【71-75】thede facto standard application program interface （api） for TCP/ip applicationsis the“sockets”interface. although this api was developed for （71） in the early 1960s it has also beenimplementedon a widevariety of no-unix systems. TCP/ip （72） writtenusing the sockets api have in the pastenjoyeda high degree of portability andwe would like the same（73） with IPv6applications. but changesarerequiredto the sockets api to support IPv6 andthis memo describes these changes. these include a new socketaddress structureto carry IPv6 （74） ，new address conversion functions，and some new socket options.theseextensions are designed to provide access tothe basic IPv6 features requited by TCP and UDP applications，includingmulticasting， while introducing a minimums of change into the system and providingcomplete（75）for existing IPv4 applications.
