draft-ietf-i2rs-pub-sub-requirements-01.txt   draft-ietf-i2rs-pub-sub-requirements-02.txt 
Interface to the Routing System (i2rs) E. Voit Interface to the Routing System (i2rs) E. Voit
Internet-Draft A. Clemm Internet-Draft A. Clemm
Intended status: Informational A. Gonzalez Prieto Intended status: Informational A. Gonzalez Prieto
Expires: September 10, 2015 Cisco Systems Expires: September 27, 2015 Cisco Systems
March 9, 2015 March 26, 2015
Requirements for Subscription to YANG Datastores Requirements for Subscription to YANG Datastores
draft-ietf-i2rs-pub-sub-requirements-01 draft-ietf-i2rs-pub-sub-requirements-02
Abstract Abstract
This document provides requirements for a service that allows client This document provides requirements for a service that allows client
applications to subscribe to updates of a YANG datastore. Based on applications to subscribe to updates of a YANG datastore. Based on
criteria negotiated as part of a subscription, updates will be pushed criteria negotiated as part of a subscription, updates will be pushed
to targeted recipients. Such a capability eliminates the need for to targeted recipients. Such a capability eliminates the need for
periodic polling of YANG datastores by applications and fills a periodic polling of YANG datastores by applications and fills a
functional gap in existing YANG transports (i.e. Netconf and functional gap in existing YANG transports (i.e. Netconf and
Restconf). Such a service can be summarized as a "pub/sub" service Restconf). Such a service can be summarized as a "pub/sub" service
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on September 10, 2015. This Internet-Draft will expire on September 27, 2015.
Copyright Notice Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Business Drivers . . . . . . . . . . . . . . . . . . . . . . 3 2. Business Drivers . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Pub/Sub in I2RS . . . . . . . . . . . . . . . . . . . . . 4 2.1. Pub/Sub in I2RS . . . . . . . . . . . . . . . . . . . . . 4
2.2. Pub/Sub variants on Network Elements . . . . . . . . . . 5 2.2. Pub/Sub variants on Network Elements . . . . . . . . . . 5
2.3. Existing Generalized Pub/Sub Implementations . . . . . . 6 2.3. Existing Generalized Pub/Sub Implementations . . . . . . 6
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6
4. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 7 4. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 8
4.1. Assumptions for Subscriber Behavior . . . . . . . . . . . 7 4.1. Assumptions for Subscriber Behavior . . . . . . . . . . . 8
4.2. Subscription Service Requirements . . . . . . . . . . . . 8 4.2. Subscription Service Requirements . . . . . . . . . . . . 8
4.2.1. General . . . . . . . . . . . . . . . . . . . . . . . 8 4.2.1. General . . . . . . . . . . . . . . . . . . . . . . . 8
4.2.2. Negotiation . . . . . . . . . . . . . . . . . . . . . 10 4.2.2. Negotiation . . . . . . . . . . . . . . . . . . . . . 10
4.2.3. Update Distribution . . . . . . . . . . . . . . . . . 10 4.2.3. Update Distribution . . . . . . . . . . . . . . . . . 10
4.2.4. Transport . . . . . . . . . . . . . . . . . . . . . . 11 4.2.4. Transport . . . . . . . . . . . . . . . . . . . . . . 11
4.2.5. Security Requirements . . . . . . . . . . . . . . . . 11 4.2.5. Security Requirements . . . . . . . . . . . . . . . . 11
4.2.6. QoS Requirements . . . . . . . . . . . . . . . . . . 12 4.2.6. Subscription QoS . . . . . . . . . . . . . . . . . . 12
4.2.7. Filtering . . . . . . . . . . . . . . . . . . . . . . 13 4.2.7. Filtering . . . . . . . . . . . . . . . . . . . . . . 14
4.2.8. Assurance and Monitoring . . . . . . . . . . . . . . 14 4.2.8. Assurance and Monitoring . . . . . . . . . . . . . . 14
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 14 5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 15
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 14 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 15
6.1. Normative References . . . . . . . . . . . . . . . . . . 14 6.1. Normative References . . . . . . . . . . . . . . . . . . 15
6.2. Informative References . . . . . . . . . . . . . . . . . 15 6.2. Informative References . . . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16
1. Introduction 1. Introduction
YANG has gained acceptance as the data definition language of choice YANG has gained acceptance as the data definition language of choice
for control and management related information. Applications that for control and management related information. Applications that
interact with YANG datastores are extending beyond traditional interact with YANG datastores are extending beyond traditional
configuration of network elements. In many cases these applications configuration of network elements. In many cases these applications
are aimed at service-assurance, which involves monitoring of are aimed at service-assurance, which involves monitoring of
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It is time to incorporate such generic object subscription mechanisms It is time to incorporate such generic object subscription mechanisms
as part of Network Elements, and allow these mechanisms to be applied as part of Network Elements, and allow these mechanisms to be applied
in the context of data that is conceptually contained in YANG in the context of data that is conceptually contained in YANG
datastores. With such mechanisms, both controller and local Network datastores. With such mechanisms, both controller and local Network
Element based applications can have access to a set of consistent Element based applications can have access to a set of consistent
network information driven via push from peer Network Elements which network information driven via push from peer Network Elements which
host authoritative information. host authoritative information.
