[MIB-DOCTORS] FW: Benoit Claise's Discuss on draft-ietf-manet-nhdp-mib-14: (with DISCUSS and COMMENT) (UNCLASSIFIED)

["Cole, Robert G CIV USARMY CERDEC (US)" <[e-mail]>]

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Tom, MIB-Doctor's.

We are looking for some guidance on one of the comments on the NHDP-MIB below, 
specifically issue #6.  Please see below.

Thanks, Bob

-----Original Message-----
From: Cole, Robert G CIV USARMY CERDEC (US)
Sent: Wednesday, June 13, 2012 12:53 PM
To: 'Benoit Claise'; [e-mail]
Cc: 'The IESG'; [e-mail]; 
[e-mail]; 'Ulrich Herberg'
Subject: RE: Benoit Claise's Discuss on draft-ietf-manet-nhdp-mib-14: (with 
DISCUSS and COMMENT) (UNCLASSIFIED)

Classification: UNCLASSIFIED
Caveats: NONE

Benoit,

I am struggling with your comments on the nhdpInterfaceTable (item #6 below).
I give two alternatives (please read way below).

a) I understand that this could be constructed as an AUGMENTS to the IF-MIB
ifTable.  E.g., (although the use of the nhdpIfRowStatus here does not seem
right)

"  nhdpInterfaceEntry OBJECT-TYPE
      SYNTAX      NhdpInterfaceEntry
      MAX-ACCESS  not-accessible
      STATUS      current
      DESCRIPTION
         "nhdpInterfaceEntry describes one NHDP
          local interface configuration.  It is
          constructed as an AUGMENTS to the
          Standard MIB II Interface Table (RFC2863)."
      AUGMENTS { ifIndex }
   ::= { nhdpInterfaceTable 1 }

   NhdpInterfaceEntry ::=
      SEQUENCE {
         nhdpIfStatus
            TruthValue,
         nhdpHelloInterval
            Unsigned32,
         nhdpHelloMinInterval
            Unsigned32,
         nhdpRefreshInterval
            Unsigned32,
         nhdpLHoldTime
            Unsigned32,
         nhdpHHoldTime
            Unsigned32,
         nhdpHystAcceptQuality
            Float32TC,
         nhdpHystRejectQuality
            Float32TC,
         nhdpInitialQuality
            Float32TC,
         nhdpInitialPending
            TruthValue,
         nhdpHpMaxJitter
            Unsigned32,
         nhdpHtMaxJitter
            Unsigned32,
         nhdpIfRowStatus
            RowStatus
         }
"


b) Instead we chose to extend the ifTable through a common indexing.  A
precedence does exists to our approach, e.g.,


"ipv4InterfaceEntry OBJECT-TYPE
    SYNTAX     Ipv4InterfaceEntry
    MAX-ACCESS not-accessible
    STATUS     current
    DESCRIPTION
           "An entry containing IPv4-specific information for a specific
            interface."
    INDEX { ipv4InterfaceIfIndex }
    ::= { ipv4InterfaceTable 1 }nhdpIfRowStatus

Ipv4InterfaceEntry ::= SEQUENCE {
        ipv4InterfaceIfIndex         InterfaceIndex,
        ipv4InterfaceReasmMaxSize    Integer32,
        ipv4InterfaceEnableStatus    INTEGER,
        ipv4InterfaceRetransmitTime  Unsigned32
    }

ipv4InterfaceIfIndex OBJECT-TYPE
    SYNTAX     InterfaceIndex
    MAX-ACCESS not-accessible
    STATUS     current
    DESCRIPTION
           "The index value that uniquely identifies the interface to
            which this entry is applicable.  The interface identified by
            a particular value of this index is the same interface as
            identified by the same value of the IF-MIB's ifIndex."
    ::= { ipv4InterfaceEntry 1 }
"

What is your recommendation?

Thanks,
Bob Cole


-----Original Message-----
From: Benoit Claise [mailto:[e-mail]]
Sent: Thursday, June 07, 2012 11:05 AM
To: [e-mail]
Cc: 'The IESG'; [e-mail];
[e-mail]
Subject: Re: Benoit Claise's Discuss on draft-ietf-manet-nhdp-mib-14: (with
DISCUSS and COMMENT)

Hi Adrian,


	Hi Benoit,

	I'm going to be a bit sniffy here :-)


		- There is a clear DISCUSS coming from the MIB-doctor review. Please
		address it.


	Sorry, what is your Discuss?

My Discuss is simply: improve the MIB module according to the MIB doctor
Looking at the long list of open issues, copied for the IESG convenience
below, I wrote "clear DISCUSS"


	General Comments
	----------------


	 1.  I did not re-compile the MIB as I am assuming Bert's comments from
compilation were sufficient.  These comments are IN ADDITION to Bert's so
please make fixes required from his comments too.

	2. Please go through the objects in the module and look for uses of
DISPLAY-STRING and UNITS where possible. There are numerous cases where it
should have been used but wasn't. I did not point out every one, just the
first one.

