Hotspot in WiFi Network

A hotspot is any location where Wi-Fi network access (usually Internet access) is made publicly available. You can often find hotspots in airports, hotels, coffee shops, and other places where business people tend to congregate. Hotspots are considered a valuable productivity tool for business travelers and other frequent users of network services.Technically speaking, hotspots consist of one or several wireless access points installed inside buildngs and/or adjoining outdoor areas. These APs are typically networked to printers and/or a shared high-speed Internet connection. Some hotspots require special application software be installed on the Wi-Fi client, primarily for billing and security purposes, but others require no configuration other than knowledge of the network name (SSID).

TraceRoute command

Traceroute is a utility program that monitors the network path of test data sent to a remote computer. On Unix and Linux computers, the "traceroute" application is available in the shell, while on Windows computers, the "tracert" program can be accessed from DOS.Traceroute programs take the name or IP address of a remote computer on the command line. When run, traceroute sends a series test messages over the network (using ICMP) to each intermediate router progressing until the last message finally reaches its destination. When finished, traceroute displays the ordered list of routers that represent the path from that computer to the destination.

What is Apache Web Servers

Apache is generally recognized as the world's most popular Web server (HTTP server). Originally designed for Unix servers, the Apache Web server has been ported to Windows and other network operating systems (NOS). The name "Apache" derives from the word "patchy" that the Apache developers used to describe early versions of their software.The Apache Web server provides a full range of Web server features, including CGI, SSL, and virtual domains. Apache also supports plug-in modules for extensibility. Apache is reliable, free, and relatively easy to configure.Apache is free software distributed by the Apache Software Foundation. The Apache Software Foundation promotes various free and open source advanced Web technologies.
Following commands are usefull to install apache and phpmyadmin with
1.Installing Mysql:
yum install mysql mysql-server
chkconfig --levels 235 mysqld on
/etc/init.d/mysqld start
 mysqladmin -u root password servertest //this is the root and its password that you required when first time login in phpmyadmin here "root" is user and "servertest" is password
2.Installing Apache2:
yum install httpd
chkconfig --levels 235 httpd on
/etc/init.d/httpd start
3.Installing PHP5:
yum install php
/etc/init.d/httpd restart
4.Getting MysQl support in PHP5:
yum search php
yum install php php-mysql php-common php-gd php-mbstring php-mcrypt php-devel php-xml php-xmlrpc
/etc/init.d/httpd restart
5.Installing phpMyAdmin:
cd /var/www/html
wget http://sourceforge.net/projects/phpmyadmin/files/phpMyAdmin/2.11.11.1/phpMyAdmin-2.11.11.1-english.tar.gz
tar xvfz phpMyAdmin-2.11.11.1-english.tar.gz
mv phpMyAdmin-2.11.11.1-english phpmyadmin
cd phpmyadmin
cp config.sample.inc.php config.inc.php
nano config.inc.php
a file will open just type and replace,cookies,with,http,
service httpd restart

Cisco fastest router

Cisco launches super fast router.....

NETWORKING HARDWARE VENDOR Cisco announced a router that it thinks could change the world wide web for evermore.The company said its glorious CRS-3 carrier-grade router is designed to serve as the foundation of the next-generation Internet, as it can manage speeds of up to 322 Terabits per second.

Just so the great unwashed know, that is fast enough to transmit the entire printed collection of the US Library of Congress in one second, or the bandwidth required for every man, woman and child in China to make a video call, simultaneously. Every movie ever created could be streamed in less than four minutes, Cisco claims.

Of course it is just a router and not the entire world wide web infrastructure, but it has more than 12 times the traffic capacity of anything else out there.Cisco says that it will make Internet and cloud services much more efficient. It mentions that AT&T recently tested the Cisco CRS-3 during the world's first field trial of 100-Gigabit backbone network technology, which took place over AT&T's live network between New Orleans and Miami recently.

The CRS-3 machine will replace the firm's CRS-1 router, which is still one of the most popular and fastest available commercial routers. The CRS-3 is three times faster than the CRS-1.The firm says its latest top of the line carrier-grade router is powered by its Quantumflow Array Processor, which unifies the combined power of six communications processor chips to work as one. This apparently will deliver high service capabilities and processing power. It also will require only a fraction of the power.

