Path Computation Element Communication Protocol (PCEP) Management Information Base (MIB) Module
draft-ietf-pce-pcep-mib-11

IESG/Authors/WG Chairs:

IANA has reviewed draft-ietf-pce-pcep-mib-10.  Please report any inaccuracies and respond to any questions as soon as possible.

IANA's reviewer has the following comments/questions:

IANA understands that, upon approval of this document, there is a single action which IANA must complete.

In the SMI Network Management MGMT Codes Internet-standard MIB registry (iso.org.dod.internet.mgmt.mib-2 [1.3.6.1.2.1]) at

http://www.iana.org/assignments/smi-numbers

a new MIB will be registered as follows:

Decimal: [ TBD by IANA at time of registration ]
Name: pcePcepMIB
Description: Path Computation Element Communications Protocol
References: [ RFC-to-be ]

Note:  The actions requested in this document will not be completed until the document has been approved for publication as an RFC. This message is only to confirm what actions will be performed.

The following Last Call announcement was sent out:

From: The IESG
To: IETF-Announce
CC:
Reply-To: ietf@ietf.org
Sender:
Subject: Last Call:  (Path Computation Element Communications Protocol (PCEP) Management Information Base (MIB) Module) to Proposed Standard


The IESG has received a request from the Path Computation Element WG
(pce) to consider the following document:
- 'Path Computation Element Communications Protocol (PCEP) Management
  Information Base (MIB) Module'
  as Proposed Standard

The IESG plans to make a decision in the next few weeks, and solicits
final comments on this action. Please send substantive comments to the
ietf@ietf.org mailing lists by 2014-10-13. Exceptionally, comments may be
sent to iesg@ietf.org instead. In either case, please retain the
beginning of the Subject line to allow automated sorting.

Abstract

  This memo defines a portion of the Management Information Base (MIB)
  for use with network management protocols in the Internet community.
  In particular, it describes managed objects for modeling of Path
  Computation Element communications Protocol (PCEP) for communications
  between a Path Computation Client (PCC) and a Path Computation
  Element (PCE), or between two PCEs.

The file can be obtained via
http://datatracker.ietf.org/doc/draft-ietf-pce-pcep-mib/

IESG discussion can be tracked via
http://datatracker.ietf.org/doc/draft-ietf-pce-pcep-mib/ballot/


No IPR declarations have been submitted directly on this I-D.

AD review
======

Hello authors,

This is very substantial and detailed piece of work. Many thanks for
the considerable effort it represents.

I have done my usual AD review of this document in order to process the
publication request. The purpose of the review is to catch any issues
that might otherwise show up in IETF last call or IESG review, and to
ensure that I can fully support the document.

I'm glad to hear that there are implementations underlying this work and
that should be used as a moderating influence on my comments and
questions. For many of the points I raise it may be OK to answer "We
have thought about it, but this is how we chose to implement it."

Please look through the comments and let me know your thoughts either by
providing a new revision, or by answering via email.

Thanks for the work,
Adrian

=====

Section 1 para 2

  The PCE communication protocol (PCEP)

The convention these days seems to be "Path Computation Element
Communications Protocol" or "Path Computation Element communications
Protocol".

You might apply that to the document title as well.

---

Section 1

  The PCE communication protocol (PCEP) is the communication protocol
  between a PCC and PCE for point-to-point (P2P) path computations and
  is defined in [RFC5440].

That reference to P2P seemed odd to me. Any reason to include it?
In particular, nothing in this module appears to be specific to whether
P2P or P2MP request are being supported.

---

That previous point does cause me to wonder about "PCE capabilities".
I can see that you have tried to limit this module to describing the
features that are core to 5440, but I wonder whether that is wise.

For example, RFCs 5088 and 5089 define a set of PCE capabilities that
may be advertised in the IGPs and are surely relevant to the model of
a PCE that speaks PCEP. That information might usefully be seen in the
module at the PCE, and also at the PCC so that an operator can check
"why does that PCC keep sending these requests to the wrong PCE?"

Similarly, the Open Object can carry TLVs that indicate further
capabilities. Obviously you can't just include all future capabilities
TLVs since you don't know what they are (well, you know some, but that
have already been defined, but you can't know the undefined ones). But
you might want to to look at how those capabilities will be hooked in
for future accessibility.

