I was stimulating a program in ns2. The program consist of 4 nodes arranged as 1,2,3,4,5. Each of these nodes are connected with a 2 Mbps link, and I was sending data from node 1 to 5 through intermediate nodes 2,3 and 4. The connection used was TCP connection and was sending FTP data over it. What I'm confused is even if I set data rate to 2 Mbps and 8 Mbps im getting the same throughput and delay. shouldn't the throughput reduce due to congestion as im trying to sending data at 8 Mbps speed through 2 Mbps link?