Thursday, September 3, 2009

An Overview of the Wireless Networking


Here you will find wireless networking tutorials, what is wifi, general security overview, wlans, wpans, wmans, wep and wireless access control overview. Whether you want to make a phone call from your mobile, received a message on your pager, checked your email from a PDA we have come across a wireless data or voice network.

If a user or a company wants to make a data portable then Wireless networking is the answer. A wireless networking system can avoid the downtime, which may be caused in the wired network. A wireless network is also save your time and efforts in installing the lot of cables.

Also, if you need to relocate a client machine in your office, you only need to move the computer with wireless network card.

Gateway


CONFIGURING THE GATEWAY

The gateway has two sides: The WAN side connects to your cable DSL modem and LAN side connects to your private network via a hub or switch. The main function of it is to route the traffic from computer to the Internet and back to the computer. A computer with the two NIC cards can act as a gateway. It routes the network traffic between two logically and physically different networks.

In its configurations, you first configure the public side of the gateway and the IP address, which is assigned to you by your ISP. The public side configurations generally includes, assigning the IP address, DNS server, subnet mask, ISP gateway IP address and host name. Additionally, if your ISP uses PPPoE, you simply have to enable PPPoE in your gateway.

On the other hand to configure the private side , you have to enable DHCP. By enabling this feature each computer in your network, will automatically pick the settings from the DHCP server that are required for a computer to be a part of the network and communicate.

SOFTWARE CONFIGURATION

The last step in the configurations, is to configure each PC in such a way that it automatically gets the all the settings from the DHCP server. Make sure that TCP/IP protocol is properly installed in each computer of your network. After configuring each PC in your network perform a reboot.

After rebooting the each PC in your network, you will see a blinking underneath network icon on the right side of the task bar. If everything is done then you can access the internet, share the printer and data in your network.

The firewall can also be configured with it to put a check on the unauthorized network traffic from the internet to your computer or network.

What is Network Routing

What is Network Routing

You will be able to find the basic network routing overview, router configuration, router working, simulations static routes and routing table. Routing is the process of defining routes for the packets to its destination through an internetwork and this is performed by the router.
Routing is consist of two separate tasks.

1. Defining paths for the packets through and internetwork.
2. Forwarding data packets based on their predefined paths.
Generally, there are two types of routing.

STATIC AND DYNAMIC ROUTING

Routing can be performed by manually defining the routes or paths for packets to reach its destination. This is called static routing.

Stating routing works well for the small networks and when using the static routing, the routing table of the each router should be updated each time there is any change in the network configuration or topology. A router, whose routing table is not regularly updated, cannot communicate with the other routers.

While on the other end in most of the networks, routing is accomplished through the use of the dynamic routing. In the dynamic routing, routing protocols, such as RIP, OSPF etc create and maintain the routing tables of each router. Practically, dynamic routing functions very well than the static routing

ROUTING TABLE

A routing table is a set or rules, viewed in a tabular format and this used to define the routes of the data packets. All the network devices, which have IP, enabled functionality such as routers and switches use the routing tables. Routing table stores the information and configurations of every router in the IP enabled network. A routing table contains the information necessary to transmit the packets toward its destination.

When a packet is received, the network devices matches the information contained in the packets and the information in the routing tables and then it defines the shortest possible route for the transmission of the packets towards its destination.

Each packet contains the information of its origin and destination and the routing table contains the following information.
• Destination: The IP address of the packet’s final destination (next hop). Next hop: The IP address to which the packet is forwarded

• Metric: It assigns the cost to each route so that most-effective paths can be picked up.
• Routes: It includes directly attached direct subnets, indirect subnets, that are not directly connected to the device but it can be accesses through one ore more hops
• Interface: The outgoing network interface the device should use when forwarding the packet to its final destination.

Routing tables can be maintained manually by the network administrator or by dynamically (automatically). The static network tables do not change unless the network administrator changes them. Routing tables can be maintained manually or dynamically. Tables for static network devices do not change unless a network administrator manually changes them. In the dynamic routing, the network devices such as routers and switches maintain the routing tables dynamically by using the routing protocols, such as RIP, OSPF etc. In the dynamic routing, the network devices listen and detect any network or devices failure and packet congestions.

Routing in the Internet

Routing is the method in which data finds its destination from one computer to the next. In the Internet there are 3 major aspects of routing.
1. Physical Address Finding
2. Determination of inter-network gateways
3. Numeric and symbolic Addresses

Physical address finding is the method of the Internet Routing and is used when datagram is transmitted from a computer. It is necessary to encapsulate the IP datagram. This encapsulation requires the local network or physical address.

If a computer wishes to transmit IP datagram it needs to encapsulate the physical address of the destination network device in the frame. This address can be achieved by using the table that will map the IP address with the physical address. Such table can be configured into a file that can be read into the memory at the boot up time. Computer normally uses the Address Resolution Protocol (ARP), which operates dynamically to maintain the translation table.

The second method is necessary because the Internet consists of a large number of local networks, which are interconnected with each other by gateways. Such gateways are known as routers, which has physical as well as logical connectivity with many networks.

The determination of the best suitable gateway and port for a particular IP address is called routing.

The third method generally involves the translation of the human friendly form (names) to the number address (IP Address). IP address can’t be remembered due to its numeric form but the simplest names (domain names) are easy to remember e.g www.yahoo.com, www.google.com, www.msn.com are easiest to remember as compared to the IP addresses 122.11.22.34, 223.45.66.76, 155.44.55.120. DNS translates the domain names into the IP address and IP address into the domain name. This domain to IP translation is a must for communicating on the Internet because communication on the Internet is performed by the IP addresses.

Communication between routers

The Internet is a network of networks. The Internet consists of large number of autonomous systems, each of which further consists of routing domains. Such autonomous systems are usually run by the larger companies or universities. Within the Autonomous system, a router communicates with the other router using the best intra domain routing protocols, which are known as interior gateway protocols. Autonomous system are connected via gateways, these exchange information using inter domain routing protocol, which are also called exterior gateway protocols.

The RIP or (Routing Information Protocol) is the commonest interior gateway protocol and the recent protocol such as open shortest path first (OSPF). The purpose of these protocols is to enable routers to exchange locally so that all the routers in the autonomous system must a have coherent and up to date information.

When a host receives the new routing information, it is likely to update not only to it but also sends this new updated information to all the connected hosts so that they can updated themselves. Hence these changes propagate across the entire network.

Introduction to ISDN Line


Introduction to ISDN Line

Find here ISDN Network, introduction to ISDN line, bri, t1 lines, d1 lines, primary rate interface, connection time and setup instructions. The regular phone line, which is used at home and offices is an analogue phone line. Your voice is picked up by telephone mouthpiece and then sent down the phone line as an analogue wave. Regular modem converts the digital signals of the computer into the analogue waves, which then travels on the regular phone lines. At the other end, modem receives that analogue signals and then convert back into the digital signals that are understandable by a computer

ISDN network is a digital communication system that is capable of producing the maximum transmission speed of 1.4Mbps. 128Kbps speed is however more common in the digital technology. It's a international standard for sending data, voice, video over regular digital telephone lines. ISDN uses UTP (unshielded twisted pair cable) for transmission.

