One document matched: draft-ietf-i2rs-ephemeral-state-06.xml

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<rfc category="std" docName="draft-ietf-i2rs-ephemeral-state-06"  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>This document covers requests to the netmod and netconf Working
   Groups for functionality to support the ephemeral state requirements
   to implement the I2RS architecture. </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="I-D.ietf-i2rs-architecture"></xref> abstractly documents a number
   of requirements for implementing the I2RS requirements.</t>
   <t>
   The I2RS Working Group has chosen to use the YANG data modeling
   language <xref target="RFC6020"></xref> as the basis to implement its mechanisms.
   </t>
   <t> 
   Additionally, the I2RS Working group has chosen to use the 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>
   While YANG, NETCONF and RESTCONF are a good starting basis for I2RS,
   there are some things needed from each of them in order for I2RS to
   be implemented.
	 </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 following are ten requirements that 
 <xref target="I-D.ietf-i2rs-architecture"></xref>
  contains which are important high level requirements:  
<list style="numbers">
<t>The I2RS protocol SHOULD support highly reliable notifications (but
not perfectly reliable notifications) from an I2RS agent to an  I2RS client. </t>
 <t>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. </t>
<t> The I2RS protocol will operate on data models which may be protocol
independent or protocol dependent.  </t>
<t> I2RS Agent needs to record the client identity when a node is created or modified. 
The I2RS Agent needs 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.</t>
<t>Client identity will have only one priority for the client identity. A
collision on writes is considered an error, but priority 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.</t>
<t>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. </t>
<t>An I2RS Client and I2RS Agent mutually authenticate each other based on
pre-established authenticated identities. </t>
<t>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 only recorded when
the data node is written or updated or deleted</t>
<t>I2RS agent can 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 
(<xref target="RFC6536"></xref>)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.  
</t>
<t>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.</t>
</list>
</t>
</section>
 <section title="Ephemeral State Requirements"> 
<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 utilized
   temporary operational state (e.g. MPLS LSP-ID or a BGP IN-RIB) as a constraints. 
   </t>
   <t>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.</t>
 </section>
<section title="Hierarchy">
	<t>Ephemeral-REQ-05: The ability to add on an object
	(or a hierarchy of objects) that have the property of
	being ephemeral. </t>
</section> 
<section title="Changes to YANG">
<t>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. 
</t>
<section title="Suggested Yang syntax changes">
<t>
The minimal changes to Yang are: 
<list style="numbers">
<t>protocol version support - "I2RS version 1", </t>
<t>ephemeral true; (key word) 
</t>
<t>data models indicate which component protocol is supported "NETCONF", "RESTCONF"
</t>
<t>encoding support - XML or JSON</t>
<t>data models indicate which transports protocol supported:"SSH", "TLS", "TCP" (nonsecure);
</t>
<t>configuration for non-secure transport
<list>
<t>i2rs-transport-non-secure ok; </t>
</list>
</t>
<t>Configuration for no validation checks: 
ephemeral-validation no check;
<list> 
<t>
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  </t>
<t>the key word "full" implies the I2RS Client is doing all
validation normally done for a configuration node.</t>
</list>
</t>
<t>
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 for all I2RS ephemeral writes is full.
</t>
<t>Note: Anything less than full validation runs the 
risk of having bad data in the I2RS ephemeral state. 
</t>
</list>
</t>
</section>
 </section>
<section title="Minimal Changes to NETCONF for I2RS Protocol version 1">
<t>
Ephemeral-REQ-07: The conceptual changes to NETCONF 	
<list style="symbols">
<t>protocol version support - "I2RS-version 1", </t>
<t>ephemeral model scope - ephemeral modules, 
mixed config module (ephemeral and config),
mixed derived state (ephemeral and config). 
</t>
<t>multiple message support - "all or nothing", 
</t>
<t>pane of glass support - single ephemeral pane only.</t>
<t>protocol support -  NETCONF <xref target="RFC6241"></xref>, 
yang pub-sub push <xref target="I-D.ietf-netconf-yang-push"></xref>,
yang module library <xref target="I-D.ietf-netconf-yang-library"></xref>,
call-home <xref target="I-D.ietf-netconf-call-home"></xref>,  
and server modules <xref target="I-D.ietf-netconf-server-model"></xref>
(server module must be augmented to support mutual authentication). 
</t>
<t>encoding support - XML or JSON</t>
<t>transports protocol supported: "TCP", "SSH", "TLS", 
non-secure, and others.
</t>
<t>ability to select transports data model available for management
protocol.  Insecure portions must be able to select a insecure transport.</t>
<t>yang modules syntax changes described in section 3.4.</t>
</list>
</t>
<section title="Dependencies">
<t>
<list style="numbers">
<t>Yang data models, sub-modules, or modules
must be flagged with ephemeral data store flag, 
</t>
<t>Yang modules must support notification of write conflicts.</t>
<t>yang modules syntax changes described in section 3.4.
