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• The single most important purpose of any network – computer or otherwise – is to link similar items together using a set of rules that ensures reliable services.
• Basic set of rules for how computer network should do its job.

1. Information must be delivered reliably without any corruption of data.
2. Information must be delivered consistently – the network should be capable of determining where its information is going.
3. Multiple computers must be able to identify each other across the network.
4. The must be a standard way of naming and identifying the parts of the network.

• All networks have the same basic goal: To ensure that data is shared quickly, reliably, and accurately.
• Networking offers a lot of benefits in the area where sharing data, applications, and printer are heavily needed. It helps avoid from running from one machine to another machine especially if the machines are placed at great distance apart.

Network Concepts:

Network has two components: physical topologies (physical network) and logical arrangement (logical network) of the physical pieces.

• Physical network – wiring, network card, computer, and other equipment the network need to transmit data (all hardware).

• Physical Topologies – the arrangement of a network by which two more computers are connected together using network interface card and wires (usually coaxial cable 10BASE2, Twisted Pair 10BASE-T, or fiber optic cable).

• Three kinds of topologies

  1. Bus Topology (used for Ethernet (10BASE2) network and the simplest).

Note:

Pro: Cheap and simplest network to set up.

Con: Has a lot of point of failure. If one of the links between the network is broken, the entire network is down.

2. Star Topology

• Commonly used Ethernet (10BASE-T). More complex networks are built using star topology.
• Have junction box called a hub or concentrator at the center of the network, which manages intercomputer communication.

Note:

Pro: Far more reliable than bus topology. A single computer can be disconnected from the star topology network on the fly without having to fear of crashing the network.

Con: Required a hub, thus increase the cost of setting up the network.

FDDI (Fiber Data Distributed Interface) networks run over optical fiber cables instead of copper wire and use a complex star topology (mixture of star and ring).

• Similar to Token Ring with an exception that a single computer can connected to two concentrator/MAUs so that if one network connector fails, the other can automatically pick up the slack.
• System connected to more than one concentrator are called dual homed.

Note:

Pro: Very fast, normally used for high speed applications and applications demand the network with capability to push a lot of data over a wire.

Con: Very expensive to install and operate.

3. Ring Topology

• Used by Token Ring and FDDI.
• Similar to star topology with the exception that the concentrator or hub is replace by MAU (Multistation Access Unit) at the center of the ring network.
• MAU does the same thing as the hub, but it work with the token ring network instead of Ethernet network and handle communication between computer slightly differently.

Note:

Pro: Very fast, normally used for high speed applications and applications demand the network with capability to push a lot of data over a wire.

Con: Very expensive to install and operate.

• Ethernet, Token Ring, and FDDI topologies stem from how they allow computers to communicate with each other.
• None of these topologies can directly communicate with each other (they don’t coexist on the same network wire).
• Ethernet, Token Ring, and FDDI are referred to a logical topologies.

• Logical Network

• Rules that allows physical pieces to work together or the organization of the hardware (hard drive, printer, or application that your computer would not be able to access without the network) that results from networking software.
• Network protocols is an example of logical network.
• A way for computers to communicate with each other (similar to language - two people both speaking English can communicate with each other, whereas one person speak French and the other speak English could never understand each other.)
• Allows computer to communicate with each other at logical level.
• Logical network also included:
• NetWare and Domain

What are network devices?

• Two type of devices:
• Equipment that does not require networking but essential to set up network
  • Workstation – computer that user does his or her work
  • Server – computer whose resources are shared with other computer
  • Network printer – printer connected to the network so that more than one user can use print to it.
• Equipment that are absolutely central to the process of networking
  • HUB or MAU – device that provides the network with a single point of contact for all other devices.
  • Routers and bridges – device that moves data between networks.
  • Wiring and cables – connect devices together either using copper material or fiber optic.

Varieties of Networks:

• LAN (Local Area Network) – least complex organizational distinction of computer network.
  • Occupy one physical location.
  • Can be peer networks (no central computer required).
  • Can be client/server networks (central computer or server is required).
  • Have high speed data transfer.
  • All data is part of local network

  

• MAN (Metropolitan Area Network) – when LAN grown to thousand of users, the network need to move beyond its single physical location.
  • Splitting the network into smaller networks and joins them.
  • Using high speed telephone lines or special hardware device (communication link) that allows full LAN speed data transfer.
  • Enable users in several local geographical locations to use shared network resources as if they are part of the same local network (sometime require the use of router).

• WAN (Wide Area Network) – geographically scattered LANs or MANs joined together using high speed modem lines.
  • Access to resources across WAN is limited to speed of the phone line (normally from 56Kps to 1.5Mps T1 line). The restriction of the speed is known as bandwidth issue. (Bandwidth – term used to describe the maximum speed a given device can transfer data. It is measure in Kilo bits per second.)
  • Usually built when most user required the access to pool of information such as ATM banking and other database access.
  • Always require the used of router. (Router – device that manages data flows between network and responsible for figuring out what data should stay inside the local network and what data should be pass onto other network.)
  • WAN is essentially a series of LANs connected to a router.

  

• CAN (Campus Area Network) – similar to MAN but has the full network speed bandwidth running between all LANs on the network.
• Sometime requires to used bridge or repeaters to join the various piece of network. Because of this type of joining, the user never knows which server he or she is using. (Bridge – device that link network together so that they form a single logical network. Repeater – device that enables networks to communicate reasonably well by amplifies and clean up digital signal and forward them toward their destination.)
• TAN (Tiny Area Network, coined by Information Week columnist Cheryl Currid) – usually two or three computer network that people set up at home or other "non-business" location for the convenience of sharing individual computer resources.

What is Internet?

• Internet is a network of networks. Series of private computer network (LANs, MANs, and WANs) connected to each other. These individual networks are connected to a router. (In general, if your network is connected to a router, your network could conceivably be part of the Internet.)
• It is bases on standard established by committee and common consent. These standards are public domain (their specification are covered in detail in a series of document called RFCs or Request for Comment available on many Internet sites). Because it’s public domain, no royalties on patents or copyright is required when writing the Internet software applications.

Understanding relationship of Bandwidth and Internet:

• The only part of the Internet that can be identified as strictly dedicated to the Internet are the extremely fast (called high-bandwidth) phone line that make up what is called the backbone of the Internet.
• Backbone – a series of high speed phone lines that phone companies use to transmit high volumes of traffic (from megabit to gigabit per second of data transferring speed).

Understanding Different Kinds of Internet Connections:

• Dial-up connection – slowest way to connect to internet (14.4kbps – 36.6 kbps)
• 56Kbps connection – digital connection but still a slow way to connect to Internet.
• Trunk connection (or T1s, E1s, T3s, and also known as OS1s, DS1s, and DS3s) – allows communication on Internet at speed of 1.5Mbps.
• Backbone – extremely high speed networking line bases on optical fiber that can carry data up to 633 Mbps.
• Generally don’t have to worry about how your data is routed; the computer systems (the routers) that run the backbone largely automate the process.

What are Intranet and Extranets?

• Intranet – private network such as LAN, MAN, or WAN using Internet standard is called internal Internet or Intranet.
• Extranets – Intranets that used the Internet as vehicle to interact with their customers, suppliers, and business partners.