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IPv6 “Under the Hood”

Join Rick Summerhill, Executive Director of the Great Plains Network, and Dale Finkelson from the University of Nebraska at Lincoln for a comprehensive tutorial and workshop on the inner workings of IPv6. Learn about the basic headers, extension headers, and header types, as well as the changes and improvements from IPv4 to IPv6. Gain a deep understanding of IPv6's addressing capabilities, header format simplification, and enhanced support for extensions and options.

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IPv6 “Under the Hood”

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  1. IPv6 “Under the Hood”

  2. IPv6 Tutorial/Workshop Rick Summerhill Executive Director, Great Plains Network Dale Finkelson University of Nebraska at Lincoln

  3. Basic Headers • IPv6 Header • IPv4 Header

  4. Basic Headers • Fields • Version (4 bits) – only field to keep same position and name • Class (8 bits) – new field • Flow Label (20 bits) – new field • Payload Length (16 bits) – length of data, slightly different from total length • Next Header (8 bits) – type of the next header, new idea • Hop Limit (8 bits) – was time-to-live, renamed • Source address (128 bits) • Destination address (128 bits)

  5. Basic Headers • Simplifications • Fixed length of all fields, not like old options field – IHL, or header length irrelevant • Remove Header Checksum – rely on checksums at other layers • No hop-by-hop fragmentation – fragment offset irrelevant – MTU discovery • Add extension headers – next header type (sort of a protocol type, or replacement for options) • Basic Principle: Routers along the way should do minimal processing

  6. Extension Headers • Extension Header Types • Routing Header • Fragmentation Header • Hop-by-Hop Options Header • Destinations Options Header • Authentication Header • Encrypted Security Payload Header

  7. Extension Headers • Routing Header

  8. Extension Headers • General Routing Header

  9. Extension Headers • Fragmentation Header • “I thought we don’t fragment?” • Can do at the sending host • Insert fragment headers

  10. Extension Headers • Options Headers in General • The usual next header and length • Any options that might be defined

  11. Extension Headers • Destinations Options Header • Act – The Action to take if unknown option • 00 – Skip Over • 01 – Discard, no ICMP report • 10 – Discard, send ICMP report even if multicast • 11 – Discard, send ICMP report only if unicast • C – Can change in route • Number is the option number itself

  12. Extension Headers • Hop-by-Hop Extension Header • The usual format of an options header • An example is the jumbo packet • Payload length encoded • Can’t be less than 65,535 • Can’t be used with fragmentation header

  13. Extension Headers • Extension Header Order • Hop-by-Hop options Header • Destination options Header (1) • Routing Header • Fragment Header • Authentication Header • Destination Options Header (2) • Upper Layer Header, e.g. TCP, UDP • How do we know whether or not we have an upper layer header, or an extension header? • Both are combined into header types

  14. Header Types • Look in packet for next header • Can be Extension Header • Can be something like ICMP, TCP, UDP, or other normal types

  15. Header Types

  16. Header Types

  17. Header Types

  18. ICMP • Completely Changed – note new header type • Now includes IGMP • Types organized as follows • 1 – 4 Error messages • 128 – 129 Ping • 130 – 132 Group membership • 133 – 137 Neighbor discovery • General Format

  19. ICMP

  20. ICMP • Error Messages (Types 1 – 4) – Some Examples • Destination Unreachable • Code 0 – No route to destination • Code 1 – Can’t get to destination for adminstrative reasons • Code 2 – Address unreachable • Code 3 – Port Unreachable • Packet Too Big • Code 0, Parameter is set to MTU of next hop • Allows for MTU determination • General Format

  21. ICMP • Ping • Similar to IPv4 • Echo Request, set code to 0 • Echo Reply sent back • General Format

  22. Multicast • Multicast (and Anycast) built in from the Beginning • Scope more well-defined – 4 bit integer • Doesn’t influence well-defined groups

  23. Multicast • A Few Well-Defined Groups • Note all begin with ff, the multicast addresses • Much of IGMP is from IPv4, but is in ICMP now

  24. Changes from IPv4 to IPv6 • Expanded addressing capabilities • Header format simplification • Improved support for extensions and options • Flow labelling capability • Authentication and privacy capabilities

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