1a. The American Registry for Internet Numbers (ARIN) is the nonprofit corporation responsible for managing Internet number resources IPv4 and IPv6 addresses for Canada, many Caribbean and North Atlantic islands and the United States.
Because Internet addresses must be unique and because address space on the Internet is limited, there is a need for some organization to control and allocate address number blocks. IP address management was formerly a responsibility of the IANA, which contracted with Network Solutions Inc. for the actual services. In December 1997, IANA turned this responsibility over to ARIN, which, along with Reseaux IP Europeans (RIPE), APNIC, LACNIC and AfriNIC, now manages the world's Internet address assignments and allocation
B. .The Internet Assigned Numbers Authority (IANA) is a department of ICANN responsible for coordinating some of the key elements that keep the Internet running smoothly. Whilst the Internet is renowned for being a worldwide network free from central coordination, there is a technical need for some key parts of the Internet to be globally coordinated, and this coordination role is undertaken by IANA.
Specifically, IANA allocates and maintains unique codes and numbering systems that are used in the technical standards (“protocols”) that drive the Internet.
IANA’s various activities can be broadly grouped in to three categories:
 Domain Names
IANA manages the DNS Root, the .int and .arpa domains, and an IDN practices resource.
 Number Resources
IANA coordinates the global pool of IP and AS numbers, providing them to Regional Internet Registries.
 Protocol Assignments
Internet protocols’ numbering systems are managed by IANA in conjunction with standards bodies.
IANA is one of the Internet's oldest institutions, with its activities dating back to the 1970s. Today it is a set of services provided by the Internet