires November 19, 2018 [Page 5] Internet-Draft RESTCONF-Notif May 2018 establish-subscription returns hints in yang-data structure ---------------------- ------------------------------------ target: event stream establish-subscription-stream-error-info target: datastore establish-subscription-datastore-error-info modify-subscription returns hints in yang-data structure ---------------------- ------------------------------------ target: event stream modify-subscription-stream-error-info target: datastore modify-subscription-datastore-error-info The yang-data included within "error-info" SHOULD NOT include the optional leaf "error-reason", as such a leaf would be redundant with information that is already placed within the "error-app-tag". In case of an rpc error as a result of a "delete-subscription", a "kill-subscription", or a "resynch-subscription" request, no "error-info" needs to be included, as the "subscription-id" is the only RPC input parameter and no hints regarding this RPC input parameters need to be provided. Note that "error-path" does not need to be included with the "rpc- error" element, as subscription errors are generally not associated with nodes in the datastore but with the choice of RPC input parameters. 3.4. Call Flow for HTTP2 Requests to [I-D.draft-ietf-netconf-subscribed-notifications] or [I-D.ietf-netconf-yang-push] augmented RPCs are sent on one or more HTTP2 streams indicated by (a) in Figure 1. A successful "establish- subscription" will result in an RPC response returned with both a subscription identifier which uniquely identifies a subscription, as well as a URI which uniquely identifies the location of subscription on the publisher. This URI is defined via the "uri" leaf the Data Model in Section 9. An HTTP POST is then sent on a logically separate HTTP2 stream (b) to the URI on the publisher. This initiates to initiate the flow of notification messages which are sent in HTTP Data frames as a response to the POST. In the case below, a newly established subscription has its associated notification messages pushed over HTTP2 stream (7). These notification messages are placed into a HTTP2 Data frame (see [RFC7540] Section 6.1). Voit, et al. Expires November 19, 2018 [Page 6] Internet-Draft RESTCONF-Notif May 2018 +------------+ +------------+ | Subscriber | | Publisher | |HTTP2 Stream| |HTTP2 Stream| | (a) (b) | | (a) (b) | +------------+ +------------+ | RESTCONF POST (RPC:establish-subscription) | |--------------------------------------------->| | HTTP 200 OK (ID,URI)| |<---------------------------------------------| | (7)HTTP POST (URI) (7) | |--------------------------------------------->| | | HTTP 200 OK| | |<---------------------------------------------| | | HTTP Data (notif-message)| | |<---------------------------------------------| | RESTCONF POST (RPC:modify-subscription) | | |--------------------------------------------->| | | | HTTP 200 OK| | |<---------------------------------------------| | | | HTTP Data (subscription-modified)| | |<------------------------------------------(c)| | | HTTP Data (notif-message)| | |<---------------------------------------------| | RESTCONF POST (RPC:delete-subscription) | | |--------------------------------------------->| | | | HTTP 200 OK| | |<---------------------------------------------| | | | HTTP Headers (end of stream)| | (/7)<-----------------------------------------(/7) | Figure 1: Dynamic with HTTP2 Additional requirements for dynamic subscriptions over HTTP2 include: o A unique HTTP2 stream MAY be used for each subscription. o A single HTTP2 stream MUST NOT be used for subscriptions with different DSCP values. o All subscription state notifications from a publisher MUST be returned in a separate HTTP Data frame within the HTTP2 stream used by the subscription to which the state change refers. o In addition to an RPC response for a "modify-subscription" RPC traveling over (a), a "subscription-modified" state change notification must be sent within HTTP2 stream (b). This allows the receiver to know exactly when the new terms of the Voit, et al. Expires November 19, 2018 [Page 7] Internet-Draft RESTCONF-Notif May 2018 subscription have been applied to the notification messages. See arrow (c). o Additional RPCs for a particular subscription MUST NOT use the HTTP2 stream currently providing notification messages subscriptions. o An HTTP end of stream message MUST not be sent until all subscriptions using that HTTP2 stream have completed. 