Re: [Pce] Query regarding draft-ietf-pce-binding-label-sid-02

[Mrinmoy Das <[e-mail]>]

Hi All,

If we only mention 20-bit label then what will be the structure of it?
As per generic MPLS label structure 24-bit used to look like as follows:

|<--------20-bit---------->|<-3-bit->|<-1-bit->|
|<-MPLS 20-bit label->|<- TC ->|<-  S  ->|

Now if we just mention about MPLS 20-bit label, is that mean following
representation:

|<-4-bit->|<--------20-bit---------->|
|<-all 0->|<-MPLS 20-bit label->|

Thanks & Regards,
Mrinmoy

On Wed, Mar 25, 2020 at 3:56 PM stefano previdi <[e-mail]> wrote:

> Hi Dhruv,
>
> I agree with your proposed changes:
>
> 1. only mention the 20 bits label value
> 2. fix the length to 4.
>
>
> Thanks.
> s.
>
>
> > On Mar 24, 2020, at 3:14 PM, Dhruv Dhody <[e-mail]> wrote:
> >
> > Hi Mrinmoy,
> >
> > I will give authors some time to respond and confirm (and spin a new
> > update). I have noted this in the PCE WG wiki [
> > https://trac.ietf.org/trac/pce/wiki/WikiStart ] to make sure we could
> > track this to closure.
> >
> > Thanks!
> > Dhruv
> >
> > On Tue, Mar 24, 2020 at 7:11 PM Mrinmoy Das <[e-mail]>
> wrote:
> >>
> >> Hi Dhruv,
> >>
> >> Thanks for your quick reply.
> >>
> >> I have added PCE WG in this mail. More inline.
> >>
> >> Thanks & Regards,
> >> Mrinmoy
> >>
> >> On Tue, Mar 24, 2020 at 6:00 PM Dhruv Dhody <[e-mail]>
> wrote:
> >>>
> >>> Hi Mrinmoy,
> >>>
> >>> I was suggest you to also include [e-mail]; WG could benefit from
> >>> the discussion in future. More inline.
> >>>
> >>> On Tue, Mar 24, 2020 at 5:08 PM Mrinmoy Das <[e-mail]>
> wrote:
> >>>>
> >>>> Respected Authors and Contributors,
> >>>>
> >>>> Hope you all are doing well and safe in this tough times of Corona
> Virus Outbreak.
> >>>>
> >>>> I like to draw your attention regarding some parts of
> draft-ietf-pce-binding-label-sid-02 which I didn't able to understand
> properly.
> >>>>
> >>>> 1. BT = 0: The binding value is an MPLS label carried in the format
> >>>>
> >>>>  specified in [RFC5462] where only the label value is valid, and
> >>>>  other fields (TC, S, and TTL) fields MUST be considered invalid.
> >>>>  The Length MUST be set to 7.
> >>>>
> >>>>
> >>>>    Previous versions of private draft uses 4 byte to store MPLS 20
> Bit label and ignores TC, S & TTL fields.
> >>>
> >>> The length in the previous version was 6, which was incorrect. The TLV
> >>> length is as per https://tools.ietf.org/html/rfc5440#section-7.1
> >>> Which didnt make sense and your calculation below is correct!
> >>>
> >>>>    But in IETF draft after TLV structure redefinition, total length
> of the TLV becomes 7, i.e. BT(1 Byte)+Reserved(3 Byte)+MPLS 20bit Label(3
> Byte) = 7 Byte
> >>>
> >>> Yes
> >>>
> >>>>    So, now MPLS 20 Bit Labelwill be stored in 3 byte. Is it correct?
> >>>
> >>> You can consider it a case of rounding up 20 bits to 3 bytes.
> >>>
> >>>
> >>>>    If this is correct then I feel the wording of the above paragraph
> needs to be more specific, meaning in 3 Byte Label there will be no space
> for TTL, so
> >>>>    my suggestion is to make below correction:
> >>>>
> >>>>    BT = 0: The binding value is an MPLS label carried in the format
> >>>>
> >>>>  specified in [RFC5462] where only the label value is valid, and
> >>>>  other fields (TC, S, and TTL) fields MUST be considered invalid.
> >>>>  The Length MUST be set to 7.
> >>>>
> >>>
> >>> My suggestion would be not mention any of the other fields and talk
> >>> only of 20 bits of Label. I see other SR RFCs take similar approach.
> >>
> >>
> >> Sounds Good. I'm agree with you.
> >>
> >>>
> >>>>
> >>>> 2. In some cases, a stateful PCE can request the PCC to allocate a
> >>>>
> >>>>  binding value.  It may do so by sending a PCUpd message containing an
> >>>>  empty TE-PATH-BINDING TLV, i.e., no binding value is specified
> >>>>  (making the length field of the TLV as 2).  A PCE can also make the
> >>>>  request PCC to allocate a binding at the time of initiation by
> >>>>  sending a PCInitiate message with an empty TE-PATH-BINDING TLV.
> >>>>
> >>>>
> >>>>  As per new Binding TLV Structure below, BT is of 1 Byte and there
> will be 3 Byte Reserved.
> >>>>
> >>>>         0                   1                   2                   3
> >>>>
> >>>>       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
> >>>>      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> >>>>      |             Type              |             Length            |
> >>>>      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> >>>>      |      BT       |                 Reserved                      |
> >>>>      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> >>>>      ~            Binding Value (variable length)                    ~
> >>>>      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> >>>>
> >>>>
> >>>>   Now, an empty Binding TLV should have length of BT(1 Byte) +
> Reserved (3 Byte) = 4 Byte instead of 2 Byte.
> >>>>
> >>>>   So, I do not understand how in the draft it is calculated as 2
> Byte. Could you please give me some clue?
> >>>
> >>>
> >>> This seems to be an error IMHO. 4 seems to be correct.
> >>
> >>
> >> Okay. So what would  be your suggestion to developer who is
> implementing this draft? Should it be taken as 4? If draft needs correction
> >> when will that be published?
> >>>
> >>>
> >>> Thanks!
> >>> Dhruv
> >>>
> >>>>
> >>>> Thanks & Regards,
> >>>> Mrinmoy
>
>