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Computer Networks · Question Set
Transport Layer & Congestion Control interview questions for placements and exams.
Questions
13
Included in this set
Subject
Computer Networks
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Difficulty
Mixed
Level of this set
Go through each question and its explanation. Use this set as a focused practice pack for Computer Networks.
TCP establishes a connection before data transfer and ensures ordered, reliable delivery. UDP, by contrast, sends datagrams without connection setup, offering lower latency but no guarantee of delivery. Choosing between them depends on the application’s needs.
For complete preparation, combine this set with full subject-wise practice for Computer Networks. You can also explore other subjects and sets from the links below.
The Sequence Number identifies the first byte in the segment’s data, enabling the receiver to reorder out-of-sequence packets correctly. Together with the acknowledgment number, it maintains reliable ordered delivery in TCP.
TCP uses a sliding-window mechanism to manage the amount of data that can be sent before receiving an acknowledgment. The receiver advertises a window size representing how much data it can accept. The sender adjusts its sending rate accordingly, preventing buffer overflow and ensuring efficient use of resources. This dynamic adjustment makes TCP adaptive to varying network conditions.
In the slow-start phase TCP begins with a small congestion window and doubles it each round-trip time as acknowledgments are received. This rapid increase probes available bandwidth until a threshold is reached, after which growth becomes linear.
UDP sends data directly without establishing a connection. This reduces delay and overhead, making it ideal for time-sensitive applications like video streaming or gaming. However, reliability and ordering are left to the application.
Port numbers identify specific processes or applications within a host. When data reaches a device, the port number determines which application should handle it. For example, HTTP uses port 80 and HTTPS uses 443. Ports allow multiple network services to run simultaneously on the same machine without conflict.
The Transport Layer ensures reliable or best-effort end-to-end delivery between processes on different hosts. It handles segmentation, acknowledgment, flow control, and error recovery, enabling application-level communication over the network.
TCP retransmits segments when it suspects packet loss—either when a timeout occurs or when three duplicate ACKs are received. The fast retransmit algorithm helps recover quickly from isolated losses without waiting for timeouts.
TCP uses a four-step termination process. One side sends a FIN to signal it has finished sending. The receiver acknowledges with ACK and may send its own FIN when done. The first side replies with a final ACK. This orderly teardown ensures that all data is delivered and resources are released gracefully. Interviews often ask candidates to contrast this with the three-way handshake.
In TCP socket programming, a client initiates a connection using connect(), while the server waits for requests using accept(). Once connected, data transfer uses send() and recv(). Understanding this flow helps you answer coding-based interview questions.
Server: socket(), bind(), listen(), accept() Client: socket(), connect()
The TCP three-way handshake establishes a reliable connection between client and server. Step 1: The client sends a SYN segment to request connection. Step 2: The server replies with SYN-ACK, acknowledging the request and sending its own SYN. Step 3: The client responds with ACK to confirm. After these three steps both sides are synchronized and can start data transfer. This process ensures both sides are ready and sequence numbers are initialized.
Congestion control prevents excessive load on the network that leads to packet loss and reduced throughput. TCP uses algorithms such as slow-start, congestion avoidance, fast retransmit, and fast recovery to adjust the sending rate based on perceived congestion.
TCP Tahoe introduced slow-start, congestion avoidance, and fast retransmit. When loss is detected, Tahoe resets the congestion window to one segment, causing a full slow-start. TCP Reno added fast recovery, allowing quicker recovery after a single packet loss. TCP New Reno further improved performance by handling multiple losses within one window without waiting for a timeout. Understanding these variants demonstrates knowledge of how TCP evolved to manage congestion efficiently across diverse networks.