HPFOCUS

Exploring the Functions of Networking

What Is a Network?

Common Physical Components of a Network

Interpreting a Network Diagram

Resource-Sharing Functions and Benefits

Data and applications
Resources
Network storage
Backup devices

Network User Applications

E-mail (Outlook, POP3, Yahoo, and so on)
Web browser (IE, Firefox, and so on)
Instant messaging (Yahoo IM, Microsoft Messenger, and so on)
Collaboration (Whiteboard, Netmeeting, WebEx, and so on)
Databases (file servers)

Impact of User Applications on the Network

Batch applications
FTP, TFTP, inventory updates
No direct human interaction
Bandwidth important, but not critical

Interactive applications
Inventory inquiries, database updates.
Human-to-machine interaction.
Because a human is waiting for a response, response time is important but not critical, unless the wait becomes excessive.

Real-time applications
VoIP, video
Human-to-human interaction
End-to-end latency critical

Characteristics of a Network

Speed
Cost
Security
Availability
Scalability
Reliability
Topology

Physical Topology Categories
Logical Topologies
Bus Topology

All devices receive the signal.
Star Topology

Transmission through a central point.
Single point of failure.
Extended-Star Topology

More resilient than star topology.
Ring Topology

Signals travel around ring.
Single point of failure.
Dual-Ring Topology

Signals travel in opposite directions.
More resilient than single ring.
Full-Mesh Topology

Highly fault-tolerant
Expensive to implement
Partial-Mesh Topology

Trade-off between fault tolerance and cost

Connection to the Internet

Summary

A network is a connected collection of devices that can communicate with each other. Networks carry data in many kinds of environments, including homes, small businesses, and large enterprises.

There are four major categories of physical components in a computer network: the computer, interconnections, switches, and routers.

Networks are depicted graphically using a set of standard icons.

The major resources that are shared in a computer network include data and applications, peripherals, storage devices, and backup devices.

The most common network user applications include e-mail, web browsers, instant messaging, collaboration, and databases.

User applications affect the network by consuming network resources.

The ways in which networks can be described include characteristics that address network performance and structure: speed, cost, security, availability, scalability, reliability, and topology.

A physical topology describes the layout for wiring the physical devices, while a logical topology describes how information flows through a network.

In a physical bus topology, a single cable effectively connects all the devices.

In a physical star topology, each device in the network is connected to the central device with its own cable.

When a star network is expanded to include additional networking devices that are connected to the main networking device, it is called an extended-star topology.

In a ring topology, all the hosts are connected in the form of a ring or circle. In a dual-ring topology, there are two rings to provide redundancy in the network.

A full-mesh topology connects all devices to each other; in a partial-mesh topology, at least one device has multiple connections to all other devices.

There are three common methods of connecting the small office to the Internet: DSL using the existing telephone lines, cable using the CATV infrastructure, and serial links using the classic digital local loops.