3.5. Call flow for HTTP1.1 The call flow is defined in Figure 2. Requests to [I-D.draft-ietf-netconf-subscribed-notifications] or [I-D.ietf-netconf-yang-push] augmented RPCs are sent on a TCP connection indicated by (a). A successful "establish-subscription" will result in an RPC response returned with both a subscription identifier which uniquely identifies a subscription, as well as a URI which uniquely identifies the location of subscription on the publisher (b). This URI is defined via the "uri" leaf the Data Model in Section 9. An HTTP POST is then sent on a logically separate TCP connection (b) to the URI on the publisher. This initiates to initiate the flow of notification messages which are sent in SSE [W3C-20150203] as a response to the POST. Voit, et al. Expires November 19, 2018 [Page 8] Internet-Draft RESTCONF-Notif May 2018 +--------------+ +--------------+ | Subscriber | | Publisher | |TCP connection| |TCP connection| | (a) (b) | | (a) (b) | +--------------+ +--------------+ | RESTCONF POST (RPC:establish-subscription) | |--------------------------------------------->| | HTTP 200 OK (ID,URI)| |<---------------------------------------------| | |HTTP GET (URI) | | |--------------------------------------------->| | | HTTP 200 OK| | |<---------------------------------------------| | | SSE (notif-message)| | |<---------------------------------------------| | RESTCONF POST (RPC:modify-subscription) | | |--------------------------------------------->| | | | HTTP 200 OK| | |<---------------------------------------------| | | | SSE (subscription-modified)| | |<------------------------------------------(c)| | | SSE (notif-message)| | |<---------------------------------------------| | RESTCONF POST (RPC:delete-subscription) | | |--------------------------------------------->| | | | HTTP 200 OK| | |<---------------------------------------------| | | | | | | Figure 2: Dynamic with HTTP1.1 Additional requirements for dynamic subscriptions over HTTP1.1 include: o All subscription state notifications from a publisher MUST be returned in a separate SSE message used by the subscription to which the state change refers. o Subscription RPCs MUST NOT use the TCP connection currently providing notification messages for that subscription. o In addition to an RPC response for a "modify-subscription" RPC traveling over (a), a "subscription-modified" state change notification must be sent within stream (b). This allows the receiver to know exactly when the new terms of the subscription have been applied to the notification messages. See arrow (c). Voit, et al. Expires November 19, 2018 [Page 9] Internet-Draft RESTCONF-Notif May 2018 Open question, should we just eliminate this possibility of HTTP1.1 for subscriptions? It would make the design simpler. 4. Configured Subscription With a configured subscription, all information needed to establish a secure relationship with that receiver is available on the publisher. With this information, the publisher will establish a secure transport connection with the receiver and then begin pushing notification messages to the receiver. Since RESTCONF might not exist on the receiver, it is not desirable to require that subscribed content be pushed with any dependency on RESTCONF. Therefore in place of RESTCONF, an HTTP2 Client connection must be established with an HTTP2 Server located on the receiver. Notification messages will then be sent as part of an extended HTTP POST to the receiver. 4.1. Transport Connectivity Configured subscriptions MUST only be connected over HTTP2 via a client session initiated from the publisher. Following are the conditions which MUST be met before estabishing a new HTTP2 connection with a receiver: o a configured subscription has a receiver in the CONNECTING state as described in [I-D.draft-ietf-netconf-subscribed-notifications], section 2.5.1., o the transport configured for that subscription is HTTP2, o there are state change notifications or notification messages pending for that receiver, and o no HTTP2 transport session exists to that receiver, If the above conditions are met, then the publisher MUST initiate a transport session via RESTCONF call home [RFC8071], section 4.1 to that receiver. HTTP2 only communications must be used as per [RFC7540], Section 3.3 when the HTTP session over TLS [RFC5246]. and [RFC7540], Section 3.4 when transporting cleartext over TCP. Note that a subscriber SHOULD establish over TLS in order to secure the content in transit. If the RESTCONF call home fails because the publisher receives receiver credentials which are subsequently declined per [RFC8071], Section 4.1, step S5 authentication, then that receiver MUST be placed into the TIMEOUT state. Voit, et al. Expires November 19, 2018 [Page 10] Internet-Draft RESTCONF-Notif May 2018 If the call home fails to establish for any other reason, the publisher MUST NOT progress the receiver to the ACTIVE state. Additionally, the publisher SHOULD place the receiver into the TIMEOUT state after a predetermined number of either failed call home attempts or remote transport session termination by the receiver. 