Internet DRAFT - draft-ietf-i2rs-ephemeral-state
draft-ietf-i2rs-ephemeral-state
I2RS working group J. Haas
Internet-Draft Juniper
Intended status: Informational S. Hares
Expires: May 20, 2017 Huawei
November 16, 2016
I2RS Ephemeral State Requirements
draft-ietf-i2rs-ephemeral-state-23.txt
Abstract
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.
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
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This Internet-Draft will expire on May 20, 2017.
Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the
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include Simplified BSD License text as described in Section 4.e of
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Architectural Requirements for Ephemeral State . . . . . . . 3
3. Ephemeral State Requirements . . . . . . . . . . . . . . . . 4
3.1. Persistence . . . . . . . . . . . . . . . . . . . . . . . 5
3.2. Constraints . . . . . . . . . . . . . . . . . . . . . . . 5
3.3. Hierarchy . . . . . . . . . . . . . . . . . . . . . . . . 5
3.4. Ephemeral Configuration overlapping Local Configuration . 6
4. YANG Features for Ephemeral State . . . . . . . . . . . . . . 6
5. NETCONF Features for Ephemeral State . . . . . . . . . . . . 6
6. RESTCONF Features for Ephemeral State . . . . . . . . . . . . 6
7. Requirements regarding Supporting Multi-Head Control via
client Priority . . . . . . . . . . . . . . . . . . . . . . . 6
8. Multiple Message Transactions . . . . . . . . . . . . . . . . 8
9. Pub/Sub Requirements Expanded for Ephemeral State . . . . . . 8
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
11. Security Considerations . . . . . . . . . . . . . . . . . . . 9
12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
13.1. Normative References: . . . . . . . . . . . . . . . . . 10
13.2. Informative References . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
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 [RFC7921] abstractly documents a number of requirements for
implementing the I2RS, and 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 [RFC7921]). Section 2 describes the specific requirements
which the I2RS working group has identified based on the I2RS
architecture's abstract requirements.
The I2RS Working Group has chosen to use the YANG data modeling
language [RFC7950] as the basis to implement its mechanisms.
Additionally, the I2RS Working group has chosen to re-use two
existing protocols, NETCONF [RFC6241] and its similar but lighter-
weight relative RESTCONF [I-D.ietf-netconf-restconf], as the
protocols for carrying I2RS.
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What does re-use of a protocol mean? Re-use means that while the
combination of the YANG modeling language, and the NETCONF and
RESTCONF protocols is a good starting basis for the I2RS data
modeling language and protocol, the creation of I2RS protocol
implementations requires that the I2RS requirements:
1. select features from the YANG modeling language, and the NETCONF
and RESTCONF protocols per version of the I2RS protocol (See
sections 4, 5, and 6)
2. propose additions to YANG, NETCONF, and RESTCONF per version of
the I2RS protocol for key functions (ephemeral state, protocol
security, publication/subscription service, traceability),
The purpose of these requirements is to ensure clarity during I2RS
protocol creation.
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).
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 provides 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 [RFC7923] that must be
expanded for ephemeral state.
1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
2. Architectural Requirements for Ephemeral State
The I2RS architecture [RFC7921] and the I2RS problem statement
[RFC7920] define the important high-level requirements for the I2RS
protocol in abstract terms. This section distills this high level
abstract guidance into specific requirements for the I2RS protocol.
To aid the reader, there are references back to the abstract
descriptions in the I2RS architecture document and the I2RS problem
statement, but the reader should note the requirements below are not
explicitly stated in the I2RS architecture document [RFC7921] or in
the I2RS problem statement [RFC7920]/
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Requirements:
1. The I2RS protocol SHOULD support an asynchronous programmatic
interface with properties of described in section 5 of [RFC7920]
(e.g. high throughput) with support for target information
streams, filtered events, and thresholded events (real-time
events) sent by an I2RS agent to an I2RS client (from section 1.1
of [RFC7921]).
2. 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. (from section 4 of
[RFC7921].)
3. 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. (from
section 7.8 of [RFC7921].)
4. 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.
(from sections 7.4 of [RFC7921].)
5. 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 [RFC7921] augmented by the resource
limitation language in section 8 [RFC7921].)
3. Ephemeral State Requirements
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.
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3.1. Persistence
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.
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.
3.2. Constraints
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.
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.
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.
Ephemeral-REQ-05: I2RS pub-sub [RFC7923], tracing [RFC7922], 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.
3.3. Hierarchy
Ephemeral-REQ-06: YANG MUST have the ability to do the following:
1. to define a YANG module or submodule schema that only contains
data nodes with the property of being ephemeral, and
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2. to augment a YANG model with additional YANG schema nodes that
have the property of being ephemeral.
3.4. Ephemeral Configuration overlapping Local Configuration
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.
4. YANG Features for Ephemeral State
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.
5. NETCONF Features for Ephemeral State
Ephemeral-REQ-09: The changes to NETCONF must include:
1. Support for communication mechanisms to enable an I2RS client to
determine that an I2RS agent supports the mechanisms needed for
I2RS operation.
2. 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).
