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NETWORKING BASICS
LAN (Local Area Network) is a computer network that spans a relatively small area. Most LANs are confined to a
single building or group of buildings. However, one LAN can be connected to other LANs over any distance via telephone
lines and radio waves. A system of LANs connected in this way is called a wide-area network (WAN).
LANs mostly connect personal computers and workstations. Each individual computer or a node in a LAN has its own
processing power to execute programs and it is able to access data and devices anywhere on the LAN as accesses
are granted to each unit. Users can collaborate and communicate with each other by using LAN.
This illustrated diagram shows how to create a simple but
secure network.
1. Two (2) Personal Computers are connected to the Network
Switch.
2. Network Switch is connected into the Network Router with a Firewall.
3. Network Router is connected to the DSL Modem.
4. DSL Modem is connected to the telephone Line.
5. Telephone Line provides Internet Connectivity.
There are many different types of LANs Ethernets being the
most common for PCs. Most Apple Macintosh networks are based on Apple's AppleTalk network system, which is built
into Macintosh computers. The following characteristics differentiate one LAN from another.
Topology: The geometric arrangement of devices on the network. For example, devices can be arranged in a
ring or in a straight line.
Protocols: The rules and encoding specifications for sending data. The protocols also determine whether
the network uses a peer-to-peer or client/server architecture. Computers are connected directly into each others
in peer-to-peer networking. Client/Server architecture has a central processing unit through every client is connected
and routed.
Media: Devices can be connected by twisted-pair wire, coaxial cables, fiber optic cables or connected via
Wireless Access Points using radio waves.
LANs are capable of transmitting data at very fast rates, much faster than data can be transmitted over a telephone
line; but the distances are limited, and there is also a limit on the number of computers that can be attached
to a single LAN.
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GFI LANguard Network Security Scanner
GFI LANguard Network Security Scanner (GFI LANguard N.S.S.) is a tool that allows network administrators to quickly
and easily perform a network security audit. GFI LANguard N.S.S. creates reports that can be used to fix security
issues on a network. It can also perform patch management.
HIGHLY RECOMMENDED by KEPCIL Designs.
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HUB, SWITCH AND ROUTER
Hubs, switches and routers are all devices which connect one or more computers to other computers, networked devices
or to other networks. Each has two or more connectors, called ports, into which the cables are plugged to make
the connection. The Difference is in intelligence how they handle the data.
Network Hub
Hub is typically the least expensive, least intelligent, and least complicated of the three. Its function
is very simple: anything that comes in from one port is sent out to the others. Every computer connected to the
hub sees everything that every other computer on the hub sees. The hub itself "don't know" of the data
being transmitted and for years, simple hubs have been quick and easy ways to connect computers in small networks.
Network Switch
Switch does essentially what a hub does, but more efficiently. Difference between a switch and a hub is
that a switch can handle multiple communications between the computers attached to it whereas a hub handle one
at a time. If there are only two computers transmitting data across a network, a hub would perform identically
to a switch. However, if more than two computers were trying to transmit across the network at the same time, the
switch would perform far better.By paying attention to the traffic that comes across it, a switch can "learn"
where particular addresses are. For example, if it sees traffic from machine A coming in on port 2, it now knows
that machine A is connected to that port, and that traffic to machine A needs to only be sent to that port and
not any of the others. The net result of using a switch over a hub is that most of the network traffic only goes
where it needs to, rather than to every port. On busy networks, this can make the network significantly faster.
Network Router
Router serves a slightly different function than a hub and switch that serve the same function. A router
is explicitly designed to connect two networks together, usually a Local Area Network, or LAN (like a single small
office) to a Wide Area Network, or WAN (like the Internet). A router also has additional "smart" software
with security features that disallow unauthorized access to the computers in the LAN from the outside.
