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IPv6 Address

Despite all short-time solutions, such as Classless IP addressing, Dynamic Host Configuration Protocol (DHCP), even Network Address Translation (NAT); addresses were still depleting which was a long-term problem for the Internet. 

There were other problems occurred such as, lack of accommodation for real-time audio and video transmission, encryption and authenticity of the data.

This set of predicaments motivated computer scientists to originate another version of IP Address, which is what we call IP version 6 (IPv6) addresses.

Structure of IPv6 Address

An IPv6 address consists of 16 byte, means it is 128 bits long.

To make addresses more understandable, IPv6 specifies a hexadecimal colon notation. In this type of notation the 128 bits are divided into eight sections, each 2 bytes in length. 

Now, 2 bytes in hexadecimal notation requires 4 hexadecimal digits. Therefore IPv6 addresses were structured like this:

128 bits = 16 bytes = 32 hex digits
Say, an example
1111110111101100      ................     1111111111111111
  Simplified to
        FDEC : 0074 : 0000 : 0000 : 0000 : B0FF : 0000 : FFFF

Abbreviations in IPv6 addresses

Even though the IP addresses are in hexadecimal format, is still very long and many of the digits are zeros. In this case, the scientists abbreviated the address. The leading zeros of a section (four digits between two colons) can be reduced. However, only the leading zeros can be dropped, not the trailing zeros.

Further abbreviations are possible if there consecutive sections consisting of zeros only. In that case, we can remove the zeros altogether and replace them with a double semicolon. Note that, this kind of abbreviation is allowed only once per address.

FDEC : 0074 : 0000 : 0000 : 0000 : B0FF : 0000 : FFFF
Abbreviated to
FDEC : 74 : 0 : 0 : 0 : B0FF : 0 : FFFF
Even more abbreviated to
FDEC : 74 : : BOFF : 0 : FFFF

Mind, there is a gap between two colons after 74 and before BOFF.

By using this form of abbreviations, 0074 can be written as 74, 000F can be written as F and 0000 as 0.

Note: 4120 can not be abbreviated.

Address Space

IPv6 has much larger address space, which is 2128 bits long

Features of using IPv6  

Unicast Addressing

A unicast Addresses A unicast address defines a single computer basically. The packets sent to unicast address must be delivered to that specified computer. IPv6 specifies two types of unicast address, such as:

  1. Geographically-based address.
  2. Provider-based address.

Multicast Addressing 

Multicast addresses are used to define a host instead of just one. When packets are sent to a multicast address, then it must be delivered to each member of the group.

Anycast Addressing 

IPv6 also specifies a feature that defines anycast addresses. An anycast addresses are like muticast addresses, it also defines a group individual nodes. 
However, when packets are destined for an anycast address then its is delivered to only one of the members of the anycast group, to the nearest one (which has the shortest route).

Note: Although the definition of an anycast address is still debatable.

Reserved Addressing 

Another category of IPv6 addresses are reserved addresses. These addresses start with eight 0s (type of prefix is 0000 0000).

It has subcategory named Loopback Address, which is used by a host to test itself without going into the network.

Local Addressing 

These type of addresses are used by an organization when it want to use IPv6 addresses without being connected to the global internet

In other words, they mainly provide the addresses for private networks. No one outside the organization can send a message to any node using these addresses.


1. What is number of bits used in IPv6 addresses?

2. Why IPv6 addresses were developed? explain with reason.

3. How IPv6 addresses are different from IPv4 addresses.

4. State the features of using IPv6 Addressing

5. What is Loopback Address?

ipv6 address size, ipv6 header format
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