Re: [mpls-tp] [mpls] WG LC draft-lm-pwe3-mpls-tp-gal-in-pw-00.txt

[Robert Rennison <[e-mail]>]

Luca, Thomas,

A couple of clarification questions.

I'm trying to understand what the combination of the two drafts, -lm-pwe3-mpls-tp-gal-in-pw, and draft-nadeau-pwe3-vccv-2 amounts to.

So, I think I understood the draft-nadeau-pwe3-vccv-2 in that it's saying use VCCV type 1 where possible and if not then use the new type 4, whereby  in type 4 the exception mechanism is triggered by the use of the GAL,  and I appreciated the diagram in section 3 to lock this is, so far so good.

Now I read -pwe3-mpls-tp-gal-in-pw and I'm thinking , Ok these two drafts could work together since this one is trying to lay the "legal framework" i.e fix up the RFCs which mandated that the GAL could not be used with the PW.

Then I get hit with a brick wall in the form of the statements in the last 2 paras of section 3 of tp-gal-in-pw which state.

- Section 4.2<http://tools.ietf.org/html/draft-lm-pwe3-mpls-tp-gal-in-pw-00#section-4.2>. (GAL Applicability and Usage) in [RFC5586<http://tools.ietf.org/html/rfc5586>], the
      original text:

          In MPLS-TP, the GAL MUST be used with packets on a G-ACh on
          LSPs, Concatenated Segments of LSPs, and with Sections, and
          MUST NOT be used with PWs. It MUST always be at the bottom of
          the label stack (i.e., S bit set to 1). However, in other MPLS
          environments, this document places no restrictions on where
          the GAL may appear within the label stack or its use with PWs.

      is replaced by:

          In MPLS-TP, the GAL MUST be used with packets on a G-ACh on
          LSPs, Concatenated Segments of LSPs, and with Sections, and
          MAY be used with PWs. It MUST always be at the bottom of the
          label stack (i.e., S bit set to 1). However, in other MPLS
          environments, this document places no restrictions on where
          the GAL may appear within the label stack.


It's the bit about the GAL MUST be at the bottom of the label stack,  this is clearly inconsistent with what is proposed in the draft-nadeau-pwe3 where one can clearly see the GAL above the PW label and if one has to use  a GAL with a PW this would be the place to put it,

Now I can hear you saying "oh but look at the text below this, where we state .."However, in other MPLS environments , this document places no restrictions on where the GAL may appear within the label stack. This is consistent with draft-nadeau "   In which case I'd retort with ; what are we to do for PWs in   MPLS-TP, since what's in draft-nadeau would not be allowed ?

Clarification /explanation appreciated.

Cheers

Rob Rennison


From: [e-mail] [mailto:[e-mail]] On Behalf Of Alexander Vainshtein
Sent: Friday, March 11, 2011 2:22 PM
To: Greg Mirsky; Luca Martini
Cc: [e-mail]; [e-mail]; pwe3; HUANG Feng F; [e-mail]
Subject: Re: [mpls] WG LC draft-lm-pwe3-mpls-tp-gal-in-pw-00.txt

Greg, Luca,
As I've already stated in my comment on draft-nadeau-pwe3-vccv-2, IMHO it makes draft-lm-pwe3-mpls-tp-gal-in-pw completely useless.

My 2c,
     Sasha

From: [e-mail] [mailto:[e-mail]] On Behalf Of Greg Mirsky
Sent: Friday, March 11, 2011 9:14 PM
To: Luca Martini
Cc: [e-mail]; [e-mail]; pwe3; HUANG Feng F; [e-mail]
Subject: Re: [mpls] WG LC draft-lm-pwe3-mpls-tp-gal-in-pw-00.txt

Dear Luca,
thank you for bringing draft-nadeau-pwe3-vccv-2-01 to my attention. I'll send my comments to it in a separate e-mail.
I'll have to miss another opportunity to discuss your proposal in a meeting. Please add my comments below to my earlier expressed WG LC comments:

 *   the draft-lm-pwe3-mpls-tp-gal-in-pw-00 depends on any solution that addresses applicability of GAL in PW VCCV, e.g. solution proposed in draft-nadeau-pwe3-vccv-2-01;
 *   the draft-lm-pwe3-mpls-tp-gal-in-pw-00 needs to mention such dependency and refer to any existing proposal;
 *   I believe that the draft-lm-pwe3-mpls-tp-gal-in-pw-00 can be advanced in lock with document that addresses use of GAL in PW VCCV.
Regards,
Greg
On Fri, Mar 11, 2011 at 5:31 AM, Luca Martini <[e-mail]<mailto:[e-mail]>> wrote:
Greg ,
Some

