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  • Mps – Mega bits per second
  • Duplicating critical information If there’s a hardware failure or you accidentally delete something then you may be able to get it back Redundancy Example if your company has a lot of Internet orders and operates it’s own web server then having redundant servers is useful if one goes down Also it can speed up customer access time if business suddenly gets busy
  • Duplicating critical information If there’s a hardware failure or you accidentally delete something then you may be able to get it back Redundancy Example if your company has a lot of Internet orders and operates it’s own web server then having redundant servers is useful if one goes down Also it can speed up customer access time if business suddenly gets busy
  • Faster: May send email and get quicker response than trying to find person e.g., out of the office Benefits You can try calling but calling for information with multiple people may be less useful e.g., it has to be formally set up as a conference call With something like IM people can join and leave at will, also you do things like share documents via IM
  • NIC cards, every new machine has one, either it’s build into the motherboard or it plugs into an expansion slot on the computer
  • Strictly speaking you don’t need a Ethernet but a cross over cable – reverses the order of the data to trick the network card into thinking that the data has returned through a network hub. Ethernet includes twisted wire and coaxial cable. The software needed to run a network is already included in Windows.
  • Network hub Your hub acts as the center of your network -- it's the device that brings all of your connections together Routes information internally within the network: The hub is basically a giant circuit, which pushes the electronic pulses back down each line. A 2 computer network doesn’t necessarily need it if you use a cross over cable, 3 computers do need it. If the network is large and/or routes a lot of information then using a hub may not be sufficient A hub typically sends data out to all devices connected to it
  • Think of a hub as a four-way intersection where everyone has to stop. If more than one car reaches the intersection at the same time, they have to wait for their turn to proceed. Imagine that each vehicle is a bit of data waiting for an opportunity to continue on its trip. Now imagine what this would be like with a dozen or even a hundred roads intersecting at a single point. Scalability - In a hub network, limited shared bandwidth makes it difficult to accommodate significant growth without sacrificing performance. Applications today need more bandwidth than ever before. Quite often, the entire network must be redesigned periodically to accommodate growth. Latency: This is the amount of time that it takes a packet to get to its destination. Since each node in a hub-based network has to wait for an opportunity to transmit in order to avoid collisions , the latency can increase significantly as you add more nodes. Then both nodes wait a random amount of time and retransmit the packets. Any part of the network where there is a possibility that packets from two or more nodes will interfere with each other is considered to be part of the same collision domain. A network with a large number of nodes on the same segment will often have a lot of collisions and therefore a large collision domain. Network failure - In a typical network, one device on a hub can cause problems for other devices attached to the hub due to incorrect speed settings (100 Mbps on a 10-Mbps hub) Collisions - Ethernet uses a process called CSMA/CD (Carrier Sense Multiple Access with Collision Detection) to communicate across the network. Under CSMA/CD, a node will not send out a packet unless the network is clear of traffic. If two nodes send out packets at the same time, a collision occurs and the packets are lost.
  • But wouldn't it be amazing if you could take an exit ramp from any one of those roads to the road of your choosing? That is exactly what a switch does for network traffic. A switch is like a cloverleaf intersection -- each car can take an exit ramp to get to its destination without having to stop and wait for other traffic to go by. A vital difference between a hub and a switch is that all the nodes connected to a hub share the bandwidth among themselves, while a device connected to a switch port has the full bandwidth all to itself. For example, if 10 nodes are communicating using a hub on a 10-Mbps network, then each node may only get a portion of the 10 Mbps if other nodes on the hub want to communicate as well. But with a switch, each node could possibly communicate at the full 10 Mbps.
  • * In such a case they also have the capabilities of a switch
  • On the Internet, the network breaks an e-mail message into parts of a certain size in bytes . These are the packets.
  • First, the network can balance the load across various pieces of equipment on a millisecond-by-millisecond basis. Second, if there is a problem with one piece of equipment in the network while a message is being transferred, packets can be routed around the problem, ensuring the delivery of the entire message.
