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

[Mrinmoy Das <[e-mail]>]

Hello Dhruv,

I appreciate your help. :)

Thanks & Regards,
Mrinmoy

On Tue, Mar 24, 2020, 7:45 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
>