Re: [MIB-DOCTORS] AD review of draft-ietf-adslmib-vdsl2-06.txt

["Romascanu, Dan (Dan)" <[e-mail]>]

Well - at least I succeeded to trigger some more comments from you :-) 

If this is OK with you I will slightly edit and forward them to the
authors and WG. 

I will not hold the document further however. We have little bandwidth
and enthusiasm nowadays in reviewing MIBs. Several calls for volunteers
for a number of documents went unanswered. Everybody is doing work that
is more interesting and more important for their employers, and this is
fine, but we cannot hold documents forever in place waiting for MIB
advisors or for management application writers to review them. 

More opinions are welcome and more MIB reviews are especially welcome. 

Dan
 

> -----Original Message-----
> From: David Harrington [mailto:[e-mail]] 
> Sent: Thursday, January 22, 2009 8:01 PM
> To: Romascanu, Dan (Dan); 'MIB Doctors (E-mail)'
> Subject: RE: [MIB-DOCTORS] AD review of 
> draft-ietf-adslmib-vdsl2-06.txt
> 
> Hi Dan,
> 
> Wow! You need to take a closer look at this module.
> In the past I just looked at your comments and made some suggestions.
> (I was surprised to see a response to comments I forgot I 
> made.) I have not reviewed this module in depth. But their 
> responses made me look a little closer to understand what 
> they were doing.
> 
> Here are a few of my favorites:
> 
> 1) Xdsl2LineEntry  ::=
>    SEQUENCE {
>       xdsl2LineCnfgTemplate            SnmpAdminString,
>       xdsl2LineCnfgFallbackTemplate    SnmpAdminString,
>       xdsl2LineAlarmCnfgTemplate       SnmpAdminString,
>       xdsl2LineCmndConfPmsf            Xdsl2ConfPmsForce,
>       xdsl2LineCmndConfLdsf            Xdsl2LineLdsf,
>       xdsl2LineCmndConfLdsfFailReason  Xdsl2LdsfResult,
>       xdsl2LineCmndConfBpsc            Xdsl2LineBpsc,
>       xdsl2LineCmndConfBpscFailReason  Xdsl2BpscResult,
>       xdsl2LineCmndConfBpscReqCount    Unsigned32,
>       xdsl2LineCmndAutomodeColdStart   TruthValue,
>       xdsl2LineCmndConfReset           Xdsl2LineReset,
>       xdsl2LineStatusActTemplate       SnmpAdminString,
>       xdsl2LineStatusXtuTransSys       Xdsl2TransmissionModeType,
>       xdsl2LineStatusPwrMngState       Xdsl2PowerMngState,
>       xdsl2LineStatusInitResult        Xdsl2InitResult,
>       xdsl2LineStatusLastStateDs       Xdsl2LastTransmittedState,
>       xdsl2LineStatusLastStateUs       Xdsl2LastTransmittedState,
>       xdsl2LineStatusXtur              Xdsl2LineStatus,
>       xdsl2LineStatusXtuc              Xdsl2LineStatus,
>       xdsl2LineStatusAttainableRateDs  Unsigned32,
>       xdsl2LineStatusAttainableRateUs  Unsigned32,
>       xdsl2LineStatusActPsdDs          Integer32,
>       xdsl2LineStatusActPsdUs          Integer32,
>       xdsl2LineStatusActAtpDs          Integer32,
>       xdsl2LineStatusActAtpUs          Integer32,
>       xdsl2LineStatusActProfile        Xdsl2LineProfiles,
>       xdsl2LineStatusActLimitMask      Xdsl2LineLimitMask,
>       xdsl2LineStatusActUs0Mask        Xdsl2LineUs0Mask,
>       xdsl2LineStatusActSnrModeDs      Xdsl2LineSnrMode,
>       xdsl2LineStatusActSnrModeUs      Xdsl2LineSnrMode,
>       xdsl2LineStatusElectricalLength  Unsigned32,
>       xdsl2LineStatusTssiDs            Xdsl2Tssi,
>       xdsl2LineStatusTssiUs            Xdsl2Tssi,
>       xdsl2LineStatusMrefPsdDs         Xdsl2MrefPsdDs,
>       xdsl2LineStatusMrefPsdUs         Xdsl2MrefPsdUs,
>       xdsl2LineStatusTrellisDs         TruthValue,
>       xdsl2LineStatusTrellisUs         TruthValue,
>       xdsl2LineStatusActualCe          Unsigned32
>    }
> I love the abrreviations everywhere.