There are some valid IETF starting points and contexts for these There are some valid IETF starting points and contexts for these
mechanisms. For example Netconf Event Notifications [RFC5277] mechanisms. For example NETCONF Event Notifications [RFC5277]
provides a useful tool for an end-to-end solution. However RFC5277 provides a useful tool for an end-to-end solution. However RFC5277
does not follow the Pub/Sub paradigm, does not allow the explicit does not follow the Pub/Sub paradigm, does not allow the explicit
deletion of subscriptions, and predates YANG. [RFC6470] defines deletion of subscriptions, and predates YANG. Predating YANG is an
configuration change notifications, but doesn't provide the actual issue, as monitoring and filtering based on YANG subtrees becomes
configuration change. problematic . [RFC6470] defines configuration change notifications,
but doesn't provide the actual configuration change.
Because of this, the authors have put forward this requirements Because of this, the authors have put forward this requirements
document as well as [datastore-push]. We are hoping these could document as well as [datastore-push]. We believe these provide a
provide a context upon which to create new solution. context upon which to create new solution. It is intended that these
documents include requirements and provide technologies applicable
beyond I2RS.
2. Business Drivers 2. Business Drivers
For decades, information delivery of current network state has been For decades, information delivery of current network state has been
accomplished either by fetching from operations interfaces, or via accomplished either by fetching from operations interfaces, or via
dedicated, customized networking protocols. With the growth of SDN, dedicated, customized networking protocols. With the growth of SDN,
imperative policy distribution, and YANG's ascent as a dominant imperative policy distribution, and YANG's ascent as a dominant
programmatic interface to network elements, this mixture of fetch programmatic interface to network elements, this mixture of fetch
plus custom networking protocols is no longer sufficient. What is plus custom networking protocols is no longer sufficient. What is
needed is a push mechanism that is able to deliver objects and object needed is a push mechanism that is able to deliver objects and object
changes as they happen. changes as they happen.
These push distribution mechanisms will not replace existing These push distribution mechanisms will not replace existing
networking protocols. Instead they will supplement these protocols, networking protocols. Instead they will supplement these protocols,
providing different response time, peering, scale, and security providing different response time, peering, scale, and security
characteristics. characteristics.
At the same time, SNMP and MIBs are still widely deployed and the de- At the same time, SNMP and MIBs are still widely deployed and the
facto choice for many monitoring solutions. Those solutions do not defacto choice for many monitoring solutions. Those solutions do not
require support for configuration transactions and the need to require support for configuration transactions and the need to
validate and maintain configuration consistency, hence there is less validate and maintain configuration consistency, hence there is less
pressure to abandon SNMP and MIBs. Arguably the biggest shortcoming pressure to abandon SNMP and MIBs. Arguably the biggest shortcoming
of SNMP for those applications concerns the need to rely on periodic of SNMP for those applications concerns the need to rely on periodic
polling, because it introduces additional load on the network and polling, because it introduces additional load on the network and
devices, is brittle in case polling cycles are missed, and is hard to devices, is brittle in case polling cycles are missed, and is hard to
synchronize and calibrate across a network, making data obtained from synchronize and calibrate across a network, making data obtained from
multiple devices less comparable. If applications need to apply multiple devices less comparable. If applications need to apply
those same interaction patterns for YANG datastores, similar issues those same interaction patterns for YANG datastores, similar issues
can be expected. Migration to YANG datastores by applications that can be expected. Migration to YANG datastores by applications that
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subscriptions to data with the following parameters: push of data subscriptions to data with the following parameters: push of data
synchronously or asynchronously via registered subscriptions... synchronously or asynchronously via registered subscriptions...
o L-DATA-REQ-07: The I2RS interface (protocol and IMs) should allow o L-DATA-REQ-07: The I2RS interface (protocol and IMs) should allow
a subscribe to select portions of the data model. a subscribe to select portions of the data model.
o PI-REQ01: monitor the available routes installed in the RIB of o PI-REQ01: monitor the available routes installed in the RIB of
each forwarding device, including near real time notification of each forwarding device, including near real time notification of
route installation and removal. route installation and removal.
