CompTIA A+ | TCP vs UDP

TCP

Transmission Control Protocol. Connection-oriented, reliable, guarantees delivery and correct order.

UDP

User Datagram Protocol. Connectionless faster, no delivery guarentee.

Connection-oriented

A connection is established before data is sent, and delivery is confirmed (TCP).

Connectionless

Data is sent without setting up a connection or confirming delivery (UDP).Three

Three-way handshake

How TCP opens a connection: SYN → SYN-ACK → ACK

SYN

Synchronize. The first step of the TCP handshake, where the client requests a connection.

SYN-ACK

Synchronize-Acknowledge. The server’s reply agreeing to the connection.A

ACK

Acknowledge. The client confirms, and the connection is established

Which protocol resends lost data?

TCPWbh

Which protocol has less overhead and is faster?

UDPWhy d

Why does TCP have more overhead than UDP?

It sets up connections, confirms delivery, and resends lost data.

What kinds of traffic use UDP?

Time-sensitive traffic where speed matters more than perfection: streaming, VoIP, online gaming, DNS lookups, DHCP.

What kinds of traffic use TCP?

Traffic that must arrive complete and accurate: web pages, email, file transfers, remote access.

A video call needs a low delay, and a few dropped packets are okay. TCP or UDP?

UDP

A user is downloading a file that must arrive with no missing pieces. TCP or UDP?

TCP

Which protocol does DNS use for normal lookups?

UDP (TCP is used for larger transfers like zone transfers)

Which protocol does DHCP use?

UDP

Which protocol do HTTP, HTTPS, SSH, SMTP, and RDP use?

TCP