I2RS working group                                               J. Haas
Internet-Draft                                                   Juniper
Intended status: Standards Track                                S. Hares
Expires: November 6, 26, 2016                                        Huawei
                                                            May 5, 25, 2016

                   I2RS Ephemeral State Requirements
                   draft-ietf-i2rs-ephemeral-state-06
                   draft-ietf-i2rs-ephemeral-state-07

Abstract

   This document covers requests to the netmod NETMOD and netconf NETCONF Working
   Groups for functionality to support the ephemeral state requirements
   to implement the I2RS architecture.

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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  . . . . . . . . . . . . . . . .   4   5
     3.1.  Persistence . . . . . . . . . . . . . . . . . . . . . . .   4   5
     3.2.  Constraints . . . . . . . . . . . . . . . . . . . . . . .   4   5
     3.3.  Hierarchy . . . . . . . . . . . . . . . . . . . . . . . .   5
     3.4.  Changes to
   4.  YANG . . . . . . . . . . . . . . . . . . . . .   5
       3.4.1.  Suggested Yang syntax changes . . . . . . . . . . . . Features for Ephemeral State for I2RS Protocol version 1   5
     3.5.  Minimal Changes to
   5.  NETCONF Features for Ephemeral State for I2RS Protocol
       version 1 .   6
       3.5.1.  Dependencies  . . . . . . . . . . . . . . . . . . . .   7
       3.5.2.  Modified operations . . . . . . . . . . . . . . . . .   7
       3.5.3.  Unsupported operations  . . . . . . . . . . . . . . .   7
       3.5.4.  Interactions with existing capabilities . . . . . . .   7
     3.6.  Changes to   6
   6.  RESTCONF Features for Ephemeral State . . . . . . . . .   7
       3.6.1.  dependencies for RESTCONF . . . . . . . . . . . . I2RS Protocol
       version 1 . .   8
       3.6.2.  modification to context . . . . . . . . . . . . . . .   9
       3.6.3.  modification to existing operations . . . . . . . . .   9
     3.7.   7
   7.  Requirements regarding Identity, Secondary-Identity and Supporting Multi-Head Control via
       Client Priority . . . . . . . . . . . . . . . . . . . . . . . .   9
       3.7.1.  Identity Requirements . . . . . . . . . . . . . . . .   9
       3.7.2.  Priority Requirements . . . . . . . . . . . . . . . .   9
       3.7.3.
   8.  Multiple Message Transactions . . . . . . . . . . . . . . . . . . . .  10
       3.7.4.  Subscriptions to Changed State
   9.  Pub/Sub Requirements Expanded for Ephemeral State . . . . .  11
   4.  Previously Considered Ideas . . . . .  11
   10. IANA Considerations . . . . . . . . . . . .  12
     4.1.  A Separate Ephemeral Data store . . . . . . . . .  11
   11. Security Considerations . . . .  12
     4.2.  Panes of Glass/Overlay . . . . . . . . . . . . . . .  11
   12. Acknowledgements  . .  13
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . .  11
   13. References  .  13
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  13
   7.  Acknowledgements . . . . .  12
     13.1.  Normative References:  . . . . . . . . . . . . . . . . .  13
   8.  12
     13.2.  Informative References . . . . . . . . . . . . . . . . . . . . . . . . .  14
     8.1.  Normative References: . . . . . . . .
   Authors' Addresses  . . . . . . . . . .  14
     8.2.  Informative References . . . . . . . . . . . . . . . . .  15
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  16  14

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 use the re-use two
   existing protocols, NETCONF [RFC6241] and its similar but lighter-weight lighter-
   weight relative RESTCONF
   [I-D.ietf-netconf-restconf] [I-D.ietf-netconf-restconf], as the
   protocols for carrying I2RS.

   While

   What does re-use of a protocol mean?  Re-use means that while YANG,
   NETCONF and RESTCONF are a good starting basis for I2RS,
   there are some things needed the I2RS protocol,
   the creation of the I2RS protocol implementations requires that the
   I2RS requirements
   1.  select features from each YANG, NETCONF, and RESTCONF per version of them in order
       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 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 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 implemented. 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 are important high level requirements: 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.

   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 MAY be
        protocol independent or protocol dependent.

