Re: [mpls] More comments from another Reviewer//Re: MPLS-RT review of draft-bryant-mpls-sfl-control

Loa Andersson <loa@pi.nu> Fri, 03 January 2020 04:12 UTC

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To: Zhenghaomian <zhenghaomian@huawei.com>, Stewart Bryant <stewart.bryant@gmail.com>, "Andrew G. Malis" <agmalis@gmail.com>
Cc: "draft-bryant-mpls-sfl-control@ietf.org" <draft-bryant-mpls-sfl-control@ietf.org>, mpls-chairs <mpls-chairs@ietf.org>, mpls <mpls@ietf.org>
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From: Loa Andersson <loa@pi.nu>
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Subject: Re: [mpls] More comments from another Reviewer//Re: MPLS-RT review of draft-bryant-mpls-sfl-control
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Haomian,

Thanks! The author will evaluate and address comment. I have small
comment on your comments inline.

On 03/01/2020 10:44, Zhenghaomian wrote:
> Hi, All,
> 
> Happy new year to you all.
> 
> I am another MPLS-RT reviewer for this document, and would like to 
> follow up in this thread, by starting from reviewing the latest 
> draft-bryant-mpls-sfl-control-05. Generally I think this is a complete 
> work with self-contained solution, and I assume the importance of the 
> document has been evaluated by the WG chairs and experts. Some comments 
> are listed below as a ‘MPLS beginner’J
> 
> 1.Section 1 Introduction
> 
> "well managed" should be "well-managed"; -> this also applies for 
> section 7 security considerations.
> 
>   "withdrawn" should be "withdraw", -> this also applies for the 
> abstract text.
> 
> 2. The RFC6374 looks slightly different than other RFC citations, as the 
> '[]' is missing; please check the formatting.
> 
> 3. section 3.1 SFL Control Message
> 
> I am curious on the bits allocation "26-bit Session Identifier" and 
> "6-bit SFL Batch", which is not typical (my intuitive is 24+8), and 
> there is no reason in the explanation text below the TLV. We need to 
> confirm 1) the allocation is intended to be 26+6; 2) add something to 
> the TLV explanation, for example:
> 
> OLD:
> 
> SFL Batch      Used where the SFLs for this Session Identifier
> 
>                 managed across multiple SFL Control Messages.  A given
> 
>                 set of SFLs MUST be retained in the same batch.
> 
> NEW:
> 
> SFL Batch (6 bits) Used where the SFLs for this Session Identifier
> 
>                    managed across multiple SFL Control Messages.  A given
> 
>                    set of SFLs MUST be retained in the same batch.
> 
> 4. section 3.1 SFL Control Message
> 
> Regarding the flags, my understanding is that the intention is to use 
> the first bit to indicate query/respond, and pad the other 3 bits as 0. 
> The processing of '0' bits is understood as "MUST be set to 0 by sender 
> and ignored by receiver". Is it correct? If yes, the following statement 
> may be easier:
> 
> OLD:
> 
> Flags: The format of the Flags field is shown below.
> 
>                                +-+-+-+-+
> 
>                                |R|0|0|0|
> 
>                                +-+-+-+-+
> 
>                          SFL Control Message Flag
> 
>     R: Query/Response indicator.  Set to 0 for a Query and 1 for a
> 
>        Response.
> 
>     0: Set to zero by the Sender and ignored by the Receiver.
> 
> NEW:
> 
> Flags (4 bits): The first bit is set to 0 for a query and 1 for a
> 
> response; the next 3 bits MUST be set to 0 by the Sender and ignored
> 
> by the Receiver.

The use of "first bit" and "next bits" could be confusing since it may
vary by context, e.g. order on the wire and descriptive text. I think
it would be better to use LSB and MSB.

BTW - I quite like the figure, if for no other reason that it give a
name for the R-bit.

To the authors: Query/Response indicator is fine in this context, but is
it possible that it might be confused with other Query/Response
indicators? Do we want to talk about "SFL Query/Response indicator" as
the general term?

