IT Essentials - Chapter 5: Networking Concepts

Cellular Generations

- 1G/2G: The first generation (1G) of cell phones were analog voice calls only. -- 2G introduced digital voice, conference calls, and caller ID. -- Speed: less than 9.6 Kb/s. - 2.5G: 2.5G supports web browsing, short audio and video clips, games, and downloads of applications and ring tones. Speed: 9.6 Kb/s to 237 Kb/s. - 3G: 3G supports full-motion video, streaming music, 3D gaming, and faster web browsing. Speed: 144 Kb/s to 2 Mb/s. - 3.5G: 3.5G supports high-quality streaming video, high-quality video conferencing, and Voice over IP (VoIP). -- VoIP is a technology that applies internet addressing to voice data. -- Speed: 400 Kb/s to 16 Mb/s. - 4G: 4G supports IP-based voice, gaming services, high-quality streamed multimedia, and Internet Protocol version 6 (IPv6). -- IPv6 is the newest version of internet addressing. -- No cell phone carriers could meet the 4G speed standards when first announced in 2008. -- Speed: 5.8 Mb/s to 672 Mb/s. - LTE: Long Term Evolution (LTE) is a designation for a 4G technology that meets the 4G speed standards. -- An advanced version of LTE significantly improves the speeds while the user is moving at high speeds, such as in a car on the highway. -- Speed: 50 Mb/s to 100 Mb/s when mobile, and up to 1 Gb/s when stationary. - 5G: The 5G standard was ratified in June 2018 and is currently being implemented in select markets. -- 5G supports a wide variety of applications including augmented reality (AR), virtual reality (VR), smart homes, smart cars, and any scenario where data transfer occurs between devices. -- Speed: 400 Mb/s to 3 Gb/s download; 500 Mb/s to 1.5 Gb/s upload. - 6G: 6G is currently in development. As of late 2022, no standard yet exists. -- 6G will support even faster speeds required for AR/VR applications, artificial intelligence (AI) applications, and instantaneous communications.

Bluetooth

- A Bluetooth device can connect up to seven other Bluetooth devices. - Described in the IEEE standard 802.15.1, Bluetooth devices operate in the 2.4 to 2.485 GHz radio frequency range and is typically used for (Personal Area Networks) PANs. - The Bluetooth standard incorporates Adaptive Frequency Hopping (AFH). -- AFH allows signals to "hop" around using different frequencies within the 2.4 to 2.485 GHz range, thereby reducing the chance of interference when multiple Bluetooth devices are present.

Crimper

- A crimper is used to attach connectors to wires. --- The crimper tool shown here can attach RJ-45 connectors to networking cables used for Ethernet and RJ-11 connectors to telephone cables used for land lines.

Unified Threat Management (UTM)

- A generic name for an all-in-one security appliance. - UTMs include all the functionality of an IDS/IPS as well as stateful firewall services. Stateful firewalls provide stateful packet filtering by using connection information maintained in a state table. - A stateful firewall tracks each connection by logging the source and destination addresses, as well as source and destination port numbers. - In addition to IDS/IPS and stateful firewall services, UTMs also typically provide additional security services such as: -- Zero Day protection -- Denial of Service (DoS) and Distributed Denial of Service (DDoS) protection -- Proxy filtering of applications -- Email filtering for spam and phishing attacks -- Antispyware -- Network access control -- VPN services - In the firewall market today, UTMs are now typically called next-generation firewalls. For example, the Cisco Adaptive Security Appliance in the figure offers the latest in next-generation firewall features.

DHCP Server

- A host needs IP address information before it can send data on the network. - Two important IP address services are Dynamic Host Configuration Protocol (DHCP) and Domain Name Service (DNS) -- DHCP is the service used by ISPs, network administrators, and wireless routers to automatically assign IP addressing information to hosts --- Dynamic Host Configuration Protocol (DHCP) works in a client/server mode, where DHCP clients request available IP configurations from a DHCP server. --- A DHCP server is configured with a scope (i.e., a pool or a range) of addresses that it can lease to requesting DHCP clients. ---- Note: The DHCP server can be a dedicated server or a router configured to provide DHCP services. ---- The DHCP scope should not include manually assigned or reserved IP addresses such as the default gateway address, switch management address, printer address, and more.

loopback adapter (loopback plug)

- A loopback adapter, also called a loopback plug, tests the basic functionality of computer ports. -- The adapter is specific to the port that you want to test. In networking, a loopback plug can be inserted in a computer NIC to test the send and receive functionality of the port.

Punch down Tool

- A punch down tool is used to terminate wire into termination blocks.

satellite

- A satellite connection does not require a phone line or cable, but uses a satellite dish for two-way communication. - The satellite dish transmits and receives signals to and from a satellite that relays these signals back to a service provider - Download speeds can reach up to 10Mb/s or more, while upload speed ranges about 1/10th of download speeds. --- It takes time for the signal from the satellite dish to relay to your ISP through the satellite orbiting the Earth. --- Due to this latency, it is difficult to use time-sensitive applications, such as video gaming, Voice over Internet Protocol (VoIP), and video conferencing. - A new type of satellite service has far more satellites orbiting the Earth in low Earth orbit (LEO). -- The service can support up to approximately 100 Mbps with much lower latency than standard satellite, between 100 and 200 ms. -- The satellite dish contains a motor so that it can realign with the satellites because they move relative to the surface of the Earth.

Lucent Connector (LC) Simplex Connectors

- A smaller version of the fiber-optic SC connector. -- It is sometimes called a little or local connector and is quickly growing in popularity due to its smaller size.

