Exploring the Functions of Networking Flashcards
Which are most common to people, fall into the category of endpoints. In the context of a network, end devices are called end-user devices, and include PCs, laptops, tablets, mobile phones, game consoles, and television sets. Endpoints are also file servers, printers, sensors, cameras, manufacturing robots, smart home components, and so on. At the beginning of computer networking, all end devices were physical hardware units. Today, many end devices are virtualized, meaning that they do not exist as separate hardware units any more. In virtualization, one physical device is used to emulate multiple end devices, for example all the hardware components that one end device would require. The emulated computer system operates as if it were a separate physical unit and has its own operating system and other required software. In a way, it behaves like a tenant living inside a host physical device, using its resources (processor power, memory, and network interface capabilities) to perform its functions. Virtualization is commonly applied for servers to optimize resource utilization, as server resources are often underutilized when they are implemented as separate physical units.
Endpoints Devices
These devices interconnect end devices or interconnect networks. In doing so, they perform different functions, which include regenerating and retransmitting signals, choosing the best paths between networks, classifying and forwarding data according to priorities, filtering traffic to allow or deny it based on security settings, and so on. As endpoints can be virtualized, so can intermediary devices or even entire networks. The concept is the same as in the endpoint virtualization—the virtualized element uses a subset of resources available at the physical host system.
Intermediary devices
These devices enable multiple endpoints such as PCs, file servers, printers, sensors, cameras, and manufacturing robots to connect to the network. Switches are used to allow devices to communicate on the same network. In general, a switch or group of interconnected switches attempt to forward messages from the sender so it is only received by the destination device. Usually, all the devices that connect to a single switch or a group of interconnected switches belong to a common network and can therefore communicate directly with each other. If an end device wants to communicate with a device that is on a different network, then it requires “services” of a device that is known as a router, which connects different networks together.
Switches
These devices connect networks and intelligently choose the best paths between networks. Their main function is to route traffic from one network to another. For example, you need a router to connect your office network to the internet. An analogy that may help you understand the basic function of switches and routers is to imagine a network as a neighborhood. A switch is the street which connects the houses, and routers are the crossroads of those streets. The crossroads contain helpful information such as road signs, to help you in finding a destination address. Sometimes, you might need the destination after just one crossroad, but other times you might need to cross several. The same is true in networking. Data sometimes “stops” at several routers, before it is delivered to the final recipient. Certain switches combine functionalities of routers and switches and they are called Layer 3 switches.
Routes
These devices allow wireless devices to connect to a wired network. An AP usually connects to a switch as a standalone device, but it also can be an integral component of the router itself.
Access Points
These devices are used by network administrators or network operations centers to facilitate management of many APs. The WLC automatically manages the configuration of wireless APs.
WLC (Wireless LAN Controllers)
Firewalls are network security systems that monitor and control the incoming and outgoing network traffic based on predetermined security rules. A firewall typically establishes a barrier between a trusted, secure internal network, and another outside network, such as the internet, that is assumed not to be secure or trusted. The term next-generation firewall indicates a firewall that provides additional features to accommodate the newest security requirements. An example of such a feature is the ability to recognize user applications, for instance a game running inside an application, such as a browser, that is connected to Facebook.
Next-generation firewalls (NGFW)
An IPS is a system that performs deep analysis of network traffic, searching for signs that behavior is suspicious or malicious. If the IPS detects such behavior, it can take protective action immediately. An IPS and a firewall can work in conjunction to defend a network.
Intrusion Protection System (IPS)
A modern management service offers centralized management that facilitates designing, provisioning, and applying policies across a network. It includes features for discovery and management of network inventory, management of software images, device configuration automation, network diagnostics, and policy configuration. It provides end-to-end network visibility and uses network insights to optimize the network. An example of such centralized management service is Cisco DNA Center.
Management Services
A network topology is the arrangement of its elements. Topologies give insight into physical connections and data flows among devices. In a carefully designed network, data flows are optimized and the network performs as desired.
Topology
Bitrate is a measure of the data rate in bits per second of a given link in the network. The unit of bitrate is bit per second (bps). This measure is often referred to as bandwidth, or speed in device configurations, which is sometimes thought of as speed. However, it is not about how fast 1 bit is transmitted over a link—which is determined by the physical properties of the medium that propagates the signal—it is about the number of bits transmitted in a second. Link bitrates commonly encountered today are one and 10 Gigabits per second (1 or 10 billion bits per second). 100-Gbps links are not uncommon either.
Bitrate or Bandwidth
Indicates how much time a network is accessible and operational. Availability is expressed in terms of the percentage of time the network is operational. This percentage is calculated as a ratio of the time in minutes that the network is actually available and the total number of minutes over an agreed period, multiplied by 100. In other words, availability is the ratio of uptime and total time, expressed in percentage. To ensure high availability, networks should be designed to limit the impact of failures and to allow quick recovery when a failure does occur. High availability design usually incorporates redundancy. Redundant design includes extra elements, which serve as back-ups to the primary elements and take over the functionality if the primary element fails. Examples include redundant links, components, and devices.
Availability
Indicates how well the network operates. It considers the ability of a network to operate without failures and with the intended performance for a specified time period. In other words, it tells you how much you can count on the network to operate as you expect it to. For a network to be reliable, the reliability of all its components should be considered. Highly reliable networks are highly available, but a highly available network might not be highly reliable—its components might operate, but at lower performance levels. A common measure of reliability is the mean time between failures (MTBF), which is calculated as the ratio between the total time in service and the number of failures, where not meeting the required performance level is considered a failure. Choosing highly reliable redundant components in the network design increases both availability and reliability.
Reliability
Indicates how easily the network can accommodate more users and data transmission requirements, without affecting current network performance. If you design and optimize a network only for the current requirements, it can be very expensive and difficult to meet new needs when the network grows.
Scalability
Tells you how well the network is defended from potential threats. Both network infrastructure and the information that is transmitted over the network should be secured. The subject of security is important, and defense techniques and practices are constantly evolving. You should consider security whenever you take actions that affect the network.
Security
