IPv6 TutorialWorkshop

1
IPv6 Tutorial/Workshop

• Rick Summerhill
• Executive Director, Great Plains Network
• Dale Finkelson
• University of Nebraska at Lincoln

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Contents

• Brief History
• Addressing
• Basic Headers
• Extension Headers
• Header Types
• ICMP
• Multicast
• Auto Configuration
• Neighbor Discovery

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Brief History

• Motivations
• Depletion of addresses - after careful study,
  depleted in 2005 2015
• Routing table expansion - Is this a problem?
• Early in Process
• IAB June, 1992 meeting in Kobe, JA - Use CLNP
  (from OSI) as basis for new IP
• Process came under question
• Withdrawn July, 1992
• Reorganize - IPng area - Scott Bradner and
  Allison Mankin

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Brief History

• Choices At time of Kobe meeting, three choices
• CLNP
• OSI, installed base, routing rotocols, etc.
• Became TUBA (TCP and UDP over bigger addresses,
  20 Octet)
• CATNIP
• IPv7, to become TP/IX, new routing protocol RAP
• Became CATNIP. Common packet format IP, CLNS,
  IPX.
• SIPP
• IP in IP, two layers became IPAE (IP address
  encapulation).
• Became transition strategy, Simple IP.
• 64 bit addresses.
• Merged with Pip, having a routing strategy.
  Became Simple IP Plus.

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Brief History

• Review in June of 1994
• Recommendation in July
• Use SIPP with modifications
• 128 bit addresses
• Called version 6 (version 5 in use as
  experimental stream protocol
• Extensive work, published in January of 1996
• Extensive set of RFCs
• Check Check http//www.rfc-editor.org/rfcsearch.ht
  ml
• Search on IPv6 much of what appears below comes
  from these.

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Addressing

• Notation
• Bits, 128 8 fields, colon delimited, each of 16
  bits in hex
• Example
• 3FFE370000210000000011fffeab1234
• Simplified Notation
• Leading zeros not necessary - above address
  becomes
• 3FFE3700210011fffeab1234
• Sequences of 0s replaced with - one time, at
  front, back, or middle
• 3FFE37002111fffeab1234
• Masks written with number of bits in network part
  of address after "/
• address - 3FFE37002111fffeab1234/48
• network - 3FFE370021/48 (meaning
  3FFE37000021/48)

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Addressing

• Notation
• IPv4 extension
• 10.0.0.1, or A001, or
• 0000000000000000000000000A000001
• Current Assignments
• Tables

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Addressing
9
Addressing
10
Addressing

• Aggregatable Unicast Addressing
• EUI addresses versus MAC addresses
• Insert fffe into middle, as bytes 4 and 5.
• abcd12345678 -gt abcd12fffe345678
• User bit
• 000712345678 -gt 020712fffe345678

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Addressing

• Specific addresses (interfaces) many addresses
  assumed
• Unspecified ()
• Used by host until configured
• Loopback (1)
• For hosts to send packets to themselves
• IPv4 (for example, 10.0.0.1)
• To use IPv4 addresses
• Site Local (prepend FEC0/10 plus subnet)
• Never route across the internet
• Link Local (prepend FE80/10 plus zeros)
• Never route away from interface

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Addressing

• Autoconfiguration
• Router gives prefix to host - takes EUI address
  on lower 64 bits
• Potential for multiple routers to give prefix
  multihoming
• Host can also hard configure address - e.g. web
  server, changing nic cards
• Multicast addresses
• Layout flags, scope, group id
• Flags - Transient or not
• Scope - fixed table
• Assigned groups - later, if there is time

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Basic Headers

• IPv6 Header

• IPv4 Header

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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)

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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

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Extension Headers

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

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Extension Headers

• Routing Header

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Extension Headers

• General Routing Header

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Extension Headers

• Fragmentation Header
• I thought we dont fragment?
• Can do at the sending host
• Insert fragment headers

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Extension Headers

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

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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

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Extension Headers

• Hop-by-Hop Extension Header
• The usual format of an options header
• An example is the jumbo packet
• Payload length encoded
• Cant be less than 65,535
• Cant be used with fragmentation header

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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

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Header Types

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

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Header Types
26
Header Types
27
Header Types
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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

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ICMP
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ICMP

• Error Messages (Types 1 4) Some Examples
• Destination Unreachable
• Code 0 No route to destination
• Code 1 Cant 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

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ICMP

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

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Multicast

• Multicast (and Anycast) built in from the
  Beginning
• Scope more well-defined 4 bit integer
• Doesnt influence well-defined groups

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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

34
Auto Configuration

• Basic Principle Hosts which dont know
  addresses use multicast to communicate
  destinations, and link local sources
• Lets turn on a host
• Assigns itself a link local address
• Uses prefix FE80000
• Uses EUI-64 address
• Configures interface to receive addresses
  FF021, the all hosts group
• Sends ICMP Solicitation Message (type 133) to
  FF022, the all routers group the link layer
  address is embedded in the message
• A router, if it exists, sends back an ICMP Router
  Advertisement message (type 134)

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Auto Configuration

• Turning on the host, continued
• Host adds to its address pool for that interface
  the prefix and the EUI-64 address
• Continues to use link-local address
• If no router responds, simply uses the link-local
  address
• Statefull configurations can be done
• Configurations can be hardwired
• Might want to do this for servers, where changing
  out a NIC card might be painful
• There is a version of DHCP that can be used
• The next consideration is ARP which is now
  combined with auto configuration into neighbor
  discovery

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Neighbor Discovery

• Old ARP too simplistic broadcast, get back
  address
• Too dependent on media
• Not really a basic part of the protocol
• Neighbor Discovery is the new procedure, and it
  fits very nicely with auto configuration
• As always, packets sent only to local network
  hosts
• Hosts keep 4 cached lists
• Destination Cache IPv6 address / Neighbor to
  forward to
• Neighbors Cache IPv6 address / Media address
  (all local)
• Prefix Cache Recently learned prefixes from
  routers
• Router Cache IPv6 addresses of routers
  (link-local)

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Neighbor Discovery

• Basic Rules for sending packets
• For IPv6 address, find media address of local
  neighbor and send to that media address
• If in destinations cache, we know the next hop
• If not, then check prefix cache for a match to
  see if local
• If not local, then send to a router in router
  cache
• At this point, have IPv6 address of neighbor and
  now we must determine the media address of the
  next hop
• If in neighbor cache completely, use that media
  address
• If incomplete, wait for completion
• If not in neighbor cache at all, send ICMP Host
  Solicitation Message (type 135) to Solicited Node
  Multicast Address (later) and add to neighbor
  cache
• If neighbor cache entry is old, refresh it

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Neighbor Discovery

• What is Solicited Node Multicast Address?
• Use prefix FF0200001FF000/104
• Use last 24 bits of IPv6 address
• All hosts need to compute this at startup
• Host must respond with ICMP Host Advertisement
  Message (type 136)