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NETWORK BASICS

Network A system of interconnected computers and computerized peripherals such as printers is called computer network. This interconnection among computers facilitates information sharing among them. Computers may connect to each other by either wired or wireless media. A computer network consists of a collection of computers, printers and other equipment that is connected together so that they can communicate with each other.  


Network application
A Network application is any application running on one host and provides a communication to another application running on a different host, the application may use an existing application layer protocols such as: HTTP(e.g. the Browser and web server), SMTP(e.g. the email-client). And may be the application does not use any existing protocols and depends on the socket programming to communicate to another application. So the web application is a type of the network applications. 
There are lots of advantages from build up a network, but the th…

WIRELESS NETWORKING

WIRELESS NETWORKING
Wireless is a term used to describe telecommunications in which electromagnetic waves (rather than some form of wire) carry the signal over part or all of the communication path. Some monitoring devices, such as intrusion alarms, employ acoustic waves at frequencies above the range of human hearing; these are also sometimes classified as wireless. The wireless method of communication uses low-powered radio waves to transmit data between devices. High powered transmission sources usually require government licenses to broadcast on a specific wavelength. This platform has historically carried voice and has grown into a large industry, carrying many thousands of broadcasts around the world. Radio waves are now increasingly being used by unregulated computer users. 

Humans communicate in order to share knowledge and experiences. Common forms of human communication include sign language, speaking, writing, gestures, and broadcasting. Communication can be interactive, transitive, intentional, or unintentional; it can also be verbal or nonverbal. In addition, communication can be intrapersonal or interpersonal. We  owe much to the Romans that in the field of communication it did not end with the Latin root communicate. They devised what might be described as the first real mail, or postal system, in order to centralize control of the empire from Rome. This allowed Rome to gather knowledge about events in its many widespread provinces. 


  • Fixed wireless: the operation of wireless devices or systems in homes and offices, and in particular, equipment connected to the Internet via specialized modems  
  • Mobile wireless: the use of wireless devices or systems aboard motorized, moving vehicles; examples include the automotive cell phone and PCS (personal communications services)  
  • Portable wireless: the operation of autonomous, battery-powered wireless devices or systems outside the office, home, or vehicle; examples include handheld cell phones and PCS units  
  • IR wireless: The use of devices that convey data via IR (infrared) radiation employed in certain limited-range communications and control systems 

Wireless technology is rapidly evolving, and is playing an increasing role in the lives of people throughout the world. In addition, ever-larger numbers of people are relying on the technology directly or indirectly. 


The 802.11 specification [IEEE Standard 802.11 (ISO/IEC 8802-11: 1999)] as a standard for wireless LANS was ratified by the Institute of Electrical and Electronics Engineers (IEEE) in the year 1997. This version of 802.11 provides for 1 Mbps and 2 Mbps data rates and a set of fundamental signaling methods and other services. Like all IEEE 802 standards, the 802.11 standards focus on the bottom two levels the ISO model, the physical layer and link layer. Any LAN application, network operating system, protocol, including TCP/IP and Novell NetWare, will run on an 802.11-compliant WLAN as easily as they run over Ethernet.  

The major motivation and benefit from Wireless LANs is increased mobility. Untethered from conventional network connections, network users can move about almost without restriction and access LANs from nearly anywhere. 

The other advantages for WLAN include cost-effective network setup for hard-to-wire locations such as older buildings and solid-wall structures and reduced cost of ownership-particularly in dynamic environments requiring frequent modifications, thanks to minimal wiring and installation costs per device and user. WLANs liberate users from dependence on hard-wired access to the network backbone, giving them anytime, anywhere network access.  
There are several specifications in the 802.11 family: 

