Data Communication and Networks

Topic : IPv6 Addresses

IPv6 Addresses

An Internet Protocol version 6 address (IPv6 address) is a numerical label that is used to identify a network interface of a computer or other network node participating in an IPv6 computer network.

Structure An IPv6 address consists of 16 bytes (octets); it is 128 bits long

Hexadecimal Colon NotationMore readable128 bit is divided into 8 sections ,each bytes in length2 bytes in hexadecimal notation requires 4 hexadecimal digitsAddress consists of 32 hexadecimal digitsEvery 4 digits separated by a colon

IPv6 address in binary and hexadecimal colon notation

Abbreviation

•Hexadecimal format is very long.•Many of the digits are zeros.•Leading zeros of a section can be omitted.•Only leading zeros can be dropped ,not the trailing zeros.

Abbrevation of IPv6 addresses

IPv6 has a much larger address space .The designers of IPv6 divided the address into several categories.A few leftmost bits, called the type prefix in each address define its category

Address Space

Type prefixes for IPv6 addresses

Type prefixes for IPv6 addresses(continued)

Types of IPv6 address -Unicast Addresses -Multicast Addresses -Anycast Addresses

Unicast Addresses

A unicast address defines a single computer.The packet sent to a unicast address must be

delivered to that specific computer.IPv6 defines two types of unicast address: Geo-graphically based Provider-based

Unicast address

The provider-based address is generally used by a normal host as a unicast address.

Prefixes for provider-based unicast address

Fields for the provider based are as follows:

Type identifier:- 3 bit field Address as the provider based addressRegistry identifier:- 5 bit field 3 registry centers : INTERNIC ,RIPNIC ,APNICProvider identifier:- 16 bit field Identifies provider for internet access

(Continued….)Subscriber identifier:- 24 bit field when organization subscribes to the internet through a provider ,it is assigned.Subnet identifier:- 32 bit field Defines a specific subnetwork under the territory of the subscriber.Node identifier:- 48 bit field Defines the identity of the node connected to a subnet

Multicast AddressesUsed to define a group of hosts instead of just one.

Multicast address

MULTICAST ADDRESS IN IPV6

A packet sent to a multicast address must be delivered to each member of the group.Second field is a flag that defines the group address , either permanent or transient.A permenent group address is defined by the Internet authorities and can be accessed at all times.A transient group address, on the other hand is used only temporarily.

Anycast AddressesAddress is delivered to only one of the members of the anycast group,the nearest one .One possible use is to assign an anycast address to all routers of an ISP that covers a large logical area in the internet.The router outside the ISP deliver a packet destined for the ISP to the nearest ISP router.No block is assigned for anycast addresses.

Anycast address

Reserved Addresses • It start with eight 0s (type prefix is 0000 0000).

Reserved addresses in IPv6

An Unspecified address is used when a host does not know its own address and sends an inquiry to finds its address. A Loopback address is used by a host to test itself without going into network.A Compatible address is used during the transition from IPv4 to IPv6.A Mapped address is also used during the transition.

Local Addresses

It is used when an organization wants to use IPv6 protocol without being connected to the global Internet. They provide addressing for private network.

Local addresses in IPv6

A link local address is used in an isolated subnet.A site local address is used in an isolated site with several subnet.

FEATURES

•Larger Address Space •No Broadcast •Anycast Support•Mobility •Extensibility

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