The size of a TCP segment header ranges between 20 and 60 bytes.

Explanation:

TCP Protocol:
TCP (Transmission Control Protocol) is a reliable and connection-oriented protocol used for data transmission in computer networks. It provides a reliable stream of data transfer by establishing a connection between the sender and the receiver.

TCP Segment Header:
In TCP, data is transmitted in segments. Each TCP segment consists of a header and the data being transmitted. The header contains control information necessary for the proper delivery and sequencing of the data.

Size of TCP Segment Header:
The size of the TCP segment header is variable and can range from 20 to 60 bytes. The actual size depends on various factors such as the presence of optional fields, such as TCP options, and the size of the data being transmitted.

Factors affecting the size of TCP segment header:
1. Minimum Size: The minimum size of the TCP segment header is 20 bytes, which includes the mandatory fields such as source and destination port numbers, sequence number, acknowledgment number, control flags, and checksum.

2. Optional Fields: TCP allows for the inclusion of optional fields, known as TCP options, in the segment header. These options can include additional control information or parameters required for specific purposes. The presence of TCP options increases the size of the segment header.

3. Data Size: The size of the data being transmitted in the TCP segment can also affect the size of the segment header. If the data size is small, the segment header will be larger in proportion to the data. Conversely, if the data size is large, the segment header will be relatively smaller.

Conclusion:
In conclusion, the size of the TCP segment header can range from 20 to 60 bytes, depending on the presence of optional fields (TCP options) and the size of the data being transmitted. The minimum size of the segment header is 20 bytes, while the maximum size is 60 bytes.