On 02/18/11 11:15, Greg Mirsky wrote:
> Dear Luca,
> I see at least two issues:
>
>     * use of GAL for PW, in my view, is another VCCV CC type that has
>       to be negotiated as described in RFC 5085.
>
These are valid points, but this document in question does not define,
not discussed VCCV.
We have since posted a draft that proposes a new VCCV mode , and we
welcome comments regarding that document.
(draft-nadeau-pwe3-vccv-2-01.txt)

>     * use of GAL creates ambiguous situation when PW CW is used. The
>       benefit from extending GAL in PW, as I see, is for PWs that are
>       not required to use PW CW. That might be a good enough reason to
>       update RFC 5586 as proposed in the document but we must address
>       use cases of GAL in PWs that require presence PW CW. If we
>       prohibit or even discourage use of GAL for these PWs that have
>       PW VCCV as native Associated Channel, then architecture of ACh
>       for MPLS-TP PW not simplified as result of adopting the proposal.
>
> Regard
Greg,
The GAL is basically a notifier that the packet following the end of the
MPLS label stack, is explicitly defined as a G-ACH format.
Normally the packet would be decoded as an IP packet , unless the last
label on the stack indicated otherwise.

The GAL can certainly be applied  to a PW OAM packet on a PW that uses
the CW, and this document does not define that , nor restricts it.

The scope of this document is limited to removing an unnecessary
restriction in rfc5586, hence  this comment not applicable to this document.

Thanks.
Luca

> s,
> Greg
>
> On Fri, Feb 18, 2011 at 7:46 AM, Luca Martini <[e-mail]<mailto:[e-mail]>
> <mailto:[e-mail]<mailto:[e-mail]>>> wrote:
>
>     Greg,
>
>     Sorry, but I do not remember the point you mention.
>     Can you explain again here ?
>     Thanks.
>     Luca
>
>
>     On 02/17/11 23:47, Greg Mirsky wrote:
>     > Dear Authors and All,
>     > prior to the meeting in Bejing and acceptance of this proposal as WG
>     > document Luca and I agreed that use of GAL with PW VCCV presents a
>     > problem.
>     > I was not attending the IETF-79, nor I found discussion of this
>     issue
>     > in the minutes. I think that this issue should be specified,
>     > explained. In my view, this document updates not only RFC 5586
>     > but RFC 5085 too.
>     >
>     > Regards,
>     > Greg
>     >
>     > Comment to draft-lm-pwe3-mpls-tp-gal-in-pw-00.txt
>     >
>     > On Sat, Oct 30, 2010 at 10:14 AM, Luca Martini
>     <[e-mail]<mailto:[e-mail]> <mailto:[e-mail]<mailto:[e-mail]>>
>     > <mailto:[e-mail]<mailto:[e-mail]> <mailto:[e-mail]<mailto:[e-mail]>>>> wrote:
>     >
>     >     Greg,
>     >
>     >     You are correct , the proposed update does not propose any
>     changes
>     >     to VCCV.
>     >     However the problem with vccv is not as simple as to ask for
>     a new
>     >     code point from IANA.
>     >     Given the good amount of discussion on this point, we should
>     >     probably have a discussion in Beijing.
>     >
>     >     Luca
>     >
>     >
>     >
>     >     On 10/29/2010 05:07 PM, Greg Mirsky wrote:
>     >>     Dear Authors,
>     >>     I think that proposed update of the Section 4.2. RFC 5586
>     makes it possible
>     >>     to use GAL on MPLS-TP PW that uses Control Word. I consider
>     it to be
>     >>     conflict between PW VCCV CC types because use of GAL is not
>     negotiated
>     >>     through PW VCCV negotiation. To avoid such situation I propose:
>     >>
>     >>        - in Section 5 request IANA to assign new CC Type "MPLS
>     Generic
>     >>        Associated Channel Label"
>     >>        - assign precedence to new CC Type that affects Section
>     7 RFC 5085
>     >>
>     >>     Regards,
>     >>     Greg
>     >>
>     >>
>     >>
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