what are three responsibilities of the transport layer? (choose three.)

2025

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29-03-2025

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The transport layer is a crucial part of the TCP/IP model, sitting between the network layer and the application layer. It's responsible for ensuring reliable and efficient data delivery between applications running on different hosts. While it has many functions, three key responsibilities stand out: segmentation and reassembly, connection management, and flow control. Let's delve into each one.

1. Segmentation and Reassembly

One of the transport layer's primary roles is managing the size and format of data transmitted across the network. Applications often generate data in chunks of varying sizes. However, the underlying network infrastructure may have limitations on the maximum size of a data packet (the Maximum Transmission Unit or MTU).

The transport layer addresses this by segmenting large application data into smaller packets suitable for transmission. These smaller packets are then reassembled into the original data stream at the receiving end. This process ensures data integrity and efficient network utilization. Think of it like breaking down a large box of books into smaller, manageable parcels for shipping, then reassembling them at the destination.

Why Segmentation Matters

• Network Efficiency: Smaller packets are less likely to be lost or corrupted during transmission.
• Error Handling: If a segment is lost, only that segment needs to be retransmitted, not the entire data stream.
• Multiple Network Technologies: Adapts to varying MTUs of different network technologies.

2. Connection Management

The transport layer provides mechanisms for establishing, managing, and terminating connections between communicating applications. This is particularly important for ensuring reliable data delivery. Two main approaches exist: connection-oriented and connectionless.

Connection-oriented protocols, like TCP (Transmission Control Protocol), establish a dedicated connection before data transmission begins. This involves a three-way handshake to ensure both ends are ready. The connection remains active until explicitly closed, guaranteeing ordered and reliable data delivery.

Connectionless protocols, like UDP (User Datagram Protocol), don't require a connection setup. Data packets are transmitted independently, without any guarantee of delivery or order. While faster, connectionless protocols are less reliable and suitable for applications where occasional data loss is acceptable (e.g., streaming).

Choosing the Right Connection Type

• Reliability: TCP prioritizes reliability, guaranteeing delivery and order.
• Speed: UDP sacrifices reliability for speed, making it ideal for real-time applications.
• Overhead: TCP adds overhead for connection management, impacting speed.

3. Flow Control

Flow control ensures that data transmission doesn't overwhelm the receiving end. A fast sender could flood a slower receiver with data, leading to packet loss and network congestion. The transport layer implements mechanisms to regulate the rate of data transmission.

This often involves a "sliding window" approach. The sender maintains a window of data it can transmit without waiting for acknowledgment. The receiver controls the size of this window based on its processing capacity and available buffer space. When the receiver's buffer is full, it shrinks the window, slowing down the sender. When space becomes available, it increases the window, allowing the sender to speed up again.

Importance of Flow Control

• Prevent Overloading: Prevents the receiver from being overwhelmed by incoming data.
• Efficient Resource Utilization: Optimizes network bandwidth and resources.
• Reliable Data Transmission: Reduces packet loss due to buffer overflows.

Conclusion

The transport layer plays a vital role in ensuring reliable and efficient data communication. Its responsibilities, including segmentation and reassembly, connection management, and flow control, are essential for the smooth operation of network applications. Understanding these functions is key to comprehending the complexities and capabilities of modern network architectures. The choice between connection-oriented and connectionless approaches depends heavily on the application's specific requirements regarding reliability and speed.