> Check out inconsistent abbreviations, such as 
> xdsl2LineCnfgFallbackTemplate which points to the 
> xdsl2LineConfTemplateTable. (cnfg and conf both mean 
> configuration) I note that RFC2662 uses "conf" consistently.
> 
> 2) I especially like the "you're screwed" counter - the 
> xdsl2LineCmndConfBpscReqCount let's management station M1 
> know when another management station M2 requested a 
> measurement, which caused the relevant counter to reset, such 
> that M1's measurement is no longer valid. 
>       "SNMP managers can use this attribute to check that the
>        measurement results retrieved by the manager where not 
>        interupted by another measurement request."
> 
> I thought we discouraged resetting counters in IETF MIB modules?
> Has this MIB been seriously reviewed by a MIB technical advisor?
> Has this MIB module been reviewed by any management 
> application designers?
> 
> 3) note the naming conventions for counters are not being 
> followed - xdsl2LineCmndConfBpscReqCount should probably be 
> xdsl2LineCmndConfBpscRequests.
> 
> 4) xdsl2LineCmndConfBpscReqCount - note that this counter is 
> not a Counter32, but an Unsigned32.
> 
> 5) I am a bit concerned about the table that actually 
> contains the measurement - the xdsl2LineSegmentTable  The 
> actual measurement is in xdsl2LineSegmentBitsAlloc. It 
> appears the value is overloaded to provide subcarrier 
> allocation status, as well as the result of a line diagnostic test. 
> 
> 6) from security consdierations "Unauthorized changes to 
> xdsl2LineCmndConfBpsc could cause an unscheduled bits per 
> subcarrier measurement to be carried out on the line.", and 
> "Unauthorized changes to xdsl2LineCmndConfLdsf could cause an 
> unscheduled line test to be carried out on the line." Since 
> these two measurements report using the same object, and 
> since one measurement can interfere with the validity of the 
> measurement requested by a different manager, this seems to 
> have serious issues of information reliability.
> 
> 7) On a larger scale, I am concerned that this appears to be a
> **competing** standard to RFC2662. This does not complement, 
> or update, or obsolete RFC2662.
> 
> I have not yet gone into the two mib modules to determine how 
> compatible they are, but section 4 in this document makes me 
> really uneasy as a (previous) management app designer. Can a 
> device support both mib modules simultaneously? Can a 
> manageent app use both MIB modules simultaneously to manage 
> the same ADSL functions on a device?
> 
> I note that rfc2662 does support using the entity mib, while 
> this mib module does not. Which makes me wonder about the 
> compatibility between the two mib modules.
> 
> 8) Per section 4, you need to go read G.997.1 to understand 
> the conformance requirements for this MIB module. G.997.1 
> appears to not be a free document.
> 
> --
> I am NOT volunteering to be the MIB Doctor for this document. 
> I have dealt with huge MIB modules before, especially ones 
> designed by people from another SDO (e.g., Printer MIB). They 
> are just way too painful to work though, with people 
> resistant to changes, and ADSL/VDSL is totally unrelated to 
> my day job.
> 
> But I think you need to have this MIB reviewed thoroughly, 
> because it looks to me like the designers do not have a good 
> understanding of how MIB modules should be designed for 
> interoperability with multiple simultaneous management apps, 
> and for usebaility by operators.