Router Commands Overview

In this section you will learn about the router commands, configurations, privileged mode commands, routing protocols, cisco labs and network configurations.

There are hundreds of basic and advance level commands of a router. It is not easy to remember all the commands. But some commands are frequently used and can be remembered with some practice. I have provided a list of the most commonly used commands based on their features and usage.

You will find here some basic terminology of a router.

Routing: Routing is a process of moving the data (packets) through an inter network. Routing performs the two basic tasks. Define the paths for a packet and then forward the packets on the basis of defined paths. Routing can also be defined as the communication between two or more logically and physical networks and this communication (packet transfer) is brought by a router.

First of all you should remember the keyboard shortcuts of a router.

Keyboard Shortcuts
CTRL-N - show next command
CTRL-P - show previous command
SHIFT-CTRL-6 – Break

Configuring the Router

You will be able to learn the basic commands for configuring a router.
sh running-config - details the running configuration file (RAM)
sh startup-config - displays the configuration stored in NVRAM
setup - Will start the the automatic setup; the same as when you first boot the router
config t - use to execute configuration commands from the terminal
config mem - executes configuration commands stored in NVRAM; copies startup-config to running-config

config net - used to retrieve configuration info from a TFTP server
copy running-config startup-config - copies saved config in running config (RAM) to NVRAM or "write memory" for IOS under ver.11
copy startup-config running-config - copies from non-volatile (NVRAM) to current running config (RAM)
boot system flash - tells router which IOS file in flash to boot from
boot system tftp - tells router which IOS file on the tftp server to boot from
boot system rom - tell router to boot from ROM at next boot
copy flash tftp - Copies flash to tftp server
copy tftp flash - Restores flash from tftp server
copy run tftp - Copies the current running-config to tftp server
copy tftp run - Restores the running-config from tftp server

General Commands

Here is a list of the general commands. These are the basic level commands and most commonly used
no shutdown - (enables the interface)
reload - restarts the router
sh ver - Cisco IOS version, uptime of router, how the router started, where system was loaded from, the interfaces the POST found, and the configuration register
sh clock - shows date and time on router
sh history - shows the history of your commands
sh debug - shows all debugging that is currently enabled
no debug all - turns off all debugging
sh users - shows users connected to router
sh protocols - shows which protocols are configured
banner motd # Your customized message here # - Set/change banner
hostname - use to configure the hostname of the router
clear counters - clear interface counters

Privileged Mode commands of a router

Learn how to work in the privileged mode of a router.
enable - get to privileged mode
disable - get to user mode
enable password - sets privileged mode password
enable secret - sets encrypted privileged mode password
Setting Passwords on router
Here you will be able to learn how to set the password on a router.
enable secret - set encrypted password for privileged access
enable password - set password for privileged access (used when there is no enable secret and when using older software)
Setting the password for console access:
(config)#line console 0
(config-line)#login
(config-line)#password
Set password for virtual terminal (telnet) access (password must be set to access router through telnet):
(config)#line vty 0 4
(config-line)#login
(config-line)#password
Set password for auxiliary (modem) access:
(config)#line aux 0
(config-line)#login
(config-line)#password

Router Processes & Statistics

By these command you can see the statistics and different processes of the router.
sh processes - shows active processes running on router
sh process cpu - shows cpu statistics
sh mem - shows memory statistics
sh flash - describes the flash memory and displays the size of files and the amount of free flash memory
sh buffers - displays statistics for router buffer pools; shows the size of the Small, Middle, Big, Very Big, Large and Huge Buffers
sh stacks - shows reason for last reboot, monitors the stack use of processes and interrupts routines

IP Commands

Here is a list of the IP Commands
Configure IP on an interface:
int serial 0
ip address 157.89.1.3 255.255.0.0
int eth 0
ip address 2008.1.1.4 255.255.255.0

Other IP Commands:

sh ip route - view ip routing table
ip route [administrative_distance] - configure a static IP route
ip route 0.0.0.0 0.0.0.0 - sets default gateway
ip classless - use with static routing to allow packets destined for unrecognized subnets to use the best possible route
sh arp - view arp cache; shows MAC address of connected routers
ip address 2.2.2.2 255.255.255.0 secondary - configure a 2nd ip address on an interface
sh ip protocol

CDP Commands (Cisco Discovery Protocol uses layer 2 multicast over a SNAP-capable link to send data):

sh cdp neighbor - shows directly connected neighbors
sh cdp int - shows which interfaces are running CDP
sh cdp int eth 0/0 - show CDP info for specific interface
sh cdp entry - shows CDP neighbor detail
cdp timer 120 - change how often CDP info is sent (default cdp timer is 60)
cp holdtime 240 - how long to wait before removing a CDP neighbor (default CDP holdtime is 180)
sh cdp run - shows if CDP turned on
no cdp run - turns off CDP for entire router (global config)
no cdp enable - turns off CDP on specific interface

IPX Commands

Enable IPX on router:
ipx routing
Configure IPX + IPX-RIP on an int:
int ser 0
ipx network 4A

Other Commands:

sh ipx route - shows IPX routing table
sh ipx int e0 - shows ipx address on int
sh ipx servers - shows SAP table
sh ipx traffic - view traffic statistics
debug ipx routing activity - debugs IPS RIP packets
debug ipx sap - debugs SAP packets

Routing Protocols

RIP, IGPR and OSPF are the routing protocols and here is a list of the commands for the working on the routing protocols.
Configure RIP:
router rip
network 157.89.0.0
network 208.1.1.0
Other RIP Commands:
debug ip rip - view RIP debugging info
Configure IGRP:
router IGRP 200
network 157.89.0.0
network 208.1.1.0
Other IGRP Commands:
debug ip igrp events - view IGRP debugging info
debug ip igrp transactions - view IGRP debugging info
Access Lists
Here is a list of the Access list command of a router.
sh ip int ser 0 - use to view which IP access lists are applies to which int
sh ipx int ser 0 - use to view which IPX access lists are applies to which int
sh appletalk int ser 0 - use to view which AppleTalk access lists are applies to which int
View access lists:
sh access-lists
sh ip access-lists
sh ipx access-lists
sh appletalk access-lists
Apply standard IP access list to int eth 0:
access-list 1 deny 200.1.1.0 0.0.0.255
access-list 1 permit any
int eth 0
ip access-group 1 in
Apply Extended IP access list to int eth 0:
access-list 100 deny tcp host 1.1.1.1 host 2.2.2.2 eq 23
access-list 100 deny tcp 3.3.3.0 0.0.0.255 any eq 80
int eth 0
ip access-group 100 out
Apply Standard IPX access list to int eth 0:
access-list 800 deny 7a 8000
access-list 800 permit -1
int eth 0
ipx access-group 800 out
Apply Standard IPX access list to int eth 0:
access-list 900 deny sap any 3378 -1
access-list 900 permit sap any all -1
int eth 0
ipx access-group 900 out

WAN Configurations Commands

Networking over WAN is the main functionality of a router. The most common use of a router is for the WAN connectivity. Here is a list of the commands for the different methods of the WAN connectivity.

