Network Design

Physical and Logical Addresses

A person’s name is typically a constant identifier, much like a MAC address in computer networking. A MAC address is a unique, hardware-based identifier assigned to a network interface card (NIC) and remains unchanged regardless of where the host is connected on the network. It serves as the host’s physical address, much like a person’s name is a constant identifier.

On the other hand, a person’s address represents their physical location, which can change over time. Similarly, in networking, the IP address is used to designate the logical location of a host on a network. Unlike the MAC address, the IP address is assigned logically and can be changed as needed. Network administrators assign IP addresses based on the host’s current location within the network, much like a person’s address changes when they move to a new place.

IP addresses consist of two main parts: the network portion and the host portion. The network portion of the IP address is the same for all hosts within the same local network, just as the general location (city or street) in a person’s address remains the same for all houses in a neighborhood. The host portion of the IP address is unique to each device within that local network, allowing specific identification of individual hosts within the same network.

Both MAC and IP addresses are essential for a computer to communicate within a hierarchical network. The MAC address serves as a constant, physical identifier, similar to a person’s name, while the IP address represents the logical network location, similar to a person’s address. Just as both a person’s name and address are necessary to send a letter, both MAC and IP addresses are required for effective communication on a network.

Hierarchical Analogy

Imagine the difficult challenges that would result in the realm of communication if the sole means of transmitting a missive to an individual were through the utilization of the recipient’s appellation. In the absence of streets, urban centers, hamlets, or national demarcations, the act of conveying correspondence to a particular individual residing on the far reaches of the globe would become a task of extraordinary complexity.

On an Ethernet network, the host MAC address can be likened to a person’s name. A MAC address serves as the distinct identifier of an individual host, yet it remains silent about the host’s network location. If all the numberless residents of the internet were to be identified solely by their unique MAC addresses, imagine the difficulty of pinpointing a solitary entity.

Furthermore, Ethernet technology produces large amounts of broadcast traffic to facilitate host-to-host communication. These transmissions are directed to the entire grouping of hosts within a given network, leading to the depletion of bandwidth and an associated lessening of network performance. One must anticipate the consequences if the internet’s countless hosts were conglomerated into a singular Ethernet network relying on broadcasts.

For these dual rationales, expansive Ethernet networks encompassing an overabundance of hosts prove inefficient. A more judicious approach involves segmenting these extensive networks into smaller, more manageable constituents, which can be achieved through the adoption of a hierarchical design model.

Access, Distribution, and Core

Access

The foundational layer, known as the “Access Layer,” serves as the joint for end-user devices to interface with the network. This layer facilitates the interconnection of multiple hosts, enabling seamless communication among them. This connection is typically achieved through the utilization of network devices, such as the Cisco 2960-XR switch, as illustrated in the accompanying diagram, or through the deployment of a wireless access point. It is imperative to note that all devices residing within a singular layer share identical network segments in their respective IP addresses.

In the event that a message is designated for a local host, determined by the network segment of the IP address, the message remains limited within the local domain. However, should the message be directed toward a disparate network, it is then routed upwards to the “Distribution Layer.” In this context, switches serve as the pivotal link to the distribution layer devices, which are typically represented by Layer 3 entities, such as routers or Layer 3 switches, exemplified by the Cisco 2960-XR.

Distribution

The distribution layer serves as a nexus for distinct networks, arranging the transmission of data between them. It often houses more robust switches, exemplified by the Cisco C9300 series depicted in the illustration, as well as routers for network interconnection. Devices at the distribution layer govern both the nature and volume of traffic that traverses from the access layer to the core layer.

Cisco C9300 Series

Core

The core layer comprises a high-velocity backbone layer-able with alternative (backup) linkages. Its primary function lies in the conveyance of considerable volumes of information among numerous terminal networks. Devices at the core level generally encompass difficult, speedy switches and routers, exemplified by the Cisco Catalyst 9600, as illustrated. The principal objective of the core layer is the expeditious transmission of data.

Have you ever been working online and suddenly lost your connection? It can be frustrating, but it’s important to remember that the internet itself didn’t go down, just your connection to it. With so many people relying on network access for work and learning, it’s crucial that networks are reliable.

In this context, reliability means more than just your connection to the internet. This topic focuses on the four aspects of network reliability. The role of the network has evolved from a data-only network to a system that enables the connections of people, devices, and information in a media-rich, converged network environment. For networks to function efficiently and grow in this type of environment, they must be built upon a standard network architecture. Networks also support a wide range of applications and services. They must operate over many different types of cables and devices that make up the physical infrastructure. The term network architecture, in this context, refers to the technologies that support the infrastructure and the programmed services and rules or protocols that move data across the network. As networks evolve, we have learned that there are four basic characteristics that network architects must address to meet user expectations:

• Fault tolerance
• Scalability
• Quality of Service (QoS)
• Security

Fault Tolerance

A fault-tolerant network is designed to limit the number of affected devices during a failure and allow quick recovery when such a failure occurs. These networks depend on multiple paths between the source and destination of a message. If one path fails, the messages are instantly sent over a different link. Having multiple paths to a destination is known as redundancy.

One way to provide redundancy in reliable networks is by implementing a packet-switched network. Packet switching splits traffic into packets that are routed over a shared network. A single message, such as an email or a video stream, is broken into multiple message blocks, called packets. Each packet has the necessary addressing information of the source and destination of the message. The routers within the network switch the packets based on the condition of the network at that moment. This means that all the packets in a single message could take very different paths to the same destination. In the figure, the user is unaware and unaffected by the router that is dynamically changing the route when a link fails.