4.2. Call Flow With HTTP2 connectivity established, a POST of each new "subscription-started" state change notification messages will be addressed to HTTP augmentation code on the receiver capable of accepting and acknowleding to subscription state change notifications. Until the "HTTP 200 OK" at point (c) of Figure 3 for each the "subscription-started" state change notification, a publisher MUST NOT progress the receiver to the ACTIVE state. In other words, is at point (c) which indicates that the receiver is ready for the delivery of subscribed content. At this point a notification-messages including subscribed content may be placed onto an HTTP2 stream for that subscription. +------------+ +------------+ | Receiver | | Publisher | |HTTP2 Stream| |HTTP2 Stream| | (a) (b) | | (a) (b) | +------------+ +------------+ |HTTP Post Headers, Data (subscription-started)| |<---------------------------------------------| | HTTP 200 OK | |-------------------------------------------->(c) | | HTTP Post Headers, Data (notif-message)| | |<---------------------------------------------| | | HTTP Data (notif-message)| | |<---------------------------------------------| | | HTTP Data (sub-terminated)| | |<---------------------------------------------| | |HTTP 200 OK | | |--------------------------------------------->| Figure 3: Configured over HTTP2 Additional requirements for configured subscriptions over HTTP2 include: o A unique HTTP2 stream MAY be used for each subscription. o A single HTTP2 stream MUST NOT be used for subscriptions with different DSCP values. Voit, et al. Expires November 19, 2018 [Page 11] Internet-Draft RESTCONF-Notif May 2018 o All subscription state notifications from a publisher MUST be returned in a separate HTTP Data frame within the HTTP2 stream used by the subscription to which the state change refers. o An HTTP end of stream message MUST not be sent until all subscriptions using that HTTP2 stream have completed. 5. QoS Treatment To meet subscription quality of service promises, the publisher MUST take any existing subscription "dscp" and apply it to the DSCP marking in the IP header. In addition, where HTTP2 transport is available to a notification message queued for transport to a receiver, the publisher MUST: o take any existing subscription "priority" and copy it into the HTTP2 stream priority, and o take any existing subscription "dependency" and map the HTTP2 stream for the parent subscription into the HTTP2 stream dependency. 6. Mandatory JSON and datastore support A publisher supporting [I-D.ietf-netconf-yang-push] MUST support the "operational" datastore as defined by [RFC8342]. The "encode-json" feature of [I-D.draft-ietf-netconf-subscribed-notifications] is mandatory to support. This indicates that JSON is a valid encoding for RPCs, state change notifications, and subscribed content. 7. Notification Messages Notification messages transported over HTTP will be encoded using one-way operation schema defined within [RFC5277], section 4. 8. YANG Tree The YANG model defined in Section 9 has one leaf augmented into four places of [I-D.draft-ietf-netconf-subscribed-notifications], plus two identities. As the resulting full tree is large, it will only be inserted at later stages of this document. Voit, et al. Expires November 19, 2018 [Page 12] Internet-Draft RESTCONF-Notif May 2018 9. YANG module This module references [I-D.draft-ietf-netconf-subscribed-notifications]. file "ietf-http-subscribed-notifications@2018-05-01.yang" module ietf-http-subscribed-notifications { yang-version 1.1; namespace "urn:ietf:params:xml:ns:yang:ietf-http-subscribed-notifications"; prefix hsn; import ietf-subscribed-notifications { prefix sn; } import ietf-yang-types { prefix yang; } organization "IETF NETCONF (Network Configuration) Working Group"; contact "WG Web: WG List: Editor: Eric Voit Editor: Alexander Clemm Editor: Einar Nilsen-Nygaard "; description "Defines HTTP variants as a supported transports 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). This version of this YANG module is part of RFC XXXX; see the RFC Voit, et al. Expires November 19, 2018 [Page 13] Internet-Draft RESTCONF-Notif May 2018 itself for full legal notices."; revision 2018-05-01 { description "Initial version"; reference "RFC XXXX: RESTCONF and HTTP Transport for Event Notifications"; } identity http2 { base sn:transport; base sn:inline-address; base sn:configurable-encoding; description "HTTP2 is used a transport for notification messages and state change notifications."; } identity http1.1 { base sn:transport; base