   4.   I2RS Agent needs to MUST record the client identity when a node is
        created or modified.  The I2RS Agent needs 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 will MUST have only one priority for the client
        identity. client's
        identifer.  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 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 is SHOULD only be recorded when the data
        node is written or updated or deleted

   9.   I2RS agent can 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.  Note: Jeff's suggests that priority is kept at the NACM
        ([RFC6536])at the client level (rather than the path level or
        the group level) will allow these lower priority clients to be
        filtered out using an extended NACM approach.  This is only a
        suggestion of a method to provide the requirement 9.

   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.

3.  Ephemeral State Requirements

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 utilized temporary
   operational state (e.g.  MPLS LSP-ID or a BGP IN-RIB) as a
   constraints.

   Ephemeral-REQ-04: Ephemeral state MAY refer to non-ephemeral state
   for purposes of implementing constraints.  The designer of ephemeral
   state modules are advised that such constraints may impact the speed
   of processing ephemeral state commits and should avoid them when
   speed is essential.

3.3.  Hierarchy

   Ephemeral-REQ-05: The ability to add on augment an object (or a hierarchy of
   objects) with appropriate
   YANG structures that have the property of being ephemeral.

3.4.  Changes to  An object
   defined as Yang module, schema tree, a schema node, submodule or
   components of a submodule (derived types, groupings, data node, RPCs,
   actions, and notifications".

4.  YANG Features for Ephemeral State for I2RS Protocol version 1

   Ephemeral-REQ-06: Yang MUST have a way to indicate in a data model
   that nodes have the following properties: ephemeral, writable/not-
   writable, status/configuration, and secure/non-secure transport.

3.4.1.  Suggested Yang syntax changes

   The minimal changes to Yang are:

   1.  protocol version support - "I2RS version 1",

   2.  ephemeral true; (key word)

   3.  data models indicate which component protocol is supported
       "NETCONF", "RESTCONF"

   4.  encoding support - XML or JSON

   5.  data models indicate which transports protocol supported:"SSH",
       "TLS", "TCP" (nonsecure);

   6.  configuration for non-secure transport

       1.  i2rs-transport-non-secure ok;

   7.  Configuration for no validation checks: ephemeral-validation no
       check;

       1.  The key word "no-check" implies the I2RS client has done all
           the validation and the I2RS agent is only validating the
           message context.  The risk in this validation method

       2.  the key word "full" implies the I2RS Client is doing all
           validation normally done for a configuration node.

   8.  These key words can apply to ephemeral leafs, ephemeral sub-
       modules, ephemeral modules, and rpc allowing flexible validation
       levels.  This validation level can also be set on an rpc command
       (e.g. rpc for creating a new route in the I2RS RIB).  The default  (If
   you desire examples, please see [I-D.hares-i2rs-protocol-strawman]
   for all I2RS ephemeral writes is full.

   9.  Note: Anything less than full validation runs the risk of having
       bad data in the I2RS ephemeral state.

3.5.  Minimal Changes to potential yang syntax).

5.  NETCONF Features for Ephemeral State for I2RS Protocol version 1

   Ephemeral-REQ-07: The conceptual changes to NETCONF

   o

   1.  protocol version support for I2RS modifications - "I2RS-version 1",

   o (e.g.  I2RS
       version 1)

   2.  support for ephemeral model scope indication - ephemeral modules, which indicates
       whether a module is an ephemeral-only module, mixed config module
       (ephemeral and config), mixed derived state (ephemeral and
       config).

   o

   3.  multiple message support - supports the I2RS "all or nothing",

   o  pane of glass nothing"
       concept ([I-D.ietf-i2rs-architecture] section 7.9) which is the
       same as NETCONF "roll-back-on-error".

   4.  support - single ephemeral pane only.

   o for the following transports protocol support - supported: "TCP",
       "SSH", "TLS", and non-secure transport (see
       [I-D.ietf-i2rs-protocol-security-requirements] section 3.2 in
       requirements SEC-REQ-09 and SEC-REQ-11 for details).  NETCONF [RFC6241], yang pub-sub push
      [I-D.ietf-netconf-yang-push], yang module library
      [I-D.ietf-netconf-yang-library], call-home
      [I-D.ietf-netconf-call-home], and server modules
      [I-D.ietf-netconf-server-model] (server module must
       should be augmented able to support mutual authentication).

   o  encoding support - XML or JSON

   o  transports protocol supported: "TCP", "SSH", "TLS", non-secure,
      and others.

   o expand the number of secure transport protocols
       supported as I2RS may add additional transport protocols.

