-----Original Message----- From: netmod <netmod-boun...@ietf.org> On Behalf Of Schönwälder, Jürgen Sent: 2020. január 20., hétfő 15:46 To: Kent Watsen <kent+i...@watsen.net> Cc: NETMOD Working Group <netmod@ietf.org> Subject: Re: [netmod] WG Last Call: draft-ietf-netmod-yang-instance-file-format-06
On Tue, Jan 07, 2020 at 12:41:23PM +0000, Kent Watsen wrote: > > This begins a two-week Working Group Last Call (WGLC) on draft-ietf-netmod-yang-instance-file-format-06. The WGLC ends on Jan 21. Please send your comments to the working group mailing list. > > Positive comments, e.g., "I've reviewed this document and believe it is ready for publication", are welcome! This is useful and important, even from authors. Objections, concerns, and suggestions are also welcomed at this time. > I have reviewed draft-ietf-netmod-yang-instance-file-format-06. I believe this is an important document but not quite ready yet. Most of the points I am raising below should, however, be easy to resolve, many concern terminology and writing consolidation and do not affect the technical solution. /js * Abstract I think we should avoid referring to some <get> operation. Here is a proposal of a rewrite: OLD running server available. This document specifies a standard file format for YANG instance data (which follows the syntax and semantic from existing YANG models, re-using the same format as the reply to a <get> operation/request) and annotates it with metadata. NEW running server available. This document specifies a standard file format for YANG instance data, which follows the syntax and semantic of existing YANG models, and annotates it with metadata. BALAZS: Other have expressly asked for a reference to "get" but if you want I can remove it. * Terminology - Add missing dots (full stops) at the end of sentences BALAZS: OK - I fail to see the difference between 'content-schema' and 'content defining YANG module(s)'. The 'content-schema' is already a set of YANG modules. I suggest to remove 'Content defining YANG module(s) as it is not a necessary term. Rewrite all places where the phrase 'content defining YANG modules' is used. BALAZS: a schema is a full set of YANG modules needed to define the structure and properties of the instance data (+features, deviations). A "content defining YANG module" is an individual YANG module is part of the content-schema. So the difference is a set versus one item. I updated the description to emphasize this difference. - Is "YANG Instance Data" a newly defined term? It's introduction does not follow the colon style. I also wonder why we need this term. Why is YANG in there? I would prefer to have this defined in RFC 7950 terms. Is 'instance data' a collection of instantiated 'data nodes'? Perhaps then we should do the following and move this up to the first definition, so we define instance data first, then instance data set, and finally instance data file. OLD YANG Instance Data, or just instance data for short, is data that could be stored in a datastore and whose syntax and semantics is defined by YANG models. NEW Instance Data: A collection of instantiated data nodes. BALAZS: OK, updated. * Introduction - It seems UC5 subsumes UC4. BALAS: OK UC4 and 5 merged - One could add UCx: Storing instance data used as test cases but then this list of use cases does not need to be exhaustive (means I do not care much). BALAZS: Valid use case, but not added for now. If you say so I can add it. - Is it necessary to describe P2 in terms of (presumably) NETCONF operations? I would prefer to have the document written in a protocol agnostic style. Perhaps simply drop "similar to the response of a <get> operation/request". BALAZS: This is a reference both to NETCONF and RESTCONF. It was explicitly asked for by other reviewers. - P4: What is 'many'? Or did you want to use 'multiple'? BALAZS: OK, changed to multiple, * Instance Data File Format - Replace "real data" with instance data OLD "real data" that we want to document/provide. NEW instance data that we want to document/provide. BALAZS: OK - I do not understand that text about the default attribute. Section 4.8.9 defines a query parameter, not an attribute. And I do not know how that fits into content data. BALAZS: https://tools.ietf.org/html/rfc8040#section-4.8.9: " If the "with-defaults" parameter is set to "report-all-tagged", then the server MUST adhere to the default-reporting behavior defined in Section 3.4 of [RFC6243]. Metadata is reported by the server as specified in Section 5.3. The XML encoding for the "default" attribute sent by the server for default nodes is defined in Section 6 of [RFC6243]. The JSON encoding for the "default" attribute MUST use the same values, as defined in [RFC6243], but encoded according to the rules in [RFC7952]. The module name "ietf-netconf-with-defaults" MUST be used for the "default" attribute. " Here the usage of the default ATTRIBUTE is defined. - Similarly, I do not understand why implementation specific metadata may be included in the content-data. This seems to be the wrong place, no? Should metadata not go into the header? BALAZS: As this might be meta-data about the individual instance data nodes (e.g. metadata following the principles from rfc7952) it belongs here. - Why MUST XML attributes be ignored, why is there no text about unknown JSON data, 'attributes' (or annotations)? What should implementations generally do about unknown elements, attributes, objects, arrays, ...)? Why are we specific about only one specific case? BALAZS: Generally we want to allow users/creators to decorate the data with additional information, that is not standardized. Like YANG extensions these may be useful, but at least should not cause problems. XML attributes are often used as meta-data and I was asked to list them specifically. It is not stated what an application should do with additional unknown data (XML elements, JSON data) that do not fit the above categories. Should we say something about it? IMHO no. We don't want to be too restrictive, as there are many potential users with different needs. We could state "Users of the instance data MAY discard any other unknown data". However that does not mean much. - References may be helpful in this sentence since <get-data> is not part of the original NETCONF specification: The content-data part will be very similar to the result returned for a NETCONF <get-data> or for a RESTCONF get operation. BALAZS: OK: will add reference. It is unclear what "will be very similar" really means but perhaps this is clarified later. If not, this sentence says nothing in terms of a technical specification. - Does the following sentence imply that any additional data in an instance file renders the instance file useless? The content-data part MUST conform to the content-schema. BALAZS: Maybe not useless, but at least partly corrupt. - You first write that instance data MUST conform to the schema and two paragraphs later you state that instance data MAY be partial, i.e., it MAY NOT conform to the content-schema. Perhaps I have an idea what you wanted to say but the text that is written here is a contradiction. BALAZS: OK. I will correct it. The content-data part MUST conform to the content-schema, while allowing for the exceptions listed below. - The introduction contains several MAYs and MUSTS that are not understandable yet and they do not seem to belong into an 'Introduction' in the first place. BALAZS: Section 2 Introduction 1 'may' " further instance data formats may be specified" I was specifically asked to include this. Why is this not understandable? Where should this be if not in the introduction chapter? Section 2 does not contain the word must. Maybe I am not understanding your comment. - Why is EXTERNAL in all caps but Inline in capitalized form? In the YANG definitions, EXTERNAL seems to be uri. I think we reduce ambiguity by being consistent with how we name things. BALAZS: OK, EXTERNAL should not be all caps. Here external means that the content-schema is defined externally to the instance data set, not even a URI is included. - What is a 'real-life YANG module'? BALAZS: OK, will rephrase it. - 3.1.1 How are the details specified in the anydata? Perhaps a forward reference might help. What are 'version labels'? BALAZS: Added reference to example. Version/Revision labels are defined in draft-verdt-netmod-yang-module-versioning; added as a reference. I added them here (only as an example) as they are highly relevant to specifying module versions even if they are not agreed in Netmod yet. The name was changed from version-label to revision-label lately. - 3.1.2 What is a 'list of content'? Which revision is used? What about these 'version labels' here? BALAZS: You cut the sentence in half: List of content defining YANG modules" The term "Content defining YANG module" is defined in the terminology section. In this case there is no possibility for using version/revision labels. People asked for a simple method. - 3.2 I do not understand the example. Has this been validated? As far as I can tell, the ietf-yang-library defines modules-state and not module-state. This inconsistency shows up multiple times. BALAZS: Corrected to modules-state - I like to understand why we need several methods to specify the schema. Having N solution is always bad for interoperability and also for maintainability. Perhaps the WG failed to reach consensus on a single solution. Or there are strong technical reasons - but then they should be clearly stated. What are implementations expected to support, all methods? Or whatever the implementer prefers? How do we achieve interoperability across tools? BALAZS: Different people in the WG wanted different solutions. - Some (as I remember you too) asked for a full flexible solution which can use multiple modules potentially not even the ietf-yang-library to define the schema (Inline solution) - some asked for a simple solution listing the content schema modules - some wanted just to use a reference (If any this is the one, I would remove) - some stated that they do not want to define the content-schema at all because it is already known So we ended up with 4 methods * Data Life Cycle - I am not sure the first paragraph is needed. BALAZS: OK removed - In the second paragraph, I like to see some discussion of snapshot consistency. How much consistency can be expected? Are there indicators for the level of consistency? I would remove the sentence about "valid values can be retrieved at run-time" as this is obvious but then I am not sure why 'valid' values? Perhaps the authors meant 'current' values? BALAZS: OK< Changed to current. I want to keep the second sentence as it describes the duality between the original documented values and the current values that can be read in run-time. Consistency is out of scope. No indicators are provided. It is very much use-case and implementation specific. - How do I implement the "SHOULD be described"? The default is that data can change, only in rare cases data is static. But how does a tool creating instance data know 'when and how' data changes in the future? I suggest to remove the SHOULD. The text saying that instance data is a snapshot is in my view sufficient. BALAZS: We do not want to specify the how the changes should be described, But we do want to state that this information should be made available. Just a few ideas how this could be done. Provide - some plain text in the description of the instance data set - some additional