  • 802.11 applies to wireless LANs and provides 1 or 2 Mbps transmission in the 2.4 GHz band using either frequency hopping spread spectrum (FHSS) or direct sequence spread spectrum (DSSS). 
  • 802.11a — an extension to 802.11 that applies to wireless LANs and provides up to 54-Mbps in the 5GHz band. 802.11a uses an orthogonal frequency division multiplexing encoding scheme rather than FHSS or DSSS. 
  • 802.11b (also referred to as 802.11 High Rate or Wi-Fi) — an extension to 802.11 that applies to wireless LANS and provides 11 Mbps transmission (with a fallback to 5.5, 2 and 1-Mbps) in the 2.4 GHz band. 802.11b uses only DSSS. 802.11b was a 1999 ratification to the original 802.11 standard, allowing wireless functionality comparable to Ethernet. 
  • 802.11e — a wireless draft standard that defines the Quality of service (QoS) support for LANs, and is an enhancement to the 802.11a and 802.11b wireless LAN (WLAN) specifications. 802.11e adds QoS features and multimedia support to the existing IEEE 802.11b and IEEE 802.11a wireless standards, while maintaining full backward compatibility with these standards. 
  • 802.11g — applies to wireless LANs and is used for transmission over short distances at up to 54Mbps in the 2.4 GHz bands. 
  • 802.11n — 802.11n builds upon previous 802.11 standards by adding multiple input & multiple output (MIMO). The additional transmitter and receiver antennas allow for increased data throughput through spatial multiplexing and increased range by exploiting the spatial diversity through coding schemes like Altamonte coding. The real speed would be 100 Mbit/s (even 250 Mbit/s in PHY level), and so up to 4-5 times faster than 802.11g. 
  • 802.11ac — 802.11ac builds upon previous 802.11 standards, particularly the 802.11n standard, to deliver data rates of 433Mbps per spatial stream, or 1.3Gbps in a three-antenna (three stream) design. The 802.11ac specification operates only in the 5 GHz frequency range and features support for wider channels (80MHz and 160MHz) and beam forming capabilities by default to help achieve its higher wireless speeds. 
  • 802.11ac Wave 2 — 802.11ac Wave 2 is an update for the original 802.11ac spec that uses MUMIMO technology and other advancements to help increase theoretical maximum wireless speeds for the spec to 6.93 Gbps. 
  • 802.11ad — 802.11ad is a wireless specification under development that will operate in the 60GHz frequency band and offer much higher transfer rates than previous 802.11 specs, with a theoretical maximum transfer rate of up to 7Gbps (Gigabits per second). 
  • 802.11r - 802.11r, also called fast basic service set (BSS) Transition, supports Vo Wi-Fi handoff between access points to enable VoIP roaming on a Wi-Fi network with 802.1X authentication. 
  • 802.1X — Not to be confused with 802.11x (which is the term used to describe the family of 802.11 standards) 802.1X is an IEEE standard for port-based Network Access Control that allows network administrators to restricted use of IEEE 802 LAN service access points to secure communication between authenticated and authorized devices. 


As long as you have all the hardware, you can quickly set up any wireless network. Here is everything you need to know about the hardware you need to have in place before you use Windows to configure the wireless network. 

There are two types of wireless networks: infrastructure and ad hoc. The infrastructure network is most likely the type of wireless setup you have in your home or office. It’s laid out similarly to a wired network, but without wires. 


Wireless router: The heart of the wireless network is the wireless router. Like a wire-based network, the hub is a central location that all computers connect to, providing the computers with network access. The wireless hubs now available also serve as routers. Well, officially, wireless hubs are gateways, not routers, but they're called routers. They’re also called access points, so get used to that term as well. Despite the nomenclature confusion, all you need to know is that the hub/router/access point is a smart little beast that helps manage wireless connections and also helps connect your wireless network to the Internet. 
Wire-based connections: Almost every wireless router I’ve seen has one or more standard, wire-based Ethernet port. One port is used to connect the router to a broadband modem. Other Ethernet ports might be also available, allowing you to connect standard wire-based networking to the wireless hub. 
Wireless NIC: Your computer needs a wireless network information card, or NIC, to talk with the wireless router. A laptop comes standard with a wireless NIC, but for a desktop PC you have to get a wireless NIC as an option. It’s installed internally as an expansion card, or you can use one of the various plug-in USB wireless NICs. 
That’s pretty much it for the infrastructure type of wireless network. 
The ad hoc type of wireless network is basically a group of wireless computers connected with each other. An ad hoc network has no central hub or router. Instead, all its computers can directly access the other computers’ files and shared resources. They may or may not have Internet access, but that’s not the point of the ad hoc network. 
  • One of the beauties of a wireless network is that you can mix in wired components as needed. If you need more Ethernet ports, for example, simply add a switch to the wireless router. 
  • Despite the wireless nature of wireless networking, you still need an Ethernet cable (a wire) to connect a wireless router to a broadband modem. 
  • Another advantage of a wireless network is that it’s portable. It’s far easier to pull up stakes with a wireless network than to pack up all the bits and pieces of a wired network. If you live in an apartment, or just move around a lot, a wireless setup a good option. 
  • The term access point is often abbreviated AP. Don’t be puzzled when you see the words wireless AP — it simply refers to the access point, not to the Associated Press. 
  • A wireless network is often called a WLAN, for wireless local-area network. 
  • A wireless network is also referred to by the term Wi-Fi. It stands for wireless fidelity. 
  • Ad hoc networks are often used by computer gamers to gather in a single location to play games with each other. 

An ad-hoc network is a local area network (LAN) that is built spontaneously as devices connect. Instead of relying on a base station to coordinate the flow of messages to each node in the network, the individual network nodes forward packets to and from each other. In Latin, ad hoc literally means "for this," meaning "for this special purpose" and also, by extension, improvised or impromptu. Ad-hoc mode is a method for wireless devices to directly communicate with each other. Operating in ad-hoc mode allows all wireless devices within range of each other to discover and communicate in peer-to-peer fashion without involving central access points (including those built in to broadband wireless routers). 