   5.  ability to select transports restrict insecure transport support to specific
       portions of a data model available for management models marked as valid to transfer via
       insecure protocol.  Insecure portions must

   6.  ephemeral state overwriting of configuration state MUST be able
       controlled by the following policy knobs (as defined by
       [I-D.ietf-i2rs-architecture] section 6.3 and 6.3.1):

       *  ephemeral configuration overwrites local configuration (true/
          false; normal value: true), and

       *  Update of local configuration value supercedes and overwrites
          the ephemeral configuration (true/false; normal value: false).

   7.  The ephemeral overwriting to select a insecure
      transport.

   o  yang modules syntax changes local configuration described in section 3.4.

3.5.1.  Dependencies

   1.  Yang data models, sub-modules, or modules must (8)
       above is considered to be flagged with the composite of all ephemeral data store flag,

   2.  Yang modules values
       by all clients.  Some may consider this approach as a single pane
       of glass for ephemeral state.

   8.  The ephemeral state must support notification of write conflicts.

   3.  yang modules syntax changes described conflicts
       using the priority requirements defined in section 3.4.

   4.  Yang modules must support the following NETCONF/RESTCONF
       features:

       1.  The yang module library feature
           [I-D.ietf-netconf-yang-library],

       2.  Publication-Subscription model found 3.7 below in
           [I-D.ietf-netconf-yang-push]

       3.  Server initiated connection to a client
           [I-D.ietf-netconf-call-home]

       4.  data models to configure RESTCONF/NETCONF servers
           [I-D.ietf-netconf-server-model],

3.5.2.  Modified operations

   <get-config>, <edit-config> <copy-config>, <delete-config> <get>
   <close-session>, <kill-session> are altered to abide by ephemeral
   data store rules.

3.5.3.  Unsupported operations

   <lock> and <unlock> are not supported for a target of ephemeral.

3.5.4.  Interactions with existing capabilities
       requirements Ephemeral-REQ-09 through Ephemeral-REQ-14).

   9.  Ephemeral data stores do SHOULD not require support interactions
       with writable-
   running, writable-running, candidate data store, confirmed commit,
       and a distinct start-up capability,

   Ephemeral data stores only

   This list of requirements require the following the following
   existing features are supported:

      support a "roll-back-on error" (I2RS all-
   or-nothing), URL capability and XPATH capability in source for the following encodings: XML or target.

3.6.  Changes to RESTCONF JSON.

      support for Ephemeral State

   Ephemeral-REQ-08: The conceptual changes to RESTCONF are:

   o the following transports protocol version support - "I2RS-version 1".

   o  ephemeral model scope allowed - ephemeral modules, mixed config
      module (ephemeral and config), mixed derived state (ephemeral and
      config).

   o  multiple message support - "all or nothing",

   o  pane supported: "TCP",
      "SSH", "TLS".

      all of glass support - "single ephemeral pane only".

   o the following NETCONF protocol support - RESTCONF [I-D.ietf-netconf-restconf], [RFC6241] specifications:

      *  yang pub-
      sub pub-sub push [I-D.ietf-netconf-yang-push],

      *  yang module library [I-D.ietf-netconf-yang-library],

      *  call-home [I-D.ietf-netconf-call-home], and

      *  server modules model [I-D.ietf-netconf-server-model] (server with the server
         module must be augmented to support mutual authentication).

   o  encoding support - XML or JSON

   o  transports protocol supported: "SSH", "TLS", "TCP"(non-secure).

   o  ability authentication (see
         [I-D.ietf-i2rs-protocol-security-requirements] section 3.1 in
         requirements: SEC-REQ-01 to select insecure transport SEC-REQ-08).

6.  RESTCONF Features for portion of data model.

3.6.1.  dependencies Ephemeral State for I2RS Protocol version 1

   Ephemeral-REQ-08: The conceptual changes to RESTCONF are:

   1.  Yang data models, sub-modules, or modules must be flagged with
       ephemeral data store flag,

   2.  Yang modules must  protocol version support notification of write conflicts. for I2RS protocol modification (e.g.
       I2RS-version 1).

   2.  ephemeral model scope allowed - ephemeral modules, mixed config
       module (ephemeral and config), mixed derived state (ephemeral and
       config).

   3.  yang modules syntax changes described in section 3.4.

   4.  Yang modules must  support for both of the following NETCONF/RESTCONF
       features:

       1.  the yang-patch features transport protocol suites:

       *  HTTP over TLS (secure HTTP as specified defined in
           [I-D.ietf-netconf-yang-patch].

