One document matched: draft-ietf-i2rs-ephemeral-state-21.xml
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<rfc category="info" docName="draft-ietf-i2rs-ephemeral-state-21.txt" ipr="trust200902">
<front>
<title abbrev="I2RS Ephemeral State Requirements">I2RS Ephemeral State Requirements </title>
<author fullname="Jeff Haas" initials="J." surname="Haas">
<organization>Juniper</organization>
<address>
<postal>
<street></street>
<city> </city>
<country></country>
</postal>
<email>jhaas@juniper.net</email>
</address>
</author>
<author fullname="Susan Hares" initials="S." surname="Hares">
<organization> Huawei </organization>
<address>
<postal>
<street></street>
<city>Saline</city>
<country>US</country>
</postal>
<email>shares@ndzh.com </email>
</address>
</author>
<date year="2016" />
<area>Routing Area</area>
<workgroup>I2RS working group</workgroup>
<keyword>RFC</keyword>
<keyword>Request for Comments</keyword>
<keyword>I-D</keyword>
<keyword>Internet-Draft</keyword>
<keyword>I2RS</keyword>
<abstract>
<t>
The I2RS (interface to the routing system) Architecture document (RFC7921)
abstractly describes a number of requirements for ephemeral state
(in terms of capabilities and behaviors) which any protocol suite
attempting to meet the needs of I2RS has to provide.
This document describes, in detail, requirements for ephemeral
state for those implementing the I2RS protocol.
</t>
</abstract>
</front>
<middle>
<section anchor="intro" title="Introduction">
<t>The Interface to the Routing System (I2RS) Working Group is chartered
with providing architecture and mechanisms to inject into and
retrieve information from the routing system. The I2RS Architecture
document <xref target="RFC7921"></xref> abstractly documents a number
of requirements for implementing the I2RS requirements.
Section 2 reviews key requirements related to ephemeral state.
<xref target="RFC7921"></xref> defines ephemeral state as "state
which does not survive the reboot of a routing device or the reboot
of the software handling the I2RS software on a routing device"
(see section 1.1 of <xref target="RFC7921"></xref>).
</t>
<t>
The I2RS Working Group has chosen to use the YANG data modeling
language <xref target="RFC7950"></xref> as the basis to implement its mechanisms.
</t>
<t>
Additionally, the I2RS Working group has chosen to re-use two existing protocols,
NETCONF <xref target="RFC6241"></xref> and its similar but lighter-weight relative RESTCONF
<xref target="I-D.ietf-netconf-restconf"></xref>, as the protocols for carrying I2RS.
</t>
<t>What does re-use of a protocol mean? Re-use means that while YANG, NETCONF and RESTCONF
are a good starting basis for the I2RS protocol, the creation of the I2RS protocol implementations
requires that the I2RS requirements
<list style="numbers">
<t>select features from YANG, NETCONF, and RESTCONF per version of the I2RS protocol
(See sections 4, 5, and 6)
</t>
<t>propose additions to YANG, NETCONF, and RESTCONF per version of the I2RS protocol
for key functions (ephemeral state, protocol security, publication/subscription service,
traceability), </t>
</list>
The purpose of these requirements is to ensure clarity during I2RS protocol creation.
</t>
<t>Support for ephemeral state is an I2RS protocol requirement that requires datastore
changes (see section 3), YANG additions (see section 4), NETCONF additions (see section 5),
and RESTCONF additions (see section 6).
</t>
<t> Sections 7-9 provide details that expand upon the changes in
sections 3-6 to clarify requirements discussed by the I2RS and NETCONF working groups.
Section 7 provided additional requirements that detail how write-conflicts
should be resolved if two I2RS client write the same data.
Section 8 describes I2RS requirements for support of multiple message transactions.
Section 9 highlights two requirements in the I2RS publication/subscription requirements
<xref target="RFC7923"></xref> that must be expanded for
ephemeral state.
</t>
<section title="Requirements Language">
<t>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 <xref target="RFC2119">RFC 2119</xref>.</t>
</section>
</section>
<section title="Review of Requirements from I2RS architecture document">
<t> The I2RS architecture defines important high-level requirements for
the I2RS protocol. The following are requirements distilled from
<xref target="RFC7921"></xref>
that provide context for the ephemeral data state requirements
given in sections 3-8:
<list style="numbers">
<t>The I2RS protocol SHOULD support an interface asynchronous programmatic interface
interface with properties of described in section 5 of <xref target="RFC7920"></xref>
(e.g. high throughput) with support for target information streams,
filtered evens, and thresholded events (real-time events) sent by an I2RS agent to
an I2RS Client (Key points from section 1.1 of <xref target="RFC7921"></xref>). </t>
<t> I2RS agent MUST record the client identity when a node is created or modified.