o BGP-REQ10: I2RS client SHOULD be able instruct the I2RS agent(s) o BGP-REQ10: I2RS client should be able instruct the I2RS agent(s)
to notify the I2RS client when the BGP processes on an associated to notify the I2RS client when the BGP processes on an associated
routing system observe a route change to a specific set of IP routing system observe a route change to a specific set of IP
Prefixes and associated prefixes....The I2RS agent should be able Prefixes and associated prefixes....The I2RS agent should be able
to notify the client via publish or subscribe mechanism. to notify the client via publish or subscribe mechanism.
o IGP-REQ-07: The I2RS interface (protocol and IMs) should support a o IGP-REQ-07: The I2RS interface (protocol and IMs) should support a
mechanism where the I2RS Clients can subscribe to the I2RS Agent's mechanism where the I2RS Clients can subscribe to the I2RS Agent's
notification of critical node IGP events. notification of critical node IGP events.
o MPLS-LDP-REQ-03: The I2RS Agent notifications should allow an I2RS o MPLS-LDP-REQ-03: The I2RS Agent notifications should allow an I2RS
client to subscribe to a stream of state changes regarding the LDP client to subscribe to a stream of state changes regarding the LDP
sessions or LDP LSPs from the I2RS Agent. sessions or LDP LSPs from the I2RS Agent.
o L-Data-REQ-01: I2rs must be able to collect large data set from o L-Data-REQ-01: I2rs must be able to collect large data set from
the network with high frequency and resolution with minimal impact the network with high frequency and resolution with minimal impact
to the device's CPU and memory. to the device's CPU and memory.
And [i2rs-traceability] has Pub/Sub requirements listed in And [i2rs-traceability] has Pub/Sub requirements listed in
Section 7.4.3. Section 7.4.3.
o I2RS Agents SHOULD support publishing I2RS trace log information o I2RS Agents should support publishing I2RS trace log information
to that feed as described in [i2rs-arch]. Subscribers would then to that feed as described in [i2rs-arch]. Subscribers would then
receive a live stream of I2RS interactions in trace log format and receive a live stream of I2RS interactions in trace log format and
could flexibly choose to do a number of things with the log could flexibly choose to do a number of things with the log
messages messages
There are additional individual drafts such as [i2rs-pubsub-security] There are additional individual drafts such as [i2rs-pubsub-security]
documenting the Pub/Sub needs for: time delivery sensitivity, support documenting the Pub/Sub needs for: time delivery sensitivity, support
for multiple transport protocols, secure/authorized communications, for multiple transport protocols, secure/authorized communications,
and support for a range specification of subscribed data delivery and support for a range specification of subscribed data delivery
content. So the list above should not be considered exhaustive. content. So the list above should not be considered exhaustive.
2.2. Pub/Sub variants on Network Elements 2.2. Pub/Sub variants on Network Elements
Looking at history, there are many examples of switching and routing This document is intended to cover requirements beyond I2RS. Looking
at history, there are many examples of switching and routing
protocols which have done explicit or implicit pub/sub in the past. protocols which have done explicit or implicit pub/sub in the past.
In addition, new policy notification mechanisms which operate on In addition, new policy notification mechanisms which operate on
Switches and Routers are being specified now. A very small subset of Switches and Routers are being specified now. A very small subset of
these includes: these includes:
o Routing Adjacencies in MPLS VPNs [RFC6513] o Routing Adjacencies in MPLS VPNs [RFC6513]
o OSPF Route Flooding [RFC2328] o OSPF Route Flooding [RFC2328]
o Multicast topology establishment protocols (IGMP, PIM, etc.) o Multicast topology establishment protocols (IGMP, PIM, etc.)
o Audio-Video Bridging streams needing guaranteed latency o Audio-Video Bridging streams needing guaranteed latency
[AVB-latency] (802.1Q-2011 Clause 35) [AVB-latency] (802.1Q-2011 Clause 35)
o Secure Automation and Continuous Monitoring (SACM) o Secure Automation and Continuous Monitoring (SACM)
[sacm-requirements] [sacm-requirements]
o "Peer Mount" subscriptions for configuration verification between o "Peer Mount" subscriptions for configuration verification between
peers[draft-voit-netmod] peers[draft-voit-netmod]
Worthy of note in the list above is the wide variety of broadcast, Worthy of note in the list above is the wide variety of broadcast,
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owner of the YANG datastore that is subjected to the Subscription. owner of the YANG datastore that is subjected to the Subscription.
A Receiver is the target where a Publisher pushes updates. In A Receiver is the target where a Publisher pushes updates. In
general, the Receiver and Subscriber will be the same entity. A general, the Receiver and Subscriber will be the same entity. A
Subscription Service provides Subscriptions to Subscribers of YANG Subscription Service provides Subscriptions to Subscribers of YANG
data. data.
