Re: Comments on raft-fz-6man-ipv6-alt-mark-01

Ole Troan <otroan@employees.org> Fri, 01 November 2019 17:46 UTC

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From: Ole Troan <otroan@employees.org>
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Subject: Re: Comments on raft-fz-6man-ipv6-alt-mark-01
Date: Fri, 1 Nov 2019 18:46:36 +0100
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To: Tom Herbert <tom@herbertland.com>
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DestOpt => measurement only  by node in DA
HBH => every router on the path with feature enabled
SRH TLV => every node along the SR path
DestOpt + SRH => every node along the SR path

Cheers 
Ole

> On 1 Nov 2019, at 18:33, Tom Herbert <tom@herbertland.com> wrote:
> 
> ´╗┐Hello,
> 
>> From the draft: "Regarding Hop-By-Hop Options Header, if we consider
> its real deployment, it is sometimes dropped by legacy devices and not
> so used by intermediate nodes.  Destination Options Header is
> preferred."
> 
> I don't think this is helpful guidance. First of all, it's not just
> Hop-by-Hop options that can be dropped, it's pretty much packets with
> any extension heades or atypical protocols that might be dropped by
> legacy devices-- including packets with Destination Options or Routing
> Headers. Neither does it make sense that Destination Options Header is
> preferred, as correctly stated in the previous paragraph DO and HBH
> address difference use cases (i.e. DO is end to end, and HBH is per
> hop). Saying that DO is preferred is equivalent to saying that
> end-to-end performance measurements are preferred which I doubt is the
> intent. IMO, this whole paragraph could be removed without loss of
> content.
> 
> "SRH TLV can also be a good choice from this point of view.  The
> intermediated nodes that are not in the SID list can consider the SRH
> as a green field, they cannot support and bypass or support and dig
> into the SRH TLV."
> 
> I disagree with the conclusion that SRH TLV is a good choice. The
> implicit assumption in this paragraph is that somehow SRH EH is less
> likely to be dropped by intermediate nodes than other EH like DO and
> HBH. I don't think there's any data to support that. Additionally,
> it's not clear what use case an SRH TLV addresses that can't already
> be addressed by Destination or HBH options.
> 
> Tom
> 
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