Controlling bitcoind connection bandwidth The bitcoin github repo has a  bash script given to control the flow of outbound traffic by using the bash script given  on : https://github.com/bitcoin/bitcoin/blob/master/contrib/qos/tc.sh

I am running two bitcoind instances on a local machine with different ports: 18441 and 18442, how do I make use of this script or tweak it, to control the connection bandwidth between the two bitcoind instances ?
If you're running two bitcoind instances on one machine, depending on the use case, you may instead be better off by connecting one to the other only, and not make it talk to the network. This will reduce the total bandwidth used significantly, as every block and transaction will only be fetched once.

Run the first one normally, and use -connect=127.0.0.1:18442 on the second.