Internet Protocol version 6 (IPv6)

IPv6 was developed by Internet Engineering Task Force (IETF) to deal with the problem of IPv4 exhaustion. IPv6 is a 128-bits address having an address space of 2¹²⁸, which is way bigger than IPv4. IPv6 use Hexa-Decimal format separated by colon (:) .

Components in Address format :   

1. There are 8 groups and each group represents 2 Bytes (16-bits). 
2. Each Hex-Digit is of 4 bits (1 nibble)
3. Delimiter used – colon (:)

Need for IPv6:

The Main reason of IPv6 was the address depletion as the need for electronic devices rose quickly when Internet Of Things (IOT) came into picture after the 1980s & other reasons are related to the slowness of the process due to some unnecessary processing, the need for new options, support for multimedia, and the desperate need for security. IPv6 protocol responds to the above issues using the following main changes in the protocol:

1. Large address space

An IPv6 address is 128 bits long .compared with the 32 bit address of IPv4, this is a huge(2 raised 96 times) increases in the address space.

2. Better header format

IPv6 uses a new  header format in which options are separated from the base header and inserted, when needed, between the base header and the upper layer data . This simplifies and speeds up the routing process because most of the options do not need to be checked by routers.

3. New options

IPv6 has new options to allow for additional functionalities.

4. Allowance for extension

IPv6 is designed to allow the extension of the protocol if required by new technologies or applications.

5. Support for resource allocation

In IPv6,the type of service field has been removed, but two new fields , traffic class and flow label have been added to enables the source to request special handling of the packet . this mechanism can be used to support traffic such as real-time audio and video.

6. Support for more security

The encryption and authentication options in IPv6 provide confidentiality and integrity of the packet.

In IPv6 representation, we have three addressing methods : 

• Unicast
• Multicast
• Anycast

Addressing methods

1. Unicast Address 
Unicast Address identifies a single network interface. A packet sent to a unicast address is delivered to the interface identified by that address. 

2. Multicast Address 
Multicast Address is used by multiple hosts, called as groups, acquires a multicast destination address. These hosts need not be geographically together. If any packet is sent to this multicast address, it will be distributed to all interfaces corresponding to that multicast address. And every node is configured in the same way. In simple words, one data packet is sent to multiple destinations simultaneously.

3. Anycast Address 
Anycast Address is assigned to a group of interfaces. Any packet sent to an anycast address will be delivered to only one member interface (mostly nearest host possible). 

Note: Broadcast is not defined in IPv6. 

Types of IPv6 address:
We have 128 bits in IPv6 address but by looking at the first few bits we can identify what type of address it is. 

Prefix	Allocation	Fraction of Address Space
0000 0000	Reserved	1/256
0000 0001	Unassigned (UA)	1/256
0000 001	Reserved for NSAP	1/128
0000 01	UA	1/64
0000 1	UA	1/32
0001	UA	1/16
001	Global Unicast	1/8
010	UA	1/8
011	UA	1/8
100	UA	1/8
101	UA	1/8
110	UA	1/8
1110	UA	1/16
1111 0	UA	1/32
1111 10	UA	1/64
1111 110	UA	1/128
1111 1110 0	UA	1/512
1111 1110 10	Link-Local Unicast Addresses	1/1024
1111 1110 11	Site-Local Unicast Addresses	1/1024
1111 1111	Multicast Address	1/256

Note: In IPv6, all 0’s and all 1’s can be assigned to any host, there is not any restriction like IPv4. 

Provider-based Unicast address :
These are used for global communication. 

The First 3 bits identify it as of this type. 
Registry Id (5-bits): Registry Id identifies the region to which it belongs. Out of 32 (i.e. 2^5), only 4 registry IDs are being used. 

Provider Id: Depending on the number of service providers that operate under a region, certain bits will be allocated to the Provider Id field. This field need not be fixed. Let’s say if Provider Id = 10 bits then Subscriber Id will be 56 – 10 = 46 bits. 
Subscriber Id: After Provider Id is fixed, the remaining part can be used by ISP as a normal IP address. 
Intra Subscriber: This part can be modified as per the need of the organization that is using the service. 

Geography based Unicast address :

Global routing prefix: Global routing prefix contains all the details of Latitude and Longitude. As of now, it is not being used. In Geography-based Unicast address routing will be based on location. 
Interface Id: In IPv6, instead of using Host Id, we use the term Interface Id. 

Some special addresses:
Unspecified

Loopback

IPv4 Compatible 

IPv4 mapped

Local Unicast Addresses : 
These are of two types: Link-local and Site-Local

1. Link-local address:

A link-local address is used for addressing a single link. It can also be used to communicate with nodes on the same link. The link-local address always begins with 1111111010 (i.e. FE80). The router will not forward any packet with Link-local address. 

2. Site local address:

Site local addresses are equivalent to a private IP address in IPv4. Likely, some address space is reserved, which can only be routed within an organization. The first 10-bits are set to 1111111011, which is why Site local addresses always begin with FEC0. The following 32 bits are Subnet IDs, which can be used to create a subnet within the organization. The node address is used to uniquely identify the link; therefore, we use a 48-bits MAC address here. 

Advantages of IPv6 :

1. Realtime Data Transmission : Realtime data transmission refers to the process of transmitting data in a very fast manner or immediately. Example : Live streaming services such as cricket matches, or other tournament that are streamed on web exactly as soon as it happens with a maximum delay of 5-6 seconds.  

2. IPv6 supports authentication: Verifying that the data received by the receiver from the sender is exactly what the sender sent and came through the sender only not from any third party. Example : Matching the hash value of both the messages for verification is also done by IPv6.

3. IPv6 performs Encryption: Ipv6  can encrypt the message at network layer even if the protocols of application layer at user level didn’t encrypt the message which is a major advantage as it takes care of encryption.

4. Faster processing at Router: Routers are able to process data packets of Ipv6 much faster due to smaller Base header of fixed size – 40 bytes which helps in decreasing processing time resulting in more efficient packet transmission. Whereas in Ipv4, we have to calculate the length of header which lies between 20-60 bytes.

References :

• https://tools.ietf.org/html/rfc3513
• https://en.wikipedia.org/wiki/IPv6_address

Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.