The MPLS WG Archive

[Shahram Davari <Shahram_Davari@pmc-sierra.com>]

Curtis,

> -----Original Message-----
> From: Curtis Villamizar [mailto:curtis@workhorse.fictitious.org]
> Sent: Tuesday, December 18, 2001 11:14 AM
> To: Shahram Davari
> Cc: 'curtis@fictitious.org'; David Allan; Cuevas, Enrique G, ALCTA;
> dave.mcdysan@wcom.com; giles@packetexchange.net; Don Fedyk;
> Ben.Mack-Crane@tellabs.com; mpls@UU.NET; neil.2.harrison@bt.com
> Subject: Re: MPLSOAM BOF meeting draft minutes 
> 
> 
> 
> In message 
> <4B6D09F3B826D411A67300D0B706EFDE84A481@nt-exch-yow.pmc-sierra.bc.ca
> >, Shahram Davari writes:
> > Curtis,
> >  
> > > ICMP is sent to detect failure.  UDP based LSP Ping is 
> sent after an
> > > failure is detected using ICMP.  Why we need the latter 
> is somewhat of
> > > a mystery to me, apparently to either distinguish a data 
> plane from
> > > control plane failure or to to circumvent anti-ICMP religion.
> > > 
> > 
> > May be that is why you advocate that LSP-Ping could be 
> easily extended to oth
> > er types
> > of MPLS control-planes. 
> > 
> > The reason that you need LSP-ping after the ICMP-ping 
> failure is that, the 
> > ICMP failure could have been due to reverse IP (hop-by-hop) 
> path failure. So
> > to determine whether the LSP is down or the reverse IP 
> path, you need a disjo
> > int
> > reverse path => RSVP reverse path :)
> 
> Both reverse path for ICMP and LSP are IP paths.  If they went down
> control traffic wouldn't flow so they can be assumed to be up.
> 

Both are IP paths, but the ICMP response path is hop-by-hop IP, while
the RESV path is based on ERO (of the forward LSP). So LSP Ping requires
a non hop-by-hop path, and that is why it is using the RESV message. 

> > -Shahram
> 
> Nice try. 

Let's try again:)

-Shahram
 
> 
> Curtis
>