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

Dear Tom, Ole,
Thank you for your feedback.
Agree, it is better to be general and avoid any definitive conclusion about HBH, DestOpt and SRH TLV.
I will update that paragraph accordingly and will publish a new revision soon.

Regards,

Giuseppe

-----Original Message-----
From: ipv6 [mailto:ipv6-bounces@ietf.org] On Behalf Of Ole Troan
Sent: Friday, November 1, 2019 7:16 PM
To: Tom Herbert <tom@herbertland.com>
Cc: 6man <ipv6@ietf.org>
Subject: Re: Comments on raft-fz-6man-ipv6-alt-mark-01

> On 1 Nov 2019, at 18:57, Tom Herbert <tom@herbertland.com> wrote:
> 
> On Fri, Nov 1, 2019 at 10:46 AM Ole Troan <otroan@employees.org> wrote:
>> 
>> 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
>> 
> Ole,
> 
> So the last two have identical effects, hence we've introduced the 
> complexity or redundant protocol mechanisms.

Yes, that should guide us in making choices here. 

Ole

> 
> Tom
> 
>> 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
>>> 
>>> --------------------------------------------------------------------
>>> IETF IPv6 working group mailing list ipv6@ietf.org Administrative 
>>> Requests: https://www.ietf.org/mailman/listinfo/ipv6
>>> --------------------------------------------------------------------

--------------------------------------------------------------------
IETF IPv6 working group mailing list
ipv6@ietf.org
Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6
--------------------------------------------------------------------