What two criteria are used to help select a network medium from various network media? (Choose two.)
- the types of data that need to be prioritized
- the cost of the end devices utilized in the network
- the distance the selected medium can successfully carry a signal
- the number of intermediate devices installed in the network
- the environment where the selected medium is to be installed
The two criteria used to help select a network medium from various network media are:
- The distance the selected medium can successfully carry a signal
- The environment where the selected medium is to be installed
Detailed Explanation:
Selecting the appropriate network medium for a specific environment and application is a crucial aspect of network design. The medium not only influences the performance and reliability of the network but also its overall cost and complexity. Two of the most critical criteria that help in making this selection are the distance the medium can carry a signal and the environment where the medium will be installed. These factors directly impact the physical layer of the OSI model, affecting both the data transmission capabilities and the robustness of the network infrastructure.
1. The Distance the Selected Medium Can Successfully Carry a Signal
One of the fundamental considerations in choosing a network medium is the distance it can carry a signal without significant degradation. This criterion is vital because different media have varying capacities to transmit data over distances, influenced by factors like signal attenuation, interference, and the medium’s inherent physical properties.
a. Signal Attenuation: Signal attenuation refers to the loss of signal strength as it travels through the medium. Over long distances, the signal weakens, which can result in errors or complete loss of data transmission. Various media types, such as twisted-pair cables, coaxial cables, fiber optics, and wireless, have different attenuation characteristics. For example, copper cables (like twisted-pair or coaxial) are more prone to attenuation over longer distances compared to fiber optic cables, which can transmit data over several kilometers with minimal signal loss.
b. Repeater and Amplifier Usage: To mitigate attenuation, repeaters or amplifiers can be used to regenerate or boost the signal strength at intervals. However, the need for such devices adds complexity and cost to the network. Choosing a medium that naturally supports the required transmission distance without needing excessive repeaters is often more efficient. For instance, fiber optic cables are preferred in scenarios requiring long-distance data transmission because they can carry signals much further than copper cables without the need for amplification.
c. Bandwidth Considerations: Distance also ties into the bandwidth capacity of the medium. High-bandwidth applications require a medium that can not only handle the necessary data rates but also maintain signal integrity over the required distance. For example, fiber optics offer significantly higher bandwidth and can sustain that bandwidth over long distances compared to traditional copper cables.
d. Application Scenarios: The distance requirement is particularly critical in designing backbone networks, metropolitan area networks (MANs), and wide area networks (WANs) where data needs to travel across long distances. In such cases, the choice of fiber optic cables is often preferred due to their ability to handle long-distance transmission with high bandwidth, making them ideal for linking buildings, campuses, or even cities.
2. The Environment Where the Selected Medium is to be Installed
The environment where the network medium will be installed plays a significant role in determining the appropriate medium. Different environments present unique challenges, such as physical obstructions, electromagnetic interference, temperature extremes, and potential exposure to water or chemicals. The chosen medium must be resilient enough to perform reliably under these specific conditions.
a. Physical Obstructions and Interference: In an indoor environment, such as an office building, the network medium may need to navigate through walls, floors, and ceilings. Twisted-pair cables (such as Cat5e or Cat6) are commonly used in these scenarios due to their flexibility and ease of installation. However, in environments with a high level of electromagnetic interference (EMI), such as factories or data centers with heavy machinery or electrical equipment, shielded cables or fiber optics may be necessary. Fiber optics are immune to EMI, making them ideal for environments with high levels of electrical noise.
b. Outdoor and Harsh Environments: For outdoor installations, the medium must withstand environmental factors like temperature fluctuations, moisture, and exposure to elements. Fiber optic cables, when properly sheathed, can be used in outdoor settings due to their resistance to environmental factors. In contrast, copper cables might require additional protection, such as conduits or waterproofing, to prevent corrosion and damage.
c. Installation and Maintenance Considerations: The environment also affects the ease of installation and maintenance. In historical buildings or environments where minimal disruption is desired, wireless media might be preferred to avoid the need for extensive cabling. However, wireless solutions must contend with challenges like signal obstruction from walls and potential interference from other wireless devices.
d. Security Implications: The physical environment also has security implications. Fiber optics are considered more secure than copper cables because they are difficult to tap without detection. In environments requiring high security, such as government facilities or financial institutions, the security of the medium may influence the choice. Additionally, in outdoor or public spaces, wireless networks must be secured against unauthorized access, which might involve additional encryption and authentication mechanisms.
e. Cost vs. Environment Adaptability: While cost is always a consideration, the environment often dictates the necessity of investing in more durable or sophisticated media. For example, although copper cables might be cheaper than fiber optics, the long-term reliability and lower maintenance requirements of fiber in certain environments may justify the higher initial cost.
Integration of Distance and Environmental Considerations
The interplay between distance and environment further refines the selection process. For example, a network designed to span across a campus with buildings separated by several kilometers would need to use a medium like fiber optics to handle both the distance and potential environmental factors like outdoor exposure. On the other hand, a small office with close proximity devices may find twisted-pair cables sufficient, provided that the environment is relatively controlled.
In scenarios where both long distance and challenging environments are factors, hybrid solutions might be employed. For instance, fiber optics could be used for the backbone network due to its distance capabilities and immunity to interference, while twisted-pair cables might be used within buildings for connecting individual devices.
Conclusion
Selecting a network medium is a nuanced decision that requires careful consideration of multiple factors. Among these, the distance the medium can carry a signal and the environment where it will be installed are two of the most critical. These criteria influence the overall performance, reliability, and cost-effectiveness of the network. By carefully evaluating the specific needs of the network in terms of distance and environmental challenges, network designers can choose a medium that meets both current and future requirements, ensuring robust and efficient data transmission.