Authentication Server

- Access to network devices is typically controlled through authentication, authorization, and accounting services. -- Referred to as AAA or "triple A", these services provide the primary framework to set up access control on a network device. --- AAA is a way to control who is permitted to access a network (authenticate), --- what they can do while they are there (authorize), --- and track what actions they perform while accessing the network (accounting).

Client - Server Roles

- All computers connected to a network that participate directly in network communication are classified as hosts. -- Hosts are also called end devices. -- Hosts on networks perform a certain role. Some of these hosts perform security tasks, while others provide web services. -- There are also many legacy or embedded systems that perform specific tasks such as file or print services. --- Hosts that provide services are called servers. --- Hosts that use these services are called clients. - Each service requires separate server software. For example, a server requires web server software in order to provide web services to the network. -- A computer with server software can provide services simultaneously to one or many clients. -- Additionally, a single computer can run multiple types of server software. --- In a home or small business, it may be necessary for one computer to act as a file server, a web server, and an email server. -- File Client and Server - The File Server stores corporate and user files in a central location. The client devices access these files with client software such as Windows Explorer. -- Web Client and Server - The Web Server runs web server software and clients use their browser software, such as Chrome or FireFox, to access web pages on the server. -- Email Client and Server - The Email Server runs email server software and clients use their mail client software, such as Microsoft Outlook, to access email on the server.

Firewalls

- An integrated router typically contains a switch, a router, and a firewall. - Firewalls protect data and equipment on a network from unauthorized access. -- A firewall resides between two or more networks. It does not use the resources of the computers it is protecting, so there is no impact on processing performance. - Firewalls use various techniques for determining what is permitted or denied access to a network segment, such as an Access Control List (ACL). -- This list is a file that the router uses which contains rules about data traffic between networks. - Note: On a secure network, if computer performance is not an issue, enable the internal operating system firewall for additional security. -- For example, in Windows 10 the firewall is called Windows Defender Firewall. -- Some applications might not operate properly unless the firewall is configured correctly for them.

Analog Telephone

- Analog telephone internet access can transmit data over standard voice telephone lines. -This type of service uses an analog modem to place a telephone call to another modem at a remote site. - This method of connection is known as Dialup.

HTTP Protocol Step 3

- As shown in the final figure, the browser interprets the HyperText Markup Language (HTML) code and formats the page for the browser window.

Switches

- Bridges and hubs are now considered legacy devices because of the benefits and low cost of switches. - a switch microsegments a LAN. -- Microsegmenting means that switches filter and segment network traffic by sending data only to the device to which it is sent. -- This provides higher dedicated bandwidth to each device on the network. -- When PC-A sends a job to the printer, only the printer receives the traffic. - Both switches and legacy bridges perform microsegmentation, however, switches perform this filtering and forwarding operation in hardware, and also include additional features. Switch Operation: As devices send data, switches enter the device's MAC address into a switching table that records the MAC address for each device connected to the switch, and records which switch port can be used to reach a device with a given MAC address. - When traffic arrives that is destined for a particular MAC address, the switch uses the switching table to determine which port to use to reach the MAC address. -- The traffic is forwarded out the port to the destination. --- By sending traffic out of only one port to the destination, other ports are not affected. Managed and Unmanaged Switches: In larger networks, network administrators typically install managed switches. - Managed switches come with additional features that the network administrator can configure to improve the functionality and security of the network. -- For example, a managed switch can be configured with VLANs and port security. - In a home or small business network, you probably do not need the added complexity and expense of a managed switch. -- Instead, you might consider installing an unmanaged switch. -- These switches typically have no management interface. - You simply plug them into the network and attach network devices to benefit from a switch microsegmentation features.

Bridge

- Bridges were introduced to divide LANs into segments. -- Bridges keep a record of all the devices on each segment. -- A bridge can then filter network traffic between LAN segments. -- This helps reduce the amount of traffic between devices. -- For example, in the next figure, if PC-A needs to send a job to the printer, the traffic will not be forward to Segment 2. However, the server will also receive this print job traffic.

Broadband

- Broadband uses different frequencies to send multiple signals over the same medium. - For example, the coaxial cables used to bring cable television to your home can carry computer network transmissions at the same time as hundreds of TV channels. - Your cell phone can receive voice calls while also using a web browser. - Some common broadband network connections include cable, digital subscriber line (DSL), ISDN, satellite, and cellular.

Cellular

- Cell phone technology relies on cell towers distributed throughout the user's coverage area to provide seamless access to cell phone services and the internet. - With the advent of the third-generation (3G) of cellular technology, smartphones could access the internet. - According to the Pew Research Center, in 2018 20% of adults in the United States do not use broadband at home (28% for adults 18-29).

Patch Panel

- Commonly used as a place to collect incoming cable runs from the various networking devices throughout a facility, as shown in the figure. - It provides a connection point between PCs and the switches or routers. - A patch panel can be unpowered or powered. - A powered patch panel can regenerate weak signals before sending them on to the next device.

Multimode Fiber (MMF)

- Consists of a larger core and uses LED emitters to send light pulses. -- Specifically, light from an LED enters the multimode fiber at different angles, as shown in the next figure. - Popular in LANs because they can be powered by low-cost LEDs. -- It provides bandwidth up to 10 Gb/s over link lengths of up to 550 meters.

Single-mode Fiber (SMF)

- Consists of a very small core and uses laser technology to send a single ray of light, as shown in the figure. - Popular in long-distance situations spanning hundreds of kilometers, such as those required in long haul telephony and cable TV applications.

