Address space in IPV6

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IP Addressing

Each TCP / IP host is identified by a logical IP address. This address is unique for each host that communicates via TCP / IP. Each 32-bit IP address identifies a location of a host on the network the same way a street address identifies a house in a city. In the same way as a street address has a standard format in two parts "a street name and house number", each IP address is separated into two parts: a network ID and host ID: The ID Network, also known as network address identifies a network segment in a single interconnection network TCP / IP bigger. All systems associated with the same network and sharing access to this network have a common network ID within their full IP address ID is also used to uniquely identify each network in the network interconnection greatest. The host ID, also called host address identifies a node TCP / IP (a workstation, server, router or other device TCP / IP) in each network. The host ID for each device identifies one system in its own network.

Here is an example of 32-bit IP address: 10,000,100 01,101,011 00,010,000 11,001,001. To facilitate IP addressing, addresses are expressed in dotted decimal notation. The IP address of 32 bits is segmented into four 8-bit bytes. The bytes are converted to decimal (base 10 numbering system) and are separated by dots. That is why, in the previous example, the IP address is 132.107.16.201 when converted to dotted decimal notation.

The following illustration shows an example for an IP address (132.107.16.201) as it is divided into sections of network and host ID. Part of Network ID (132 107) is indicated by the first two numbers of the IP address. The party host ID (16201) is indicated by the last two numbers of the IP address.


IP Address Classes

The Internet community has defined five classes of addresses. Addresses Class A, B and C are used for assignment to the nodes TCP / IP.

The class of address defines which bits are used for the network and the host ID portions of each address. The address class also defines the number of networks and hosts that can be supported by network. The following table uses wxyz to indicate the four byte values of a given IP address. This table is used to present the following:

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The Subnet Mask

In any case, the netmask is used to identify the portion of the IP address corresponding to the network and the part corresponding to the host. Indeed, the address of the network is calculated simply by a logical AND between IP address and netmask. For this, we must translate the address decimal to binary, then do the logical according to the following table:

0 and 0 = 0
0 and 1 = 0
1 and 0 = 0
1 and 1 = 1

The default mask for a Class A address is 255.0.0.0, so if one makes the logical AND: Translate decimal network address = 12.0.0.0. In fact, the network mask, the bits set to 1 are associated with the network number, while those set to 0 correspond to the party guests. This is important since this is how we will find the number of machines belonging to a network. Example with a class C address: 200.13.13.26 mask: 255.255.255.0. If we put the mask in binary 11111111.11111111.11111111.00000000 & we see that the host part is coded on 8 bits, so February 8 to 2 = 254 machines max. The netmask can therefore find the network address and the maximum number of machines on a given network. This might seem unnecessary since we know that a network with a Class A address, for example going to be up to 16 million machines and we know also quickly find its network address (first byte code identifier network ).

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The IPv6 address space

The first characteristic is the use of IPv6 address much larger. The size of an address in IPv6 is 128 bits, which is four times larger than IPv4 address. A 32-bit address space allows 4,294,967,296 possible addresses. A 128-bit address space allows 340 282 266 920 938 463 463 374 607 431 768 211 465 (or 3.4 x 10 ^38) possible addresses.

Syntax of IPv6 addresses

IPv4 addresses are represented in dotted decimal format. The 32-bit address is divided into four times 8 bits. Each group of 8 bits is converted to its decimal equivalent and separated by dots. For IPv6, the 128-bit address is divided into 16-bit boundaries, and each block of 16 bits is converted into a 4-digit hexadecimal number and separated by a colon. The resulting representation is described as hexadecimal colon.


The following is an IPv6 address in binary: 128 bits is divided into 16-bit boundaries


0010000111011010 1001000011010011 0000000001010000

0010111100111011 0000001010101010 0000000011111111

1111111000101000 1001110001011010


Each block of 16 bits is converted to hexadecimal and separated by a colon. The result is the following 21DA: 00D3: 0000: 2F3B: 02AA: 00FF: FE28: 9C5A. IPv6 representation can be further simplified by removing the leading zeros in each block of 16 bits. However, each block must have at least one individual figure. With leading zero suppression, the address representation becomes: 21DA: D3: 0:2 F3B: 2AA: FF: FE28: 9C5A

Compressing Zeros

Some types of addresses contain long sequences of zeros. To simplify the representation of IPv6, a contiguous sequence of 0 in blocks of 16 bits are zeroed in hexadecimal "two point" to be compressed "::".

For example:

The link local address FE80: 0:0:0:2 AA: FF: FE9A: 4CA2 can be compressed to FE80:: 2AA: FF: FE9A: 4CA2. The multicast address FF02: 0:0:0:0:0:0:2 can be compressed to FF02:: 2. Compression of zeros can only be used to compress a contiguous series of 16 bits. You can not use zero compression to include part of the block of 16 bits. For example, you can not express FF02: 30:0:0:0:0:0:5 as FF02: 3:: 5. In the address FF02:: 2, two blocks (the block "FF02" block and "2"). The number of 0 bits expressed by "::" is 128 bit - 32 bits = 96. Compression of zeros can only be used once in a given address. Otherwise, you could not determine the number of 0 bits represented by each address.