References. Slides are heavily based on, and contain content from: Technology in Action Eleventh Edition by Evans, Martin, and Poatsy

Transcription

1 Networks CSCI 101

2 References Slides are heavily based on, and contain content from: Technology in Action Eleventh Edition by Evans, Martin, and Poatsy

3 Computer Network Two or more computers connected via software and hardware so they can communicate with each other. Each device (e.g. computer) connected to a network is called a node.

4 Benefits of Networking Sharing an internet connection among devices Can share resources like printers Can share files Can share software

5 At home Family Network Daughters play online video games Son researches for homework Dad watches Netflix Mom looks for recipes on ipad

6 Speed of Data Transfer Bandwith: The max speed that data can be transmitted between nodes in a network. Throughput: Actual speed of data transmission that is achieved. Data transfer rates are traditionally measured in Mbps (Megabits per second)

7 Connecting Nodes Together In wired networks different types of cables are used based on how close the nodes are. Three types of cables are: Twisted-pair cable Coaxial cable Fiber-optic cable

8 Twisted-pair cable Copper wires twisted around each other Used for telephones An unshielded twisted-pair (UTP) is used for DSL networking

9 Twisted-pair cable History Created in 1881 by Alexander Graham Bell Telephones have two wires, one for sending the signal and one for receiving it Telephone wires shared same route as power lines Experienced electromagnetic interference or crosstalk from the magnetic field, e.g. hearing other peoples conversations

10 Twisted-pair cable They twisted the wires at each junction to resist the electro magnetic interference. Electro magnetic interference

11 Twisted-pair cables Two types: Unshielded and Shielded twisted pair. Shielded is less common, it has an insulating material around it that helps further resist the interference. Unshielded is the dominate cable.

12 Coaxial cable A single copper wire surrounded by layers of plastic and copper mesh. Used to connect cable TV and cable modems

13 Coaxial cable Co: Stands for together, coordination Axial: stands for axis All 4 cables share the same axis, all centered around the same point

14 Coaxial cable More expensive. Here you have 4 layers for one wire, where as with the twisted pair you had two. And the pieces are more expensive. There is less interference here, where as with the twisted-pair when you use it over long distances the interference gets magnified. Invented by Oliver Heaviside in 1880 All the shields reduce signal leakage.

15 Fiber-optic cable Most expensive, and most advanced Plastic or glass fibers that transmit data at extremely fast speeds. The glass will not produce or be altered by magnetic fields Can carry larger amounts of data over larger distances at higher speeds Used as the network backbone

16 Why have Fiber Optics not taken over? Producing glass as thin as hair, and to exact measurements is very costly More fragile since it s glass We are satisfied with what we have today

17 Wired Network Topologies HOW WE ARRANGE OUR COMPUTERS AND CONNECTIONS

18 Topologies Refer to the physical or logical arrangement of computers, cables, and other pieces of the network. Think of this like a floor plan. You want to arrange the equipment for optimal performance.

19 Point to Point Data travels from one note to another Very simple Supports two nodes

20 Bus Topology All computers connected on a sequence on a single cable.

21 Bus Topology This topology is less used now as it s not designed to easily support wireless Data Collisions can occur when two computers send out data on the same cable (the bus). Because of the setup Data Collisions are more common on Bus Topologies than others. To prevent data collisions an access method is established where the computer checks to see if data is being transmitted before it attempts to transmit.

22 Bus Topology Advantages: Uses minimal amount of cable Installation is easy, reliable, and inexpensive Disadvantages: Breaks in cable can disable the network Large number of nodes decreases performance, as a lot of data being transmitted on one bus

23 Ring Topology Computers are connected along a ring.

24 Ring Topology To avoid data collisions this topology uses a token. The token is passed around the ring until a computer takes hold of it. A computer can transmit data when it has the token, and will not give up the token until it is done transmitting.

25 Ring Topology When a computer transits data to another. The data is passed along from node to node, each node retransmitting until the data gets to it s destination. This topology is an active topology because the nodes are participating in transmitting the data.

