FRAGMENTATION AND PATH MTU
IPv6 source is responsible for fragmentation. Routers simply drop datagrams bigger than network MTU. So source have to fragment datagram to arrive destination.
Source calculates path MTU. The smallest MTU on any network between destination and source and it fragments datagram to fix within that MTU.The process of learning the path MTU is called as path MTU discovery. Source transmits probe message of different sizes until destination arrived. It have to be dynamic i.e. path may modify during transmission of message.
USE OF MULTIPLE HEADERS:
It has given advantages: