Networking Overview

Question 1

What is a network?

Answer 1

A network is two or more computer systems that are linked by a transmission medium and share one or more protocols that enable them to exchange data.

Question 2

Nodes

Answer 2

nodes are devices that send, receive, and forward data

Question 3

Links

Answer 3

links are the communications pathways between nodes

Question 4

Intermediate nodes

Answer 4

Intermediate nodes perform a forwarding function

Question 5

End system nodes (Hosts)

Answer 5

End system nodes are those that send and receive data traffic. End systems are often also referred to as hosts.

Question 6

Server

Answer 6

A Server is a End System Node that makes network applications and resources available to other hosts.

Question 7

Client

Answer 7

A Client is a End System Node that consumes the services provided by servers.

Question 8

Client-Server Network

Answer 8

A client-server network is one where some nodes, such as PCs, laptops, and smartphones, act mostly as clients. The servers are more powerful computers. Application services and resources are centrally provisioned, managed, and secured.

Question 9

Peer-to-Peer Network

Answer 9

A peer-to-peer network is one where each host acts as both client and server. This is a decentralized model where provision, management, and security of services and data are distributed around the network. A small peer-to-peer network can also be referred to as a workgroup.

Question 10

Appliances

Answer 10

Networks make use of many types of specialized platforms. Unlike general-purpose Windows or macOS computers and servers, an appliance is a computer with an operating system and software designed to perform a particular network role. Examples of these roles include the switches, routers, and wireless access points that forward data, the firewalls and intrusion detection systems that enforce security rules, and the load balancers and proxies that improve network performance.

Question 11

Applications

Answer 11

The nodes and links of networking infrastructure are deployed to run services. Services are shared applications that allow the network to do useful work, such as sharing files or allowing employees to send email.

Question 12

Function

Answer 12

Networks can be configured with additional properties to perform different functions. For example, the security properties of a virtual private network allow devices to join a local network from across the Internet. As another example, quality of service functionality allows optimization of a network to suit a particularly time-sensitive application, such as voice or video.

Question 13

local area network (LAN)

Answer 13

A local area network (LAN) is confined to a single geographical location. In a LAN, all nodes and segments are directly connected with cables or short-range wireless technologies. Most of the network infrastructure in a LAN would be directly owned and managed by a single organization. Some examples of LANs include the following:

• Home/residential network—With an Internet router and a few computers, plus mobile devices, gaming consoles, and printers.
• Small office/home office (SOHO) network—A business-oriented network possibly using a centralized server in addition to client devices and printers, but often still using a single Internet router/switch/access point to provide connectivity.
• Small and medium-sized enterprise (SME) Network—A network supporting dozens of users. Such networks would use structured cabling and multiple switches and routers to provide connectivity.
• Enterprise LAN—A larger network with hundreds or thousands of servers and clients. Such networks would require multiple enterprise-class switch and router appliances to maintain performance levels.
• Datacenter—A network that hosts only servers and storage, not end user client devices.

Question 14

wide area network (WAN)

Answer 14

A wide area network (WAN) is a network of networks, connected by long-distance links. A typical enterprise WAN would connect a main office site with multiple branch office sites, possibly in different countries. A WAN could link two or more large LANs or could be used for remote workers connecting to an enterprise network via a public network such as the Internet. WAN links are also used to connect datacenters to one another. WANs are likely to use leased network devices and links, operated and managed by a service provider.

Question 15

Network type

Answer 15

A network type refers primarily to its size and scope. The size of a network can be measured as the number of nodes, while the scope refers to the area over which nodes sharing the same network address are distributed.

Question 16

Topology

Answer 16

Where the type defines the network scope, the topology describes the physical or logical structure of the network in terms of nodes and links.

Question 17

Point-to-Point Topology

Answer 17

In the simplest type of topology, a single link is established between two nodes. This is called a point to point link. Because only two devices share the connection, they are guaranteed a level of bandwidth.

Physical point to point topologies using different media types for half-duplex and duplex communications.

Question 18

Half Duplex

Answer 18

When the network media is halp-duplex, a node cannot transmit and receive at the same time.

Question 19

Full Duplex

Answer 19

When the network media is full-duplex, nodes can transmit and receive simultaneously.

Question 20

Star Topology

Answer 20

In a star topology each endpoint node is connected to a central forwarding appliance, such as a switch or router. The central node mediates communications between the endpoints. The star topology is the most widely used physical topology. For example, a typical SOHO network is based around a single Internet router appliance that clients can connect to with a cable or wirelessly. The star topology is easy to reconfigure and easy to troubleshoot because all data goes through a central point, which can be used to monitor and manage the network. Faults are automatically isolated to the media, node (network card), or the switch, router, or wireless access point at the center of the star.

You may also encounter the hub-and-spoke topology, which has the same physical layout as a star topology but is primarily used in a different context. While the star topology is often seen in local area networks (LANs), the hub-and-spoke topology is more commonly applied to wide area networks (WANs) with remote sites.

Question 21

Mesh Topology.

Answer 21

A mesh topology is commonly used in WANs, especially public networks such as the Internet. A full mesh network requires that each device has a point to point link with every other device on the network. This approach is normally impractical, however. The number of links required by a full mesh is expressed as n(n–1)/2, where n is the number of nodes. For example, a network of just four nodes would require six links, while a network of 40 nodes would need 780 links! Consequently, a hybrid approach is often used, with only the most important devices interconnected in the mesh, perhaps with extra links for fault tolerance and redundancy. This type of topology is referred to as a partial mesh.

Mesh networks provide excellent redundancy, because other routes, via intermediary devices, are available between locations if a link failure occurs.

Question 22

Network Protocol

Answer 22

A network protocol is a set of rules for exchanging data in a structured format A network protocol has two principal functions:

• Addressing—Describing where data messages should go. At each OSI model layer, there are different mechanisms for identifying nodes and rules for how they can send and receive messages.
• Encapsulation—Describing how data messages should be packaged for transmission. Encapsulation is like an envelope for a letter, with the distinction that each layer requires its own envelope. At each layer, the protocol adds fields in a header to whatever payload data it receives from an application or other protocol.