</t>
<t>Yang modules must support the following NETCONF/RESTCONF 
features: 
<list> 
<t>The yang module library feature <xref target="I-D.ietf-netconf-yang-library"></xref>,
</t>
<t> Publication-Subscription model found in
<xref target="I-D.ietf-netconf-yang-push"></xref>
</t>
<t>Server initiated connection to a client 
<xref target="I-D.ietf-netconf-call-home"></xref>
</t>
<t> data models to configure RESTCONF/NETCONF servers
<xref target="I-D.ietf-netconf-server-model"></xref>,</t>
</list>
</t>
</list>  
</t>
</section> 
<section title="Modified operations">
<t><get-config>, <edit-config>
<copy-config>, <delete-config>
<get> <close-session>, 
<kill-session> are altered to abide by 
ephemeral data store rules. 
</t>
</section> 
<section title="Unsupported operations">
<t><lock> and <unlock> are
not supported for a target of ephemeral. 
</t>
</section>
<section title="Interactions with existing capabilities">
<t>Ephemeral data stores do not support 
interactions with writable-running, candidate
data store, confirmed commit, and a distinct start-up capability,
</t>
<t> Ephemeral data stores only support a 
"roll-back-on error" (I2RS all-or-nothing), 
URL capability and XPATH capability in source or target.
</t>
</section>
</section> 
<section title="Changes to RESTCONF for Ephemeral State">
<t>Ephemeral-REQ-08: The conceptual changes to RESTCONF are:   	
<list style="symbols">
<t>protocol version support - "I2RS-version 1". </t>
<t>ephemeral model scope allowed - ephemeral modules, 
mixed config module (ephemeral and config),
mixed derived state (ephemeral and config). 
</t>
<t>multiple message support - "all or nothing", 
</t>
<t>pane of glass support - "single ephemeral pane only".</t>
<t>protocol support - RESTCONF <xref target="I-D.ietf-netconf-restconf"></xref>,
yang pub-sub push <xref target="I-D.ietf-netconf-yang-push"></xref>,
yang module library <xref target="I-D.ietf-netconf-yang-library"></xref>,
call-home <xref target="I-D.ietf-netconf-call-home"></xref>,  
and server modules <xref target="I-D.ietf-netconf-server-model"></xref>
(server module must be augmented to support mutual authentication). 
</t>
<t>encoding support - XML or JSON</t>
<t>transports protocol supported:   "SSH", "TLS", "TCP"(non-secure). 
</t>
<t>ability to select insecure transport for portion of data model. 
</t>
</list>
</t>
<section title="dependencies for RESTCONF">
<t>
<list style="numbers">
<t>Yang data models, sub-modules, or modules
must be flagged with ephemeral data store flag, 
</t>
<t>Yang modules must support notification of write conflicts.</t>
<t>yang modules syntax changes described in section 3.4.
</t>
<t>Yang modules must support the following NETCONF/RESTCONF 
features: 
<list> 
<t> the yang-patch features as specified in 
<xref target="I-D.ietf-netconf-yang-patch"></xref>.</t>
<t>The yang module library feature <xref target="I-D.ietf-netconf-yang-library"></xref>,
</t>
<t> Publication-Subscription model found in
<xref target="I-D.ietf-netconf-yang-push"></xref>
</t>
<t>Server initiated connection to a client 
<xref target="I-D.ietf-netconf-call-home"></xref>
</t>
<t> data models to configure RESTCONF/NETCONF servers
<xref target="I-D.ietf-netconf-server-model"></xref>,</t>
</list>
</t>
</list>
</t>
</section>
<section title="modification to context">
<t>RESTCONF must be able to support ephemeral data with 
an ephemeral context that supports "edit-collision" features
that include timestamp, Entity tag, and the ability to 
compare I2RS client-priorities.</t>
</section>
<section title="modification to existing operations">
<t>The following modification to the existing operations
are required: 
<list style="numbers">
<t>OPTIONS - provide indication of ephemeral in modules,
</t>
<t>HEAD - able to get HEAD of ephemeral or config module or
the head of groups of ephemeral or configuration nodes in a module.
</t>
<t>GET,Post,PUT, Patch, Delete, Query Parameters - must be able to handle 
a context="Ephemeral". </t>
<t>Ephemeral database must support publication notifications or errors  
as event stream, and subscribing to portions of that event stream. 
(see <xref target="I-D.ietf-netconf-yang-push"></xref></t>
</list>
</t>
</section>
</section>
 <section title="Requirements regarding Identity, Secondary-Identity and Priority">
 <section title="Identity Requirements">
 <t>Ephemeral-REQ-09:Clients shall have identifiers and secondary identifiers.