The I2RS agent SHOULD to be able to read the client identity of a node and
use the client identity's associated priority to resolve conflicts.
The secondary identity is useful for traceability and may also be recorded.
(Key points from section 4 of <xref target="RFC7921"></xref>.)
</t>
<t>An I2RS Client identity MUST have only one priority for the client's identifier. A
collision on writes is considered an error, but the priority associated
with each client identifier is utilized to compare
requests from two different clients in order to modify an existing
node entry. Only an entry from a client which is higher priority can modify
an existing entry (First entry wins). Priority only has meaning at the time
of use. (Key points from section 7.8 of <xref target="RFC7921"></xref>.)
</t>
<t>I2RS Client's secondary identity data is read-only meta-data that is recorded by the
I2RS agent associated with a data model's node is written.
Just like the primary client identity, the secondary identity SHOULD
only be recorded when the data node is written.
(Key points from sections 7.4 of <xref target="RFC7921"></xref>.)</t>
<t>I2RS agent MAY have a lower priority I2RS client attempting to modify
a higher priority client's entry in a data model. The filtering out of
lower priority clients attempting to write or modify a higher priority
client's entry in a data model SHOULD be effectively handled and not put an
undue strain on the I2RS agent.
(See section 7.8 of <xref target="RFC7921"></xref> augmented by the resource limitation
language in section 8 <xref target="RFC7921"></xref>.)
</t>
</list>
</t>
</section>
<section title="Ephemeral State Requirements">
<t>
In requirements Ephemeral-REQ-01 to Ephemeral-REQ-15, Ephemeral state
is defined as potentially including in a data model
ephemeral configuration and operational state which is flagged as
ephemeral.
</t>
<section title="Persistence">
<t> Ephemeral-REQ-01: I2RS requires ephemeral state; i.e. state that does not persist
across reboots. If state must be restored, it should be done solely
by replay actions from the I2RS client via the I2RS agent.
</t>
<t>While at first glance this may seem equivalent to the writable-
running data store in NETCONF, running-config can be copied to a
persistent data store, like startup config. I2RS ephemeral state
MUST NOT be persisted.
</t>
</section>
<section title="Constraints">
<t>Ephemeral-REQ-02: Non-ephemeral state MUST NOT refer to
ephemeral state for constraint purposes;
it SHALL be considered a validation error if it does. </t>
<t>Ephemeral-REQ-03: Ephemeral state MUST be able to have constraints that refer
to operational state, this includes potentially fast changing or
short lived operational state nodes, such as MPLS LSP-ID (label switched path ID)
or a BGP Adj-RIB-IN (Adjacent RIB Inboud). Ephemeral state constraints
should be assessed when the ephemeral state is written, and if
any of the constraints change to make the constraints invalid
after that time the I2RS agent SHOULD notify the I2RS client.
</t>
<t>Ephemeral-REQ-04: Ephemeral state MUST be able to refer to non-ephemeral state
as a constraint. Non-ephemeral state can be configuration state or operational state.
</t>
<t>Ephemeral-REQ-05: I2RS pub-sub <xref target="RFC7923"></xref>, tracing <xref target="RFC7922"></xref>,
RPC or other mechanisms may lead to undesirable
or unsustainable resource consumption on a system implementing an I2RS agent.
It is RECOMMENDED that mechanisms be made available to permit
prioritization of I2RS operations, when appropriate, to permit
implementations to shed work load when operating under constrained
resources. An example of such a work shedding mechanism is rate-limiting.
</t>
</section>
<section title="Hierarchy">
<t>
Ephemeral-REQ-06: YANG MUST have the ability to do the following:
<list style="numbers">
<t>to define a YANG module or submodule schema that
only contains data nodes with the property of being ephemeral, and
</t>
<t>to augment a YANG model with additional YANG
schema nodes that have the property of being ephemeral.