> 
> dbh
> 
> 
> > -----Original Message-----
> > From: [e-mail]
> > [mailto:[e-mail]] On Behalf Of Romascanu, Dan 
> > (Dan)
> > Sent: Thursday, January 22, 2009 9:38 AM
> > To: Moti Morgenstern; David B Harrington
> > Cc: MIB Doctors (E-mail); [e-mail]; Menachem Dodge; 
> > [e-mail]; [e-mail]
> > Subject: Re: [MIB-DOCTORS] AD review of 
> > draft-ietf-adslmib-vdsl2-06.txt
> > 
> > Hi Moti,
> > 
> > Your proposed resolution to the comments looks satisfactory to me. 
> > 
> > Please proceed with creating a revised version of this document
> which
> > could be sent to IETF LC. 
> > 
> > Thanks and Regards,
> > 
> > Dan
> >  
> > 
> > > -----Original Message-----
> > > From: Moti Morgenstern [mailto:[e-mail]]
> > > Sent: Sunday, November 09, 2008 4:53 PM
> > > To: Romascanu, Dan (Dan); David B Harrington
> > > Cc: MIB Doctors (E-mail); [e-mail]; Menachem Dodge; 
> > > [e-mail]; [e-mail]
> > > Subject: RE: AD review of draft-ietf-adslmib-vdsl2-06.txt
> > > 
> > > Hi Dan and David,
> > > 
> > > Thank you for the comments regarding to 
> > > draft-ietf-adslmib-vdsl2-06.txt.
> > > We, the editors, reviewed the comments and here is our 
> response to 
> > > each (Dan's comments and then David's):
> > > 
> > > Comment T1
> > > --------------
> > > Comment suggests writing specifically in the MIB module, in the 
> > > DESCRIPTION clauses of the MIB tables, what is the persistence 
> > > policy relative to the objects in the table.
> > > Response: We have a section in the document called "2.5.  
> > > Persistence" which lists all persistent objects. If you 
> search for 
> > > each of these objects in the MIB, not all of the objects mention 
> > > persistence in the DESCRIPTION clause. This is when the 
> persistency 
> > > is relevant to ALL objects and, when that happens, the 
> DESCRIPTION 
> > > clause of the containing table
> > > mentions: "Entries in this table MUST be maintained in a 
> persistent 
> > > manner." So we believe the current situation is satisfactory.
> > > 
> > > Comment T2
> > > --------------
> > > Comment claims that indexation by name is very resource consuming.
> > > Response: The observation is basically correct. Despite that, we 
> > > chose name indexes on purpose for ease of use by the operator and 
> > > consistency with all other xDSL MIBs.
> > > 
> > > Comment T3
> > > --------------
> > > Comment refers to rate-limiting notifications mentioned in the 
> > > document.
> > > Response: We will remove the rate limiting comment altogether 
> > > because no other xDSL MIB mentions this.
> > > 
> > > Comment T4
> > > --------------
> > > Comment is a request to explain the Reserved bits in 
> > > Xdsl2TransmissionModeType.
> > > Response: We used reserved bits because we want the VDSL2 MIB to 
> > > closely match the source document G.997.1.
> > > 
> > > Comment T5
> > > --------------
> > > Comment about the Textual Conventions with enumerated 
> INTEGER syntax 
> > > in which the list of values starts from zero.
> > > Response: Similar to T4 above this was done on purpose. 
> We want the 
> > > MIB to closely match the source document G.997.1 which already 
> > > defines the range of enumerated values for many attributes. Since 
> > > the syntax allows that we don't see it necessary to explain such 
> > > considerations in the MIB.
> > > 
> > > Comment T6
> > > --------------
> > > Comment about the Boolean objects with new TCs instead of using 
> > > TruthValue
> > > Response: We use TruthValue for 10 objects in the MIB, 
> so, it's not 
> > > that we are not familiar with that TC. The real reason, again, is 
> > > that G.997.1 specifically defines the range of values and meaning 
> > > for many attributes and our MIB follows it as much as we could.
