2023/08/08

Computer Networking Essentials Week 3

Networking

Computer Networking Essentials Week 3

Computer Lab

Set IP address for a switch:
```
S1#(config)# interface vlan 1
S1(config-if)# ip address 192.168.1.1 255.255.255.0
S1(config-if)# no shutdown
S1(config-if)# exit
S1(config)#
```
- S1#(config)# interface vlan 1: This command is used to enter into the configuration mode for the interface, specifically VLAN 1 (Virtual Local Area Network 1). A VLAN is a network that logically segments a network on the basis of the function, project team, or application, regardless of the physical location of the users. VLANs allow for greater ease of network management and scalability.
- S1(config-if)# ip address 192.168.1.1 255.255.255.0: Once in the configuration mode for the interface, this command is used to assign the IP address 192.168.1.1 with the subnet mask 255.255.255.0 to VLAN 1. This effectively sets the network address for the VLAN.
- S1(config-if)# no shutdown: This command is used to activate the interface. By default, many interfaces on a network device are administratively down (or “shutdown”), meaning they are turned off. The “no shutdown” command turns them on (or makes them “up”). This command is essential for the interface to pass traffic.
- S1(config-if)# exit: This command is used to exit the interface configuration mode and go back to the global configuration mode. From here, you can select and configure other interfaces or aspects of the device.
Configure the VTY (Virtual Teletype/ Virtual terminal) line for the switch to allow remote access:
```
S1(config)# line vty 0 15
S1(config-line)# password cisco
S1(config-line)# login
S1(config-line)# logging synchronous
S1(config-line)# end
```
- S1(config)# line vty 0 15: This command is used to enter into line configuration mode for the Virtual Teletype (VTY) lines on the device. VTY lines are virtual interfaces that allow remote access to the device, such as through protocols like Telnet or SSH. The numbers 0 and 15 specify a range, so this command is accessing VTY lines 0 through 15. This means any configurations applied after this command will affect all of these 16 lines.
show run command: The command “S1# show run” is a shortened version of the command “S1# show running-config”. This is a command used in Cisco IOS (the operating system that runs on most Cisco networking devices) to display the device’s current running configuration.

When executed, this command shows the entire active configuration file, which contains all the configuration commands that are currently in effect. This includes interface configurations, routing protocols, access control lists, security settings, and any other settings that have been applied.

Here is a brief breakdown of what the command does:
- S1#: This is the prompt that appears in the command-line interface (CLI) of the Cisco device. The “#” symbol indicates that the user is in privileged EXEC mode, which is required to view the running configuration.
- show: This command is used to display information about the device’s operation and configuration.
- run: This is a shorthand version of “running-config”, which indicates that you want to view the current running configuration.
The running configuration is stored in the device’s RAM and can be changed at any time. It’s important to note that these changes are not permanent and will be lost if the device is restarted, unless they are saved to the startup configuration (stored in non-volatile memory) using the “copy running-config startup-config” command.

Physical Layer

Physical Layer Media: The Physical Layer is the first and lowest layer of the Open System Interconnection (OSI) Model. The main function of the Physical Layer is to transport raw bit streams from one device to another, typically across a physical medium such as a wire. This transport occurs via varied media types, including electrical signals through copper wire, light pulses through fiber-optic cables, and microwave signals for wireless communication. Let’s go into more detail about each:

Electrical Signals with Copper Wire:
- Copper cables are widely used in traditional telephone lines and Ethernet networks due to their cost-effectiveness and ease of installation.
- The most common types of copper cables are Coaxial Cable and Twisted Pair (which includes Unshielded Twisted Pair (UTP) and Shielded Twisted Pair (STP)).
- Information is sent over copper wires as electrical signals (voltage). Different voltage levels represent the binary data (1s and 0s) that constitute all network communication.
- However, copper wires are susceptible (very likely to be influenced, harmed or affected by something) to electrical interference (noise) and signal degradation over long distances.
Light Pulses with Fiber Optic Cable:
- Instead of using electricity to transmit data, fiber-optic cables use pulses of light.
- A fiber-optic cable consists of a bundle of glass threads, each of which can transmit messages modulated onto light waves. This makes it possible for fiber-optic cables to carry a significant amount of data over great distances.
- Fiber-optic cables are immune to electromagnetic interference and provide faster data rates (bandwidth) compared to traditional copper cables.
- They are primarily used in long-haul networks, where their high cost can be justified by their increased speed, capacity, and distance capabilities.
Microwave Signals with Wireless:
- Wireless technologies use the air or space as the medium to transmit signals in the form of electromagnetic or radio waves, often referred to as microwaves.
- Wireless communications can be via Radio Frequency (RF) communication, microwaves, Infrared (IR), or satellite. The use of these frequencies is regulated by international agreement to prevent interference.
- Wi-Fi and cellular networks are the most commonly recognized wireless technologies.
- The advantages of wireless communication include mobility and the elimination of physical cables. However, they are also subject to interference, security issues, and have distance limitations.
In conclusion, the choice of physical medium depends on factors such as the distance data needs to travel, the volume of data being sent, cost, and the environment in which it will be installed.
Several organizations governing the physical layer standards: Various organizations set the standards for the physical layer of the OSI (Open Systems Interconnection) model, which is the first and most fundamental layer concerned with the medium of transmission and the nature of the transmitted signal. These standards help ensure compatibility and interoperability between different devices and systems. Here are some of the key organizations:
- International Organization for Standardization (ISO): This is an independent, non-governmental international organization that develops standards to ensure the quality, safety, and efficiency of products, services, and systems. It covers a variety of sectors, including technology. The ISO, in collaboration with the International Electrotechnical Commission (IEC) and the International Telecommunication Union (ITU), developed the OSI model.
- Telecommunications Industry Association/Electronic Industries Association (TIA/EIA): These are American trade organizations that set standards for information and communication technologies. Their standards address a wide range of issues, including data transfer and physical layer interconnections.
- International Telecommunication Union (ITU): This is a specialized agency of the United Nations that is responsible for issues related to information and communication technologies. It coordinates the shared global use of the radio spectrum, promotes international cooperation in assigning satellite orbits, works to improve telecommunication infrastructure in the developing world, and assists in the development and coordination of worldwide technical standards.
- ITU-T (Telecommunication Standardization Sector): This is a sector of ITU that is responsible for coordinating standards for telecommunications on behalf of ITU.
- American National Standards Institute (ANSI): This is a private, non-profit organization that oversees the development of voluntary consensus standards for products, services, processes, systems, and personnel in the United States. It coordinates U.S. standards with international standards so that American products can be used worldwide.
- Institute of Electrical and Electronics Engineers (IEEE): This is a professional association for electronic engineering and electrical engineering. It is best known for developing standards for the computer and electronics industry. For example, the IEEE 802 standards for local area networks (LANs) and metropolitan area networks (MANs) are widely used.
These organizations work together in various ways to ensure that the standards are consistent and interoperable. Each of these organizations has its own scope and jurisdiction, but they often cooperate and share information to create standards that work worldwide.
Throughput and Goodput: Throughput and Goodput are essential network performance metrics that provide insight into the efficiency and effectiveness of data transfer over a network. They are specifically used to measure the rate of data transfer over a given period of time. However, they are not the same and measure different aspects of network performance.