DNS Server

- DNS is the method computers use to translate domain names into IP addresses. -- On the internet, domain names, such as http://www.cisco.com, are much easier for people to remember than 198.133.219.25, which is the actual numeric IP address for this server. -If Cisco decides to change the numeric IP address of www.cisco.com, it is transparent to the user because the domain name remains the same. -- The new address is simply linked to the existing domain name and connectivity is maintained.

SPAM Management

- DNS service is commonly abused by threat actors to assist in their SPAM email campaigns. -- For this reason, DNS servers now implement the following anti-spam security features using TXT resource records. --- Sender Policy Framework. (SPF) --- DomainKeys Identified Mail (DKIM) --- Domain-based Message Authentication, Reporting, and Conformance. (DMARC)

Mail Server

- Email is a store-and-forward method of sending, storing, and retrieving electronic messages across a network. -- Email messages are stored in databases on mail servers. - Email clients communicate with mail servers to send and receive email. -- Mail servers communicate with other mail servers to transport messages from one domain to another. - An email client does not communicate directly with another email client when sending email. Instead, both clients rely on the mail server to transport messages. - Email supports three separate protocols for operation: -- Simple Mail Transfer Protocol (SMTP), -- Post Office Protocol (POP), and -- Internet Message Access Protocol (IMAP). - The application layer process that sends mail uses SMTP. - A client retrieves email using one of the two application layer protocols: --POP or IMAP.

Fiber

- Fiber optic cables are made of glass or plastic and use light to transmit data. - have a very high bandwidth, which enables them to carry large amounts of data. - At some point in your connection to the internet, your data will cross a fiber network. -- Fiber is used in backbone networks, large enterprise environments and large data centers. -- The Internet backbone consists of many networks owned by numerous companies. --- Optical fiber trunk lines (the main core of the internet backbone) consist of many fiber cables bundled to increase capacity, or bandwidth. - Older copper cabling infrastructures closer to home and businesses are increasingly being replaced with fiber. -- For example, in the figure, the cable connection includes a hybrid fiber coaxial (HFC) network in which fiber is used in the last mile to the user's home. --- At the user's home, the network switches back to copper coaxial cable. This is known as Fiber to the Curb (FTTC) ---- Fiber to the premises (FTTP) brings the fiber to the customer's building. ---- A splitter in the street cabinet has an optical line terminal (OLT). The OLT has connections for each customer being supplied in the area. ---- The building is connected to the optical network terminal (ONT) inside the customer's building. ---- The optical signals are converted to electrical signals and connect to a router using a standard Ethernet patch cord.

Repeaters

- In early days of networking, solutions like using repeaters, hubs, and bridges were created to add more devices to the network. - Repeater: Regenerating weak signals is the primary purpose of a repeater, as shown in the figure. -- Repeaters are also called extenders because they extend the distance a signal can travel. - In today's networks, repeaters are most often used to regenerate signals in fiber-optic cables. -- -- Also, every networking device that receives and sends data regenerates the signal.

Legacy Systems

- Legacy systems are inherently vulnerable to security breaches because they cannot be upgraded or patched. -- One solution to alleviate some of the security risk is to air gap these systems. --- Air gapping is the process of physically isolating legacy systems from other networks and particularly the internet.

Syslog Server

- Many networking devices support syslog, including routers, switches, application servers, firewalls, and other network appliances. - The syslog protocol allows networking devices to send their system messages across the network to syslog servers. - The syslog logging service provides three primary functions: -- The ability to gather logging information for monitoring and troubleshooting -- The ability to select the type of logging information that is captured -- The ability to specify the destinations of captured syslog messages

Power over Ethernet (PoE)

- Method for powering devices that do not have a battery or access to a power outlet. - For example, a PoE switch, such as the one shown in the figure, transfers small amounts of DC current over an Ethernet cable, along with the data, to power PoE devices. - Low voltage devices that support PoE, such as wireless access points, surveillance video devices, and IP phones, can be powered from remote locations. - Devices that support PoE can receive power over an Ethernet connection at distances up to 330 ft (100 m) away. There are several IEEE standards for PoE: - 802.3af - Can supply up to 13 watts as 350mA at 48 volts. - 802.3at (PoE+) - Can supply up to 25 watts as 600 mA. - 802.3bt (PoE++ or 4PPoE) - Can supply 51 watts (Type 3) or 73 watts (Type 4)

Near Field Communication (NFC)

- NFC uses frequency 13.56 MHz and is a subset of the RFID standards. - NFC is designed to be a secure method to complete transactions. -- For example, a consumer pays for good or services by waving the phone near the payment system, as shown in the figure. --- Based on a unique ID, the payment is charged directly against a pre-paid account or bank account. -- NFC is also used in mass-transportation services, the public parking sector, and many more consumer areas.

Network

- Networks are systems that are formed by links

Twisted-Pair Category Ratings

- New or renovated office buildings often have some type of UTP cabling that connects every office. -- The distance limitation of UTP cabling used for data is 100 meters (330 feet). - Each category also comes in plenum rated versions, which are installed inside plenum areas of buildings. - A plenum is any area that is used for ventilation, such as the area between the ceiling and a dropped ceiling. -- Plenum-rated cables are made from a special plastic that retards fire and produces less smoke than other cable types.