/Loa
> 
> 5. section 3.1 SFL Control Message
> 
> Regarding the 'Control Code', do we allocate specific value for the 
> query/response actions? For example, we can have request (control code = 
> 0), refresh (control code = 1) and withdraw (control code =2) for a 
> query. Currently there is no such allocations.
> 
> 6. section 3.2.1.  Request/Grant
> 
> In the first paragraph, when you say 'It sets ...' and 'It chooses ...', 
> does the “it” refer the Querier?
> 
> This problem confused me some times in later sections as well.
> 
> 7. section 4. Return Path
> 
> 'mulit-point' -> 'multi-point'
> 
> The usage of comma and bracket confused me, does it mean the following?
> 
> Where the MPLS LSP (or other construct) is a multi-point to point or
> 
> multi-point to multi-point, the RFC6374 Address TLV MUST be included
> 
> in Query packet even if the response is requested in-band, since it is
> 
> necessary to provide the necessary return address for this request.
> 
> Thank you.
> 
> Best wishes,
> 
> Haomian
> 
> *发件人:*mpls [mailto:mpls-bounces@ietf.org] *代表 *Stewart Bryant
> *发送时间:*2020年1月3日0:28
> *收件人:*Andrew G. Malis <agmalis@gmail.com>
> *抄送:*draft-bryant-mpls-sfl-control@ietf.org; mpls-chairs 
> <mpls-chairs@ietf.org>rg>; mpls <mpls@ietf.org>
> *主题:*Re: [mpls] MPLS-RT review of draft-bryant-mpls-sfl-control
> 
> Fixed in the master I will use for the next release.
> 
> - Stewart
> 
> 
> 
>     On 2 Jan 2020, at 14:47, Andrew G. Malis <agmalis@gmail.com
>     <mailto:agmalis@gmail.com>> wrote:
> 
>     Stewart,
> 
>     Looking at the diff from the previous version, I just noticed a typo
>     that I missed earlier. In the first paragraph of the introduction,
>     "withdrawn" should be "withdraw". I also see that you added an
>     Oxford comma, which is fine by me! :-)
> 
>     Cheers,
> 
>     Andy
> 
>     On Thu, Jan 2, 2020 at 9:40 AM Andrew G. Malis <agmalis@gmail.com
>     <mailto:agmalis@gmail.com>> wrote:
> 
>         Stewart,
> 
>         Glad to be of assistance.
> 
>         Cheers,
> 
>         Andy
> 
>         On Thu, Jan 2, 2020 at 9:09 AM Stewart Bryant
>         <stewart.bryant@gmail.com <mailto:stewart.bryant@gmail.com>> wrote:
> 
> 
>             Hi Andy
> 
>             Thank you for the review.
> 
>             > On 30 Dec 2019, at 19:31, Andrew G. Malis <agmalis@gmail.com <mailto:agmalis@gmail.com>> wrote:
>             > 
>             > All,
>             > 
>             > I’ve been selected as an MPLS-RT reviewer for draft-bryant-mpls-sfl-control,
>             > which is currently a candidate for MPLS WG adoption.
>             > 
>             > In general I believe that the draft is ready for WG adoption. However, I have a few minor comments which may be addressed either before or after WG adoption.
>             > 
>             > 1. The Security Considerations section says "It is assumed that this protocol is run in a well managed MPLS network with strict access controls preventing unwanted parties from generating MPLS OAM packets." While this is true of most (all?) MPLS networks,  this assumption should also be stated in the abstract or
>             Introduction as well.
> 
>             I have added a line to the Introduction.
> 
>             I generally work on the assumption that the purpose of the
>             Abstract is to help the potential reader decide if they want
>             to read the document (or more likely to help a search engine
>             match the document against a query) and I am unconvinced as
>             to value of the qualification text in deciding whether to
>             read the rest of the document.
> 
> 
>             > 
>             > 2. Section 8 contains the line "Force references to appear with mkd [RFC3032] [RFC5036]". However, both references appear elsewhere as well, so this line can be removed.
> 
>             The earlier references are in text that I included as a
>             figure to force the layout style I wanted, and the markdown
>             compiler ignores references in figures. The compiling
>             process excluded unused references so they have to be
>             forced. I have changed the text to
> 
>             RFC Editor please remove this note which is used to force
>             the following references to appear {{RFC3032}} {{RFC5036}}
> 
>             > 
>             > 3. I would move "I-D.ietf-mpls-sfl-framework" to the Normative References, as understanding it is necessary to understand this draft.
>             > 
> 
>             The framework is informational and so the reference would
>             become a down-ref. I will leave it to the chairs and ADs on
>             how they want to proceed with this. It is not unusual for a
>             framework to be required reading and yet informational.
> 
> 
>             > 4. The text in Section 2 is out of date. The current wording is:
>             > 
>             > The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they  appear in all capitals, as shown here.
>             > 
>             > RFC 8174 should also be added as a normative reference.
> 
>             Done
> 
>             > 
>             > 5. When this draft was last updated, Stewart included the following in an email message to the MPLS WG:
>             > 
>             > "Next to do is authors of draft-bryant-mpls-sfl-control to check that 
>             > this is suitable to be called by another protocol to act on its behalf.
>             > When we are satisfied that that is that case and any consequentially 
>             > necessary amendments have been make to the other drafts we will
>             > request adoption of draft-bryant-mpls-sfl-control and then WGLC on all 
>             > three."
>             > 
>             > There's been no follow-up indication that this analysis has occurred, or further revision to the draft. If it has, the authors should indicate as such on the list. If it hasn't, then this will serve as a reminder to the authors.
> 
> 
>             George and I discussed this and concluded that the design
>             was satisfactory.
> 
>             I certainly indicated this to the chairs but I cannot
>             remember if I posted that to the list. If any reader of this
>             note (which will go to the MPLS list) has any technical
>             concerns WRT this point, please raise them and we will work
>             with you to address the issue.
> 
>             New version (05) has been uploaded.
> 
>             Best regards
> 
>             Stewart
> 
> 
> 
>             > 
>             > Thanks,
>             > Andy
>             > 
> 
> 
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-- 


Loa Andersson                        email: loa@pi.nu
Senior MPLS Expert
Bronze Dragon Consulting             phone: +46 739 81 21 64