Address Binding Technique 3

Address Resolution with message exchange: In this approach the computer that needs to resolve an address sends a message across network and receives reply.The message carries a request that specifies the protocol address,and the reply carries the corresponding hardware address.Now the main question that came in front of us is that where all these requests be sent.Generally there are two designs that are used for this.In the first design a network includes one or more servers that are assigned the task of answering address resolution requests.

Whenever,address resolution is needed a message must be sent to any of these servers which will send a reply.In the second design no special address resolution servers are needed.Instead,each computer on the network participates in address resolution by agreeing to answer resolution requests for its address.When a computer needs to resolve an address,it broadcasts a request on the network.All machine receive the request and examine the requested address.If an incoming request matches a computer’s address, the computer responds.Now discuss the advantages of both the designs.

The chief advantage of the first scheme arise from centralization because a few address resolution servers handle all resolution tasks on the network,address resolution is easier to configure,manage and control.Now the advantage of second design arise from distributed computation.Address resolution servers may be expensive.In addition to the expense of additional hardwares like extra memory.In addition to this servers are expensive to maintain because address binding information stored in servers must be updated whenever new computers are added to the network or hardware address changes.Furthermore ,address resolution servers can become a bottleneck on a large busy network.If each computer is able to resolve its own address ,then there is no need of servers.

Address Binding Technique 2

Address Resolution with closed form computation: As all we know that many network technologies use static physical addresses, some technologies use configurable addressing in which a network interface can be assigned a specific hardware address. For such type of networks it is possible that we can choose addresses that make closed form address resolution possible.A resolver that uses a closed form method computes a mathematical function that maps an IP address to its equivalent hardware address. If the relationship between the IP address and its coprresponding hardware address is straightforward, the computation requires only a few arithmetic operations.Infact,the host portion of a computer’s IP address can be chosen such that it is identical to the computer’s hardware address.

Let’s understand this situation with the help of a example, suppose a configurable network has been assigned the network address 220.123.152.xxx and its suffix ranging from 0-24. As computers are added to the network, each computer is assigned an IP address from this range and a matching hardware address.The first host is assigned an IP address 220.123.152.1 and hardware address 1. The second host is assigned an IP address 220.123.152.2 and hardware address 2. The suffixes need not be sequential, if a router attached to a network assigned IP address202.123.152.101,then the router is assigned an IP address of 121.Given the IP address of any computer on the network, the computer’s hardware address can be computed by a single Boolean ‘and’ operation.

Hardware Address=IP Address & 0xff

As I think it is clear from the example that why closed form resolution is often used with configurable networks.

Address Binding Technique 1

1.Address resolution with table lookup: This technique of address resolution requires a data structure that contains information about address binding. The table consists of an array. Each entry in the array contains a pair (P,H),where P is the protocol address and H is its corresponding hardware address. The main advantage of table lookup approach is generality- a table can store the address bindings for an arbitrary set of computers on a given network. In particular a particular protocol address can map to an arbitrary hardware address.

Furthermore, the table lookup algorithm is straight forward and easies among all the approaches. Suppose we have given a next-hop address, N, the software searches the table until it finds an entry where the IP address matches N. The software then extracts the hardware address from the entry.For a network that contains a less then dozen of hosts, a sequential search is sufficient ,the resolution software begins at first entry and searches each entry in table until a match is found. But for large networks this sequential search is not possible because it consumes excessive CPU time. In these type of situations to improve computational efficiency we can use Hashing or Direct Indexing.
As all we know that Hashing is a general purpose data structure and is well known to all the programmers, so, here I am not going to discuss it. Let’s take a look at the other technique that is of Direct Indexing. Direct Indexing is slightly more efficient but less general technique. In particular Direct Indexing is possible only in those cases where protocol addresses are assigned from a compact range.
For Example
Direct Indexing can be used with IP addresses that are arranged in sequential order. In these type of cases the software maintains a one dimensional array of hardware addresses, and uses the host suffix from an IP address as an index to an array.
In the next post I will tell you the second technique of Address Binding.