Implementation(2) API extension

Use sin6_scope_id to specify a scope (i.e. link) ID
kernel sends a packet to the link specified by sin6_scope_id
kernel sets a link ID of a received packet to sin6_scope_id 

KAME's getaddrinfo supports the extended format
takes an address as a hostname in the extended format
sets the according scope ID to the sin6_scope_id field

getnameinfo is also extended
takes sockaddr_in6{}
returns a literal address in the extended format.