PPP Configuration

Point to point protocol is a method for the WAN connectivity and you will find here some commands of PPP.
encapsulation pppppp authentication
ppp chap hostname
ppp pap sent-username
sh int ser 0 - use to view encapsulation on the interface

Frame-Relay Configuration

One of the methods for the WAN connectivity is the Frame Relay. Find here some basic commands for the WAN connectivity through Frame Relay.
encapsulation frame-relay ietf - use IETF when setting up a frame-relay network between a Ciscorouter and a non-Cisco router
frame-relay lmi-type ansi - LMI types are Cisco, ANSI, Q933A; Cisco is the default; LMI type is auto-sensed in IOS v11.2 and up
frame-relay map ip 3.3.3.3 100 broadcast - if inverse ARP won't work, map Other IP to Your DLCI # (local)
keep alive 10 - use to set keep alive
sh int ser 0 - use to show DLCI, LMI, and encapsulation info
sh frame-relay pvc - shows the configured DLCI's; shows PVC traffic stats
sh frame-relay map - shows route mapssh frame-relay lmi - shows LMI info

Miscellaneous Commands

In the last but not least here is a list of the some miscellaneous and useful commands
sh controller t1 - shows status of T1 lines
sh controller serial 1 - use to determine if DCE or DTE device
(config-if)#clock rate 6400 - set clock on DCE (bits per second)
(config-if)#bandwidth 64 - set bandwidth (kilobits)

What is Ethernet ?

In this section you will learn about the lan terminology, basic ethernet networking overview, a general introduction to LAN, introduction to IEEE, lan topologies, wan standards. You can also find these categories in this site such as network tutorials, computer networking guide, what is networking, tech study guides, topologies, what is data recovery, wireless communication, computer interview questions and network certification. The IEEE standards have been developed by the International Standards Organization (ISO). The Institute of Electrical and Electronic Engineers (IEEE) in 1985 produced a series of standards for the Local Area Networks, which are called IEEE 802 standards.

These standards have been accepted widely throughout the IT world. One of the IEEE 802 standards, the IEEE 802.3 is known as “Ethernet”. Ethernet is the most widely used LAN technology. Ethernet was developed by Xerox corporations in 1972 and it was the first LAN.

According to the ISO standards allows manufactures to produce the devices and equipments, which are guaranteed to operate anywhere.


The Ethernet in its simplest form uses a passive bus that operates at 10 Mbps. The bus is formed from the co-axial cable, which connects all the PCs in the LAN.

A single LAN may have 1024 attached computers, although in the real practice most LANS have fewer computers than this number. One or more segments of the co-axial cable are attached to end to end to create the Ethernet Cable Segment. Each segment is terminated by 50 ohm resistors.

In today’s IT world the reliable and timely access to the information has become vital. Today coworkers thousands of miles apart from each other can share data, voice, video etc with the fractions of seconds. Similarly a larger number of the coworkers can review the research data simultaneously. The Internet allows businesses to share information and resources with their customers.

Ethernet is a communication protocol that is embedded in software and hardware devices that intended. Ethernet has become the standard computer networking protocol with the help of the Xerox, Intel and Digital

A basic LAN consists of the following components.

• Two or more computers.
• Network Interface card or LAN Card in each PC.
• Ethernet cable (Cat5, UTP/SPT) cable to connect the two computers.
• A hub, switch or router to route or direct the network traffic.
• Software for the communication/computer networking.

A network interface card (NIC) is attached and installed in each PC and is assigned a unique address. An Ethernet cable is used to connect two computers; Ethernet cable has RJ45connectors at both ends. There can be two scenarios 1. Two computers can directly connect with each other or 2. Each computer is directly connected with the hub/switch and hence communication occurs in the network. The hub or switch acts as relay.

Computer Network can be wireless. Despite of using Ethernet cable for the communication, Wireless Network Interface cards use radio waves to communicate with the wireless switch or hub. A small antenna is used in the wireless NICs, switches and hubs. Although the wireless networks are more easy to use as compared to the cabled networks, but more configurations and extra care is required to setup and run a wireless network.

The alternate technologies to Ethernet are “Token Ring”, which is used in the Ring Topologiesnetworks. Token Ring is designed by the IBM and ATM. In ATM networking, devices are connected with each other over a very large distance (thus forms the WAN), and behaves like LANs.

Ethernet is a well established and widely used network standard for small to medium sized Ethernet networks as well as for other networks. Ethernet has been used over the 3 decades and forms a very excellent networking/communication environment.
Ethernet Terms
Ethernet follows a simple set of rules. To understand these rules its important to understand the

following terminology.

• Node – The devices that are attached to the segments are nodes.
• Frame – The nodes (computers or network devices) communicates in the form of short messages that are known as frames. The frames are chunks of information with variable size.
• Segment – A single shared medium is known as a Ethernet segment.

• Medium – The Ethernet devices are attached to a common medium. The frames of the data travel along with that medium. This medium can be coaxial cable. Today most commonly used communication mediums are UTP/STP cable, fiber optic cables.

Frames are analogous in human language. We have some rules for constructed the sentences. The

Ethernet protocol specifies a set of rules for constructing the frames. The frames length varies. Each frame must contain source and destination address for the identification of the recipient and the send of the message. The nodes can be uniquely and easily identified. Each Ethernet devices must have a single unique address.

Compute networking standards has brought a revolution in the network computing and it made the communication very easy and standarized. Now every computer and networking devices has to to follow the same standard to communicate with each other.

Introduction To Certifications

Comptia

In this section you will find Network Certification overview-free resources, exam tutorials, Comptia a+ exam, cissp, cisco exams, microsoft certifications. I have given the general overview of the computer networking certifications. Having knowledge of these certifications, it will be very easy for the visitors to decide their certification of choice. Users will also know the prerequisites of this exam, course outline, level of knowledge, and their expertise after having certified.

You will also be able to learn these things while browsing this website communication tutorials, what is data communication, tech study guides, topologies, computer networking guide, what is data recovery, wireless communication, computer interview questions, network tutorials, microsoft exams, cisco exams online certifications and comptia tutorials.


Network+

Network+ exam by Comptia is designed specifically for the IT professional who have more than nine months experience in the computer network administration. The code of the Network+ exam is N10-003 and it was first introduced in 1997. Till the mid of May 2005, according to Comptia’s announcement, more than 150,000 were Network+ exam certified. Network+ is an entry level exam and it paves the way for the IT professionals in their quest for the more advance certifications like MCSE, CCNA, CCNP etc. There are not prerequisites for this certification. Comptia recommends that you must have the A+ certifications.

Network+ certification is well suited and designed for the network administrators. The topics covered in this exam are media and topologies, standards, protocols, network support and implementations. The Network+ certification shows the candidate’s knowledge of the basic networking fundamentals. Like other Comptia’s certifications, the Network+ certification will not be expired once it is achieved.

