RE: RPR protection with MPLS

My understanding as to which layer will respond first to a failure is
dependent on what trigger and protocol timer expires first. If RPR
takes more than some amount of time to respond to a failure
and FRR is configured and optimized, MPLS could respond first
before the ring. If anyone knows this cannot happen then please
speak up. Since both RPR and FRR are capable of responding
to a failure within a small amount of milliseconds, plus FRR is
usually planned with consideration of layer 1 topology and properties
such as latency, it seems to me that we need to understand the
coupling effect when there is a failure.

Thanks,
Helen.

At 12:09 PM 11/12/2002 -0800, nitin panjwani wrote:

>Hi David and all,
> > > >However if RPR protection fails, MPLS should be
> > triggered to
> > > protect. The exact method of doing it could be an
> > IPORPR
> > > discussion topic, with timeouts being one of the
> > options (so
> > > MPLS could be configured to ignore failures unless
> > they
> > > persist for more than say 100ms, which would
> > indicate a
> > > failure of the underlying RPR layer)
> > >
> > > Two questions
> > > 1. When the 802.17 ring has a failure and invokes
> > its protection
> > >    procedure, do the higher layers see it as a
> > brief failure in
> > >    the link (i.e. there is an "interface down"
> > event followed a
> > >    few ms later by an "interface up" event) or
> > does it happen
> > >    transparently, with no interface failure (i.e.
> > it would appear
> > >    to the higher layers as just a brief moment of
> > packet loss)
> > >
> > It is the later as the RPR will steer/wrap in less
> > than 50msec.
> >
> > > 2 If an 802.17 ring fails and can not go into
> > single-ring-mode
> > >   for some reason, wouldn't it appear as a link
> > failure to MPLS
> > >   causing MPLS mechanisms to invoke fast reroute,
> > just as if, say,
> > >   a PPP link went kablooey or an ethernet lost its
> > ether?
> > >
> > RPR failure is segment failure (not sure what you
> > mean by single-ring-mode)
> > i.e. you loose a segment between two nodes. If you
> > have more than one
> > failure any connection that cannot access the
> > isolated nodes in the middle
> > between those failures is lost. I believe it is
> > implementation specific
> > whether to wait for the MPLS timeout to detect it or
> > report immediately back
> > to the MPLS to invoke backward that re-route is
> > required. This is something
> > we can work out in the WG.
>Shouldn't it be something like: either RPR or MPLS
>protection will take charge of rerouteing the traffic;
>and one which assures minimum packate loss and delay
>will win and take charge.
>On this, usually upper layer(MPLS) depends on the
>lower layer(RPR)(as it simplifies the implementation
>and serves the perfect goal of layering approach)and
>shouldn't it be upto MPLS to decide wheathet to take
>charge of protection or wait for RPR, depending on how
>critical network and the passing traffic is(this
>should be configurable).
>Please correct me.
>
>Tahnks,
>Nitin
>
>
>
>
>
>
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