Throughput is the measure of the transfer of bits across the network media over a given period of time. It’s a metric that reveals the amount of data that can pass through a network or a portion of the network per unit of time. However, this doesn’t mean that all the bits are useful data. Some bits could be part of network protocol overhead (headers, acknowledgments, etc.), retransmissions due to errors, or other non-payload elements.

Several factors can affect throughput, causing it to be less than the maximum bandwidth specified for a particular physical layer. These factors may include:
- Amount of traffic: High network traffic can cause congestion, reducing the actual throughput.
- Type of traffic: The data payload sizes and the need for acknowledgements or other aspects of the transport protocol can affect throughput.
- Latency: This is the delay caused by network devices or the propagation of signals. More latency can decrease throughput.
Goodput, on the other hand, is a more refined measure. It is the rate of successful message delivery over a communication channel. Essentially, goodput is the throughput minus all the “overhead” bits including those used for establishing sessions, acknowledgments, and encapsulation. This means it measures the rate at which useful data is transmitted, i.e., the actual payload of data minus all the protocol overhead.

In other words, while throughput gives an overall measure of how much data is getting through, goodput provides a measure of how efficiently the network is handling useful data transmission.
Copper Cabling:
Characteristics of Copper Media: Copper Media is widely used in the creation of networking cables due to its excellent electrical conductivity. Signals are transmitted over copper cables in the form of electrical pulses. However, as with any physical medium, it comes with its specific set of characteristics and limitations.
- Transmission: Copper media carries data in the form of electrical pulses. These pulses can be easily read by network devices, making copper media a convenient choice for data transmission.
- Attenuation: As signals travel over copper wires, they tend to deteriorate (to become worse) or weaken, a phenomenon known as attenuation. This is one of the primary limiting factors in the distance data can travel reliably over copper cabling. The longer the cable, the higher the signal loss.
- Distance Limitations: Due to the attenuation, copper media must adhere to strict distance limitations. For example, a standard Ethernet copper cable (Cat 5e) has a maximum length of 100 meters for a single run to ensure signal integrity.
- Electromagnetic Interference (EMI) / Radio Frequency Interference (RFI): Copper is susceptible (very likely to be influenced, harmed or affected by something) to interference from external electromagnetic fields, which can distort (to change the shape, appearance or sound of something so that it is strange or not clear) and corrupt the data signals being carried by the cable. To counteract (to do something to reduce or prevent the bad or harmful effects of something) this issue, copper cables are often wrapped in shielding, which helps reduce the effect of EMI and RFI.
- Crosstalk: Crosstalk is a disturbance caused by the electric or magnetic fields of a signal on one wire interfering with the signal in an adjacent wire. This can result in decreased network performance and possible data errors. To mitigate this, wires within copper cables are twisted into pairs. The twist rate (also called pitch) is varied for each pair to ensure that no two pairs have the same cross-section alignment for any considerable distance, which helps to cancel out the effects of crosstalk.
All of these characteristics play a crucial role in determining the use case, effectiveness, and efficiency of copper media in a network.

