Re: [OPS-AREA] RE: [OPS-NM] Comments on XSDMI BoF proposal

[Jon Saperia <[e-mail]>]

One comment/question in line below:

Romascanu, Dan (Dan) wrote:

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See in-line a few comments from a contributor perspective. 

Dan

 
 

  

-----Original Message-----
From: David Harrington [mailto:[e-mail]] 
    

I strongly support the formation of this WG, and think it should be 
the "only next step" in NETCONF Data Modeling standards development.
      

Trying to standardize too much at once without enough 
      

implementation 
    

experience is not going to help.  The most critical DM need is to 
figure out how to use the standard NM data definitions we already 
have.
      

My intention is to develop a way to access MIB data via 
XML-based NM protocols, to take advantage of the existing NM 
data definitions in the MIB. 

This is a migration strategy to move from a 
mainly-SNMP-and-MIB management framework to a 
multi-protocol-and-multi-data-model
management framework. 

I do not think MIB access is enough. A binary data-based 
approach like the MIB is fine for automated management, but 
it is not good for operator-interactive management, and it 
fails to take advantage of advances in computer networking 
technology like WWW technologies.

For operator-interactice NM, I think we need task-based NM interfaces.
The CLI is one approach, and standardizing it would probably 
be helpful, but the engineering departments of vendors are 
not very cooperative on doing that; it is easier for 
engineers to use freeform text when developing CLIs and 
syslog-style reporting than to use standardized content. 
    

I do not believe that a standard CLI is achievable in the IETF. By now
we should assume this is not going to happen. 

  

XML-based management leverages lessons learned from the WWW. 
While document-based rather than command-based, tasks can 
often be grouped into a document-type interface, such as a 
web page. With automated translation from XML into HTML (and 
related technologies), we can work on developing 
task-based-document NM interfaces. 

I think we need to spend more time thinking about operator 
use-cases, not just technical designs of SMIs. I think it 
would help to start thinking in terms of modular data models 
similar to MIB modules, not just a <running> config,  but we 
need to develop an SMI that helps to differentiate config and 
state info, which SMIv2 doesn't do, Maybe all we need to do 
is recommend that MIB modules have separate subtrees for 
config and for state, much as we now recommend separate 
subtrees for objects and notifications. 
    

Maybe, but at this point in time all the base of standard MIB modules is
not designed this way. What are we going to do, re-write these MIB
modules, or part of them? This does not seem an achievable task. 
  

I have seen a couple of references in the discussion to State and netconf.  Can we be more specific about what we mean by state here.  Configuration state?  When I think of other types of state such as operational state or quality state I think of either read MIB objects or notifications (traps/informs).

The suggestion of using subtrees for functional (e.g., FCAPS) separation has worked well in some cases (we use 0 for notifications right). 

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While I would like to see the reuse of existing standards, 
such as XSD, we need to support programmatic interfaces to 
allow (incremental) automation of repetitive tasks. That 
means we need to provide machine-readable "clues" about the 
meta-nature of management information. Maybe that can be done 
in XML using attributes, or namespaces, or hierarchical 
organization. Maybe it will require a new SMI with all the 
special fields found in SMIv2 - and more. 

I think one of the big questions we need to address is 
whether a new SMI should be developed that is an 
extension/superset of SMIv2, or is distinct from SMIv2. I 
think that work involves getting operator feedback of how 
they work, so we can understand whether we should be trying 
to merge the existing NM protocols, or should keep them (and 
their data) distinct. I think we should be considering how to 
componentize existing standards work, so we can reuse some 
parts, such as secure transport, while keeping other parts distinct. 
    

I somehow like the paradigm - SNMP for performance monitoring and
alerts, Netconf for configuration and status retrieval. Could we
consider that the current standard MIB modules based would be used for
read configuration operations, like declare it as the status branch in
each MIB, ignoring the configuration objects and build atop of it what
is needed for configuration, even if this means duplication of some
objects. Simple or too simplistic? 

  

That work can advance while we work on developing support for 
one or more XML-based interfaces to SMIv2 data models, as a 
migratory step toward multi-protocol management.

    

Nit: The WG acronym is kind of cryptic and I'm not sure what it 
supposed to mean.  Also, the WG name only describes work items
(A) and (B).  Security requirements for multi-protocol 
      

access to MIB 
    

data is definitely not covered by the title, and (D) is 'possibly' 
NETCONF protocol-specific. (?? XSMI ?? SMIX ??
SMINET ??)
      

I deliberately avoided the use of SMI. As somebody pointed 
out (you?), this work (A and B) is not developing a new SMI, 
it is merely translating elements of SMIv2 from one language 
to another.

    

Milestones:  Any idea how long you think it will take to do 
      

all this 
    

work?

Work items:

(A)(B)
The XSD for SMIv2 data types and TCs draft has been reviewed and 
refined over a couple years, and it is very much needed, and ready, 
for standardization.
      

Yan will be publishing a base datatype translation document, 
based on libsmi translations. Since this has been defined and 
used(?) fo ryears, I expect this should be fast - in IETF 
terms, we can probably finish in seven or eight years ;-). 
Seriously, I hope this can be done in six months or so, if 
there is enough interest to work on it.