</t>
</list>
</t>
</section>
<section title="Ephemeral Configuration overlapping Local Configuration">
<t>
Ephemeral-REQ-07: Local configuration MUST have a priority that is comparable
with individual I2RS client priorities for making changes. This
priority will determine whether local configuration changes or
individual ephemeral configuration changes take precedence as described in
RFC7921. The I2RS protocol MUST support this mechanism.
</t>
</section>
</section>
<section title="YANG Features for Ephemeral State">
<t>Ephemeral-REQ-08:In addition to config true/false, there MUST be a
way to indicate that YANG schema nodes represent ephemeral state.
It is desirable to allow for, and have a way to indicate, config
false YANG schema nodes that are writable operational state.
</t>
</section>
<section title="NETCONF Features for Ephemeral State">
<t>
Ephemeral-REQ-09: The changes to NETCONF must include:
<list style="numbers">
<t>Support for communication mechanisms to enable an I2RS client to
determine that an I2RS agent supports the mechanisms needed for I2RS operation.
</t>
<t>The ephemeral state MUST support notification
of write conflicts using the priority requirements
defined in section 7 below (see requirements Ephemeral-REQ-11 through Ephemeral-REQ-14).
</t>
</list>
</t>
</section>
<section title="RESTCONF Features for Ephemeral State">
<t>Ephemeral-REQ-10: The conceptual changes to RESTCONF are:
<list style="numbers">
<t>Support for communication mechanisms to enable an I2RS client to
determine that an I2RS agent supports the mechanisms needed for I2RS operation.
</t>
<t>The ephemeral state must support notification
of write conflicts using the priority requirements
defined in section 7 below (see requirements Ephemeral-REQ-11 through Ephemeral-REQ-14).
</t>
</list>
</t>
</section>
<section title="Requirements regarding Supporting Multi-Head Control via client Priority">
<t> To support Multi-Headed Control, I2RS requires that there be a
decidable means of arbitrating the correct state of data when
multiple clients attempt to manipulate the same piece of data. This
is done via a priority mechanism with the highest priority winning.
This priority is per-client.
</t>
<t>Ephemeral-REQ-11: The following requirements must be
supported by the I2RS protocol I2RS Protocol (e.g. NETCONF/RESTCONF + yang)
in order to support I2RS client identity and priority:
<list style="symbols">
<t>the data nodes MAY store I2RS client identity and not
the effective priority at the time the data node is stored.
</t>
<t>Per SEC-REQ-07 in section 4.3 of <xref target="I-D.ietf-i2rs-protocol-security-requirements"></xref>,
an I2RS Identifier MUST have just one priority.
The I2RS protocol MUST support the ability to have data nodes
store I2RS client identity and not the effective priority
of the I2RS client at the time the data node is stored.
</t>
<t> The priority MAY be
dynamically changed by AAA, but the exact actions
are part of the protocol definition as long as collisions are handled
as described in Ephemeral-REQ-12, Ephemeral-REQ-13, and Ephemeral-REQ-14.
</t>
</list>
</t>
<t>Ephemeral-REQ-12: When a collision occurs as two I2RS clients are trying
to write the same data node, this collision is considered an error. The
I2RS priorities are used to provide a deterministic resolution to the conflict.
When there is a collision, and the data node is changed,
a notification (which includes indicating data
node the collision occurred on) MUST BE sent to the original client
to give the original client a chance to deal with the issues
surrounding the collision. The original client may need to fix their
state.
</t>
<t>Explanation: RESTCONF and NETCONF updates can come in concurrently from alternative sources.
Therefore the collision detection and comparison of priority needs to occur for any type of update.
</t>
<t>For example, RESTCONF tracks the source of configuration change via the
entity-Tag (section 3.5.2 of <xref target="I-D.ietf-netconf-restconf"></xref>)
which the server returns to the client along with the value in GET or HEAD methods.
RESTCONF requires that this resource entity-tag be updated whenever a resource or
configuration resource within the resource is altered. In the RESTCONF processing,
when the resource or a configuration resource within the resource is altered, then
the processing of the configuration change for two I2RS clients must detect an
I2RS collision and resolve the collision using the priority mechanism.
</t>
<t>Ephemeral-REQ-13: Multi-headed control is required for collisions and the priority
resolution of collisions. Multi-headed control is not tied to
ephemeral state. I2RS protocol MUST NOT mandate the internal mechanism for how AAA protocols
(E.g. Radius or Diameter) or mechanisms distribute priority per identity except that
any AAA protocols MUST operate over a secure transport layer (See Radius <xref target="RFC6614"></xref>
and Diameter <xref target="RFC6733"></xref>. Mechanisms that prevent collisions of
two clients trying to modify the same node of data are the focus.
