Slavica Tomovic wrote:
Hi to all, I am using CentOS 6.4 and have problems when I want to limit bandwidth of TCP flow to some value smaller than 15 Mbit/s. Namely, I used iperf to generate TCP traffic and limited bandwidth (with tc command) for that flow on 6 Mbit/s. I got approximately 6 Mbit/s in average but iperf, which I adjusted to report me statistics every second, showed that in one second flow got 10 Mbit/s or more and than for few consecutive seconds 0 Mbit/s. With UDP traffic everything works fine. I expected that TCP bandwidth will fluctuate because of congestion mechanism but not like this. When I reserve more than 15 Mbit/s situation is pretty much OK. Also I had similar problem when I tried to split link bandwidth (which I had throttled previously on 10 Mbit/s with tc) between two TCP flows. On the other side, TCPvsUDP and UDPvsUDP slicing works fine. I had updated kernel version to 2.6.32-431 recently. I don't know did this cause a problem because I didn't use tc htb mechanism in the older version. Do you have any idea why is this happening and how I can fix it? These are commands I had used to create htb classes: tc class add dev eth0 parent 1: classid 1:1 htb rate 10000kbps ceil 10000kbps tc class add dev eth0 parent 1:1 classid 1:10 htb rate 4000kbps ceil 4000kbps tc class add dev eth0 parent 1:1 classid 1:11 htb rate 6000kbps ceil 6000kbps
kbps means k bytes/sec, use kbit or mbit If you don't specify child qdiscs for htb it will use pfifo with the txqlen on the device as the limit which may be a bit long on eth (1000) or on ppp too short (3). -- To unsubscribe from this list: send the line "unsubscribe lartc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
