RE: [ippm] Mail regarding draft-fz-6man-ipv6-alt-mark

Dear Bob, Tom,
Thanks a lot for your review of the draft. Much appreciate.
Please find my answers inline tagged as [GF].

Best Regards,

Giuseppe

-----Original Message-----
From: Bob Hinden [mailto:bob.hinden@gmail.com] 
Sent: Saturday, October 19, 2019 7:08 PM
To: IPv6 List <ipv6@ietf.org>; IETF IPPM WG <ippm@ietf.org>
Cc: Bob Hinden <bob.hinden@gmail.com>; Haoyu Song <haoyu.song@futurewei.com>; draft-fz-6man-ipv6-alt-mark@ietf.org; Tom Herbert <tom@quantonium.net>
Subject: Re: [ippm] Mail regarding draft-fz-6man-ipv6-alt-mark

Hi,

I did a quick read of this draft and have a few comments.

It appears to be defining a new IPv6 extension header.   It should say that in the title and be described in the abstract.

[GF]: I will do.

   This document defines how the alternate marking method can be used to
   measure packet loss and delay metrics of IPv6 and SRv6.

As Tom mentioned, SRv6 is part of IPv6, they are not separate things.

[GF]: Sure, we meant that it can be applicable to IPv6 and, as a consequence, also to SRv6. We will specify it better in the next revision. 

   The IPv6 Header Format defined in [RFC8200] introduces the format of
   the IPv6 addresses, the Extension Headers in the base IPv6 Header and
   the availability of a 20-bit flow label, that can be considered for
   the application of the Alternate Marking methodology.  In this

RFC8200 does not define the format of IPv6 addresses.  That is done in RFC4291.

[GF]: Yes, we will add the reference to RFC4291.

This draft appears to depend on a number of IPPM documents, but none are listed as normative references.

[GF]: We will review the dependencies. In particular we may need to cut the reference to draft-zhou-ippm-enhanced-alternate-marking and leave only RFC 8321 and draft-ietf-ippm-multipoint-alt-mark.

One of these is RFC 8321, but that has status of Experimental.  I don’t think this document can be Standards track if it depends on an Experimental RFC.

[GF]: Consider that RFC 8321 was classified as Experimental since it describes a methodology that came from lab experience. In particular, the first example of application was with IP packets where there is no space for marking and we reused the DSCP field for our scope. However the applicability of the method is general and, in this draft, the new IPv6 extension header introduces an appropriate marking field that would be dedicated only for the alternate marking method and not for other purposes. So we refer to RFC 8321 just for information and this does not necessarily imply that the draft should be experimental, therefore it could be discussed.

In the EH definition in Section 3.1.1 there is a field called "Flow ID".  I can’t tell if this is the same or different from the IPv6 flow label defined in RFC8200 and RFC6437.   This should be clarified and justified.

[GF]: Of course, it is a separate field and we will make it clearer in the next version.

Bob

> On Oct 19, 2019, at 8:32 AM, Tom Herbert <tom@quantonium.net> wrote:
> 
> On Fri, Oct 18, 2019 at 1:30 AM Haoyu Song <haoyu.song@futurewei.com> wrote:
>> 
>> I just read this draft and I think it’s an implementation of the draft [I-D.zhou-ippm-enhanced-alternate-marking], which discusses the method of encapsulating the enhanced alternate marking header in IPv6. I have several comments.
>> 
>> 
>> 
>> It doesn’t cover the encapsulation on SRv6 yet and I think a solution for SRv6 would be more useful.
> 
> SRv6 _is_ a subset IPv6. It is one type of routing header. Like any 
> other use case of IPv6, HBH and destination options are useable when
> SRv6 header is present. Because SRv6 is a routing header destination 
> options before the routing header are processed by each destination in 
> the route list.
> 
>> More deployment consideration discussion should be given when it’s 
>> encapsulated in HBH EH
> 
> In what regard?
> 
>> The document mentioned two PBT modes discussed in [I-D.song-ippm-postcard-based-telemetry]. Since the PBT-I variation has been merged in another draft [I-D.ioamteam-ippm-ioam-direct-export], this draft may need to be updated accordingly.
>> 
>> 
>> 
>> Thanks!
>> 
>> 
>> 
>> Haoyu
>> 
>> _______________________________________________
>> ippm mailing list
>> ippm@ietf.org
>> https://www.ietf.org/mailman/listinfo/ippm
> 
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