[Fedora-xen] Poor Network Performance between dom-0 and dom-u

Hi, i have problems concerning the network performance between dom-0 and a dom-u host. Messurement using iperf show [ 4] 1.0- 2.0 sec 7.85 MBytes 65.8 Mbits/sec Network performance between dom-0 and an external maschine shows gigabit speed. [ 5] 0.0- 1.0 sec 112 MBytes 938 Mbits/sec i am using Fedora core 6 on the dom-0 host and redhat 4.4 on the dom-u guest. Dom-u is fully virtualized. (Dual Xeon 5150 2.66GHz.) Any hints that could help to improve the performance are greatly appreciated. -- Harald