IPv6

Question 1

IPv6 - general characteristics

Answer 1

• replacement for IPv4
• extended use of TCP/IP (new applications => requests for new IP addresses)
• requirements for new types of services due to new applications with different requirements
• extended address space: 128 bits
• dynamic assignment of addresses
• improved option mechanism
• increased addressing flexibility

Question 2

IPv6 - header format

Answer 2

• contains less info than IPv4 header
• next header field - first extension header; identifies type of header immediate following
• flow label field - associate datagrams belonging to a flow or communication between two applications
• traffic class - classes/priorities of current packet; still under development
• payload length - includes all extension headers plus user data
• source address & destination address (128 bits)

Question 3

IPv6 addresses

Answer 3

• 128 bits long
• assigned to node’s interface (one single interface may have multiple unique unicast addresses)
• three types of addresses:
  1. unicast - packet delivered to a single interface - one to one (global, link local, site local) + an address destined for a single interface
  2. anycast - set of interfaces (typically belonging to different nodes); delivered to any one interface, usual the “nearest” - one to nearest
  3. multicast - packets delivered to all interfaces identified - one to many + replaces IPv4 “broadcast”

Question 4

IPv6 - Optional Headers

Answer 4

• carry optional info, not necessary examined by all routers or hosts
• Hop-by-Hop Options Header consists of the following:
  1. Next Header
  2. Header extension length
  3. Options - one or more option definitions (options definition contains the following sub-fields: option type, length, option data)
  4. Fragmentation Header - fragmentation only allowed at source node which must find the smallest MTU (Maximum Transmission Unit) of intermediate networks - composed of next header, reserved, frag. offset, reserved, more flag, identification
  5. Routing Header - list of one or more intermediate nodes to be visited - composed of next header, header extension length, routing type, segments left
  6. Destination Options Header