CompTIA A+ 1101 Comprehensive Port Numbers and Protocols Study Guide

File Transfer and Shared Resource Protocols

• FTP (File Transfer Protocol): This protocol is characterized by its use of two separate channels for communication.

  • Active Data Mode: Utilizes port tcp/$20$ for the actual transfer of file data.

  • Control Mode: Utilizes port tcp/$21$ for the transmission of commands and status updates between the client and server.

• SMB (Server Message Block) & CIFS (Common Internet File System): A network file sharing protocol that allows applications on a computer to read and write to files and to request services from server programs in a computer network. It operates on port tcp/$445$.

Remote Access and Terminal Protocols

• SSH (Secure Shell): A cryptographic network protocol for operating network services securely over an unsecured network. It is primarily used for secure remote login into a computer system and operates on port tcp/$22$.

• Telnet (Telecommunication Network): An application layer protocol used on the Internet or local area network to provide a bidirectional interactive text-oriented communication facility using a virtual terminal connection. It operates on port tcp/$23$.

• RDP (Remote Desktop Protocol): A proprietary protocol developed by Microsoft which provides a user with a graphical interface to connect to another computer over a network connection. It operates on port tcp/$3389$.

Email Delivery and Management Protocols

• SMTP (Simple Mail Transfer Protocol): An internet standard communication protocol for electronic mail transmission. It is used by mail servers and other message transfer agents to send and receive mail messages. It operates on port tcp/$25$.

• POP3 (Post Office Protocol version 3): An application-layer Internet standard protocol used by e-mail clients to retrieve e-mail from a mail server. It typically involves downloading the message to a local device and deleting it from the server. It operates on port tcp/$110$.

• IMAP4 (Internet Message Access Protocol, version 4): An Internet standard protocol used by email clients to retrieve email messages from a mail server over a TCP/IP connection. Unlike POP3, it allows for synchronization across multiple devices. It operates on port tcp/$143$.

Network Infrastructure and Naming Services

• DNS (Domain Name System): A hierarchical and decentralized naming system for computers, services, or other resources connected to the Internet or a private network. It translates human-readable domain names into numerical IP addresses. It operates on port udp/$53$.

• DHCP (Dynamic Host Configuration Protocol): A network management protocol used on Internet Protocol (IP) networks for automatically assigning IP addresses and other communication parameters to devices. It utilizes two ports:

  • udp/$67$

  • udp/$68$

• NetBIOS (Network Basic Input/Output System) Services:

  • NBNAME (NetBIOS Name Service): Used for name registration and resolution. It operates on port udp/$137$.

  • NBSESSION (NetBIOS Session Service): Used for session-oriented communication. It operates on port udp/$139$.

Web and Directory Access Protocols

• HTTP (Hypertext Transfer Protocol): The foundation of any data exchange on the Web and a protocol used for transmitting hypermedia documents, such as HTML. It operates on port tcp/$80$.

• HTTPS (Hypertext Transfer Protocol Secure): An extension of the Hypertext Transfer Protocol (HTTP) used for secure communication over a computer network, utilizing encryption. It operates on port tcp/$443$.

• LDAP (Lightweight Directory Access Protocol): An open, vendor-neutral, industry-standard application protocol for accessing and maintaining distributed directory information services over an Internet Protocol (IP) network. It operates on port tcp/$389$.

Network Management and Monitoring

• SNMP (Simple Network Management Protocol): An Internet Standard protocol for collecting and organizing information about managed devices on IP networks and for modifying that information to change device behavior.

  • Queries: Communication initiated to request information from a device occurs on port udp/$161$.

  • Traps: Unsolicited notifications sent from a managed device to a management station occur on port udp/$162$.

Port Classification and Range Standards

• Non-Ephemeral Ports:

  • These are defined as permanent port numbers.

  • They encompass the range of ports from $0$ through $1023$.

• Ephemeral Ports:

  • These are defined as temporary port numbers.

  • The specific port number used is determined in real-time by the client during a communication session.

  • They encompass the range of ports from $1024$ through $65535$.