_______ is used to detect the errors in the header to avoid misdelivery.

Question

Accepted Answer

The correct option is (1):
The mechanism used specifically to detect errors in the header of a network packet, such as an IP datagram or a TCP/UDP segment, is the **Checksum**. The Checksum is an error-detection code calculated by the sender by performing a mathematical summation of the data in the header fields. This result is then placed in a dedicated Checksum field within the header. When the packet arrives at an intermediate router or the final destination host, the receiver recalculates the checksum using the exact same algorithm. If the calculated checksum matches the value stored in the header, the data is assumed to be uncorrupted. If the values do not match, it indicates that one or more bits in the header were accidentally altered during transmission. The device will then discard the corrupted packet to prevent misdelivery, ensuring that the packet is not forwarded to an incorrect address due to header corruption, which is its primary function in preventing misdelivery.

The incorrect option is (2):
**Fault** is a general term in computing that refers to the underlying cause of a system failure, such as a hardware malfunction or a programming bug. A fault is the *origin* of a problem that might lead to an error in a packet header, but it is not a mechanism or a calculated field used for active error detection. In the context of the question, a fault would *cause* the error, but the Checksum is the tool that *detects* it.

The incorrect option is (3):
The term **Error** refers to the actual change or corruption of data that has occurred during transmission, which is the *result* of a fault or noise on the transmission medium. For example, a single bit flip in the destination address is an error. The Checksum is the mechanism used to *find* the error, but the error itself is not the method of detection. The question asks for the tool or technique used for detection, not the problem that is being detected.

The incorrect option is (4):
**Padding** is a technique used to add 'filler' bits or bytes to a data block, typically to make the block length conform to a required minimum size or a specific multiple of bytes (e.g., to align with hardware word boundaries). Its purpose is purely structural and related to data alignment or protocol conformity. Padding data does not contain any calculated value or control information designed to verify the integrity of the header, meaning it has no role in detecting transmission errors.