That will be supplemented by the (romascanu) TC translations document.
We need to decide whether XSD can express the restrictions 
adequately to support machine-validation, and whether the 
amount of machine-validation supported justifies having an 
XSD for the TC.
Having TC translations might be helpful for netconf to go 
read existng MIB data, without having to also parse SMIv2 MIB 
documents to understand what the values mean. I think the 
bigger benefit is defining TCs that can be used by multiple 
protocols to support consistent semantics across protocols, 
and XML is the preferred language for most new protocols.

This will require case-by-case analysis, and might take time 
to reach consensus. Of course, not every contentious TC must 
be included in this document, so if we cut out the 
contentious ones, this should be able to be wrapped up within 
a year, I hope.
    

I would try to push for a more aggressive schedule, even if it's a
smaller set of TCs. It's not that all needs to be standardized in RFC
form, but it is better to have this in a stable format for other work to
re-use it including proprietary implementations to deploy this. 

  

(C)
This work item is a bit vague.  I'm not sure if it means a mapping 
between an SNMP EngineID to a NETCONF session identity, or 
      

something 
    

to do with VACM, or something else undefined.
I think it is a smart idea to understand all the security issues 
associated with (D).
      

I'm looking at the bigger picture of multi-protocol 
management. There are lots of protocols being developed, both 
inside and outside IETF, to perform management functionality. 
As Bob Natale pointed out, the MIB is the "crown jewel" of 
IETF Management (I think SNMP is as well, when used for what 
it is good at). I think lots of WGs and lots of other SDOs 
are going to look at the MIB and say "gee, we should leverage that!"

I think we need to set some guidelines about how protocols 
should deal with the MIB, so that it is not ruined by 
unconstrained access by multiple protocols, especially write access.

But even read-access can be problematic. Security is a 
process, not a product. The IETF needs to decide how to 
"balance" security in an environment of multi-protocol 
management. It makes no sense to protect your house with a 
front door that has multiple deadbolt locks, if your back 
door has no locks. 

It makes no sense to expect operators to go to the trouble of 
configuring VACM to protect the data in the MIB when using 
SNMP, if the operator's VACM configuration will just be 
ignored by netconf and other protocols accessing the MIB. I 
think we need some guidelines that provide for a more 
consistent approach to multi-protocol MIB access, than 
VACM-for-SNMP and nothing-for-others. 

Personally, I would like to see VACM not be 
mandatory-to-implement for SNMP, if there is no corresponding 
mandatory-to-implement access control for other protocols. I 
don't think the operator community is actually ready for 
standardized cross-protocol access control, and if it isn't 
balanced across protocols, then we shouldn't require any NM 
protocol standards to have a mandatory-to-implement access 
control model.
    

I confess that this is confuse for me too. I am not sure that I
understand what is the deliverable here, or whether the problem can be
solved within the context of this working group. 

  

(D)
I support a standard algorithmic translation between SMIv2
      

conceptual
    

data models and NETCONF configuration databases, which 
      

includes data 
    

organization and standard protocol operation mappings.
I think read-only access instead of full access will be easier to 
achieve, so it should be done first.  The use case for 
      

write access is 
    

not as strong, and the multi-protocol access and security 
      

issues are 
    

harder.
      

I agree that read-only access would probably be sufficient 
for netconf to gather state information, statistical 
information, and notifications. I do not see a lot of reason 
to support write access to the MIB via netconf.
    

Yes, see the above.

  

I do not support a generic XSD representation of SMIv2 
      

macros, without 
    

consideration of the specific XML-based protocol being used.
The 'embedded' SNMP protocol operations in SMIv2, as well as the 
explicit SNMP operations discussed in MIB object 
      

DESCRIPTION clauses, 
    

RowPointer, RowStatus, StorageType, etc., all have to be explicitly 
mapped to
      

the
    

specific NETCONF (or whatever) protocol operations and architecture 
assumptions.
      

I think these need to be supported to understand the values 
of certain fields that might be read from the MIB. 

RowStatus reflects the operational state of the row, and if 
netconf is accessing the MIB to determine operational state 
of the thing represented by that row, it is an important 
piece of information. But if netconf has no write capability 
to the MIB, it does not need to know how to manipulate the values.

StorageType is also state information about a row that might 
be important for a netconf client to understand; it might be 
helpful to know that the MIB representation (or the 
underlying instrumentation) is in ROM. But if it has no write 
capability, it does not need to know how to manipulate the 
row within the constraints of StorageType. 

The MIB is more or less a relational database, where the 
relations between rows is important information. If netconf 
reads a row that has a relationship to another row via a 
RowPointer, netconf better know how to interpret a RowPointer.

(It is important to understand that I make no assumptions 
that a netconf-client will have a direct connection to an 
SNMP manager that knows how to parse this information from an 
SMIv2  MIB module
document.)

I think we need to walk through these TCs on a case-by-case 
basis to decide whether we need each one for use with 
netconf, and what XSD restrictions apply.
    

Agree with David on this one. 

  

David Harrington
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-- 
Jon Saperia
(cell) 617-201-2655
(Eve.) 978-461-0264

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