SECURTY+

Security+ certification is designed for the IT professionals who have 2 years of experience in the network or systems administration and having the main focus on the security. The code of this exam is SY0101 and it was introduced by Comptia in 2002. Security+ is an entry level test for the most advanced tests like ISC2, CISSP and the SANS. As well as it can also be used as the basis for the some Microsoft certifications. Security+ certification is well suited for the network and security administrators and professionals.

The common topics included in this exam are designing security for a network, security infrastructure, cryptography, authentication, access control, internal and external network attacks and the dealing with the company’s security.

Security+ certifications shows the candidates knowledge of these things and it prepares the candidate to such level that he/she competes with the security breaches and finds some good alternative ways that are helpful in reducing the cost of a security breach. Once this certification is achieved it will never expire just like the other certifications of Comptia.

Microsoft

MCSE

Microsoft Certified Systems Engineer (MCSE) is designed for the professionals who are some requirements of analyzing the business, designing, making infrastructure, and implementing the securities at certain levels. MCSE is based on the Microsoft Windows 2000 platform and Windows NT platform (though many of the NT exams have been obsolete now). The Windows 2003 server has been merged into the MCSE exam.

MCSE certification does not retire but the newer versions are released by the Microsoft after few years. So the candidate has to be upgraded himself/herself with these latest exams. There are no specific requirements for the MCSE certifications. Those candidates who have one year experience in managing a computer network, network or desktop operating systems, will be considered suitable for this exam. Job descriptions and roles including after achieving the MCSE are Systems engineer, Network Engineer, Network Consultant, and Systems Analyst.
There is a 7 exams pass requirement for this certification and the candidates how are holding the MCSE 2000, are required to give 2-upgrade exams. By passing these exams you can achieve Windows Server 2000 MCSE exam.

Cisco

CCNA

Cisco CCNA certification (Cisco Certified Network Associates) is an introductory level exam. The CCNA exam by Cisco systems was designed for the candidates who can install, configure and do administrator of the LAN or WAN networks. CCNA is a prerequisite for the some higher level certifications like CCNP and CCDP. The CCNA exam is valid for the three years. In 2003, Cisco has introduced the two paths of the CCNA exam (INTRO and ICND). Job role for the individuals who are CCNA certified are network administration, system administration and network consultant etc.

CCNP

CCNP (Cisco Certified Network Professional) exam is designed for the candidates who can install, configure and troubleshoot a LAN/WAN network of 100 to 500 computers. The CCNP certification has its prerequisites such as CCNP certification. The topics included in this certification are converged networks, security, VPN, quality of service and broadband technologies like VOIP, DSL, Cable net etc. There is a four, three and two exams path to the CCNP. The CCNP exam is valid for the three years. The job role for a CCNP certified are Network administration, LAN administration, WAN administrator and Network consultant.

ISC2

CISSP

CISSP (Certified Information Systems Security Professional) is introduced by ISC2. the ISC2 is a not profit organization and it manages the CISSP exams. A CISSP exam is designed for the candidates who are having minimum four years of experience in the field of Information systems. A bachelor and a Master degree separately, can be a substitute of the one required years for this exam. Also, some lower level certifications like SSCP (Systems Security Certified Practitioner) is also recommended before the CISSP exam.

The CISSP exam is aimed for the IT professionals who want to be Information security professionals, systems security professionals and network security professionals.

An Overview of Computer Network Topology

Here you will learn network topology introduction, how computers get connected, bus, star, hub, hybrid, mesh, tree topologies and network physical design. In Computer Networking “topology” refers to the layout or design of the connected devices. Network Topologies can be physical or logical. In this section I will illustrate on the different types of the topologies.

Physical Topology means the physical design of a network including the devices, location and cable installation.

Logical Topology refers to the fact that how data actually transfers in a network as opposed to its design.

Topology can be considered as a virtual shape or structure of a network. This shape actually does not correspond to the actual physical design of the devices on the computer network. The computers on the home network can be arranged in a circle shape but it does not necessarily mean that it presents a ring topology.

Bus Topology

Bus topology uses a common backbone to connect all the network devices in a network in a linear shape. A single cable functions as the shared communication medium for all the devices attached with this cable with an interface connector. The device, which wants to communicate send the broadcast message to all the devices attached with the shared cable but only the intended recipient actually accepts and process that message.

Ethernet bus topologies are easy to install and don’t require much cabling and only a main shared cable is used for network communication. 10Base-2 and 10BaseT are two popular types of the Ethernet cables used in the Bus topology. Also, Bus network works with very limited devices. Performance issues are likely to occur in the Bus topology if more than 12-15 computers are added in a Bus Network. Additionally, if the Backbone cable fails then all network becomes useless and no communication fails among all the computers. Unlike in the Star topology in which if one computer is detached from a network then there is not effect on the other computers in a network.

Ring Topology

In ring Network, every computer or devices has two adjacent neighbors for communication. In a ring network, all the communication messages travel in the same directory whether clockwise or anti clockwise. Any damage of the cable of any cable or device can result in the breakdown of the whole network. Ring topology now has become almost obsolete.
FDDI, SONET or Token Ring Technology can be used to implement Ring Technology. Ring topologies can be found in office, school or small buildings.

Star Topology

In the computer networking world the most commonly used topology in LAN is the star topology. Star topologies can be implemented in home, offices or even in a building. All the computers in the star topologies are connected to central devices like hub, switch or router. The functionality of all these devices is different. I have covered the detail of each networking devices in the separate portion of my website. Computers in a network are usually connected with the hub, switch or router with the Unshielded Twisted Pair (UTP) or Shielded Twisted Pair Cables.

As compared to the bus topology, a star network requires more devices & cables to complete anetwork. The failure of each node or cable in a star network, won’t take down the entire network

as compared to the Bus topology.

However if the central connecting devices such as hub, switch or router fails due to any reason,then ultimately all the network can come down or collapse.

Tree Topology

Tree topologies are comprised of the multiple star topologies on a bus. Tree topologies integrate multiple star topologies together onto a bus. Only the hub devices can connect directly with the tree bus and each Hub functions as a root of a tree of the network devices. This bus/star/hybrid combination supports future expandability of the computer networks, much better than a bus or star.

Mesh Topology

Mesh topology work on the concept of routes. In Mesh topology, message sent to the destination can take any possible shortest, easiest route to reach its destination. In the previous topologies star and bus, messages are usually broadcasted to every computer, especially in bus topology. Similarly in the Ring topology message can travel in only one direction i.e clockwise or anticlockwise. Internet employs the Mesh topology and the message finds its route for its destination. Router works in find the routes for the messages and in reaching them to their destinations.The topology in which every devices connects to every other device is called a full Mesh topology unlike in the partial mesh in which every device is indirectly connected to the other devices.

Summary

Topologies are the important part of the network design theory. A better network can be built if you have the knowledge of these topologies and if you know the difference between each topology. Similarly you should have the knowledge of each network device so that you can properly use them according to your network needs. A misconfigured network can result in a waste of time and energy as well as a lots of troubleshooting methods to resolve the issue. So thebasic understanding of the network topologies and network devices is a must to build a good network.

