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Objectives
• Explain the need for IPv6 address space.
• Explain how IPv6 deals with the limitations of IPv4.
• Describe the features of IPv6 addressing.
• Describe the structure of IPv6 headers in terms of format and extension
headers.
• Show how an IPv6 address is represented.
• Describe the three address types used in IPv6.
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Internet Organization
IANA Internet Assigned
Numbers Authority
ARIN APNIC LACNIC AFRINIC RIPE
American Registry for Internet Numbers
Asia Pacific Network Information Centre
Latin America and Caribbean Network Information Centre
African Network Information Centre
Réseaux Internet Protocol Européens
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Why Do We Need a Larger Address Space?
• Internet population
– Approximately 973 million users in November 2005
– Emerging population and geopolitical and address space
• Mobile users
– PDA, pen-tablet, notepad, and so on
– Approximately 20 million in 2004
• Mobile phones
– Already 1 billion mobile phones delivered by the industry
• Transportation
– 1 billion automobiles forecast for 2008
– Internet access in planes – Example: Lufthansa
• Consumer devices
– Sony mandated that all its products be IPv6-enabled by 2005
– Billions of home and industrial appliances
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IPv6 Advanced Features
Larger address space
• Global reachability and flexibility
• Aggregation
• Autoconfiguration
• Plug-and-play
• End to end without NAT
• Renumbering
Simpler header
• Routing efficiency
• Performance and forwarding rate
scalability
• No broadcasts
• No checksums
• Extension headers
• Flow labels
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IPv6 Advanced Features (Cont.)
Mobility and security
• Mobile IP RFC-compliant
• IPSec mandatory
(or native) for IPv6
Transition richness
• Dual stack
• 6to4 tunnels
• Translation
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IPv4
• 32 bits or 4 bytes long
• 4,200,000,000 possible addressable nodes
IPv6
• 128 bits or 16 bytes: four times the bits of IPv4
• 3.4 * 1038 possible addressable nodes
• 340,282,366,920,938,463,374,607,432,768,211,456
• 5 * 1028 addresses per person
Larger Address Space
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Larger Address Space Enables Address Aggregation
• Aggregation of prefixes announced in the global routing table
• Efficient and scalable routing
• Improved bandwidth and functionality for user traffic
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Self Check
1. How much of the address space was in use by mid-2001?
2. How many bits are included in an IPv6 address?
3. How will IPv6 enable smaller routing tables in Internet
routers?
4. Why is NAT not a requirement for IPv6?
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Simple and Efficient Header
A simpler and more efficient header means:
• 64-bit aligned fields and fewer fields
• Hardware-based, efficient processing
• Improved routing efficiency and performance
• Faster forwarding rate with better scalability
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MTU Issues
• Minimum link MTU for IPv6 is 1280 octets
(vs. 68 octets for IPv4).
– On links with MTU < 1280, link-specific fragmentation and reassembly must
be used
• Implementations are expected to perform path MTU discovery to send packets
bigger than 1280.
• Minimal implementation can omit PMTU discovery as long as all packets kept ≤
1280 octets.
• A hop-by-hop option supports transmission of “jumbograms” with up to 232
octets of payload.
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IPv4 and IPv6 Header Comparison
Fragment
Offset
Flags
Total Length
Type of
Service
IHL
PaddingOptions
Destination Address
Source Address
Header ChecksumProtocolTime to Live
Identification
Version
IPv4 Header
Next
Header
Hop Limit
Flow Label
Traffic
Class
Destination Address
Source Address
Payload Length
Version
IPv6 Header
Field’s Name Kept from IPv4 to IPv6
Fields Not Kept in IPv6
Name and Position Changed in IPv6
New Field in IPv6
Legend
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IPv6 Extension Headers
Simpler and more efficient header means:
• IPv6 has extension headers.
• IPv6 handles the options more efficiently.
• IPv6 enables faster forwarding rate and end nodes processing.
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1 Basic IPv6 Header -
2 Hop-by-Hop Options 0
3 Destination Options (with Routing Options) 60
4 Routing Header 43
5 Fragment Header 44
6 Authentication Header 51
7 Encapsulation Security Payload Header 50
8 Destination Options 60
9 Mobility Header 135
UL TCP 6
UL UDP 17
U L ICMPv6 58
IPv6 Extension Headers
Any combination of 64-bits Extension Headers may follow the IPV6 header but
according to the following order:
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IPv6 Address Representation
• x:x:x:x:x:x:x:x, where x is a 16-bit hexadecimal field
• Leading zeros in a field are optional:
– 2031:0:130F:0:0:9C0:876A:130B
• Successive fields of 0 can be represented as ::, but only once per address.