Copper Media:
Unshielded Twisted-Pair (UTP) cabling: Unshielded Twisted-Pair (UTP) cabling is the most common type of cabling used in Ethernet networks. Its popularity stems from its balance of performance, ease of installation, and cost.
- Properties of UTP Cabling: UTP cable is composed of pairs of wires twisted together, which helps to reduce signal interference, including Electromagnetic Interference (EMI) and Radio Frequency Interference (RFI). The twists help to ensure that each wire in the pair is equally exposed to any external interference, which allows the receiver to effectively subtract out this noise.
- UTP Cabling Standards: UTP cabling adheres to several standards, such as the TIA/EIA-568 standard which governs the manufacture and use of UTP cables. The IEEE has further categories, like Cat5, Cat5e, Cat6, and Cat6e, which denote different performance characteristics and capabilities of the cables. For example, Cat5e cables are designed for use in networks running at speeds up to 1 Gigabit per second, whereas Cat6 cables can be used in networks running at speeds up to 10 Gigabits per second.
- UTP Connectors (RJ45): UTP cables are typically terminated with RJ-45 connectors. RJ-45 is a standardized physical network interface for connecting telecommunications or data equipment.
- Types of UTP Cable: There are several types of UTP cables, which are used in different situations:
  - Rollover (console) cables are used to connect a computer terminal to a router’s console port.
  - Crossover cables are used to connect two devices of the same type, such as two computers or two switches.
  - Straight-through cables are used to connect devices of different types, such as a computer to a switch or a switch to a router.
- Cable Pinouts: Cable pinouts refer to the arrangement of wires in the cable and the RJ-45 connector. The TIA/EIA-568 standard specifies two different pinouts: T568A and T568B. The choice between them is generally a matter of preference, unless equipment requires a specific one.
- Color-Coded Wires: UTP cables consist of four pairs of color-coded wires. The color coding aids in the termination of the cable to the RJ-45 connector, helping to ensure that the correct wires are connected to the correct pins.
Shielded Twisted-Pair (STP) cable: Shielded Twisted-Pair (STP) cable is another commonly used form of network cabling that has several features that set it apart from its Unshielded Twisted-Pair (UTP) counterpart. Let’s go over these properties in a comprehensive way:
- Noise Protection: STP cables, as the name suggests, are shielded. This shielding provides an additional layer of protection against electromagnetic interference (EMI) and radio frequency interference (RFI), above and beyond the noise cancellation offered by the twisting of the pairs of wires. This makes STP a suitable choice in environments with higher levels of electrical noise or interference.
- Cost and Installation: Because of the additional shielding, STP cables are more expensive than UTP cables. They are also more difficult to install because they are heavier and less flexible than UTP cables. Additionally, the shielding needs to be grounded (In simpler terms, when something is grounded, it’s connected to the earth in a way that allows electrical current or electromagnetic interference to safely and effectively be redirected away from sensitive components or signals.), which adds to the complexity of installation.
- Connectors: Like UTP, STP also uses RJ-45 connectors, which are widely used in Ethernet networks.
- Combination of Techniques: STP cables use both shielding and twisting of wire pairs to provide maximum protection from interference. The shielding guards against EMI and RFI, while the twisting helps to reduce crosstalk, a form of signal interference where a signal transmitted on one pair gets coupled with another pair.
- Wire Pairs and Shielding: STP cables consist of four pairs of wires, each wrapped in a foil shield. This individually shielding of pairs is then encompassed in an overall metallic braid or foil. This dual shielding structure provides superior protection against interference but also contributes to the cable’s rigidity (inflexibility) and difficulty of installation.
To sum up, STP cables are a reliable choice for high-speed networks, especially in environments with significant potential interference. However, their cost and complexity of installation mean they are generally used in specific circumstances where their advantages outweigh their drawbacks.

Coaxial cable: Coaxial cable, often known as “coax,” is a type of cabling solution that was once very popular in computer networks, but has been largely replaced by Unshielded Twisted Pair (UTP) cable for many Ethernet installations. However, it still finds uses in specific areas due to its specific characteristics:
- Structure:
  
  A coaxial cable consists of a central copper conductor that is used to transmit electronic signals. This central conductor is surrounded by a layer of flexible plastic insulation. Over this insulation, there is a woven copper braid or metallic foil which acts as the second wire in the circuit. This outer conductor (braid/foil) also serves as a shield for the inner conductor, preventing external Electromagnetic Interference (EMI) or Radio Frequency Interference (RFI) from distorting the signal. Finally, the entire assembly is covered with a cable jacket to protect against minor physical damage.
- Benefits: Coaxial cables offer several benefits, including better protection against signal interference due to the shielding provided by the outer conductor. This can make them a suitable choice in environments where EMI/RFI is a concern.
- Applications: Despite the rise of UTP for Ethernet installations, coaxial cable is still used in specific scenarios:
  - Wireless Installations: Coaxial cables are often used to connect antennas to wireless devices. Their ability to carry high-frequency signals over longer distances with minimal loss makes them an ideal choice for such applications.
  - Cable Internet Installations: Coaxial cables are commonly used in broadband cable internet installations. Many cable Internet service providers deliver their services over coaxial cables due to their high bandwidth capacity and resistance to interference.
In summary, while coaxial cables may not be as common as they once were in Ethernet networks, they remain a key part of many wireless and cable Internet installations. Their structural characteristics make them suitable for situations requiring high-frequency transmission and resistance to signal interference.
UTP Cabling:
Properties: Unshielded Twisted Pair (UTP) cabling is a common type of networking media, especially in Ethernet networks. Here are the key properties:
- Structure:
  
  UTP cabling consists of four pairs of color-coded copper wires that are twisted together and then encased (to surround or cover something completely, especially to protect it) in a flexible plastic sheath (any layer that covers and fits closely over something for protection). Each pair is twisted a different number of times, which helps to mitigate crosstalk, a type of interference between the different pairs. The color-coding of the wires helps during the installation process to ensure each wire is correctly connected.
- Size: UTP cables are relatively small and flexible, which makes them easy to install, even in tight spaces or in areas where there may be sharp bends. They’re also lightweight, which can be an advantage in installations where heavier cables might place too much strain on infrastructure.
- Shielding: As the name implies, UTP cables do not have any additional shielding against Electromagnetic Interference (EMI) or Radio Frequency Interference (RFI). However, they employ a technique called cancellation to counter these effects. This involves placing two wires in an electrical circuit close together, so their magnetic fields are the exact opposite of each other. This effectively cancels out any outside EMI and RFI signals. The different number of twists per wire pair further enhances the cancellation effect.
- Cancellation: The cancellation effect utilized in UTP cables is a simple yet effective measure to combat interference. By closely pairing two wires and twisting them around each other, each wire in the pair is exposed to nearly the same interference. Because the two wires carry opposite signals (one carries a positive version of the signal, the other carries a negative version), when the signal is received, any interference picked up along the way gets cancelled out.
- Variation in Twists: You’ll notice in a UTP cable that the orange/orange-white pair is twisted less than the blue/blue-white pair. Each pair is twisted at different lengths to help prevent crosstalk between pairs. By varying the twist lengths, the same segments of different pairs are less likely to be next to each other, decreasing the chances of interference.
UTP cabling, with its balance of affordability, ease of installation, and performance, has become the standard choice for many network applications, especially those involving Ethernet.

UTP Cabling Standards: UTP (Unshielded Twisted Pair) cabling is subject to certain standards outlined by the TIA/EIA (Telecommunications Industry Association/Electronic Industries Alliance) to ensure quality and consistency across products and installations. One such standard is the TIA/EIA-568, which outlines cabling standards specifically for local area network (LAN) installations.

