Table of Contents Link to heading

• Network Architecture
• Fault Tolerance
• Scalability
• Quality of Service (QoS)
• Security
• Network Architecture Requirements

Network Architecture Link to heading

the technologies that support the infrastructure and the programmed services and rules, or protocols, that move data across the network.

Networks must support a wide range of applications and services, as well as operate over many different types of cables and devices, which make up the physical infrastructure.

There are four basic characteristics that the underlying architectures need to address in order to meet user expectations:

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

Fault Tolerance Link to heading

limits the impact of a failure, so that the fewest number of devices are affected.

The expectation is that the Internet is always available to the millions of users who rely on it. This requires a network architecture that is built to be fault tolerant. It is also built in a way that allows 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 can be instantly sent over a different link. Having multiple paths to a destination is known as redundancy.

One way reliable networks provide redundancy 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 destination.

Reasons for packet-switched technology to be chosen for the development of the Internet:

1. Network devices dynamically decide on the best available path to forward each packet.
2. It can rapidly adapt to the failure of network devices and communication links.
3. Data packets can travel though the network using multiple different paths.

This is not the case in circuit-switched networks traditionally used for voice communications. A circuit-switched network is one that establishes a dedicated circuit between the source and destination before the users may communicate. If the call is unexpectedly terminated, the users must initiate a new connection.

Scalability Link to heading

ability to expand quickly to support new users and applications without degrading the performance of the service being delivered to existing users.

Networks are scalable because the designers follow accepted standards and protocols. This allows software and hardware vendors to focus on improving products and services without worrying about designing a new set of rules for operating within the network.

Quality of Service (QoS) Link to heading

managed by the router, ensures that priorities are matched with the type of communication and its importance to the organisation.

New applications available to users over internetworks, such as voice and live video transmissions, create higher expectations for the quality of the delivered services. As data, voice, and video content continue to 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 the number of bits that can be transmitted in a single second, or 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 queue, or hold, the packets in memory until resources become available to transmit them.

For example, one user is requesting a web page and another is on a phone call. 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.

Examples of priority decisions for an organisation might include:

1. Time-sensitive communication - increase priority for services like telephony or video distribution.
2. Non time-sensitive communication - decrease priority for web page retrieval or email.
3. High importance to organisation - increase priority for production control or business transaction data.
4. Undesirable communication - decrease priority or block unwanted activity, like peer-to-peer file sharing or live entertainment.

Security Link to heading

The network infrastructure, services, and the data contained on network-attached devices are crucial personal and business assets. There are two types of network security concerns that must be addressed: network infrastructure security and information security.

Network infrastructure security refers to the physical securing of devices that provide network connectivity, and preventing unauthorised access to the management software that resides on them.

Information security refers to protecting the information contained within the packets being transmitted over the network and the information stored on network attached devices. In order to achieve the goals of network security, there are three primary requirements for data:

1. Confidentiality - only the intended and authorised recipients can access and read data.
2. Integrity - having the assurance that the information has not been altered in transmission, from origin to destination.
3. Availability - having the assurance of timely and reliable access to data services for authorised users.

Network Architecture Requirements Link to heading