Internet Adress

What is IP Address ?

• A number that uniquely identifies each computer or device connected to the Internet.
• IP addresses are also referred to as IP numbers and Internet addresses.
• IP address sometimes is called a dotted decimal number or dotted quad.

IP usage :

• A way to find specific server or computer on the internet or a network.
• Provide identity to a computer in a network.
• Identify for a particular device/machine on a particular network.
• Allows transfers of files and e-mail.

IP structure :

• IP addresses usually consists of four groups of number each separated by a period.
• The number in each group is between 0 and 255.
• It is 32 bit long ,each group is 8 bits long
• Commonly written in decimal.
• Written, for example, 128.35.0.72
• These four sections represent the machine itself and the network it is on.
• The network portion is assigned.
• The host section is determined by the network administrator.
• 5 Classes of IP address A,B,C,D, and E :
• Class A : reserved for governments/ large companies
• Class B : reserved for medium companies
• Class C : reserved for small companies
• Class D : are reserved for multicasting
• Class E : are reserved for future use

• IP address classified in which of bits are used to identify network, network ID, host ID, host computer
• You can determine which class any IP address is in by examining the first 4 bits of the IP address. 

IP Addresses :

• IP addresses are:
• Unique
• Global and Standardised
• Essential

IP versions :

• Two versions of the Internet Protocol (IP) are in use:
• IP Version 4 (IPv4)
• IP Version 6 (IPv6)

a. IP Version 4 (IPv4) :

• IPv4 an address consists of 32 bits which limits the address space to 4294967296 (232) possible unique addresses.

b. IP Version 6 (IPv6) :

• The address size was increased from 32 to 128 bits or 16 octets.
• Provides the potential for a maximum of 2128, or about 3.403×1038 unique addresses.

Domain names and IP addresses :

• People prefer to use easy-to-remember names instead of IP addresses 
• Domain names (a part of the URL) are alphanumeric names for IP addresses.
• e.g., neon.ece.utoronto.ca, www.google.com, ietf.org
• The domain name system (DNS) is an Internet-wide distributed database that translates between domain names and  IP addresses

How important is DNS? 

• Imagine what happens when the local DNS server is down.

Internet Address

• Domain name : The text version of an IP address
• Generally,
• First portion of each IP address identifies the network.
• Last portion identifies the specific computer.

Domain Name System (DNS) :

• IP address and domain name allocation requires central administration to avoid duplication.
• Previously administered by U.S. government contract (NSI)
• In 1998, technical coordination assigned to ICANN (Internet Corporation for Assigned Names and Numbers).

ICANN is the official organization that coordinates domain names on the World Wide Web. ICANN is also responsible for approving or denying new domain extensions.

Top-Level Domains (TLDs) :

• The first-level set of domain names are the top-level domains (TLDs).
• Three types of top-level domains : Organizational, Geographical, and Reverse Domains.
• There are more than 200 top-level domains.

Generic Top-level Domains (gTLD) :

• A generic top-level domain (gTLD) is one of the categories of top-level domains (TLDs) maintained by the internet Assigned Numbers Authority (IANA) for use in the Domain Name System of the Internet.