Router is the smartest and most complicated of the connecting devices. Routers come from the small four-port broadband
routers to the large industrial strength devices that drive the Internet. Router is as a computer that can be programmed
to understand, possibly manipulate and route the data it is being asked to handle. For example, broadband routers
include the ability to "hide" computers behind a type of firewall, which involves slightly modifying
the packets of network traffic as they traverse the device. All routers include some kind of user interface for
configuring how the router will treat traffic. The really large routers include the equivalent of a full-blown
programming language to describe how they should operate, as well as the ability to communicate with other routers
to describe or determine the best way to get network traffic from point A to point B.
Most broadband routers or routers for short, are a combination Ethernet switch (or hub) and Network Address Translator
(NAT). They usually include a Dynamic Host Configuration Protocol (DHCP) server, Domain Name Service (DNS) proxy
server and a hardware firewall to protect the Local Area Network (LAN) from malicious intrusion from the Internet.
All routers have a Wide Area Network (WAN) Port. This port connects to the to a DSL or cable MODEM for broadband
service (e.g., the Internet) and is usually a 10 MHz 10BASET Ethernet port. A 10 MHz WAN port is sufficient for
cable and DSL Modems as these devices transfer data at rate that is a fraction of 10 MHz.
Many recent broadband routers are combination routers/Ethernet switch (or hub) that have multiple Ethernet ports
to connect more than one PC to form a LAN. These ports allow the PCs to share the WAN port/broadband Internet connection
and perform LAN functions, such as Windows file and printer sharing. The LAN ports are usually 100 MHz 100 BASE-TX
Ethernet.
Some routers have a single WAN port and a single LAN port and are designed to connect to an existing LAN hub or
switch to a WAN.
Ethernet switches and hubs can be connected to router with multiple PC ports to expand a LAN. Depending on the
capabilities (available ports) of the router and the switches or hubs, the connection between the router and switches/hubs
may require straight-thru or crossover cables.
Network speed and connectivity
Most devices now are capable of both 10mps (10 mega-bits, or million bits, per second) and 100mbs, and will automatically
detect the speed. If the device is labeled with only one speed, then it will only be able to communicate with devices
that also support that speed. Gigabit or 1000mbs devices are starting to become more common and many devices now
also include 802.11b or 802.11g wireless transmitters that simply act like additional ports to the device.
Modem
Modem is a device that converts data from one form into another, as from one form usable in data processing to
another form usable in telephonic transmission.
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Network Topology
Network topology is the specific physical, i.e.,
real, or logical, i.e., virtual, arrangement of the elements of a network.
Note 1: Two networks have the same topology if the connection configuration is the same, although the networks
may differ in physical interconnections, distances between nodes, transmission rates, and/or signal types.
Note 2: The common types of network topology are defined in alphabetical order below:
Bus topology
A network topology in which all nodes, i.e., stations, are connected together by a single bus. All devices are
connected to a central cable, called the bus or backbone.
Dual Ring Topology
A dual ring topology has four branches connected to it, and is more resistant to failures. See more details on
Ring Topology.
Fully Connected Topology
A network topology in which there is a direct path (branch) between any two nodes. Note: In a fully connected network
with n nodes, there are n(n-1)/2 direct paths, i.e., branches. Synonym fully connected mesh network.
Hybrid Topology
A combination of any two or more network topologies. Note 1: Instances can occur where two basic network topologies,
when connected together, can still retain the basic network character, and therefore not be a hybrid network. For
example, a tree network connected to a tree network is still a tree network. Therefore, a hybrid network accrues
only when two basic networks are connected and the resulting network topology fails to meet one of the basic topology
definitions.
For example, two star networks connected together exhibit hybrid network topologies. Note 2: A hybrid topology
always accrues when two different basic network topologies are connected.
Linear topology
A network topology in which all nodes, i.e., stations, are connected together by a single bus.
Mesh topology
A network topology in which there are at least two nodes with two or more paths between them.
