IP Address - IPv6 Header

Hello everybody,

welcome to this new lesson about of networking topics, today we'll cover how IPv6 packet is composed. As perhaps the majority of readers will know the IPv6 has taken hold because the IPv4 addresses are over, so that the computer scientist have decided to create the IPv6 address, and this time the address space is very large because the IPv6 address has 128 bit. Well now explain some things... the IPv6 address use the hexadecimal values so represented in figure below:

This is a structure of IPv6 address where 'X' is switched with 2001:0DB8:AC10:FE01:0000:0000:0000:0000, now see that is a long address and is boring copy when setting a net-device we can use some simple rules:

1. Zero Omitting: we can remove all zeros in address then the 0DB8 become: DB8.
2. Omitting segment zeros: The segments zeros are represented of that pile of zeros 0000:0000:0000:0000 how we can delete it? It's simple! We can delete with the omitting segment zeros. 

So that when we write an IPv6 address, we represent in this form: 

2001:DB8:AC10:FE01::

But a warning, when you use the segment omitting, you can use only one time. Now we move on header of this packet. In this packet we can found
some modifications to the header, let's see.

  

IPv6 HEADER 

The IPv6 header has this structure:

Version (4 bit): This field is 4 binary value. In this field we can find the IPv6 version, infact this field is always set to 0110.

Traffic Class (8 bit): This field is 8 binary value. This field is used for the management priority of packet. The 6 most-significant bits are used for differentiated services, which is used to classify packets while the remaining two bits are used for ECN (Explicit Congestion Notification).

Flow Label (20 bit): This field is used by the sender to identify a sequence of packets as if they were in the same flow. Supports the management of QoS, but for now this field is still in an experimental stage.

Payload Lenght (16 bit): This field instead is used for understand the lenght of packet. Then it represents the number of bytes of everything that comes after the header.

Next Header (8 bit): This field is very similar to the protocol field of the IPv4 header, which uses the same values. Because this field is used for understand the type of header follows the basic IPv6 header.

Hop Limit (8 bit): This field deals of the TTL jumps. Let me explain better the limit of jumps allowed. This field is decremented to 1 each time that the packet passes by a router when it reaches zero is discarded (deleted).

Source Address (128 bit): This field is source address or sender of a letter.

Destination Address (128 bit): This field is destination address or receiver of a letter. 

Bye,

Tefnut.