NetworkingBasics

SECTION 7A

This lesson includes the following sections:

• The Uses of a Network

• How Networks are Structured

• Network Topologies for LANs

• Network Media and Hardware

• Network Software

大多數的辦公室幾乎在每個辦公桌上都有一部 PC。這些電腦彼此連線而構成一個網路。

• Simultaneous Access

• Shared Peripheral Devices

• Personal Communication

• Easier Backup

A network connects computers so they can communicate, exchange information, and share resources.

The main benefits of using a network are:

The Uses of a Network

• In organizations, many people may need to use the same data or programs. A network solves this problem.

• Shared data and programs can be stored on a central network server. A server that stores data files may be called a file server.

• Managers may assign access rights to users. Some users may only be able to read data, others may be able to make changes to existing files.

The Uses of a Network - Simultaneous Access

Read/writeRead/writeRead/writeRead/writeRead/writeRead only

使用者可共享儲存在中央檔案伺服器的資料。

• In an environment where PCs are not networked, a separate copy of each program must be installed on every computer. However, this would be costly.

•Software can be expensive, especially when you must buy many copies•Installing and configuring a program on many different computers can take a lot of time and labor, and maintaining many separate installations of a program is an ongoing expensive.

The Uses of a Network - Simultaneous Access

• Solution•Site Licenses: buy a single copy (or a few copies) of an application and pays the developer for a license to copy the application onto a specified number of computers•Network Versions: connect users’ computers to a central network server and enable users to share a network version of a program

•In network version, only one copy of the application is stored on the server, with a minimum number of supported files copies to each user’s PC

The Uses of a Network - Simultaneous Access

使用應用程式的網路版。

• Because peripheral (external) devices like printers can be expensive, it is cost-effective to connect a device to a network so users can share it.

• Through a process called spooling, users can send multiple documents (called print jobs) to a networked printer at the same time. The documents are temporarily stored on the server and printed in turn.

The Uses of a Network -Shared Peripheral Devices

• One of the most common uses of networks is for electronic mail (e-mail).

• An e-mail system enables users to exchange written messages (often with data files attached) across the local network or over the Internet.

• Two other popular network-based communications systems are teleconferencing and videoconferencing.

The Uses of a Network - Personal Communication

1 2 3 4

在一般的網路上傳送與接收電子郵件。

貼附一份文件到電子郵件信息上，是一種與其他人交換檔案的簡單方法。

參加線上視訊會議。

• Networks enable managers to easily back up (make backup copies of) important data.

• Administrators commonly back up shared data files stored on the server, but may also use the network to back up files on users' PCs.

The Uses of a Network - Easier Backup

備份系統可用來備份網路上的伺服器以及每部個人電腦。

• Local Area Networks (LANs)• Campus Area Networks (CANs)• Metropolitan Area Networks (MANs)• Wide Area Networks (WANs)• Server-Based Networks• Client/Server Networks• Peer-to-Peer Networks

How Networks are Structured

• A LAN is a network whose computers are located relatively near one another. The nodes may be connected by a cable, infrared link, or small transmitters.

• A network transmits data among computers by breaking it into small pieces, called packets.

• Every LAN uses a protocol – a set of rules that governs how packets are configured and transmitted.

How Networks are Structured – Local Area Networks (LANs)

電子郵件信息被分割到封包內。

• TCP/IP: the protocol of the internet and the default networking protocol of almost operating systems.

• IPX/SPX: A proprietary protocol of Novell for NetWare network operating system.

• NetBEUI: Excellent protocol for networking small offices but does not expand well into larger environment.

How Networks are Structured – Well-Known Protocols

• Hub: a hub is a simple connection point for different type of devices on a network

• Bridge: a bridge is a device that looks at the information in each packet header and forwards data that is traveling from one LAN to another

• Router: a router is a more complicated device that stores the routing information for packets. Like bridge, a router looks at each packet’s header to determine where the packet should go and then determines a route for the packet to reach its destination.

