Transport layer protocol

For peer to peer communication between controllers to achieve real time control, some vendors use UDP protocol instead of TCP protocol at the transport layer. Vendors like siemens use UDP instead of TCP. What are the advantages of UDP. What are the limitations of TCP protocol for real time control.

I would suggest you check here

http://ourworld.cs.com/rahulsebos/

for networks and follow some of the links so that you can complete your homework. If you show what you have done through good research and then come back with some more specific questions I am sure any of us will help if we can.

UDP typically allows for a one to many communications configuration, while TCP is used for one to one relationships only. Reason being that the TCP protocol facilitates some "handshaking" if you will, offering the ack and nack. I liken it to an acknowledgement that the packet sent by one end was in fact received by the other end. There are no guarantees using UDP. Depending upon the amount of traffic on that Ethernet segment, you may not notice any additional delay using TCP.