CompTIA A+ 220-1201 (V15) - Domain 2: Networking (23%)

FTP - File Transfer Protocol

Transfer files between systems. Authenticates with a username and password or some other type of generic / anonymous login. Full feature functionality (List, Add, Delete, etc.)

• TCP / Port 20 (Active Mode Data)

• TCP / Port 21 (Administration/Control)

SSH - Secure Shell

Provides an encrypted communication link. Looks and acts the same as Telnet protocol (old)

• TCP / Port 22

Telnet Protocol - Telecommunication Network

Works identical to SSH, has command line, can log into a device with username and password, can administer that device remotely BUT there is NO ENCRYPTION used. }

• TCP / Port 23

SMTP - Simple Mail Transfer Protocol

Server to server email transfer. Also used to send mail from a device to a mail server, commonly configured on mobile devices and email

• TCP / Port 25

DNS - Domain Name System

Converts domain name (website name) to IP address

• UDP / Port 53

DHCP - Dynamic Host Configuration Protocol

Automated configuration of IP addresses, Subnet Mask, Default Gateway or DNS servers.

• UDP / Port 67 (Server)

• UDP / Port 68 (Client)

HTTP - Hypertext Transfer Protocol

Web server communication

• TCP / Port 80

HTTPS - Hypertext Transfer Protocol Secure

Web server communication with encryption, more secure than HTTP

• TCP / Port 443

POP 3 - Post Office Protocol (Version 3)

Receives emails from an email server (often downloads to device) - Authenticate and transfer

Basic mail transfer functionality

• TCP / Port 110

IMAP 4 - Internet Message Access Protocol (Version 4)

Allows you to manage your email inbox on the server and keep them synchronized across multiple devices

• Use: make folders, and transfer emails into those folders

• TCP / Port 143

SMB - Server Message Block

Protocol used by Microsoft Windows. Also called CIFS (Common Internet File System)

Use: File transfer / sharing and send information to printers queues and for other processes where Windows need to communicate information between different Windows devices

• TCP / Port 445 (modern, direct hosted)

NetBIOS over TCP/IP (NetBT) - Older version

UDP / Port 137 - NetBIOS name services (nbname)

TCP / 139 - NetBIOS session service (nbsession)

LDAP - Lightweight Directory Access Protocol

Store and retrieve information in a network.

Example: Microsoft Active Directory

• TCP / Port 389

LDAPS - Lightweight Directory Access Protocol Secure

LDAP wrapped in TLS so directory look-ups are protected in transit.

• TCP / Port 636

RDP - Remote Desktop Protocol

Share a desktop from a remote location over TCP / Port 3389. Can connect to an entire desktop or just an application

TCP - Transmission Control Protocol

Connection-oriented, reliable delivery, error checking, used for web, email, file transfer

• Example: HTTPS (Hypertext Transfer Protocol) & SSH (Secure Shell)

• Benefit: Guaranteed delivery, ordered packets, suitable for data integrity requirements

UDP - User Datagram Protocol

Connection-less, faster but unreliable, no error checking, used for streaming, VoIP, gaming

• Benefit: Lower latency, suitable for real-time applications that can tolerate packet loss

RFID (Radio Frequency Identification)

Uses radio waves for identification (Access Badges, Product Tags)

• Tags: Antenna + Chip

  • Most RFID are Passive: No battery, powered by scanner’s radio waves

  • Some Active: Has battery, longer range

• One-way communication (Tag to Scanner)

NFC (Near Field Communication)

Two-way wireless communication

• Builds on RFID, which is mostly one-way

• Very short range (4cm) (tap to connect) payments, device pairing, no pairing required

Uses: Contactless payments, quick device setup/pairing, identification

2.4 GHz

• Longer range

• Better wall penetration

• More interference (microwaves, Bluetooth, cordless phones)