Of particular interest will be the OF-list TLV of RFC 5541.

---

Convention has it that you have written a "MIB module" which is part of
"the MIB", so can you look through the document and mainly change "MIB"
to "MIB module".

---

I'm wondering under what circumstances the pcepEntityTable has more than
one entry. You might describe that in 4.1 and also in the Description
clause for the table.

That would tie in with explaining why you have an index of
Unsigned32 (1..2147483647) which allows for quite a lot of entities!

For a moment I thought that maybe there would be one entry when acting
as PCE and one when acting as PCC (i.e., a max of 2 < 2147483647) but
there is no mode field in the entityTable, only the peerTable.

Actually, I'm a bit confused about the indexing of the three tables.
I think you think that every PCE and PCC in the network shows in the
entityTable. But that isn't how you have set up the entityTable to
contain information that is about the local PCEP entity/entities. So
my confusion...

Now, looking at the indexes to pcePcepPeerTable. There are two
questions.

1. Why do you use pcePcepEntityIndex as an index? It points back into
  entityTable which we have established is basically the local PCEP
  speaker or which there is probably just one.

  The text in 4.2 says...

      The pcePcepPeerTable contains one row for each PCEP peer that the
      PCEP entity (PCE or PCC) knows about.

  I think your intention is that pcePcepEntityIndex is different for
  each peer. But pcePcepEntityIndex is the index to PcePcepEntityTable
  which is full of local PCEP entity information and (I suspect) will
  only ever have one entry.

  Shouldn't the peerTable have its own unique index for each peer?

2. Making pcePcepPeerAddrType and pcePcepPeerAddr indexes as well would
  appear to allow two or more entries for the same peer with different
  addresses.

  Is that the intention? If so, you might make it clear in section 4.2.
  And you would also need to make clear that there is an expectation
  that an implementation will assign the same value of
  pcePcepEntityIndex (or the new per-peer index) to each table entry
  that represents the same peer.

  OTOH, if a peer has multiple addresses, will this allow you to have
  multiple sessions to the same peer. Is that what you intended?

  Alternatively, it seems unlikely that two different peers will have
  the same address. So why is any additional index (i.e.,
  pcePcepEntityIndex) needed?

The same questions apply to the indexing of pcePcepSessTable although
pcePcepSessInitiator is understandable.


The solution to all this will be:
- Decide how many entries you really expect in entityTable.
- Decide whether entries in peerTable and sessTable should be indexed
  from entityTable, or with an index from peerTable.

---

A small worked example would be cool (either between Sections 4 and 5,
or in an Appendix).  I would draw a figure such as:

    PCE1---PCE2  PCE3
      |  /  |    /  |
      |  /  |  /  |
    PCCa/    PCCb  PCCc

...and give an example of the module as read at PCE2 and PCCb.

---

The OID structure is unusual. I'm not saying it is wrong, but it is
different around pcePcepObjects. It would probably help to include a
diagrammatic representation. I think you have something like the
following.

(BTW, the "unusual" is the additional indirection between pcePcepObjects
and the various tables.)

  mib-2
  |
  |--- XXX pcePcepMIB
          |
          |--- 0 pcePcepNotifications
          |      |
          |      |--- 1 pcePcepSessUp
          |      :    :
          |
          |--- 1 pcePcepObjects
          |      |
          |      |--- 1 pcePcepEntityObjects
          |      |      |
          |      |      |--- 1 pcePcepEntityTable
          |      |
          |      |--- 2 pcePcepPeerObjects
          |      |      |
          |      |      |--- 1 pcePcepPeerTable
          |      |
          |      |--- 3 pcePcepSessObjects
          |            |
          |            |--- 1 pcePcepSessTable
          |
          |--- 2 pcePcepConformance
                  |
                  |--- 1 pcePcepCompliances
                  |--- 2 pcePcepGroups

---

I'd also like to see a short section (probably just containing a figure)
that shows the relationship between the three tables in this module.

It can't be complex (there are only three tables!), but a figure that
shows which objects in which tables lead you to find rows in other
tables would be a help. And where the relationship is shared indexes or
augmentation that can be called out.

