Tom Taylor
On 12/12/2014 9:40 AM, Elwyn Davies wrote:
Hi, Sam. Thanks for the responses. On the subject of SNMP write, I understand that agreement has been reached that the the MIB should effectively adopt the same position as RFC 3812, i.e. having read/write etc. objects and describing the use of the MIB for configuration in the examples. I suggest that para 3 of s1 is rewritten to make this a bit clearer what the position is and also to explain what the phrase "as a way to provide the information model" means. My suggestion... OLD: It is understood that SNMP SET is not used for MPLS configuration these days, however the read-write and read-create option is still specified for some objects as a way to provide the information model. NEW: At the time of writing, SNMP SET is no longer recommended as a way to configure MPLS networks as was described in [RFC3812]. However, since the MIBs specified in this document extend and are intended to work in parallel with the MIB for MPLS specified in [RFC3812], certain objects defined here are specified with MAX-ACCESS of read-write or read-create so that specifications of the base tables in [RFC3812] and the extensions in this document are consistent. Although the examples described in Section 9 specify means to configure MPLS-TP tunnels in a similar way to the examples in [RFC3812], this should be seen as indicating how the MIB values would be returned in the specified circumstances having been configured by alternative means. Further responses are embedded below. I see this draft has appeared on next week's IESG agenda. If you can get me an updated snapshot asap it would be helpful so I can do the telechat review as I am travelling next week. Cheers, Elwyn On 11/12/14 20:41, Sam K. Aldrin wrote:Hi Elwyn, Thanks for the review and comments. Please find the responses inline.On Dec 11, 2014, at 10:36 AM, Elwyn Davies <[email protected]> wrote: I am the assigned Gen-ART reviewer for this draft. For background on Gen-ART, please see the FAQ at <http://wiki.tools.ietf.org/area/gen/trac/wiki/GenArtfaq>. Please resolve these comments along with any other Last Call comments you may receive. Document: draft-ietf-mpls-tp-te-mib-09.txt Reviewer: Elwyn Davies Review Date: 10 December 2014 IETF LC End Date: 8 December 2014 IESG Telechat date: (if known) - Summary: Not ready. I am not a MIB expert nor an MPLS(-TP) configuration expert, so I have assumed that the details of the MIB specification have been addressed by Joan's MIB Doctor review and the configuration examples have been checked by an MPLS-TP expert. However, the introductory text needs significant work to make it easier for people who are not MPLS-TP experts to come to grips with the document.This MIB is intended to be used for MPLS-TP tunnels and is done by the way of extending existing MPLS-TE MIB. The assumption is that reader is already aware of MPLS-TP. Hence we didn’t provide a primer for MPLS-TP in this MIB and I am not sure if it is the right place either.Sure.. Reading some of the earlier reviews there were some terms which were not very well defined. The text below for para 2 of s1 gives enough background to help I think.The major issue with this document is that it appears to go against the current IETF view that SNMP is not a satisfactory solution for configuring networks. The document has effectively reiterated the RFC 3812 situation from 10 years ago when the IETF held its nose and said that SNMP was the only game in town even if security sucked. As I mention below, this was extensively discussed a year ago but I couldn't determine whether this draft was given a special dispensation even though consensus seemed to be that writeable MIBs were considered inappropriate. If this is the case, it will be sufficient to adapt the end of s1.We have deliberated over this topic for more than two years and after multiple discussions along with Routing AD and OPS AD, we decided to go forward with the writable objects for this MIB. Additionally we added a small paragraph at the end of s1, as recommended, the reason for doing so.OK.. see notes at start.AFAICS this draft has not had the 'grammar review' recommended by its AD about a year ago and there are a number of areas in the object descriptions where language improvements would be desirable in addition to notes given here. That is it still needs the grammar review.We could take help of English reviewers and request WG chairs to help us out in this regard.Thanks Tom.. sorry I am a bit pushed for time as NFSv4 took up lots of tiem last week :-(There are some more minor issues, particularly as regards the description of the types of tunnel in s1, the discussion of the contents of the MIBs in s6 and possibly in regard to the interaction with the standard interface table. Major issues: Support for configuration: The issue of SNMPset (write) support was discussed at length in the context of the MIB doctors' review of v-05 of this draft. The consensus at that time appeared to be that provision of write support in new MIBs should be strongly discouraged. I am unclear what the outcome of that discussion in the context of this draft was, but it is clear that the draft is very much written from the point of using the MIB as a configuration tool, especially