dropper performance

Experiments of the packet dropper module( by Glen )

Test Script file for the test

Network infrastructure diagram,

Packet Flow: Madrid:eth1==>Dublin:eth2==>Dublin:eth1==>Prague:eth2

Packet dropper is running on the Static Router (Dublin).

Packet Dropper Module code Makefile

TCP connection. Request Size is optimal size 1448Bytes.

Kernel file modified: /usr/src/linux/net/core/dev.c /usr/src/linux/net/netsyms.c

Optimal Request Size 1448 (TCP blast test) iteration times=100000
drop rate	Time elapse (sec)												var/avg	Throughput
drop rate	1st	2nd	3rd	4th	5th	6th	7th	8th	9th	10th	AVG	Var	var/avg	Throughput
0	12.33	12.34	12.41	12.37	12.35	12.44	12.34	12.40	12.35	12.38	12.371	0.0292	0%	12335300.30
0.1%	27.88	27.87	27.87	27.92	27.92	27.87	27.87	27.90	27.90	27.85	27.885	0.02	0%	5472476.24
0.5%	28.41	28.43	28.63	28.44	28.30	28.80	28.79	28.48	28.60	28.76	28.564	0.152	1%	5342389.02
1%	30.43	30.40	31.38	30.47	31.25	31.05	30.21	31.32	31.27	31.46	30.924	0.4372	1%	4934678.57
2%	37.09	38.62	41.73	38.07	38.59	36.74	39.40	38.67	39.88	40.32	38.911	1.1372	3%	3921770.19
5%	86.16	86.17	92.66	88.77	89.84	90.15	87.78	87.51	87.00	86.59	88.263	1.6736	2%	1728923.78
10%	293.59	288.31	301.46	283.20	289.61	288.89	292.89	306.97	291.82	267.83	290.457	6.889	2%	525378.97
20%	1579.44	1612.92	1835.97	1858.58	1909.68	1709.72	1799.82	1777.15	1823.33	1737.23	1764.384	83.6452	5%	86489.11

Note: The data in 0% dropping rate is the case when Packet_dropper module is not installed

A PS version of the chart is available here

The throughput is calculated in this way:

Throughput = 1526 * 100000/(Average elapse time )

Although the request size is 1448. There are overheads (TCP header/ IP header/ Ethernet Wrapper). The actual data sent is 1526 bytes each time

The Original experiment data: NoDrop, drop0.1, drope0.5, drop1, drop2, drop5, drop10, drop20

Explanation of the chart:

The throughput drops significantly even when the dropping rate is very low ( 0.1% ). This might help to explain the TCP exponential back off: When the sender finds packet is lost, it reduces the sending speed in half.