---

I am quite happy that this module is entirely read-only. But it makes
some of the "usual" objects a little odd without additional information
in their Description clauses. For example, pcePcepEntityAdminStatus says
  "The administrative status of this PCEP Entity."
That is fine, but what does it mean?
You could probably add:
  "... This is the desired operational status as currently set by an
  operator or by default in the implementation. The value of
  pcePcepEntityOperStatus represents the current status of an attempt
  to reach this desired status."

---

I like the values you have offered in pcePcepEntityOperStatus
A common accompaniment to the failure cases (and maybe the inactive /
deactivating cases) is an unformatted reason string. Did you consider
adding one of these?

---

Do you support values of pcePcepEntityAddrType other than ipv4(1) and
ipv6(2)?

Maybe unknown(0) is used when pcePcepEntityAddr has not been set up?

If there is some limit on the full range of values from the Syntax
InetAddressType you should:
- say so in the Description clause
- say so in the Conformance statement.

That will make the text in pcePcepEntityAddr easier to cope with
unchanged.

---

Just asking...

Is there a value of pcePcepEntityConnectTimer that means "never give
up"?  You could use zero if you wanted to, but you don't have to.
(18 hours is probably long enough.)

---

Similar for pcePcepEntityConnectMaxRetry
Is there a value that means continue indefinitely?
Although 2^32 attempts sounds like quite a few.

The Description for this object says "...before going back to the Idle
state."  Could you reference that back to an object (presumably in the
peerTable since the entry in the sessTable does not exist in idle state)
and the associated value.

---

pcePcepEntityOpenWaitTimer same question about "wait forever".

Also, perhaps clarify that this is the time after the TCP connection has
come up.

I know the protocol spec makes this clear, but "...aborts the session
setup attempt" could be enhanced with "...terminates the TCP connection
and removes the associate entry from the sessTable"

---

            pcePcepEntityDeadTimer is recommended to be 4 times the
            pcePcepEntityKeepAliveTimer value.

I don't think that giving this advice is helpful since this object is
read-only and can only report the configured (through other means)
value.

---

  pcePcepEntityMaxDeadTimer
      DESCRIPTION
          "The maximum value that this PCEP entity will accept from a
            peer for the Dead timer.  Zero means that the PCEP entity
            will allow not running a Dead timer.

            A Dead timer will not be accepted unless it is both greater
            than the session Keepalive timer and less than this field."

Are you sure? Where does a zero Dead timer fit with that statement?

---

pcePcepEntityAllowNegotiation seems out of order in amidst the various
timer objects. Not important, but odd.

---

  pcePcepEntityMinDeadTimer OBJECT-TYPE
      DESCRIPTION
          "In PCEP session parameter negotiation, the minimum value
            that this PCEP entity will accept for the Dead timer.  Zero
            means that the PCEP entity insists on not running a Dead
            timer.

            A Dead timer will not be accepted unless it is both greater
            than the session Keepalive timer and greater than this
            field."

Again, the second paragraph seems to conflict with the use of zero.

---

pcePcepEntitySyncTimer needs to clarify that this object only has
meaning if the entity is a PCE.

So you should give a value that a PCC can return in this object, or
say that a PCC should not return this object.

Furthermore, the syncTimer is only recommended in RFC 5440. How should
an implementation that does not implement a syncTimer return this
object?

---

The backoff timer objects (pcePcepEntityInitBackoffTimer and
pcePcepEntityMaxBackoffTimer) might be better grouped next to the
other session-related timers (especially the OpenTimer).

---

  pcePcepEntityMaxUnknownReqs OBJECT-TYPE
      DESCRIPTION
          "The maximum number of unrecognized requests and replies that
            any session on this PCEP entity is willing to accept per
            minute.


  pcePcepEntityMaxUnknownMsgs OBJECT-TYPE
      DESCRIPTION
          "The maximum number of unknown messages that any session
            on this PCEP entity is willing to accept per minute."


...before doing what?


---

Same issue wrt pcePcepPeerAddrType as for pcePcepEntityAddrType

---

In pcePcepPeerRole it might be more usual to have unknown(0).

---

It is not clear (to me) whether pcePcepPeerNumSessSetupFail is
incremented each time a retry fails or only each time a session
set-up attempt is abandoned.