6. RESTCONF Features for Ephemeral State
Ephemeral-REQ-10: The conceptual changes to RESTCONF are:
1. Support for communication mechanisms to enable an I2RS client to
determine that an I2RS agent supports the mechanisms needed for
I2RS operation.
2. 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).
7. Requirements regarding Supporting Multi-Head Control via client
Priority
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
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is done via a priority mechanism with the highest priority winning.
This priority is per-client.
Ephemeral-REQ-11: The following requirements must be supported by the
I2RS protocol in order to support I2RS client identity and priority:
o the data nodes MUST store I2RS client identity and MAY store the
effective priority at the time the data node is stored.
o Per SEC-REQ-07 in section 4.3 of
[I-D.ietf-i2rs-protocol-security-requirements], 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.
o 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.
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.
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.
For example, RESTCONF tracks the source of configuration change via
the entity-Tag (section 3.5.2 of [I-D.ietf-netconf-restconf]) 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.
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
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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
[RFC6614] and Diameter [RFC6733]. Mechanisms that prevent collisions
of two clients trying to modify the same node of data are the focus.
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.
8. Multiple Message Transactions
Ephemeral-REQ-15: Section 7.9 of the [RFC7921] 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:
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.
multiple operations in multiple messages, but multiple message
commands error handling MUST NOT insert errors into the I2RS
ephemeral state.
9. Pub/Sub Requirements Expanded for Ephemeral State
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.
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.
The publication/subscription requirements for I2RS are in [RFC7923],
and the following general requirements SHOULD be understood to be
expanded to include ephemeral state:
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o Pub-Sub-REQ-01: The Subscription Service MUST support
subscriptions against ephemeral state in operational data stores,
configuration data stores or both.
o 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.
o Pub-Sub-REQ-03: The subscription service MUST support
subscriptions which are ephemeral. (E.g. An ephemeral data model
which has ephemeral subscriptions.)
10. IANA Considerations
There are no IANA requirements for this document.
11. Security Considerations
The security requirements for the I2RS protocol are covered in
[I-D.ietf-i2rs-protocol-security-requirements] document. The
security requirements for the I2RS protocol environment are in
[I-D.ietf-i2rs-security-environment-reqs].
12. Acknowledgements
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:
o Alia Atlas,
o Andy Bierman,
o Martin Bjorklund,
o Dean Bogdanavich,
o Rex Fernando,
o Joel Halpern,
o Thomas Nadeau,
o Juergen Schoenwaelder,
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o Kent Watsen,
o Robert Wilton, and
o Joe Clarke,
13. References
13.1. Normative References:
[I-D.ietf-i2rs-protocol-security-requirements]
Hares, S., Migault, D., and J. Halpern, "I2RS Security
Related Requirements", draft-ietf-i2rs-protocol-security-
requirements-17 (work in progress), September 2016.
[I-D.ietf-i2rs-security-environment-reqs]
Migault, D., Halpern, J., and S. Hares, "I2RS Environment
Security Requirements", draft-ietf-i2rs-security-
environment-reqs-02 (work in progress), November 2016.
[I-D.ietf-netconf-restconf]
Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
Protocol", draft-ietf-netconf-restconf-18 (work in
progress), October 2016.
[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,
<http://www.rfc-editor.org/info/rfc6241>.
[RFC6614] Winter, S., McCauley, M., Venaas, S., and K. Wierenga,
"Transport Layer Security (TLS) Encryption for RADIUS",
RFC 6614, DOI 10.17487/RFC6614, May 2012,
<http://www.rfc-editor.org/info/rfc6614>.
[RFC6733] Fajardo, V., Ed., Arkko, J., Loughney, J., and G. Zorn,
Ed., "Diameter Base Protocol", RFC 6733,
DOI 10.17487/RFC6733, October 2012,
<http://www.rfc-editor.org/info/rfc6733>.
[RFC7920] Atlas, A., Ed., Nadeau, T., Ed., and D. Ward, "Problem
Statement for the Interface to the Routing System",
RFC 7920, DOI 10.17487/RFC7920, June 2016,
<http://www.rfc-editor.org/info/rfc7920>.
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[RFC7921] Atlas, A., Halpern, J., Hares, S., Ward, D., and T.
Nadeau, "An Architecture for the Interface to the Routing
System", RFC 7921, DOI 10.17487/RFC7921, June 2016,
<http://www.rfc-editor.org/info/rfc7921>.
[RFC7922] Clarke, J., Salgueiro, G., and C. Pignataro, "Interface to
the Routing System (I2RS) Traceability: Framework and
Information Model", RFC 7922, DOI 10.17487/RFC7922, June
2016, <http://www.rfc-editor.org/info/rfc7922>.
[RFC7923] Voit, E., Clemm, A., and A. Gonzalez Prieto, "Requirements
for Subscription to YANG Datastores", RFC 7923,
DOI 10.17487/RFC7923, June 2016,
<http://www.rfc-editor.org/info/rfc7923>.
[RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
RFC 7950, DOI 10.17487/RFC7950, August 2016,
<http://www.rfc-editor.org/info/rfc7950>.
13.2. Informative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
Authors' Addresses
Jeff Haas
Juniper
Email: jhaas@juniper.net
Susan Hares
Huawei
Saline
US
Email: shares@ndzh.com
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