Function NS_LOG - NS3(Network Simulator): What does the operator "<<" mean in practice?

Question

I am working with the ns3 program, and trying to understand the code that I have at hand, I came across this line, and I would like to know what this sequence of "<" means. (I don’t mean the variables, but the command "<<")

I read about it and I found this: shift to the left and add zeros at the right end, but this is true between 2 values. I don’t know what it means so chained as shown in the function below.

NS_LOG_FUNCTION (this << tcb << packetsAcked << rtt);

Answer 1

This is a left bit shift operator: https://msdn.microsoft.com/pt-br/library/336xbhcz.aspx