Scalability

A scalable network is designed to expand quickly and support new users and applications without compromising the performance of existing services. The figure illustrates how a new network can be added to an existing one with ease. Scalable networks are made possible by adhering to accepted standards and protocols, which allows software and hardware vendors to focus on improving their products and services without having to design a new set of rules for operating within the network.

Quality of Service (QoS)

Quality of Service (QoS) is an essential requirement for modern networks. With the advent of new applications such as voice and live video transmissions, users expect high-quality services. Imagine watching a video with constant breaks and pauses – not a pleasant experience, right? As data, voice, and video content converge onto the same network, QoS becomes a primary mechanism for managing congestion and ensuring reliable delivery of content to all users.

Congestion occurs when the demand for bandwidth exceeds the amount available. Network bandwidth is measured in bits per second (bps). When simultaneous communications are attempted across the network, the demand for network bandwidth can exceed its availability, creating network congestion.

When the volume of traffic is greater than what can be transported across the network, devices will hold the packets in memory until resources become available to transmit them. With a QoS policy in place, the router can manage the flow of data and voice traffic, giving priority to voice communications if the network experiences congestion. The focus of QoS is to prioritize time-sensitive traffic. The type of traffic, not the content of the traffic, is what is important.

Network Security

The network infrastructure, services, and the data contained on network-attached devices are crucial personal and business assets.” Network administrators must address two types of network security concerns: network infrastructure security and information security. Securing the network infrastructure includes physically securing devices that provide network connectivity and preventing unauthorized access to the management software that resides on them. Administrators can protect the network with software and hardware security and by preventing physical access to network devices. Security measures like username and password protect the network from unauthorized access.

Network administrators must also safeguard the information enshrined within the packets being transmitted across the network, as well as the data housed on network-attached devices. To fulfill the objectives of network security, three paramount prerequisites must be met.

1. Confidentiality – Data confidentiality dictates that only the designated and sanctioned recipients may ingress and peruse the information.
2. Integrity – Data integrity provides assurance to users that the data remains unaltered during transmission, from its point of origin to its final destination.
3. Availability – Data availability ensures that authorized users can rely on prompt and dependable access to data services.

FAQs

Q1. What is network reliability, and why is it essential for internet users?

A1. Network reliability refers to the ability of a network to provide consistent and uninterrupted services. It’s essential for internet users because it ensures that their connections remain stable and dependable. In a world where many rely on networks for work and learning, reliability is crucial to avoid interruptions.

Q2. What are the four aspects of network reliability discussed in the article?

A2. The four aspects of network reliability discussed in the article are:

1. Fault tolerance
2. Scalability
3. Quality of Service (QoS)
4. Security

Q3. How does fault tolerance contribute to network reliability?

A3. Fault tolerance limits the impact of network failures and enables quick recovery. It does this by creating multiple paths for message transmission. If one path fails, the message is automatically rerouted through a different link, ensuring continuous service.

Q4. What is redundancy in the context of network architecture, and why is it important?

A4. Redundancy involves having multiple paths or backups in a network. It’s important because it helps maintain network reliability. When one path fails, data can still flow through an alternate route, minimizing disruptions.

Q5. What is the role of packet-switched networks in achieving fault tolerance?

A5. Packet-switched networks split data into packets and route them over a shared network. In case of a failure, packets can take different paths to reach the destination. This dynamic routing enhances fault tolerance.

Q6. What does scalability mean in network architecture, and why is it crucial for network growth?

A6. Scalability means the ability of a network to expand rapidly to support new users and applications without degrading existing services. It is crucial because it allows networks to grow without sacrificing performance.

Q7. How does adhering to standards and protocols contribute to network scalability?

A7. Adhering to standards and protocols allows hardware and software vendors to create products and services that can seamlessly integrate into existing networks. This promotes scalability as new components can easily be added without complex rule redesign.

Q8. Why is Quality of Service (QoS) important in modern networks, and what role does it play?

A8. QoS is essential because it ensures high-quality services, especially for data, voice, and video transmissions. It manages network congestion and prioritizes time-sensitive traffic, ensuring reliable content delivery.

Q9. How does QoS help manage congestion and ensure high-quality content delivery?

A9. When network demand exceeds available bandwidth, congestion can occur. QoS manages data and voice traffic flow, giving priority to time-sensitive content. This helps maintain the quality of services during congestion.

Q10. What are the key aspects of network security discussed in the article?

A10. The key aspects of network security discussed in the article are network infrastructure security and information security. Network infrastructure security involves physically securing devices and preventing unauthorized access. Information security safeguards data during transmission and on network-attached devices.

Q11. What are the two types of network security concerns that network administrators must address?

A11. Network administrators must address network infrastructure security and information security concerns. The former involves protecting the physical network components, while the latter focuses on safeguarding data and information.

Q12. What are the three fundamental prerequisites of network security mentioned in the article?

A12. The three fundamental prerequisites of network security are:

1. Confidentiality – Only authorized users can access and view data.
2. Integrity – Data remains unaltered during transmission.
3. Availability – Authorized users have prompt and reliable access to data services.

Q13. Can you explain the concepts of data confidentiality, integrity, and availability in network security?

A13. Data confidentiality ensures that only authorized users can access data. Data integrity ensures that data remains unchanged during transmission. Data availability ensures that authorized users can reliably access data services when needed.

Q14. How do administrators protect network infrastructure and information security?

A14. Network administrators protect infrastructure through physical security measures and preventing unauthorized access. They safeguard information security by employing software and hardware security and access controls, such as username and password protection.

Q15. What are some of the methods mentioned in the article for securing the network against unauthorized access?

A15. The article mentions methods like using username and password protection and employing software and hardware security measures to prevent unauthorized access to the network.