sn:inline-address; base sn:configurable-encoding; description "HTTP1.1 is used a transport for notification messages and state change notifications."; } grouping uri { description "Provides a reusable description of a URI."; leaf uri { config false; type yang:uri; description "Location of a subscription specific URI on the publisher."; } } augment "/sn:establish-subscription/sn:output" { description "This augmentation allows HTTP specific parameters for a response to a publisher's subscription request."; uses uri; } augment "/sn:subscriptions/sn:subscription/sn:target" { description "This augmentation allows HTTP specific parameters to be Voit, et al. Expires November 19, 2018 [Page 14] Internet-Draft RESTCONF-Notif May 2018 exposed for a subscription."; uses uri; } augment "/sn:subscription-started/sn:target" { description "This augmentation allows HTTP specific parameters to be included part of the notification that a subscription has started."; uses uri; } augment "/sn:subscription-modified/sn:target" { description "This augmentation allows HTTP specific parameters to be included part of the notification that a subscription has been modified."; uses uri; } /* need to add a constraint that HTTP1.1 not allowed for configured subscriptions - needs the right syntax below... augment "sn:subscriptions/sn:subscription/sn:protocol" { when '../sn:configured-subscription-state' must ' protocol <> "http1.1"' { error-message "HTTP1.1 not used for configured subscriptions"; } } */ } 10. IANA Considerations This document registers the following namespace URI in the "IETF XML Registry" [RFC3688]: URI: urn:ietf:params:xml:ns:yang:ietf-http-subscribed-notifications Registrant Contact: The IESG. XML: N/A; the requested URI is an XML namespace. This document registers the following YANG module in the "YANG Module Names" registry [RFC6020]: Name: ietf-http-subscribed-notifications Voit, et al. Expires November 19, 2018 [Page 15] Internet-Draft RESTCONF-Notif May 2018 Namespace: urn:ietf:params:xml:ns:yang:ietf-http-subscribed- notifications Prefix: hsn Reference: RFC XXXX: RESTCONF and HTTP Transport for Event Notifications 11. Security Considerations The YANG module specified in this document defines a schema for data that is designed to be accessed via network management transports such as NETCONF [RFC6241] or RESTCONF [RFC8040]. The lowest NETCONF layer is the secure transport layer, and the mandatory-to-implement secure transport is Secure Shell (SSH) [RFC6242]. The lowest RESTCONF layer is HTTPS, and the mandatory-to-implement secure transport is TLS [RFC5246]. The one new data node introduced 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 this data nodes. These are the subtrees and data nodes and their sensitivity/vulnerability: Container: "/subscriptions" o "uri": leaf will show where subscribed resources might be located on a publisher. Access control must be set so that only someone with proper access permissions, and perhaps even HTTP session has the ability to access this resource. One or more publishers of configured subscriptions could be used to overwhelm a receiver which doesn't even support subscriptions. There are two protections needing support on a publisher. First, notification messages for configured subscriptions MUST only be transmittable over encrypted transports. Clients which do not want pushed content need only terminate or refuse any transport sessions from the publisher. Second, the HTTP transport augmentation on the receiver must send an HTTP 200 OK to a subscription started notification before the publisher starts streaming any subscribed content. One or more publishers could overwhelm a receiver which is unable to control or handle the volume of Event Notifications received. In deployments where this might be a concern, HTTP2 transport such as HTTP2) should be selected. The NETCONF Authorization Control Model [RFC6536] SHOULD be used to control and restrict authorization of subscription configuration. Voit, et al. Expires November 19, 2018 [Page 16] Internet-Draft RESTCONF-Notif May 2018 12. Acknowledgments We wish to acknowledge the helpful contributions, comments, and suggestions that were received from: Ambika Prasad Tripathy, Alberto Gonzalez Prieto, Susan Hares, Tim Jenkins, Balazs Lengyel, Kent Watsen, Michael Scharf, and Guangying Zheng. 