The MPLS WG Archive

["LIAN Franklin FTLD/IAP" <franklin.lian@francetelecom.com>]

wu min wrote:
> 
> The last few lines of the RFC3031 snippet from my previous message reads,
> "....In this situation, packet P can be label Switched until it reaches R2,
> but since R2 has performed route aggregation, it must execute the best match
> algorithm to find P's FEC."
> 
> It indicated that the best match algorithm must be executed to find the next
> appropriate FEC to be used for further label switching. In my opinion,
> surely this does not stop it from label switching further, right?
> 

Sure, if there is another LSP built for the more granular FEC, but you
don't know if there is one or not.

> > > 2. Suppose the LSP is being used as a tunnel that ends after R2 and if
> >the
> > > answer for my question (1) is true, then stripping the top label will
> >never
> > > reveal the IP header yet since there will still be 1 or more labels. Is
> >this
> > > situation valid? If so, can R2 still manage to terminate the LSP and
> >perform
> > > best match algorithm? If yes, then how?
> >
> >I don't think you can build an LSP beyond R2 in this case, in another
> >word, I don't know how you can have a tunnel that ends after R2.
> 
> What I meant is, take for example an LSR with address 10.2.153.178 is a
> remote peer and the LSP in the example is the hop-by-hop routed tunnel used
> for this peering. Obviously here the LSR is after the LSR2.

With LDP, you can try to build a tunnel to 10.2.153.178, but if the
tunnel LSP is broken in the middle, you won't know.  If you run MPLS
VPN over the broken tunnel, you blackhole the traffic.  I think you
just gave one example why it is necessary to have /32 tunnel 
termination point for MPLS VPN with LDP.

> 
> _________________________________________________________________
> Send and receive Hotmail on your mobile device: http://mobile.msn.com