5 GHz

• Shorter range

• Less interference from common household devices

• More available channels

• Faster speeds

• More non-overlapping channels available, less congestion

6 GHz

• Most spectrum (1,200 MHz), no legacy device interference

• Wi-Fi 6E only

• Shortest range

802.11n

• Up to 600 Mbps, 2.4 GHz and 5 GHz

• MIMO support

802.11ac

• Up to 1.3 Gbps, 5 GHz only

• MU-MIMO support

802.11ax (Wi-Fi 6/6E)

• Up to 9.6 Gbps, 2.4/5/6 GHz,

• OFDMA

• Better efficiency in dense environments

WPA2 with AES - Wi-Fi Protected Access 2

Minimum recommended security for business networks

WPA3 - Wi-Fi Protected Access 3

• Latest standard

• stronger encryption

• protection against brute-force attacks

Bluetooth

• Short-range (10-100m)

• device pairing

• low power consumption

2.4 GHz non-overlapping channels

1, 6, and 11 (North America) - use these to avoid interference

Channel width

Wider channels (40 MHz, 80 MHz) provide faster speeds but more interference

Channel overlap

Causes interference and reduced performance

NTP (Network Time Protocol)

Synchronizes system clocks across network

• NTP server

  • Responds to time requests form NTP clients

• NTP clients

  • Requests time updates from NTP server

  • Daily synchronization is common

DNS (Domain Name System) Server

Translates domain names to IP addresses, critical for internet connectivity

DHCP (Dynamic Host Configure Protocol) Server

Automatically assigns IP addresses, subnet masks, gateways, and DNS servers to clients

File server

Centralized file storage and sharing so you and the other people in the organization can access it. Example: sharing spreadsheets, documents, etc.

• Windows: SMB/CIFS

• Linux: NFS (Network File System)

• Apple: AFD (Apple Filing Protocol)

Print server

Manages network printers, handles print queues and job distribution

• Standard Printing Protocols:

  • SMB (Server Message Block)

  • IPP (Internet Printing Protocol)

  • LDP (Line Printer Daemon)

Mail server

Handles email delivery (SMTP for sending and POP3/IMAP for receiving)

Web server

• Hosts websites and web applications (HTTP/HTTPS)

• Pages are built with HTML, HTML5

Database server

Stores and manages structured data for applications

• Database Table Storage

  • Save information in columns and rows

  • Similar to a spreadsheet

• Relational Database

  • Links tables together

  • These links are relationships

  • Flexible and fast

• Structured Query Language (SQL)

  • Access data using a standard language

  • Microsoft SQL Server, MySQL

Proxy server

Intermediary “middleman” for client requests

• Useful features:

  • Access control

  • Caching

  • Content scanning

  • URL filtering

Load balancer

Distributes traffic across multiple servers for performance and redundancy

UTM (Unified Threat Management) / Web Security Gateway

All-in-one security appliance

• Combines firewall, antivirus, IDS/IPS, content filtering

Spam gateway

Filters unwanted email before reaching mail server

Syslog

• A standard protocol for message logging, allowing devices like routers, servers, and applications to send event notifications to a centralized collector.

• It enhances security and troubleshooting by providing a unified view of system activity and facilitates compliance. It typically operates on UDP port 514, though modern versions support TCP

IoT (Internet of Things)

Appliances:

• Refridgerators

Smart devices:

• Smart speakers, respond to voice commands

Air Control:

• Thermostats

Access:

• Smart doorbells, doors, and windows

Security considerations

• Change default passwords

• Isolate on separate VLAN

• Regular firmware updates

SCADA (Supervisory Control and Data Acquisition System) / ICS (Industrial Control Systems)

Industrial control systems for manufacturing, utilities, infrastructure

Authentication Server

• AAA - Authentication, Authorization, and Accounting

  • The login server

• Login authentication to resources

  • Centralized management

• Almost always an enterprise service

  • Not required on a home network

Legacy and Embedded Systems

Legacy Systems “really old”

Embedded Systems “built in”

• Not usual to have direct access to the operating system

• Alarm system, door security, time card system

LAN (Local Area Network)

A group of devices in the same broadcast domain