Re: [mpls-tp] about open discussion about MIP MEP in MPLS-TP networks

[Alexander Vainshtein <[e-mail]>]

Italo,
I will re-read Section 3.8 to check if it addresses the issue.
regards,
Sasha________________________________________
From: BUSI, ITALO (ITALO) [[e-mail]]
Sent: Friday, November 26, 2010 3:08 PM
To: Alexander Vainshtein
Cc: [e-mail]; Maarten Vissers; [e-mail]
Subject: R: [mpls-tp] about open discussion about MIP MEP       in      MPLS-TP networks

Sasha,

> I see two possibilities for resolving the issue:
>
> 1. You can withdraw the current SPME concept from the draft. Whether you
> replace it with another solution for the
>    problem or not SPME is supposed to solve or not, is not so relevant at
> the moment.
> 2. You retain the current SPME concept but add clarifications and caveats
> pertaining to the issue raised.
>    By doing that you transfer the responsibility for using this concept
> and dealing with the potentially
>    useless results to the operators.

Actually section 3.8 was added to "add clarifications and caveats pertaining to the issue raised" so I think we have already adopted the solution 2. you proposed above.

The individual drafts I referred to (together with a reference to section 3.8) are discussing detailed requirements and solutions to resolve this problem.

Italo

> -----Messaggio originale-----
> Da: Alexander Vainshtein [mailto:[e-mail]]
> Inviato: martedì 23 novembre 2010 15.33
> A: BUSI, ITALO (ITALO)
> Cc: [e-mail]; Maarten Vissers; [e-mail]
> Oggetto: RE: [mpls-tp] about open discussion about MIP MEP in MPLS-TP
> networks
>
> Italo,
> In this message I will only refer to the SPME issue (which I am raising as
> the IETF LC comment on the MPLS-TP FW draft).
> I have added Dave Allan (your co-editor) to the CC list.
>
> This is how I see the situation after reading your email:
>
> 1. I have, some time ago, raised a technical issue with the proposed SPME
> concept, namely that the results of
>    SPME monitoring are not necessarily correlated with the behavior of
> traffic in the original monitored LSP.
>    My original comment has been discussed on the MPLS-TP mailing list for
> some time.
> 2. In your email you agree that this issue is real, and even refer to some
> individual drafts
>    that have raised the same issue.
> 3. Nevertheless, you, as the co-editor of the draft, retain the SPME
> concept "as is" in the WG document now in the
>    final round IESG discussions before approval for publication as an RFC.
> And the current version
>    of the draft, while discussing some specific aspects of SPME,
> completely ignores a known issue with SPME.
>
> I do not think that it is reasonable to expect that the target audience of
> the RFC-to-be has followed the discussion of the draft on this mailing
> list, or read some individual submissions dealing with one of the concepts
> introduced in the draft (and which are not even referenced in the draft).
> Hence, IMHO and FWIW, if the draft were approved for publication as an RFC
> "as is", it would be misleading its target audience regarding actual
> usefulness of SPME.
>
> I see two possibilities for resolving the issue:
>
> 1. You can withdraw the current SPME concept from the draft. Whether you
> replace it with another solution for the
>    problem or not SPME is supposed to solve or not, is not so relevant at
> the moment.
> 2. You retain the current SPME concept but add clarifications and caveats
> pertaining to the issue raised.
>    By doing that you transfer the responsibility for using this concept
> and dealing with the potentially
>    useless results to the operators.
>
> Hopefully these notes clarify my position on the subject.
>
> Regards,
>      Sasha
>
> -----Original Message-----
> From: BUSI, ITALO (ITALO) [mailto:[e-mail]]
> Sent: Monday, November 22, 2010 8:06 PM
> To: Alexander Vainshtein; Maarten Vissers
> Cc: [e-mail]
> Subject: R: [mpls-tp] about open discussion about MIP MEP in MPLS-TP
> networks
>
> Sasha,
>
> See my comments in line marked with [ib]
>
> Thanks, Italo
>
> > -----Messaggio originale-----