A Subscription Service interacts with the Publisher of the YANG data A Subscription Service interacts with the Publisher of the YANG data
as needed to provide the data per the terms of the Subscription. as needed to provide the data per the terms of the Subscription.
A Subscription Request for one or more YANG subtrees made by the A Subscription Request for one or more YANG subtrees (including
Subscriber of a Publisher and targeted to a Receiver. A Subscription single leafs) made by the Subscriber of a Publisher and targeted to a
MAY include constraints which dictates how often or under what Receiver. A Subscription may include constraints which dictate how
conditions YANG subtree updates might be sent. often or under what conditions YANG information updates might be
sent.
A Subscription is a contract between a Subscription Service and a A Subscription is a contract between a Subscription Service and a
Subscriber that stipulates the data to be pushed and the associated Subscriber that stipulates the data to be pushed and the associated
terms. terms.
A YANG datastore is a conceptual datastore that contains hierarchical A YANG datastore is a conceptual datastore that contains hierarchical
data defined in YANG data models. It is what is referred in existing data defined in YANG data models. It is what is referred in existing
RFCs as "Netconf datastore". However, as the same datastore is no RFCs as "NETCONF datastore". However, as the same datastore is no
longer tied to Netconf as a specific transport, the term "YANG longer tied to NETCONF as a specific transport, the term "YANG
datastore" is deemed more appropriate. datastore" is deemed more appropriate.
An Update provides object changes which have occurred within An Update provides object changes which have occurred within
subscribed YANG subtree(s). An Update MUST include the current subscribed YANG subtree(s). An Update must include the current
status of (data) node instances which according to any filtering are status of (data) node instances which according to any filtering are
reportably different from the previously provided state. An Update reportably different from the previously provided state. An Update
MAY include a bundled set of ordered/sequential changes for a given may include a bundled set of ordered/sequential changes for a given
object which have been made since the last update. object which have been made since the last update.
A Filter contains evaluation criteria which are evaluated against A Filter contains evaluation criteria which are evaluated against
YANG object(s) within a Subscription. There are two types of YANG object(s) within a Subscription. There are two types of
Filters: Subtree Filters which identify selected objects/nodes Filters: Subtree Filters which identify selected objects/nodes
published under a target data node, and object Property Filters where published under a target data node, and object Property Filters where
an object should only be published if it has propert(ies) meeting an object should only be published if it has propert(ies) meeting
specified Filter criteria. For "on-change" notifications, passing specified Filter criteria. For "on-change" notifications, passing
through the Filter requires that a subscribed object is now different through the Filter requires that a subscribed object is now different
that from the previous Push, AND at least one of the YANG objects that from the previous Push, AND at least one of the YANG objects
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However In order to frame the desired behavior of the Subscription However In order to frame the desired behavior of the Subscription
Service, it is important to specify key input constraints. Service, it is important to specify key input constraints.
4.2. Subscription Service Requirements 4.2. Subscription Service Requirements
This document provides requirements for the Subscription Service. It This document provides requirements for the Subscription Service. It
does not define all the requirements for the Subscriber/Receiver. does not define all the requirements for the Subscriber/Receiver.
However In order to frame the desired behavior of the Subscription However In order to frame the desired behavior of the Subscription
Service, it is important to specify key input constraints. Service, it is important to specify key input constraints.
A Subscriber SHOULD avoid attempting to establish multiple A Subscriber should avoid attempting to establish multiple
Subscriptions pertaining to the same information, i.e. referring to Subscriptions pertaining to the same information, i.e. referring to
the same datastore YANG subtrees. the same datastore YANG subtrees.
A Subscriber MAY provide QoS criteria to the Subscription Service A Subscriber may provide Subscription QoS criteria to the
such that if the Subscription Service is unable to meet those Subscription Service such that if the Subscription Service is unable
criteria, the Subscription should not be established. to meet those criteria, the Subscription should not be established.
When a Subscriber needs to restart, it is acceptable for the When a Subscriber needs to restart, it is acceptable for the
Subscriber to have to resubscribe. There is no requirement for the Subscriber to have to resubscribe. There is no requirement for the
life span of the Subscription to extend beyond the life span of the life span of the Subscription to extend beyond the life span of the
Subscriber. Subscriber.
A Subscriber MUST be able to infer when a Subscription Service is no A Subscriber must be able to infer when a Subscription Service is no
longer active and when no more updates are being sent. longer active and when no more updates are being sent.
A Subscriber MAY check with a Subscription Service to validate the A Subscriber may check with a Subscription Service to validate the
existence and monitored subtrees of a Subscription. existence and monitored subtrees of a Subscription.
