Subject: RE: Active/Standby Status Bit

From: "Ali Sajassi \(sajassi\)" <[email-masked]>
Date: Tue, 7 Nov 2006 19:26:39 -0800

________________________________

	From: Sasha Vainshtein [mailto:[email-masked]] 
	Sent: Tuesday, November 07, 2006 11:14 AM
	To: AISSAOUI Mustapha; Ali Sajassi (sajassi)
	Cc: [email-masked]
	Subject: RE: Active/Standby Status Bit

	Mustapha, Ali and all,
	After the yesterday presentation I have been under impression
that, in the case of a dual-homed MTU-s, the status bit would only
sirnal to the "standby" PE-r not to send its BUM traffic over the
standby PW. 
	 
	Ali's text below seems to suggest that PE-r should not send ANY
traffic over the "standby" PW. 
	 
	Yes, PE-rs should not send any traffic because known-unicast
would never get sent over standby PW from either far-end MTU-s or local
MTU-s. However, based on earlier emails, it seems like we need to have a
new bit anyway because of OAM indication issue to AC.
	 
	-Ali
	 
	Do I miss something? 
	Or is it a real difference in interpretation (between, say,
draft-muley and VPLS dual-homing)?
	 
	Regards,
	                Sasha

________________________________

	From: AISSAOUI Mustapha [mailto:[email-masked]]
	Sent: Tue 11/7/2006 06:57
	To: Ali Sajassi (sajassi)
	Cc: [email-masked]
	Subject: RE: Active/Standby Status Bit

	Ali,
	See below.
	
	Mustapha.
	
	> -----Original Message-----
	> From: Ali Sajassi (sajassi) [mailto:[email-masked]]
	> Sent: Monday, November 06, 2006 10:05 PM
	> To: AISSAOUI Mustapha; Luca Martini (lmartini)
	> Cc: [email-masked]
	> Subject: RE: Active/Standby Status Bit
	>
	> 
	>
	> > -----Original Message-----
	> > From: AISSAOUI Mustapha
[mailto:[email-masked]]
	> > Sent: Monday, November 06, 2006 5:04 PM
	> > To: Luca Martini (lmartini)
	> > Cc: [email-masked]
	> > Subject: Active/Standby Status Bit
	> >
	> > Luca,
	> > Here is the description of the "PW not forwarding" bit as
per RFC
	> > 4447:
	> >
	> > "The presence of the lowest bit (PW Not Forwarding) acts
only as a
	> > generic failure indication when there is a link-down event
	> for which
	> > none of the other bits apply."
	> >
	> > So, we still need a bit to indicate a failure which is not
	> explicilty
	> > indicated by the AC and PSN failure bits. A good example of
	> using this
	> > bit is when an LSP switches its path and if the new path
	> MTU does not
	> > match anymore that signaled in the PW FEC, this bit is used
	> to signal
	> > the remote PE.
	> > There may be other types of failures which could use this
bit.
	> >
	> With respect to u-PE dual homing applications to two
	> different n-PE devices, it is still not clear to me why we
	> cannot use "PW forwarding"
	> bit (since the MTU for the standby PW is already signaled
	> between u-PE & standby n-PE). If the problem is its
	> definition as defined in RFC 4447, then we can generalize its
	> definition a bit more. However, if there is a more
	> fundamental problem, then lets elaborate on what that is.
	
	MA> The MTU for tunnel LSP can change if the LSP path for the
primay PW
	or the secondary PW changes. If the new MTU value is lower than
the one
	signaled in the PW FEC iterface parameter field, an alarm should
be
	raised since the PE will drop packets on that PW. So, this is a
fault
	condition which we currently  signal using the "PW not
forwarding bit".
	
	When the PW is in standby state, there is no fault or alarms
which are
	generated. It just an indication to the remote PE to preferably
not send
	traffic over that PW.

	> -Ali
	>
	> > I can only conclude that we need a separate bit for the
	> > "Active/Standby"
	> > status.
	> >
	> > Mustapha.
	> >
	>