Introduction to the Network Communication Devices

In this tutorial you will learn get the basic introduction to network devices such as nic adapters, routers, hubs, switches, modems, communication cables, lan/wan routers, gateway and other devices. A network is consists of a larger number of the communication devices. The simplest device that is used in the communication is the NIC adapter which is attached with the every computer in a network. If you want to build a LAN, you will need to have computers, hubs, switches, network adapters, UTP/STP cables, routers, internal/external modems, connectors, cable testers and clipping tool.

On the other hand if you need to build WAN, you will need to have routers, switches, dedicated or leased telephone lines such as ISDN lines, frame relay connection and other types of wan communication connections.

There are different communication mediums such as Ethernet cables, copper wire, coaxial cable, fiber optic cables, leased telephone lines and ever air is also a communication medium for the satellite communication. The most common networking medium is the LAN is the Ethernet cable (UTP/STP), which is used in the star topology. Hub is a central device of a network and every computer in a network is directly connected with the hub.
If the hub fails to work, the communication between the computers stops till the hub again starts working. Hub broadcasts the data to its every port, and then finding the destined computer, the data sent toward it. The switch is an advance form of the hub similar in functions but the advanced switches has a switching table in them. A advanced switch stores the MAC address of every attached computer and the data is only sent to the destined computer, unlike the hubs where data is sent to all ports. A router is a key device in the internet communication and wan communication system. A router has software called routing table and the source and destination addresses are stored in the routing table.

A router connects two logically and physically different networks. Router finds the IP address of the next hop (next router) and the data is sent toward it and so on. The well known routers developing companies are Cisco systems, Nortel, DLink and others. Every ISP, banks, corporate offices and multinational companies use routers for LAN and WAN communications and communication in their private networks. A gateway can be device or software in a network.

A gateway device connects the LAN with the internet. A gateway is directly exposed to the internet so it should be securely configured and in and out traffic should be monitored. If you are using DSL connection, you must need a DSL modem in your network. The telephone line is connected with the DSL modem and UTP/STP cable attaches your computer with the DSL modem. Modems are the devices that are used to modulate and demodulate the data. They convert analogue signals to digital and digital signals to analogue so that signals can travel on the telephone lines.

There are certain types of the cables that are used to connect two or more computers in a network. Fiber optic cable acts as a backbone between the ISPs and corporate offices. Data travels at the speed of light on the fiber optic cables. The cost and the installation cost of the fiber optic cable is very high but it is becoming very popular in the home networking and LANs also. In the local area networking, 10baseT/CAT5 cable is most commonly in use.

A server is a computer in network that provides services to the client computers such as logon requests processing, files access and storage, internet access, printing access and many other types of services. Servers are mostly equipped with extra hardware such as plenty of external memory (RAM), more data store capacity (hard disks), high processing speed and other features.


Active Directory

A network is created to group computers and other objects into a common ground to share their means. The connected computers provide resources, such as files, folders, (local) printers, DVD players, that other computers can take advantage of. Besides the computers, peripherals such as printers, projectors, fax machines, etc, are made part of the network and shared so their use can be as transparent as possible. The computers, peripherals, users, and other resources that are part of a network are also called objects. The interaction and usefulness of the objects that are part of a network is mainly taken care of by people called users.

Because there can be so many objects in a network, they should be better organized to be able to locate and manage them. To make this possible, the objects are created as a list. The first or top item of the tree is referred to as the root. This main list contains items called nodes. Each main node of the list is considered a category of items. A category can contain its own internal categories also called nodes:

Introduction to Network Management

Management Overview

As a network administrator, you will perform various tasks to keep the network up and running. These include computers, users (the people who use the network), the peripherals (the other machines attached either to the computers or directly to the network. To make this possible, both Microsoft Windows XP Professional and Windows Server 2003 provide the various tools you will need. If you are managing a peer-to-peer network, the former provides local and possibly small network tools to manage workstations. For a client/server network, Microsoft Windows Server 2003 provides all the tools you need to locally or remotely manage the servers or the clients.


Joining the Network

Creating a Computer Account

After creating a domain, you can can add client computers to it. In our examples, we will add workstations that run Microsoft Windows XP Professional. There are two actions to adding a client to a Microsoft Windows Server 2003 domain but only one is required.

Before physically or electronically adding a client to a domain, you can first create a computer account for it. To create a computer account, you have various alternatives:

  • If using the Manage Your Server window, you can click Manage Users And Computers In Active Directory
  • You can also click Start -> Administrative Tools -> Active Directory Users And Computers
  • You can also click Start -> Control Panel -> Administrative Tools -> Active Directory Users And Computers

Any of these actions would open the Active Directory Users and Computers window. In the left frame, expand the name of the domain. Then you can right-click the name of the domain -> New -> Computer. This would open the New Object - Computer dialog box. In the Computer Name text box, enter the name of the computer. The operating systems before Windows 2000 don't use very long names. Therefore, when naming a computer, keep this in mind and give a name made of fewer than 15 characters. After naming the computer, click Next twice and click Finish.

Instead of right-clicking the name of the domain, in the Active Directory Users And Computers, you can expand the name of the domain, right-click the Computers node -> New -> Computer. As mentioned already, in the first page of the New Object - Computer wizard, you can type a name for the computer. Here is an example:

Joining a Domain

After creating an account for a computer, you can add it to the domain. This is referred to as joining a domain. Normally, primarily creating an account for a computer is not required although it's a good idea. When joining a domain, if the computer you are adding doesn't have one already, an account would be created for it.

To join a domain using Microsoft Windows XP Professional:

  1. First display the System Properties dialog box. To do this,
    • You can right-click My Computer and click Properties...
    • You can display Control Panel and double-click System
  2. In the System Properties, click Computer Name
  3. Click Change...
  4. In the Computer Name text box, enter the desired name of the computer. If you had already created an account in the domain for this computer, type that name
  5. In the Member Of section, click the Domain radio button
  6. Click the Domain text box and enter the name of the domain
  7. After specifying the name of the computer and the domain to join, click OK
  8. You would then be asked to asked to provide a user name and a password for a user who has the permissions to join let a computer join a domain
  9. After entering a user and a password, click OK. If you have the right to add computers to the domain, you would receive a Welcome message and click OK:
  10. Once you click OK, you will be asked to restart the computer, which you should do. Therefore, in the System Properties dialog box, click OK
  11. When asked whether you want to restart the computer, click Yes
  12. After the computer has restarted, when it displays the Log On To Windows dialog box, click the arrow of the Log On To combo box and select the name of the domain
  13. If necessary, change the User Name in the top text box.
    In the Password text box, enter the password associated with the user name
  14. Click OK

Server Installation

In Lesson 1, we saw that a server was another computer that can participate in a client/server network, as opposed to a peer-to-peer network. A server is used to hold resources and items that other computers would need:

A server is primarily a regular computer. For a small network, identify the computer that you will use as the server. You can use an existing computer or purchase a new one. Before starting to acquire the necessary hardware for your network, when planning a server, you may fit one or the following descriptions:

Network Setup (Peer-To-Peer)

Wired Networking

After installing the operating systems on the computers that will primarily participate in the network, you can "physically" connect the computers and the router. You can start connecting the pieces whether the computers are on or off.

