Computer Network Tutorial, communications

[DNR]

-Computer Network Tutorial, Communications-
by: DNR = writer @ suck-o.com:Last Update 7/14/09
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Network communications can be simplified and explained, once you understand which device or method used to connect to a network - wired or wire-less, then you can begin hacking it. This will be a basic reference, you should search for a specific manufacturer as there might be propriety protocols or special technology for that specific device.



Wired Networks - a cable connection is involved.

Dial-up- a modem dials to connect to the ISP. The modem can be connected to a telephone line or a cellphone. Only until recently, the modem used to be only a digital-to-analog device to transmit and recieve over a analog phoneline. Phonelines now can be both, analog and digial switched devices. More homes are switching to cellphones and VoIP. Modems are translators, analog to digital, and digital back to analog signals. Now, a modem can be digital to digital, as in the case of a Motorola V3 cellphone that can be used as a dial-up modem for a USB port.

ISDN/ DSL - This is more of a private network set up using the common telephone wire, it uses the standard copper telco lines but all the switches, repeaters, and even the client components like the NIC, VoIP phones, are owned and operated by the ISDN provider. The Integrated Services implies that it has technology to simultaneously deliver both audio and video, or several connected devices can use the single line at the same time. The technology is the ability to use a single cable by splitting its signals into 'channels', and sort of like your televison channels, each has its own different show. With the availability of coax-cabled networks (like comcast), wifi, and even cheap dial-up, ISDN is not the only choice and maybe too expensive and problematic to implement.

Cable- You are connected to the service provided by a network, simply by a cable. The cable can be twisted-pair of wires, or a coax cable. Like the ISDN/DSL, it is a network set-up, but instead of using the common teleco lines, the Provider uses their own cable, typically coax cable. Inside a building, it can be twisted pair, that is individual wires twisted together to make a cable. The cabled network uses a Network Interface Card (NIC), a hub or router, servers that are computer that provide some kind of service. Cable layout can vary - computers and devices can be connected in a line, a ring, or mesh. The worldwideweb is an example of a mesh network, as there are many paths a packet can take to get to sender/receiver. The layout is called network topology, and it can change from one part of the network to the other, the indvidual sections can be called segments, and isolated from each other by switches.

Fiber optic- Expensive technology and expensive cable, primarily used as a backbone route. It is used by telecom, ISP,gov, edu, and mil. It is covered here because it is a different technology than a modem, a cable, or wifi. It is light-transmission, rather than digital bits on and off, it is lighwaves on/off signals. Fiber-optic was also considered high security as there is no leakage of signals, as in the case of radio-waves, or intercepted packets as on the public internet.

Power-line-Imagine this, your powerline is the wires going from your fusebox to your appliances, your tv, your outlets. You can plug in a device that will modulate frequencies through those same copper wires to communicate with each other. Several problems arise due to inherent defects of power supply. Filters-that clean the power supply can clean the line of your intended signals. Power spikes - from people turning stuff on and off on your grid will create noise and interfere with your intended signals. AC devices are just noisy by themselves.

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Wireless Networks - instead of a cable connection, a signal is used for communication, it can be radiowave, or lightwave.

The radio-wave version of wireless network is broken down in to many different techologies, 802.11, 802.16, CDMA, EV-DO, UMTS/GSM, MIMO, HSDPA, iBurst, OFDM. The principle is the same, they use radio frequencies. The different technologies are just ways data is broken down into packets and signalling techniques. Transmitting radio waves over long distance requires lot of power, this means smaller devices won't have the battery power and means to transmit over long distances. The ability to recieve a signal from a powerful base station does not mean the smaller mobile device can send a signal to the base station as well.

WiFi- Wifi should be understood as any device that uses the 802.11 industry standards set by IEEE, the consortium that defines and approves the devices. Wifi is used to connect computers and other devices into a network, other devices can be VoIP phones, printers, MP3 players, game consoles, and cameras. Wifi is radio-waves, just think of a CB or police radio, but a small electronic board translates it into computer language so you can see video and text, as well as voice in digital quality.

WiMax- The original WiMAX standard (IEEE 802.16) specified WiMAX for the 10 to 66 GHz range. This is the difference from Wifi, which was made for short-wave 2.4GHz. 802.16 later added specifications for the 2 to 11 GHz range.WiMAX uses more expensive longer range Microwave equipment, and is typically used for point-to-point transmissions. WiBro is a korean company that created the IEEE 802.16e (mobile WiMAX) international standard. This was meant to provide mobile broadband service to cellphones and networks.

Bluetooth- The technology was standardized by a Bluetooth special interest group at first, then later accepted as IEEE standard 802.15. This is a low-powered solution to a small network, it provided a way for mobile phones, MP3 players, laptops, printers and cameras to communicate. Low-power meant shorter range radio frequency, but it also meant less battery drain than a wifi application of the same device. There are three classes of bluetooth devices, Class 1 means it can be upto 100mW of power, and reach out to 100 meters, Class 2 is 2.5mW, and can go upto 10 meters. Class 3 is 1mW and good for upto 1 meter. Because of the lower power consumption, the cellphone with the mobile ear-piece can have longer run time.

Satellite- Satellite Internet services are used in locations where ground based Internet access is not available from towers. This technology is also used for stations that move like including vessels at sea and mobile land vehicles. Satellite service is broken down in to three levels, one-way multicast - sort of like your satellite dish for television. One-way multicast means you can see the results of the signal like a tv show, but you can't interact with it. There is One-way multicast with ground-based return, this means you get a signal from the satellite, but to reply or interact, you use a ground based option, like a telephone modem, a cable, or wifi AP. This allows for high speed transmission from the satellite, but a slower ground based transmission for your replies. Dish Network for my television works this way, I get satellite dish-to-satellite in space but the company and I can talk through my transceiver via a telephone line hook-up. I can order movies to watch on my satellite TV, but the movie is ordered through a modem on my tv-set box.
Two-way satellite service means you have two satellite dishes pointed at each other and communication in the standard two-way fashion of a regular network. Think of the floating satellite in space as a router. This is like a company headquarter using a large dish to bounce off a satellite in space to talk to someone using a satellite phone, or a remote company office, also with a dish pointed at the same satellite.

CellularSince the cellular network is just another digital switched network, modems can work on a cellular network. Cellphones can plug into a laptop's USB port and use software to emulate a modem. This works at dial-up speed, but it can work where ever there is a cellphone tower nearby that can link you to your cellphone provider's service. The GM OnStar device works in this manner, it is just a cellphone wired into your vehicle.

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This tutorial will be updated, suggestions for additions or corrections can be posted in this thread. Various references were used to verify my own personal knowledge.

[bad_brain]

real nice!

[DNR]

Thanks B_B.
I think I will try to expand from here, into other areas of networking. I also will keep the "Last Updated" clock accurate - I know its annoying to read a post, and then it gets updated. At least here you can check the timestamp to see.

DNR

[CockWaffle]

ahh yes another great chunk of information that countless kids will bypass and then ask silly questions about how to get an end result without first knowing how the technology works...DNR you ever think about teaching?