Re: [Pce] cursory review of draft-xiong-pce-lsp-flag

Loa Andersson <loa@pi.nu> Wed, 29 July 2020 10:43 UTC

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To: Dhruv Dhody <dd@dhruvdhody.com>
Cc: draft-xiong-pce-lsp-flag@ietf.org, "pce-chairs@ietf.org" <pce-chairs@ietf.org>, "pce@ietf.org" <pce@ietf.org>
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From: Loa Andersson <loa@pi.nu>
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Date: Wed, 29 Jul 2020 18:43:25 +0800
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Subject: Re: [Pce] cursory review of draft-xiong-pce-lsp-flag
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Dhruv,

Inline please.

On 29/07/2020 17:01, Dhruv Dhody wrote:
> Hi Loa,
> 
>> Comment:
>>
>> 5.2.  PCEP-Error Object
>>
>>      IANA is requested to register the following error types and error
>>      values within the "PCEP-ERROR Object Error Types and Values"
>>      subregistry of the "Path Computation Element Protocol (PCEP) Numbers"
>>      registry:
>>
>>             +--------------+-------------------------------------+
>>             |  Error-Type  |  Meaning                            |
>>             +--------------+-------------------------------------+
>>             |  6           |  Mandatory Object missing           |
>>             |              |  Error-value                        |
>>             |              | TBD2: LSP-EXTENDED-FLAG TLV missing |
>>             +--------------+-------------------------------------+
>>
>>                                     Table 2
>>
>> Both the RTG DIR rules and IANA rules strongly advice against putting
>> fixed numeric  values into allocation from existing registries. The
>> reason is obvious, in the time from you put the value in your document
>> until iet is ready for IESG review (which includes IANA review) someone
>> else might have been assigned tht value. This has happened and have
>> caused serious problems.
>>
>> 6 in table 2 hould be replaced with TBA (to be assigned).
>>
>> Note: If you really want the value 6, we should go for an early
>> allocation as soon as we have the wg document.
>>
> 
> [Dhruv] The value 6 is for Error-Type already allocated by RFC 5440.
> This I-D is asking for a new Error-Value which is  TBD2. A reference
> column in the IANA table would have helped here.

hmmmm - okey, but no, we are asking IANA to register a new error-value,
but not a new error type. The text says:

   "IANA is requested to register the following error types and error
     values ..."

But then the table is very unclear, at a minimum it should look
something like this:

   +-------------+----------------------------+-------------------------+
   |  Error-Type | Meaning                    | Error-value             |
   +-------------+----------------------------+-------------------------+
   |  6          | Mandatory Object missing   | 0: Unassigned           |
   |             |                            | 1-15 Assigned           |
   |             |                            | TBD2: LSP-EXTENDED-FLAG |
   |             |                            |       TLV missing       |
   +-------------+----------------------------+-------------------------+

                                      Table 2


> 
>> Question:
>>
>> In section 4 you say:
>>
>>      The LSP-EXTENDED-FLAG TLV MUST be defined as mandatory when a router
>>      supporting the LSP Object and needs to use the extended flag field.
>>
>> I don't really parse; are you saying that if it is present it should be
>> treated as mandatory?
>>
>> If that is what you are saying, what does it change?
>>
> 
> [Dhruv]: I read it as a requirement for a future extension that would
> define a flag in the LSP-EXTENDED-FLAG TLV.
> 
> If that is true, I would suggest not using normative MUST. How about -
> 
> A future extension that defines a flag in the LSP-EXTENDED-FLAG TLV
> could mark this TLV as mandatory to be carried the LSP Object.

I have been reading a bit more, but this is still unclear to me, if I
understand it will still be valid to send without the extended TLV
(if you don't need the flags). How are you deciding if the extended TLV
missing?


/Loa
> 
> Thanks!
> Dhruv
> 
>> /Loa
>>
>>
>> --
>>
>> Loa Andersson                        email: loa@pi.nu
>> Senior MPLS Expert                          loa.pi.nu@gmail.com
>> Bronze Dragon Consulting             phone: +46 739 81 21 64

-- 

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