       2.  The yang module library feature
           [I-D.ietf-netconf-yang-library],

       3.  Publication-Subscription model found RESTCONF
          [I-D.ietf-netconf-restconf] section 2),

       *  HTTP used in
           [I-D.ietf-netconf-yang-push]

       4.  Server initiated connection to a client
           [I-D.ietf-netconf-call-home]

       5.  data models to configure RESTCONF/NETCONF servers
           [I-D.ietf-netconf-server-model],

3.6.2.  modification to context non-secure fashion (See
          [I-D.ietf-i2rs-protocol-security-requirements], section 3.2,
          requirements SEC-REQ-09 and SEC-REQ-11 for details), and

       *  RESTCONF must SHOULD be able to support ephemeral data with an ephemeral
   context that supports "edit-collision" features that include
   timestamp, Entity tag, and expand the transports supported as
          as future I2RS protocol versions may support other transports.

   4.  The ability to compare I2RS client-
   priorities.

3.6.3.  modification restrict insecure transports to existing operations

   The following modification specific portions
       of a data model marked as valid to transfer via an insecure
       protocol.

   5.  Support for the existing operations are required:

   1.  OPTIONS - provide indication development of ephemeral in modules,

   2.  HEAD - able a RESTCONF based yang pub-sub push
       based on the requirements in [I-D.ietf-i2rs-pub-sub-requirements]
       and equivalent to get HEAD of ephemeral or config module or the head
       of groups of netconf . [I-D.ietf-netconf-yang-push]

   6.  ephemeral or state overwriting of configuration nodes in a module.

   3.  GET,Post,PUT, Patch, Delete, Query Parameters - must state MUST be able to
       handle a context="Ephemeral".

   4.
       controlled by the following policy knobs (as defined by
       [I-D.ietf-i2rs-architecture] section 6.3 and 6.3.1)

       *  Ephemeral database must support publication notifications or
       errors as event stream, configuration overwrites local configuration (true/
          false; normal value:true), and subscribing to portions

       *  Update of that event
       stream.  (see [I-D.ietf-netconf-yang-push]

3.7.  Requirements regarding Identity, Secondary-Identity and Priority

3.7.1.  Identity Requirements

   Ephemeral-REQ-09:Clients shall have identifiers local configuration value supercedes and secondary
   identifiers.

   Explanation:

   I2RS requires clients to have an identifier.  This identifier will be
   used by the Agent authentication mechanism over overwrites
          the appropriate
   protocol. ephemeral configuration (true/false; normal value:false).

   7.  The Secondary identities can ephemeral state overwriting a local configuration described
       above is considered to be carried as part of rpc or meta-data
   [I-D.ietf-netmod-yang-metadata].  The primary purpose of the
   secondary identity is for traceability information which logs (who
   modifies certain nodes).  This secondary identity is an opaque value.
   [I-D.ietf-i2rs-traceability] provides an example composite of how the secondary
   identity can be used for traceability.

3.7.2.  Priority Requirements

   To support Multi-Headed Control, I2RS requires that there be all ephemeral state
       values by all clients.  Some may consider this a
   decidable means single "pane of arbitrating
       glass" for the correct ephemeral values.

   8.  RESTCONF support ephemeral state MUST support notification of data when
   multiple clients attempt to manipulate
       write conflicts using the same piece priority requirements (see section 3.7
       below, specifically requirements Ephemeral-REQ-09 through
       Ephemeral-REQ-14).  Expansion of data.  This existing "edit-collision"
       features (timestamp and Entity tag) to include I2RS client-
       priorities is done via a priority mechanism with preferred since I2RS client-Agents exchange MAY
       wish to use the highest priority winning.
   This priority is per-client.

   Ephemeral-REQ-09: The existing edit-collision features in RESTCONF.

   9.  Ephemeral data nodes MAY store I2RS client identity and stores SHOULD not the effective priority at the time the require support for interactions
       with writeable-running, candidate data node is stored. stores, confirmed commit,
       and a distinct start-up capability.

   This requirement also requires that RESTCONF support all of the
   following specifications:

   1.  support for the following encodings: XML or JSON.

   2.  all of the following curren RESTCONF specifications:

       1.  RESTCONF [I-D.ietf-netconf-restconf],

       2.  the yang-patch features as specified in
           [I-D.ietf-netconf-yang-patch],

       3.  yang module library [I-D.ietf-netconf-yang-library] as
           defined in RESTCONF [I-D.ietf-netconf-restconf] section
           3.3.3),

       4.  call-home [I-D.ietf-netconf-call-home],

       5.  zero-touch [I-D.ietf-netconf-zerotouch], and

       6.  server modules [I-D.ietf-netconf-server-model] (server module
           must be augmented to support mutual authentication).

