Chapter 4. TCP and UDP Ports and Protocols

What is the primary difference between TCP and UDP transport methods?

TCP is connection-oriented, guarantees packet delivery, and uses flow control; UDP is connectionless, faster, does not check for dropped packets, and is ideal for streaming media

What are the three steps of the TCP three-way handshake in order?

1. SYN, 2. SYN-ACK, 3. ACK

What is a TCP socket connection?

The established network connection formed once a server receives the final ACK packet in a three-way handshake

What mechanism does TCP use to prevent a sending computer from overwhelming a receiving server with too much data too quickly?

Flow control

What port and transport protocol are used by unencrypted HTTP?

Port 80 over TCP

What port, transport protocol, and underlying security protocol does HTTPS use to ensure private, encrypted web communication?

Port 443 over TCP using Transport Layer Security (TLS)

What are the unencrypted and secure (SSL/TLS) default ports for the SMTP email sending protocol?

Unencrypted: Port 25; Secure: Ports 587 or 465 (TCP)

What are the unencrypted and secure (SSL/TLS) default ports for the POP3 email retrieval protocol?

Unencrypted: Port 110; Secure: Port 995 (TCP)

What are the unencrypted and secure (SSL/TLS) default ports for the IMAP email retrieval protocol?

Unencrypted: Port 143; Secure: Port 993 (TCP)

What are the two historical port numbers associated with the connection-oriented File Transfer Protocol (FTP)?

Ports 20 and 21 over TCP (21 for connection/control, 20 historically for data transfer)

What port and transport protocol are used by Secure Shell (SSH) to provide an encrypted channel for remote command-line control and Secure FTP (SFTP)?

Port 22 over TCP

What insecure, clear-text remote command-line utility utilizes port 23 and is typically deprecated/disabled by default?

Telnet (TCP or UDP)

What transport protocol and default ports are used by a DHCPv4 server and client to automatically assign IP addresses?

UDP; Server listens on inbound Port 67, Client connects out using Port 68

What port does the Domain Name System (DNS) use by default to translate human-readable domain names into IP addresses?

Port 53 (TCP or UDP)

What are the unencrypted and secure default ports used by the Lightweight Directory Access Protocol (LDAP) to query Microsoft Active Directory?

Unencrypted: Port 389; Secure: Port 636 (TCP or UDP)

What proprietary Microsoft protocol utilizes port 3389 over TCP to allow administrators full remote desktop control and Remote Assistance capabilities?

Remote Desktop Protocol (RDP)

What protocol provides authenticated access to shared files and printers, communicating directly over TCP port 445 or via legacy NetBIOS/NetBT ports 137–139?

Server Message Block (SMB) / Common Internet File System (CIFS)

What protocol uses port 161 for device monitoring and port 162 for alerts (traps) sent to a central Network Management System (NMS)?

Simple Network Management Protocol (SNMP)

What is the most secure version of SNMP, and what cryptographic standards does it support to ensure data confidentiality?

SNMPv3; supports AES, HMAC-SHA, and HMAC-MD5

A web server needs to accept secure incoming traffic from the public internet. Which inbound port must remain open on the firewall?

Port 443 (HTTPS)

What command-line utility should you run in Windows to identify the exact IP address of the local DNS server resolving names for the host?

ipconfig /all

What command-line tool can a technician use to verify if inbound ports like 3389 (RDP) or 389 (LDAP) are actively open and listening on a server?

netstat

What is the core operational difference between a statically assigned IP address and a dynamically assigned DHCP address?

A static address is manually assigned by an admin and never changes; a dynamic address is leased from a central server and can change periodically

What specific, connectionless file transfer protocol is utilized primarily for booting a client workstation or thin client directly from a network?

Trivial File Transfer Protocol (TFTP)