Here are some key categories within UTP cabling as per the TIA/EIA-568 standard:
- Cat 3 Cable:
  
  Cat 3 is an older UTP standard, typically used for voice communication and often used in phone line installations. This category of cable supports data transfer rates up to 10 Megabits per second (Mb/s) at a maximum length of 100 meters. It’s not commonly used in modern data networks due to its limited bandwidth.
- Cat 5 Cable:
  
  Cat 5 cable supports higher data transfer rates compared to Cat 3, with a maximum capacity of 100 Mb/s. It can technically support gigabit speeds (1000 Mb/s), but this isn’t recommended due to its limitations in handling crosstalk at those speeds. It’s used in data transmission for typical Ethernet applications.
- Cat 5e Cable: Cat 5e (the ‘e’ stands for ‘enhanced’) is an improvement over Cat 5, designed to reduce crosstalk. This makes it better suited to support Gigabit Ethernet with a speed of up to 1000 Mb/s. It’s commonly used in modern network installations.
- Cat 6 Cable:
  
  Cat 6 cables are even more advanced, with an added separator between each pair of wires to further reduce crosstalk. They can support data transmission rates from 1000 Mb/s up to 10 Gigabits per second (Gb/s), although usage at 10 Gb/s isn’t recommended due to potential limitations at longer distances. Cat 6 cables can achieve 10 Gb/s speeds up to 55 meters, but for distances more than that, lower speeds are advised.
Each of these cable categories has a specific use case and choosing the correct type of cable for a given application is vital to achieving the desired network performance. It’s also important to note that higher category numbers don’t just offer increased performance – they also offer improved signal integrity due to advances in insulation and twisting techniques.

UTP Connectors: Unshielded Twisted Pair (UTP) cables, commonly used in Ethernet networks and telephone systems, are typically terminated using an RJ-45 connector. The RJ-45, short for “Registered Jack-45”, is a standard type of physical connector for network cables. RJ-45 connectors are similar in appearance to the more familiar RJ-11 connectors used for traditional telephone cables, but they are somewhat larger.

The TIA/EIA-568 standard describes the specific pin assignments, also known as pinouts, for Ethernet cables. This pinout standardization ensures that all devices connected to the network interpret the signals they receive correctly. In an RJ-45 connector, there are eight pins, each corresponding to a separate wire in the UTP cable.

Here are some key points to understand about UTP connectors, specifically the RJ-45:
- The RJ-45 connector is the male component, which is crimped at the end of the cable. This crimping process physically attaches the connector to the cable and electrically connects the connector to the individual wires within the cable.
- The socket, the female component, is typically part of a network device, wall outlet, cubicle partition outlet, or patch panel. When the RJ-45 connector is inserted into a socket, it forms a secure physical and electrical connection.
- The wire color codes to pin assignments specified by TIA/EIA-568 help technicians correctly wire the RJ-45 connectors. A UTP cable generally has four pairs of color-coded wires: orange (with one wire in the pair being orange and white), green (with one wire being green and white), blue (with one wire being blue and white), and brown (with one wire being brown and white).
- It’s essential that all copper media terminations (like the connections at the end of a UTP cable) be of high quality to ensure optimum performance with current and future network technologies. This means the crimping process has to be done accurately to make sure each wire in the cable makes solid contact with the corresponding pin in the RJ-45 connector.
One popular method of wiring RJ-45 connectors to UTP cables is the T568B standard, often used for Ethernet cables, in which the wire pairs are ordered as follows from pin 1 to pin 8: orange/white, orange, green/white, blue, blue/white, green, brown/white, brown. There’s also the T568A standard, which swaps the positions of the orange and green pairs.

In summary, UTP connectors, particularly the RJ-45, play a critical role in networking by enabling UTP cables to physically and electrically connect to networking devices in a standardized way.

Types of UTP Cable:

In Ethernet networking, there are three primary types of UTP (Unshielded Twisted Pair) cables distinguished by their wiring patterns and uses. These are Straight-through, Crossover, and Rollover cables. Let’s discuss each one in more detail:
- Straight-Through Cable: This is the most common type of UTP cable. Both ends of a straight-through cable follow the same wiring standard, either T568A or T568B. As the name suggests, the wiring “goes straight through,” meaning that Pin 1 on one end connects to Pin 1 on the other end, Pin 2 to Pin 2, and so on up to Pin 8. Straight-through cables are used to connect network hosts (like computers, printers, etc.) to network devices like switches or hubs.
- Crossover Cable: A crossover cable has one end wired as per the T568A standard and the other end wired as per the T568B standard. This allows the cable to “cross over” the transmit and receive pairs, meaning Pin 1 (transmit) on one end connects to Pin 3 (receive) on the other end, and Pin 2 (transmit) on one end connects to Pin 6 (receive) on the other end, and so on. Crossover cables are used to directly connect two similar devices or hosts together, like connecting a computer to another computer, a switch to another switch, or a router to another router, without needing a network intermediary device in between.
- Rollover Cable (also known as a Console Cable): A rollover cable is a type of cable that is mostly used for connecting to the console port of a device like a router or switch. In this cable, the order of the wires is completely reversed from one end to the other (i.e., Pin 1 on one end connects to Pin 8 on the other end, Pin 2 to Pin 7, and so forth). Rollover cables are typically not used for transmitting data but are used for signaling and management purposes, particularly for configuring network devices directly.
Each of these cable types has its specific uses and is essential for the proper functioning of a network. A clear understanding of when and how to use each one is a fundamental skill in network cabling and installation.
Fiber-Optic Cabling:
Properties of Fiber-Optic Cabling:
Fiber-optic cabling has become a popular choice for transmitting data, especially over long distances and at high bandwidths, primarily because of its numerous advantages over other forms of transmission. Let’s discuss its properties in more detail:
- Long Distance Transmission: Fiber-optic cables can transmit data over much longer distances compared to copper-based cabling (UTP or coaxial). This is because light signals attenuate (to make something weaker or less effective) much less over distance than electrical signals. Some types of fiber-optic cable can carry signals for tens of kilometers without requiring signal repeaters.
- Thin and Flexible: Fiber-optic cables are made of thin strands of glass or plastic that are incredibly flexible and can be bundled together to create a larger, more robust cable. Despite their thinness, these strands are capable of carrying a vast amount of data.
- Less Attenuation: Attenuation refers to the reduction in signal strength over distance. In fiber-optic cables, the attenuation is much less compared to copper cables. This means that the signal can travel longer distances without significant loss of signal strength or quality.
- Immune to Electromagnetic Interference (EMI) and Radio Frequency Interference (RFI): Because fiber-optic cables use light to transmit data rather than electricity, they are immune to EMI and RFI. This makes fiber-optic cables an excellent choice for environments where EMI/RFI is a concern, like industrial settings or in proximity to power lines.
  Immune: Not affected by something, especially something that you might expect to be harmful.
- High Bandwidth: Fiber-optic cables can carry a higher volume of data (i.e., have greater bandwidth) than copper cables of the same diameter. This makes fiber-optic cabling the preferred choice for high-speed data transmission applications.
These properties make fiber-optic cabling an excellent choice for a wide range of applications, including telecommunication networks, cable TV services, and internet connections.

