IANA- The Internet Assigned Numbers Authority is the entity that oversees global IP address allocation, autonomous system number allocation and other Internet Protocol-related numbers. IANA is operated by ICANN.  Originally, all the IPv4 address spaces were managed directly by the IANA. Later parts of the address space were allocated to various other registries to manage for particular purposes or regional areas of the world.
 
 ICANN - The Internet Corporation for Assigned Names and Numbers is responsible for managing the Internet Protocol address spaces (IPv4 and IPv6) and assignment of address blocks to regional Internet registries, for maintaining registries of Internet protocol identifiers, and for the management of the top-level domain name space (DNS root zone), which includes the operation of root nameservers.
 
IRR - The Internet Routing Registry is a database of Internet route objects for determining, and sharing route and related information used for configuring routers, with a view to avoiding problematic issues between Internet service providers.
 
LNR – A legacy number resource is an IPv4 address or Autonomous System number that was issued by an Internet Registry (InterNIC or its predecessors) prior to the inception of ARIN on Dec. 22, 1997. These resources are not covered by a Registration Services Agreement with ARIN. A legacy resource holder is any individual or organization that was directly issued legacy number resources, not their assignees.
 
LRSA - The Legacy Registration Services Agreement is offered to those organizations and individuals in the ARIN service region who hold legacy Internet number resources not covered by any other Registration Services Agreement with ARIN.
 
NRO- Number Resource Organization is an unincorporated organization uniting the five RIRs.  The main aims of the NRO are to:   
  • Protect the unallocated IP number resource pool,
  • Promote and protect the bottom-up policy development process of the Internet, and
  • Act as a focal point for Internet community input into the RIR system.
RIR – The Regional Internet Registries is an organization that manages the allocation and registration of Internet number resources within a particular region of the world. Internet number resources include IP addresses and autonomous system (AS) numbers.  There are five RIRs:
  • African Network Information Centre (AfriNIC) for Africa
  • American Registry for Internet Numbers (ARIN) for the United States, Canada, and several parts of the Caribbean region.
  • Asia-Pacific Network Information Centre (APNIC) for Asia, Australia, New Zealand, and neighboring countries
  • Latin America and Caribbean Network Information Centre (LACNIC) for Latin America and parts of the Caribbean region
  • Réseaux IP Européens Network Coordination Centre (RIPE) for Europe, the Middle East, and Central Asia