April 13th, 2002, 05:48 AM
Basic Networking Tutorial Pt.3
This is part #3 to my series in my tutorials on basic networking. The previous tuts can be found here:
Part 2: http://www.antionline.com/showthread...hreadid=222545
Part 1: http://www.antionline.com/showthread...hreadid=220125
Hardware Devices and Interfaces
This will deal with devices on a network and what the individual hardware device does. The next tut will deal with putting it all togather and making it work. So this one will be very short compared with the first two tuts. The devices listed are what you need to get a good basic network up and going. For the home you can use a direct cable connection with ICS (internet connection sharing) or a proxy to share your dial up or high speed access. However I won't deal with this. I'm headed down the road of building a full fleged network. Yes you can have a network in your home even with dial up for minimal cost. You can start your own network for less than $100.00 (US) in many cases.
A network interface card (NIC) is a computer circuit board or card that is installed in a computer so that it can be connected to a network. Personal computers and workstations on a local area network (LAN) typically contain a network interface card specifically designed for the LAN transmission technology, such as Ethernet or token ring. Network interface cards provide a dedicated, full-time connection to a network. Most home and portable computers connect to the Internet through as-needed dial-up connection. The modem provides the connection interface to the Internet service provider. As the current trend of the high speed connection band wagon comes home. More home computers are now being provided with nic cards on board. Due to DSL, cable and satellite connections being widely availible. More and more people will be getting into networking to share one connection in the home.
In general, a hub is the central part of a wheel where the spokes come together. A hub is a place of convergence where data arrives from one or more directions and is forwarded out in one or more other directions. A hub usually includes a switch of some kind. The distinction seems to be that the hub is the place where data comes together and the switch is what determines how and where data is forwarded from the place where data comes together. Regarded in its switching aspects, a hub can also include a router.
In describing network topologies, a hub topology consists of a backbone to which a number of outgoing lines can be attached ("dropped"), each providing one or more connection port for device to attach to. For Internet users not connected to a local area network, this is the general topology used by your access provider.
A switch is a network device that selects a path or circuit for sending a unit of data to its next destination. A switch may also include the function of the router, a device or program that can determine the route and specifically what adjacent network point the data should be sent to. In general, a switch is a simpler and faster mechanism than a router, which requires knowledge about the network and how to determine the route.
On larger networks, the trip from one switch point to another in the network is called a hop. The time a switch takes to figure out where to forward a data unit is called its latency. The price paid for having the flexibility that switches provide in a network is this latency. Switches are found at the backbone and gateway levels of a network where one network connects with another and at the subnetwork level where data is being forwarded close to its destination or origin. The former are often known as core switches and the latter as desktop switches.
In the simplest networks, a switch is not required for messages that are sent and received within the network. For example, a local area network may be organized in a token ring or bus arrangement in which each possible destination inspects each message and reads any message with its address.
On the Internet, a router is a device or, in some cases, software in a computer, that determines the next network point to which a packet should be forwarded toward its destination. The router is connected to at least two networks and decides which way to send each information packet based on its current understanding of the state of the networks it is connected to. A router is located at any gateway (where one network meets another), including each Internet point-of-presence. A router is often included as part of a network switch. Or to connect an office or home network to an external network or provider. It provides the transport layer between the two.
A router may create or maintain a table of the available routes and their conditions and use this information along with distance and cost algorithms to determine the best route for a given packet. Typically, a packet may travel through a number of network points with routers before arriving at its destination.
A cable modem is a device that enables you to hook up your PC to a local cable TV line and receive data at about 1.5 Mbps. This data rate far exceeds that of the prevalent 56 Kbps telephone modems and is about the data rate available to subscribers of Digital Subscriber Line (DSL) telephone service. A cable modem can be added to or integrated with a set-top box that provides your TV set with channels for Internet access. In most cases, cable modems are furnished as part of the cable access service and are not purchased directly and installed by the subscriber.
A cable modem has two connections: one to the cable wall outlet and the other to a PC or to a set-top box for a TV set. Although a cable modem does modulation between analog and digital signals, it is a much more complex device than a telephone modem. It can be an external device or it can be integrated within a computer or set-top box. Typically, the cable modem attaches to a standard 10/100 Ethernet card in the computer (They also adapt to 10 BaseT).
All of the cable modems attached to a cable TV company coaxial cable line communicate with a Cable Modem Termination System (CMTS) at the local cable TV company office. All cable modems can receive from and send signals only to the CMTS, but not to other cable modems on the line.
The actual bandwidth for Internet service over a cable TV line is up to 27 Mbps on the download path to the subscriber with about 2.5 Mbps of bandwidth for interactive responses in the other direction. However, since the local provider may not be connected to the Internet on a line faster than a T-carrier system at 1.5 Mpbs, a more likely data rate will be close to 1.5 Mpbs.
In addition to the faster data rate, an advantage of cable over telephone Internet access is that it is a continuous connection. Which will be delt with later when the security of the network will be disscussed.
Yes you can use a dial up modem in full fleged networking involving hubs, routers and NIC cards. I'll get into that in the next tut "putting it all togather and making it work". A modem modulates outgoing digital signals from a computer or other digital device to analog signals for a conventional copper twisted pair telephone line and demodulates the incoming analog signal and converts it to a digital signal for the digital device.
The most common standard for modems today is a 56 k connecttion (the actual speed rarely achives this and/or is limited in some countries). Also there is the ISDN modem which can provide a 128k in dual mode or 64k connection. This can be dial up or an always on connection depending on what you want to pay. The advantages to the modem is that you can get internet access in areas that high speed such as cable and DSL aren't availible.
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