IPv6

1
IPv6

• 2004. 11. 3
• 20000515 Ha, Kiryong

2
IPv6

• Motivation
• The 32bit IP address space was beginning to be
  used up.
• IP node being attached to the Internet at a
  breathtaking rate.

3
IPv6 Datagram Format

• Version
• Putting 4 in this field do not make IPv4 (Life is
  not easy like that)
• Traffic class
• Similar in spirit to the TOS in IPv4
• Flow label
• Used to identify a flow
• Payload length
• Number of bytes following header
• Next Header
• Identify the protocol which the contents (data
  field) of this datagram will be delivered (ex.
  TCP, UDP)
• Hop limit
• Source and destination address
• Data

4
IPv6 Datagram Format

• Feature
• Expanded addressing capabilities
• 32 bit ? 128 bit
• 340,282,366,920,938,463,463,374,607,431,768,211,45
  6
• New type of address any cast which allows a
  datagram addressed to an anycast address to be
  delivered to any one of a group of hosts
• A streamlined 40-byte header
• 40-byte fixed-length header allows for faster
  processing of the IP datagram
• Flow labeling and priority
• Allows labeling of packets belonging to
  particular flows for which the sender request
  special handling
• Audio Video transmission. High-priority user

5
IPv4 vs IPv6 Format

• Fields appearing only in IPv4
• Fragmentation/Reassembly
• Do not allow fragmentation and reassembly at
  intermediate routers ? Performed only in source
  and destination
• If too large to be forwarded, simply drop and
  send ICMP error message
• Removing this function speeds up IP forwarding
  within the network
• Header checksum
• Transport layer and Internet link layer perform
  check sum ? Redundant work
• Again, speeds up. ( checksum was performed every
  router inIPv4 )
• Options
• Allowed but outside of header, indicated by Next
  Header field

6
A new ICMP for IPv6

• A new ICMP for IPv6
• ICMP protocol is used by IP nodes to inform error
  conditions and provide limited information to an
  end system.
• ICMPPv6 added new types and code for IPv6
• Packet Too Big type
• Unrecognized IPv6 options
• Subsumes IGMP protocol

7
Transitioning from IPv4 to IPv6

• Not all routers can be upgraded simultaneous
• How will the public Internet be transitioned to
  IPv6?
• Dual Stack allow IPv4 and IPv6 to co-exist in
  the same devices and networks
• Tunneling avoid order dependencies when
  upgrading hosts, routers, or regions
• Translation allow IPv6-only devices to
  communicate with IPv4-only devices

8
Transitioning from IPv4 to IPv6

• Dual Stack
• Introduce IPv6-capable node, which also have a
  complete IPv4 implementation
• Use IPv4 when interoperating with IPv4 node, and
  use IPv6 when interoperating with IPv6.
• Using DNS, determine whether another node is
  IPv6-capable or IPv4 only.
• Problem IPv6-specific fields which do not have
  counter part in IPv4

9
Transitioning from IPv4 to IPv6

• Refer to the intervening set of Ipv4 routers
  between two IPv6 routers as a tunnel
• Within the tunnel, Put entire IPv6 datagram in
  the data field of an IPv4 datagram and Extract
  IPv6 datagram

10
Conclusion

• Adoption of IPv6 has been slow to take off
  because of advances such as CIDRized IPv4
  address, DHCP, NAT contributed toward solving
  depletion of IPv4 addresses.
• Proliferation of devices such as IP-enabled
  phones may push for more widespread deployment of
  IPv6
• One important lesson How enormously difficult
  to change network-layer protocol