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-09: The data nodes MAY store I2RS Client MUST 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 a time.
   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-10, Ephemeral-REQ-11, and Ephemeral-REQ-12.

   Ephemeral-REQ-10: 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 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.

   Ephemeral-REQ-11: The requirement to support 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 the same node of data are the focus.

   Ephemeral-REQ-12: If two clients have the same priority, the
   architecture says the first one wins.  The I2RS protocol has this
   requirement to prevent was the oscillation between clients.  If one
   uses the last wins scenario, you may oscillate.  That was our
   opinion, but a design which prevents oscillation is the key point.

   Hints for Implementation

   Ephemeral configuration state nodes that are created or altered by
   users that match a rule carrying i2rs-priority will have those nodes
   annotated with meta data.  Additionally, during commit processing, if
   nodes are found where i2rs-priority is already present, and the
   priority is better than the transaction's user's priority for that
   node, the commit should fail.  An appropriate error should be
   returned to the user stating the nodes where the user had
   insufficient priority to override the state.

3.7.3.

8.  Multiple Message Transactions

   Ephemeral-REQ-13: 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 data-store.

   Explanation:

   I2RS suggests the following are some of the potential error handling
   techniques for multiple message sent to the I2RS client:

   1.  Perform all or none: All operations succeed or none of them will
       be applied.  This useful when there are mutual dependencies.

   2.  Perform until error: Operations are applied in order, and when
       error occurs the processing stops.  This is useful when
       dependencies exist between multiple-message operations, and order
       is important.

   3.  Perform all storing errors: Perform all actions storing error
       indications for errors.  This method can be used when there are
       no dependencies between operations, and the client wants to sort
       it out.

   Is important to reliability of the data store that none of these
   error handling for multiple operations in one more multiple messages
   cause errors into be insert the I2RS ephemeral data-store.

   Discussion of Current NETCONF/RESTCONF versus

   RESTCONF does an atomic action within a http session, and NETCONF has
   atomic actions within a commit.  These features may be used to
   perform these features.

   I2RS processing is dependent on the I2RS model.  The I2RS model must
   consider the dependencies within multiple operations work within a
   model.

3.7.4.  Subscriptions to Changed State Requirements

   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 following requirements from the
   [I-D.ietf-i2rs-pub-sub-requirements] apply to ephemeral state:

   o  PubSub-REQ-1: The I2RS interface SHOULD support user subscriptions
      to data with the following parameters: push of data synchronously
      or asynchronously via registered subscriptions.

   o  PubSub-REQ-2: Real time for notifications SHOULD be defined by the
      data models.

   o  PubSub-REQ-3: Security of the pub/sub data stream SHOULD be able
      to be model dependent.

   o  PubSub-REQ-4: The Pub/Sub mechanism SHOULD allow subscription to
      critical Node Events.  Examples of critical node events are BGP
      peers down or ISIS protocol overload bits.

   o  PubSub-REQ-5:I2RS telemetry data for certain protocols (E.g.  BGP)
      will require a hierarchy of filters or XPATHs.  The I2RS protocol
      design MUST balance security against the throughput of the
      telemetry data.

   o  PubSub-REQ-6: I2RS Filters SHOULD be able to be dynamic.

   o  PubSub-REQ-7: I2rs protocol MUST be able to allow I2RS agent to
      set limits on the data models it will support for pub/sub and
      within data models to support knobs for maximum frequency or
      resolution of pub/sub data.

4.  Previously Considered Ideas

4.1.  A Separate Ephemeral Data store

   The primary advantage of a fully separate data store is that the
   semantics of its contents are always clearly ephemeral.  It also
   provides strong segregation of I2RS configuration and operational
   state from the rest of the system within the network element.

   The most obvious disadvantage of such a fully separate data store is
   that interaction with the network element's operational or
   configuration state becomes significantly more difficult.  As an
   example, a BGP I2RS use case would be the dynamic instantiation of a
   BGP peer.  While it is readily possible to re-use any defined
   groupings from an IETF-standardized BGP module in such an I2RS
   ephemeral data store's modules, one cannot currently reference state
   from one data store to another
   For example, XPath queries are done in the context document of the
   data store in question and thus it is impossible a
   model.

