220-1201 Networking Study Guide for the CompTIA A+ Core Series Exam

General Information

Understanding all types of networks and their corresponding connections is vital if you are in an IT support position. You will need to know everything about TCP/IP, Wi-Fi, and SOHO connections. About 23% of the CompTIA A+ 1201 test concerns various aspects of networking. Only about 13% of the questions concerning networking begin with a scenario.

Transmission Control Protocol (TCP) and User Datagram Protocol (UDP)

For the CompTIA A+ exam, you must be able to compare and contrast TCP and UDP ports and protocols and their respective purposes. Memorizing port numbers is highly recommended for this section.

Transmission Central Protocol (TCP) vs. User Datagram Protocol (UDP)

TCP is a connection-oriented protocol used to send and receive data over a network. Before data is sent, a connection is established with the receiving host. It is considered a reliable protocol because the receiving host acknowledges that it received the data. TCP is used in cases where receiving the proper data is more important than speed.

UDP is a connectionless protocol. Data is sent without any assurance that the receiving host is actually receiving the data. For that reason, it is considered an unreliable protocol. The advantage of UDP over TCP is that it is faster.

Note: While both the TCP and UDP protocols utilize the IP protocol, the term TCP/IP refers to an entire suite of protocols that are used to ensure connection prior to transmission, including the Domain Name System (DNS) and Address Resolution Protocol (ARP) protocols. The UDP protocol, on the other hand, does not utilize these additional protocols to ensure proper connection or delivery.

Ports and Protocols

The Transmission Control Protocol (TCP) and the User Datagram Protocol (UDP) are two transport layer protocols used for transmitting data over a network connection in conjunction with the IP protocol, which is a network layer protocol.

For this exam, you should know the following TCP/UDP port numbers, the protocols that run over those ports, and the primary use for each. A port is the unique identifier number for transmission control and direction. A protocol is a set of rules that govern communications.

20-21—File Transfer Protocol (FTP)

FTP is used to manipulate files. FTP can copy files, list and manipulate directories, and view file contents. FTP runs on ports 20 and 21. Port 21 is mainly used for file management, while port 20 is used for data transfer. FTP is not secure and transmits in plaintext.

22—Secure Shell (SSH)

SSH is a connection-oriented protocol used to set up secure Telnet connections for remote logins. SSH is secure and runs on port 22.

23—Telnet

Telnet is a terminal emulation program that allows for remote access to text on another computer. Telnet is not secure and transmits plaintext. Telnet uses port 23.

25—Simple Mail Transfer Protocol (SMTP)

SMTP is used to send email only and is a push protocol. SMTP uses port 25.

53—Domain Name System (DNS)

DNS is used to resolve hostnames to IP addresses and uses port 53.

67/68—Dynamic Host Configuration Protocol (DHCP)

DHCP assigns IP addresses dynamically to network clients. DHCP uses port 67 for the server and port 68 for the client.

80—Hypertext Transfer Protocol (HTTP)

HTTP manages communications between a web server and a client to view internet content. HTTP is not secure and transmits in plaintext. HTTP uses port 80.

110—Post Office Protocol 3 (POP3)

POP3 is used for downloading email and uses port 110.

143—Internet Mail Access Protocol (IMAP)

IMAP is currently in its fourth version, or IMAP4, and is used for downloading email. IMAP4 is secure and runs over port 143.

137-139—Network Basic Input/Output System (NetBIOS)/NetBIOS over TCP/IP (NetBT)

NetBIOS is an application programming interface (API) for communication between computers over a network. NetBIOS works over the Open Systems Interconnection (OSI) Layer 4 and needs to work with a Layer 5 protocol, namely TCP/IP, to function properly. NetBIOS over TCP/IP is called NetBT. NetBIOS runs on ports 137/139.

389—Lightweight Directory Access Protocol (LDAP)

LDAP is used for accessing information stored in an information directory. LDAP uses port 389.

443—Hypertext Transfer Protocol Secure (HTTPS)

HTTPS is the secure version of HTTP. HTTPS uses port 443.

