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MPLSOAM BOF revised minutes
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From: "Abarbanel, Benjamin" <Benjamin.Abarbanel@Marconi.com>
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Date: Wed, 19 Dec 2001 11:11:53 -0500
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Cc: "'mpls@UU.net'" <mpls@UU.NET>
Title: RE: MPLSOAM BOF revised minutes
Why
dont we call MPLS "The Adoptation Layer". It adopts various kinds of Layer 2 to
the IP Layer 3.
The
paradigm offcourse can work on other layer 3s as well. This way everyone is
happy and the
mechanism is preserved according to its long list of
designers. I hope the GMPLS people will be
satisfied as well.
I
think the use of the shim header and what it contains, is only incidental to
what adoptations are
being
performed.
Ben
Yakov
I think MPLS is a layer in its own right.
You replied to Shahram that forwarding information is not
in the shim header. My experience with many routers
that
use ATM is in practice that they ONLY put the
forwarding
information in the SHIM header and use the
ATM VC/VP as a
pipe. Things would be better if they
would follow the drafts
you quote from below. I don't
know yet how they will interpret
the GMPLS specs but
if they follow the ATM example there will
be a extra
shim header there as well.
Don
> -----Original Message-----
>
From: Yakov Rekhter [mailto:yakov@juniper.net]
> Shahram,
>
>
> > While we are busy arguing about whether MPLS is a separate
> > > layer or not,
> > > please bear in mind that the whole concept of a layer
assumes
> > > (among other
> > > things) a single format for transport of the data from
the
> > > layer above.
> > > Since MPLS doesn't make such an assumption (as in some
> cases it uses
> >
> the "shim" header, in other cases it uses the VCI/VPI,
> > > etc...) one could
> > >
conclude that perhaps MPLS doesn't fit into the
>
traditional layering
> > > model at
all.
> >
> > It
seems that you have confused the "layer above" with the
> "layer below".
> > X over MPLS
always requires a Shim header.
>
> First of all, in the case of ATM-LSRs the presence of the shim
header
> strictly speaking is not mandatory.
Second, even when the shim header
> is present with
ATM-LSRs, the forwarding information used by
>
ATM-LSRs is
> *not* in the shim header, but in
VCI/VPI fields of the ATM
> cell header.
> Finally, in GMPLS there is no shim header at
all.
>
> Yakov.
>
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