9.  Pub/Sub Requirements Expanded for an Ephemeral State

   I2RS model to
   fulfil a "must" or "when" requirement in clients require the BGP module in ability to monitor changes to ephemeral
   state.  While subscriptions are well defined for receiving
   notifications, the
   standard data stores.  To implement such need to create a mechanism would require
   appropriate semantics notification set for XPath.

4.2.  Panes of Glass/Overlay

   I2RS all
   ephemeral configuration state may be overly burdensome to the user.

   There is generally expected 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
   disjoint from persistent configuration.  In some cases, extending
   persistent configuration with ephemeral attributes is expected
   doable without requiring the notifications to be
   useful.  A case that is considered potentially useful but problematic
   was explored was 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 ability following general
   requirements SHOULD be understood to "overlay" persistent configuration
   with be expanded to to include
   ephemeral configuration.

   In this overlay scenario, persistent state:

   o  Pub-Sub-REQ-01: The Subscription Service MUST support
      subscriptions against ephemeral data in operational data stores,
      configuration data stores or both.

   o  Pub-Sub-REQ-02: The Subscription Service MUST support filtering so
      that was not
   shadowed by subscribed updates under a target node might publish only
      ephemeral data in operational data or configuration could be "read through".

   There were two perceived disadvantages to this mechanism:

      The general complexity with managing the overlay mechanism itself.

      Consistency issues with validation should the data, or
      publish both ephemeral state be
      lost, perhaps on reboot.  In such a case, the previously shadowed
      persistent state may no longer validate.

5. and operational data.

10.  IANA Considerations

   There are no IANA requirements for this document.

6.

11.  Security Considerations

   The security requirements for the I2RS protocol are covered in
   [I-D.ietf-i2rs-protocol-security-requirements] document.

7.  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

8.

13.  References

8.1.

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.

   [I-D.ietf-i2rs-protocol-security-requirements]
              Hares, S., Migault, D., and J. Halpern, "I2RS Security
              Related Requirements", draft-ietf-i2rs-protocol-security-
              requirements-03
              requirements-06 (work in progress), March 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-07
              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-09 draft-ietf-i2rs-traceability-11 (work
              in progress), May 2016.

   [I-D.ietf-netconf-call-home]
              Watsen, K., "NETCONF Call Home and RESTCONF Call Home",
              draft-ietf-netconf-call-home-17 (work in progress),
              December 2015.

   [I-D.ietf-netconf-restconf]
              Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
              Protocol", draft-ietf-netconf-restconf-13 (work in
              progress), April 2016.

   [I-D.ietf-netconf-server-model]
              Watsen, K. and J. Schoenwaelder, "NETCONF Server and
              RESTCONF Server Configuration Models", draft-ietf-netconf-
              server-model-09 (work in progress), March 2016.

   [I-D.ietf-netconf-yang-library]
              Bierman, A., Bjorklund, M., and K. Watsen, "YANG Module
              Library", draft-ietf-netconf-yang-library-06 (work in
              progress), April 2016.

   [I-D.ietf-netconf-yang-patch]
              Bierman, A., Bjorklund, M., and K. Watsen, "YANG Patch
              Media Type", draft-ietf-netconf-yang-patch-08 (work in
              progress), March 2016.

   [I-D.ietf-netconf-yang-push]
              Clemm, A., Prieto, A., Voit, E., Tripathy, A., and E.
              Einar, "Subscribing to YANG datastore push updates",
              draft-ietf-netconf-yang-push-02 (work in progress), March
              2016.

   [I-D.ietf-netconf-zerotouch]
              Watsen, K. and M. Abrahamsson, "Zero Touch Provisioning
              for NETCONF or RESTCONF based Management", draft-ietf-
              netconf-zerotouch-08 (work in progress), April 2016.

   [I-D.ietf-netmod-yang-metadata]
              Lhotka, L., "Defining and Using Metadata with YANG",
              draft-ietf-netmod-yang-metadata-07 (work in progress),
              March 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>.

8.2.

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>.

   [RFC6536]  Bierman, A. and M. Bjorklund, "Network Configuration
              Protocol (NETCONF) Access Control Model", RFC 6536,
              DOI 10.17487/RFC6536, March 2012,
              <http://www.rfc-editor.org/info/rfc6536>.

Authors' Addresses

   Jeff Haas
   Juniper

   Email: jhaas@juniper.net

   Susan Hares
   Huawei
   Saline
   US

   Email: shares@ndzh.com