addresses have not been allocated efficiently, leading to waste
public address supply is exhausted
IPv6 is designed to mitigate address exhaustion
128-bit addressing scheme has 340 undecillion unique addresses
only a small portion can currently be allocated to hosts
still enough space for every person on earth to own 4,000 address
consists of 2 or 3 elements:
main header
fixed length
fields for source and destination addresses
field for version (0110 or 0x06 for IPv6)
one or more optional extension headers
replace the Options field in IPv4
several predefined extension headers
cover functions such as fragmentation and reassembly, security (IPSec), source routing, etc.
payload
Other header fields include:
Field
Explanation
Traffic Class
Describes the packet’s priority.
Flow Label
Used for quality of service (QoS) management, such as for real-time streams. This is set to 0 for packets not part of any delivery sequence or structure.
Payload Length
Indicates the length of the packet payload, up to a maximum of 64 KB; if the payload is bigger than that, this field is 0, and a special Jumbo Payload (4 GB) option is established.
Next Header
Used to describe what the next extension header (if any) is, or where the actual payload begins.
Hop Limit
Replaces the TTL field in IPv4 but performs the same function.