To set up an ad-hoc wireless network, each wireless adapter must be configured for ad-hoc mode versus the alternative infrastructure mode. In addition, all wireless adapters on the ad-hoc network must use the same SSID and the same channel number. 
Create an Ad Hoc network profile on computer A   

Step 1 Go to Control Panel -> Network Connections and find Wireless Network Connection. Right click Wireless Network Connection and select Properties. 

Step 2 On Wireless Networks tab, click Add button. 
Step 3 On Association tab of Wireless network properties window, please type a phrase for Network Name [SSID]. In our scenario, we take adhoctest for example. Then go to the bottom and tick this is a computer-to-computer [ad hoc] network; wireless access points are not used. Then click OK. 

Step 4 After Step 3, there should be a profile named adhoctest in Preferred Networks. Click OK to save all the settings

Part 2: Manually configure an IP address on computer A   

Step 5 Right click Wireless Network Connection and select Properties. 

Step 6: On General tab, please double click Internet Protocol (TCP/IP). 

Step 7: Tick Use the following IP address, and input the IP address and Subnet mask. Then click OK.

Step 8 Click OK on Wireless Network Connection Properties window. 

Part 3: Scan for Ad Hoc network on computer B   

Step 9 Right click Wireless Network Connection, select View available wireless networks 

Step 10 Find adhoctest(which is set up on computer A) network in the scan window. Then double click it and click connect anyway? 

Part 4: Manually configure an IP address on computer B The steps are the same as which were done on computer A (Step 5 to Step 8). The point is that we need assign a different IP address for computer B, and it must be in the same subnet with computer A. In our scenario, we can take 192.168.1.20/255.255.255.0. 
Here until, all the basic settings for building an Ad Hoc network have been finished. If we open the network scan window again, we can see the adhoc test network says Connected. 

INFRASTRUCTURE MODE: Infrastructure mode wireless networking bridges (joins) a wireless network to a wired Ethernet network while supporting central connection points for local wireless clients. Setting up an infrastructure mode network requires at least one wireless access point (AP). The AP and all local wireless clients must be configured to use the same network name (SSID). 

Infrastructure mode wireless networking bridges (joins) a wireless network to a wired Ethernet network while supporting central connection points for local wireless clients. Setting up an infrastructure mode network requires at least one wireless access point (AP). The AP and all local wireless clients must be configured to use the same network name (SSID). 
Wireless Router Configuration Steps 
Preparations: 
Please connect a computer to TP-LINK router by cable or through wireless network. 
It’s recommended to configure it by a wired connection. 
Step 1 
Log into the router’s web-based utility by typing 192.168.0.1(by default ID) in address bar of any browser or you can check the by default web address login ID & password in the user manual.  Get in to the wireless setup mode then Select Wireless->Wireless Settings on the left side menu to open the wireless setting page. 

 Wireless Network Name (also called SSID for some models): Create a new name for your wireless network. If you want to use the default TP-LINK_****** wireless name, you can also leave it here as default value. 
Region: Select your current location. 
"Enable Wireless Router Radio" and "Enable SSID Broadcast" should be both ticked.  
Please do not change other settings on this page if not necessary. 

Click Save to save your settings. 
Note: After clicking on save button, you will see a tip (red line) at the bottom of the page. But actually there is no need to reboot at here and we will reboot the router at the end of the configurations. 
Select Wireless->Wireless Security on the left side menu. It’s recommended to use WPA/WPA2 Personal (Recommended), some models will name that as WPA-PSK/WPA2-PSK instead. 

Version: WPA-PSK or WPA2-PSK 
Encryption:  AE
Wireless Password (also called PSK Password): make up your WI-FI password, also called Wireless Network Key.  
 If you want to use WEP as wireless security type, you need obey certain rules to create the wireless password. 
For 64-bit encryption - You can enter 10 hexadecimal digits (any combination of 0-9, a-f, A-F, and null key is not permitted) or 5 ASCII characters. 
For 128-bit encryption - You can enter 26 hexadecimal digits (any combination of 0-9, a-f, A-F, and null key is not permitted) or 13 ASCII characters. 
For 152-bit encryption - You can enter 32 hexadecimal digits (any combination of 0-9, a-f, A-F, and null key is not permitted) or 16 ASCII characters. 
Step 4 

Click Save button to save the settings 
Step 5 

Click here at the bottom of the page to reboot the router; or you can go to system tools, reboot to reboot the router to make all settings take effect. 

