Subject: Re: [mpls] draft-george-mpls-ipv6-only-gap-04.txt

From: "Rajiv Asati (rajiva)" <[email-masked]>
Date: Sat, 8 Mar 2014 07:28:43 +0000

Hi Alan,

Sorry about the delay, please see inline,

> I am concern that for a gap analysis, it starts getting prescriptive,
> along the lines of a framework, only really in one place having now read
> the doc e2e.
> - Section 3.2.2 on mLDP starts mining the solution space for expressing
> interworking or overlay of root addresses.

Good catch. This section needs to be updated (related to the next point).

> Reading 3.2.2 and subsequent sections does raise a question. The issue in
> 3.2.2 is a tree that spans contiguous IPv4 and IPv6 operational domains,
> and expressing a routable root is a problem. Yet RSVP and PCE are assumed
> to have no gaps. 

You do raise a good point. We should remove this v4-only and v6-only
co-existence scenario from mLDP point#2 altogether.

> Is the assumption that an ERO will include a node that
> would know how to treat hops that change address families, and IF so
> doesn't that mean there are loose hops that will not work? E.g. a hop
> that transits a v4 only and v6 only domain, but with no dual stack LSR
> identified? (using the example from 3.2.2 the ERO is (R1, R3, R4, R5,
> R6), if R2 is not there would not R1 be clueless about getting to R3?).

IMO, RSVP doesn¹t suffer from this problem, since the Path-calculation
(CSPF) would not end up concluding v4-only and v6-only hops to the
tail-end, hence, ERO would have either all v4-only or v6-only hops or none.

> Section 3.3.1, I might be worth mentioning the impact of requiring
> homogenous capability end points in a VPLS network architecture or S-PEs
> for MS-PW for that matter.

You mean, the PE routers (connecting a PW) must be of the same AFI !! I
agree.

> Section 3.4.2, seems to me to fall under the general class of TTL
> expiring for a ping message from an unroutable address. Which in a VPN
> context is nothing new and not unique to v4/v6 operation, it has always
> been a head wound. And there are practices to at least partially mitigate
> the impact. So IMO there is a gap, and that's "tough!" ;-)

Ditto. The intent (for now) is to document the gap, whether it could be
sufficiently solved or not. :) We may end up borrowing the same solution
if we were to solve it later on.

-- 
Cheers,
Rajiv Asati 

-----Original Message-----
From: <George>, Wes George <[email-masked]>
Date: Tuesday, February 18, 2014 at 4:05 PM
To: "[email-masked]"
<[email-masked]>, Rajiv Asati
<[email-masked]>, "Kamran Raza (skraza)" <[email-masked]>, Ronald
Bonica <[email-masked]>, Rajiv Papneja <[email-masked]>,
Dhruv Dhody <[email-masked]>, Vishwas Manral
<[email-masked]>, Nagendra Kumar <[email-masked]>
Subject: FW: draft-george-mpls-ipv6-only-gap-04.txt

>More feedback on the draft that goes beyond my capability to address.
>
>Note - it¹s unclear to me whether the draft email alias still sends email
>to everyone that was originally listed as an author, or only to carlos and
>I as the listed authors on the current draft. Can one of you confirm that
>you received (or definitely did not receive) this message when it was
>originally sent to the draft alias on the 15th so that I know whether I
>need to keep watching for messages like this and parsing them out to the
>authors?
>
>
>Thanks,
>
>Wes
>
>
>
>
>
>On 2/15/14, 1:22 PM, "David Allan I" <[email-masked]> wrote:
>
>>HI There:
>>
>>So being stuck in SFO for an unexpected LONG sojourn provided me with
>>some serendipitous time to look over this.
>>
>>In general I found the document to be well written and clear, and it
>>appears to have both merit and utility. I'm less able to comment on
>>completeness.
>> If I understand correctly, I believe the general class of problem being
>>explored by the I-D overall is a homogenous end point set and the
>>potential issues with a heterogenous core and the completeness of the
>>IPv6 feature set in the set of homogenous IPv6 end points. The actual
>>application of that to some of the analysis does not seem to acknowledge
>>that basis, and I think some use case boilerplate along those lines would
>>help drive some conclusions and confidence in the gap/no gap
>>pronouncements.
>>
>>I am concern that for a gap analysis, it starts getting prescriptive,
>>along the lines of a framework, only really in one place having now read
>>the doc e2e.
>>- Section 3.2.2 on mLDP starts mining the solution space for expressing
>>interworking or overlay of root addresses.
>>
>>Technical comments:
>>
>>Reading 3.2.2 and subsequent sections does raise a question. The issue in
>>3.2.2 is a tree that spans contiguous IPv4 and IPv6 operational domains,
>>and expressing a routable root is a problem. Yet RSVP and PCE are assumed
>>to have no gaps. Is the assumption that an ERO will include a node that
>>would know how to treat hops that change address families, and IF so
>>doesn't that mean there are loose hops that will not work? E.g. a hop
>>that transits a v4 only and v6 only domain, but with no dual stack LSR
>>identified? (using the example from 3.2.2 the ERO is (R1, R3, R4, R5,
>>R6), if R2 is not there would not R1 be clueless about getting to R3?).
>>
>>Section 3.3.1, I might be worth mentioning the impact of requiring
>>homogenous capability end points in a VPLS network architecture or S-PEs
>>for MS-PW for that matter.
>>
>>Section 3.4.2, seems to me to fall under the general class of TTL
>>expiring for a ping message from an unroutable address. Which in a VPN
>>context is nothing new and not unique to v4/v6 operation, it has always
>>been a head wound. And there are practices to at least partially mitigate
>>the impact. So IMO there is a gap, and that's "tough!" ;-)
>>
>>I hope this helps
>>Dave
>>-----Original Message-----
>>From: Loa Andersson [mailto:[email-masked]]
>>Sent: Saturday, February 15, 2014 12:07 AM
>>To: David Allan I; Mach Chen; Markus Jork;
>>[email-masked];
>>[email-masked]; VIGOUREUX, MARTIN (MARTIN); Aissaoui,
>>Mustapha (Mustapha)
>>Subject: draft-george-mpls-ipv6-only-gap-04.txt
>>
>>Dave, Mach, Markus and Mustapha,
>>
>>You have been selected as MPLS Review team reviewers for
>>draft-george-mpls-ipv6-only-gap-04.
>>
>>Note to authors: You have been CC'd on this email so that you can know
>>that this review is going on. However, please do not review your own
>>document.
>>
>>Note 2: All the IPv& expertise we have in the MPLS review team are listed
>>as contributors on this draft. I've therefore asked Mustapha to review.
>>
>>Reviews should comment on whether the document is coherent, is it useful
>>(ie, is it likely to be actually useful in operational networks), and is
>>the document technically sound?  We are interested in knowing whether the
>>document is ready to be considered for WG adoption (ie, it doesn't have
>>to be perfect at this point, but should be a good start).
>>
>>Reviews should be sent to the document authors, WG co-chairs and WG
>>secretary, and CC'd to the MPLS WG email list. If necessary, comments may
>>be sent privately to only the WG chairs.
>>
>>Are you able to review this draft by March 1, 2014?
>>
>>
>>Thanks, Loa
>>(as MPLS WG chair)
>>--
>>
>>
>>Loa Andersson                        email: [email-masked]
>>Senior MPLS Expert                          [email-masked]
>>Huawei Technologies (consultant)     phone: +46 739 81 21 64
>
>
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