Fiber Media Cable Design:

Fiber-optic cables are a critical technology in telecommunications and data networking, providing a path for data to travel as light pulses. The design of a fiber-optic cable is quite sophisticated and includes several key components, each playing a specific role:
- Jacket: The outermost layer of the cable, the jacket serves to protect the internal fibers from physical damage, moisture, and contaminants. The materials used for the jacket can vary based on the specific requirements of the cable’s intended usage, such as resistance to specific chemicals or environmental conditions.
- Strengthening Material: This is typically found just under the jacket and surrounds the buffer. Its main function is to prevent the fiber cable from being stretched or strained (showing the effects of worry or pressure) during installation or regular use. This part often uses materials known for their high tensile (used to describe the extent to which something can stretch without breaking) strength, like those used in bulletproof vests.
- Buffer: The buffer’s main purpose is to protect the delicate core and cladding (a layer of a hard material, used as protection) from mechanical damage. It may come in various forms and thicknesses, depending on the design specifications of the cable, and acts as a cushion to absorb shocks and pressures that might otherwise damage the delicate internal components.
- Cladding: The cladding surrounds the core and functions to keep the light within the core as it travels down the fiber. It does this by reflecting the light back into the core. The cladding is usually made of a material that has a different refractive index than the core, so the boundary between the core and cladding acts like a mirror to the light traveling within the core.
- Core: This is the central part of the fiber where the light transmission occurs. It is usually made of silica or glass, though plastics are used in some applications. The core’s quality, purity, and design are critical to the cable’s overall performance, as this is where the actual transmission of data in the form of light pulses occurs.
Together, these components create a highly efficient medium for data transmission. Fiber-optic cables can transmit data over much longer distances compared to traditional copper cables, with less signal attenuation. They are also immune to electromagnetic interference (EMI) and radio frequency interference (RFI), providing a more reliable and secure data transmission.

The design and manufacturing process of fiber-optic cables are quite complex, requiring precise control over materials and fabrication techniques to ensure optimal performance. Different types of fiber-optic cables may be designed to meet the specific needs of various applications, such as long-haul telecommunications, local area networks (LANs), or specialized industrial usage. The detailed engineering behind each component allows fiber-optic cables to meet the high demands of modern data communication systems.

Fiber-Optic Connectors: Fiber-optic connectors are specialized devices used to join two ends of fiber-optic cables, allowing light signals to pass between them. These connectors are vital components in fiber-optic communication systems, providing connections between different equipment or network segments. Here is an overview of fiber-optic connectors, focusing on specific types and features:
1. Directionality: Optical fibers transmit light in one direction. Therefore, two fibers are usually required to support full-duplex operation, meaning simultaneous transmission and reception of signals.
2. Straight-Tip (ST) Connectors:
  
  One of the earliest types of fiber-optic connectors, ST connectors utilize a twist-on/twist-off mechanism to secure the connection. This provides a sturdy and reliable connection but might be considered less convenient than some newer connector types.
3. Subscriber Connector (SC) Connectors:
  
  These are often referred to as square or standard connectors and are recognizable by their push-pull mechanism that ensures positive insertion. SC connectors are versatile (able to do many different things) and can be used with both multimode and single-mode fiber.
4. Lucent Connector (LC) Simplex Connectors:
  
  LC connectors are smaller than SC connectors and have become popular due to their compact size. They are often used in applications where space is a premium.
5. Duplex Multimode LC Connectors:
  
  Similar to standard LC connectors but designed to handle two fibers for full-duplex operation. These connectors are often used in more advanced network applications.
6. Color Coding and Protection:
  - Yellow Jacket: Typically signifies single-mode fiber cables.
  - Orange or Aqua Jacket: Indicates multimode fiber cables.
  - Protective Caps: To prevent damage to the connectors when not in use, they should be protected with small plastic caps.
  - Fiber Patch Cords: These are used to interconnect infrastructure devices, such as switches and routers, within a data center or networking environment.
Fiber-optic connectors play an essential role in maintaining the integrity and efficiency of the optical signal as it passes through the network. Proper selection, installation, and maintenance of these connectors are crucial to the overall performance and reliability of the fiber-optic communication system. Different connector types have specific applications, advantages, and disadvantages, so the choice of connector can be critical depending on the specific needs of the network. Manufacturers have developed a variety of connector types to meet the varied needs of different applications, and ongoing developments in this area continue to improve the performance and ease of use of fiber-optic connections.

