Networking Concepts

Last updated: Sunday, September 26, 2004 4:05 (EDT GMT-5)

TODO--> CH: DRAW NETWORK DIAGRAM

We often see course participants in the past asking questions confused of basic networking concepts especially those working in a Microsoft Windows environment only. So we are spending time here to explain how a computer works and how a network works in its basic terms.

• In the old days of computing 30-40 years ago, users provided an input to the computer and computer output the results similar to how a calulator functions
• As computers became larger, they were expected to do more tasks on their systems at the same time. And computers were big and expensive so any unused processing time on the CPU (the computer brain) was very wasteful and costly. If you don't use the computer, it became a waste of money.
• Data was put in memory and in the hard disk, but hard disks are very slow in comparison to the memory.
• Then people decided they would like to share their results with others and to put data from other users elsewhere. Remember it is very expensive to have a computer, so more work the computer does, the more cost effective the computer becomes. So, people sent data for the computer to be analyzed. Originally, you send it via postal mail or hand deliver on magnetic tapes, but this took sometime and the magnetic tape could get damaged, etc. There must be a way of interconnecting these computers together so they can communicate with each other, thus the concept of a network was developed.
• Definition:
  • Telecommunications – technology of communications at a distance that permits information to be created any where and used everywhere with little delay
  • Network - A collection of computers interconnected so any computer can send messages to another computer by providing an address.
• Phone line -- call other computers and then read what you need over the phone and retype it again!!!! But slow, what happen if it is really long?
• So is there a better method?
• Draw a network diagram of ICGEB -- so people understand how this place is configured.
• Mention how the computers are networked together here at ICGEB as an example. Using ICGEB as an example explain the following as well.
• Computers communication with each other via a medium (here they used twisted pair cables -- very expensive).
• Network protocol (we just know that networks communicate by a protocol called TCP/IP -- that is all you need to know)
• Every computer has an address like 192.168.153.5 consisting of four numbers. It is called an IP Address. In this example, this is the local network. Any IP Address starting with 192.xxx.xxx.xxx are reserved for local networks which is what is setup here at ICGEB. There is also a public static address for the internet as well. The IP Address is based on 4 numbers. For example, my computer is 130.14.21.57 where 130 is for all National Institutes of Health. Some large institutions have a huge block of IP Address.
• Domain Name service. It is hard to remember numbers so there is a domain name server that translate the IP Address (numbers) to words like trainlab.com.ui.edu.ng for 192.168.153.5
• Ethernet -- is the technology most commonly used today for networking of computers.
• A group of standards for defining a local area network that includes standards in cabling and the structure of the data sent over those cables as well as the hardware that connects those cables. So, when you hear the term ethernet, it simply refers to a standard.
• Bridge: device to interconnect two LANs that use the SAME logical link control protocol but may use different medium access control protocols. Refer to the network diagram.
• Router: device to interconnect SIMILAR networks, e.g. similar protocols and workstations and servers. Refer to the network diagram.
• Gateway: device to interconnect DISSIMILAR protocols and servers, and Macintosh and IBM LANs and equipment. Refer to the network diagram.
• Some definitions in detail often not really explained in the lecture -- but here it is if you want the details:
  • A hub is the place where data converges from one or more directions and is forwarded out in one or more directions. Seen in local area networks
  • A gateway is a network point that acts as an entrance to another network. On the internet, in terms of routing, the network consists of gateway nodes and host nodes.
    Host nodes are computer of network users and the computers that serve contents (such as Web pages).
    Gateway nodes are computers that control traffic within your company’s network or at your local internet service provider (ISP)
  • A router is a device or a software in a computer that determines the next network point to which a packet should be forwarded toward its destination.
    Allow different networks to communicate with each other
    A router creates and maintain a table of the available routes and their conditions and uses this information along with distance and cost algorithms to determine the best route for a given packet.
    A packet will travel through a number of network points with routers before arriving at its destination.
  • 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).
    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).
  • Allow different nodes of a network to communicate directly with each other.
    Allow several users to send information over a network at the same time without slowing each other down
• The Windows 2000 Professional workstation (where you be sitting at) and Red Hat Linux 9.0 Server computers in this course are interconnected together. They could talk to each other, share information, and run programs on other more powerful machines. The Windows 2000 Professional can access via ftp, scp, samba (go into Network Neighborhood) -- this goes to the Linux Network and the machine can communicate to each other as well. For example, user30 can read files in user31 if it is public, but at the same time also access files off the main server by ftp. Ultimately, you need to know the difference of where you are to answer this basic question, where is my file? Did I put it on the Linux server or on my Windows 2000 machine?
• Demo how you log into another computer.
• Online Audio/Video Recording of Networking Class: http://www.cis.ohio-state.edu/~jain/videos.htm