Big Talk web surfing

We assume that there is no strategy for packet transfer between different hosts, and we are thinking from the beginning how to accomplish this.

  Thinking steps:  1. Let's start with a simple one, assuming we have 4 computers, and we connect them together, we are temporarily called intranet or LAN. In order to point to the point we need to make a unique logo for each computer, so we got a call card, the production of the time to give him a unique indicator, in a LAN we through the network interconnection is easy to get all the machine's physical network card, through this unique indicator we can send data, The data is sent in the most brutal way broadcast to all hosts, the data contains its own physical address and the target physical address, the receiver response time according to their own network card number matching mode to make a single response.  2. The data transmission between our 4 computers has been solved, and then, we want to connect other LAN computers, and then access 4 units is OK, can access 8 units, 10,1000,10000 it? In the form of a broadcast it is dead, because you have a computer that frequently accepts useless data. And so many computers each time the data transfer to know the other person's physical number is to be dead. In order to solve this problem, we can do this, all the local area network is reserved, and then specify a machine in the local area network as the gateway to the local area network, which is responsible for interacting with other local area network information. Then the door of different LAN is re-formed a local area network.  3. In order to quickly determine this hierarchical relationship we invented an abstract concept IP and then classified it, we say 3 classes for the time being.  a Class 1-126.0-255.0-255.1-244b class 128-191.0-255.0-255.1-254c class 192-233.0-255.0-255.1-254  each computer has an IP, So what are the characteristics of a computer in the same network segment or a computer IP in the same LAN? We divide an IP into two parts, part is the network address, part is the host address, is located in the same network address on the same LAN, then this network address and host address how to get it? For the A,b,c class they are different, in order to get the network address and host address quickly we have defined a "subnet mask" concept, the subnet mask of Class 3 IP is:  a class 255.0.0.0B Class 255.255.0.0 c class 255.255.255.0  It is obvious that we only need to use the subnet mask and the IP phase operation, and the result if the two IPs are uniformly stated in a network segment.  4. The same network segment does not need to go through the gateway, different network segments need to go through the gateway, the gateway is also in a local area network, if the gateway with the target IP or not a network segment inside, and then go up a layer of Gateway, loop so.

Big talk web surfing