13. References 13.1. Normative References [GRPC] "RPC framework that runs over HTTP2", August 2017, . [I-D.draft-ietf-netconf-subscribed-notifications] Voit, E., Clemm, A., Gonzalez Prieto, A., Tripathy, A., and E. Nilsen-Nygaard, "Custom Subscription to Event Streams", draft-ietf-netconf-subscribed-notifications-13 (work in progress), April 2018. [I-D.ietf-netconf-yang-push] Clemm, A., Voit, E., Gonzalez Prieto, A., Prasad Tripathy, A., Nilsen-Nygaard, E., Bierman, A., and B. Lengyel, "Subscribing to YANG datastore push updates", March 2017, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, DOI 10.17487/RFC3688, January 2004, . [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS) Protocol Version 1.2", RFC 5246, DOI 10.17487/RFC5246, August 2008, . [RFC5277] Chisholm, S. and H. Trevino, "NETCONF Event Notifications", RFC 5277, DOI 10.17487/RFC5277, July 2008, . Voit, et al. Expires November 19, 2018 [Page 17] Internet-Draft RESTCONF-Notif May 2018 [RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for the Network Configuration Protocol (NETCONF)", RFC 6020, DOI 10.17487/RFC6020, October 2010, . [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, . [RFC6242] Wasserman, M., "Using the NETCONF Protocol over Secure Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011, . [RFC6520] Seggelmann, R., Tuexen, M., and M. Williams, "Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS) Heartbeat Extension", RFC 6520, DOI 10.17487/RFC6520, February 2012, . [RFC6536] Bierman, A. and M. Bjorklund, "Network Configuration Protocol (NETCONF) Access Control Model", RFC 6536, DOI 10.17487/RFC6536, March 2012, . [RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing", RFC 7230, DOI 10.17487/RFC7230, June 2014, . [RFC7540] Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext Transfer Protocol Version 2 (HTTP/2)", RFC 7540, DOI 10.17487/RFC7540, May 2015, . [RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017, . [RFC8342] Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K., and R. Wilton, "Network Management Datastore Architecture (NMDA)", RFC 8342, DOI 10.17487/RFC8342, March 2018, . [W3C-20150203] "Server-Sent Events, World Wide Web Consortium CR CR- eventsource-20121211", February 2015, . Voit, et al. Expires November 19, 2018 [Page 18] Internet-Draft RESTCONF-Notif May 2018 13.2. Informative References [I-D.draft-ietf-netconf-netconf-event-notifications] Clemm, Alexander., Voit, Eric., Gonzalez Prieto, Alberto., Nilsen-Nygaard, E., and A. Tripathy, "NETCONF support for event notifications", May 2018, . [I-D.draft-ietf-netconf-nmda-restconf] Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K., and R. Wilton, "RESTCONF Extensions to Support the Network Management Datastore Architecture", April 2018, . [RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content", RFC 7231, DOI 10.17487/RFC7231, June 2014, . [RFC7923] Voit, E., Clemm, A., and A. Gonzalez Prieto, "Requirements for Subscription to YANG Datastores", RFC 7923, DOI 10.17487/RFC7923, June 2016, . [RFC8071] Watsen, K., "NETCONF Call Home and RESTCONF Call Home", RFC 8071, DOI 10.17487/RFC8071, February 2017, . Appendix A. RESTCONF over GRPC An initial goal for this document was to support [GRPC] transport seamlessly without any mapping or extra layering. However there is an incompatibility of RESTCONF and GRPC. RESTCONF uses HTTP GET, and GRPC uses HTTP2's POST rather than GET. As GET is used across RESTCONF for things like capabilities exchange, a seamless mapping depends on specification changes outside the scope of this document. If/when GRPC supports GET, or RESTCONF is updated to support POST, this should be revisited. It is hoped that the resulting fix will be transparent to this document. Appendix B. Examples This section is non-normative. To allow easy comparison, this section mirrors the functional examples shown with NETCONF over XML within [I-D.draft-ietf-netconf-netconf-event-notifications]. In Voit, et al. Expires November 19, 2018 [Page 19] Internet-Draft RESTCONF-Notif May 2018 addition, HTTP2 vs HTTP1.1 headers are not shown as the contents of the JSON encoded objects are identical within. B.1. Dynamic Subscriptions B.1.1. Establishing Dynamic Subscriptions The following figure shows two successful "establish-subscription" RPC requests as per [I-D.draft-ietf-netconf-subscribed-notifications]. The first request is given a subscription identifier of 22, the second, an identifier of 23. +------------+ +-----------+ | Subscriber | | Publisher | +------------+ +-----------+ | | |establish-subscription | |------------------------------>| (a) | HTTP 200 OK, id#22, URI#1 | |<------------------------------| (b) |POST (URI#1) | |------------------------------>| (c) | HTTP 200 OK,notif-mesg (id#22)| |<------------------------------| | | | | |stablish-subscription | |------------------------------>| | HTTP 200 OK, id#23, URI#2| |<------------------------------| |POST (URI#2) | |------------------------------>| | | | | | notif-mesg (id#22)| |<------------------------------| | HTTP 200 OK,notif-mesg (id#23)| |<------------------------------| | | Figure 