Hi, all I read the code about HTB. Function htb_class_mode judge the "mode" of a class, when " cl->ctokens + *diff < 0", it means that the class's rate exceeds the Ceil-rate. Why? And, can somebody tell me that How Can I compute the rate of a class? Is there a formula which can get the accurate rate at any time? Thanks ! Best Regards Lawrence Lee Linux/IA, Software, S3 Tech. Tel:(021)53560056-8056 Mail: lawrencelee@xxxxxxxxxxxxxx