if your using our voxility ddos protection you may consider apply this setting to your linux server to get stable connection .

 

whitelisted in your firewall:

ptables -I INPUT -s 93.115.83.64/26 -j ACCEPT
iptables -I INPUT -s 5.254.83.0/26 -j ACCEPT
iptables -I INPUT -s 93.115.90.64/26 -j ACCEPT
iptables -I INPUT -s 5.254.107.0/26 -j ACCEPT
iptables -I INPUT -s 5.254.108.64/26 -j ACCEPT
iptables -I INPUT -s 5.254.110.0/26 -j ACCEPT
iptables -I INPUT -s 5.254.88.0/26 -j ACCEPT
iptables -I INPUT -s 5.254.115.128/26 -j ACCEPT
iptables -I INPUT -s 5.254.70.64/26 -j ACCEPT
iptables -I INPUT -s 5.254.30.192/26 -j ACCEPT

 

 

edit you sysctl.conf:

net.ipv4.ip_local_port_range=32768 61001
net.ipv4.tcp_dsack=0
net.ipv4.tcp_ecn=0
net.ipv4.tcp_fack=0
net.ipv4.tcp_fin_timeout=1
net.ipv4.tcp_keepalive_intvl=10
net.ipv4.tcp_keepalive_probes=3
net.ipv4.tcp_keepalive_time=30
net.ipv4.tcp_low_latency=1
net.ipv4.tcp_max_orphans=524288
net.ipv4.tcp_max_syn_backlog=1024
net.ipv4.tcp_no_metrics_save=1
net.ipv4.tcp_retries2=10
net.ipv4.tcp_sack=1
net.ipv4.tcp_slow_start_after_idle=0
net.ipv4.tcp_synack_retries=3
net.ipv4.tcp_syncookies=2
net.ipv4.tcp_timestamps=1
net.ipv4.tcp_tw_reuse=1
net.ipv4.tcp_window_scaling=1

 

 

restart server ! and get more stable connection now !