A Subscriber MUST be able to periodically lease and re-lease a A Subscriber must be able to periodically lease and re-lease a
Subscription from a Subscription Service. Subscription from a Subscription Service.
4.2.1. General 4.2.1. General
A Subscription Service MUST support the ability to create, renew, A Subscription Service must support the ability to create, renew,
timeout, and terminate a Subscription. timeout, and terminate a Subscription.
A Subscription Service MUST be able to support and independently A Subscription Service must be able to support and independently
track one or more Subscription Requests by the same Subscriber. track one or more Subscription Requests by the same Subscriber.
A Subscription Service MUST be able to support an add/change/delete A Subscription Service must be able to support an add/change/delete
of one or more YANG subtrees as part of the same Subscription of one or more YANG subtrees as part of the same Subscription
Request. Request.
A Subscription Service MUST support Subscriptions against operational A Subscription Service must support Subscriptions against operational
datastores, configuration datastores, or both. datastores, configuration datastores, or both.
A Subscription Service MUST be able support a Subtree Filter so that A Subscription Service must be able support a Subtree Filter so that
subscribed updates under a target node might publish only operational subscribed updates under a target node might publish only operational
data, only configuration data, or both. data, only configuration data, or both.
A Subscription MAY include filters as defined within a Subscription A Subscription may include filters as defined within a Subscription
Request, the Subscription Service MUST publish only data nodes that Request, the Subscription Service must publish only data nodes that
meet the filter criteria. meet the filter criteria.
A Subscription Service MUST support the ability to subscribe to A Subscription Service must support the ability to subscribe to
periodic updates. The subscription period MUST be configurable as periodic updates. The subscription period must be configurable as
part of the subscription request. part of the subscription request.
A Subscription Service SHOULD support the ability to subscribe to A Subscription Service should support the ability to subscribe to
updates "on-change", i.e. whenever values of subscribed data objects updates "on-change", i.e. whenever values of subscribed data objects
change. change.
For "on-change" updates, the Subscription Service MUST support a For "on-change" updates, the Subscription Service must support a
dampening period that needs to pass before the first or subsequent dampening period that needs to pass before the first or subsequent
"on-change" updates are sent. The dampening period SHOULD be "on-change" updates are sent. The dampening period should be
configurable as part of the subscription request. configurable as part of the subscription request.
A Subscription Service MUST allow Subscriptions to be monitored. A Subscription Service must allow Subscriptions to be monitored.
Specifically, a Subscription Service MUST at a minimum maintain Specifically, a Subscription Service must at a minimum maintain
information about which Subscriptions are being serviced, the terms information about which Subscriptions are being serviced, the terms
of those subscriptions (e.g. what data is being subscribed, of those subscriptions (e.g. what data is being subscribed,
associated filters, update policy - on change, periodic), and the associated filters, update policy - on change, periodic), and the
overall status of the Subscription - e.g. active or suspended. overall status of the Subscription - e.g. active or suspended.
A Subscription Service SHOULD be able to interpret Subscription A Subscription Service should be able to interpret Subscription QoS
Requests QoS Policy requests, and only establish a Subscription if it parameters, and only establish a Subscription if it is possible to
is possible to meet the QoS those QoS Policy requests. meet the QoS needs of the provided QoS parameters.
A Subscription Service MUST support terminating of a Subscription A Subscription Service must support terminating of a Subscription
when requested by the Subscriber. when requested by the Subscriber.
A Subscription Service SHOULD support the ability to suspend and to A Subscription Service should support the ability to suspend and to
resume a Subscription on request of a client. resume a Subscription on request of a client.
A Subscription Service MAY at its discretion revoke or suspend an A Subscription Service may at its discretion revoke or suspend an
existing subscription. Reasons MAY include transitory resource existing subscription. Reasons may include transitory resource
limitation, credential expiry, failure to reconfirm a subscription, limitation, credential expiry, failure to reconfirm a subscription,
loss of connectivity with the Receiver, operator CLI, and/or others. loss of connectivity with the Receiver, operator CLI, and/or others.
When this occurs, the Subscription Service MUST notify the Subscriber When this occurs, the Subscription Service must notify the Subscriber
and update subscription status. and update subscription status.
A Subscription Service MAY offer the ability to modify a subscription A Subscription Service may offer the ability to modify a subscription
filter. If such an ability is offered, the service MUST provide filter. If such an ability is offered, the service must provide
subscribers with an indication at what point the modified subscribers with an indication at what point the modified
subscription goes into effect. subscription goes into effect.
