ipv6寻址

1)分类寻址 (1) Classful Addressing)

IPv4 addressing used the concept of classes. This architecture is known as classful addressing.

IPv4寻址使用类的概念。 这种体系结构称为类寻址 。

In the classful addressing, there are 5 classes in which the address space is divided: A, B, C, D, and E.

在有类寻址中，地址空间分为5个类： A，B，C，D和E。

Each class occupies some fraction of the address space.

每个类占用一部分地址空间。

We can find the class of an address when given the address in binary notation or dotted-decimal notation by checking the first few bits or first byte.

通过检查前几位或第一个字节，以二进制或点分十进制形式给定地址时，可以找到地址的类别。

类和块 (Classes and Blocks)

There is a problem with the classful addressing that is "each class is divided into a fixed number of blocks with each block having a fixed size".

分类寻址存在一个问题，即“每个类被划分为固定数量的块，每个块具有固定的大小” 。

Class name	Number of blocks	Block size	Application
A	128	16,777,216	Unicast
B	16,384	65,536	Unicast
C	2,097,152	256	Unicast
D	1	268,435,456	Multicast
E	1	268,435.456	Multicast

班级名称	块数	块大小	应用
一个	128	16,777,216	单播
乙	16,384	65,536	单播
C	2,097,152	256	单播
d	1个	268,435,456	多播
Ë	1个	268,435.456	多播

The "class A addresses" are designed for large organizations to manage a large number of attached hosts or routers.

“ A类地址”是为大型组织设计的，用于管理大量连接的主机或路由器。

The "class B addresses" are designed for midsize organizations to manage tens of thousands of attached hosts or routers.

“ B类地址”是为中型组织设计的，用于管理成千上万个连接的主机或路由器。

The "class C addresses" are designed for small organizations to manage a small number of attached hosts or routers.

“ C类地址”是为小型组织设计的，用于管理少量连接的主机或路由器。

2)无类寻址 (2) Classless Addressing)

Classful addressing leads to address depletion. That's the big issue for this schema and that's why it's not used nowadays.

分类寻址会导致地址耗尽。 这是此架构的主要问题，这就是为什么现在不使用它。

To overcome the problem of address depletion and to give more organizations access to the Internet, the classless addressing was designed and implemented. In this scheme of classless addressing, there are no classes, but the addresses are still granted in blocks.

为了克服地址耗尽的问题，并使更多组织可以访问Internet，设计并实现了无类寻址。 在这种无类别寻址方案中，没有任何类别，但是地址仍以块形式授予。

地址块 (Address Blocks)

In classless addressing, when an entity(organization or a single household (small organization) or whatever which uses the internet) needs to be connected to the Internet, it is granted a block (range) of addresses. The size of the block (the number of addresses) varies based on the nature, size, and need of the entity.

在无类寻址中，当一个实体(组织或单个家庭(小型组织)或使用互联网的任何对象)需要连接到Internet时，将被授予一个地址块(范围)。 块的大小(地址数)根据实体的性质，大小和需要而变化。

For example, a household (small organization) may be given only two addresses; a large organization may be given thousands of addresses. On the other hand. An ISP, as the Internet service provider, may be given hundreds of thousands based on the number of customers it may serve.

例如，一个家庭(小型组织)可能仅获得两个地址。 大型组织可能会获得数千个地址。 另一方面。 作为互联网服务提供商，ISP可能会根据其服务的客户数量而获得数十万的奖励。

Three restrictions on classless address blocks:

无类地址块的三个限制：

1. The addresses in a block must be contiguous that means one after another.

   块中的地址必须连续，这意味着一个接一个。

2. The number of classless addresses in a block must be a power of 2.

   块中无类地址的数量必须是2的幂。

3. The first address must be evenly divisible by the number of addresses.

   第一个地址必须能被地址数平均整除。

References:

参考文献：

• Book: Data communication & networking

  图书：数据通信与网络

• Classless addressing

  无类寻址

翻译自: https://www.includehelp.com/computer-networks/classful-and-classless-addressing-ipv4-addressing.aspx

ipv6寻址