UDP (User Datagram Protocol) - Computer Science Engineering (CSE) MCQ

Concept:
The User Datagram Protocol (UDP) is a network communication protocol that makes it easier to send and receive messages between computers. It's a replacement for the Transmission Control Protocol (TCP) (TCP). It is sometimes referred to as UDP/IP in a network that uses the Internet Protocol (IP).

Option 1: UDP is an unreliable transport protocol.
True, UDP is an unreliable protocol because it does not provide error correction. To look at it another way, packet delivery is not guaranteed.

Option 2: There is no window mechanism in UDP.
True, UDP is a simple but insecure transport protocol. There is no window mechanism because there is no flow control.

Option 3: There is a robust error control mechanism in UDP.
False, In contrast to TCP, UDP does not require checksum calculation. UDP does not provide any error or flow control. As a result, UDP error reporting depends on IP and ICMP. As a result.

Option 4: The receiver may overflow with incoming messages.
True, UDP is a very simple protocol. It lacks a flow-control mechanism. The receiver may become overburdened with incpming messages. If this service is required, the process using UDP should provide it.
Hence the correct answer is there is a robust error control mechanism in UDP.

TCP (Transmission Control Protocol): The transport layer is responsible for error-free, end-to-end delivery of data from the source host to the destination host. It corresponds to the transport layer of the OSI model.
The functions of the transport layer are:

• It facilitates the communicating hosts to carry on a conversation.
• It provides an interface for the users to the underlying network.
• It can provide for a reliable connection. It can also carry out error checking, flow control, and verification.

Transmission Control Protocol (TCP):

• It is a reliable connection-oriented protocol that transmits data from the source to the destination machine without any error.
• A connection is established between the peer entities prior to transmission.
• At the sending host, TCP divides an incoming byte stream into segments and assigns a separate sequence number to each segment.
• At the receiving host, TCP reorders the segments and sends an acknowledgment to the sender for correct receipt of segments.
• TCP also manages flow control so that a fast sender does not overwhelm a slow receiver.

User Datagram Protocol (UDP):

• It is a message-oriented protocol that provides a simple unreliable, connectionless, unacknowledged service.
• It is suitable for applications that do not require TCP’s sequencing, error control or flow control.
• It is used for transmitting a small amount of data where the speed of delivery is more important than the accuracy of delivery.

Stream Control Transmission Protocol (SCTP): It combines the features of both TCP and UDP. It is message oriented like the UDP, which providing the reliable, connection-oriented service like TCP. It is used for telephony over the Internet.
UPD is used for real time multimedia, DNS and TCP is used for e-mail.

UDP is an unreliable, connectionless transport layer protocol that provides message-based data transmission. TCP is an example of connection-oriented protocols.

De-multiplexing is the delivering of received segments to the correct application layer processes at the recipients end using UDP. Error checking is done through checksum in UDP.

The Network Time Protocol is a clock synchronization network protocol implemented by using UDP port number 123 to send and receive time stamps.

Port numbers from 1025 to 5000 are used as ephemeral port numbers in Windows Operating System. Ephemeral port numbers are short-lived port numbers which can be used for clients in a UDP system where there are temporary clients all the time.

A user datagram is encapsulated in an IP datagram. There is a field in the IP header that defines the total length of the IP packet. There is another field in the IP header that defines the length of the header. So if we subtract the length of the IP header that is encapsulated in the IP packet, we get the length of UDP datagram.

Using Chargen with UDP on port 19, the server sends a UDP datagram containing a random number of characters every time it receives a datagram from the connecting host. The number of characters is between 0 and 512.

As UDP does not provide assurance of delivery of packet, reliability and other services, the overhead taken to provide these services is reduced in UDP’s operation. Thus, UDP provides low overhead, and higher speed.

The fixed size of the UDP packet header is 8 bytes. It contains four two-byte fields: Source port address, Destination port address, Length of packet, and checksum.