4.2.2. Negotiation 4.2.2. Negotiation
A Subscription Service MUST be able to negotiate the following terms A Subscription Service must be able to negotiate the following terms
of a Subscription: of a Subscription:
o The policy: i.e. whether updates are on-change of periodic o The policy: i.e. whether updates are on-change of periodic
o The interval, for periodic publication policy o The interval, for periodic publication policy
o The dampening period, for on-change update policy o The dampening period, for on-change update policy
o Any filters associated with a subtree subscription o Any filters associated with a subtree subscription
A Subscription Service SHOULD be able to negotiate QoS criteria for a A Subscription Service should be able to negotiate QoS criteria for a
Subscription. Examples of QoS criteria MAY include reliability of Subscription. Examples of Subscription QoS criteria may include
the Subscription Service, reaction time between a monitored YANG reliability of the Subscription Service, reaction time between a
subtree/object change and a corresponding notification push, and the monitored YANG subtree/object change and a corresponding notification
Subscription Service's ability to support certain levels of object push, and the Subscription Service's ability to support certain
liveliness. levels of object liveliness.
In cases where a Subscription Request cannot be fulfilled, the In cases where a Subscription Request cannot be fulfilled, the
Subscription Service MUST include in its decline a set of criteria Subscription Service must include in its decline a set of criteria
that would have been acceptable when the Subscription Request was that would have been acceptable when the Subscription Request was
made. For example, if periodic updates were requested with too short made. For example, if periodic updates were requested with too short
update intervals for the specified data set, the minimum acceptable update intervals for the specified data set, the minimum acceptable
interval period SHOULD be included. If on-change updates were interval period should be included. If on-change updates were
requested with a dampening period, the minimum acceptable dampening requested with a dampening period, the minimum acceptable dampening
period SHOULD be included, or an indication whether only periodic period should be included, or an indication whether only periodic
updates are supported along with the minimum acceptable interval updates are supported along with the minimum acceptable interval
period for the data set being subscribed to. period for the data set being subscribed to.
4.2.3. Update Distribution 4.2.3. Update Distribution
For "on-change" updates, the Subscription Service MUST only send For "on-change" updates, the Subscription Service must only send
deltas to the object data for which a change occurred. [Otherwise deltas to the object data for which a change occurred. [Otherwise
the subscriber will not know what has actually undergone change.] the subscriber will not know what has actually undergone change.]
The updates for each object needs to include an indication whether it The updates for each object needs to include an indication whether it
was removed, added, or changed. was removed, added, or changed.
When a Subscription Service is not able to send updates per its When a Subscription Service is not able to send updates per its
subscription contract, the Subscription MUST notify subscribers and subscription contract, the Subscription must notify subscribers and
put the subscription into a state of indicating the Subscription was put the subscription into a state of indicating the Subscription was
suspended by the service. When able to resume service, subscribers suspended by the service. When able to resume service, subscribers
need to be notified as well. If unable to resume service, the need to be notified as well. If unable to resume service, the
Subscription Service MAY terminate the subscription and notify Subscription Service may terminate the subscription and notify
Subscribers accordingly. Subscribers accordingly.
When a Subscription with "on-change" updates is suspended and then When a Subscription with "on-change" updates is suspended and then
resumed, the first update SHOULD include updates of any changes that resumed, the first update should include updates of any changes that
occurred while the Subscription was suspended, with the current occurred while the Subscription was suspended, with the current
value. The Subscription Service MUST provide a clear indication when value. The Subscription Service must provide a clear indication when
this capability is not supported (because in this case a client this capability is not supported (because in this case a client
application may have to synchronize state separately). application may have to synchronize state separately).
A Subscription Service MAY, as an option, support a persistence/ Multiple objects being pushed to a Subscriber, perhaps from different
Subscriptions, should be bundled together into a single Update.
The sending of an Update must not be delayed beyond the Push Latency
of any enclosed object changes.
The sending of an Update must not be delayed beyond the dampening
period of any enclosed object changes.
The sending of an Update must not occur before the dampening period
expires for any enclosed object changes.
A Subscription Service may, as an option, support a persistence/
replay capability. replay capability.
4.2.4. Transport 4.2.4. Transport
A Subscription Service SHOULD support different transports. A Subscription Service should support different transports.
A Subscription Service SHOULD support different encodings of payload. A Subscription Service should support different encodings of payload.
It MUST be possible for Receivers to associate the update with a It must be possible for Receivers to associate the update with a
specific Subscription. specific Subscription.
In the case of connection-oriented transport, when a transport In the case of connection-oriented transport, when a transport
connection drops, the associated Subscription SHOULD be terminated. connection drops, the associated Subscription should be terminated.
It is up the Subscriber to request a new Subscription. It is up the Subscriber to request a new Subscription.
4.2.5. Security Requirements 4.2.5. Security Requirements
As part of the Subscription establishment, there MUST be mutual As part of the Subscription establishment, there must be mutual
authentication between the Subscriber and the Subscription Service. authentication between the Subscriber and the Subscription Service.