  1. Shut down all computers and the router (if necessary)
  2. Turn on one computer you will use to setup the router
  3. You router should have come equipped with a piece of paper or a brochure of just a few pages that lists the instructions to follow to setup the router. One of the early instructions may ask you to insert the CD that came with the router, in the CD drive and wait for the instructions. Follow these instructions faithfully
  4. After setting up and configuring the router, turn it off and turn off the computer you used to set it up (this step is optional)
  5. Connect each of the other computers to the router using an RJ-45 cable for each connection:

Wireless Networking

1) Start the computer you will use to setup the router (you should turn the others off):
2) Most, if not all, wireless routers come with very easy to follow instructions. Most of them usually ask you to first insert the CD that accompanies the router, that is, before physically installing the router. Consult the documentation (usually just one or a few pieces of paper or a small brochure) and faithfully follow its CD's instructions. At one time, the instructions would indicate to you when to connect the computer and the wireless router. To do this, you will use a cable (usually supplied to you) to connect one end to the computer and another end to the router:
  1. After installing and setting up the wireless router, turn it off and turn the computer off
If you didn't yet, install the wireless network card(s) on the other computer(s).
For any computer that doesn't have a wireless network card but has a wired network card, connect it to a port of the wireless router using an RJ-45 cable. The computers that have a network card will not need a physical connection to the wireless router:




Software Installations

Workstation Operating Systems

When you are planning to use a computer as a workstation is a network, you should make sure that computer meets the necessary requirements. In some cases, it may only meet the hardware requirements without any software. In some cases, something could be missing. In previous lessons, we cover the issues related to making sure that the computer was ready. In some other cases, you may plan to purchase brand new computers that you would use to build your network.

Acquiring Brand New Computers

If you decide to purchase or are in the position of purchasing brand new computers, as a reminder of what we reviewed in Lesson 2, here are the hardware requirements the computer must meet:
  • A processor with 300 megahertz or higher processor clock speed recommended; 233 MHz minimum required (single or dual processor system);* Intel Pentium/Celeron family, or AMD K6/Athlon/Duron family, or compatible processor recommended
  • 128 megabytes (MB) of RAM or higher recommended (64 MB minimum supported; may limit performance and some features)
  • 1.5 gigabytes (GB) of available hard disk space
  • Super VGA (800 x 600) or higher-resolution video adapter and monitor
  • CD-ROM or DVD drive
  • Keyboard
  • Microsoft Mouse or compatible pointing device

Network Software

Operating Systems

A workstation is a computer that is a member of a network. At homes and small businesses, the most regular operating system, at the time of this writing, is probably Microsoft Windows XP Home Edition. Other regularly used operating systems from Microsoft are Microsoft Windows XP Professional, Microsoft Windows 9X, and Microsoft Windows 2000 Professional. On this site, we will mostly cover Microsoft Windows XP Professional.

When preparing to get or acquire your workstations, you may be in one of the following scenarios.

Using New Computers

If you get a contract to build a network for a small business or you are going to create a new network for a home, you may decide to purchase brand new computers. If you haven't bought the computer(s) but are planning to, refer to our section on purchasing or acquiring new computers in the Lesson 4.

Using Existing Computers

If you already have one or more computers that you plan to use as workstations, in the previous lesson, we reviewed how you can get it ready for Microsoft Windows XP Professional. Once the computer is ready with the appropriate hardware, you can prepare the operating system. Because Microsoft Windows 9X, Windows Me, and Windows XP Home Edition have only limited security, on this site, we will mostly consider only Microsoft Windows XP Professional. Based on this, if you have a computer with Microsoft Window 9X, Windows Me, or Windows XP Home Edition but plans to apply a good level of security in your network, you should upgrade it to either Microsoft Windows 2000 Professional or Windows XP Professional.

Network Hardware

As introduced in the previous lesson, in a network, computers and optional other devices are connected to share resources. When a computer or device A is requesting a resource from another computer or device B, the item A is referred to as a client. Because all or most items that are part of a network live in association or cooperation, almost any one of them can be referred to as a client. Based on this, there can be different types of clients. The most regularly used of them is referred to as a workstation.

As its name implies, a workstation is a computer on which a person performs everyday regular assignments. A workstation is primarily a personal computer (PC). It can also be a laptop. You have probably used PCs so far. Almost any modern PC can be used as a workstation and participate on a network.

Before building a computer network, when planning the workstations, you may be in one of the following scenarios.

Monitors

A monitor is a display that a user looks at when performing daily assignments. You can buy a monitor from a computer store or from a web store. When purchasing a monitor, keep in mind that users may stare at it all day long. You should put as much care as possible when acquiring one.

If you haven't bought the computer(s) and monitors, you can refer to our section on purchasing or acquiring new computers in the Lesson 4.

If you are using an existing computer, it may have a monitor attached to it already. You can still replace it if you want.

If you are using a barebone computer, make sure you purchase a monitor and attach it to it. It is usually easy to connect a monitor to a computer. It uses a unique connector usually in the back of the computer.

Printers

If you want your users to be able to print, you can use an existing printer or purchase a new one. The simplest printers will be attached to one computer and "shared" to allow other computers to access it.

Network Cables

Cable is used to connect computers. Although we are planning to use as much wireless as possible, you should always have one or more cables around. In our network, we will use Category 5 cable RJ-45. The ends of the cable appear as follows:

You can purchase this cable from a web store on the Internet. Probably the fastest way to get this cable is to go to a computer store. When purchasing it, get something with at least 6ft.

Hub

A hub is rectangular box that is used as the central object on which computers and other devices are connected. To make this possible, a hub is equipped with small holes called ports. Here is an example of a hub:

Although this appears with 4 ports, depending on its type, a hub can be equipped with 4, 5, 12, or more ports. Here is an example of a hub with 8 ports:

When configuring it, you connect an RJ-45 cable from the network card of a computer to one port of the hub.

In most cases for a home-based or a small business network, you may not need a hub.

Routers: Wired or Wireless

Like a hub, a router is another type of device that acts as the central point among computers and other devices that are part of a network. Here is an example of a wired router:

A router functions a little differently than a hub. In fact, a router can be considered a little "intelligent" than the hub.

Like a hub, the computers and other devices are connected to a router using network cables. To make this possible, a router is equipped with holes, called ports, in the back. Here is an example:

Based on advances in the previous years from IEEE and other organizations or research companies, there are wireless routers. With this type, the computers and devices connect to the router using microwaves (no physical cable).

In our (small) network, we wish to use a wireless router. Therefore, this is the kind we suggest you purchase. You can purchase a wireless router from a computer store or on the internet (http://www.tigerdirect.com, http://www.3com.com, http://www.provantage.com, etc). You can also buy a wireless router from a computer store.