in s9 (examples of usage). Whilst this technique reflects the equivalent section is RFC 3813, that document was written over 10 years ago and considerable effort has been devoted to providing alternative and more secure ways of configuring networks in the intervening time. The body of the document has not been altered to reflect the discussion that occurred.Whether SNMP write should exist or not discussion is not within the scope of this document. Whether this MIB should support writable MIB objects was discussed and the conclusion was yes. The text at end of s1 was added as recommended by AD’s. On the contrary, if this MIB were to change the way RFC3813 is to implemented/interpreted along with the MIB i.e. from writable for TE but read-only for non MPLS-TE tunnels, then it should be documented."Lip service" is paid to the discouragement of the use of SNMPset by the addition of para 3 of s1:It is understood that SNMP SET is not used for MPLS configuration these days, however the read-write and read-create option is still specified for some objects as a way to provide the information model.It is not clear to me why providing read-write or read-create options enhance the MIB or are "a way to provide the information model". I note that despite the extensive discussion of this topic by WG members and MIB specialists back in December 2013, this issue was not flagged up in the Shepherd's write up. If it has now been agreed that the configuration "flavour" is to be accepted as WG consensus in spite of being contrary to current practice, it appears to me that the word "configuration" should be removed from the last sentence of para 2 of s1 and the last para of s1 rewritten to explain why write capabilities are used in a more convincing manner.As noted above, the write option was retained after discussing at length, both at the WG sessions and over emails. The statement in last part of s1 was added as per the advice we received to move forward with the writable objects [ref: email from OPS AD dated Mar 11 on MPLS mailing list]. The main reason for writable objects, is because the MPLS-TE had writable objects and MPLS-TP extensions leverage this existing MIB and also few vendors have implemented them. Having said that, we are open to any suggested text, in addition to the one, which you already did below, in regards to ‘writable’ objects.See above.Minor issues: Abstract/s1: Needs to be clear in both places that is is intended for MPLS-TP, this: -- Abstract and s1: s/transport networks./MPLS networks conforming to the MPLS Transport Profile (MPLS-TP)./ s1: What is a Non-MPLS-TP (transport) network?MPLS-TE and other MPLS networks which is not constrained by transport requirements. Assuming some new tunnel type comes up into the future like bi-directional TE. :DIn that case I would just call it a "basic MPLS" network or some such. non-MPLS-TP is rather ambiguous.s1: The explanation of what the MIB extensions in this document actually do is not clear to the general reader. I suggest replacing para 2 completely: OLD: The existing MPLS Traffic Engineering (TE) Management Information Base (MIB) [RFC3812] and Generalized Multiprotocol Label Switching (GMPLS) Traffic Engineering Management Information Base [RFC4802] do not support the management of transport network requirements of Tunnel end points with non-IP based identifiers and static bidirectional tunnels. This document focuses on static bidirectional MIB modules that should be used in conjunction with [RFC3812] and companion document [RFC3813] for MPLS Transport Profile (MPLS-TP) path configuration and management. NEW: As described in the MPLS Traffic Engineering (TE) Management Information Base (MIB) definition [RFC3812], MPLS traffic engineering is concerned with the creation and management of MPLS tunnels. This term is a shorthand for a combination of one or one or explicitly routed LSPs (ERLSPs) linking an ingress and an egress LSR. Several types of point-to-point MPLS tunnels may be constructed between a pair of LSRs A and B: - Unidirectional with a single LSP (say) from A to B. - Associated bidirectional consisting of two separately routed ERLSPs, one linking A to B and the other linking B to A. Together the pair provide a single logical bidirectional transport path. - Corouted bidirectional consisting of an associated bidirectional tunnel but with the second ERLSP from B to A following the reverse of the path of the ERLSP from A to B, in terms of both nodes and links. Tunnels may be either statically configured by management action or dynamically created using a LSP management protocol.what is ‘LSP management protocol’?I meant either RSVP or LDP or anything else that might be used dynamically. Not sure what the generic term is these days.The existing MPLS TE MIB [RFC3812] and the Generalized Multiprotocol Label Switching (GMPLS) Traffic Engineering Management Information Base [RFC4802] address only a subset of the combinations of statically and dynamically configured tunnel types, catering for statically configured unidirectional tunnels together with dynamically configured unidirectional and corouted bidirectional tunnels. They are alsorestricted to to end point LSRs identified by IP addresses. The MPLS-TP TE MIB defined in this document extends the MIB defined in [RFC3812] to cover all six combinations (that is adding support for statically configured associated and corouted bidirectional plus dynamically configured associated bidirectional tunnels). It also extends support to end points that are identified other than with IP addresses. This support is provided by a suite of four MIB modules that are to be used in conjunction with the MIBS defined in [RFC3812] and the companion document [RFC3813] for MPLS Transport Profile (MPLS-TP) TE path [configuration and]* management. END NEWThank you. Will go through the text again and replace as suggested.OK.