When there are multiple Subscribers, it SHOULD be possible to provide When there are multiple Subscribers, it should be possible to provide
cryptographic authentication in such a way that no Subscriber can cryptographic authentication in such a way that no Subscriber can
pose as the original Subscription Service. pose as the original Subscription Service.
Versioning MUST be supported. Versioning must be supported.
A Subscription could be used to attempt to retrieve information that A Subscription could be used to attempt to retrieve information that
a client has not authorized access to. Therefore it is important a client has not authorized access to. Therefore it is important
that data pushed based on Subscriptions is authorized in the same way that data pushed based on Subscriptions is authorized in the same way
that regular data retrieval operations are. Data being pushed to a that regular data retrieval operations are. Data being pushed to a
client MUST be filtered accordingly, just like if the data were being client must be filtered accordingly, just like if the data were being
retrieved on-demand. For Unicast transports, the Netconf retrieved on-demand. For Unicast transports, the NETCONF
Authorization Control Model applies. Authorization Control Model applies.
Additions or changes within a subscribed subtree structure must be
validated against authorization methods before Subscription Updates
including new subtree information are pushed.
A loss of authenticated access to subtree or node SHOULD be
communicated to the Subscriber
Subscription requests, including requests to create, terminate, Subscription requests, including requests to create, terminate,
suspend, and resume Subscriptions MUST be properly authorized. suspend, and resume Subscriptions must be properly authorized.
When the Subscriber and Receiver are different, the Receiver MUST be When the Subscriber and Receiver are different, the Receiver must be
able to terminate any Subscription to it where objects are being able to terminate any Subscription to it where objects are being
delivered over a Unicast transport. delivered over a Unicast transport.
A Subscription Service SHOULD decline a Subscription Request if it A Subscription Service should decline a Subscription Request if it
would deplete its resources. It is preferable to decline a would deplete its resources. It is preferable to decline a
Subscription when originally requested, rather than having to Subscription when originally requested, rather than having to
terminate it prematurely later. terminate it prematurely later.
4.2.6. QoS Requirements 4.2.6. Subscription QoS
A Subscription Service SHOULD be able to negotiate the following QoS A Subscription Service should be able to negotiate the following
parameters with a Subscriber: Dampening, Reliability, Deadline, Subscription QoS parameters with a Subscriber: Dampening,
Bundling. Reliability, Deadline, Bundling.
4.2.6.1. Liveliness 4.2.6.1. Liveliness
A Subscription Service MUST be able to respond to requests to verify A Subscription Service must be able to respond to requests to verify
the Liveliness of a subscription. the Liveliness of a subscription.
A Subscription Service MUST be able to report the currently monitored A Subscription Service must be able to report the currently monitored
Nodes of a Subscription. Nodes of a Subscription.
4.2.6.2. Dampening 4.2.6.2. Dampening
A Subscription Service MUST be able to negotiate the minimum time A Subscription Service must be able to negotiate the minimum time
separation since the previous update before transmitting a subsequent separation since the previous update before transmitting a subsequent
update for Subscription. (Note: this is intended to confine the update for Subscription. (Note: this is intended to confine the
visibility of volatility into something digestible by the receiver.) visibility of volatility into something digestible by the receiver.)
4.2.6.3. Reliability 4.2.6.3. Reliability
A Subscription Service MAY send Updates over Best Effort and Reliable A Subscription Service may send Updates over Best Effort and Reliable
transports. transports.
4.2.6.4. Coherence 4.2.6.4. Coherence
Every update to a subscribed object MUST be sent to the Receiver in Every update to a subscribed object must be sent to the Receiver in
sequential order. sequential order.
4.2.6.5. Presentation 4.2.6.5. Presentation
The Subscription Service SHOULD have the ability to bundle a set of The Subscription Service should have the ability to bundle a set of
discrete object notifications into a single publishable update for a discrete object notifications into a single publishable update for a
Subscription. A bundle MAY include information on different Data Subscription. A bundle may include information on different Data
Nodes and/or multiple updates about a single Data Node. Nodes and/or multiple updates about a single Data Node.
For any bundled updates, the Subscription Service MUST provide For any bundled updates, the Subscription Service must provide
information for a Receiver to reconstruct the order and timing of information for a Receiver to reconstruct the order and timing of
updates. updates.
4.2.6.6. Deadline 4.2.6.6. Deadline
The Subscription Service MUST be able to push updates at a regular The Subscription Service must be able to push updates at a regular
cadence that corresponds with Subscriber specified start and end cadence that corresponds with Subscriber specified start and end
timestamps. (Note: the regular cadence can drive one, a discrete timestamps. (Note: the regular cadence can drive one, a discrete
quantity, or an unbounded set of periodic updates.) quantity, or an unbounded set of periodic updates.)
