New World,New beginning

终于在美国安顿下来，时差也调整好了，明天就要开始新学期了。又要做学生了，呵呵！

这次看一个网络的基本问题，网络划分问题。有关于VLSM，CIDR。以前一直是固有的A、B、C类的地址，技术在进步，老的方法不行了，新的就出现了。

Classless Inter-Domain Routing (CIDR, pronounced "cider") was introduced in 1993 and is the latest refinement to the way IP addresses are interpreted. It replaced the previous generation of IP address syntax, classful networks. Specifically, rather than allocating address blocks on eight-bit (i.e., octet) boundaries forcing 8, 16, or 24-bit prefixes, it used the technique of variable-length subnet masking (VLSM) to allow allocation on arbitrary-length prefixes. CIDR encompasses:

The VLSM technique of specifying arbitrary length prefix boundaries. A CIDR-compliant address is written with a suffix indicating the number of bits in the prefix length, such as 192.168.0.0/16. This permits more efficient use of increasingly scarce IPv4 addresses.
The aggregation of multiple contiguous prefixes into supernets, and, wherever possible in the Internet, advertising aggregates, thus reducing the number of entries in the global routing table. Aggregation hides multiple levels of subnetting from the Internet routing table, and reverses the process of "subnetting a subnet" with VLSM.
The administrative process of address blocks to organizations based on their actual and short-term projected need, rather than the very large or very small blocks required by classful addressing schemes.

来自wikipedia，自己也还没有很好的消化。要继续看了，以前的基础还是太差了。

目前的理解：在基本网路划分的基础上，提出了VLSM，而为了解决网络汇聚问题，提出了CIDR。至于其间的关系，我在继续看。