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

SMB is primarily a Microsoft protocol used for shared file access. CIFS is an enhanced version of SMB. SMB and CIFS both use port 445.

3389—Remote Desktop Protocol (RDP)

RDP allows for remote connection to computers and uses port 3389.

Wireless Networking Technologies and Specifications

You must be able to identify, explain, and compare and contrast wireless networking specifications and technologies, which includes recognizing what they have in common and where they differ.

Frequencies

The frequency of a wireless protocol refers to the audio range in which the technology broadcasts. The three operating frequencies for Wi-Fi are 2.4 GHz, 5 GHz, and 6 GHz. The frequency has an impact on transmission range and data throughput.

2.4 GHz

The 2.4 GHz frequency is approximately 70 MHz wide. This relatively low frequency (compared with 5 GHz) has a greater transmission range because it passes through objects, including walls and floors, better. On the negative side, throughput is slower, and it is an open frequency range that other devices use. Furthermore, devices like cordless phones and microwave ovens can interfere with it.

5 GHz

The 5 GHz frequency is approximately 500 MHz wide. At this higher frequency, throughput is faster. On the negative side, the transmission range is shorter as the signal is attenuated by objects such as walls and floors.

6 GHz

The 6 GHz frequency is approximately 1,200 MHz wide. The 6 GHz frequency is the newest available frequency and has the ability to provide gigabit speeds without interference from the other frequencies. Only newer devices that are Wi-Fi 6E enabled are able to use this frequency.

Channels

Channels are different frequencies that are used for communications between the end-user device and the wireless access point.

Regulations

The Federal Communications Commission (FCC) is a government agency that allocates and manages frequency spectrums for non-military use. The FCC has defined 14 different communications channels in the 2.4 GHz frequency range, but only allows for the use of the first 11 channels. In the 5 GHz frequency range, there are 24 channels available for use, and in the 6 GHz frequency range, there are 59 channels available for use.

Channel Selection

Channel selection by a connecting device can be either manual or automatic. For optimum transmission, the channel with the least amount of interference or congestion is commonly used.

Widths

The channel width is how much of the frequency is allocated to each channel and affects the amount of data that can be transmitted over a channel at once. The 2.4 GHz frequency most commonly has a width of 22 MHz but can support a width of 40 MHz. The 5 GHz and 6 GHz frequencies are capable of supporting 20, 40, 80, and 160 MHz channels.

Frequencies

For optimal transmission, channel frequencies are non-overlapping. Non-overlapping frequencies refers to a set of frequencies that can be used simultaneously without causing interference with one another. In the image below, the shaded area corresponds to non-overlapping channels, as shown by the white space present between each set of frequencies.

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Bands

The wireless frequency band refers to the complete range of frequencies included, such as 2.4 GHz, 5 GHz, and 6 GHz. For example, the 2.4 GHz band includes all the frequencies within 2.4 GHz, such as channel 6, which has a frequency range of 2.427 to 2.447, and channel 11, which has a frequency range of 2.452 and 2.472.

802.11 Standards

The Wi-Fi specification 802.11 is part of the IEEE 802 wireless networking standards. It is used for wireless local area network (WLAN), commonly referred to as Wi-Fi communications. All of the 802.11 Wi-Fi standards use the Ethernet protocol and carrier-sense multiple access with collision avoidance (CSMA/CA) media access method. The main characteristics that differentiate each Wi-Fi standard are their operating frequencies, theoretical maximum data speed, and throughput.

Bluetooth

Bluetooth allows devices to communicate over short distances (10 meters) in a personal area network (PAN). It is typically used to connect peripherals, such as headphones, to a laptop or smartphone. Bluetooth is the IEEE 802.15.1 standard.

Near-Field Communication (NFC)

NFC has a very short range of a few inches. It is used for contactless communications between devices that are right next to one another. The most common use today is for contactless payment systems.

Radio-Frequency Identification (RFID)

RFID uses a radio signal to send information from an RFID tag with identifying information. This is commonly used to streamline the inventory of tracking applications.