Common Protocols

Question 1

TCP (Transmission Control Protocol)

Answer 1

• Reliable
• Connection-oriented
• Virtual circuit
• Sequenced
• Acknowledgements
• 24 - 60 bytes (high overhead)

Question 2

UDP (User Datagram Protocol)

Answer 2

• Unreliable
• Connectionless
• No virtual circuit
• Un-sequenced
• No acknowledgments
• 8 bytes (lightweight)

Question 3

FTP - File Transfer Protocol

Answer 3

• Used to share files with users in a LAN or a WAN
• TCP Port 20 (active), 21 (control)
• Supports authentication, authorization, and directory browsing
• Unencrypted – not recommended, use sftp.

Question 4

TFTP - Trivial File Transfer Protocol

Answer 4

• Used to push (put) or pull (get) files from a server
• Commonly used to manage devices like IP phones, routers and switches
• Does NOT support authentication, authorization, or directory browsing
• UDP port 69
• Unencrypted – not recommended, use sftp

Question 5

SFTP - Secure File Transfer Protocol

Answer 5

• A secure implementation of FTP
• Supports all the same functions as FTP but with encryption
• SFTP is an extension of SSH which is why they use the same port number
• TCP Port 22

Question 6

SMTP - Simple Mail Transfer Protocol

Answer 6

• Sends outgoing mail to a server
• TCP Port 25

Question 7

POP3 - Post Office Protocol

Answer 7

• Downloads incoming mail from a server
• TCP Port 110

Question 8

IMAP - Internet Message Access Protocol

Answer 8

• Synchronizes incoming mail from a server
• TCP Port 143

Question 9

Telnet - Telecommunication Network

Answer 9

• Provides remote command line access to interact with a server
• Considered insecure and should no longer be used, use SSH instead
• TCP Port 23

Question 10

SSH - Secure Shell

Answer 10

• Provides encrypted remote command line access to interact with a server
• SSH version 2 added SFTP and SCP support
• TCP Port 22

Question 11

DNS - Domain Name Service

Answer 11

• Provides name to IP address resolution for host
• Resolves Domain name to IP address
• TCP/UDP Port 53 (mostly UDP but moving towards TCP)

Question 12

DHCP - Dynamic Host Configuration Protocol

Answer 12

• Provides various configurations to clients in an IP network via broadcast
• UDP Port 67 (server)
• UDP Port 68 (client)

Question 13

HTTP - Hyper Text Transfer Protocol

Answer 13

• Used to transmit webpages
• TCP Port 80

Question 14

HTTPS - Hyper Text Transfer Protocol Secure

Answer 14

• Used to securely transmit encrypted
webpages using SSL or TLS
• TCP Port 443

Question 15

NetBios - Network Basic Input/Output System

Answer 15

• Provides various network communication features in a Windows network
• Used in Windows before IP networking
• NetBIOS over TCP/IP is still used in Windows

UDP Port 137
NetBIOS name services (nbname)

TCP Port 139
NetBIOS session service (nbsession)

Question 16

SNMP - Simple Network Management Protocol

Answer 16

• Used to query, configure, and monitor host in a LAN
• SNMPv3 encrypts communication where previous versions did not
• UDP Port 161 (Queries)
• UDP Port 162 (Traps)

Question 17

LDAP - Lightweight Directory Access Protocol

Answer 17

• Used in domain-based network
environments to facilitate system and user management.
• TCP/UPD Port 389 (mainly TCP)

Question 18

SMB - Server Message Block

Answer 18

• Provides file sharing, network browsing, and printing services
• Commonly used in Windows networks but supported in Linux, macOS, and many other devices
• CIFS (Common Internet File System) is an open implementation used on Linux and macOS
• TCP Port 445 (NetBIOS-less)

Question 19

RDP - Remote Desktop Protocol

Answer 19

• Used to securely remotely access a Windows desktop
• TCP Port 3389