xenml@matthiasjansen.de
2006-Jun-06 14:56 UTC
[Xen-users] XEN as virtual wireless enviroment
Dear all, We want do develop a virtual wireless enviroment emulator at the university of Düsseldorf (Germany) to test some new wireless protocols as a substitute for the not well performing TCP. The main problem is that the currently available wireless hardware has implemented many protocols of the IEEE 802.11(a,b,g...) family hardcoded in their hardware or in non opensource firmware. But these protocols interfere with our protocols so we can''t use any real hardware to test the protocols in the wild. At this point there comes a virtual network to mind which emulates wireless behaviour like packetloss and the most important colition. We already got a simple emulator from the university of Marburg (Germany) which is based on Xen 2.0. This emulator uses a modified version of the netshaper virtual network device and adds some functionality so set the packet loss rate and some the bandwith limit. But this emulator doesn''t support collition which we need the most because the new protocol should avoid packet collition. So our first thought was to change the interface of the netshaper device to also inform about collition. At first we started some speed tests to see how fast we can inform a Xen node that there was a (virtual) collition. For that we implemented a simple UPD sender and receiver which sends UDP packets of a given size and waits for the return and gives out the time. Thats where I come to my question (sorry for the long introduction) to you: The mean time the packet took to return was 3 milliseconds on a Pentium Mobile with 1,6 Ghz and 1 GB RAM running 2 instances of Xen. (OK, I forgott to mention that the Xen system was running in VMware 5.5) What puzzled me most was the fact that the CPU load was 100%. So my question to you: Do you think that the VMware caused the performance problems? When not, does Xen 3 perform better with network connections? And finally: We would need a performance gain about 100 times, so about 0,03 milliseconds to return the packet from one xen node to the other and back. The bandwith isn''t important, about 1Mbit would be fairly enough. Do you think about any way of getting such good response times on a normal hardware (1 CPU, Pentium 4 with about 2,5 - 3 Ghz) when using about 10 Xen nodes? Thanks alot in advance, Greetings from Germany, Matthias Jansen _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users