1. Connecting Device Repeater Hub Bridge Switch Router

2. Repeater –1 port to 1 port –signal amplification overcome signal attenuation –do not consider whether the signal need / need not to forward to the other side

3. In digital communication systems, a repeater is a device that receives a digital signal on an electromagnetic or optical transmission medium and regenerates the signal along the next leg of the medium. In electromagnetic media, repeaters overcome the attenuation caused by free-space electromagnetic-field divergence or cable loss. A series of repeaters make possible the extension of a signal over a distance. Repeaters remove the unwanted noise in an incoming signal. Unlike an analog signal, the original digital signal, even if weak or distorted, can be clearly perceived and restored. With analog transmission, signals are restrengthened with amplifiers which unfortunately also amplify noise as well as information.digitalsignalattenuationnoise analog From www.whatis.com : http://searchnetworking.techtarget.com/sDefinition/0,,sid 7_gci212890,00.htmlwww.whatis.com http://searchnetworking.techtarget.com/sDefinition/0,,sid 7_gci212890,00.html

4. Hub –multi ports to multi ports –signal amplification –do not consider whether the signal need / need not to forward to the other side one signal in multi signal out …. broadcast

5. Bridge –1 port to 1 port –Consider whether the signal need / need not to forward to the other side interconnect segments in a LAN

6. In telecommunication networks, a bridge is a product that connects a local area network (LAN) to another local area network that uses the same protocol (for example, Ethernet or Token Ring). You can envision a bridge as being a device that decides whether a message from you to someone else is going to the local area network in your building or to someone on the local area network in the building across the street. A bridge examines each message on a LAN, "passing" those known to be within the same LAN, and forwarding those known to be on the other interconnected LAN (or LANs).LANprotocolEthernetToken Ring From www.whatis.com : http://searchsecurity.techtarget.com/sDefinition/0,29066 0,sid14_gci211705,00.htmlwww.whatis.com http://searchsecurity.techtarget.com/sDefinition/0,29066 0,sid14_gci211705,00.html

7. Switch –multi-ports bridge –Consider whether the signal need / need not to forward to the other side no broadcast –With switching table inside which memorize connecting PC / devices

8. Router –With WAN port and LAN ports –used to connect multiple networks usually used to connect a LAN to the internet used to translate info from a LAN to the internet

9. A router is a device or, in some cases, software in a computer, that determines the next network point to which a packet should be forwarded toward its destination. The router is connected to at least two networks and decides which way to send each information packet based on its current understanding of the state of the networks it is connected to. A router is located at any gateway (where one network meets another), including each point-of- presence on the Internet. A router is often included as part of a network switch.packetgatewaypoint-of- presenceswitch A router may create or maintain a table of the available routes and their conditions and use this information along with distance and cost algorithms to determine the best route for a given packet. Typically, a packet may travel through a number of network points with routers before arriving at its destination. From www.whatis.com : http://searchsmb.techtarget.com/sDefinition/0,290660,sid44_gci212 924,00.htmlwww.whatis.com http://searchsmb.techtarget.com/sDefinition/0,290660,sid44_gci212 924,00.html

10. What is a NODE in a LAN ? A connection point for data transmission a node can be any device –workstation –server –connecting devices (hub / switch / router …)

11. What is a Carrier ? In phone lines / coaxial cable / STP / UTP –A carrier is an electromagnetic pulse –can be analogue or digital –when travel along a long distance its strength attenuate In Optical fibres –A carrier is a laser generated light ray –will not attenuate even after travels for a long distance