Packet Drop
As we are conducting tests on real equipment and not on simulator, it it often difficult to perform tests under different network conditions. We could use something like dummynet to similute packet loss and delay, however, we would not be able to achieve the capacities nor the latencies required for our studies.
As such, in order to simulate a wide spread of network loss rates (link loss rate), we have implemented a patch against a 2.4.20 linux kernel to automatically and periodocially drop incoming tcp packets at a predefined and changeable rate.
Usage
The rate in which the packets are selectively dropped is controlled in a sysctl variable called net.ipv4.tcp_pktdrop_rate. It will automatically ignore values less than 2.
It is basically a loop counter that counts evey packet coming in and it will drop the packet that equals the sysctl net.ipv4.tcp_pktdrop_rate value by marking it with a checksum error. You should see these as InErr packets in the kernel SNMP.
Download
| Description | |
| Patch against linux 2.4.20 | Linux patch against 2.4.20. Includes web100-2.2.1. [1.0] |
| Patch for DataTAG 2.4.20 'dtg4' | As above but also includes SCSI and Syskonnect update drivers. [1.0] |
Results
MB-NG
| Description | |
| VanillaTCP | Performance is sound with good line rates achieved due to low delays. DRS, Web100tune and comparision |
| HSTCP | DRS, Web100tune and comparision |
| ScalableTCP | DRS, Web100tune and comparision |
| Comparision of all Stacks | DRS and Web100tune |
DataTAG
| Description | |
| VanillaTCP | DRS, Web100tune and comparision |
| HSTCP | DRS, Web100tune and comparision |
| ScalableTCP | DRS, Web100tune and comparision |
| Comparision of all Stacks | DRS and Web100tune |
| Tue, 5 August, 2003 22:11 |   |
Room D14, High Energy Particle Physics, Dept. of Physics & Astronomy, UCL, Gower St, London, WC1E 6BT
