What are the two main types of communication used by the Transport Layer?

• A. Connection-oriented (TCP) and connectionless (UDP)
• B. Datagram and streaming
• C. Synchronous and asynchronous
• D. Client-server and peer-to-peer

Answer: (A)

The main concept here is the mode of communication the Transport Layer provides, split by whether a session is established and maintained. One mode is connection-oriented: a session is set up between endpoints (a handshake occurs), the endpoints keep state, and the protocol guarantees reliable, ordered delivery with flow and congestion control. The other mode is connectionless: no prior connection or persistent session is established; packets are sent as independent datagrams with minimal overhead and no guarantees of delivery or order, leaving reliability to the application if needed. This distinction is embodied by TCP (connection-oriented) and UDP (connectionless).

So this question highlights the two fundamental transport-layer communication styles: reliable, stateful, connection-managed versus simple, stateless, best-effort delivery. The other options describe different aspects that aren’t the primary division at the transport layer: datagram vs streaming concerns data packaging or usage, not the fundamental connection model; synchronous vs asynchronous refers to timing coordination rather than the transport’s connection semantics; and client-server vs peer-to-peer describes network architecture, not the transport-layer communication service.