26 Ring Topology Advantages: Allocates access to network fairly Performance remains ok with lots of nodes No collisions Disadvantage: Adding/removing nodes disables the network Low Redundancy: Failure of one node brings down the network Problems in data transmission can be a hard to find Can take longer to send data if on wrong side of the ring Security: Everyone can see your message, better encrypt it!

27 Equality In the Bus and Ring topologies all nodes are created equal. However, some noes are more important than others and this should be reflected in the topology.

28 Star Topology Nodes all connect to a switch.

29 Star Topology To send data from one node to another, it will first go to the switch, and the switch will direct the data to the correct receiving node. To avoid data collisions it uses CSMA/CD (Carrier Sense Multiple Access with Collision Detection). Here the node listens to make sure no data is being sent before it sends data.

30 Star Topology Advantages: Failure of one computer doesn t take down the whole network Easy to add nodes to this topology Performance is still good with lots of nodes The switch makes troubleshooting and repairs easier Disadvantage: If the switch fails, the system goes down Requires more cable, thus, can be more costly

31 Tree Topology

32 Tree Topology Here the nodes are connected to a central node, directly or indirectly. This creates structure, giving priority, and potentially restricting nodes to a certain area.

33 Tree Topology Advantages: Easy to add more nodes Easier to debug if parts of the network go down Each node has a direct connection to it s hub If one segment goes down the others don t Disadvantage: If the backbone fails, the network can cripple Can be hard to maintain as it grows.

34 Mesh Topology Every node is connected to every other node

35 Mesh Topology Advantages: Data can be going between different nodes at the same time If a node goes down it doesn t destroy the network Disadvantage: Redundancy Cost of all the cables Setting up and maintaining is difficult

36 Connecting to the Internet

37 The Modem Converts the internet signal coming in from the cable into a signal that your computer can understand. And vice versa when you re sending data out.

38 The Modem The modem connects to the wall for signal in and signal out. Typically, using your coaxial cable.

39 The Modem The modem then transfers the data to your computer by either Connecting to it directly using USB or Ethernet, or Connecting to a router which will allow multiple computers to connect, and a non-wired Wi-Fi connection.

40 The Router The router will take the connect given to it through the modem and split it such that multiple computers can connect.

41 The Router The modem will be connected to the router through Ethernet to a port that either says WAN (Wide Area Network) or Internet. Then your computers can directly connect with Ethernet wires or they can connect wirelessly as long as you have a wireless router.

42 The Router Even if you have only one computer that you can directly connect to the modem, it s still a good idea to have a router because it has a built in hardware firewall. The more firewalls you have, the better.

43 Your internet stopped working What do you do? Reset both the modem and the router by unplugging them from the power source, then wait sec and plug them back in. You may also want to reset you computer.

44 Wireless Networks DO WE HAVE OUR HEADS IN THE CLOUDS?

45 How does WI-FI work? Radio internet waves are sent out through your wireless router. Your computer was an internet card, and it picks up the signal.

46 Wireless Networks Wifi is the standard transmission using radio waves to connect nodes Wirless networks typically have decreased throughput when compared to wired networks because: More interference from magnetic and electronics Other people can get on your connections Metal and buildings can decrease your signal

47 Wireless Network Send and receive radio waves to / from router

48 Wired and Wireless Both wired and wireless connections can exist on the same network

49 Network Architectures DESIGNING YOUR NETWORK

50 Network Architecture The following list of Network Architectures are defined by the distance between nodes Personal Area Network (PAN) Local Area Network (LAN) Home Area Network (HAN) Metropolitan Area Network (MAN) Wide Area Network (WAN)

51 Personal Area Network A network designed for communication among devices for one person. E.g. Smartphone, to notebook, to tablet, can use Bluetooth and WIFI

52 Local Area Network A network where the nodes are located in a small geographical area. E.g. Computer lab at school, restaurant, house Home Area Network (HAN) is a specific type of LAN at your home.

53 Metropolitan Area Network A network designed to provide access to a larger geographical area like a city.

54 Wide Area Network Spans a large physical distance. The internet is the largest WAN. It s a collection of LANs.

55 Client/Server Network Centrally administrated network Client makes request to the server for information and resources Client Client Server Client Client Client

56 Peer-to-Peer (P2P) Network Every node can communicate directly with every other node. If a computer wants to print it communicates directly with the printer.