There seems to be a generic issue in v3.7 on how much tx traffic out of the PVM can be handled. I actually can see something similar with Xen 4.2 with dom0 running a Quantal kernel (I know it is a daring combination). But I think that points either to net in general or to the netfront driver. I would believe we would have noticed a generic net problem by now, so I would check on netfront first.
There seems to be a generic issue in v3.7 on how much tx traffic out of the PVM can be handled. I actually can see something similar with Xen 4.2 with dom0 running a Quantal kernel (I know it is a daring combination). But I think that points either to net in general or to the netfront driver. I would believe we would have noticed a generic net problem by now, so I would check on netfront first.