4.2.6.7. Push Latency 4.2.6.7. Push Latency
It MUST be possible for an administrative entity to determine the The Subscription Service should be able to delay Updates on object
push for a configurable period per Subscriber.
It must be possible for an administrative entity to determine the
Push latency between object change in a monitored subtree and the Push latency between object change in a monitored subtree and the
Subscription Service Push of the update transmission. Subscription Service Push of the update transmission.
4.2.7. Filtering 4.2.7. Filtering
If no filtering criteria are provided, or if filtering criteria are If no filtering criteria are provided, or if filtering criteria are
met, updates for a subscribed object MUST be pushed, subject to the met, updates for a subscribed object must be pushed, subject to the
QoS limits established for the subscription. QoS limits established for the subscription.
It MUST be possible for the Subscription Service to receive Filter(s) It must be possible for the Subscription Service to receive Filter(s)
from a Subscriber and apply them to corresponding object(s) within a from a Subscriber and apply them to corresponding object(s) within a
Subscription. Subscription.
It MUST be possible to attach one or more Subtree and/or Property It must be possible to attach one or more Subtree and/or Property
Filters to a subscription. Mandatory Property Filter types include: Filters to a subscription. Mandatory Property Filter types include:
o For character based object properties, filter values which are o For character based object properties, filter values which are
exactly equal to a provided string, not equal to the string, or exactly equal to a provided string, not equal to the string, or
containing a string. containing a string.
o For numeric based object properties, filter values which are =, o For numeric based object properties, filter values which are =,
!=, <, <=, >, >= a provided number. !=, <, <=, >, >= a provided number.
It SHOULD be possible for Property Filtering criteria to evaluate It should be possible for Property Filtering criteria to evaluate
more than one property of a particular subscribed object as well as more than one property of a particular subscribed object as well as
apply multiple filters against a single property. apply multiple filters against a single property.
It SHOULD be possible to establish query match criteria on additional It should be possible to establish query match criteria on additional
objects to be used in conjunction with Property Filtering criteria on objects to be used in conjunction with Property Filtering criteria on
a subscribed object. (For example: if A has changed AND B=1, then a subscribed object. (For example: if A has changed AND B=1, then
Push A.) (Note: Query match capability MAY be done on objects within Push A.) (Note: Query match capability may be done on objects within
the datastore even if those objects are not included within the the datastore even if those objects are not included within the
subscription. This of course assumes the subscriber has read access subscription. This of course assumes the subscriber has read access
to those objects.) to those objects.)
4.2.8. Assurance and Monitoring 4.2.8. Assurance and Monitoring
It MUST be possible to fetch the state of a single subscription from It must be possible to fetch the state of a single subscription from
a Subscription Service. a Subscription Service.
It MUST be possible to fetch the state of all subscriptions of a It must be possible to fetch the state of all subscriptions of a
particular Subsciber. particular Subscriber.
It MUST be possible to fetch a list and status of all Subscription It must be possible to fetch a list and status of all Subscription
Requests over a period of time. If there us a failure, some failure Requests over a period of time. If there us a failure, some failure
reasons might include: reasons might include:
o Improper security credentials provided to access the target node o Improper security credentials provided to access the target node
o Target node referenced does not exist o Target node referenced does not exist
o Subscription type requested is not available upon the target node o Subscription type requested is not available upon the target node
o Out of resources, or resources not available o Out of resources, or resources not available
o Incomplete negotiations with the Subscriber. o Incomplete negotiations with the Subscriber.
5. Acknowledgements 5. Acknowledgements
We wish to acknowledge the helpful contributions, comments, and We wish to acknowledge the helpful contributions, comments, and
suggestions that were received from Ambika Tripathy and Prabhakara suggestions that were received from Ambika Tripathy and Prabhakara
skipping to change at page 16, line 23 skipping to change at line 753
Monitoring (SACM) Requirements", October 2014, Monitoring (SACM) Requirements", October 2014,
<https://tools.ietf.org/html/draft-ietf-sacm-requirements- <https://tools.ietf.org/html/draft-ietf-sacm-requirements-
02>. 02>.
Authors' Addresses Authors' Addresses
Eric Voit Eric Voit
Cisco Systems Cisco Systems
Email: evoit@cisco.com Email: evoit@cisco.com
Alexander Clemm
Alex Clemm
Cisco Systems Cisco Systems
Email: alex@cisco.com Email: alex@cisco.com
Alberto Gonzalez Prieto Alberto Gonzalez Prieto
Cisco Systems Cisco Systems
Email: albertgo@cisco.com Email: albertgo@cisco.com
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