---

  pcePcepPeerSessionFailTime
      DESCRIPTION
          "The value of sysUpTime the last time a session with this
            peer failed to be established.

This is consistent with other fields, but does not record a session
that was up, but then failed.

---

Now, I'll grant that pcePcepEntityMaxUnknownMsgs allows for a remarkably
high rate of receipt of unknown messages with...
      SYNTAX      Unsigned32
      DESCRIPTION
          "The maximum number of unknown messages that any session
            on this PCEP entity is willing to accept per minute."

But, given that rate, it seems that pcePcepPeerNumUnknownRcvd could
overflow within just one minute.
      SYNTAX      Counter32
      DESCRIPTION
          "The number of unknown messages received from this peer."

The same is going to apply to pcePcepEntityMaxUnknownReqs and
pcePcepPeerNumReqRcvdUnknown.

Also, of course, the same applies to the counters in the sessTable.

---

Many of the same comments apply to the objects in the sessEntry as
applied to the peerEntry and entityEntry, and I won't repeat them here.

---

I don't think pcePcepSessOverloadTime and pcePcepSessPeerOverloadTime
are very useful. The values are presumably stored from sent or received
OVERLOADED-DURATION TLVs in PCNtf messages that indicate 'Overloaded'.

However, if I come and look at the object some time later I have no idea
how much longer the overloaded state may last.

I think you need (I use the peer as an example)

pcePcepSessPeerOverload          TruthValue
  Whether or not this peer is overloaded.
pcePcepSessPeerLastOverloaded    Timestamp
  Time at which last overload event occurred for this peer.
  Not cleared when pcePcepSessPeerOverload becomes false.
pcePcepSessPeerLastOverloadTime  Unsigned32
  Duration of last overload event for this peer.
  Not cleared when pcePcepSessPeerOverload becomes false.

---

Although this is carefully a read-only MIB module, I wonder whether you
need a way to quiesce the Notifications issued by an implementation.

Something like...

  pcePcepNotificationsMaxRate OBJECT-TYPE
      SYNTAX      Unsigned32
      MAX-ACCESS  read-write
      STATUS      current
      DESCRIPTION
          "This variable indicates the maximum number of
            notifications issued per second. If events occur
            more rapidly, the implementation may simply fail to
            emit these notifications during that period, or may
            queue them until an appropriate time. A value of 0
            means no notifications are emitted and all should be
            discarded (i.e., not queued)."

...or...

  pcePcepNotificationsEnable OBJECT-TYPE
      SYNTAX        TruthValue
      MAX-ACCESS    read-write
      STATUS        current
      DESCRIPTION
          "If this object is true, then it enables the
            generation of notifications."

Without one of these, your management station will be bombed with
Notifications from the PCCs in the network.

As required by RFC 4858, this is the current template for the Document
Shepherd Write-Up.

Changes are expected over time. This version is dated 24 February 2012.

(1) What type of RFC is being requested (BCP, Proposed Standard,
Internet Standard, Informational, Experimental, or Historic)?
-> PS
Why is this the proper type of RFC?
-> MIB specification
Is this type of RFC indicated in the title page header?
-> Yes (ST)

(2) The IESG approval announcement includes a Document Announcement
Write-Up. Please provide such a Document Announcement Write-Up. Recent
examples can be found in the "Action" announcements for approved
documents. The approval announcement contains the following sections:

Technical Summary

  This memo defines a portion of the Management Information Base for
  use with network management protocols in the Internet community.  In
  particular, it describes managed objects for modeling of Path
  Computation Element communication Protocol (PCEP) for communications
  between a Path Computation Client (PCC) and a Path Computation
  Element (PCE), or between two PCEs.