  • Twisting eliminates electrical interference from nearby pairs Increased twisting increases the transmission rate
  • Core (glass) – about the width of a human hair. The part that actually transmits the light. Cladding – glass surrounding the core that is designed to reflect light back into the core (to avoid loss of information) Buffer coating – a plastic jacket that protects the core from damage and moisture Fast: 100 Mbps – 2 Gbps, May run even faster (100 Gbps in lab – limited by ability to convert between light and electrical signals) Few errors: Light not electricity – means that unlike the twisted wire and coaxial cable it is not subject to electrical interference. Long range ~ 62 miles Expensive: cable is costly and installers must be well trained
  • Wireless NIC: A network card that can send and receive wireless signals Either plugs into an expansion slot of your motherboard or into a free USB slot Wireless router: Can do what a wired router receives wireless signals Wireless access point: some routers can act as one but some allow devices to access the wireless network without the features of a router The electronic computer signals must be converted by transmitter to radio waves, transmitted as radio waves and on the receiving end reconverted back from radio waves back to electronic signals
  • The standard indicates how the radio waves signals are sent e.g., one serial transmission or parallel ones. 802.11b is oldest on the list, slow just for email, IM browsing simple web pages 802.11a and 802.11g came out to replace it: can view streaming videos (but not high definition), 802.11a is outdated and most devices won’t support it 802.11n is the newest standard just getting some acceptance (expensive and most wireless devices don’t support it yet) Most commonly used are probably 802.11g and 802.11n SuperG, EnhancedG, ExtraG 108 Mbps – not a fully agreed upon standard and sometimes devices that use this standard may not work together
  • Speed – generally cheaper for a given transmission speed to use a wired network Security – typically wired networks and more secure, wireless information can be intercepted (bypass a firewall) and even the encryption algorithms aren’t as good yet. Interference: lower frequency cordless phones 2 GHz instead of 5 GHz, microwaves, walls, metal objects Convenience: wireless doesn’t require cords, you can more things around more easily.
  • Pretty much all new laptops and many desktops include wireless capabilities
  • Screen outgoing data: Checks if packets come from an actual machine on the network or going to an actual machine, if not then the packets are dropped e.g., Trojan horse sending spam Filters information You can “flag” offensive websites. If information comes in from the flagged website (e.g., as you try to click on a link to it) the information is not allowed through You will still get spammed unless you block all email Some routers include firewall software May include some protection from viruses (but best to get anti-virus software)

PowerPoint slides PowerPoint slides Presentation Transcript

  • Computer networking In this section of notes you will learn the rudiments of networking, the components of a network and how to secure a network
  • What This Section Will And Will Not Cover
    • What we will talk about:
      • The principles of how a network functions, the different parts of a network and one way of securing a network.
    • What we won’t talk about:
      • The step-by-step process of building a network.
      • Typically you can find many sites that already provide this information:
        • E.g., http://www.microsoft.com/windowsxp/using/networking/setup/default.mspx
  • What Is Required For A Network
    • 2+ computers
    • The hardware and software needed to connect them
    View slide
  • Introducing Some Basic Parts Of A Network
    • Nodes:
      • Hardware devices that are connected to the network (e.g., printers, computers)
    • Bandwidth:
      • Speed at which information transmits through the network
      • Maximum typically 10 – 100 Mbps
    Node Node Node Bandwidth speed Bandwidth speed Bandwidth speed View slide
  • Benefits Of Networking Computers
    • Resource sharing
    • Reliability
    • Cost savings
    • Communication
    • Resource Sharing
    • Non-networked computers
      • Information is stored separately and locally on each computer
    Do not accept cheques from this person! Calgary branch Edmonton branch Bad cheque
    • Resource Sharing
    • Networked computer system
      • Information is accessible from other locations as if it were available locally.
    Calgary branch Edmonton branch Do not accept cheques from this person! Do not accept cheques from this person!
    • Reliability
    • Duplicating critical information across a network
    • May provide useful redundancy
    TAMCO INDUSTRIES INC. Internet orders Server #1 Server #2
    • Reliability
    • Duplicating critical information across a network
    • May provide useful redundancy
    TAMCO INDUSTRIES INC. Internet orders Server #2: down Server #1
    • Cost Savings
    • One shared resource for multiple users instead of one item per user that is used only periodically.
    • Communication
    • Electronic communication may allow for faster responses.
    • Electronic communication may provide benefits not derived from traditional methods of communication.
  • What You Need For A Two Computer Network
    • Two computers (obvious)
    • A network adaptor for each computer
      • It’s hardware that acts as an interface between the computer and the network.
      • It can be wired or wireless.
      • Many new computers include this hardware (no need to buy a special component).
    “ NIC” (network interface card/controller) USB to network adaptor
  • What You Need For A Two Computer Network (2)
    • Ethernet connection: a network cable.
      • Or as an alternative a cross-over cable can be used (looks physically identical to a regular network cable but allows the computers to be connected without the need for additional hardware e.g., hub, switch).
    • Software to support the network connection (included in modern operating systems like Windows).
  • What You Need For A Multi (3+) Computer Network
    • The items mentioned for a 2 computer network
    • Plus a network hub
  • Hub
    • Brings all of the connections together and routes information internally
  • Hub (2)
    • Rule of thumb when a hub is needed/appropriate:
      • Needed to route information in a network consisting of 2+ computers (strictly speaking not mandatory for a 2 computer network because a cross-over cable can be used to directly connect the computers).
      • Works well for smaller networks or when there isn’t a great deal of information passing through the network.
  • Hub (3)
    • Drawbacks of using network hubs:
      • Scalability
      • Latency and collisions
      • Network failure
  • Switch
    • Similar to a hub it connects the computers in a network and routes information internally.
