The MPLS WG Archive

[Lou Berger <lberger@labn.net>]

JL,

See below.

At 03:20 AM 6/23/2006, LE ROUX Jean-Louis RD-CORE-LAN wrote:

>Hi Lou,
>
>When RRO is not used this procedure does not 
>apply and remerge should be fixed in the data plane on the remerge node.

"fixing in the data plane" doesn't work for all 
technologies covered in the spec, e.g., GMPLS optical.

(You're making me think about my favorite HL Mencken quote...)

>IMO full RRO inclusion is the price to pay if 
>you want to fix remerge in a simple manner in the control plane.

Yes, but there is already a defined, documented, 
and agreed to mechanism that will work for all 
the cases.  De we really want/need to be making 
such a significant change at this late date (post 
WG last call!).  If it were broken, then certain 
a change would be needed, but I haven't heard anyone make such an assertion.

Lou

>Regards,
>
>JL
>
> > -----Message d'origine-----
> > De : Lou Berger [mailto:lberger@labn.net]
> > Envoyé : vendredi 23 juin 2006 05:51
> > À : LE ROUX Jean-Louis RD-CORE-LAN
> > Cc : zzx-rahul@juniper.net; mpls@ietf.org; Drake, John E
> > Objet : RE: [mpls] TR: working group last call
> > ondraft-ietf-mpls-rsvp-te-p2mp-05.txt
> >
> > JL,
> >
> > So what happens when no RRO is used (which isn't currently
> > required) or portions of the RRO are removed?
> >
> > Lou
> >
> > At 02:03 AM 6/22/2006, LE ROUX Jean-Louis RD-CORE-LAN wrote:
> >
> > >Hi Rahul, all
> > >
> > >Actually, after thinking a bit more, it seems to me that a simpler
> > >remerge procedure based on RRO analysis could be useful.
> > >If the RRO is carried in Path messages, the node where the remerge
> > >occurs could easily identify the node that created the
> > remerge, simply
> > >by analyzing the two RROs.
> > >When a node detect a remerge it sends a PAthErr with a new object
> > >(Remerge-Spec object) that identifies the remerge origin.
> > This PathErr
> > >carries the set of sub-LSPs received in the Path message that caused
> > >the remerge.
> > >On receipt of such PAthErr, a node that see its own address in the
> > >Remerge-spec object moves the set of sub-LSPs...
> > >
> > >It seems that this procedure would require simpler processing...
> > >It requires the use of RRO, but this is the price to pay.
> > >
> > >Would that make sense?
> > >
> > >Best Regards,
> > >
> > >JL
> > >
> > >
> > > > -----Message d'origine-----
> > > > De : Drake, John E [mailto:John.E.Drake2@boeing.com]
> > Envoyé : mardi
> > > > 20 juin 2006 23:59 À : zzx-rahul@juniper.net; LE ROUX Jean-Louis
> > > > RD-CORE-LAN Cc : mpls@ietf.org Objet : RE: [mpls] TR:
> > working group
> > > > last call ondraft-ietf-mpls-rsvp-te-p2mp-05.txt
> > > >
> > > > Rahul,
> > > >
> > > > Snipped, comments inline.
> > > >
> > > > Thanks,
> > > >
> > > > John
> > > > > > > 4: Section 18.1.1 Remerge Procedure
> > > > > > >
> > > > > > > The text says
> > > > > > >    "The PathErr message MUST include all of the objects
> > > > > > >    normally included in a PathErr message, as well as
> > > > one or more
> > > > SUB-
> > > > > > >    LSP objects from the set of sub-LSPs associated with the
> > > > matching
> > > > > > >    P2MP LSP Path state.  A minimum of three SUB-LSP
> > objects is
> > > > > > >    RECOMMENDED. This will allow the node that caused
> > > > the re-merge
> > > > to
> > > > > > >    identify the outgoing Path state associated with
> > the valid
> > > > > > > portion of
> > > > > > >    the P2MP LSP. The set of SUB-LSP objects in the
> > > > received Path
> > > > > > > message
> > > > > > >    MUST also be included"
> > > > > > >
> > > > > > > And then:
> > > > > > >
> > > > > > >    "A node that receives a PathErr message that
> > > > contains the Error
> > > > > > > Value
> > > > > > >    "Routing Problem/P2MP Remerge Detected" MUST
> > > > determine if it is
> > > > the
> > > > > > >    node that created the re-merge case.  This is done
> > > > by checking
> > > > > > >    whether there is any intersection between the set of
> > > > > > > SUB-LSP objects
> > > > > > >    associated with the matching P2MP LSP Path state and
> > > > the set of
> > > > > > > SUB-
> > > > > > >    LSP objects in the received PathErr message.  If
> > > > there is, then
> > > > the
> > > > > > >    node created the re-merge case."
> > > > > > >
> > > > > > > There is an issue here. Actually there will always be an
> > > > > > > intersection, because the PathErr includes the set
> > of sub-lsp
> > > > > > > objects in the received Path... IMO for this procedure
> > > > to work the
> > > > > > > PathErr MUST only include sub-LSP objects
> > associated with the
> > > > > > > matching P2MP LSP state on the rermerge LSR and must
> > > > not include
> > > > > > > the set of SUB-LSP objects in the received Path message.
> > > > > > > By the way why are three objects recommended?
> > > > > > >
> > > > >
> > > > > I believe this was clarified by John Drake offline and no
> > > > > revisions
> > > > were
> > > > > needed ?
> > > > Rahul,
> > > >
> > > > Here's the e-mail I sent to JL:
> > > >
> > > > "JL,
> > > >
> > > > The text was originally stated as you stated.  The issue
> > is that the
> > > > set of sub-LSPs associated with the interface on the node that
> > > > caused the re-merge condition may have more members than
> > the set of
> > > > sub-LSPs in the received Path message, and you only want
> > to move the
> > > > ones that were in the received Path message.
> > > >
> > > > Adrian was the one who initially pointed this and he proposed
> > > > creating a different object/type for the set of sub-LSPs in the
> > > > received Path message. I think this is reasonable solution.
> > > >
> > > > Thanks,
> > > >
> > > > John"
> > > >
> > > > As you can see from the last paragraph, we do need to
> > create a new
> > > > object/type.
> > > >
> > >
> > >_______________________________________________
> > >mpls mailing list
> > >mpls@lists.ietf.org
> > >https://www1.ietf.org/mailman/listinfo/mpls
> >
> >


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