Encrypted security payload header. Destination options header. 647 IPv6 Extension Headers. Allows more control of Fragmentation and Reassembly, which has very high overhead in IPv4. Allows better routing because routers can include information in each datagram as they are routed.
Helps insure prompt delivery.
A way to transfer information to the destination device without using ICMP or a separate datagram to do so. Expands the address space to 128-bits. Simplifies the IP header to reduce overhead. Enhances functionality by adding Extension Headers. Actual or virtual leased-line between two locations.