I2RS working group J. Haas
Internet-Draft Juniper
Intended status: Standards Track S. Hares
Expires: January 7, 2017 Huawei
July 6, 2016
I2RS Ephemeral State Requirements
draft-ietf-i2rs-ephemeral-state-14
Abstract
This document covers requests to the NETMOD and NETCONF Working
Groups for functionality to support the ephemeral state requirements
to implement the I2RS architecture.
Status of This Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Review of Requirements from I2RS architecture document . . . 3
3. Ephemeral State Requirements . . . . . . . . . . . . . . . . 5
3.1. Persistence . . . . . . . . . . . . . . . . . . . . . . . 5
3.2. Constraints . . . . . . . . . . . . . . . . . . . . . . . 5
3.3. Hierarchy . . . . . . . . . . . . . . . . . . . . . . . . 6
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 . . . . . . . . . . . . . . . . . . . . . . . 7
8. Multiple Message Transactions . . . . . . . . . . . . . . . . 8
9. Pub/Sub Requirements Expanded for Ephemeral State . . . . . . 8
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
11. Security Considerations . . . . . . . . . . . . . . . . . . . 9
12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
13.1. Normative References: . . . . . . . . . . . . . . . . . 9
13.2. Informative References . . . . . . . . . . . . . . . . . 10
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 [I-D.ietf-i2rs-architecture] abstractly documents a number
of requirements for implementing the I2RS requirements. Section 2
reviews 10 key requirements related to ephemeral state.
The I2RS Working Group has chosen to use the YANG data modeling
language [RFC6020] 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.
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
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1. select features from YANG, NETCONF, and RESTCONF 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),
3. suggest protocol strawman (e.g.
[I-D.hares-i2rs-protocol-strawman]) as ideas for the NETCONF,
RESTCONF, and YANG changes.
The purpose of these requirements and the suggested protocol straw
man is to provide a quick turnaround on creating the I2RS protocol.
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. Sections 7 provide additional requirements that detail how
write-conflicts should be resolved if two I2RS client write the same
data. Section 8 provides an additional requirement that details on
I2RS support of multiple message transactions. Section 9 highlights
two requirements in the I2RS publication/subscription requirements
[I-D.ietf-i2rs-pub-sub-requirements] 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. Review of Requirements from I2RS architecture document
The I2RS architecture defines important high-level requirements for
the I2RS protocol. The following are ten requirements that
[I-D.ietf-i2rs-architecture] contains which provide context for the
ephemeral data state requirements given in sections 3-8:
1. The I2RS protocol SHOULD support highly reliable notifications
(but not perfectly reliable notifications) from an I2RS agent to
an I2RS client.
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2. The I2RS protocol SHOULD support a high bandwidth, asynchronous
interface, with real-time guarantees on getting data from an
I2RS agent by an I2RS client.
3. The I2RS protocol will operate on data models which MAY be
protocol independent or protocol dependent.
4. 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.
5. 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.
6. The Agent identity and the Client identity SHOULD be passed
outside of the I2RS protocol in a authentication and
authorization protocol (AAA). Client priority may be passed in
the AAA protocol. The values of identities are originally set
by operators, and not standardized.
7. An I2RS Client and I2RS Agent MUST mutually authenticate each
other based on pre-established authenticated identities.
8. Secondary identity data is read-only meta-data that is recorded
by the I2RS agent associated with a data model's node is
written, updated or deleted. Just like the primary identity,
the secondary identity SHOULD only be recorded when the data
node is written or updated or deleted
9. 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.
10. The I2RS protocol MUST support the use of a secure transport.
However, certain functions such as notifications MAY use a non-
secure transport. Each model or service (notification, logging)
must define within the model or service the valid uses of a non-
secure transport.
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3. Ephemeral State Requirements
In requirements Ephemeral-REQ-01 to Ephemeral-15, Ephemeral state is
defined as potentially including both ephemeral configured state and
operational state.
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 may have constraints that refer to
operational state, this includes potentially fast changing or short
lived operational state nodes, such as MPLS LSP-ID or a BGP IN-RIB.
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, logging, 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.
