Section 2

A set of protocols used to connect network devices to each other.

A set of protocols used to connect network devices to each other.

TCP/IP

Responsible for the communication protocols between nodes. The protocols in this layer include hypertext transfer protocol (HTTP and HTTPS), Secure Shell (SSH), and network time protocol (NTP), among many others.

TCP/IP Application Layer

Responsible for the end-to-end transport of data. The protocols that live in this layer are transmission control protocol (TCP) and user datagram protocol (UDP).

TCP/IP Transport Layer

Defines the logical transmission protocols for the whole network. The main protocols that live in this layer are internet protocol (IP), internet control message protocol (ICMP), and address resolution protocol (ARP).

TCP/IP Network Layer

Establishes how data should be physically sent through the network.

TCP/IP Network Interface Layer

This network model consists of a seven-layer architecture that organizes the sending of data from hosts across a network

The OSI (Open System Interconnection) model

This layer is responsible for the physical connections of the devices in the network. This layer is implemented through the use of devices such as hubs, repeaters, modem devices, and physical cabling.

OSI Physical Layer or Layer 1

This layer is responsible for the error-free delivery of data to the receiving device or node. This layer is implemented through the use of devices such as switches and bridge devices, as well as anything with a network interface, like wireless or wired network cards.

OSI Data Link Layer or Layer 2

This layer is responsible for the transmission of data between hosts in different networks as well as routing of data packets. This layer is implemented through the use of devices such as routers and some switches.

OSI Network Layer or Layer 3

This layer provides services to the application layer and receives services from the network layer. It is responsible for the reliable delivery of data. It segments and reassembles data in the correct order for it to be sent to the receiving device. It may also handle the reliable delivery of data and any retries of data that are lost or corrupted (for example, TCP does this). This layer is often called the heart of OSI.

OSI Transport Layer or Layer 4

This layer is responsible for connection establishment, session maintenance, and authentication.

OSI Session Layer or Layer 5

This layer is responsible for translating data from the application layer into the format required to transmit the data over the network as well as encrypting the data for security if encryption is used.

OSI Presentation Layer or Layer 6

This layer is responsible for network applications (like HTTP or FTP) and their production of data to be transferred over the network.

OSI Application Layer or Layer 7

A device necessary for sending and receiving data over analog lines, such as phone or cable lines.

Modem

A device that acts as a point of connection between two or more networks that forwards data packets between networks. To have internet in your home, you need an this device that connects the networks on the internet to the network of your home. You can access the internet’s network either through a wired Ethernet port of via Wi-Fi.

Router

This device is used to connect devices in a specific network and allows them to communicate efficiently within the network. It is a more complex version of a hub, in that they have the capability to add security measures and function far more intelligently, sending traffic directly from the sender to the receiver without the other devices being aware of the communication. Thus, this device is less chatty and allows for more simultaneous conversations between devices. Most internet routers include a this in the form of wired or wireless Ethernet connections.

Switch

This device is similar to a router in that it connects two or more networks. The difference is that the router analyzes data packets to determine where to send the packet next, whereas this device simply forwards the data to the next network without analysis. This make for fast data transfer that lacks versatility. These devices are not widely used in modern networks, as routers and switches are the favored devices.

Bridge

This is a device used to strengthen, replicate, and regenerate signals that are weakened (for example, because of distance) during transmission. In many large homes, the Wi-Fi signal does not extend to the end of the house farthest from the router. A range extender is a form of this device that takes the distorted Wi-Fi signal and transmits is to the formerly dead zone.

Repeater

This device connects the router to the network, takes the data packets from the router, and sends them to all of the devices connected on the network.

Hub

Operates at the Network and Data Link layers.

Switch (OSI)

Operates at the Network layer.

Router (OSI)

Operates at the Data Link and Physical layers.

Modem (OSI)

Operates at the Data Link layer.

Bridge (OSI)

Operates at the Physical layer.

Repeater (OSI)

This device is a data link layer device. It is available either as a standalone or integrated with other devices, such as wireless routers or modems that can plug in physical devices. It keeps the traffic between the source and destination ports from interfering with other devices in the network.

Switch

This device operates at the network layer and can connect your home network to the Internet. Or, in a business or institutional scenario, it can connect your webserver to your database server.

Router

This can operate at multiple layers of the OSI model, including data link, network, transport, session, and application - and in certain circumstances, presentation as well.

Firewall

At what layers does the firewall defines what traffic should go between two networks?

data link and network

At what layer are the firewall filter settings are port-based?

transport

The firewall that operates at the network and transport layers is called what?

the Layer 4 firewall

The firewall that works at the session, presentation, and application layers is what?

the Layer 7 firewall

What layer firewall is also smart enough to decrypt and analyze the content flowing through, thereby adding one more level of filtering to the IP address and port combination?