Fiber versus Copper: Fiber-optic and copper (specifically Unshielded Twisted Pair or UTP) cabling are the two prominent types of media used for data transmission in modern networks. They have distinct properties, advantages, and disadvantages, which are summarized below:
1. Bandwidth Supported:
  - UTP Cabling: Supports speeds ranging from 10 Mb/s to 10 Gb/s.
  - Fiber-Optic Cabling: Supports significantly higher speeds, ranging from 10 Mb/s to 100 Gb/s. This makes fiber-optic cabling suitable for high-bandwidth applications, such as data centers and backhaul connections.
2. Distance:
  - UTP Cabling: Suitable for relatively short distances, typically ranging from 1 to 100 meters.
  - Fiber-Optic Cabling: Can support much greater distances, from 1 to 100,000 meters. This makes it the preferred choice for long-haul communications.
3. Immunity to Electromagnetic Interference (EMI) and Radio Frequency Interference (RFI):
  - UTP Cabling: Has low immunity to EMI and RFI, making it susceptible to interference from other electrical devices.
  - Fiber-Optic Cabling: Offers high immunity to both EMI and RFI, as it uses light rather than electrical signals. This makes it suitable for environments with a high level of electromagnetic activity.
4. Immunity to Electrical Hazards:
  - UTP Cabling: Low immunity to electrical hazards, such as lightning strikes or electrical surges.
  - Fiber-Optic Cabling: Completely immune (that cannot catch or be affected by a particular disease or illness) to electrical hazards, as it does not conduct electricity.
5. Media and Connector Costs:
  - UTP Cabling: Has the lowest cost for both media and connectors.
  - Fiber-Optic Cabling: Generally more expensive due to the complex manufacturing processes involved in producing the cables and the precision required for the connectors.
6. Installation Skills Required:
  - UTP Cabling: Requires the lowest level of skill for installation.
  - Fiber-Optic Cabling: Installation requires specialized skills and tools, as the fibers must be carefully handled and precisely aligned.
7. Safety Precautions:
  - UTP Cabling: Lowest safety precautions are needed.
  - Fiber-Optic Cabling: Requires the highest level of safety precautions, particularly during installation, to prevent potential injury from glass shards or laser light.
8. Conclusion: Fiber-optic and UTP cabling have their specific applications, advantages, and limitations. Fiber-optic cabling offers higher bandwidth, greater distances, and complete immunity to EMI/RFI and electrical hazards but comes at a higher cost, complexity, and need for specialized installation skills. UTP cabling, on the other hand, is more accessible and cost-effective for shorter distances and lower bandwidth requirements but has lower immunity to interference and hazards. The choice between these two media types depends on the specific needs and constraints of the network in question.
Wireless Media:
Properties of Wireless Media: The properties of wireless media refer to the characteristics and considerations that are specific to data communications using radio or microwave frequencies. Below is a comprehensive explanation of the key properties and areas of concern associated with wireless media, based on the provided references:
1. Nature of Communication:
  - Electromagnetic Signals: Wireless media carry electromagnetic signals representing the binary digits (0s and 1s) used in data communication.
  - Frequencies: Communication typically occurs via radio or microwave frequencies.
2. Coverage Area:
  - Limitations: The range of wireless communication can be limited by various factors, such as the construction materials used in buildings, the design of structures, and the local terrain (used to refer to an area of land when you are mentioning its natural features).
  - Variation: Different wireless technologies offer various ranges of coverage, from a few meters (such as Bluetooth) to several kilometers (like WiMAX).
3. Interference:
  - Sources: Wireless communication can be disrupted by common devices and phenomena such as fluorescent (producing bright light by using some forms of radiation) lights, microwave ovens, other wireless communications, and even weather conditions.
  - Impact: Interference can lead to a decrease in signal strength, data corruption, or complete loss of connection.
4. Security:
  - Unauthorized Access: Wireless signals can be intercepted by unauthorized devices and users, leading to potential security breaches.
  - Measures: Security protocols like WPA3 and encryption techniques are employed to secure wireless communication and prevent unauthorized access.
5. Shared Medium:
  - One Device at a Time: In a wireless environment, only one device can send or receive at a time within a given frequency channel.
  - Sharing: The wireless medium is shared amongst all wireless users within range, which can lead to congestion and competition for access, potentially reducing efficiency.
  - Protocols: Protocols such as Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) are used to manage access to the shared medium.
6. Conclusion: Wireless media offer flexibility and mobility in data communications but come with challenges and concerns related to coverage, interference, security, and the shared nature of the medium. These properties must be carefully considered and managed to optimize the performance, reliability, and security of wireless networks. Techniques and technologies for overcoming these challenges continue to evolve, reflecting the growing importance of wireless communication in various aspects of modern life.
Types of Wireless Media:
1. Wi-Fi (IEEE 802.11): Wi-Fi is a wireless networking technology that uses radio frequencies to provide wireless connectivity to devices such as computers, smartphones, and tablets.
  - Standard: IEEE 802.11
  - Access Method: Uses Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA), a protocol that helps manage how data packets are placed on the network. Devices must wait until the channel is clear before transmitting.
  - Coverage: Typical coverage ranges from a few meters to 100 meters, depending on factors like the access point’s power and environmental obstructions.
  - Use Cases: Widely used in homes, businesses, and public places to provide wireless Internet access.
2. Bluetooth (IEEE 802.15): Bluetooth is a wireless technology for short-range communications, often used to connect peripheral devices like headphones, keyboards, or smartwatches to a central device.
  - Standard: IEEE 802.15
  - Type: Wireless Personal Area Network (WPAN)
  - Pairing Process: Uses a device pairing process that facilitates secure connections between devices.
  - Range: Typically, distances range from 1 to 100 meters, depending on the class of the device.
  - Use Cases: Common in personal gadgets, automotive applications, and various consumer electronics.
3. WiMAX (IEEE 802.16): WiMAX, short for Worldwide Interoperability for Microwave Access, is a wireless broadband technology designed to provide high-speed Internet access.
  - Standard: IEEE 802.16
  - Coverage: Can cover large geographical areas, potentially spanning many kilometers.
  - Type: Offers wireless broadband access, often serving as an alternative to traditional wired broadband like DSL or cable.
  - Use Cases: Utilized for providing Internet in remote or underserved areas, mobile broadband, and metropolitan area networks.
Wireless Local Area Network (Wireless LAN or WLAN): Wireless Local Area Network (Wireless LAN or WLAN) is a type of local area network that enables devices to connect to a network without physical cables. It’s widely used in homes, businesses, and public places. Here’s a comprehensive look at Wireless LAN, considering the provided references.
1. Wireless Access Point (AP): A Wireless Access Point is a central device that connects wireless devices to a wired LAN. It acts as an interface between wireless clients and the existing network infrastructure.
  - Functionality: It concentrates the wireless signals from users and connects them to a copper-based network infrastructure, such as Ethernet.
  - Placement: Access Points can be placed in strategic locations to provide coverage throughout a building or area.
  - Types: There are standalone APs and integrated ones within routers, especially in home and small business environments.
2. Wireless NIC Adapters: Network Interface Card (NIC) adapters for wireless communication are essential for each network host to connect to a WLAN.
3. Integrated Routers for Home and Small Business: In home and small business environments, wireless routers often integrate multiple functions:
  - Router: Directs traffic between the local network and the Internet.
  - Switch: Allows wired devices to connect and communicate within the local network.
  - Access Point: Provides the wireless connectivity for devices within the network.
4. Standards and Security:
  - Standards: WLAN typically operates under the IEEE 802.11 family of standards, which define various speed and frequency specifications.
  - Security: Security is vital in a WLAN to prevent unauthorized access. Common security protocols include WEP, WPA, and WPA2.
5. Advantages and Challenges:
  - Advantages: Flexibility, mobility, and ease of installation are among the main benefits of WLAN.
  - Challenges: Coverage area limitations, interference from other devices, and security concerns are some of the challenges that must be managed.