    • They are employed to overcome some of the drawbacks of hubs:
    • Since prices of switches have declined, hubs are rarely used now (used hubs?)
  • Router
    • Used to connect multiple networks .
  • Router (2)
    • Routers can also be used to share a broadband connection (referred to as DSL/cable routers)
    From “Technology in Action” by Evans, Martin and Poatsy
  • Transmitting Information On A Network
    • Information is broken down into parts (packets).
    • The packets are send over the network in groups
    • When the packets reach their destination they are reassembled into their original forms.
    Computer on the network with document Packets Server computer
  • Transmitting Information Over A Network (2)
    • The route taken can vary from packet-to-packet:
    Source Destination
    • Reasons for breaking information into packets:
    • Speed
    • Stability
  • Types Of Network Connections
    • Wired
      • Twisted pair: typically used for home or small networks although the fastest ones now rival fiber optic in terms of speed.
      • Fiber optic: used for larger networks when a lot of data is transmitted.
      • Power -line networks: uses existing electrical wiring to transmit network information.
    • Wireless
      • Typically use the Wi-Fi protocol for transmitting information
  • Twisted Pair Network Connections
    • The transmitting wire consists of a collection of paired wires
    Category “Cat” Max bandwidth Category 5 100 Mbps Category 5E 100 – 1000 Mbps (1 Gbps) Category 6 1000 Mbps (1 Gbps)
  • Twisted Pair Network Connections (2)
    • The ends look similar to but are larger than telephone cables.
    Telephone Computer network
  • Twisted Pair Network Connections (3)
    • Pros:
      • Mature proven technology: stable with a great deal of choice
    • Cons:
      • Rewiring of an existing home may be expensive (although new homes – North America - often have Cat 5 wiring through out the house).
    • Typical range ~300’
  • Fiber Optic Network Connections
    • Unlike twisted pair and coaxial connections which use electricity, fiber optic connections use light.
    • Pros:
      • Fast transmissions (~100 Mbps – 30 Gbps) with few errors
      • Very long range connections are possible (~62 miles)
      • Typically used for large networks where there’s a high volume of information transmitted
    • Cons:
      • Expensive
  • Power-Line Network Connections
    • Rather than requiring new wires to network equipment, this type of network uses existing power lines.
    • Transmission rates: 200 Mbps
  • Power-Line Connections (2)
    • Pros:
      • Easy to set up.
      • No new wiring needed, flexibility in the layout of nodes.
    • Cons:
      • An entire power outlet must be used (power bars cannot be used).
      • Performance can be affected by power usage.
  • Wireless Network Connections
    • The network is connected via radio waves
    • The general requirements for setting up a wireless network are similar but not identical to a wired network:
    A computer Wireless Network adaptor Wireless router
  • Types Of Wireless Network Connections
    • All are based on the 802.11 standard (also known as Wi-Fi) for wireless transmissions
    Transmission protocol Maximum bandwidth 802.11g 52 Mbps 802.11n 540 Mbps
  • Wired Vs. Wireless Networks
    • Wired:
      • Speed (faster for many)
      • Security
      • Less likely to be affected by interference
    • Wireless:
      • Convenience
  • Mixed Networks
    • To balance the strengths of wired networks vs. the strength of wireless networks a network can mix-and-match between wired and wireless connections.
    Wired portion of the network (high security) Wireless portion of the network (security is less of an issue)
  • Firewall
    • It’s one way of protecting a network.
    • Protects the network against things coming into the network:
      • Certain type of connections to your computer can be disabled e.g., transfer of files to/from your computer.
      • Connections may be made only by certain users or only within a certain period of time e.g., file transfer only possible for today or only possible for login name ‘tam’
    • Some may screen outgoing data
  • Firewalls (2)
    • Firewalls may be implemented as software or hardware
    • Software based firewalls:
      • Easy to set up and inexpensive (e.g., Windows comes with one built in)
    • Hardware based firewalls:
      • Your computer can be attacked if it can be located on the Internet
    No firewall: your computer has been located Hardware firewall: only the firewall is visible
  • A Firewall Will NOT Make You Invulnerable!
    • Firewalls cannot protect against carelessness. If YOU choose to allow a malicious program to have access to your computer then the firewall may still be bypassed. (This is an example of “Social Engineering” and will be discussed further in the section on computer security).
    • Also if your firewall is secure and your wireless signals are not then someone else may be able to ‘sniff’ out private information from the wireless signals on your network.
    Wireless signals can be intercepted even if you have a firewall X
  • After This Section You Should Now Know
    • What is a computer network
    • What are some of the benefits of networking computers
    • What’s needed to network computers
    • The role of a hub and switch in a network and the differences between them
    • The purpose of a router in a computer network
    • How is information transmitted on a network in the form of packets
    • The characteristics of common wired and wireless networks
    • How a firewall can be used to secure a network as well as the things that they can’t protect