 </t>
  <t>Explanation:</t>
  <t>I2RS requires clients to have an identifier.  This identifier will be
   used by the Agent authentication mechanism over the appropriate
   protocol. </t>
   <t>The Secondary identities can be carried as part of rpc or meta-data
    <xref target="I-D.ietf-netmod-yang-metadata"></xref>.   
	The primary purpose of the secondary identity is for traceability information
	which logs (who modifies certain nodes).  This secondary identity is an opaque value.  
	<xref target="I-D.ietf-i2rs-traceability"></xref> provides an 
	example of how the secondary identity can be used for traceability.
   </t>
 </section>
 <section title="Priority Requirements">
   <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-09: The data nodes MAY store I2RS client identity and not
   the effective priority at the time the data node is stored. 
   The I2RS Client MUST have one priority at a time. 
   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. </t>
   <t>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. 
   </t> 
   <t>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.  </t>
   <t>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. 
 </t>
<t> Hints for Implementation </t>
<t>
   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.
</t>
 </section>
  <section title="Transactions">
 <t> Ephemeral-REQ-13: Section 7.9 of the <xref target="I-D.ietf-i2rs-architecture"></xref>
 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. 
</t>
<t>
Explanation: 
</t>
<t>
I2RS suggests the following are some of the potential error handling techniques
for multiple  message sent to the I2RS client:
 <list style="numbers">
 <t>Perform all or none: All operations succeed or none of them will be applied. 
   This useful when there are mutual dependencies.</t>
 <t>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.</t>
  <t>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.</t>
 </list> 
 </t>
<t>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. 
</t>
<t>
</t>
<t>Discussion of Current NETCONF/RESTCONF versus </t>
<t>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.</t>
<t> I2RS processing is dependent on the I2RS model. The I2RS model must consider 
the dependencies within multiple operations work within a model.  
</t>
 </section>
 <section title="Subscriptions to Changed State Requirements">
 <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 following requirements from the 
<xref target="I-D.ietf-i2rs-pub-sub-requirements"></xref> apply to ephemeral 
   state: 
   <list style="symbols">
   <t>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.
   </t>
   <t>PubSub-REQ-2: Real time for notifications SHOULD be defined by the data models.
   </t>
   <t>PubSub-REQ-3: Security of the pub/sub data stream SHOULD be able to be
   model dependent.</t>
   <t>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.</t>
   <t>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. </t>
   <t>PubSub-REQ-6: I2RS Filters SHOULD be able to be dynamic. </t>
   <t>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.   </t>
  </list></t>
 </section>
 </section> 
 </section>
<section title=" Previously Considered Ideas">
 <section title="A Separate Ephemeral Data store">
 <t>
 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.
 </t>
 <t>
    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
 </t>
 <t>
    For example, XPath queries are done in the context document of the
   data store in question and thus it is impossible for an I2RS model to
   fulfil a "must" or "when" requirement in the BGP module in the
   standard data stores.  To implement such a mechanism would require
   appropriate semantics for XPath.
 </t>
 </section>
 <section title=" Panes of Glass/Overlay">
 <t>   I2RS ephemeral configuration state is generally expected to be
   disjoint from persistent configuration.  In some cases, extending
   persistent configuration with ephemeral attributes is expected to be
   useful.  A case that is considered potentially useful but problematic
   was explored was the ability to "overlay" persistent configuration
   with ephemeral configuration.
 </t>
 <t>   In this overlay scenario, persistent configuration that was not
   shadowed by ephemeral configuration could be "read through".
 </t>
 <t>   There were two perceived disadvantages to this mechanism:
 <list>
 <t>The general complexity with managing the overlay mechanism
       itself.</t>
 <t>Consistency issues with validation should the ephemeral state be
       lost, perhaps on reboot.  In such a case, the previously shadowed
       persistent state may no longer validate.
</t>
 </list>
 </t>
 </section>
 </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.
	  </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>
	    </list>
	</t>
</section>
</middle>
  <back>
    <references title="Normative References:">
	 &RFC6241;
     &I-D.ietf-netconf-restconf;
	 &I-D.ietf-i2rs-architecture;
	 &I-D.ietf-i2rs-traceability;
	 &I-D.ietf-i2rs-pub-sub-requirements;
	 &I-D.ietf-i2rs-protocol-security-requirements;
	 &I-D.ietf-netmod-yang-metadata;
	 &I-D.ietf-netconf-yang-library;
	 &I-D.ietf-netconf-yang-push;
	 &I-D.ietf-netconf-yang-patch;
	 &I-D.ietf-netconf-server-model;
	 &I-D.ietf-netconf-call-home;
	</references>
    <references title="Informative References">
      &RFC2119;
	  &RFC6020;
	  &RFC6536;
    </references>
  </back>
</rfc>