diff --git a/Optimizing-Shadowsocks.md b/Optimizing-Shadowsocks.md
index b525c17..c3a7873 100644
--- a/Optimizing-Shadowsocks.md
+++ b/Optimizing-Shadowsocks.md
@@ -61,4 +61,15 @@ reduce the size of rmem and wmem.
 
 Before & after:
 
-![cc](https://cloud.githubusercontent.com/assets/1073082/3296349/10c34b04-f5d9-11e3-95fc-e38f5299c274.jpg)
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+![cc](https://cloud.githubusercontent.com/assets/1073082/3296349/10c34b04-f5d9-11e3-95fc-e38f5299c274.jpg)
+
+
+**NOTICE**
+
+Hybla may not be suitable for low-latency network. cubic is probably a better choice for you.
+
+you You must select `net.ipv4.tcp_congestion_control = hybla` or `net.ipv4.tcp_congestion_control = cubic` based on test.
+
+Eg.
+
+![cubic](https://raw.githubusercontent.com/mengskysama/wiki/master/sad.png)
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