4: Multiple subscriptions over RESTCONF/HTTP To provide examples of the information being transported, example messages for interactions in Figure 4 are detailed below: Voit, et al. Expires November 19, 2018 [Page 20] Internet-Draft RESTCONF-Notif May 2018 POST /restconf/operations/subscriptions:establish-subscription { "establish-subscription": { "stream": { "ietf-netconf-subscribed-notifications" : "NETCONF" }, "stream-xpath-filter": "/ex:foo/", "dscp": "10" } } Figure 5: establish-subscription request (a) As publisher was able to fully satisfy the request, the publisher sends the subscription identifier of the accepted subscription, and the URI: HTTP status code - 200 { "identifier": "22", "uri": "/subscriptions/22" } Figure 6: establish-subscription success (b) Upon receipt of the successful response, the subscriber POSTs to the provided URI to start the flow of notification messages. When the publisher receives this, the subscription becomes ACTIVE (c). POST /restconf/operations/subscriptions/22 Figure 7: establish-subscription subsequent POST While not shown in Figure 4, if the publisher had not been able to fully satisfy the request, or subscriber has no authorization to establish the subscription, the publisher would have sent an RPC error response. For instance, if the "dscp" value of 10 asserted by the subscriber in Figure 5 proved unacceptable, the publisher may have returned: Voit, et al. Expires November 19, 2018 [Page 21] Internet-Draft RESTCONF-Notif May 2018 HTTP status code - 406 { "ietf-restconf:errors" : { "error" : [ { "error-type": "application", "error-tag": "operation-failed", "error-severity": "error", "error-app-tag": "ietf-subscribed-notifications:dscp-unavailable" } ] } } Figure 8: an unsuccessful establish subscription The subscriber can use this information in future attempts to establish a subscription. B.1.2. Modifying Dynamic Subscriptions An existing subscription may be modified. The following exchange shows a negotiation of such a modification via several exchanges between a subscriber and a publisher. This negotiation consists of a failed RPC modification request/response, followed by a successful one. Voit, et al. Expires November 19, 2018 [Page 22] Internet-Draft RESTCONF-Notif May 2018 +------------+ +-----------+ | Subscriber | | Publisher | +------------+ +-----------+ | | | notification message (id#23)| |<-----------------------------| | | |modify-subscription (id#23) | |----------------------------->| (d) | HTTP 406 error (with hint)| |<-----------------------------| (e) | | |modify-subscription (id#23) | |----------------------------->| | HTTP 200 OK | |<-----------------------------| | | | notif-mesg (id#23)| |<-----------------------------| | | Figure 9: Interaction model for successful subscription modification If the subscription being modified in Figure 9 is a datastore subscription as per [I-D.ietf-netconf-yang-push], the modification request made in (d) may look like that shown in Figure 10. As can be seen, the modifications being attempted are the application of a new xpath filter as well as the setting of a new periodic time interval. POST /restconf/operations/subscriptions:modify-subscription { "modify-subscription": { "identifier": "23", { "ietf-yang-push": "datastore-xpath-filter": "/interfaces-state/interface/oper-status" }, { "ietf-yang-push": "periodic": "500" } } } Figure 10: Subscription modification request (c) Voit, et al. Expires November 19, 2018 [Page 23] Internet-Draft RESTCONF-Notif May 2018 If the publisher can satisfy both changes, the publisher sends a positive result for the RPC. If the publisher cannot satisfy either of the proposed changes, the publisher sends an RPC error response (e). The following is an example RPC error response for (e) which includes a hint. This hint is an alternative time period value which might have resulted in a successful modification: HTTP status code - 406 { "ietf-restconf:errors" : { "error" : [ "error-type": "application", "error-tag": "operation-failed", "error-severity": "error", "error-app-tag": { "ietf-yang-push": "ietf-yang-push:period-unsupported" }, "error-info": { "ietf-yang-push": "modify-subscription-datastore-error-info": { "period-hint": "3000" } } ] } } Figure 11: Modify subscription failure with Hint (e) B.1.3. Deleting Dynamic Subscriptions The following demonstrates deleting a subscription. This subscription may have been to either a stream or a datastore. POST /restconf/operations/subscriptions:delete-subscription { "delete-subscription": { "identifier": "22" } } Figure 12: Delete subscription If the publisher can satisfy the request, the publisher replies with success to the RPC request. Voit, et al. Expires November 19, 2018 [Page 24] Internet-Draft RESTCONF-Notif May 2018 If the publisher cannot satisfy the request, the publisher sends an error-rpc element indicating the modification didn't work. Figure 13 shows a valid response for existing valid subscription identifier, but that subscription identifier was created on a different transport session: HTTP status code - 406 { "ietf-restconf:errors" : { "error" : [ "error-type": "application", "error-tag": "operation-failed", "error-severity": "error", "error-app-tag": "ietf-subscribed-notifications:no-such-subscription" ] } } Figure 13: Unsuccessful delete subscription B.2. Configured Subscriptions Configured subscriptions may be established, modified, and deleted using configuration operations against the top-level subtree of [I-D.draft-ietf-netconf-subscribed-notifications] or [I-D.ietf-netconf-yang-push]. In this section, we present examples of how to manage the configuration subscriptions using a HTTP2 client. B.2.1. Creating Configured Subscriptions For subscription creation via configuration operations, a RESTCONF client may send: Voit, et al. Expires November 19, 2018 [Page 25] Internet-Draft RESTCONF-Notif May 2018 POST /restconf/operations/subscriptions/ { "edit-config": { "target": { "running": null }, "default-operation": "none", "config": { "subscriptions": { "subscription": { "identifier": "22", "transport": "HTTP2", "stream": "NETCONF", "receivers": { "receiver": { "name": "receiver1", "address": "1.2.3.4" } } } } } } } Figure 14: Create a configured subscription If the request is accepted, the publisher will indicate this. If the request is not accepted because the publisher cannot serve it, no configuration is changed. In this case the publisher may reply: Voit, et al. Expires November 19, 2018 [Page 26] Internet-Draft RESTCONF-Notif May 2018 HTTP status code - 406 { "ietf-restconf:errors" : { "error" : [ "error-type": "application", "error-tag": "resource-denied", "error-severity": "error", "error-message": { "@lang": "en", "#text": "Temporarily the publisher cannot serve this subscription due to the current workload." } ] } } Figure 15: Response to a failed configured subscription establishment After a subscription has been created and been verified as VALID, HTTP2 connectivity to each receiver will be established if that connectivity does not already exist. The following figure shows the interaction model for the successful creation of a configured subscription. Voit, et al. Expires November 19, 2018 [Page 27] Internet-Draft RESTCONF-Notif May 2018 +----------+ +-----------+ +---------+ |Config Ops| | Publisher | | 1.2.3.4 | +----------+ +-----------+ +---------+ | | | | Capability Exchange | | |<-------------------------->| | | | | | | | | Edit-config | | |--------------------------->| | | RPC Reply: OK | | |<---------------------------| | | | Call Home | | |<-------------->| | | | | | subscription- | | | started | | |--------------->| | | | | | notification | | | message | | |--------------->| Figure 16: Interaction model for configured subscription establishment B.2.2. Modifying Configured Subscriptions Configured subscriptions can be modified using configuration operations against the top-level container "/subscriptions". For example, the subscription established in the previous section could be modified as follows, here a adding a second receiver: Voit, et al. Expires November 19, 2018 [Page 28] Internet-Draft RESTCONF-Notif May 2018 POST /restconf/operations/subscriptions { "edit-config": { "target": { "running": null }, "config": { "subscriptions": { "subscription": { "identifier": "1922", "receivers": { "receiver": { "name": "receiver2", "address": "1.2.3.5" } } } } } } } Figure 17: Modify configured subscription If the request is accepted, the publisher will indicate success. The result is that the interaction model described in Figure 16 may be extended as follows. Voit, et al. Expires November 19, 2018 [Page 29] Internet-Draft RESTCONF-Notif May 2018 +----------+ +-----------+ +---------+ +---------+ |Config Ops| | Publisher | | 1.2.3.4 | | 1.2.3.5 | +----------+ +-----------+ +---------+ +---------+ | | notification | | | | message | | | |--------------->| | | Edit-config | | | |--------------------------->| | | | RPC Reply: OK | | | |<---------------------------| | | | | subscription- | | | | started | | | |---------------------------->| | | | | | | notification | | | | message | | | |--------------->| | | |---------------------------->| | | | | Figure 18: Interaction model for configured subscription modification Note in the above that in the specific example above, modifying a configured subscription actually resulted in "subscription-started" notification. And because of existing HTTP2 