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3.3. Hierarchy
Ephemeral-REQ-06: The ability to:
1. to define a YANG module or submodule schema that only contains
data nodes with the property of being ephemeral, and
2. to augment a YANG data model with additional YANG schema nodes
that have the property of being ephemeral.
3.4. Ephemeral Configuration overlapping Local Configuration
Ephemeral-REQ-07: Ephemeral configuration state could override
overlapping local configuration state, or vice-versa.
Implementations MUST provide a mechanism to choose which takes
precedence. This mechanism MUST include local configuration (policy)
and MAY be provided via the I2RS protocol mechanisms.
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 to way to indicate, config false
YANG schema nodes that are writable operational state.
5. NETCONF Features for Ephemeral State
Ephemeral-REQ-09: The conceptual changes to NETCONF
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 in
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 in
requirements Ephemeral-REQ-11 through Ephemeral-REQ-14).
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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
is done via a priority mechanism with the highest priority winning.
This priority is per-client.
Ephemeral-REQ-11: The data nodes MAY store I2RS client identity and
not the effective priority at the time the data node is stored. Per
SEC-REQ-07 in section 3.1 of
[I-D.ietf-i2rs-protocol-security-requirements], an identifier must
have just one priority. Therefore, the data nodes MAY store I2RS
client identity and not the effective priority of the I2RS client at
the time the data node is stored. 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 clients are trying
to write the same data node, this collision is considered an error
and priorities were created to give a deterministic result. When
there is a collision, 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.
Note:RESTCONF and NETCONF posts can come in concurrently from
alternative sources (see ETag in [I-D.ietf-netconf-restconf] section
3.4.1.2 usage). Therefore the collision detection and comparison of
priority needs to occur both for both type of updates (POST or edit-
config) at the point of comparison.
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 is not mandating how AAA supports
priority. Mechanisms which 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.
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8. Multiple Message Transactions
Ephemeral-REQ-15: Section 7.9 of the [I-D.ietf-i2rs-architecture]
states the I2RS architecture does not include multi-message atomicity
and roll-back mechanisms. I2RS notes multiple operations in one or
more messages handling can handle errors within the set of operations
in many ways. No multi-message commands SHOULD cause errors to be
inserted 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
[I-D.ietf-i2rs-pub-sub-requirements], and the following general
requirements SHOULD be understood to be expanded to to include
ephemeral state:
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.
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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
o Kent Watsen
o Robert Wilton
13. References
13.1. Normative References:
[I-D.ietf-i2rs-architecture]
Atlas, A., Halpern, J., Hares, S., Ward, D., and T.
Nadeau, "An Architecture for the Interface to the Routing
System", draft-ietf-i2rs-architecture-15 (work in
progress), April 2016.
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[I-D.ietf-i2rs-protocol-security-requirements]
Hares, S., Migault, D., and J. Halpern, "I2RS Security
Related Requirements", draft-ietf-i2rs-protocol-security-
requirements-06 (work in progress), May 2016.
[I-D.ietf-i2rs-pub-sub-requirements]
Voit, E., Clemm, A., and A. Prieto, "Requirements for
Subscription to YANG Datastores", draft-ietf-i2rs-pub-sub-
requirements-09 (work in progress), May 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-01 (work in progress), April 2016.
[I-D.ietf-i2rs-traceability]
Clarke, J., Salgueiro, G., and C. Pignataro, "Interface to
the Routing System (I2RS) Traceability: Framework and
Information Model", draft-ietf-i2rs-traceability-11 (work
in progress), May 2016.
[I-D.ietf-netconf-restconf]
Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
Protocol", draft-ietf-netconf-restconf-14 (work in
progress), June 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>.
13.2. Informative References
[I-D.hares-i2rs-protocol-strawman]
Hares, S., Bierman, A., and a. amit.dass@ericsson.com,
"I2RS protocol strawman", draft-hares-i2rs-protocol-
strawman-02 (work in progress), May 2016.
[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>.
[RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for
the Network Configuration Protocol (NETCONF)", RFC 6020,
DOI 10.17487/RFC6020, October 2010,
<http://www.rfc-editor.org/info/rfc6020>.
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Authors' Addresses
Jeff Haas
Juniper
Email: jhaas@juniper.net
Susan Hares
Huawei
Saline
US
Email: shares@ndzh.com
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