RE: [PWE3] status signalling of MPLS PW state

[David Zelig <Davidz@corrigent.com>]

Luca,

> 
> David Zelig wrote:
> > Luca,
> > 
> > The problem with setting the CE facing administrative 
> status to down as a
> > way to tear down the PW is that in case of logical 
> attachments circuits
> > (like VLAN as example) you may do not have one.
> 
> I'm not sure I understand this clearly.
> Are you talking about the case when there are many VCs inside 
> a single PW ?
> that is never the case in the control draft.

Maybe I wasn't clear enough. In PW type EthernetVLAN for example, many PWs
may be associated with a single physical Ethernet interface. If the
interface table (in the ifMib) has no knowledge on each individual VLAN,
there is only one Administrative Status available at the physical port
without per VLAN granularity. In this case tearing an individual PW must be
done using the PW administrative status.
> 
> 
> > Another reason as I stated
> > earlier is that the physical interface administrative 
> status may be used
> > separately from the PW administrative status.
> > 
> one thing that is clear is that if the interface is admined 
> down the PW will 
> not be forwarding.

Agree.

> Two things can happen:

> 
> 1) a PW status TLV is sent out with the PW CE-facing tx and rx faults.
> 
> 2) the PW is torn down, and this is looked at as an 
> configuration event.
> 
> In either case the remote PE should take the same action.
> 
> > An EMS application has a separate admin can be used for 
> tearing the PW. If
> > an implementation want to tie it together to the physical 
> port admin it is
> > OK, but should be left for the implementer decision.
> > 
> 
> I can see that port admin down == tear down is probably not a 
> great idea.

That's my observation too. For tearing down we have the PW administrative
status.

> but why do we need a separate status bit ?
> 

In case of a fault indication, there might be some red alarms, automatic
fault correlation and debugging procedure that would start. With another bit
for administrative operation, no need for these processes.

> What different PE-CE protocol action will the remote PE take 
> in the case of 
> admin down , as opposed to the Pw tx/rx CE-facing fault ?
> 
> 
The same forwarding action, only different level of reporting.

> 
> > If there is an agreement on that, than there is a need in 
> the status to
> > inform about the physical port administrative status.
> > 
> > David
> > 
> I have no problem in allocating the bit , just need some 
> arguments to defend it.
> :-)
> 
> Thanks.
> Luca
> 
> 
> 
> 
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