IPv6

Internet Protocol Version 6

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Internet Protocol Version 6 (IPv6)

• IPv6 solutions to IPv4 disadvantages• IPv6 addressing• IPv6 header• DNS support for IPv6• Core protocols of IPv6• IPv6 Neighbor Discovery• Differences between IPv4 and IPv6

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Disadvantages of IPv4

• Limited address space• Flat routing infrastructure• Configuration• Security• Quality of service (QoS)• Mobility

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IPv6 Solutions to IPv4 Disadvantages

• Huge address space• Hierarchical routing infrastructure• Automatic configuration• Built-in security• Better support for QoS• Built-in mobility

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Larger Address Space

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IPv4• 32 bits or 4 bytes long

4,200,000,000 possible addressable nodesIPv6• 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

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IPv6 Adressing

TrillionTrillionBillion 525.62128

) 523( 523 100

52TrillionthousandnQuadrillio

Billion

TrillionTrillion

6.5 Billion people on earth

Typical braincell has ~100 Billion cells(your count may vary)

IPv6 addresses for every human brain cell on the planet

IPv6 addresses per person

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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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The IPv6 Address Space• 128-bit address space• 128 bits were chosen to allow multiple levels of

hierarchy and flexibility in designing hierarchical addressing and routing

• Global unicast and anycast addresses are defined by a global routing prefix, a subnet ID, and an interface ID

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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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Compressing Zeros• Some IPv6 addresses contain long sequences of zeros• A single contiguous sequence of 16-bit blocks set to 0 can

be compressed to “::” (double-colon) • Examples:

– FE80:0:0:0:2AA:FF:FE5F:47D1 becomes FE80::2AA:FF:FE5F:47D1

– FEC0:0:0:41CD:2AA:FF:FE5F:47D1 becomes FEC0::41CD:2AA:FF:FE5F:47D1

– FF02:0:0:0:0:0:0:1 (a multicast address) becomes FF02::1

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IPv6 Prefixes• Prefix is the part of the address where the bits

have fixed values or are the bits of a route or subnet identifier

• IPv6 subnets or routes always uses address/prefix-length notation– CIDR notation

• Examples:– 3FFE:FFFF:2A:41CD::/64 is a subnet

identifier– 3FFE:FFFF:2A::/48 is a route– FF::/8 is an address range

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Types of IPv6 Addresses

• Unicast– Address of a single interface– One-to-one delivery to single interface

• Multicast– Address of a set of interfaces– One-to-many delivery to all interfaces in the

set• Anycast

– Address of a set of interfaces– One-to-one-of-many delivery to a single

interface in the set that is closest• No more broadcast addresses

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Unicast IPv6 Addresses• Global addresses

– Used on IPv6 Internet– Equivalent to IPv4 public

addresses• Local-Use Addresses

– Site-local addresses• Equivalent to IPv4

private addresses• Always begin with

FEC0– Link-local addresses

• Equivalent to APIPA addresses

• Always begin with FE80

Link LocalSite LocalGlobal

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IPv6 Interface Identifiers

• Based on:– Derived from the MAC address of the network

adapter to which the address is assigned– Randomly generated to provide IPv4-

equivalent anonymity– Assigned during a Point-to-Point Protocol

(PPP) connection– Assigned during DHCP configuration

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IPv6 Interface identifier EUI-64• Cisco uses the extended

universal identifier (EUI)-64 format to do stateless autoconfiguration.

• This format expands the 48-bit MAC address to 64 bits by inserting “FFFE” into the middle 16 bits.

• To make sure that the chosen address is from a unique Ethernet MAC address, the universal/local (U/L bit) is set to 1 for global scope (0 for local scope).

00 90 27 17 FC 0F

00 90 27 17 FC 0F

FF FE

00 90 27 17 FC 0FFF FE

02 90 27 17 FC 0FFF FE

48 bit

64 bit

000000U01 = Unique0 = Not UniqueU =

Mac address

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IPv6 Header

Fragment OffsetFlags

Total LengthType of ServiceIHL

PaddingOptions

Destination Address

Source Address

Header ChecksumProtocolTime to Live

Identification

Version

IPv4 Header

Next Header Hop Limit

Flow LabelTraffic 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 IPv6Leg

end

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IPv6 Extension Header types

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

Ethernetheader

IPv6header

Routingheader

Fragheader

Authheader

ESPheader

TCPheader

Applicationdata

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DNS Support for IPv6

• AAAA resource records for name-to-address resolutions

• PRT resource records in the IP6.ARPA reverse domain for address-to-name resolutions

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Core Protocols of IPv6• IPv6

– Replacement for IPv4• ICMPv6

– Replacement for ICMP for IPv4• Neighbor Discovery

– Replacement for ARP, Redirect, and Router Discovery for IPv4

• Multicast Listener Discovery– Replacement for IGMPv2 for IPv4

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IPv6 Neighbor Discovery• Messages

– Neighbor Solicitation– Neighbor Advertisement– Router Solicitation– Router Advertisement– Redirect

• Processes– Address resolution– Duplicate address detection– Router discovery– Redirect– Neighbor unreachability detection

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Stateless Autoconfiguration

• A router sends network information to all the nodes on the local link.

• A host can autoconfigure itself by appending its IPv6 interface identifier (64-bit format) to the local link prefix (64 bits).

• The result is a full 128-bit address that is usable and guaranteed to be globally unique.

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A Standard Stateless Autoconfiguration

• Stage 1: The PC sends a router solicitation to request a prefix for stateless autoconfiguration.

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• Stage 2: The router replies with a router advertisement.

A Standard Stateless Autoconfiguration (Cont.)

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Differences Between IPv4 and IPv6 Feature IPv4 IPv6Address length 32 bits 128 bits

Header size 20-60 bytes 40 bytes

IPSec support Optional Required

QoS support Some Better

Fragmentation Hosts and routers Hosts only

Checksum in header Yes No

Options in header Yes No

Link-layer address resolution ARP (broadcast) Multicast Neighbor Discovery Messages

Multicast membership IGMP Multicast Listener Discovery (MLD)

Router Discovery Optional Required

Uses broadcasts? Yes No

Configuration Manual, DHCP Automatic, DHCP

DNS name queries Uses A records Uses AAAA records

DNS reverse queries Uses IN-ADDR.ARPA Uses IP6.ARPA