Working Group Summary

  Was there anything in WG process that is worth noting?
-> Moving to YANG modules has been discussed.
  For example, was there controversy about particular points or
  were there decisions where the consensus was particularly
  rough?
-> No

Document Quality

  Are there existing implementations of the protocol?
-> Yes (but not a protocol)
  Have a significant number of vendors indicated their plan to
  implement the specification?
-> Not really significant
  Are there any reviewers that
  merit special mention as having done a thorough review,
  e.g., one that resulted in important changes or a
  conclusion that the document had no substantive issues?
-> Juergen Schoenwaelder: "The document is in a pretty good shape. [...] well put together"
  If there was a MIB Doctor, Media Type or other expert review,
  what was its course (briefly)?
-> Review by MIB Doctor (Juergen)
  In the case of a Media Type review, on what date was the request posted?
-> N/a

Personnel

  Who is the Document Shepherd?
-> Julien Meuric
  Who is the Responsible Area Director?
-> Adrian Farrel

(3) Briefly describe the review of this document that was performed by
the Document Shepherd.  If this version of the document is not ready
for publication, please explain why the document is being forwarded to
the IESG.
-> Looks ready for publication

(4) Does the document Shepherd have any concerns about the depth or
breadth of the reviews that have been performed? 
-> No

(5) Do portions of the document need review from a particular or from
broader perspective, e.g., security, operational complexity, AAA, DNS,
DHCP, XML, or internationalization? If so, describe the review that
took place.
-> No

(6) Describe any specific concerns or issues that the Document Shepherd
has with this document that the Responsible Area Director and/or the
IESG should be aware of? For example, perhaps he or she is uncomfortable
with certain parts of the document, or has concerns whether there really
is a need for it. In any event, if the WG has discussed those issues and
has indicated that it still wishes to advance the document, detail those
concerns here.
-> N/a

(7) Has each author confirmed that any and all appropriate IPR
disclosures required for full conformance with the provisions of BCP 78
and BCP 79 have already been filed. If not, explain why.
-> Yes

(8) Has an IPR disclosure been filed that references this document?
If so, summarize any WG discussion and conclusion regarding the IPR
disclosures.
-> No

(9) How solid is the WG consensus behind this document? Does it
represent the strong concurrence of a few individuals, with others
being silent, or does the WG as a whole understand and agree with it?
-> WG members interested in MIBs agree

(10) Has anyone threatened an appeal or otherwise indicated extreme
discontent? If so, please summarise the areas of conflict in separate
email messages to the Responsible Area Director. (It should be in a
separate email because this questionnaire is publicly available.)
-> No

(11) Identify any ID nits the Document Shepherd has found in this
document. (See http://www.ietf.org/tools/idnits/ and the Internet-Drafts
Checklist). Boilerplate checks are not enough; this check needs to be
thorough.
-> Kiran Koushik's address needs to be updated
(kirankoushik.agraharasreeniv@gmail.com)

(12) Describe how the document meets any required formal review
criteria, such as the MIB Doctor, media type, and URI type reviews.
-> MIB specification, thus MIB Doctor review performed by Juergen

(13) Have all references within this document been identified as
either normative or informative?
-> Yes

(14) Are there normative references to documents that are not ready for
advancement or are otherwise in an unclear state? If such normative
references exist, what is the plan for their completion?
-> No

(15) Are there downward normative references references (see RFC 3967)?
If so, list these downward references to support the Area Director in
the Last Call procedure.
-> No

(16) Will publication of this document change the status of any
existing RFCs? Are those RFCs listed on the title page header, listed
in the abstract, and discussed in the introduction? If the RFCs are not
listed in the Abstract and Introduction, explain why, and point to the
part of the document where the relationship of this document to the
other RFCs is discussed. If this information is not in the document,
explain why the WG considers it unnecessary.
-> No

(17) Describe the Document Shepherd's review of the IANA considerations
section, especially with regard to its consistency with the body of the
document. Confirm that all protocol extensions that the document makes
are associated with the appropriate reservations in IANA registries.
-> OK
Confirm that any referenced IANA registries have been clearly
identified.
-> OK
Confirm that newly created IANA registries include a
detailed specification of the initial contents for the registry, that
allocations procedures for future registrations are defined, and a
reasonable name for the new registry has been suggested (see RFC 5226).
-> N/a

(18) List any new IANA registries that require Expert Review for future
allocations. Provide any public guidance that the IESG would find
useful in selecting the IANA Experts for these new registries.
-> N/a

(19) Describe reviews and automated checks performed by the Document
Shepherd to validate sections of the document written in a formal
language, such as XML code, BNF rules, MIB definitions, etc.
-> http://www.simpleweb.org/ietf/mibs/validate/