Fiber-Optic Cables

- Optical fiber is composed of two kinds of glass (core and cladding) and a protective outer shield (jacket), as shown in the figure. - Because it uses light to transmit signals, fiber-optic cable is not affected by EMI or RFI. - All signals are converted to light pulses as they enter the cable, and converted back into electrical signals when they leave it. -- This means that fiber-optic cable can deliver signals that are clearer, can go farther, and have greater bandwidth than cable made of copper or other metals. - Although the optical fiber is very thin and susceptible to sharp bends, the properties of the core and cladding make it very strong. - Optical fiber is durable and is deployed in harsh environmental conditions in networks all around the world. - Components of Fiber-Optic Cable: -- Jacket: Typically a PVC jacket that protects the fiber against abrasion, moisture, and other contaminants. This outer jacket composition can vary depending on the cable usage. -- Strengthening Material: Surrounds the buffer, prevents the fiber cable from being stretched when it is being pulled. --- The material used is often the same material used to produce bulletproof vests. -- Buffer: Used to help shield the core and cladding from damage. -- Cladding: Made from slightly different chemicals than those used to create the core. --- It tends to act like a mirror by reflecting light back into the core of the fiber. ---This keeps light in the core as it travels down the fiber. -- Core: The core is actually the light transmission element at the center of the optical fiber. --- This core is typically silica or glass. Light pulses travel through the fiber core.

Intrusion Detection Systems (IDS)

- Passively monitor traffic on the network. - Stand-alone IDS systems have largely disappeared in favor of Intrusion Prevention Systems (IPSs). -- But the detection feature of an IDS is still part of any IPS implementation. -- The figure shows that an IDS-enabled device copies the traffic stream and analyzes the copied traffic rather than the actual forwarded packets. ----- Working offline, it compares the captured traffic stream with known malicious signatures, similar to software that checks for viruses.

PoE injector

- PoE devices like PoE switches, PoE injectors, IP cameras, Voice over IP (VoIP) phones, and wireless access points (WAPs) are the top five most popular devices - Power can also be inserted in the middle of a cable run using a PoE injector, as

Print Server

- Print servers enable multiple computer users to access a single printer. -- A print server has three functions: --- Provide client access to print resources. --- Administer print jobs by storing them in a queue until the print device is ready for them and then feeding or spooling the print information to the printer. --- Provide feedback to users.

Proxy Server

- Proxy servers have the authority to act as another computer. -- A popular use for proxy servers is to act as storage or cache for web pages that are frequently accessed by devices on the internal network. When any internal host sends an Hypertext Transfer Protocol (HTTP) GET request to www.cisco.com, the proxy server completes the following steps: 1. It intercepts the requests. 2. It checks to see if the website content has changed. 3. If not, the proxy server responds to host with the web page.

Radio Frequency ID (RFID)

- RFID uses the frequencies within the 125 MHz to 960 MHz range to uniquely identify items, such as in a shipping department - Active RFID tags that contain a battery can broadcast their ID up to 100 meters. - Passive RFID tags rely on the RFID reader to use radio waves to activate and read the tag. -- Passive RFID tags are typically used for close scanning but have a range of up to 25 meters.

Hub

- Receive data on one port and then send it out to all other ports. - A hub extends the reach of a network because it regenerates the electrical signal. - Hubs can also connect to another networking device, such as a switch or router, which connects to other sections of the network. - Hubs are legacy devices and should NOT be used in today's networks. Hubs do not segment network traffic. When one device sends traffic, the hub floods that traffic to all other devices connected to the hub. The devices are sharing the bandwidth.

Embedded Systems

- Related to legacy systems in that many legacy systems have embedded microchips. -- These embedded microchips are typically programmed to provide dedicated input and output instructions to a specialized device. -- Examples of embedded systems in the home are things such as a thermostat, refrigerator, cooking range, dishwasher, washing machine, video game consoles, and smart TVs. -- Embedded systems are increasingly becoming connected to the internet. -- Security should be top of mind when the technician recommends and installs embedded systems.

Spam Management

- Sender Policy Framework (SPF) - Domain Keys Identified Mail (DKIM) - Domain-based Message Authentication, Reporting, and Conformance (DMARC)

Load Balancer

- Some network servers can experience very heavy loads. -- Some examples include streaming media servers, web servers, and email servers. -- Often, multiple servers are providing one service in order to provide timely content. --- A load balancer can be used distribute the demand of requests. --- It is placed in front of the servers to ensure each server is being used as much as the others. ----- This prevents things like network timeouts and slow responses.

Network Taps

- Sometimes it is necessary to capture network traffic to analyze it. - This can often be done with software such as Wireshark. -- If this is not possible, a network tap can be used to capture the cable signals and send them to analyzing software. -- A network tap can be passive or active (powered). --- Passive test access point (TAP) - This type of TAP is a box with network ports to carry signals in and out. Inside, an inductor or optical splitter is used to copy the signal and send it out a monitor port. The monitor port receives all the traffic from the cable. --- Active TAP - This type of TAP regenerates the signal. Due to the complexity of gigabit signaling, a passive TAP is unable to be used. Also, some fiber links may become corrupt using an optical splitter, so an active TAP is used instead. - Network sniffing can also be completed using a special port on a network switch. This is known as a switched port analyzer (SPAN)/mirror port. A mirror receives a copy of the traffic that are addressed to a specific port or all other ports.

Subscriber Connector (SC) Connectors

- Sometimes referred to as square connector or standard connector. -- It is a widely adopted LAN and WAN connector that uses a push-pull mechanism to ensure positive insertion. This connector type is used with multimode and single-mode fiber.

Routers

- Switches and wireless APs forward data within a network segment. - Routers can have all the functionality of a switch or a wireless AP. -- However, routers connect networks, as shown in the figure. - Switches use MAC addresses to forward traffic within a single network. - Routers use IP addresses to forward traffic to other networks. -- In larger networks, routers connect to switches, which then connect to LANs, like the router on the right in the figure. The router serves as the gateway to outside networks. - The router on the left in the figure is also known as a multipurpose device or integrated router. -- It includes a switch and a wireless access point. --- For some networks, it is more convenient to purchase and configure one device that serves all your needs than to purchase a separate device for each function. -- This is especially true for the home or small office. Multipurpose devices may also include a modem for connecting to the internet.

