Hi Nanog, Scenario: Transits -----(router A)Backbone(router B)----- Customers We applied Cisco CAR at the edge routers (B) in the Backbone to rate limit inbound and outbound traffics to/from Customers. If transmission rate is higher than the rate limit threshold, IP packets are being dropped by router B. How do we prevent the excess IP packets to consume the transit links and the Backbone? Here is my understanding: -For TCP traffics (HTTP, FTP), TCP senders will stop sending packets when the TCP windows threshold is reached. -For UDP based audio/video trafffics, if the applications use RTSP and H.323, RTCP/H.245 will signal the sender to slowdown the transmission if the receiver lost packets. Did I miss anything? How about UDP traffics that are not using RTSP/H.323? Thanks. Suan "Ken" Yeo Network Engineer Aurum Technology ken.yeo@aurumtechnology.com