• Exhaustion of IPv4 address space
• Enabling end-to-end global addressing
• Securing IPv6 in your own "IPv4 only" network
• Simplify ability for early adopter-only access networks to reach your content
• New applciations: sensors, logistics, transport, etc

• Architectural
• 128-bit addresses
• Support for billions more devices online
• Potential to restore end-to-end capability
• Removal of the need for NAT
• Technical
• Network (IP configuration) plug and play
• Stateless Address Autoconfiguration
• Steamlined, extensible IPv6 header
• Fragmentation only at sender

• Less fields, with a fixed header size
• Concept of a chain of headers
• One header per function e.g:
• Authentication header
• Fragmentation header
• The 'next header' field links headers together
• In theory, one cen define new headers
• In practice, tricky due to firewall considerations

• Unicast: one to one
• Multicast: one to many
• New. Various scopes of addresses are defined
• Link-local addresses - used only on local subnets
• Uses prefix fc00::/7
• Global addresses - globally unique and routable

• An IPv6 address in the block fc00::/7.
• Approximate counterpart of the IPv4 private address
• Not accessible in the global IPv6 Internet
• In IPv6 hosts may routiney be multi-addressed
• One or more global IPv6 address(es)
• One IPv6 link-local address
• Possibly a ULA

• IPv6 has enough address space not to require Network address translation purely for address conservation
• MIght still be implemented for 'Security benefits'
• Using ULAs doesn't imply you have to use IPv6 NAT
• If hosts have global address from ISP and ULA:
• They can use their ULA to talk internally
• Can use their global address to talk externally
• If they change ISP, and their global address has to change, the use of ULAs keeps internal communications stable

• For both IPv4 or IPv6
• An IP address to use
• The size of the local subnet (prefix size)
• The default router to use on the local subnet
• DNS server(s)/resolver(s) to use
• In IPv4 you can use
• Manual configuration (Typically for servers)
• or Dynamic Host Configuration Protocol (DHCP)

• IPv6 hosts can also autoconfigure basic network settings without the need for a stateful DHCP server
• IP address
• Default gateway
• An IPv6 Host using SLAAC by default builds its address from:
• An advertised 64-bit(/64) network prefix
• A 64-bit host part generated based on MAC
• Prefix information is advertised by a router, either
• Periodically (Typically every 600 seconds)
• Request (node sends Router Solicitation request)
• The Advertisement is multicast on the local subnet

Host sees or solicits a RA from router - the response includes:

• RA message carries the network prefix to use
• RA (link-local) source address implies default router
• RA can indicate if a DHCPv6 service is available
• DNS server information can be included in RA

• Host's Ethernet (MAC) address is 08:00:20:9c:14:66
• The network prefix in the RA is 2001:630:80:200::/64
• Address is 2001:630:80:200:0a00:20ff:fe9c:1466
• A MAC address is 48 bits, ehnce the fffe 16-bit padding
• the "0a" is the globally unique EUI-64 bit being set

• MAC address is being embeded in the autoconfigured IPv6 address
• If device moves between networks, its prefix changes but the 64-bit identifier part remains the same
• Device can be tracked over time
• Privacy extensions instead use a random host part
• Generated when device joins network - and changes over time
• Also applies to static hosts - generates new privacy address periodically
• Increases complexity

• Router Advertisements
• Neighbour solicitation/advertisements 
• Similar to ARP

• Post-scanning is common in IPv4
• In IPv4 one port per subnet is 5 minutes (256 addresses)
• In IPv6 it is 500 billion years (2^64 hosts per subnet)
• There are ways to narrow search space
• 'Security through obscurity'

• Dual Stack
• Translation Methods (IPv4-only to IPv6-only)
• Rewriting IP header information
• Application layer gateways (ALGs)
• Tunnels
• IPv6 traffic encapsulated in IPv4 packets
• router-to-router or host-to-router

• Run both protocols on same equipment
• May need to rewrite/port existing applications
• Need to choose when to use IPv4 or IPv6
• Assumes enough IPv4 addresses are available
• Need to secure both protocols

Encapsulate IPv6 packet as payload/data of an IPv4 packet, usually manually configured on two routers

IPv4 packets carry IPv6 packets as their data