Supervisory Control and Data Acquisition (SCADA)

- System is used in an industrial control system (ICS). -- This type of system provides automation for critical services such as national security, water treatment plants, or power suppliers. -- SCADA software runs on a computer to gather data from the devices used by the ICS. The SCADA manages the devices remotely typically through the use of satellite or cellular communications.

Application Port Numbers

- TCP and UDP use a source and destination port number to keep track of application conversations. - The source port number is associated with the originating application on the local device. - The destination port number is associated with the destination application on the remote device. --These are not physical ports. They are numbers that are used by TCP and UDP to identify the applications that should handle the data. -The source port number is dynamically generated by the sending device. -- This process allows multiple conversations to occur at the same time for the same application. -- For example, when you use a web browser, you can have more than one tab open at a time. The destination port number is 80 for regular web traffic or 443 for secure web traffic. --- These are called well-known port numbers because they are consistently used by most webservers on the Internet. - Source port numbers will be different for each tab opened. -- This is how your computer knows which browser tab to deliver the web content to.

File Server

- The File Transfer Protocol (FTP) provides the ability to transfer files between a client and a server. - An FTP client is an application that runs on a computer that is used to push and pull files from a server running FTP as a service. - As the figure illustrates, to successfully transfer files, FTP requires two connections between the client and the server, one for commands and replies, the other for the actual file transfer. - FTP has many security weaknesses. Therefore, a more secure file transfer services should be used, such as one of the following: -- File Transfer Protocol Secure (FTPS) - An FTP client can request the file transfer session be encrypted. The file server can accept or deny the request. -- SSH File Transfer Protocol (SFTP) - As an extension to Secure Shell (SSH) protocol, SFTP can be used to establish a secure file transfer session. -- Secure Copy (SCP) - SCP also uses SSH to secure file transfers.

WLAN Protocals

- The Institute of Electrical and Electronic Engineers' (IEEE) standards for Wi-Fi as specified in the 802.11 collective group of standards that specify the radio frequencies, speeds, and other capabilities for WLANs - The 802.11a, 802.11b, and 802.11g standards should be considered legacy. - New WLANs should implement 802.11ax (Wi-Fi 6) devices. Existing WLAN implementations should upgrade to 802.11ax (Wi-Fi 6) when purchasing new devices.

HTTP Protocal Step 1

- The browser then checks with a Domain Name Server (DNS) to convert www.cisco.com into a numeric address, which it uses to connect to the server. -- Using HTTP requirements, the browser sends a GET request to the server and asks for the index.html file, as shown in the next figure.

DHCP Lease

- The client must contact the DHCP server periodically to extend the lease. - This lease mechanism ensures that moved or power-off clients do not keep addresses that they no longer need. - When a lease expires, the DHCP server returns the address to the pool where it can be reallocated as necessary.

Fiber-Optic Connectors

- The main differences among the types of connectors are dimensions and methods of coupling. -- Businesses decide on the types of connectors that will be used, based on their equipment. - For fiber standards with FX and SX in the name, light travels in one direction over optical fiber. -- Therefore, two fibers are required to support the full duplex operation. - Fiber-optic patch cables bundle together two optical fiber cables and terminate them with a pair of standard single fiber connectors. - Some fiber connectors accept both the transmitting and receiving fibers in a single connector known as a duplex connector, as shown in the Duplex Multimode LC Connector in the figure. - For fiber standards with BX in the name, light travels in both directions on a single strand of fiber. -- It does this through a process called Wave Division Multiplexing (WDM). WDM is a technology that separates the transmit and receive signals inside the fiber.

Medium/Media

- The medium provides the channel over which the message travels from source to destination.

HTTP Protocol Step 2

- The server sends the HTML code for this web page back to the client's browser, as shown in the next figure.

Twisted-Pair Wire Schemes

- There are two different patterns, or wiring schemes, called T568A and T568B. -- Each wiring scheme defines the pinout, or order of wire connections, on the end of the cable. -- Only the orange pair and green pair are reversed between T568A and T568B. - It is important that the same wiring scheme is used for every termination in that project. - If working on an existing network, use the wiring scheme that already exists.

Intermediary Devices

- These intermediary devices ensure that data flows from one host device to another host device. The most common intermediary devices are shown in the figure: Switch - connects multiple devices to the network. Router - forwards traffic between networks. Wireless router - connects multiple wireless devices to the network and may include a switch to connect wired hosts. Access point (AP) - connects to a wireless router and is used to extend the reach of a wireless network. Modem - connects a home or small office to the Internet.

Internet Protocal Suite (TCP/IP Protocol Suite)

- This protocol suite includes all the protocols used in various aspects of end-to-end network communications, including addressing, routing, and reliability. - The TCP/IP protocol suite is also a conceptual model that classifies and organizes the various protocols into four different layers: Network Access, Internet, Transport, and Application. -- The two protocols that operate at the transport layer are Transmission Control Protocol (TCP) and User Datagram Protocol (UDP), as shown in the figure. -- These protocols determine how the data will be delivered, reliably or unreliably. It is up to the network application to choose. - TCP is responsible for tracking all the network connections between a user's device and multiple destinations. - The Internet Protocol (IP) is responsible for adding addressing so that data can be routed to the intended destination.