> > > 
> > > Taking the Textual Conventions mentioned in this comment as
> > examples:
> > > Xdsl2LineLdsf- G.997.1 uses the value 0 to inhibit LDSF and 1 for 
> > > forcing LDSF. We preferred explicitly using those values.
> > > Xdsl2LineCeFlag- CEFLAG is defined by G.997.1 as a bitmap with a 
> > > single bit. So, the values range is 0 and 1.
> > > Xdsl2LineSnrMode-TruthValue uses the value 1 for true and 2 for 
> > > false, while G.997.1 uses 1 for disable and 2 for enable.
> > > 
> > > There is still one TC (Xdsl2LineForceInp) that could be 
> replaced by 
> > > the TruthValue. This will be performed.
> > > 
> > > Comment T7
> > > --------------
> > > Comment regarding to using RowStatus only to delete rows
> > > Response: We'll add text in the relevant DESCRIPTION clauses to 
> > > explain that the agent rejects any SET operation which sets row 
> > > status to a value other than delete(6)
> > > 
> > > Comment T8
> > > --------------
> > > Comment: why not replace inventory information in 
> > > Xdsl2LineInventoryEntry with entPhysicalTable in RFC4133
> > > Response: There are several arguments against the idea. 
> > > However, the most important one is that we need to provide the 
> > > inventory for both near-end and far-end units and that means two 
> > > rows per each ifIndex. So, we cannot use RFC4133 for inventory 
> > > because the indexing scheme is inappropriate.
> > > 
> > > Comment T9
> > > --------------
> > > Comment: what happens when row is validated, etc.
> > > Response: We agree that there's a need to perform several 
> changes in 
> > > the DESCRIPTION clause of row-status objects. This will include 
> > > removing the text about validating the row content (i.e., as we 
> > > cannot explain how we expect the implementation to 
> perform that) as 
> > > well as giving more information regarding to deleting a 
> "referenced" 
> > > row.
> > > 
> > > Comment T10
> > > --------------
> > > Comment requests explanation about how the thresholds in the 
> > > xdsl2ChAlarmConfProfileTable are being applied
> > > Response: First of all, RFC3705 includes TCs and we use 
> one of them 
> > > in the referred table. Second, we suggest to add a text 
> in the top 
> > > part of the document explaining that only one threshold trap per 
> > > interval will be issued once the individual counter exceeds the 
> > > threshold defined for it. Is that acceptable?
> > > 
> > > Comment T11
> > > --------------
> > > Comment suggests that the compliance should be function of the 
> > > flavor(s) of xDSL an agent implements.
> > > Response: The MODULE-COMPLIANCE section applies to all technology 
> > > types: VDSL2/ADSL/ADSL2 and ADSL2+. The assumption of G.997.1 is 
> > > that a typical implementation supports a mixture of 
> technologies and 
> > > transmission modes, not a single selected one, and that's why the 
> > > abstract attribute was originally defined as a bit map 
> rather than 
> > > an enumeration of modes. The idea is that a typical 
> operator wishes 
> > > to serve all transmission modes supported by the remote 
> units so he 
> > > prepares, for each service package, a setup that can satisfy 
> > > multiple use cases.
> > > Theoretically, Most of the MIB attributes are relevant 
> for all or at 
> > > least multiple xDSL technologies. There are still several 
> which are 
> > > relevant for a specific technology. We didn't want to 
> complicate the 
> > > compliance section because otherwise we would also need to handle 
> > > attributes that are sometimes mandatory and sometimes 
> optional (and 
> > > what happens when you have a mixed scenario..?). So, we 
> believe an 
> > > agent implementation should conform to the compliance clause but 
> > > also consult with ITU-T G.997.1 to see exactly what is required 
> > > depending on the mixture of the various transmission 
> modes relevant 
> > > for the specific operator.