connectivity, no additional call home was needed. Also note that if the edit of the configuration had impacted the filter, a separate modify-subscription would have been required for the original receiver. B.2.3. Deleting Configured Subscriptions Configured subscriptions can be deleted using configuration operations against the top-level container "/subscriptions". Deleting the subscription above would result in the following flow impacting all active receivers. Voit, et al. Expires November 19, 2018 [Page 30] Internet-Draft RESTCONF-Notif May 2018 +----------+ +-----------+ +---------+ +---------+ |Config Ops| | Publisher | | 1.2.3.4 | | 1.2.3.5 | +----------+ +-----------+ +---------+ +---------+ | | | | | | notification | | | | message | | | |--------------->| | | |---------------------------->| | | | | | Edit-config | | | |--------------------------->| | | | RPC Reply: OK | | | |<---------------------------| | | | | subscription- | | | | terminated | | | |--------------->| | | |---------------------------->| | | | | Figure 19: Interaction model for configured subscription deletion B.3. Subscription State Notifications A publisher will send subscription state notifications according to the definitions within [I-D.draft-ietf-netconf-subscribed-notifications]). B.3.1. subscription-started and subscription-modified A "subscription-started" encoded in JSON would look like: { "ietf-restconf:notification" : { "eventTime": "2007-09-01T10:00:00Z", "ietf-subscribed-notifications:subscription-started": { "identifier": "39", "transport": "HTTP2", "stream-xpath-filter": "/ex:foo", "stream": { "ietf-netconf-subscribed-notifications" : "NETCONF" } } } } Figure 20: subscription-started subscription state notification Voit, et al. Expires November 19, 2018 [Page 31] Internet-Draft RESTCONF-Notif May 2018 The "subscription-modified" is identical to Figure 20, with just the word "started" being replaced by "modified". B.3.2. subscription-completed, subscription-resumed, and replay- complete A "subscription-completed" would look like: { "ietf-restconf:notification" : { "eventTime": "2007-09-01T10:00:00Z", "ietf-subscribed-notifications:subscription-completed": { "identifier": "39", } } } Figure 21: subscription-completed notification in JSON The "subscription-resumed" and "replay-complete" are virtually identical, with "subscription-completed" simply being replaced by "subscription-resumed" and "replay-complete". B.3.3. subscription-terminated and subscription-suspended A "subscription-terminated" would look like: { "ietf-restconf:notification" : { "eventTime": "2007-09-01T10:00:00Z", "ietf-subscribed-notifications:subscription-terminated": { "identifier": "39", "error-id": "suspension-timeout" } } } Figure 22: subscription-terminated subscription state notification The "subscription-suspended" is virtually identical, with "subscription-terminated" simply being replaced by "subscription- suspended". Voit, et al. Expires November 19, 2018 [Page 32] Internet-Draft RESTCONF-Notif May 2018 Appendix C. Changes between revisions (To be removed by RFC editor prior to publication) v04 - v05 o Error mechanisms updated to match embedded RESTCONF mechanisms o Restructured format and sections of document. o Added a YANG data model for HTTP specific parameters. o Mirrored the examples from the NETCONF transport draft to allow easy comparison. v03 - v04 o Draft not fully synched to new version of subscribed-notifications yet. o References updated v02 - v03 o Event notification reframed to notification message. o Tweaks to wording/capitalization/format. v01 - v02 o Removed sections now redundant with [I-D.draft-ietf-netconf-subscribed-notifications] and [I-D.ietf-netconf-yang-push] such as: mechanisms for subscription maintenance, terminology definitions, stream discovery. o 3rd party subscriptions are out-of-scope. o SSE only used with RESTCONF and HTTP1.1 dynamic subscriptions o Timeframes for event tagging are self-defined. o Clean-up of wording, references to terminology, section numbers. v00 - v01 o Removed the ability for more than one subscription to go to a single HTTP2 stream. Voit, et al. Expires November 19, 2018 [Page 33] Internet-Draft RESTCONF-Notif May 2018 o Updated call flows. Extensively. o SSE only used with RESTCONF and HTTP1.1 dynamic subscriptions o HTTP is not used to determine that a receiver has gone silent and is not Receiving Event Notifications o Many clean-ups of wording and terminology Authors' Addresses Eric Voit Cisco Systems Email: evoit@cisco.com Einar Nilsen-Nygaard Cisco Systems Email: einarnn@cisco.com Alexander Clemm Huawei Email: ludwig@clemm.org Andy Bierman YumaWorks Email: andy@yumaworks.com Voit, et al. Expires November 19, 2018 [Page 34]