Twisted Pair Cables

- Twisted-pair is a type of copper cabling used for telephone communications and most Ethernet networks. -The pair is twisted to provide protection against crosstalk, which is the noise generated by adjacent pairs of wires in the cable. - Unshielded twisted-pair (UTP) cabling is the most common variety of twisted-pair cabling. - UTP cable consists of four pairs of color-coded wires that have been twisted together and then encased in a flexible plastic sheath that protects from minor physical damage. - UTP does not protect against electromagnetic interference (EMI) or radio frequency interference (RFI). -- EMI and RFI can be caused by a variety of sources including electric motors and fluorescent lights.

Coaxial Cables

- Used by both cable television companies and satellite communication systems. - Coaxial cable is enclosed in a sheath or jacket and can be terminated with a variety of connectors. - Coaxial cable (or coax) carries data in the form of electrical signals. - It provides improved shielding compared to unshielded twisted-pair (UTP), so it has a higher signal-to-noise ratio allowing it to carry more data. - However, twisted-pair cabling has replaced coax in LANs because, when compared to UTP, coax is physically harder to install, more expensive, and harder to troubleshoot.

Web Server

- Web resources are provided by a web server. -- The host accesses the web resources using the Hypertext Transfer Protocol (HTTP) or the secure HTTP (HTTPS). -- HTTP is a set of rules for exchanging text, graphic images, sound, and video on the World Wide Web. -- HTTPS adds encryption and authentication services using Secure Sockets Layer (SSL) protocol or the newer Transport Layer Security (TLS) protocol. -- HTTP operates on port 80. HTTPS operates on port 443. - Browser interprets 3 parts of URL: -- 1. http (the protocol or scheme) -- 2. www.cisco.com (the server name) -- 3. index.html (the specific filename requested)

DNS Records

- When a client does not know the IP address of a web domain or email domain name, it sends a Domain Name System (DNS) query to the DNS server identified in its Internet Protocol (IP) configuration. - The DNS query may ask the DNS server: -- What is the IPv4 address for the xyz.com domain name? -- What is the IPv6 address for the xyz.com domain name? -- What is the IP address for emails forwarded to the @xyz.com domain name? -- Do you have additional information about the @xyz.com email domain? - To answer these types of questions, a DNS server keeps a list of domain names and IP addresses information in resource records (RRs). -- This list of RRs is stored on a DNS server in a DNS zone database. - When the server receives a DNS name query, it looks in its zone database for a matching RR to resolve the query. -- If it finds a match, it replies to the requesting host with the RR information. -- If there is no match, then it queries a higher-level DNS server. Some of the Types of DNS RRs are on image.

Z-Wave

- Z-Wave technology is a proprietary standard that is now owned by Silicon Labs. - However, a public version of the interoperability layer of Z-Wave was open sourced in 2016. -- These open source Z-Wave standards include Z-Wave's S2 security, Z/IP for transporting Z-Wave signals over IP networks, and Z-Ware middleware. - Z-Wave operates within a variety of frequencies based on the country from 865.2 MHz in India to 922 - 926 MHz in Japan. Z-Wave operates at 908.42 MHz in the North America. Z-Wave can transmit data up to 100 meters but has a slower data rate than Zigbee at 9.6-100 kb/s. Z-Wave can support up to 232 devices in one wireless mesh netwo- However, a public version of the interoperability layer of Z-Wave was open sourced in 2016. -- These open source Z-Wave standards include Z-Wave's S2 security, Z/IP for transporting Z-Wave signals over IP networks, and Z-Ware middleware.

Zigbee

- Zigbee and Z-Wave are two smart home standards that allow users to connect multiple devices in a wireless mesh network. -- Typically, the devices are then managed from a smartphone app - Zigbee uses low-power digital radios based on the IEEE 802.15.4 wireless standard for low-rate wireless personal area networks (LR-WPANs) that is meant to be used by low-cost, low-speed devices. - Zigbee operates within frequencies from 868 MHz to 2.4 GHz and is limited to 10 to 20 meters. - Zigbee has a data rate from 40-250 kb/s and can support approximately 65,000 devices. -The ZigBee specification relies on a main device called a ZigBee Coordinator. -- Tasked with managing all ZigBee client devices, the ZigBee Coordinator is responsible for the creation and maintenance of the ZigBee network. - Although Zigbee is an open standard, software developers must be a paid member of the Zigbee Alliance to use and contribute to the standard.

Local Area Network (LAN)

- a network that connects devices using wire cables in a small geographical area. - distinguishing characteristic for LANs today is that they are typically owned by an individual, such as in a home or small business, or wholly managed by an IT department, such as in a school or corporation.

Metropolitan Area Network (MAN)

- a network that spans across a large campus or a city. The network consists of various buildings connected through wireless or fiber optic media

Virtual LANs (VLANs)

- allow an administrator to segment the ports on a single switch as if it were multiple switches. --provides more efficient forwarding of data by isolating traffic to only those ports where it is required. - VLANs also allow end devices to be grouped together for administrative purposes. - A group of devices within a VLAN communicate as if each device was attached to the same switch. - VLANs are based on logical connections, instead of physical connections. - An administrator can segment VLANs based on factors such as function, team, or application, without regard for the physical location of the users or devices. - VLANs help reduce excessive broadcast traffic and implement access and security policies between groups of users.

Line of Sight Wireless Internet Service

- always-on service that uses radio signals for transmitting internet access. - Radio signals are sent from a tower to the receiver that the customer connects to a computer or network device. -- A clear path between the transmission tower and customer is required. -- The tower may connect to other towers or directly to an internet backbone connection. -- The distance the radio signal can travel and still be strong enough to provide a clear signal depends on the frequency of the signal. --- Lower frequency of 900 MHz can travel up to 40 miles (65 km) --- higher frequency of 5.7 GHz can only travel 2 miles (3 km). - Extreme weather conditions, trees, and tall buildings can affect signal strength and performance.