The Layer 7 firewall

What is a powerful tool that can help prevent malicious attacks like Structured Query Language, also known as SQL injection, or other malware?

A firewall

These types of are created when pairs of wires are twisted around each other to protect and cancel out interference from each other and outside sources. They are widely used as analog phone cables and in copper Ethernet cables.

UTP Cables

These types of cables are analog cables made of copper but specifically engineered with a metal shield intended to block signal interference. They are mostly used by cable TV companies to connect their customers to the company’s facilities.

Coaxial Cables

These types of cables use glass or plastic threads within cables to transfer data using light (lasers or LEDs) as opposed to traditional metal cables using electricity. They are useful for high bandwidth needs and transfer data digitally, making them more reliable and less susceptible to interference.

Fiber Cables

These types of cables are made up of one single glass or plastic fiber and can carry higher bandwidth for longer distances compared to multimode cables. They are typically used for longer distances and higher bandwidth applications.

Single-mode Fiber Cables

These types of cables are wider in diameter and allow for the transmission of light modes across the cable. They are effective over medium distances and are generally used within a LAN. They are less expensive than single-mode fiber.

Multimode Fiber Cables

These types of cables are used to connect two computing devices of the same type directly to each other. The transmit connector on one end of the wire is connected to the receive connector on the other. These cables are used less frequently today due to built-in capabilities in many standards.

Crossover Cables

These types of cables are used to connect a device to a wall outlet or networking panel. They are commonly used to wire servers in a rack to a switch or connect devices to a network. They are similar in appearance to crossover and UTP cables.

Patch Cables

The ________________, an association of professional electronic and electrical engineers responsible for creating networking standards.

IEEE (Institute of Electrical and Electronics Engineers)

The IEEE standard for wired Ethernet networks.

802.3

The IEEE standard for wireless networks.

802.11

A wired Ethernet standard that provides 1 Gbps transmission over UTP cables.

1000BASE-T

The ability to power a low-power device without plugging it into an electrical outlet, reducing cabling.

Power over Ethernet (PoE)

A wireless networking standard that adds multiple-input multiple-output (MIMO) technology, increasing range and bandwidth.

802.11n

A wireless networking standard that delivers high data rates, up to 1.3 Gbps, in a three-signal design.

802.11ac

A wireless networking standard operating in frequency bands below 1 GHz, designed for IoT devices with limited bandwidth needs over larger distances.

802.11ah

The rebranded name for the 802.11ax standard, which adds support for the 6 GHz frequency range and provides speeds of approximately 1-10 Gbps.

Wi-Fi 6

Command that allows for superuser access so that a user can run commands as an administrator.

sudo

Command that shows how interfaces are set up in a machine.

ifconfig

Command that defines the paths a data packet takes between networks.

route

Command used to verify connectivity and latency.

ping

Command that helps resolve a name associated with an IP address.

nslookup

Local Area Network, a network that connects computers within a limited area, such as a home or office.

LAN

Wide Area Network, a network that connects computers over a large geographical area.

WAN

a software emulation of a computer system.

Virtual Machine

the complete domain name for a specific host on the internet.

FQDN (Fully Qualified Domain Name)

Command that shows the routers and infrastructure devices on the route from one machine to another.

traceroute

Command used to find the owner of a domain and more information about that domain.

whois

A basic tools for testing connectivity to other hosts. It sends an internet control message protocol (ICMP) echo request to a host and listens for the reply. If a reply is received, it will display the time it took and the time to live (TTL) left. It has many options for setting attributes of the request, like the maximum TTL, IPv4/IPv6, and the number of requests to send. It is useful in troubleshooting connectivity with other devices. If a reply is not received, you will receive a timeout message, which could indicate connectivity issues, firewall issues, or both issues with the other device. In addition, due to the time to get a response, the latency between two devices can be measured, enabling a network engineer to troubleshoot performance problems or a network architect to determine where to place devices to minimize response time to other systems and users.

Ping

Commnand(s) used to trace the route an IP packet takes to a destination, displaying each hop (next router) in a numerical list.They are used to trace the route an IP packet takes to a destination. It displays each hop (next router) in a numerical list with the hop’s IP address and the time it takes to receive the packet. It can be useful in determining where a ping fails, troubleshooting performance issues, and other aspects regarding connectivity.

Traceroute/Tracert

Command similar to traceroute/tracert, it displays the path taken by a packet from its source to its destination, primarily used in Linux. It is useful because it can be used by any user instead of needing superuser privileges.

Tracepath

Provides the user with IP, subnet mask, and default gateway information for each network adapter, primarily used in Windows. Adding /release can be used to release all connections and renew all adapters.

