Computer Networks

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Computer Networks
IPv6
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Motivation

• The primary motivation from changing the IP
  datagram format is to increase the size of the
  useable address space from 32 bits to 128 bits.
  Secondary reasons include routing improvements,
  simplicity in header format and even to bring
  back some of the end-to-end principles that are
  being lost due to NAT and firewalls.

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IPv6

• Standardized in RFC 2460
• Extends Addresses from 32 to 128 bits
• Streamlined header format
• Routers no long fragment packets
• New flow labeling capability
• Enhanced options design

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IPv6 Header Format
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Options Move Out
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Various Protocol Changes

• ICMP Streamlined
• IGMP now part of ICMP
• Changes to upper layers
• New DNS record type AAAA
• RIPv6
• OSPFv6

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Fragmentation Changes

• Fragmentation is no long done by routers
• Hosts musts discover the path MTU
• This is a significant change from IPv4!

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Addressing Changes

• Using IPv4 dotted decimal notation
• 105.220.136.100.255.255.255.255.0.18.128.140.10.25
  5.255
• IPv6 uses colon hexadecimal notation
• 69dc8864ffffffff012808c0affff
• With zero compression
• ff0c000000b1 becomes ff0cb1
• IPv4 addresses start with 96 zeroes
• No more broadcast, new anycast address

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Address Assignment

• Standard assignments
• IPv4 compatibility
• IPX addresses
• Link, site and multicast addresses
• Auto configuration
• Serverless autoconfiguration is possible
• Simple renumbering is possible

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Making the Transition

• 6Bone - current testbed
• Dual stacks
• Tunnelling
• Address Translation
• Lots of software changes!
• Will take years, but may be taking off now

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Final Thoughts

• What?s taking so long?
• NAT, CIDR, killer applications
• Might help return end-to-end principles
• Difficult to upgrade all hosts
• Other benefits and problems?