metadata e.g. etags, timestamp for the individual data nodes. - a change indicator in the content defining yang module itself - This section talks about YANG instance data but it likely should talk about YANG instance data sets. BALAZS: I think both are acceptable terms here. Naturally if the data changes the data set containing it also changes. * Delivery of Instance Data - Why do we need this SHOULD? I do not think we should use RFC 2119 keywords to define how organizations may use the instance data format. My proposal is to delete this entire section. BALAZS: I will change it to lower case may. I was asked to and I want to state that we want to use instance data both for offline delivery of design time information and for run-time delivery of other data. (The first 3 users of this format all want to use this for early delivery of server capabilities. It is for now the dominant use case for which the 2119 SHOULD is important.). * Backwards Compatibility - I do not think 'managed entity' is a YANG term. BALAZS: What term do you propose for something that is managed like an interface or user etc. ? I was told managed entity is a generic term that is commonly understood . Would "managed item" or "managed thing" be better? - I think this text is use case specific and the items are kind of conflicting with each other (2nd says changing the semantics of a list should lead to a change of the key while the 1st suggests that changing keys may lead to misinterpretation of something being new). - My proposal is to simply drop this entire section. If use case specific text is needed, add it to the use cases in the appendix. BALAZS: You don't know how many trouble reports we got in multiple use-cases for violating these recommendations. While they may not be important for all use-cases, the are important for many. Actually we met the problem or had to avoid it in all but one of the listed use-cases. * YANG Model - How is the inline-content-schema feature used? Which component does indicate that inline content-schema is supported? Do all implementations have to support simplified-inline? If inline-schema is used, how do I find out which schema formats are supported? The more formats there are, the more interoperability issues will arise. Balazs: - case inline { is decorated with "if-feature inline-content-schema" - feature support is generally indicated as part of the ietf-yang-library - simplified-inline is mandatory to support. It is relatively simple, so IMHO not a problem - what do you mean with schema-formats? The yang schema is not actually included anywhere. If the "inline" case is used, instance data corresponding to the inline-modules is included, not the schema. anydata inline-schema { description "Instance data corresponding to the YANG modules specified in the inline-module nodes defining the set of content defining YANG modules for this instance-data-set." * Security Considerations - "is designed as a wrapper" - what does this tell me? I suggest to rewrite the first paragraph and to remove this phrase or to explain what it means. - Why is the header part not security sensitive? Almost all data is security sensitive in certain situations. BALAZS: IMHO it is a valid and meaningful statement to differentiate between security sensitive data like passwords and non-sensitive data like a revision date. RFC8341 states: "One of the most important aspects of the data model documentation, and one of the biggest concerns during deployment, is the identification of security-sensitive content." So the differentiation between sensitive and non-sensitive information is important. In your opinion which part of the header data is sensitive? - I would prefer if the text would not use the phrase "result of a <get> operation". As stated before, I like to see things written in protocol neutral forms. BALAZS: OK, I will change to the generic "read" operation as used by RFC8341 (although for me <get> is much more clear). - Since instance data files may require protection, is there any recommendation how to do this, e.g., by wrapping everything into a cryptographic message syntax or so? It would be important in certain use cases to be able to verify that instance data is authentic (i.e., it is signed by the original source). In other cases, it may be crucial to protect the instance data itself against occasional readers. BALAZS: File security is an important but really big topic and I was instructed by multiple people to avoid a half baked discussion on the topic. - It may be useful to explain that data in instance data sets may have been filtered by access control rules like NACM and that data in instance data sets itself won't be filtered anymore by access control rules like NACM. In other words, if I take snapshots and stored them as instance data files, these snapshots may leak information that is otherwise protected. Hence it is important that NACM rules and file access control rules are consistent. BALAZS: We do not know if the instance data set was originally filtered by NACM or not. We don't know if the users on Netconf/Restconf/cli are the same as the users defined in the file system., so I fear defining what consistent means would be impossible. It is stated that " The same kind of handling should be applied, that would be needed for the result of a <get> operation returning the same data." IMHO we can't really say more. -- Juergen Schoenwaelder Jacobs University Bremen gGmbH Phone: +49 421 200 3587 Campus Ring 1 | 28759 Bremen | Germany Fax: +49 421 200 3103 <https://www.jacobs-university.de/> _______________________________________________ netmod mailing list netmod@ietf.org https://www.ietf.org/mailman/listinfo/netmod
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