* Note: Using the term 'configuration' is inconsistent with the discussion in para 3. See Major Issues above s5, bullet 1: s8 in RFC 3812 discusses the use of the Interface Table with MPLS. It should be made clear here: 1. Whether, if the MPLS-TP Tunnel is treated as an interface, there is any difference in the usage of the ifTable fields as compared with standard MPLS. In particular if a different interface type should be applicable. 2. Are there any issues if all or (more especially) a subset of the tunnels are not treated as interfacesHaven’t come across any different types as such. Do you see any specific type which is of contrary to RFC 3812, that MPLS-TP defines? Will ask my co-authors as well.I don't see anything obvious except that there might be some reason to declare a different interface type rather than using type 150 defined in RFC 3812 especially for non-IP interfaces. I am not sure how the ifSpeed field is used on bidirectional tunnels (that is also a point for RFC 3812). Also whether the operational status could take on other values if one direction of the tunnel is not working but the other is. Otherwise it would be worth a statement that the interface table can be used as in RFC 3812 (or not) as appropriate.Row pointer usage: s9 of RFC 3812 considers Row Pointer usage - are there any differences or additional considerations for these MIBs?None that we are aware off.There are three RowPointer type objects: mplsTunnelExtOppositeDirPtr and two in MplsXCExtEntry. Notes about consistent use with the corresponding entries in the base tables would be desirable perhaps.s6: Sections 6.1 to 6.4 are not MIBs (as indicated by the title and prologue) but MIB objects in the MPLS-TE-EXT-STD-MIB MIB. Please reorganize s6 accordingly. Looking back at RFC3812, the structure of the document in sections 5 and 6 appears to be more helpful to the new reader with a summary of the four MIB modules in one section (expanded from ss6.5 - 6.7) followed by notes on the key MIB objects in each MIB as necessary. It would also be helpful to clarify where objects in this MIB are expected to parallel those in the basic (RFC 3812) and note that they are indexed equivalently (notably in the case of mplsTunnelTable and mplsTunnelExtTable). Nits/editorial comments:Nod.General: Consistent use of bi-directional or bidirectional: Please choose one and use it throughout.Nod.General: The qualifier "sparse" is used incorrectly in several places (e.g., sparsely extended). Presumably the intention is that the extensions are "slight" or "limited" . In most cases the term can be deleted: The degree of extension will ultimately be in the eyes of the implementer! (s5 - 2 cases, s6.4, s7 - 2 cases, s8, s9.1.6, s9.2.9, s9.3.6, s12 - 3 cases) General: The figures need number and captions. The numbers should be used to refer to the figures.Will review and edit as suggested.s4, para 1: s/unidirectional tunnel/unidirectional tunnels/Nod.s4, para 1, last sentence: s/re-use/re-use and extend/Nod.s4, para 2: OLD: retained in the same document, instead of a separate document. NEW: all defined in this document, rather than split over several documents. s5, para 1: s/This document identifies/The MIBs in this document satisfy/ s5, para 2: s/The MIB module supports/The MIB modules, taken together, support/ s5, para 2: s/static and signaled/statically configured and dynamically signaled/ s5, bullet 4: s/sparsely extended/extended/ s9.1.6, s9.2.9, s9.3.6: s/a sparse augmentation/a limited augmentation/Nod for all the above.s5, bullet 5: It would be helpful to explain how node identification differs from standard MPLS to understand why this mapping is needed. There appears to be text in s6.1 that might help but it is too late to make it easy to understand this section.Will add reference to s6.1.ss10-13: It is conventional to give the RFCs used as references in the docuement s/RFC 3812/[RFC3812]/ etc.Nod.s14: This is a near duplicate of the security considerations in RFC 3812. It might be easier to reference that section and add a note that extra tables may provide further sensitive information.Nod.A brief discussion of whether the non-IP case makes any difference would be useful.I do not think there is a difference as such. We have provided example for non-ip case anyway.For security???s16: At the very least RFC 3811, RFC 3812 and RFC 3813 are normative. RFC 6923 probably is. RFC 6370 and RFC 4802 may also be.Nod. thanks again -sam _______________________________________________ Gen-art mailing list [email protected] https://www.ietf.org/mailman/listinfo/gen-art
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