How Networks are Structured – Connecting Devices

• If two LAN are built around the same communication rules, then they can be connected by

•Bridge: forward data from one LAN to another•Router: A more complicated devices that store the routing information for networks. (Next page)

• If different networks are connected•Gateway: connects two network and translate information from one to the other.

How Networks are Structured – Network Connections

LAN 1

WAN

LAN 2

Type Aheader

Payload Type Aheader

Payload

Type Aheader

Payload

Significantgeographical

distance

ROUTER ROUTER

SERVER SERVER

A gateway performs the translationbetween two different types of networks.

1

2

3

• A CAN follows the same principles as a local area network, only on a larger and more diversified one.

How Networks are Structured – Campus Area Networks (CANs)

• A MAN is a large-scale network that connects multiple corporate LANs together.

How Networks are Structured – Metropolitan Area Networks (WANs)

• Multiple LANs can be connected together using devices such as bridges, routers, or gateways, which enable them to share data.

• A WAN is two or more LANs connected together. The LANs can be many miles apart.

• To cover great distances, WANs may transmit data over leased high-speed phone lines or wireless links such as satellites.

How Networks are Structured – Wide Area Networks (WANs)

都會網路和網域網路及區域網路間的使用

• In addition to the individual users' PCs (nodes), many networks use a central computer, called a server.

• A server has a large hard disk for shared storage. It may provide other services to the nodes, as well.

• In a file server network, nodes can access files on the server, but not necessarily on other nodes.

How Networks are Structured – Server-Based Networks

含有檔案伺服器的簡單型 LAN

• A popular type of server-based network

• In client/server computing, individual nodes share the processing and storage workload with the

server.

• Client/server networks require specialized software that enables nodes and the server to collaborate on processing and storage, but no special type of network hardware.

How Networks are Structured – Client/Server Networks

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2

3

在客戶 / 伺服器電腦環境模式下的分散處理。

• In a peer-to-peer network, all nodes have an equal relation to one another.

• Each node usually has access to some resources on other nodes, so users can share files, programs, or devices on other users' systems.

• Some peer-to-peer networks use a server, but some do not.

How Networks are Structured – Peer-to-Peer Networks

P2P (Peer-to-Peer)

• Bus. •Each node is connected in series along a single line. •At end node, a terminator is attached to prevent signal bounce back.

• Star. •The most common topology in use today.•All nodes are connected to a central hub.

A network's topology is the layout of the cables and devices that connect the nodes. The four most common network topologies are:

Network Topologies for LANs (Option)

• Ring. •Nodes are connected in a circular chain, with the conduit beginning and ending at the same computer.•No danger of collisions because only one packet of data may traverse the ring at a time

•By Token

• Mesh. •Each node has a separate connection to every other node. •The least used network topology.•The most expensive to implement.

Network Topologies for LANs (Cont.) (Option)

• In a network, the media are the wires, cables and other means by which data travels from its source to its destination.

• The most common network media are twisted-pair cable, coaxial cable, fiber-optic cable, and wireless links.

• Each node uses a special device, called a network interface card (NIC). The card connects to the network media and controls the flow of data.

• NICs must use a common network technology to communicate. The most popular network technologies for LANs are Ethernet, Fast Ethernet, and Token Ring.

Network Media and Hardware (Option)

• Ethernet: •10 Mbps•Original use coaxial cable (10Base-5 and 10Base-2)•Now use twisted-pair called 10Base-T by star technology

• Fast Ethernet (also called 100Base-T)•100 Mbps

• Gigabit Ethernet

• Token Ring•Proposed by IBM•Once hold token, a node can then transmit data

Network Technologies

• Novell NetWare

• Microsoft Windows NT Server

• Microsoft Windows 2000

• Microsoft XP

• Microsoft .NET Server

• Linux

A network operating system (NOS) is the group of programs that manages the resources on a network.

Common network operating systems for PC-based networks include:

Network Software

• List the four benefits of using a network.

• Differentiate between LANs and WANs.

• Identify three common network topologies.

• Name four common network media.

• List four examples of network operating systems.

Section 7a review