Re: RE : RE : TR : I-D ACTION:draft-leroux-ccamp-gmpls-mrn-eval-00.txt

[Igor Bryskin <i_bryskin@yahoo.com>]

Dimitri,

See at the bottom

> >
> >IB>>Well, are they? They give you a way to signal a
> >requirement not to commit resources for an LSP
until
> >further notice and also to require their commitment
> >when it becomes necessary. Why not to allow working
> >LSP to be signaled as Secondary according to the
> >mentioned draft? Then it would be possible even to
> >signal protected virtual FAs, which is not as
stupid
> >as it may sound :=)
>
> Sorry but this sounds really bad...
> Please let me know then how do you signal protected
virtual FAs?
>
> IB>> You signal both working and protection LSPs of
the FA as Secondary.
At
> the time when you decide to make FA "real" you
re-signal working or both
> LSPs (depending on protection type) as Primary.
Don't see why this
wouldn't
> work.
>
> DP> because what do you do in case the primary
(virtual) FA-LSP fails ?
you
> are simply going to activate the secondary (virtual)
FA-LSP which is in
> clear
> opposition with the notion of virtual-FA - the
reason is again because you
> are trying to use one bit i.e. S to say something in
a context (protection
> object) for which it has not been designed for
>

IB>> Oh-Oh, what do you mean by "primary (virtual)
FA-LSP fails" and  "you
are simply going to activate the secondary (virtual)
FA-LSP "?  I activate
protection LSP if I have a failure in the *data plane*
of the working LSP.
But working LSP of the virtual FA does not have any
data plane yet, there is
nothing that can trigger the protection LSP activation
and switchover.

DP> but they are associated to resources they do not
use - and the control plane role is to ensure that
when they need to be activated resources can be used -
the question JL raises is the problem of "how do i
protect a virtual FA" and the response is if you are
using the S bit for telling i am a virtual FA you can
not use it anymore to ensure protection of a primary
(and even less a secondary !) - this said an secondary
LSP exists only within the context of its primary

IB>>Here is what I have in mind.

A network operator configures a mesh of virtual FAs.
Working FA LSPs are signaled as Secondary. Once they
are established the FA TE link ends are advertised.
Resources for these LSPs are allocated on the links
the LSPs are going through, however, they are not
committed (not bound into cross-connects). Two or more
virtual FA LSPs may share the resources on common
links. This is especially true for those of them that
are unlikely to become real at the same time.
Furthermore, polices could be such that virtual FA LSP
resources could be allowed to get pre-empted by real
(not necessarily FA-) LSPs. The mentioned resources
also could be involved in mesh restoration schemes and
even be bound into extra traffic LSPs. 

When a virtual FA transforms into real FA, its working
FA-LSP is re-signaled as Primary. At this time, the
allocated resources are bound into FA-LSP
cross-connects. Naturally, all other LSPs ? virtual or
real ? that share resources with the FA-LSP in
question are notified and need to be recomputed and/or
re-signaled.

A virtual FA could be provisioned as protected in a
sense that when it becomes real it will have a certain
protection scheme already in place. Path computation
for backup LSPs of virtual FAs is performed just like
of real FAs, that is, by assuming that associated
working LSPs are Primary (fully built) LSPs.
Regardless of the protection type backup LSPs of
virtual FAs are always signaled as Secondary. At the
time when a virtual FA is transformed into real one
(that is, when its working LSP becomes Primary) its
backup LSP(s) may be activated as well (e.g. 1+1
protection) or may be left Secondary until the working
LSP data plane failure is detected (e.g. shared
protection).

Igor





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