	3. In general, you have not explicitly described what happens to rows in the
tables where read-create objects exist. You must describe these behaviors. I
have noted the first instance of this, but please check all tables.

	4. The use of DisplayString in the MIB is quite prevalent. RFC4181 is very
clear in stating that:

	   Note 2.  DisplayString does not support internationalized text.  It
	            MUST NOT be used for objects that are required to hold
	            internationalized text (which is always the case if the
	            object is intended for use by humans [RFC2277]).  Designers
	            SHOULD consider using SnmpAdminString, Utf8String, or
	            LongUtf8String for such objects.



	5. You need a DEFVAL for *every* read-create object. I have noted the first
case, but there are LOTS of these in the module that need to be fixed.

	6. There is some confusion about your ifTable interaction. You seem to want
an EXTENDS relationship, but your modeling is one of AUGMENTS. That is, the
index text describes two types of interfaces (without a proper ifType BTW),
where you allow for the modeling of non-manet interfaces. What I think you
want to do is have this relationship:

	ifEntry NhdpInterfaceEntry
	1, ifType=mols
	2, ifType=mpls
	3, ifType=manet    ---------> 3
	4, ifType = manet  --------->       4
	5, ifType = mpls

	That is, you do not have entries in the NhdpInterfaceEntry table for
ifIndex-es 1, 2 and 5.


	7. I think it is customary to include the full reference description in the
REFERENCE clause. For example:

	           "RFC 2863 - The Interfaces Group MIB, McCloghrie, K.,
	             and F. Kastenholtz, June 2000"


	There are a number of these in the document, but I have only noted the first
one. Please go through the document and make these corrections, and please do
it consistently.

	8. When you use InetAddress, you are constraining it to 4 or 16. This is
unusual. It is typical to just use the TC as-is.

	9.  I have found a number of tables that match this guidance. The easiest
thing to do is create a StorageType object in each table and define its
semantics.  I have only noted one case of this, but there are a number of
them.

	There either MUST be one columnar object with a SYNTAX value of
	       StorageType [RFC2579] and a MAX-ACCESS value of read-create, or
	       else the row object (table entry) DESCRIPTION clause MUST specify
	       what happens to dynamically-created rows after an agent restart.





	10. In the notifications section, there is ambiguous terminology like
"significant number"; you need to define what you expect this means.   In
fact, there is a lot of examples for defining explicit MIB variables like
nhdpNbrStateChangeThreshold that explicitly define this. This will help aid
interoperability.  All of the notifications suffer from this deficiency.


	11. The notifications emitted here seem to be potentially of a high volume
given that manet applications can include massive numbers of "mobile" devices.
You really should include some limiting/throttling parameters as explicit MIB
configuration values.  I know that you have defined this in some of the
description clauses, but this is not easily interoperable, especially if
implementations really need to use smaller values.  Also, the way things are
written, it is possible for implementations to experience DoS attack on the
device because it is forced to emit so many notifications that it overwhelms
the CPU. The "bad packets" notification is a great example.

	12. The  nhdpIfState notification is potentially dangerous given how the
IfTable relationship is currently defined above to be essentially a 1:1 match
with the IfEntry.  Imagine having to issue notifications constantly for IF
state changes for every interface in the normal IF-MIB and then here?  Also,
what value does this notification add above/beyond the normal IfUp/Down
notification if you define an ifType=manet as I suggested above?

	13. The  nhdpPacketSrcAddr  notification has no limits or throttling. What if
%100 of the packets sent to the device match this criteria? Do you issue a
notification for every one?





	Could you please capture your Discuss in the data tracker so that it can be
resolved in discussion with you.

Ok.





		- While reading through the document, I've been really waiting for an
		applicability statement section.


	So, I think you are asking "Why would any application that is not using
telnet and a CLI or directly attached to the node want to know any details
about the topology learnt by the node?"

Not really, basically, I'm asking a very simple question: how do you plan on
managing an ad-hoc network?




	I might ask you what is the point of the IF-MIB? Why would any management
application ever want to learn about the behavior of a network node using a
standardised protocol?

I don't understand this.





		A sentence [RFC6130] such as "if router A is able to exchange packets
		with router B, and router B is able to exchange packets with router C,
		this does not guarantee that router A and router C can exchange packets
		directly" got me thinking about the management and operational aspects.
		How do you plan on using this MIB module, taking into account that you're
		dealing with an ad-hoc network?


	I am not sure whether you asking
	- How will a TCP-based application work in a MANET?

Yes.



	or
	- What information might you learn from a MANET node
	   that implements NHDP?

	NHDP discovers neighbors. Neighbor relationships are not necessarily
symmetric. They are hard to predict because they depend on physical placement
of the nodes (and other conditions that affect wireless transmissions).
Reading the information gathered using NHDP allows an external application to
generate  map of the topology. Reading statistics about the performance of the
protocol allows an application to assess whether there is a misbehaving
implementation and also whether the reported topology is likely to be
accurate.

