Thanks for all, Clients have 1Gb and iperf3 results are 900Mb per client, if multiple client run at same time. I think client and server network is ok. I've figured out something else. On Host setting there is an option for "console and gpu". separated or consolidated. It's made me suspected that the issue might come from this. I've checked my gpu which is onboard lshw -C Display *-display description: VGA compatible controller product: MGA G200eH3 vendor: Matrox Electronics Systems Ltd. physical id: 0.1 bus info: pci@0000:01:00.1 logical name: /dev/fb0 version: 02 width: 32 bits clock: 33MHz capabilities: pm msi pciexpress vga_controller bus_master cap_list rom fb configuration: depth=32 driver=mgag200 latency=0 resolution=1024,768 resources: irq:17 memory:d8000000-d8ffffff memory:d9b98000-d9b9bfff memory:d9000000-d97fffff memory:c0000-dffff Spice uses gpu, RDP uses cpu. So, maybe if i change my primary gpu with some powerful one it can effect spice in a good way What do you think about that?