Networking

TCP IP – How it works

Many computer users have heard about something called an IP address in relation to how they get on the Internet and so forth. Also, many if they have been on the phone with their ISP tech support may have been asked to check settings having to do with their IP address. What exactly is TCP/IP and what is an IP address?

TCP/IP is Transmission Control Protocol/Internet Protocol. TCP/IP or IP for short is the protocol that the Internet and most computer networks are based on. In the tutorial on DNS, you will read about the analogy of DNS being likened to a phone book which has the numbers translated to names so we don’t have to remember every IP address that is equivalent to a website address we may want to visit or connect to. IP addresses are like the phone numbers in that analogy. They are the unique address of a computer or other network node on a network. IP version 4 which is still by far the most used addressing standard is notated in the format of 4 octets. For instance an IP v4 address would be something like 192.168.1.1 where each octet is separated by a decimal.
IP addresses are unique in a relative sense on every network. A technology widely in use today is called NAT or Network Address Translation. NAT allows a router or some other device to “translate” one IP address into another IP address. So 192.168.1.1 might become a completely different Internet facing address. Likely NAT’ing has saved the TCP/IP v4 standard from address exhaustion as the number of IP addresses has steadily been dwindling down over the years with the explosion of websites, domain names, and devices.

Most home networks these days are behind a consumer level router from a company such as Netgear, Dlink, or Linksys. Most routers are configured to NAT the address of your home network devices so that they use what is called a Private IP address range. These ranges have been set aside by RFC standards:

RFC1918 name IP address range number of addresses classful description largest CIDR block (subnet mask) host id size
24-bit block 10.0.0.0 – 10.255.255.255 16,777,216 single class A 10.0.0.0/8 (255.0.0.0) 24 bits
20-bit block 172.16.0.0 – 172.31.255.255 1,048,576 16 contiguous class Bs 172.16.0.0/12 (255.240.0.0) 20 bits
16-bit block 192.168.0.0 – 192.168.255.255 65,536 256 contiguous class Cs 192.168.0.0/16 (255.255.0.0) 16 bits

Home users as well as business organizations alike can utilize these ranges for addressing devices on networks and then using a public facing IP Address to use as their public presense IP Address.

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