	This all seems rather "obvious". I guess a statement like this could be added
to the document. I hope that this would mean that *every* MIB module that goes
for publication from now on will be required to add similar explanation of why
a MIB module is relevant.


		Note that the write-up mentions: "This document shepherd is not aware of
		existing implementations of this MIB although several implementers have
		indicated interest in the work."
		So the potential implementers should have some views on the following
		questions.

		I'm really after 3 different parts in the applicability statement (or
		call it use cases if you want to): configuration management, monitoring,
		and notification. And I have questions such as:
		* one static NMS or each MANET router configures/monitors his (newly
		attached) neighbor(s)?


	I think the question you are asking is about write-access. I think it is
obvious from the module that the node can update the information that is
reported by an application reading the module. So the question is why is so
much write-access needed to so many objects in the module? That is something
the authors/WG need to answer.

Coming back to my basic question: how do you plan on managing an ad-hoc
network?
Do you want to have one static NMS monitoring the entire network, or do you
want to have every router only monitoring his neighbors (*).





		* where are the notifications sent to?


	Hmmm? Why is this question any different for this module compared with any
other module? Who consumes Notifications from other modules?

In the case of (*)





		* Do you expect all MANET routers to always have connectivity to a static
		NMS?


	Why ever not? It is a routed IP network. If there is a management station
present, it can connect. If the network becomes partitioned, well, this is the
same problem as in any other network.

You know, I started to find a couple of my points addressed in
http://www.herberg.name/downloads/pubs/CNSM_10.pdf
<blockedhttp://www.herberg.name/downloads/pubs/CNSM_10.pdf>
Interestingly, in that paper (and you will recognize the author), there is the
notion of proxy with the REPORT-MIB Sorry proxy or "Do you expect all MANET
routers to always have connectivity to a static NMS?"




		* etc...


	Can't address that one :-)


		Obviously, monitoring, for example, is important in ad-hoc networks, but
		please let us know how you envision doing this. For example, right now, I
		see the term "appropriate SNMP management stations", and I have no clue
		what's "appropriate" in the management of an ad-hoc network.


	Frankly, I don't think we have a good answer to what "appropriate" means in
any network. Again, I am not sure why a MANET is any different.

	But I agree that "appropriate" is a bad word and I should have let it through
my review. Perhaps this is a Comment?

Whether this is Comment or a Discuss is not relevant.
Let's not try to see every single line in this DISCUSS as a small thing to
fix... it seems to me that there is an elephant in the room.


At this point in time, I believe that a conf. with the authors would be more
beneficial

Regards, Benoit.






		I see some other MANET MIB modules...
		* draft-ietf-manet-olsrv2-mib-04 	Definition of Managed Objects for the
		Optimized Link State Routing Protocol
		* draft-ietf-manet-report-mib-02 	Definition of Managed Objects for
		Performance Reporting
		* draft-ietf-manet-smf-mib-04 	Definition of Managed Objects for the
		Manet Simplified Multicast Framework Relay Set
		However, this document is the first MANET MIB module to reach the IESG,
		so those operational questions are important.


	Agreed. The authors of those other documents are waiting on the review of
this document to help them with their work. The MIB Doctor review was much
anticipated. I agree that the answers to the questions you have raised are
equally applicable to the other documents. I think the lessons learned about
write access will be quickly applied to the other document. But I have some
trouble understanding the value of the other questions - I just can't
understand why a MANET is so dramatically different in your eyes.


		If this is expressed in a different document, let me know, and I can
		review it.


	There is no other document on the applicability of managing MANET devices.


		Along the same lines,
		1. see Al Morton's review, part of the OPS-DIR

			General question: Is a lossy, mobile ad-hoc network compatible with
			SNMPv3? In other words, will the link performance information needed
			for troubleshooting really be available when it is needed most, and
			critical nodes may be unreachable?


	Sorry, I have not seen Al's review.
	It looks like his question is "is it possible to run an IP-based application
over a MANET?"
	Answer: yes.


		2. Read Ron's Bonica's Abstain


	Read and discussed with Ron in person. Presuming you agree this part of your
Discuss is not actionable (or maybe the action is to read Ron's comment :o)


		COMMENT:
		----------------------------------------------------------------------

		- Abstract

		   This document defines a portion of the Management Information Base
		   (MIB) for use with network management protocols in the Internet
		   community.  In particular, it describes objects for configuring
		   parameters of the Neighborhood Discovery Protocol (NHDP) process on a
		   router.

		Should this be "MANET router"?
		"MANET router" is used in RFC6130
		Alternatively, I see in this document:
			"NHDP router"
			"router in a Mobile Ad Hoc Network (MANET)"
		Same remark for the introduction, which uses the same text.


	This can be cleaned up.


		- First occurence of NHDP must be expanded.


	It already is.






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