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Introduction to Computer Networking

Introduction to Computer Networking. Definition. Network Any interconnected group or system. Multiple computers and other devices connected together to share information. (nodes). History. 1957 USSR launches Sputnik, first artificial earth satellite 1958

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Introduction to Computer Networking

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  1. Introduction to Computer Networking

  2. Definition • Network • Any interconnected group or system. • Multiple computers and other devices connected together to share information. (nodes)

  3. History • 1957 • USSR launches Sputnik, first artificial earth satellite • 1958 • US forms the ARPA (Advanced Research Projects Agency) for their military to have an edge on science and technology

  4. History • 1962 • Paul Baran invented Packet Switching – breaking digital messages into bite-size chunks which can easily be sent to computer • 1969 • A four node computer system called Arpanet was developed • First electronic message was sent

  5. History • 1971 • Arpanet now has 15 nodes • First email was sent to a group of computers • 1972 • Arpanet has now 37 nodes

  6. History • 1976 • Queen Elizabeth of England sends her first email • Early 1980s • The military set up their own network and named it MILNET

  7. History • Mid 1980s • Network of linked computers are growing… around 50,000 nodes • It linked universities and research laboratories • 1982 • It was then called the INTERNET

  8. Benefits • File sharing • Hardware sharing • Program sharing • User communication • Multiplayer gaming

  9. Considerations • Money • Future Growth • Cable Type • Cable Length

  10. Networking Models • Client/Server • Two computers – Clients & Servers • Clients are usually computer workstations sitting on the desks of employees in an organization • Servers are usually more powerful computers and are held in a central location/s within an organization

  11. Network Servers • Servers are computers that perform services for other computers on the network • LANs and WANs usually have File Servers and Login Servers • The Internet has other types of servers such as Web Servers and Mail Servers.

  12. Networking Models • Peer-to-Peer (P2P) • Only workstations are connected to each other • Much simpler to set up than Client/Server Networks • Lack some of the advantages normally associated with networks (Central Management) • Set up among with few computers within an office or single room

  13. Networking Models • Local Area Network (LAN) • A network contained within one building or site • Wide Area Network (WAN) • A network that spans several sites across a city, country or even the world • A Client/Server may be a LAN or WAN, but a P2P network can only be a LAN.

  14. Data Packets • When a workstation wishes to send data, it encloses the data in a 'packet' containing a 'header' and a 'trailer' • The header and trailer contain information for the destination computer.

  15. Data Packets • When a data packet is put onto the network by a workstation, each computer on the network examines the packet to see who it is intended for. • The packet quickly dissipates if it is not recognized, allowing other packets to be sent. • The rate at which packets can be sent is called the Bandwidth

  16. Data Packets • Data packets are transmitted between computers on the network either as • Electrical signals in electric wires • Light signals in fiber optic cables • Electromagnetic waves through space

  17. Electrical Cables • Electrical cables are the usual means of connecting the computers in a LAN and in a WAN on one site. • Cables can either be coaxial cables or twisted pair cables.

  18. Coaxial Cables • Coaxial cables have a copper wire running through the middle encased in plastic insulation. • The plastic insulation is itself encased in a metal braid (copper mesh) which is covered by an outer layer of plastic insulator.

  19. Coaxial Cables

  20. Coaxial Cables • The electrical signals run through the central wire and the metal braid acts as both an earth and as a shield against electromagnetic interference. • Coaxial cables are connected to devices by means of a special plug with a bayonet connection. This is called a BNC plug.

  21. Coaxial Cables

  22. Twisted Pair Cables • Twisted pair cables come in two types • Unshielded Twisted Pair (UTP) • Shielded Twisted Pair (STP).

  23. Twisted Pair Cables • UTP cables have pairs of insulated copper wires twisted round each other to cancel out electromagnetic interference. • STP cable wires have a metal cover encasing the twisted pairs, shielding them further from outside electromagnetic interference.

  24. Twisted Pair Cables

  25. Twisted Pair Cable

  26. RJ-45 Connector

  27. Fiber Optic Cables • Fiber optic cable is often used to connect several buildings within a site. • Fiber optic cables are more expensive than electrical cables • But have higher bandwidths and can transmit over longer distances.

  28. Fiber Optic Cables • Fiber optic cables have a thin strand of glass in the center that carries the light pulses initially put into it by means of Light Emitting Diodes (LEDs)

  29. Fiber Optic Cables • The central strand is encased in glass shield of lower density than the central strand – ensures that the light signal is kept within the central strand by total internal reflection.

  30. Fiber Optic Cables • The glass cladding may then be surrounded by strengthening wires and a plastic outer cover.

  31. Fiber Optic Cables

  32. Network Interface Card • All computers within a network need to be physically connected to the network. • This is achieved by a Network Interface Card or Ethernet Cards which transmits and receives the data packets. • A Network Interface Card has one or more sockets for network cables and the type of socket depends on the type of network it will be used in.

  33. Network Interface Card

  34. Network Hub • A device for connecting multiple twisted pair or fiber optic Ethernet devices together, making them act as a single segment

  35. Network Switch • Is a computer networking device that connects network segments. It often referred to as an intelligent hub or switching hub.

  36. Switch Hub Router

  37. Router • A computer networking device that forwards data packet across an internetwork toward their destinations, through a process known as routing. • Filter out traffic according to their protocols.

  38. Backbone • A backbone is a larger transmission line that carries data gathered from smaller lines that interconnect with it.

  39. Backbone • At local level, a backbone is a line or set of lines that LANs connect to for a WAN connection. • On the Internet, a backbone is a set of paths that local or regional networks connect to for long-distance interconnection.

  40. Gateway • A gateway is hardware or software that provides a bridge between two otherwise incompatible networks. • Once a gateway is established then data can flow seamlessly between the network segments. • Software routers are sometimes referred to as gateways.

  41. Network Cabinet

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