Wireless Network Cards

Depending on your network budget or your customer's, instead of using wired network cards, you can use wireless ones. A wireless NIC appears as its wired counterpart. Here are two examples:

Overall, the physical installation of a wireless network card follows the same rules as that of a wired NIC. They normally come with easy to follow instructions but it may be a good idea to install the wireless network adapters after installing the wireless router. Also, it may be a good idea to purchase the network cards and the wireless router from the same manufacturer.

Most desktop computers (workstations) come without a wireless network card. If you purchase a computer from one of the big companies on the Internet, you can choose to have it shipped with a wireless NIC. Some companies may propose to install it before shipping the computer. If you buy a computer from a store and if you want to use wireless networking, you can buy a wireless network card separately. As stated already, a wireless network card is not particularly difficult to install.

Besides the wireless network cards that can be installed inside the computer, you can use external cards. These are installed using a USB port. Here is an example of a USB adapter:

These adapters, like most USB objects, are easy to connect and use. Like the other hardware parts, when you connect these, the computer detects them and helps you get them ready for use.

Unlike desktop computers, most laptops nowadays come equipped with a wireless network card (in fact most laptops today ship with both a wired and a wireless adapters). This means that, after purchasing or acquiring a laptop, you should simply check whether it has a wireless adapter. The way you check this depends on the laptop. Therefore, check its documentation. If your laptop happens not to a have a wireless adapter and you want to use one, you have two main options. The classic style of adapter appears as the following two examples:

Client/Server Networking

A computer network is referred to as client/server if (at least) one of the computers is used to "serve" other computers referred to as "clients". Besides the computers, other types of devices can be part of the network:

In a client/server environment, each computer still holds (or can still hold) its (or some) resources and files. Other computers can also access the resources stored in a computer, as in a peer-to-peer scenario. One of the particularities of a client/server network is that the files and resources are centralized. This means that a computer, the server, can hold them and other computers can access them. Since the server is always On, the client machines can access the files and resources without caring whether a certain computer is On.

Another big advantage of a client/server network is that security is created, managed, and can highly get enforced. To access the network, a person, called a user must provide some credentials, including a username and a password. If the credentials are not valid, the user can be prevented from accessing the network.

The client/server type of network also provides many other advantages such as centralized backup, Intranet capability, Internet monitoring, etc.

In these series of lessons, the network we will build is based on Microsoft Windows operating systems (I have been able to fully connect some versions of Linux, such as Novell SUSE Linux, into a Microsoft Windows-based network but at the time of this writing, I will not be able to address that).

In our lessons, we will mention the names of companies or provide links. These are only indications and not advertisements. Any other company or link that provides the mentioned service is suitable.

Peer-to-Peer Networking

Based on their layout (not the physical but the imagined layout, also referred to as topology), there are two types of networks. A network is referred to as peer-to-peer if most computers are similar and run workstation operating systems:

It typically has a mix of Microsoft Windows 9X, Me, Windows XP Home Edition, or Windows XP Professional (you can also connect a Novell SUSE Linux as part of a Microsoft Windows-based network; the current release of the operating system is really easily to install and made part of the network).

In a peer-to-peer network, each computer holds its files and resources. Other computers can access these resources but a computer that has a particular resource must be turned on for other computers to access the resource it has. For example, if a printer is connected to computer A and computer B wants to printer to that printer, computer A must be turned On.

Characteristics of a Computer Network

The primary purpose of a computer network is to share resources:

  • You can play a CD music from one computer while sitting on another computer
  • You may have a computer with a CD writer or a backup system but the other computer doesn’t have it; In this case, you can burn CDs or make backups on a computer that has one of these but using data from a computer that doesn’t have a CD writer or a backup system
  • You may have a computer that doesn’t have a DVD player. In this case, you can place a movie DVD on the computer that has a DVD player, and then view the movie on a computer that lacks a DVD player
  • You can connect a printer (or a scanner, or a fax machine) to one computer and let other computers of the network print (or scan, or fax) to that printer (or scanner, or fax machine)
  • You can place a CD with pictures on one computer and let other computers access those pictures
  • You can create files and store them in one computer, then access those files from the other computer(s) connected to it

What can a Network do For You?

A computer network can be two computers connected:

A computer network can also consist of, and is usually made for, more than two computers:


Saturday, April 11, 2009

Introduction To Network

INTRODUCTION TO NETWORK

A network is a collection of computers and devices connected to each other. The network allows computers to communicate with each other and share resources and information.Or A network is a group of computers, printers, and other devices that are connected together with cables. Information travels over the cables, allowing network users to exchange documents & data with each other, print to the same printers, and generally share any hardware or software that is connected to the network. Each computer, printer, or other peripheral device that is connected to the network is called a node.
For making one Network minimum size of Computers should be 2, while maximumThere could be Millions of Computer. In one netwo6rk there could be different ComputerAnd different NOS (Network Operating System).
The Advance Research Projects Agency (ARPA) designed "Advanced Research Projects Agency Network" (ARPANET) for the United States Department of Defense. It was the first computer network in the world in late 1960's and early 1970's.

Networking Tips

Networking Tips

Computer networks are used to share the data and resources and for the communications. To get the optimized performance, data protection, maintenance, improved reliability and the security, every system administrator and network administrator should know the basic maintenance, troubleshooting and security techniques. Downtime is very dangerous for the critical network business applications and servers. In this article, you will learn some of the best networking tips and by using them you can get the optimized performance from your network.

  1. Security

A compute network is susceptible to the internet and external security related threats, which includes viruses, spyware, adware, Trojan horses, rootkits, web worms, intruders and hackers. To keep your network secure

Firewall: Install and configure a software/hardware firewall on your gateway and all other computers in your network. Firewall is used monitor the inbound and outbound traffic and block the unauthorized access and hackers’ attacks.
Antivirus: Install antivirus software such as Norton Antivirus, Trend Micro Office Scan, Panda Antivirus or McAfee and regularly scan your computer with an antivirus program.
Anti spyware: Install and configure an up-to-dated anti spyware software in your network.
Updated Operating System: Update your Windows based operating systems with the latest service packs, hot fixes and security patches.
Browser Security: Raise the level of security of your web browsers.

  1. Connectivity

Computer networking sometimes considered to be complex and seems to hard to troubleshoot. The connectivity problems occur in the computer network due to the devices conflicts, outdated LAN card’s driver, faulty hardware, faulty cable or connectors and misconfigurations. To troubleshoot the connectivity related issues, you need to perform the following tasks.

  • Check the LEDs of your LAN card.
  • Update the driver of your LAN card.
  • Scan your computer for the viruses and spyware.
  • Check the UTP/STP cable, the both end of the cable should be properly inserted i.e. one end in the LAN card and one end in the hub/switch or router.
  • Check the configurations of the LAN card.
  • PING the destination computer and check the status.
  • If your problem is still not resolved, replace the LAN card and reconfigure it.
  1. Maintenance

Computer network availability and security is very critical for the businesses. Maintenance include the domain setup, dealing with the internal and external security threats, assigning IP addresses to the computes, enabling/disabling network services like DHCP, FTP SMTP, SNMP, taking data backup, adding/removing users, troubleshooting the software/hardware, configuring the firewall and implementing the security in the overall IT infrastructure. To perform the maintenance related tasks in your compute network, you need the perfect tools.

