Subject: [mpls] Martin Vigoureux's Yes on draft-ietf-mpls-sfc-05: (with COMMENT)

From: Datatracker on behalf of Martin Vigoureux <[email-masked]>
Date: Wed, 06 Mar 2019 02:19:35 -0800

Martin Vigoureux has entered the following ballot position for
draft-ietf-mpls-sfc-05: Yes

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COMMENT:
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Hello

thank you for this document.

I know I'm being too pernickety:
You say:
   o  An SFF MUST decrement the TTL by one each time it performs a
      forwarding lookup.
but in the examples you also say:
   b.  When the packet arrives at SFFa it strips any labels associated
       with the tunnel that runs from the classifier to SFFa.  SFFa
       examines the top labels and matches the SPI/SI to identify that
       the packet should be forwarded to SFa.  The packet is forwarded
       to SFa unmodified.
and
   d.  SFFa modifies the SI in the lower label stack entry (to 254) and
       uses the SPI/SI to look up the forwarding instructions.

It could look as two forwarding lookup, which, according to the requirement,
could lead to two TTL decrements. I do read in step b that the packet is
forwarded unmodified, and read in Section 6 "The TTL in SF label stack entry is
decremented once for each forwarding hop in the SFP" but still I wonder if some
clarification wouldn't be beneficial.

nits:
   TTL:  The TTL fields in the SFC Context label stack entry SF label
      stack entry SHOULD be set to 1 as stated in Section 5,
Do you mean: SFC Context label stack entry *and* SF label stack entry ?

s/document)./document./

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From: "Adrian Farrel" <[email-masked]>
Date: Thu, 7 Mar 2019 15:18:28 -0000

Hi Martin,

Thanks for your thoughts.

> I know I'm being too pernickety:

As is your right 😉

> It could look as two forwarding lookup, which, according to the
> requirement, could lead to two TTL decrements.  I do read in step b that the packet is

Oh, dear. Yes, you're right about the word "forward". It crops up too often with too many meanings.

I think the tidies solution is to change the first quote to say...

   An SFF MUST decrement the TTL by one each time it performs a
   lookup to forward a packet to the next SFF.

> Do you mean: SFC Context label stack entry *and* SF label stack entry ?

Yup

> s/document)./document./

Ack

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From: "Vigoureux, Martin (Nokia - FR/Paris-Saclay)" <[email-masked]>
Date: Fri, 8 Mar 2019 12:38:17 +0000

Thanks Adrian, that's perfect.