Examples:
2031:0000:130F:0000:0000:09C0:876A:130B
2031:0:130f::9c0:876a:130b
FF01:0:0:0:0:0:0:1 >>> FF01::1
0:0:0:0:0:0:0:1 >>> ::1
0:0:0:0:0:0:0:0 >>> ::
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IPv6—Addressing Model
• Addresses are assigned to interfaces
– Change from IPv4 mode:
• Interface “expected” to have multiple addresses
• Addresses have scope
– Link Local
– Unique Local
– Global
• Addresses have lifetime
– Valid and preferred lifetime
Link LocalUnique LocalGlobal
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IPv6 Address Types
• Unicast
– Address is for a single interface.
– IPv6 has several types (for example, global and IPv4 mapped).
• Multicast
– One-to-many
– Enables more efficient use of the network
– Uses a larger address range
• Anycast
– One-to-nearest (allocated from unicast address space).
– Multiple devices share the same address.
– All anycast nodes should provide uniform service.
– Source devices send packets to anycast address.
– Routers decide on closest device to reach that destination.
– Suitable for load balancing and content delivery services.
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IPv6 Global Unicast (and Anycast)
Addresses
The global unicast and the anycast share the same address format.
• Uses a global routing prefix—a structure that enables aggregation upward,
eventually to the ISP.
• A single interface may be assigned multiple addresses of any type
(unicast, anycast, multicast).
• Every IPv6-enabled interface must contain at least one loopback (::1/128)
and one link-local address.
• Optionally, every interface can have multiple unique local and global
addresses.
• Anycast address is a global unicast address assigned to a set of interfaces
(typically on different nodes).
• IPv6 anycast is used for a network multihomed to several ISPs that have
multiple connections to each other.
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NAT-PT#sho ipv6 interface fa0/0
FastEthernet0/0 is up, line protocol is up
IPv6 is enabled, link-local address is FE80::20D:BDFF:FE75:3D01
No Virtual link-local address(es):
Global unicast address(es):
2001:A:B::1, subnet is 2001:A:B::/64
Joined group address(es):
FF02::1
FF02::2
FF02::1:FF00:1
FF02::1:FF75:3D01
MTU is 1500 bytes
ICMP error messages limited to one every 100 milliseconds
ICMP redirects are enabled
ICMP unreachables are sent
ND DAD is enabled, number of DAD attempts:
IPv6 Addresses assigned (example)
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IPv6 Global Unicast Addresses (RFC 3587)
• Global unicast and anycast addresses are defined by a global routing prefix, a
subnet ID, and an interface ID.
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IPv6 Global Unicast Addresses Range (example)
• Global unicast and anycast addresses are defined by a global routing prefix, a subnet ID, and
an interface ID.
• Global Routing prefix = /53
• Subnet ID (Routing Prefix) = /64
• Interface ID = /64
• 64M of clients using only an Address (2001) from the Global Unicast Address Space
• Addresses from 2000/3 (0010) – E000/3 (1110), with the exception of the FF00::/8, are
available to form Global Unicast (EUI-64) Addresses.
• Thirteen blocks of 4096 (16^3) addresses each = 53.248 blocks of 67M of clients each=
3.567.616.000.000 of clients (3.5 trillions).
• IANA is currently allocating addresses in the range of 2001::/16 to the registries.
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2001:rrr ../19 2^3=8 Registries
2001:rrriiiiiiii .. /27 2^8=256 ISPs
2001:rrriiiiiiiiccccc:cccccc .. /53 2^26=67M Clients
2001:rrriiiiiiiiccccc:cccccc ..:ssssssss..:: /64 2^11=2048 Subnetworks
2001:xxxx:xxxx:xxxx:HHHH:HHHH:HHHH::/128 2^64=18446 Trill. hosts
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IPv6 Unicast Addressing
• IPv6 addressing rules are covered by multiple RFCs.
– Architecture defined by RFC 4291.
• Unicast: One to one
– Global
– Link local (FE80::/10)
• A single interface may be assigned multiple IPv6 addresses of any type: unicast,
anycast, or multicast.
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Self Check
1. Describe the MTU discovery process used by IPv6 devices.
2. Why is the IP checksum header not used in IPv6 implementations?
3. How are successive zeros represented in an IPv6 address?
4. What are 3 types of IPv6 addresses?
5. Which address type from IPv4 was eliminated in IPv6?
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Summary
• IPv6 is a powerful enhancement to IPv4. Features that offer functional
improvement include a larger address space, simplified header, and mobility
and security.
• IPv6 increases the number of address bits by a factor of four, from 32 to 128.
• The IPv6 header has 40 octets and is simpler and more efficient than the IPv4
header.
• IPv6 addresses use 16-bit hexadecimal number fields separated by colons (:) to
represent the 128-bit addressing format.
• The three types of IPv6 addresses are unicast, multicast, and anycast.
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