The term transaction refers to the request sent by a client to a server along with the server's reply.
T/TCP can be considered as a superset of the TCP protocol. The reason for this is that T/TCP is designed to work with existing TCP machines seamlessly. If a TCP host tries to connect to a T/TCP host, the T/TCP host will respond with the original TCP 3-Way Handshake. What follows is a brief description of T/TCP and how it differs to the current TCP standard in operation. There are a number of smaller differences as well, but we will only deal with the main ones here.