</t>
<t>Ephemeral-REQ-14: A deterministic conflict resolution mechanism MUST
be provided to handle the error scenario that two clients, with
the same priority, update the same configuration data node. The I2RS
architecture gives one way that this could be achieved, by
specifying that the first update wins. Other solutions, that prevent
oscillation of the config data node, are also acceptable.
</t>
</section>
<section title="Multiple Message Transactions">
<t> Ephemeral-REQ-15: Section 7.9 of
the <xref target="RFC7921"></xref>
states the I2RS architecture does not include
multi-message atomicity and roll-back mechanisms.
The I2RS protocol implementation MUST NOT require the support of these features.
As part of this requirement, the I2RS protocol should support:
<list>
<t>multiple operations in one messge; an error in one operation
MUST NOT stop additional operations from being carried out nor
can it cause previous operations to be rolled back. </t>
<t>multiple operations in multiple messages, but
multiple message commands error handling MUST NOT
insert errors into the I2RS ephemeral state.
</t>
</list>
</t>
</section>
<section title="Pub/Sub Requirements Expanded for Ephemeral State">
<t>
I2RS clients require the ability to monitor changes to ephemeral
state. While subscriptions are well defined for receiving
notifications, the need to create a notification set for all
ephemeral configuration state may be overly burdensome to the user.
</t>
<t>
There is thus a need for a general subscription mechanism that can
provide notification of changed state, with sufficient information to
permit the client to retrieve the impacted nodes. This should be
doable without requiring the notifications to be created as part of
every single I2RS module.
</t>
<t>The publication/subscription requirements for I2RS are in
<xref target="RFC7923"></xref>, and the
following general requirements SHOULD be understood to be expanded to
include ephemeral state:
<list style="symbols">
<t>Pub-Sub-REQ-01: The Subscription Service MUST support
subscriptions against ephemeral state in operational data stores, configuration data stores or both.
</t>
<t> Pub-Sub-REQ-02: The Subscription Service MUST support filtering
so that subscribed updates under a target node might publish only
ephemeral state in operational data or configuration data, or publish both
ephemeral and operational data.
</t>
<t>Pub-Sub-REQ-03: The subscription service MUST support subscriptions which are ephemeral.
(E.g. An ephemeral data model which has ephemeral subscriptions.)
</t>
</list>
</t>
</section>
<section anchor="IANA" title="IANA Considerations">
<t>There are no IANA requirements for this document.</t>
</section>
<section title="Security Considerations">
<t>The security requirements for the I2RS protocol are
covered in <xref target="I-D.ietf-i2rs-protocol-security-requirements"></xref> document.
The security requirements for the I2RS protocol environment are in
<xref target="I-D.ietf-i2rs-security-environment-reqs"></xref>.
</t>
</section>
<section anchor="Acknowledgements" title="Acknowledgements">
<t>
This document is an attempt to distill lengthy conversations on
the I2RS mailing list for an architecture that was for a long
period of time a moving target. Some individuals in particular
warrant specific mention for their extensive help in providing
the basis for this document:
</t>
<t>
<list style="symbols">
<t>Alia Atlas,</t>
<t>Andy Bierman,</t>
<t>Martin Bjorklund,</t>
<t>Dean Bogdanavich,</t>
<t>Rex Fernando,</t>
<t>Joel Halpern,</t>
<t>Thomas Nadeau,</t>
<t>Juergen Schoenwaelder,</t>
<t>Kent Watsen,</t>
<t>Robert Wilton, and</t>
<t>Joe Clarke,</t>
</list>
</t>
</section>
</middle>
<back>
<references title="Normative References:">
&RFC6241;
&I-D.ietf-netconf-restconf;
&RFC6614;
&RFC6733;
&RFC7920;
&RFC7921;
&RFC7922;
&RFC7923;
&RFC7950;
&I-D.ietf-i2rs-protocol-security-requirements;
&I-D.ietf-i2rs-security-environment-reqs;
</references>
<references title="Informative References">
&RFC2119;
&I-D.hares-i2rs-protocol-strawman;
</references>
</back>
</rfc>| PAFTECH AB 2003-2026 | 2026-04-23 20:44:09 |