  1. Troubleshooting

You can troubleshoot the computer network related problems by using the right tools and techniques. Be default, Windows based operating systems offer the TCP/IP stack, which contains the troubleshooting and diagnostic utilities such as PING, IPCONFIG, Hostname, ARP, Telnet, NSLOOKUP, Tracert and many others. Pinging a network computer is the first troubleshooting step as it checks the connectivity with the destination computer. Additionally, you can use the other troubleshooting tools such as Ethereal, IP Sniffer, LanGuard, Packeteer and many others. These tools help to diagnose the cause of the problem and troubleshoot them.

  1. Performance

To get the optimized performance from your computer network, you need to perform the following actions on every computer of your network.

    • Use System Tools
    • Delete Unnecessary Files
    • Update Device Drivers
    • Update BIOS
    • Uninstall Unused Programs
    • Update Operating System
  1. Wireless Networking Security Tips

The following tips are very helpful in securing your wireless computer network.

  • Change the Default SSID
    Change the Default Administrator’s password
  • Disable SSID broadcast.
  • Enable Mac Address Filtering
  • Assign Static IP address to the Network devices and computers.
  • Turn on and configure the firewall on every computer in your network.
  • Enable IPSec, SSL, Encryption, WPA and WPE according to your security requirements.

Securing Wireless Network


Securing Wireless Network

Wireless network has become very popular in the home and office networks. Wireless network security is required to protect your wireless network from the unauthorized access, viruses, hackers and other internal and external threats. An unsecured wireless network is an open invitation to the hackers, intruders and the viruses. Many worldwide businesses and the home users are rapidly adopting the wireless networking for the key advantages that it has like the mobility, ease of work, easy management, scalability and the lost cost.

If you plan to implement the WLAN or wi-fi then its important for you to understand the security challenges that are associated with it to protect it from the security threats. The most common security threats include the following.

  • Viruses
  • Hackers
  • Spyware
  • Intruders
  • Unauthorized Users
  • Denial of Service
  • Network Injection
  • Trojans

Solutions

The possible steps that can be taken to protect the network are the following.

  • All wireless network devices including routers, access point the PCMCIA LAN cards need to be secured.
  • The wireless network needs to be monitored for detecting and preventing it from the security threats and for monitoring the users’ activities.
  • All the users should be educated about the security threats.

Security Solutions

A wireless computer network can be protected from the internal and external security threats by implementing the following techniques.

  • Change the default password of the router.
  • Disable SSID broadcast.
  • Map the IP addresses with the MAC addresses
  • Enable WEP, WPA and WPA2 security mechanisms.
  • Enable 128-bit WEP encryption.
  • Use strong passwords.
  • Disable Remote Administration.
  • Do not auto connect to the open Wi-Fi networks.
  • Assign static IP address to the devices.
  • Enable firewall and the antivirus software on each computer.
  • Place the router and access point in the center of the network.
  • Turn off the network when you are not using it.
  • Limit access rights.
  • Upgrade to wi-fi protected networks.

Network Troubleshooting

Network Troubleshooting is a form of problem solving most often applied to repair of failed products or processes. It is a logical, systematic search for the source of a problem so that it can be solved, and so the product or process can be made operational again. Troubleshooting is needed to develop and maintain complex systems where the symptoms of a problem can have many possible causes. Troubleshooting is used in many fields such as engineering, system administration, electronics, automotive repair, and diagnostic medicine. Troubleshooting requires identification of the malfunction(s) or symptoms within a system. Then, experience is commonly used to generate possible causes of the symptoms. Determining which cause is most likely is often a process of elimination - eliminating potential causes of a problem. Finally, troubleshooting requires confirmation that the solution restores the product or process to its working state.

Network Security

How To Secure A Computer

The confidentiality, availability and the integrity of the data is the most important aspect of the computer security. Computer security refers to securing your computer from the unauthorized access and from internal and external threats like virus, spyware, Trojan horses, phishing attacks, hackers and intruders. There are a large number of techniques that can be used to protect your computer from all these threats. In this article you will learn that how to secure your computer from the most common security threats.

Network security consists of the provisions made in an underlying computer network infrastructure, policies adopted by the network administrator to protect the network and the network-accessible resources from unauthorized access, and consistent and continuous monitoring and measurement of its effectiveness (or lack) combined together.

Network security concepts

Network security starts from authenticating any user, commonly (one factor authentication) with a username and a password (something you know). With two factor authentication something you have is also used (e.g. a security token or 'dongle', an ATM card, or your mobile phone), or with three factor authentication something you are is also used (e.g. a fingerprint or retinal scan). Once authenticated, a stateful firewall enforces access policies such as what services are allowed to be accessed by the network users.[1] Though effective to prevent unauthorized access, this component fails to check potentially harmful content such as computer worms being transmitted over the network. An intrusion prevention system (IPS)[2] helps detect and inhibit the action of such malware. An anomaly-based intrusion detection system also monitors network traffic for suspicious content, unexpected traffic and other anomalies to protect the network e.g. from denial of service attacks or an employee accessing files at strange times. Communication between two hosts using the network could be encrypted to maintain privacy. Individual events occurring on the network could be tracked for audit purposes and for a later high level analysis.

Honeypots, essentially decoy network-accessible resources, could be deployed in a network as surveillance and early-warning tools. Techniques used by the attackers that attempt to compromise these decoy resources are studied during and after an attack to keep an eye on new exploitation techniques. Such analysis could be used to further tighten security of the actual network being protected by the honeypot.[3]

A useful summary of standard concepts and methods in network security is given by [4] in the form of an extensible ontology of network security attacks.

Repeaters


Introduction to Repeaters

A repeater is a communication device that retransmits the weak signals with greater power. It receives the signals over the wireless, optical transmission and network cable mediums such as copper wire, UTP/STP and fiber optic cables and regenerates the analog or digital signals. It can relay the data signals between the different subnetworks.

Repeater operates at the physical layer of the OSI layers model and it is not such as intelligent device like the switches and routers that perform the smart routing based on the MAC and IP addresses of the source and destination computers. Repeaters are also used in the broadcasting, where they are known as the relay transmitters and boosters. Repeaters restrengthen the data signals in the telecommunications. Normally a repeater consists of the following things.

  • Amplifier
  • Transmitter
  • Isolator
  • Antennas
  • Radio Receiver

In a fiber optic network, a repeater consists of the following.

  • Amplifier
  • Photocell
  • IRED
  • IR
  • LED

Fiber optic repeaters are less expensive and operate at low power.
Repeaters were also used to connect the segments of the cables. Repeaters are of mainly two types i.e. with internal antenna and with external antenna. If you are using repeater in your network make sure that is it compatible with other devices in your network.