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Re: [mpls] Segment Routing vs. “Label Stacking” in draft-ietf-mpls-sfc-00

Loa Andersson <loa@pi.nu> Tue, 15 May 2018 08:38 UTC

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To: "Andrew G. Malis" <agmalis@gmail.com>, mpls@ietf.org, sfc@ietf.org
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From: Loa Andersson <loa@pi.nu>
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Subject: Re: [mpls] Segment Routing vs. “Label Stacking” in draft-ietf-mpls-sfc-00
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 >chair-hat off>

Andy,

Inlime please.

On 2018-05-07 13:15, Andrew G. Malis wrote:
> I just realized that I was a bit more terse in my email than I should 
> have been. When I said that the MPLS WG had never discussed “Label 
> Stacking”, well of course we have the label stack, but we had never 
> discussed, prior to Segment Routing, using the label stack as a method 
> to do source routing via only popping labels, with no label swapping 
> along the path.

I think that this would be an argument if

    POP'n'go == SR

but an entirely different case if

    POP'n'go > SR

I think we can see from the uses case proposed by the authors of
draft-ietf-mpls-sfc there are a lot of additional things for POP'n'go,
and that it motivates its place in an MPLS wg draft.

Please send comments on Adrian mail with proposed changes.

/Loa


> 
> Cheers,
> Andy
> 
> 
> On Mon, May 7, 2018 at 8:05 AM, Andrew G. Malis <agmalis@gmail.com 
> <mailto:agmalis@gmail.com>> wrote:
> 
>     The following URL is a diff between draft-farrel-mpls-sfc-04
>     and draft-farrel-mpls-sfc-05, when section 6 was updated to change
>     Segment Routing to “Label Stacking”. (Note that the only changes
>     from draft-farrel-mpls-sfc-05 to draft-ietf-mpls-sfc-00 were the
>     name and date change).
> 
>     https://tools.ietf.org/rfcdiff?url2=draft-farrel-mpls-sfc-05.txt
>     <https://tools.ietf.org/rfcdiff?url2=draft-farrel-mpls-sfc-05.txt>
> 
>     If you examine the changes to section 6, it’s pretty clear (at least
>     to me) that the changes are really just cosmetic in nature, such as
>     removing a reference to draft-ietf-spring-segment-routing and
>     changing a few terms here and there.
> 
>     That, combined with the fact that the MPLS WG had never discussed
>     “Label Stacking” in a draft (never mind an RFC) prior to the
>     introduction of Segment Routing leaves me to conclude that section 6
>     really does need to be removed in order to comply with the WG
>     concerns about -04 and earlier revisions of draft-farrel.
> 
>     Thanks,
>     Andy
> 
> 
> 
> 
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-- 


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

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