[e2e] how to use token bucket to reduce rate

[changxl]

Hi,
Could someone help me? Thanks in advance.

The problem is:
node s1 sends packets to node d1 , but the arrival rate at d1 shoule not 
exceed a certain value. When this occurs, d1 should send source quench message 
to s1. HOw to implement this? And when s1 receives this quench message , how 
does s1 use token bucket to reduce rate?

Could someone tell me which .cc file should be modified?

Thanks,
cxl