Data Link Layer

Layer 2 Data Link Addresses:
Logical Link Control (LLC) {Sublayers of data link layer}: The Logical Link Control sublayer sits above the MAC sublayer and is responsible for communication between the data link layer and the network layer.

Key Responsibilities and Characteristics:
- Network Layer Communication: LLC communicates directly with the network layer (Layer 3).
- Protocol Identification: It identifies the network layer protocol being used for the frame (e.g., IPv4 or IPv6), enabling the data link layer to support multiple network layer protocols simultaneously.
- Interface Utilization: LLC allows multiple Layer 3 protocols to utilize the same network interface and media. It acts as a translator between the network and data link layers, ensuring the proper protocol is used for each frame.
- Error Detection and Flow Control: Though not explicitly mentioned in the reference, LLC also plays a role in error detection and control and the flow of data across the link.
Media Access Control (MAC): The MAC sublayer is closely associated with the physical network hardware and deals with the protocols that control the physical network connections.

Key Responsibilities and Characteristics:
- Media Access Processes: MAC defines the rules for how devices on the network access the physical media. It deals with how frames are placed onto the media, control of access to the media, and avoidance of collisions if it’s a shared media.
- Data Link Layer Addressing: Provides the hardware addressing (also known as MAC addressing) that identifies devices within the network. These addresses are unique to each network interface card (NIC).
- Access to Network Technologies: MAC is responsible for communication with various network technologies, including both wired (such as Ethernet over copper or fiber-optic cable) and wireless technologies (such as Wi-Fi and Bluetooth).
- Adaptation to Physical Networks: As packets travel from the source host to the destination host, they may pass over various physical networks, including copper wires, optical fibers, wireless signals, and satellite links. MAC plays a crucial role in adapting the transmission to these diverse physical media.
Controlling Access to the Media: Controlling Access to the Media is akin to the rules governing traffic on a roadway. In the same way that vehicles must follow specific protocols like merging, waiting at a stop sign, or obeying signal lights to avoid accidents, data packets in a network must adhere to certain rules to avoid collisions and ensure smooth communication. These rules or protocols vary depending on the network type, such as Ethernet or Wi-Fi, and can differ in approach. For example, Ethernet might use Carrier Sense Multiple Access with Collision Detection (CSMA/CD), where devices listen before transmitting, while wireless networks might prioritize collision avoidance through Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA). The necessity of controlling access to the media is fundamental to prevent data collisions, which could lead to lost or corrupted data and an inefficient use of the network medium. Without proper media access control, the network could become chaotic and unreliable, similar to a road without traffic rules.
Hub and Spoke: The Hub and Spoke topology is built around a central site that connects all branch sites using point-to-point links. You can imagine it as the spokes on a bicycle wheel, where each spoke represents a direct connection from the outer rim (branch sites) to the hub at the center.

In this configuration, the central hub is the focal (central) point of the network, and all communication between branch sites must pass through it. This simplifies the network structure, making it easier to manage and potentially more cost-effective, as there’s no need for direct connections between all the branches. However, this also means that if the hub fails, all connections will be lost, since there’s no direct communication between the branches.
Mesh: Contrastingly, the Mesh topology is designed to provide high availability by ensuring that every end system is interconnected to every other system. Imagine a web or net where each node is directly connected to every other node within the network.

This complete interconnection ensures that there are multiple paths for data to travel, making the network highly resilient to failures. If one connection fails, data can simply take another route. However, this level of redundancy requires many more connections and significantly more hardware, which can lead to higher administrative and physical costs. Managing a Mesh network can be complex and time-consuming, and the cost might not be justified unless constant connectivity is a critical need.
Star Topology:

The Star topology is a common network configuration where all end devices are connected to a central intermediate device, often an Ethernet switch. You can visualize it as a star, where each point (or end device) is connected directly to the center.

In the Star topology, all data that moves between devices must pass through the central hub or switch. This centralized control can simplify network management and troubleshooting, as it’s easy to isolate problems and make changes. However, the central device also becomes a single point of failure; if it goes down, all devices lose connectivity.

Ethernet switches are commonly used in Star topologies, making it a prevalent structure in modern local area networks (LANs).
Extended Star Topology:

An Extended Star topology builds on the basic Star structure by interconnecting multiple star networks through additional Ethernet switches. Imagine several star networks, each with its central hub, and those hubs are then connected to each other.

