Computer Networks

 Which is the best definition of a circuit switched network?  An electric circuit where the connections get switched based on who is calling whom at a given moment

 What is a digital packet?  Computers separate the information they want to send across a network into smaller pieces called packets that travel along different routes to their destination

 What is EMI?  Electromagnetic interference is produced by electromagnetic waves from electromagnetic devices that can degrade the signal your computer or computer monitor received  Examples of electromagnetic devices include: cell phones, cordless phones, pagers, electric space heaters, other motorized devices

 What is RFI?  Radio frequency interference is an unwanted radio signal that prevents clear reception and can degrade the signal your computer or computer monitor receives  It is typically caused by garage door openers, remote control devices, AM and FM radios and antennas

 1. They are used in networks that need to send messages across longer distances than the wires themselves can carry the message (booster)  2. They have all of the abilities of a router, plus they can translate between network protocols (gateway)  3. They do not read MAC addresses, so they send data packets to all the computers on the network (hub)

 4. Directs incoming messages to the right computer and directs outgoing messages to the fastest route to their destination (switch).  5. A circuit board that allows you to plug in an Ethernet cable and connect your computer to a network or the internet (network interface card)  6. Smarter versions of hubs that can read the MAC addresses attached to data packets (router)

 Which of the following statements are true about digital signals?  Computer systems use binary code to communicate  Ones and zeros are strung together to form instructions to the computer  Computer networks use electric pulses across wire to communicate  The ups and down in the waveform show changes in frequency  All of the above (correct answer)

 Which of the following statements is true about analog signals?  In the world around us, very few sounds are actually analog sounds (not true)  Early cell phone systems used digital radio waves to transmit voice signals (not true)  Analog signal is a wave pattern that is not continuously variable (not true)  Digital cell phones compress your voice into analog information (not true)  Modems are used to connect computers to the Internet via analog phone lines (True)

Star topology connects computers using a hub or a switch. Very common; easy to design and implement Advantages: simplicity of adding additional nodes. Disadvantage: hub represents a single point of failure. Ring topology is no longer common. The network sends a token around the ring and only one computer can hold the token at once. Only the computer holding the token can send information. Disadvantages: switches are smarter at routing data to specific addresses With Bus topology every computer taps into a central cable. Advantages: easy to connect and requires less cable than star. Used mostly on large scale networks to connect smaller networks. Disadvantages: if the central cable breaks it divides the network into two separate sections. Full mesh topology links every device to every other one. Advantages: has the highest fault tolerance of all the networks. Disadvantages: costly, more complex. Rarely used today. WAN implementations sometime use a partial mesh where all computers can connect to all others by going through no more than a few nodes.

 You will be asked to design a small LAN for a T-shirt company. You will have to recommend which network topology will work best and explain why.  You will also have to decide whether client/server to peer-to-peer network would be best and describe the features and benefits of each.

 In client/server networks, one computer is set up to function only as a server.  The server controls the access that other computers have to shared resources such as files and folders that are stored on the server. Employees folders can be password protected.  The network administrator can back up documents that are stored on a server more easily. If one of the computers crashes, the information is still available on the server.  Some servers perform multiple tasks such as storing and retrieving documents, serving up Web pages, printing, or allowing employees to access .

 On peer-to-peer networks all computers have equal ability to communicate and control documents.  All computers can share files with others, request files from other computers, and access office machines such as printers.  Security is typically controlled by the end user (the employee who used the computer) who configures who can see what on his/her computer.

 List the seven layers of the OSI Seven Layer Model starting with layer 1:  Physical  Data Link  Network  Transport  Session  Presentation  Application

 Write a short essay that describes the process that takes place at the layer of the OSI Seven Layer model for which you made a collage. State the imagery you used, the process, and the layer devices and protocols used at that layer.