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CT320: IPv6

Thanks to:

• Dr. Indrajit Ray, CSU
• Dr. James Walden, NKU
• Russ Wakefield, CSU

for the contents of these slides.

Motivation

IPv6

• Initial motivation: 32-bit address space soon to be completely allocated.
• Additional motivation:
  • header format helps speed processing/forwarding
  • header changes to facilitate QoS
  • IPv6 datagram format:
  • fixed-length 40 byte header
  • no fragmentation allowed

IPv6 Header

• Traffic class: identify priority among datagrams in flow
  • Abuse? You bet!
• Flow Label: identify datagrams in same “flow” (ill-defined concept).
• Next header: identify upper layer protocol for data

Other Changes from IPv4

• Checksum: removed entirely to reduce processing time at each hop
• Options: allowed, but outside of header, indicated by “Next Header” field
• ICMPv6: new version of ICMP
  • additional message types, e.g. “Packet Too Big”
  • multicast group management functions

Transition From IPv4 To IPv6

• Not all routers can be upgraded simultaneously
  • no “flag days”
  • How will the network operate with mixed IPv4 and IPv6 routers?
• Tunneling: IPv6 carried as payload in IPv4 datagram among IPv4 routers

Tunneling

Send a packet from IPV6, in the future:

┌───┐   ┌───┐                                   ┌───┐   ┌───┐
│ A │···│ B │···································│ E │···│ F │
└───┘   └───┘           IPv6 Internet           └───┘   └───┘
IPv6    IPv6                                    IPv6    IPv6

In these primitive times:

┌───┐   ┌───┐   ┌───┐                   ┌───┐   ┌───┐   ┌───┐
│ A │···│ B │···│ C │···················│ D │···│ E │···│ F │
└───┘   └───┘   └───┘   IPv4 Internet   └───┘   └───┘   └───┘
IPv6    IPv6    IPv4                    IPv4    IPv6    IPv6

C & D are IPv4/IPv6 gateways, which wrap/unwrap the IPv6 packet in an IPv4 packet, much as a TCP packet is wrapped in an IP packet.