This configuration combines the benefits of the Star topology with additional redundancy and scalability. By interconnecting multiple stars, an Extended Star can span larger physical distances and connect more devices. It also provides some level of fault tolerance since the failure of one central device in one star won’t necessarily affect the others.
Bus Topology:

The Bus topology is a type of network configuration where all end systems (computers, printers, etc.) are connected to a single, continuous cable called the “bus.” This central cable essentially forms the backbone of the network, and each device on the network is chained to this main line.

Terminators are often placed at each end of the bus to prevent signals from bouncing back along the cable. The key features of a Bus topology include:
- Simplicity: Setting up a Bus topology is relatively simple and inexpensive, particularly when using coaxial cables. It often requires less cabling than other topologies, making it an attractive option for smaller networks.
- No Need for Switches: Unlike many other topologies, Bus doesn’t require switches to interconnect the end devices. They are all directly connected to the main bus line.
- Single Point of Failure: If the central cable (bus) fails or if there’s a break in the line, it can bring down the entire network. This lack of redundancy is one of the significant downsides of this topology.
- Legacy Use: The Bus topology was a popular choice in early Ethernet networks due to its cost-effective nature. However, with advancements in technology and changing network demands, it has largely fallen out of favor.
Ring Topology:

In a Ring topology, end systems (like computers and other devices) are connected to their respective neighbors, forming a physical ring or circle. The data travels in a continuous loop from one device to another in a predetermined direction, either clockwise or counterclockwise.

Key Features of Ring Topology:
- No Need for Termination: Unlike Bus topology, there’s no need to terminate the ends of the network since the data flows in a continuous loop.
- Simple Data Flow: Data travels in one direction around the ring, ensuring a predictable and organized flow of information.
- Single Point of Failure: If one connection in the ring fails, the entire network can be affected, as the continuous loop is broken.
Fiber Distributed Data Interface (FDDI): FDDI is a set of standards and protocols that were commonly used to implement Ring topology using fiber-optic cables. FDDI networks typically consist of two rings for redundancy, with data able to travel in both directions (dual ring).

Key Features of FDDI:
- High Bandwidth: By utilizing fiber-optic cables, FDDI provides high-speed data transmission.
- Dual Ring: The use of two rings adds a level of redundancy, enhancing reliability.
- Legacy Usage: FDDI was once a popular choice for networking, particularly in environments requiring high-speed connections. However, newer technologies have largely supplanted it.
Token Ring Networks: Token Ring is a protocol used in a Ring topology where a “token” is passed around the ring. A device can only transmit data if it “holds” the token, ensuring orderly access to the network.

Key Features of Token Ring:
- Controlled Access: The token-passing mechanism helps in avoiding collisions and ensures that only one device can transmit at a time.
- Different from Ethernet: Unlike Ethernet, which may use a “listen before talk” approach, Token Ring uses the token to manage access explicitly.
- Legacy Technology: Like FDDI, Token Ring networks were more prevalent in the past but have been largely replaced by more modern protocols and topologies.
Data Link Frame:
- Frame start and stop indicator flags: Identifies the beginning and end limits of the frame.
- Addressing: Indicates the source and destination nodes.
- Type: The Type field in an Ethernet frame is 16 bits long and serves to identify the Layer 3 protocol encapsulated in the frame. Common examples of Layer 3 protocols include IPv4 and IPv6. This field helps the receiving device understand how to interpret the payload of the frame, i.e., how to pass it up to the appropriate Layer 3 protocol for further processing.
- Control: The Control field might be used to identify special flow control services, such as Quality of Service (QoS). QoS mechanisms allow for prioritization of certain types of traffic over others. This is particularly useful in real-time communication scenarios where latency and bandwidth must be carefully managed.
- Data: Contains the frame payload (i.e., packet header, segment header, and the data).
Data link layer protocols:
- Ethernet: Ethernet is a family of wired networking technologies used in local area networks (LANs). It defines the physical layer (cables, switches) and the data link layer’s MAC (Media Access Control) sublayer. Ethernet uses a frame structure that includes source and destination MAC addresses, EtherType (indicating the upper layer protocol), and error-checking information. Ethernet’s key characteristics include its flexibility in handling various data types and its broad adoption in LANs.
- 802.11 Wireless: 802.11 Wireless, commonly referred to as Wi-Fi, is a set of wireless networking protocols. Unlike Ethernet, which relies on physical cables, Wi-Fi allows devices to connect to a LAN wirelessly. The 802.11 protocols define the rules for transmitting data over the airwaves, using technologies like CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) to regulate traffic. While Ethernet is typically used in wired environments, Wi-Fi is employed where wireless connectivity is required.
- Point-to-Point Protocol (PPP): PPP is a data link layer protocol used to establish a direct connection between two nodes. It can provide connection authentication, transmission encryption (using ECP, RFC 1968), and compression. PPP is often used for establishing a direct link between two networking devices over serial cable, phone line, trunk line, cellular telephone, specialized radio links, or fiber optic links. Unlike Ethernet and Wi-Fi, which can connect multiple devices, PPP is used for simple, direct connections.
- HDLC (High-Level Data Link Control): HDLC is a bit-oriented synchronous data link layer protocol used for communication over point-to-point and multipoint links. HDLC encapsulates data into framed packets that allow for synchronous transmission. It’s more generic (not specific) than PPP, allowing for various configurations, such as unicast or multicast, over different types of media. HDLC can be seen as a precursor (a person or thing that comes before somebody/something similar and that leads to or influences its development) to PPP and was used in similar contexts but is generally considered less flexible.
- Frame Relay: Frame Relay is a packet-switching protocol that operates at the data link layer. It’s designed for cost-efficient data transmission for intermittent (stopping and starting often over a period of time, but not regularly) traffic between LANs and between endpoints in a WAN. Frame Relay creates virtual circuits, which provide a path for data transmission. Unlike Ethernet, which can be used for general-purpose LANs, Frame Relay is typically used in wide area networks (WANs) where guaranteed quality of service (QoS) isn’t required.