Ring topology
A network topology in which every node has exactly two branches connected to it. All devices are connected to one
another in the shape of a closed loop, so that each device is connected directly to two other devices, one on either
side of it. These nodes and branches form a ring. If one of the nodes on the ring fails than the ring is broken
and cannot work.
Star topology
A network topology in which peripheral nodes are connected to a central node, which rebroadcasts all transmissions
received from any peripheral node to all peripheral nodes on the network, including the originating node. Note
1: All peripheral nodes may thus communicate with all others by transmitting to, and receiving from, the central
node only. Note 2: The failure of a transmission line, i.e., channel, linking any peripheral node to the central
node will result in the isolation of that peripheral node from all others. Note 3: If the star central node is
passive, the originating node must be able to tolerate the reception of an echo of its own transmission, delayed
by the two-way transmission time, i.e., to and from the central node, plus any delay generated in the central node.
An active star network has an active central node that usually has the means to prevent echo-related problems.
Tree topology
A network topology that, from a purely topologic viewpoint, resembles an interconnection of star networks in that
individual peripheral nodes are required to transmit to and receive from one other node only, toward a central
node, and are not required to act as repeaters or regenerators. A hybrid topology. Groups of star-configured networks
are connected to a linear bus backbone.
Note 1: The function of the central node may be distributed.
Note 2: As in the conventional star network, individual nodes may thus still be isolated from the network by a
single-point failure of a transmission path to the node.
Note 3: A single-point failure of a transmission path within a distributed node will result in partitioning two
or more stations from the rest of the network.
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CAT Cable
Data is sent and received through specific wires within an Ethernet cable. Depending on the arrangement of its
sending and receiving wires, Ethernet cable is either a straight-through type or a crossover type. CAT5 and CAT6
cables can be made either straight-through or crossover.
Straight-through cable
Straight-through cables are used to connect nearly all Ethernet devices, and are the more common type of cable
in a local area network (LAN). It is most likely to use straight-through cables when using a base station or a
switch and connecting your computers into a LAN with a broadband modem.
Crossover cable
Crossover cables are most often used to connect two computers directly to each other, or occasionally to connect
a broadband modem directly to a computer. Sometimes crossover cables might be required to connect new networking
hardware to a LAN, depending on the current network configuration and the capabilities of the existing hardware.
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Straight Through
Cable
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RJ-45
PIN
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RJ-45
PIN
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1 TX+
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1 RC+
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2 TX-
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2 RC-
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3 RC+
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3 TX+
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6 RC-
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6 TX-
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Crossover
Cable
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RJ-45
PIN
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RJ-45
PIN
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1 RC+
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3 TX+
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2 RC-
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6 TX-
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3 TX+
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1 RC+
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6 TX-
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2 RC-
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Note: The standard connector view shown is color-coded
for a straight thru cable.
Category 5 wiring standards
EIA/TIA 568A/568B and AT&T 258A define the wiring standards and allow for two different wiring
color codes.
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PIN #
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SIGNAL
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EIA/TIA 568A
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AT&T 258A or EIA/TIA 568B
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Ethernet
10BASE-T
100BASE-T
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1
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Transmit+
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Green/White
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Orange/White
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X
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2
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Transmit-
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Green/White
or Green
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Orange/White
or Orange
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X
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3
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Receive+
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Orange/White
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Green/White
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X
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4
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N/A
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Blue/White
or Blue
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Blue/White
or Blue
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Not used *
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5
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N/A
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Blue/White
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Blue/White
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Not used *
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6
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Receive-
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Orange/White
or Orange
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Green/White
or Green
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X
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7
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N/A
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Brown/White
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Brown/White
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Not used *
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8
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N/A
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Brown/White
or Brown
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Brown/White
or Brown
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Not used *
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Pairs may be solid colors and not have the stripe.
Category 5 cable must use Category 5 rated connectors.
Only two pairs of wires in the eight-pin RJ-45 connector are used to carry Ethernet signals. Both 10BASE-T and
100BASE-T use the same pins, a crossover cable made for one will also work with the other.
