1. Confidentiality/date line: 13pt Arial Regular, white Maximum length: 1 line Information separated by vertical strokes, with two spaces on either side Disclaimer information may also be appear in this area. Place flush left, aligned at bottom, 8-10pt Arial Regular, white Indications in green = Live content Indications in white = Edit in master Indications in blue = Locked elements Indications in black = Optional elements Copyright: 10pt Arial Regular, white Passage Two. Networking Hardware and Topology

2. Training target: In this part ， our target is to train your reading speed. You should pay more attention to” word group”. Treating a group of words as a whole unit is a short cut to save your time. We have underlined the word groups in some sentences ， and the rest can be practiced by yourself. If there are some new words ， you may cover the note area with a piece of paper and try to guess their meanings without looking them up in the dictionary.

3.  Text  1.Networking hardware  Networking hardware includes all computers ， peripherals ， interface cards and other equipments needed to perform data-processing and communications within the network. Let’s look some networking hardwares.

4. ..  （ 1 ） Network Interface Card （ NIC ） :The network interface card provides the physical connection between the network and the computer workstation. Most NICs are internal ， with the card fitting into an expansion slot inside the computer. NIC is a major factor in determining the speed and performance of a network. It is a good idea to use the fastest network card available for the type of workstation you are using.

5. .  （ 2 ） Switch （ concentrator ） :A switch is a device that provides a central connection point for cables from workstations ， servers and peripherals. In a star topology ， twisted-pair is run from each workstation to a central switch. Switches electrically amplify the signal as it moves from one device to another. Switches no longer broadcast network packets as hubs did in the past ， they memorize the addresses of computers and send the information to the correct location directly.

6. .  （ 3 ） Repeater: Since a signal loses strength as it passes along a cable ， it is often necessary to boost the signal with a device called a repeater. The repeater electrically amplifies the signal it receive  s and rebroadcasts it. Repeaters can be separate devices or they can be incorporated into a concentrator. They are used when the total length of your network cable exceeds the standards set for the type of cable being used.

7.  （ 4 ） Bridge: A bridge is a device that allows you to segment a large network into two smaller ， more efficient networks. Bridges can be used to connect different types of cable ， or physical topologies. They must ， however ， be used between networks with the same protocol. Bridges are store-and-forward devices. A bridge accepts an entire frame and passes it up to the data link layer where the checksum is verified. Then the frame is sent down to the physical layer for forwarding on a different network. Bridges can make minor changes to the frame before forwarding it ， such as adding or deleting some fields from the frame header.

8. .  A bridge monitors the information traffic on both sides of the network so that it can pass packets of information to the correct location. Most bridges can “listen” to the network and automatically figure out the address of each computer on both sides of the bridge. You might say that the bridge is like a traffic cop at a busy intersection during rush. It keeps information flowing on both sides of the network ， but it doesn’t allow unnecessary traffic through.

9. .  （ 5 ） Router: A router translates information from one network to another; it is similar to a super intelligent bridge. Routers can direct traffic to prevent head-on collisions. Routers know the addresses of computers ， bridges and other routers on the network. Based on the destination address and origin ， routers can even “listen” to the entire network to determine which sections are busiest ， then select the best path to route a message.

10.  （ 6 ） Gateway: A gateway can translate information between different network data formats or network architectures. It can translate TCP/IP to AppleTalk so computers supporting TCP/IP can communicate with Apple brand computers. Most gateways operate at the application layer ， but can operate at the network or session layer of the OSI model.

11.  2.Network topology  Every network has a “shape” which is normally referred to as its topology. There are five major topologies in use today: Bus ， Ring ， Star ， Tree ， and Mesh. Each is used for specific network types ， although some network types can use more than one topology.

12.  （ 1 ） Bus:The simplest topology to understand is the Bus.In a Bus ， all the devices on the network are connected to a common cable.Normally ， this cable is terminated at either end ， and can never be allowed to form a closed loop.Pic6.4shows an example of a Bus network.  Pic6.4 Bus network

13.  （ 2 ） Ring:A Ring topology is very similar to a Bus.In a Ring ， all the devices on the network are connected to a common cable which loops from machine to machine.After the last machine on the network ， the cable then returns to the first device to form a closed loop.Pic6.5shows an example of a Ring network.  Pic6.5 Ring Topology

14.  （ 3 ） Star: A Star topology is completely different from either a Bus or a Ring. In a Star ， each device has its own cable run connecting the device to a common hub or concentrator. Only one device is permitted to use each port on the hub.Pic6.6shows an example of a Star network.  Pic6.6 Star Topology

15.  （ 4 ） Tree: A Tree topology can be thought of as being a “Star of Stars ”network. In a Tree network ， each device is connected to its own port on a hierarchical concentrator in the same manner as in a Star. However ， concentrators are connected together in a hierarchical manner.  Pic6.7shows a  Tree network.

16.  （ 5 ） Mesh: A Mesh topology consists of a network where every device on the network is physically connected to every other device on the network. This provides a great deal of performance and reliability ， however ， the complexity and difficulty of creating one increases geometrically as the number of nodes on the network increases.Pic6.8shows an example of a four-node Mesh network.  Pic6.8a four-node Mesh  network geometrically

17. .  Key words  NIC 网卡 bridge 网桥  repeater 中继器 topology 拓扑结构  Ring network 环型网络  Tree network 树型网络  switch 交换机 router 路由器 gateway 网关  Bus network 总线型网络  Star network 星型网络 Mesh network 网型网络  OSI:Open System Interconnection 开放系统互联（一种网络体系结构）  TCP/IP:Transmission Control Protocol/Internet Protocol 传输控制协议 / 网际协议（一个协议集、一种网络体系结构）

18. .  The End