> > > 
> > > Comment E1
> > > --------------
> > > Comment: s/ a more comprehensive/a complementary/
> > > Response: The ADSL2 MIB is recommended for 
> implementations that do 
> > > not implement VDSL2 and do not want to be affected by it 
> at all. The 
> > > NG-xDSL MIB (this draft) has a wider scope of technologies and is 
> > > recommended for implementations of VDSL2 (only VDSL2 or together 
> > > with older DSL technologies) and are ready to pay the 
> "price". The 
> > > "price" is expressed in various ways, e.g., the need to implement 
> > > the "subcarrier group"
> > > related attributes for DELT also for ADSL/2/2+, although those 
> > > attributes are meaningful only in VDSL2.
> > > So the new MIB is not a complementary one but a solution for the 
> > > same problem space, only with a wider set of DSL technologies.
> > > 
> > > Comment E2
> > > --------------
> > > Comment: list of abbreviations
> > > Response: OK
> > > 
> > > Comment E3
> > > --------------
> > > Comment: Section 2.3.2 duplicates text from the TC-MIB module
> itself
> > > Response: OK. We'll delete it.
> > > 
> > > Comment E4
> > > --------------
> > > Comment: page 28 - s/This MIB allows supporting/This MIB module 
> > > allows supporting
> > > Response: OK.
> > > 
> > > Comment E5
> > > --------------
> > > Comment: page 31 - s/ Network Elements may /Network Elements MAY/ 
> > > and s/The xTU-C should / The xTU-C SHOULD/
> > > Response: OK.
> > > 
> > > Comment E6
> > > --------------
> > > Comment: In SMIv2 we do not usually speak about 
> attributes but about 
> > > objects
> > > Response: We'll correct the relevant text.
> > > 
> > > Comment E7
> > > --------------
> > > Comment: DESCRIPTION clause of the MIB module duplicates 
> text in the 
> > > Overview section
> > > Response: We'll use a short summary in the overview section and a 
> > > full description in the MIB module.
> > > 
> > > Comment E8
> > > --------------
> > > Comment: 'an ifType of vdsl(xxx)'. It is good to add at 
> least at the 
> > > first occurrence a note to the RFC Editor
> > > Response: OK.
> > > 
> > > Comment E9
> > > --------------
> > > Comment: The DESCRIPTION clauses of Valid Intervals and Invalid 
> > > Intervals are almost void
> > > Response: We'll fill the DESCRIPTION clauses for these objects
> > > 
> > > Comment E10
> > > --------------
> > > Comment: Section 4 would benefit from one or two examples of 
> > > configuration templates
> > > Response: We prefer not to add any additional tutorial 
> material into 
> > > the VDSL2 draft MIB.
> > > 
> > > 
> > > Comments from David B Harrington
> > > --------------------------------
> > > 
> > > Comment: "One suggestion would be to put the 
> VDSL2-LINE-TC-MIB in a 
> > > separate document."
> > > Response: This would require 2 RFC numbers for VDSL2 and we don't 
> > > like it. We also have an experience from RFC4706 and the 
> draft ANCP 
> > > AN MIB (draft-ietf-ancp-mib-an-03) that have the same 
> structure as 
> > > this draft.
> > > 
> > > Comment:"I strongly support Dan's request to eliminate 
> some of the 
> > > redundancy in this document, and I recommend starting with the 
> > > textual convention triplication. You can probably save 30% of the 
> > > document length getting rid of unnecessary textual convention 
> > > definitions."
> > > Response: We have no real objection to removing the TCs that are 
> > > referenced only once and placing the definition in the object 
> > > definition. Is that also agreed by Dan? Any comment from the WG 
> > > members?
> > > 
> > > Comment: "It might be good to have a manageability considerations 
> > > section that discusses using short strings and internal 
> choices to 
> > > minimize the resource impact."
> > > Response: We don't think this is necessary.
> > > 
> > > Dan and David, Thanks again for your time and your comments.
> > > 
> > > On behalf of the co-editors,
> > > Moti Morgenstern
> > > 
> > _______________________________________________
> > MIB-DOCTORS mailing list
> > [e-mail]
> > https://www.ietf.org/mailman/listinfo/mib-doctors
> > 
> 
> 
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