GATE Overflow Test Series | Computer Networks | Test 1 | Question: 8

Question

When a UDP segment arrives at a host, in order to direct the segment to the appropriate socket, the operating system's network stack uses which of the following fields? (Mark all the appropriate choices)

• A. the source IP address
• B. the destination IP address
• C. the source port number
• D. the destination port number

Comments

@gatecse What if same thing for TCP host?

Answer 1

UDP is connectionless and hence uses only the destination address (IP, port).

Comments

The combination of the destination port and the IP address in the IP header is used to route the UDP segment to the appropriate application or socket on the receiving host. The operating system keeps a table of active sockets and their associated port numbers, allowing it to demultiplex incoming UDP segments to the correct destination.

The operating system maintains a table of active connections (the connection's 4-tuple, which includes source IP, source port, destination IP, and destination port) and uses this information to demultiplex incoming TCP segments to the correct socket, allowing the host to handle multiple TCP connections simultaneously.