Networking Basics

1. SECTION 7A • Networking • Basics

2. 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

3. 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。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。

4. The Uses of a Network • A network connects computers so they can communicate, exchange information, and share resources. • The main benefits of using a network are: • Simultaneous Access • Shared Peripheral Devices • Personal Communication • Easier Backup

5. The Uses of a Network - Simultaneous Access • 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.

6. Read/write Read/write Read/write Read/write Read/write 使用者可共享儲存在中央檔案伺服器的資料。 Read only

7. The Uses of a Network - Simultaneous Access • 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.

8. 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

9. 使用應用程式的網路版。

10. The Uses of a Network - Shared Peripheral Devices • 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.

11. The Uses of a Network - Personal Communication • 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.

12. 1 2 3 4 在一般的網路上傳送與接收電子郵件。

13. 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。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。

14. 參加線上視訊會議。

15. The Uses of a Network - Easier Backup • 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.

16. 備份系統可用來備份網路上的伺服器以及每部個人電腦。備份系統可用來備份網路上的伺服器以及每部個人電腦。

17. How Networks are Structured • 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

18. How Networks are Structured – Local Area Networks (LANs) • 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.

19. 電子郵件信息被分割到封包內。

20. How Networks are Structured – Well-Known Protocols • 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.

21. How Networks are Structured – Connecting Devices • 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.

22. How Networks are Structured – Network Connections • 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.

23. Type A header Type A header Type A header Payload Payload Payload LAN 1 LAN 2 WAN ROUTER ROUTER Significant geographical distance SERVER SERVER

24. 1 2 3 A gateway performs the translation between two different types of networks.

25. How Networks are Structured – Campus Area Networks (CANs) • A CAN follows the same principles as a local area network, only on a larger and more diversified one.

26. How Networks are Structured – Metropolitan Area Networks (WANs) • A MAN is a large-scale network that connects multiple corporate LANs together.

27. How Networks are Structured – Wide 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.

28. 都會網路和網域網路及區域網路間的使用

29. How Networks are Structured – Server-Based Networks • 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.

30. 含有檔案伺服器的簡單型LAN

31. How Networks are Structured – Client/Server Networks • 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.

32. 1 2 3 在客戶 / 伺服器電腦環境模式下的分散處理。

33. How Networks are Structured – Peer-to-Peer Networks • 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.

34. P2P (Peer-to-Peer)

35. Network Topologies for LANs (Option) A network's topology is the layout of the cables and devices that connect the nodes. The four most common network topologies are: • 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.

36. Network Topologies for LANs (Cont.) (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.

37. Network Media and Hardware (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.

38. Network Technologies • 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

39. Network Software • 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: • Novell NetWare • Microsoft Windows NT Server • Microsoft Windows 2000 • Microsoft XP • Microsoft .NET Server • Linux

40. Section 7a review • 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.