IP Address

Published on January 2017 | Categories: Documents | Downloads: 49 | Comments: 0 | Views: 467
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Internet Protocol - IP Address is the number that denotes the Computer connecting to the Internet. It is given out by the ISP, in this case it is BSNL. There are two types of IP Addresses. Public and Private. When Internet Protocol (IP) was designed in the 1970s, the IP address defined contained 32 bits or 4 - eight bit characters, which results in 4 Billion destinations. At that time they thought 4 Billion Computers on the network will never exist. However, in reality the way IP Network exists the number of computers that exist will be much less. Out of this 4 Billion Address space, USA uses more than 70% - 80% of IP addresses. The rest of the world has only 20-30% of IP addresses! The shortage started occurring in the 1990s. Therefore IP address is scarce commodity in the world today. Several schemes were defined in the 1990s to address the shortage. Two of those important schemes are DHCP & NAT. DHCP is Dynamic Host Control Protocol – is simply that the IP Address is NOT permanently allocated to ONE Computer. An IP address is given to the Computer whenever it connects to the Internet. That way a small pool of IP addresses are shared by many computers. However, this means that the Computers are NOT ALWAYS connected to the Internet. This is typically how ‘DIAL-UP’ Computers are connected. Whenever the Computers ‘Dials-up’ and connects a DHCP IP address is given. When the computer disconnects that IP address goes back into the pool and then is reassigned to anyone who connects. In India, most connections use this option. You can see that limitation imposed by Hathaway or BSNL. You can buy 100 Hours for Rs600. You can use that 100 Hours in one week or 3 months. However, when you use ‘Broadband’ you are ‘ALWAYS ON’/CONNECTED. So an IP address is necessary. There are two types of ‘Always On’ IP addresses – DHCP & STATIC. DHCP means it is Dynamic, the address may change whenever the Broadband disconnects and reconnects at anytime. This can be because of power failure, equipment failure or any other vendor or site related incident. Static IP – Address – A Permanent IP address is allocated to a specific location. Any Computer that connects at that location assumes that IP Address. For example, my office at Verizon has a STATIC IP Address. Even when I am not in office or turned of the computer that IP address can’t be used by anyone else. That is because Verizon owns more than 500 Million IP addresses, their whole network uses real IP Addresses (yes, Verizon runs 40%

of the Internet). But in the real world, like India, the whole country of India may have less than 50 million IP addresses available. This is a very expensive option, because only limited IP addresses are available. Who needs a STATIC Address? Anyone who needs a permanent presence on the Internet. When others want to reach them, the destination IP address must be the same. For example, WWW.MCC.EDU may translate to a STATIC IP address of the Server at MCC. If they use DHCP and the IP Address keeps changing then, no one can reach it. So when someone sets up a server like that they need a STATIC IP Address. The other scheme used to address the IP address scarcity is NAT. Network Address Translation (NAT). Basically, a computer/router maintains a Table of IP address and substitutes the IP address for data packets traffic flow instead of actual computers. The Router has connection to two Networks. On one side it runs a IP Network called ‘INSIDE Network’ or Local LAN with a small IP address, that can never be reached on the Internet called Private IP Address. On the other side it connects the Internet of the using REAL IP Addresses. The IP Protocol defines three such ‘sub spaces’ as PRIVATE/RESERVED and not available in the general Internet. These are any address starting with 10.X.X.X, 172.16.X.X, 192.168.X.X. On the INSIDE Network the Router using DHCP or Static allocates IP addresses to all the Computers on the Network. The Computers only KNOW how to reach the Router and send traffic to the Router. The Router then assigns a ‘real IP Address’ for the Request and sends it to the Internet as if the request actually came from a real computer on the Internet. When the response comes back the Router strips the real IP address and sends the response back to the original computer from which the request came. So whenever, the traffic is flowing the Router maintains a table of requests and when the response comes it knows where to send the response. This automatically acts like a firewall. Generally, hackers will send requests to any IP address. Since the IP address is public, any computer can send a request to anyone. When the hacker sends a request to the IP address the Router is using to send out requests, it doesn’t know where to send this request (since it came from outside world), there is no corresponding entry in the table. So the Request Flow is always from INSIDE to OUTSIDE. No UNSOLICITED requests from OUTSIDE/INTERNET can reach the Computers inside. That way they are protected from hacking, that is the function of a firewall. Therefore, behind the Router which acts like a Firewall, you can have a whole IP network and use only one REAL IP Address to reach the entire Internet. Depending up on the Router type/size you can have anywhere from 252 to 16

Million computers on the Inside network. The small cheap Routers costing less than $100 (Rs5000), you can have up to 252 computers. Sometimes ISPs like Hathaway actually do that and when you ‘DIAL IN’ you connect to the local LAN (INSIDE) network of the Hathaway Router and you may not even be ON the Internet directly. I know this because I saw this in Hyderabad in my house the Hathaway ISP connection gave an IP address of 10.X.X.X to the computer which means that I was on the INSIDE Network of the Hathaway Router. Is it Legal? Well that is how ISPs in India are operating. When such connections are given, you are sharing with many other users and your speeds are unpredictable. I think VSNL/BSNL may actually put you on the Internet by giving a Real Dynamic IP Address.

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