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

["Carlos Pignataro (cpignata)" <[e-mail]>]

Hi, Lou,

> 2020/01/27 午前9:41、Lou Berger <[e-mail]>のメール:
> 
> 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?
> 

I have no strong feelings either way, but I believe if this is a departure from a “preferred” format from a BCP, then a one-liner explanation would not hurt. I’d leave this one in.

Thanks,

Carlos.

> Thanks,
> 
> Lou (as contributor)
>