WEP, WPA, and WPA2: Wi-Fi Security through the Ages 

Since the late 1990s, Wi-Fi security algorithms have undergone multiple upgrades with outright depreciation of older algorithms and significant revision to newer algorithms. A stroll through the history of Wi-Fi security serves to highlight both what’s out there right now and why you should avoid older standards. 


Wired Equivalent Privacy (WEP) is the most widely used Wi-Fi security algorithm in the world. This is a function of age, backwards compatibility, and the fact that it appears first in the encryption type selection menus in many router control panels. 
WEP was ratified as a Wi-Fi security standard in September of 1999. The first versions of WEP weren’t particularly strong, even for the time they were released, because U.S. restrictions on the export of various cryptographic technology led to manufacturers restricting their devices to only 64-bit encryption. When the restrictions were lifted, it was increased to 128-bit. Despite the introduction of 256-bit WEP encryption, 128bit remains one of the most common implementations. 
Despite revisions to the algorithm and an increased key size, over time numerous security flaws were discovered in the WEP standard and, as computing power increased, it became easier and easier to exploit them. As early as 2001 proof-of-concept exploits were floating around and by 2005 the FBI gave a public demonstration (in an effort to increase awareness of WEP’s weaknesses) where they cracked WEP passwords in minutes using freely available software. 
Despite various improvements, work-around, and other attempts to shore up the WEP system, it remains highly vulnerable and systems that rely on WEP should be upgraded or, if security upgrades are not an option, replaced. The Wi-Fi Alliance officially retired WEP in 2004. 


Wi-Fi Protected Access was the Wi-Fi Alliance’s direct response and replacement to the increasingly apparent vulnerabilities of the WEP standard. It was formally adopted in 2003, a year before WEP was officially retired. The most common WPA configuration is WPA-PSK (Pre-Shared Key). The keys used by WPA are 256-bit, a significant increase over the 64-bit and 128-bit keys used in the WEP system. 
Some of the significant changes implemented with WPA included message integrity checks (to determine if an attacker had captured or altered packets passed between the access point and client) and the Temporal Key Integrity Protocol (TKIP). TKIP employs a per-packet key system that was radically more secure than fixed key used in the WEP system. TKIP was later superseded by Advanced Encryption Standard (AES). 
Despite what a significant improvement WPA was over WEP, the ghost of WEP haunted WPA. TKIP, a core component of WPA, was designed to be easily rolled out via firmware upgrades onto existing WEP-enabled devices. As such it had to recycle certain elements used in the WEP system which, ultimately, were also exploited. 
WPA, like its predecessor WEP, has been shown via both proof-of-concept and applied public demonstrations to be vulnerable to intrusion. Interestingly the process by which WPA is usually breached is not a direct attack on the WPA algorithm (although such attacks have been successfully demonstrated) but by attacks on a supplementary system that was rolled out with WPA, Wi-Fi Protected Setup (WPS), designed to make it easy to link devices to modern access points. 
Wi-Fi Protected Access II (WPA2) 
WPA has, as of 2006, been officially superseded by WPA2. One of the most significant changes between WPA and WPA2 was the mandatory use of AES algorithms and the introduction of CCMP (Counter Cipher Mode with Block Chaining Message Authentication Code Protocol) as a replacement for TKIP (still preserved in WPA2 as a fallback system and for interoperability with WPA). 
Currently, the primary security vulnerability to the actual WPA2 system is an obscure one (and requires the attacker to already have access to the secured Wi-Fi network in order to gain access to certain keys and then perpetuate an attack against other devices on the network). As such, the security implications of the known WPA2 vulnerabilities are limited almost entirely to enterprise level networks and deserve little to no practical consideration in regard to home network security. 
Unfortunately, the same vulnerability that is the biggest hole in the WPA armor, the attack vector through the Wi-Fi Protected Setup (WPS), remains in modern WPA2-capable access points. Although breaking into a WPA/WPA2 secured network using this vulnerability requires anywhere from 2-14 hours of sustained effort with a modern computer, it is still a legitimate security concern and WPS should be disabled (and, if possible, the firmware of the access point should be flashed to a distribution that doesn’t even support WPS so the attack vector is entirely removed). 

  • Identify wireless Network components 
  • Install WI-FI router. 
  • Provide Wi-Fi SSID & give password & test whether the configuration is working or not. 

a) 2.4Gbps 
b) 5Gbps 
c) 2.4GHz 
d) 5GHz 


a) 3 
b) 12 
c) 23 
d) 40 


a) 6Mbps 
b) 11Mbps 
c) 22Mbps 
d) 54Mbps 


a) 2.4Gbps 
b) 5Gbps 
c) 2.4GHz 
d) 5GHz 


a) 3 
b) 12 
c) 23 
d) 40 


a) WCS 
b) Controller 
c) Access point 
d) Bridge

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