IPS

- builds upon IDS technology. - However, an IPS device is implemented in inline mode. -- This means that all inbound and outbound traffic must flow through it for processing. -- As shown in the next figure, an IPS does not allow packets to enter the target system without first being analyzed. - The biggest difference between IDS and IPS is that an IPS responds immediately and does not allow any malicious traffic to pass, whereas an IDS allows malicious traffic to pass before it is addressed. -- However, a poorly configured IPS can negatively affect the flow of traffic in the network.

Mobile Hotspot and Tethering

- cell phones provide the ability to connect other devices known as "Tethering." - can be made using Wi-Fi, Bluetooth, or by using a USB cable. - Once a device is connected, it is able to use the phone's cellular connection to access the Internet. - When a cellular phone allows Wi-Fi devices to connect and use the mobile data network, it is called a mobile hotspot.

Wide Area Network (WAN)

- connects multiple networks that are in geographically separated locations. -Individuals and organizations contract for WAN access from a service provider. - Your service provider for your home or mobile device connects you to the largest WAN, the internet. www.youtube.com/watch?v=5OoX_cRLaNM

Shielded twisted-pair (STP)

- designed to provide better protection against EMI and RFI. - As shown in the next figure, each twisted-pair is wrapped in a foil shield. - The four pairs are then wrapped together in a metallic braid or foil. - Compared to UTP cable, STP cable is significantly more expensive and difficult to install. - To gain the full benefit of the shielding, STP cables are terminated with special shielded STP RJ-45 data connectors (not shown). - If the cable is improperly grounded, the shield may act as an antenna and pick up unwanted signals. - Both UTP and STP cables are terminated with an RJ-45 connector and plug into RJ-45 sockets

Cloud-based Network Controller

- device in the cloud that allows network administrators to manage network devices. -- For example, a medium sized company with multiple locations might have hundreds of wireless APs. Managing these devices can be cumbersome without using some type of controller. --- For example, Cisco Meraki provides cloud-based networking that centralizes the management, visibility, and control of all Meraki devices into one dashboard interface, as shown in the figure. --- The network administrator is able to manage the wireless devices in multiple locations with the click of a mouse button.

Wi-Fi Analyzer

- mobile tools for auditing and troubleshooting wireless networks. - Technicians can see all available wireless networks in a given area, determine signal strengths, and position access points to adjust wireless coverage. - Some Wi-Fi analyzers can help troubleshoot a wireless network by detecting misconfigurations, access point failures, and radio frequency interference (RFI) problems.

Personal Area Network (PAN)

- network that connects devices, such as mice, keyboards, printers, smartphones, and tablets within the range of an individual person. -- most often connected with Bluetooth technology.

Wireless Access Point (APs)

- provide network access to wireless devices, such as laptops and tablets. - The wireless AP uses radio waves to communicate with the wireless Network Interface Card (NIC) in the devices and other wireless access points. - An access point has a limited range of coverage. - Large networks require several access points to provide adequate wireless coverage. - A wireless access point provides connectivity only to the network, while a wireless router provides additional features.

network interface card (NIC)

- provides the physical connection to the network at the PC or other end device. - there are different types of NICs. -- Ethernet NICs are used to connect to Ethernet networks and wireless NICs are used to connect to 802.11 wireless networks. -- Most NICs in desktop computers are integrated into the motherboard or connected to an expansion slot, and also available in USB for factor. -A NIC also performs the important function of addressing data with the NIC's media access control (MAC) address and sending the data out as bits on the network. -- NICs found on most computers today are gigabit Ethernet (1000 Mbps) capable.

Dial Up Connection

- requires either an internal modem installed in the computer or an external modem connected by USB. -The modem dial-up port is connected to a phone socket using an RJ-11 connector. - Once the modem is physically installed it must be connected to one of the computer's software COM ports. - The modem must also be configured with local dialing properties such as the prefix for an outside line and the area code. -The Set Up a Connection or Network Wizard is used to configure a link to the ISP server. - Connecting to the internet has evolved from analog telephone to broadband:

Endpoint Management Server

- responsible for monitoring all the end devices in your network including desktops, laptops, servers, tablets, and any device connected to your network. - An endpoint management server can restrict an end device's connection to the network if the device does not meet certain predetermined requirements. -- For example, it can verify the devices has the latest operating system and anti-virus updates. --- Cisco's Digital Network Architecture (DNA) Center is an example of a solution that provides endpoint management. --- However, Cisco DNA is much more. It is a comprehensive management solution for managing all devices connected to the network so that the network administrator can optimize network performance to deliver the best possible user and application experience. --- The tools for managing the network are available for the Cisco DNA Center interface, as shown in the figure.

Transmission Control Protocol (TCP)

- the data will be delivered reliably with guaranteed delivery and assembled in the proper order. - TCP adds some "overhead," which means there will be some additional delay - For example, the Network Application HTTP uses TCP to make sure all the data is delivered reliably. -- EX: the user types in the URL www.MyBank.example. TCP is used to transport the information reliably between the user's computer and the web server. The web server, also using TCP, sends the requested data, the webpage, in separate segments. -- Each segment includes a sequence number so the receiver knows if anything is missing and so it can assemble it in the proper order. - To summarize, the application such as those that perform file transfers, downloading webpages and email, all use the reliable Transport protocol TCP, - With TCP, there are three basic operations of reliability: -- Numbering and tracking data segments transmitted to a specific device from a specific application -- Acknowledging received data Retransmitting any unacknowledged data after a certain period of time

Cable

- use a modem to connect to the internet through an Internet Service Provider (ISP) - A cable modem connects the user's network to a cable service provider. - A cable internet connection does not use telephone lines.. - Cable uses coaxial cable lines originally designed to carry cable television. - A cable modem connects your computer to the cable company - You can plug your computer directly into the cable modem. -However, connecting a routing device to the modem allows multiple computers to share the connection to the internet.