> > Da: Alexander Vainshtein [mailto:[e-mail]]
> > Inviato: lunedì 22 novembre 2010 14.41
> > A: Maarten Vissers
> > Cc: [e-mail]; BUSI, ITALO (ITALO)
> > Oggetto: RE: [mpls-tp] about open discussion about MIP MEP in MPLS-TP
> > networks
> >
> > Maarten,
> >
> > Please see some answers inline below.
> > I will snip the fragments where we seem to be in agreement in hope that
> > this will improve readability.
> >
> > Regards,
> >      Sasha
> >
> >
> > -----Original Message-----
> > From: Maarten Vissers [mailto:[e-mail]]
> > Sent: Monday, November 22, 2010 12:50 PM
> > To: Alexander Vainshtein; 'BUSI, ITALO (ITALO)'
> > Cc: [e-mail]
> > Subject: RE: [mpls-tp] about open discussion about MIP MEP in MPLS-TP
> > networks
> >
> > Sasha,
> >
> > See inline...
> >
> > > -----Original Message-----
> > > From: [e-mail] [mailto:[e-mail]] On
> > > Behalf Of Alexander Vainshtein
> > > Sent: 15 November 2010 08:03
> > > To: BUSI, ITALO (ITALO)
> > > Cc: [e-mail]
> > > Subject: Re: [mpls-tp] about open discussion about MIP MEP in MPLS-TP
> > > networks
> > >
> > > Italo,
> > > Lots of thanks for a prompt response.
> > >
> > > I will look up my archives and resend the specific comment regarding
> > > SPME.
> > > But the gist of this comment has been, that SPME is a new LSP, so that
> > > monitoring it does not necessarily say anything about the original LSP
> > > passing thru the segment in question. The simplest use case
> > > demonstrating the difference is a case of incomplete configuration,
> > > when the original LSP has not been configured in one of the internal
> > > nodes of the segment, but SPME was (and vice versa).
> > [[[Sasha]]] Looks like you've decided not to comment on this point.
> > Does it mean that you agree with me that there is an issue with SPME?
> > >
>
> [ib] I think there is not disagreement here: see section 3.8 of the OAM
> Framework well as draft-koike-mpls-tp-temporal-hitless-psm and draft-
> zhang-mpls-tp-path-segment-monitoring.
>
> > > Regarding MIPs, I'd like to explain my doubts.
> > >
> > > 1. We all agree (or so it seems) that intermediate points of LSPs and
> > > PWs can only be reached due to TTL expiration.
> >
> > [maarten] That is what MPLS experts tell me; so this is the assumption
> for
> > MPLS-TP.
> > [[[Sasha]]] Great! So at least here we are on the same page.
> >
>
> [ib] I think this is described in section 3.4 of the OAM Framework:
>
>    When sending an OAM packet to a MIP, the source MEP should set
>    the TTL field to indicate the number of hops necessary to reach
>    the node where the MIP resides.
>
>    The source MEP should also include Target MIP information in the
>    OAM packets sent to a MIP to allow proper identification of the
>    MIP within the node. The MEG the OAM packet is associated with
>    is inferred from the MPLS label.
>
> [ib] I am less familiar with the MIP/MEP Map draft but when I read it I
> understood it to be aligned with the OAM Framework.
>
> > > 2. By default TTL expiration extracts a packet from the data plane and
> > > sends it to the control plane instead.
> >
> > [maarten] see my previous email. Packet transport network equipment
> > without
> > control plane are required to support MIP functions as well.
> > [[[Sasha]]] I've already explained that in a separate email.
> >
> > >     As per RFC 4379, this process includes preservation of the
> original
> > > received label stack
> > >     and noting the actual ingress interface so that they are available
> > > for the CP processing.
> >
> > [maarten] in nodes with and without control plane these OAM packets have
> > to
> > be processed as if the MIP is functionally located on the ingress port.
> > [[[Sasha]]] Please note that this is basic MPLS data plane functionality
> > that does not depend on configuration of MIPs. Or, if you prefer it in a
> > different way, a per-node MIP is by default enabled in any MPLS node.
> >
>
> [ib] I think that neither the OAM Framework nor the MIP/MEP Map precludes
> the implementation of per-node MIPs. However, they allow also the