Re: [RTG-DIR] [Detnet] Rtgdir last call review of draft-ietf-detnet-mpls-04

[Lou Berger <[e-mail]>]

Hi,

Balázs thank you for the clarification -- see below for one comment.

On 1/10/2020 8:56 AM, Balázs Varga A wrote:
> Yes, but why not the Preferred CW?
>
> <Balazs>/<Stewart> Sum of mailing + proposed fixing:
> The PCW only supports a 16bit sequence number and it has the skip zero auto-signaling of active S/N feature.
> This was a problem for DetNet because:
> - We were worried about S/N rollover frequency in some applications and so we wanted the option of a larger S/N.
> - We wanted to have the option to propagate the S/N from the payload to the transport to simplify the implementation
> in some cases. These applications have a non-skip zero S/N. Skip zero is an irritation to implement and we should probably
> have signaled in in PWs.
> As you note in is only a preferred design for PWs, DetNet is not constrained by that and there were good reasons to adopt
> this alternate approach.
> We assume to fix this with adding above information to the text.
> NEW text to be added in section 4.2.1:
>      "This format of the d-CW was created in order (1) to allow larger S/N space to
>      avoid S/N rollover frequency in some applications and (2) to allow non-skip
>      zero S/N what simplifies implementation."

While I completely agree with the rational and validity of the good 
question, I don't think such motivation belongs in the document.  We 
generally don't document every design decision in a specification.  I 
don't feel strongly about this so if others do, I'll defer to their 
opinion...

Balázs, Carlos, Do you think it should stay?

Thanks,

Lou (as contributor)