Hello, I've put a debug line at the beginning of the u32 classifier to print the content of the packets (skb->data) , but: A, http client B, web server, qos with u32 classifier When doing http requests, the u32 classifier on host B isn't called for the packet containing the GET/ request. Then reversing : A, web server B, http client, qos with u32 classifier This time the content returned by A isn't passed to classifier. tc rules are : tc qdisc add dev $DEV handle 1: root cbq bandwidth 56kbit avpkt 1000 mpu 64 tc class add dev $DEV parent 1: classid 1:1 cbq bandwidth 56kbit avpkt 1000 prio 1 rate 56kbit bounded isolated tc filter add dev $DEV parent 1:0 protocol ip prio 1 u32 match ip dst $DEST flowid 1:1 Does anyone knows if this is normal ? (I'm testing under usermode linux). thanks