TCP & UDP | Day 30

What port and protocol are used for FTP Data?

TCP Port 20

What port and protocol are used for FTP Control?

TCP Port 21

What port and protocol are used for SSH?

TCP Port 22

What port and protocol are used for Telnet?

TCP Port 23

What port and protocol are used for SMTP?

TCP Port 25

What port and protocols are used for DNS?

TCP/UDP Port 53

What port and protocol are used for a DHCP Server?

UDP Port 67

What port and protocol are used for a DHCP Client?

UDP Port 68

What port and protocol are used for TFTP?

UDP Port 69

What port and protocol are used for HTTP?

TCP Port 80

What port and protocol are used for POP3?

TCP Port 110

What port and protocol are used for an SNMP Agent?

UDP Port 161

What port and protocol are used for an SNMP Manager?

UDP Port 162

What port and protocol are used for HTTPS?

TCP Port 443

What port and protocol are used for Syslog?

UDP Port 514

What does TCP stand for?

Transmission Control Protocol

What does UDP stand for?

User Datagram Protocol

What are Layer 4 addresses called?

Port numbers

Which protocol provides reliable data transfer, error recovery, data sequencing, and flow control?

TCP

Which protocol is connectionless, has less overhead, and is preferred for real-time voice and video?

UDP

What does the Layer 4 destination port number indicate?

The Application Layer protocol

Is the Layer 4 source or destination port randomly selected by the initiating host?

The Source port

What is the IANA range for well-known ports?

0 - 1023

What is the IANA range for registered ports?

1024 - 49151

What is the IANA range for ephemeral (dynamic) ports?

49152 - 65535

Which TCP header field is used for flow control?

Window Size

What is the order of messages in a TCP 3-way handshake (establishing a connection)?

SYN ->,

What is the order of messages in a TCP 4-way handshake (terminating a connection)?

FIN ->,

In TCP, what mechanism indicates the sequence number of the next segment the host expects to receive?

Forward Acknowledgement

In TCP, what mechanism is used to dynamically adjust how large the window size is?

Sliding Window

What is the primary function of OSI Layer 4 (Transport Layer)?

To provide process-to-process (or host-to-host) communication using port numbers.

How does Layer 4 achieve Session Multiplexing?

By using different random Source Port numbers to keep separate sessions (like multiple browser tabs) isolated, even if they connect to the same Destination IP and Port.

What are the three IANA port ranges and their values?

Well-known (0 - 1023), Registered (1024 - 49151), and Ephemeral/Dynamic (49152 - 65535).

Which port range does a client PC typically use to randomly select its Source Port?

Ephemeral / Dynamic Ports (49152 - 65535).

Is TCP connection-oriented or connectionless?

Connection-oriented (it requires a 3-way handshake before sending any actual data).

What are the three steps of the TCP 3-Way Handshake to establish a connection?

1. SYN (Client to Server) | 2. SYN-ACK (Server to Client) | 3. ACK (Client to Server).

What are the four steps of the TCP 4-Way Handshake to terminate a connection?

FIN -> ACK -> FIN -> ACK.

In TCP, what does "Forward Acknowledgment" mean?

The Acknowledgment (ACK) number sent back always indicates the sequence number of the NEXT segment the receiver expects to get.

Which TCP header field is used for Flow Control?

Window Size (it dynamically adjusts how much data can be sent before requiring an acknowledgment).

If a TCP segment is lost in transit and the sender never receives an ACK, what happens?

TCP Retransmission (the sender's timer expires, and it sends the segment again).

Is UDP connection-oriented or connectionless?

Connectionless (it sends data immediately without a handshake, acting as "best-effort" delivery).

Between TCP and UDP, which one provides sequencing and error recovery (retransmissions)?

TCP. (UDP provides neither).

What are common real-world use cases for UDP?

VoIP (voice calls), Live Video Streaming, and Online Gaming (where speed is prioritized over perfect reliability).

What are common real-world use cases for TCP?

Web browsing (HTTP/HTTPS), Emails (SMTP), and File Downloads (FTP) where data integrity is required.

Which protocol (TCP or UDP) does DNS use?

Both! Mostly UDP for fast client queries, but TCP for large data transfers like Zone Transfers.