Digital Subscriber Line (DSL)

- use a modem to connect to the internet through an Internet Service Provider (ISP). Requires a phone line. - A DSL modem connects a user's network directly to the digital infrastructure of the phone company. - DSL is an always-on service, which means that there is no need to dial up each time you want to connect to the internet. - Voice and data signals are carried on different frequencies on the copper telephone wires. - A filter prevents DSL signals from interfering with phone signals. Very high-speed DSL (VDSL) attains much higher bit rates than DSL. -- A symmetric link can carry as much as 26 Mbps in both directions -- an asymmetric link can carry as much as 52 Mbps download and 6 Mbps upload. -- VDSL2 can carry as much as 100 Mbps in both directions.

Virtual Private Network (VPN)

- used to securely connect to another network over an insecure network such as the internet - most common type of VPN is used by teleworkers to access a corporate private network. - In the figure, the fat links between Teleworker 1 and the router at the Company Headquarters represent a VPN connection.

Ethernet over Power/Powerline Networking

- uses existing electrical wiring to connect devices, as shown in the next figure. - The concept of "no new wires" means the ability to connect a device to the network wherever there is an electrical outlet. -- This saves the cost of installing data cables and without any additional cost to the electrical bill. -- --- Using the same wiring that delivers electricity, powerline networking sends information by sending data on certain frequencies. - Figure 3 is of a powerline networking adapter plugged into an electrical outlet.

Wireless Mess Network (WMN)

- uses multiple access points to extend the WLAN. - The topology shows a wireless router. The two wireless APs extend the reach of the WLAN within the home. - business and municipalities can use WMNs to quickly add new areas of coverage

Integrated Services Digital Network (ISDN)

- uses multiple channels and can carry different types of services --therefore, it is considered a type of broadband. - ISDN is a standard that uses multiple channels to send voice, video, and data over normal telephone wires. - ISDN bandwidth is larger than traditional dialup.'

User Datagram Protocol (UDP)

- when the data needs to be delivered as quickly as possible, with some tolerance for loss of data. - Network applications such as those used for sending voice and real-time video can sacrifice some data loss in order for the data to be delivered as quickly as possible. - UDP does not include any functions for reliability, such as there are no sequence numbers in the UDP segments - UDP provides the basic functions for delivering data segments between the appropriate applications, with very little overhead and data checking. - In the context of networking, best-effort delivery is referred to as "unreliable" because there is no acknowledgment that the data is received at the destination. - UDP is used for applications such as real-time video and voice where speed is more important than reliability.

Wireless LAN (WLAN)

- wirelessly connects users and devices in a small geographical area instead of using a wired connection. - WLAN uses radio waves to transmit data between wireless devices.

DHCP Reservation

-It is also possible to ensure that some hosts, such as servers and printers, are always assigned the same IP address when they connect. -- To do so, a DHCP server is configured with a reserved list of IP addresses based on the requesting DHCP client's MAC address. --- Therefore, when a host sends a DHCPDISCOVER message, the DHCP server looks in its DHCP reserved address list for a matching MAC address. --- If it finds a match, then it sends a DHCPOFFER with the reserved IP address.

DHCP Four-Step Process to Obtain a Lease

1. The DHCP client broadcasts a DHCPDISCOVER message to request an IP configuration from a DHCP server. 2. The DHCP server chooses an available IP configuration from its configured scope, and sends a DHCPOFFER unicast message to the client Media Access Control (MAC) address. - The IP configuration can contain the IP address, subnet mask, default gateway, DNS servers, and the period of time (i.e., the lease) that the host can use the IP configuration. 3. The client then officially requests the IP configuration by sending a broadcast DHCPREQUEST message to the DHCP Server. 4. The server removes the IP configuration from its pool of available IP configurations and sends a unicast acknowledgement (DHCPACK) to the DHCP client to confirm that it can use the address until the lease expires. Note: DHCP messages are sent using UDP ports 67 (server) and UDP port 68 (clients). DHCP servers listen for client messages on UDP port 67 and DHCP clients listen for messages from servers on UDP port 68.The figure displays the DHCP process in Wireshark. - Once a client receives the DHCPACK from the server, it send out an ARP message to the provided IP address to make sure it is not already assigned on the network. -- ARP (address resolution protocol) is a network protocol to discover the MAC address of a device using an IP address. -- If there is no response to the ARP request, then the host can use the IP configuration. -- If the host receives an ARP reply, then it restarts the DHCP process to obtain a different IP configuration.

Cable Tester

A cable tester is used to check for wiring shorts, faults, or wires connected to the wrong pins.

straight-tip (ST) connector

One of the first connector types used. The connector locks securely with a "twist-on/twist-off" bayonet style mechanism.

Duplex Multimode LC Connectors

Similar to a LC simplex connector, but using a duplex connector.

Host device

The network devices that people are most familiar with are called end devices or host devices - end devices because they are at the end or edge of a network. - They are also called host devices because they typically host network applications, such as web browsers and email clients, that use the network to provide services to the user.

Tone Generator and Probe

The tone generator and probe is a two-part tool used to trace the remote end of a cable for testing and troubleshooting. -- The tone generator applies a tone to the wire to be tested. -- On the remote end, the probe is used to identify the test wire. -- When the probe is in near proximity to the cable to which the toner is attached, the tone can be heard through a speaker in the probe.