Re: [IPFIX] review of draft-ietf-ipfix-mib-variable-export-07

Juergen Schoenwaelder <j.schoenwaelder@jacobs-university.de> Mon, 05 January 2015 15:19 UTC

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Date: Mon, 5 Jan 2015 16:19:41 +0100
From: Juergen Schoenwaelder <j.schoenwaelder@jacobs-university.de>
To: Paul Aitken <paitken@Brocade.com>
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Subject: Re: [IPFIX] review of draft-ietf-ipfix-mib-variable-export-07
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Paul,

I think the example should either be a real-world example or there
needs to be a clear warning somewhere that this example is not a
real-world example in order to prevent people from coding along the
example and then coming up with ideas such as white space padding
interface names to make them fixed-length 16 octets long. There are
programmers who code along examples instead of reading the underlying
specifications and they sometimes end up being (too) creative.

I guess my preference is to show a realistic example but if I am the
only one, then of course I will go along with what we have (but I
would appreciate that there is a warning somewhere that this example
makes simplifying assumptions).

/js

On Mon, Jan 05, 2015 at 11:09:14AM +0100, Paul Aitken wrote:
> Juergen, thanks for your careful review and all your feedback. I've addressed all your points except one:
> 
>     - p46: Why is the Field Length of mibObjectValueOctetString set to 16?
>            The interface names in general have variable length.
> 
> Fixed length is used to simplify the example data record in figure 31.
> 
> Although interfaces generally do have variable length names, I believe the example is clearer with fixed length fields.
> 
> Changing to variable length would be straightforward if the consensus is that it's more realistic example.
> 
> P.
> 
> 
> > -----Original Message-----
> > From: IPFIX [mailto:ipfix-bounces@ietf.org] On Behalf Of Juergen Schoenwaelder
> > Sent: 17 December 2014 14:19
> > To: ipfix@ietf.org
> > Subject: [IPFIX] review of draft-ietf-ipfix-mib-variable-export-07
> > 
> > Hi,
> > 
> > here is my review of draft-ietf-ipfix-mib-variable-export-07. Most of the
> > comments are editorial or bug fixes. There is only one real technical concern
> > related to the encoding of BITS. The current I-D uses a 64-bit unsigned integer,
> > which limits things to 64 bit positions. The SMIv2 does not have this limit - it only
> > warns about bit positions in excess of 128.
> > 
> > - RFC4293 is listed as a normative reference but as far as I can tell
> >   it is only used in an example. I suggest to make this an informative
> >   reference.
> > 
> > - p3: 2nd paragraph Introduction: I am not sure the statement "there
> >   are no dependencies between the SMIv2 and the SNMP protocol" is
> >   correct.  Perhaps the simplest fix is to simply delete the whole
> >   paragraph.
> > 
> > - p4: 1st paragraph Motivation: The 2nd sentence is hard to follow.
> > 
> > - p5: s/does not specify SNMP notifications/does not specify how to
> >   carry SNMP notifications in IPFIX/
> > 
> > - p9: s/in a certain MIB/in a certain MIB module/
> > 
> > - p10: s/may be also be/may also be/
> > 
> > - p10: s/described by the MIB./described by the MIB module./
> > 
> > - p14: s/when when/when/
> > 
> > - p14: s/references sections/referenced sections/
> > 
> >   The fact that every listed item refers to two sections may be a bit
> >   confusing, perhaps change to
> > 
> >   o  mibIndexIndicator (defined in Section 5.8.5, example in Section 11.2.2.3)
> > 
> > - p20: It took me a while to spot the difference between Fig. 7 and
> >   Fig.8 (I did not immediately spot that the fields are
> >   swapped). Perhaps mention this more explicitly in the last paragraph
> >   on p19?
> > 
> >      Figure 7 shows an IPFIX Options Template Set using Scope Existing
> >      IFPIX IE and a Non Scope mibObjectValueInteger IE, while Figure 8
> >      shows an IPFIX Options Template Set using a Scope
> >      mibObjectValueInteger IE and a Non Scope Existing IFPIX IE.
> > 
> > - p12: s/name of the MIB/name of the MIB module/
> > 
> > - p26: s/present the same order/present in the same order/
> > 
> > - p32: s/not defined as possible/not possible/
> > 
> > - p37: s/CISCO-PROCESS_MIB/CISCO-PROCESS-MIB/
> > 
> > - p45: s/ifMTU/ifMtu/ (this shows up several time, do a global replace)
> > 
> > - p46: Why is the Field Length of mibObjectValueOctetString set to 16?
> >        The interface names in general have variable length.
> > 
> > - p47: why 'ifName = ""'?
> > 
> > - p52: s/index by IEs:/indexed by IEs:/
> > 
> > - p58: The VLEN and the OID value seem to be wrong. I think this should
> >        be VLEN=10 and the OID value 06082B060102010E0A01.
> > 
> > - p61: I would have named SNMPtotalCounter simply snmpCounter and I
> >        would have named SNMPgauge snmpGauge. If this change is
> >        adopted, then these names needs to be changed in several
> >        places.
> > 
> > - p64: The encoding of mibObjectValueBits may need to specify how the
> >        bit positions are counted. That said, there is an issue here
> >        with using unsigned64. RFC 2578 does not restrict the bit
> >        positions, it only warns that using bit positions in excess of
> >        128 may cause interoperability problems. The IPFIX I-D
> >        essentially limits this to 64 bits. The obvious solution is to
> >        follow the SNMP encoding rules that encode bits into an octet
> >        string (an octetArray in IPFIX speak).
> > 
> > - p67: s/as defined in a MIB//
> > 
> > - p68: OLD
> > 
> >        Description: A non-negative sub-identifier.  One Sub number from
> >        an Object Identifier (OID).
> > 
> >        NEW
> > 
> >        Description: A non-negative sub-identifier of an Object
> >        Identifier (OID).
> > 
> > - p69: s/was retrieved from SNMP/was retrieved from the MIB/
> > 
> > - p70: s/could be sampled by SNMP/has been sampled/
> > 
> > - p70: s/SNMP sampling time/sampling time/
> > 
> > /js
> > 
> > --
> > Juergen Schoenwaelder           Jacobs University Bremen gGmbH
> > Phone: +49 421 200 3587         Campus Ring 1, 28759 Bremen, Germany
> > Fax:   +49 421 200 3103         <http://www.jacobs-university.de/>
> > 
> > _______________________________________________
> > IPFIX mailing list
> > IPFIX@ietf.org
> > https://www.ietf.org/mailman/listinfo/ipfix

-- 
Juergen Schoenwaelder           Jacobs University Bremen gGmbH
Phone: +49 421 200 3587         Campus Ring 1, 28759 Bremen, Germany
Fax:   +49 421 200 3103         <http://www.jacobs-university.de/>