Ipconfig

Used to configure kernel network interfaces, primarily used in Linux. It is implemented at the time of booting to configure the necessary interfaces. Once the interfaces are configured, it is used for debugging or tuning the system.

Ifconfig

Displays the IP to physical (MAC) address mappings for hosts in the ARP cache, used for adding, removing, or modifying entries. The hosts need to be on the local network, as these addresses are discovered by broadcasting to everyone on the network and noting the reply from the owner; broadcast traffic is not allowed through a router so that the system will maintain the MAC address of the router.

ARP

Displays information about active ports and their state, useful in troubleshooting and capacity management. Adding -r displays routing information for network adapters. It is available in Windows, MacOS, and Linux.

Netstat

Displays DNS information and troubleshoots DNS problems, useful in displaying names to IP address mappings.

Nslookup

Queries DNS name servers, helpful in troubleshooting DNS problems, and displays answers from the query. It is a replacement for nslookup.

Dig

Is a command that looks up who owns a domain or block of IP addresses on the internet, including name, email address, and physical address, primarily used in Linux. However, there are many privacy options that hide this information from being returned

Whois

Displays the current route tables on a host, used to add or remove routes. This is used by the local host to determine where to send traffic (0.0.0.0 means the default gateway, where the router sends things if it is not otherwise defined in the routing table).

Route

Securely copies files between servers leveraging SSH for authentication and encryption.

SCP

Copies files from one host to another host, data is unencrypted. If encryption is needed, it uses SSL/TLS (Secure Sockets Layer, replaced by Transport Layer Security; the same encryption used in https). Transfer uses TCP (transmission control protocol) for reliability and is often used on the internet and other wide-area networks, where errors may be more common.

FTP

Transfers files between client and server using UDP, usually used on reliable (local) networks.

TFTP

Displays information about a user or users on a remote system, including things such as last log-in time and username, primarily used in Linux.

Finger

Scans networks to find hosts and open ports, commonly used to determine what is deployed on a network for vulnerability analysis, security scans, and related activities. It is not native to either Linux or Windows but can be downloaded for free and used with both.

Nmap

The command traceroute is used for

Linux systems

The command tracert is used for

Windows systems.

Command that displays TCP/IP packets and other network packets that are being transmitted over the network system. It is a form of protocol analyzer (sometimes called a sniffer) and is designed to show the contents of network packets in human-readable form for troubleshooting, security analysis, etc. It is not native to either Linux or Windows but can be downloaded for free and used with both.

tcpdump

Command(s) that allow a user to manage accounts and devices remotely. The main difference between the two is that one is encrypted, and thus all data is secure from eavesdropping, while the other is unencrypted.

telnet/ssh

A network centered around a person and their devices, allowing for communication between devices such as computers, smartphones, and speakers using Bluetooth in the case of wireless connections or USB in the case of wired connections.

Personal Area Network (PAN)

A wireless technology used for short-range communication between devices in a PAN.

Bluetooth

A wired connection used for communication between devices in a PAN.

USB

The ability of devices to work together seamlessly, often seen in Apple products through their iCloud integration.

Integration

When a mobile phone acts as a gateway for other devices to connect to the internet.

Wi-Fi hotspot

A network consisting of computers connected within a limited area, often using Ethernet or Wi-Fi. or both.

Local Area Network (LAN)

A wired connection used for communication between devices in a LAN.

Ethernet

A set of protocols used for communication on LANs, allowing for the transfer of data between devices.

TCP/IP

A wireless technology used for communication between devices in a LAN.

Wi-Fi

The area within which devices can connect to a LAN, often determined by the range of the Wi-Fi signal.

Coverage area

A LAN with wireless connectivity, allowing devices to connect and communicate via Wi-Fi.

Wireless Local Area Network (WLAN)

A wireless technology used for communication between devices in a WLAN.

Wi-Fi

A point of entry or access to the internet for devices connected to a WLAN.

Gateway

A service that allows guests to connect to a WLAN and use the network and internet.

Hotspot service

The ability for users and devices to move freely within the coverage area of a WLAN.

Mobility

A network dedicated to storage devices, allowing servers to access devices like tape libraries and disk arrays.

Storage Area Network (SAN)

Disturbance or disruption caused by other network traffic, which SANs aim to reduce during data transfer.

Interference

A high-speed network technology often used in SANs for storage device communication.

Fibre Channel

The process of moving data from one device or storage system to another within a SAN.

Data transfer

Provides networking of multiple LANs across a limited area. Each LAN would typically be constrained to a single building (or even just a part of a building), and this would link them together in much the same way that a WAN does but over a smaller geographic area. It typically connects LANs owned by a single company, university, government agency, etc.

Campus area network (CAN)