CSCI 465 Data Communications and Networks Lecture 25

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CSCI 465Data Communications and
NetworksLecture 25

• Martin van Bommel

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IP Versions

• IP v 1-3 defined and replaced
• IP v4 - current version
• IP v5 - streams protocol
• IP v6 - replacement for IP v4
• during development it was called IPng
• (IP Next Generation)

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Why Change IP Versions?

• Address space exhaustion
• 2 level addressing (network and host) wastes
  space
• IP network addresses used even if not connected
• Growth of networks and the Internet
• extended use of TCP/IP e.g. TV, point-of-sale
• single address per host not flexible
• Requirements for new types of service
• address configuration
• Routing flexibility - traffic support

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IPv6 Enhancements

• expanded 128 bit address space
• improved option mechanism
• most not examined by intermediate routes
• dynamic address assignment
• increased addressing flexibility
• unicast, anycast, and multicast
• support for resource allocation
• labeled packet flows

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IPv6PDU(Packet) Structure
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IPv6 Header
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IP v6 Flow Label

• related sequence of packets - special handling
• identified by source and destination address
  flow label
• flow number generated randomly
• make sure not to reuse within lifetime of old
  flow
• router treats packets of flow the same
• treatment pre-negotiated with router(s)

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IPv6 Addresses

• 128 bits long
• Assigned to interface
• Same interface may have multiple addresses
• Types of addresses
• Unicast single interface address
• Anycast one of a set of interface addresses
• Multicast all of a set of interface addresses

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Hop-by-Hop Options

• must be examined by every router
• if unknown discard/forward handling is specified
• next header type of header that follows
• header extension length length of this header
• Options
• Jumbo payload
• IPv6 packet is longer than 65,535 octets
• Router alert
• Tells router(s) that packet contains router
  control data

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Fragmentation Header

• fragmentation only allowed at source
• no fragmentation at intermediate routers
• node must perform path discovery to find smallest
  MTU (maximum transmission unit) of intermediate
  networks
• set source fragments to match MTU
• otherwise limit to 1280 octets
• minimum MTU must be supported by networks

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Routing Header

• contains a list of one or more intermediate nodes
  to be visited on the way to a packets
  destination
• Includes
• Next header identification, Header length,
  Routing type
• Segments left number of route segments left
• Type 0 routing IPv6 header has address of
  router
• Routing header contains list of router addresses
• Next destination address first on list
• Final destination address last on list
• Each router on path moves address to IPv6 header
  and shortens list

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IPv6 Extension Headers