*Note: Even though pins 4,5,7, and 8 are not used, it is mandatory that they be present in the cable.
Use the right type of cable
The type of Ethernet cable is used in the network depends on the configuration requirements of the specific devices
being connected. Always see the documentation for the network device that is going to be installed that what type
of cable to use for that particular network connection. Sometimes when there is no information, a straight-through
cable can be tried first and if the status light on the network device lights up to indicate a working connection,
and then it is the correct type of cable. If there is no status light when all the hardware is turned on, try connecting
the devices with a crossover cable instead.
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Dial-up Networking Basics for Windows
98 and Windows ME
Modem is a device that converts data from one form into another, as from one form usable in data processing to
another form usable in telephonic transmission. You may be connected to the Internet through an Internet Service
Provider (ISP) who maintains a server that is directly connected to the Internet. You must connect through an Internet
service provider unless your organization is directly connected to the Internet. Connecting to an Internet service
provider entails calling the provider and setting up a PPP account. I tested some settings for trouble-free connections
and You might want to check these out.
TCP/IP SETTINGS
Modems transfer rates are affected by line conditions, server load and the distance from the local exchange. To
optimize transfer rates, ensure that the line is clear. Also, ensure that no other protocols are used.
TCP (Transmission Control Protocol)
Internet networking software that controls the transmission of packets of data over the Internet. Among its tasks,
TCP checks for lost packets, puts the data from multiple packets into the correct order, and requests that missing
or damaged packets be resent. Computers must run TCP to communicate with Web servers.
TCP/IP Stack
To properly use the TCP/IP protocol, PCs require a TCP/IP stack. This consists of TCP/IP software, sockets software
(such as WINSOCK.DLL for Windows machines), and hardware driver software (known as packet drivers). Windows 95
comes with Microsoft's own built-in TCP/IP stack, including version 1.1 of Microsoft's WINSOCK.DLL and packet drivers.
To check your TCP/IP settings:
- double click on "My Computer" > "Dial-Up Networking",
- right click the connection icon and select "Properties",
- click on "Server Types" tab and uncheck all the options in the "Advanced Options" frame,
- uncheck "NetBEUI" and "IPX/SPX Compatible",
- click on the "TCP/IP Settings" button and uncheck "Use IP Header Compression",
- click "OK" to close the window.
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WIN98 has several other options that can be adjusted:
- double click "My Computer" > "Control Panel" > "Network",
- in the "Configuration" window should be seen only "Dial Up Adapter" and "TCP/IP"
installed, if there are any other network components and the PC is not networked, they should be removed,
- a component can be removed by clicking on the component's name and clicking on the "Remove" button.
The "Microsoft Family Logon" component can be removed safely. Windows will complain that the "Network
Is Not Complete" but that can be ignored safely. Thereafter, every time the "Network" icon is double
clicked, Windows will inform that the "Network Is Complete", just click "Yes" to continue.
To adjust TCP/IP properties:
- click on the name "TCP/IP" > "Properties" > "OK"
These are the appropriate settings, listed according to the titles on the tabs:
DNS Configuration:
- correct setting should be "Disable DNS".
WINS Configuration:
- correct setting should be "Disable WINS Resolution".
IP Address:
- this should be "Obtain an IP Address Automatically".
Advanced:
- "Allow Binding to ATM" should be set to "No".
NetBIOS:
- "I want to enable NetBIOS over TCP/IP" should be unchecked.
These are appropriate settings for the Dial-Up Adapter:
Advanced:
- "Enable Point to Point IP" should be set to "No",
- "IP Packet Size" should be set depending on the quality of the connection, try different settings to
see which works best,
- "Record a log file" should be set to "No", unless a log of every connection is required,
- "Use IP header compression" should also be set to "No".
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Any questions or inquiries may be e-mailed to keppanet@hotmail.com.
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