I think I'm making some progress on my L2TPv3 tunnel project (between two 3640s, one connected via ATM at a remote site). It looks like the tunnel is being established, but then it tries to bring up a session within that tunnel. One side sends an ICRQ to the other. That other side responds by sending a service request to SSS. I'm not certain what SSS is, but I'm not sure we have it. That's where everything stops. Does anyone know anything about this? I notice one side is set to "sss switching" and the other is "idb switching". Could that make a difference?