The MPLS WG Archive

[Kireeti Kompella <kireeti@juniper.net>]

Hi Curtis,

> That would only be the case if the L3PID on the outer tunnel (top) was
> set up as MPLS.  If the L3PID was set up as IPv4, then only tunnels
> containing IPv4 in the payload (other tunnels with a L3PID of IPv4)
> should be placed inside.
> 
> I think this has been quite clear, but if not, we should make it
> clear.  The right place might be the hierarchical draft.  See below.

Philosophically, one could define:
a) L3PID applies only when the stack depth is 1.
b) L3PID applies always.

Neither definition is a priori better.  (a) is (I think) more convenient
(for SPs).  However, not being an SP myself, I will let them speak.

Whatever the decision, some text somewhere should capture this.  I agree,
the hierarchical draft is a good place.

> > Note too for IP VPNs and for BGP-free cores, traceroute will not work
> > (easily) -- intermediate LSRs don't know whom to send the ICMP error
> > to.  Yes, one may be able to hack around this, but it ain't pretty.
> 
> This is solved by sending the ICMP forward through the LSP.  The
> egress should be able to look up the destination in the ICMP packet in
> the correct VPN forwarding table if private address is used.

True.  This is what I meant by "hack around this".  But it does work.

Kireeti.