TCP vs UDP: Understanding the Difference

What is TCP?

The Transmission Control Protocol or TCP is a communication protocol that describes how to build and maintain a network communication by which application programs exchange data. 

TCP originated in the initial network implementation through which it complemented the Internet Protocol (IP). Therefore, the duo is ordinarily referred to as TCP/IP. Internet Protocol (IP)is the element that determines how computers send data packets to each other. In this day and age, TCP and IP are the necessary rules defining the Internet. 

How TCP works?

Unlike UDP, TCP is a connection-oriented protocol, meaning it ensures the package’s safety and ensures it will reach the target destination device. This type of protocol is built with the help of a three-way handshake—a three-way handshake is a negotiation process between two parties using data transfer. Once the link is established, the transfer starts, and when the transmission process is terminated, the connection is ended by the closing of a designated virtual circuit.

Features of TCP

  • TCP is a reliable protocol.
  • Reliable but slower than UDP.
  • Operates in client/server point-to-point mode.
  • Provides error control and recovery algorithms.
  • Connection-oriented protocol. 
  • May delay transactions when the network is overcrowded.
  • Acknowledgment when delivered.
  • Has a bigger header than UDP.
  • Suited for high-reliability projects.

Advantages of TCP

  • The initiator asks the acceptor before pairing.
  • It operates independently irrespective of the operating system.
  • It supports many routing protocols.
  • It enables internetworking among different organizations.
  • Highly scalable client-server architecture.
  • Supports several routing protocols.
  • It can be used to build a connection between two computers.
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Disadvantages of TCP

  •  Not fitting to describe new technologies in new networks.
  • It does not differentiate between the data linkage and the physical layers, which have very different functionalities. 
  •  It is not optimized enough for small network systems like LAN (local area network) and PAN (personal area network).
  • Protocol replacement is difficult.
  • Can’t use for broadcast or multicast transmission

Real-time applications of TCP

What is UDP?

The User Datagram Protocol, or UDP, is a communication protocol utilized across the Internet, especially during time-sensitive transmissions such as video playback and DNS lookups. 

UDP speeds up communications by not formally establishing a connection before the data transfer. This datagram allows data movement very quickly. Still, it can also cause data packets/ data units to get lost in the transition to creating exploitation opportunities in the form of DDoS attacks.

How UDP works?

UDP uses IP to transfer a datagram from one system to another. UDP operates by collecting data in a UDP packet and adding its header information to the package. This data consists of the origin and target ports to communicate on, the packet length, and a checksum. After the UDP data packets are grouped in an IP packet, they’re sent off to their destinations.

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UDP does not guarantee delivery because it does not link directly to the receiving machine, unlike TCP. In this case, it sends the package out and leaves it on the devices in between so that the data can be safely sent and received by the intended recipients.

Features of UDP

  • One of the fastest modes of data transfer.
  • Fire and forget type protocol, i.e., trigger it, and you will lose control.
  • Ideal for DNS and NFS.
  • Although an unreliable protocol, suitable for video streaming because of its fast and lightweight characteristics.
  • The sender can overrun the receiver’s buffer.
  • No handshaking and flow control.
  • No withdrawing capabilities.
  • You can detect an error but cannot control them.

Advantages of UDP

  • Packet sizes are smaller than TCP by about 60%.
  • No connection to create and maintain before sending the data out.
  • Faster and quicker than other protocols.
  • Supports packet switching.
  • It never restricts you to a connection-based communication model; that’s why startup latency in distributed applications is low.
  • For error detection, it uses a checksum.
  • Ideal for video streaming.

Disadvantages of UDP

  • A data packet can be lost or will not be delivered in UDP, or some elements could be lost in the transmission.
  • The order can be not what the sender intended it to be.
  • Routers are quite careless with UDP, so they never retransmit it if it collides.
  • Only the application layer deals with error recovery.
  • No congestion control or flow control. 
  • UDP mostly likely will suffer from worse packet loss, and there is no way of data recovery. 
  • Routers prefer TCP datagram over UDP.
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Real-time applications of UDP

  • UDP is the right way for request-response communication, where the data size is relatively less.
  • UDP is typically used for real-time applications that can not tolerate uneven delays between sections of a received datagram.
  • Multicasting: It is a suitable protocol for multicasting( like streaming and as UDP supports packet switching.
  • Null protocol: UDP can also be used for the null protocol if you remove the checksum field.
  • Routing protocol: UDP is used for Routing Information Protocol, i.e., for exchanging network protocol.
  • UDP is used as a transport layer protocol: NTP (Network Time Protocol), DNS (Domain Name Service), BOOTP, DHCP, NNTP (Network News Transfer Protocol), TFTP, RTSP, OSPF, etc.
  • Other assignments: The application layer can do some of the tasks like Source routing, trace routing, and Timestamp.

Key Differences between TCP vs UDP

Relatively reliableRelatively unreliable
Is connection basedDoes not require any type of connection between two devices
Relatively slowerRelatively quicker.
Datagram oriented protocolConnection-oriented protocol
TCP provides extensive error checking mechanisms, that is because it provides flow control and acknowledgment of data.Has the basic error checking mechanism with the help of checksums.
The specified  order sequence is maintainedThe specified order sequence is not maintained
Retransmission is possible in case the transmission is terminated, or data is lost.Retransmission is not possible in case the transmission is terminated, or data is lost.
Heavyweight protocol.Lightweight protocolDoes not support broadcastingIt supports broadcastingFlexible length header(20-80)Fixed length header(8-bytes)Data recovery facilityNo data recovery facilityTCP is used by HTTP, HTTPs, FTP, SMTP and Telnet.Used by DNS, DHCP, TFTP, SNMP, RIP, and VoIP.


Is UDP better than TCP?

TCP lags behind UDP in terms of speed. UDP is more efficient, faster, and simpler than TCP. TCP allows the retransmission of dropped packets, however, UDP does not. The User Datagram Protocol does not allow for the retransmission of lost packets (UDP).

Where are TCP and UDP used?

When it comes to network congestion and segmentation, TCP plays a key role. TCP is preferred when network interface error correction is required. Time-sensitive applications and servers that respond to modest queries from a large number of clients frequently employ UDP.