It will be described below separately for the three closely related to the HTTP protocol (IP, TCP, DNS) the TCP / IP protocol suite.
Responsible for IP transport protocol
By sub-level, IP (Internet Protocol) Internet protocol at the network layer. Internet Protocol The name may sound a bit exaggerated installed, but the fact is the case, because almost all use of the network system will be used IP protocol. TCP / IP protocol suite IP refers to the network protocol, the protocol name occupies half position, and its importance.
IP is actually the name of a protocol.
An IP protocol is to transmit various data packets to each other. And to ensure that there is indeed sent to the other party, you will need to meet all kinds of conditions. Wherein two important condition is the IP address and MAC address.
Indicates the IP address is assigned to the node address, MAC address refers to a fixed address belongs to the network card. IP address and MAC address pair. IP address conversion, but does not substantially change the MAC address.
Using the ARP protocol to communicate with the MAC address
Communication between the MAC address-dependent IP. On the network, the communication of both sides in the same local area network is very small, usually after multiple computers and network devices to connect to each other transit. During the transfer, the MAC address will use the next relay device to search for a next relay destination. At this time, we will use ARP protocol. ARP is a protocol used to address resolution protocol, can be isolated anti MAC address corresponding to the IP address of the access side.
No one can fully control the transport situation in the Internet
In the transfer process reaches the communication target sign, those computers and routers and other networking equipment can only be learned very rough transport routes.
This mechanism is called routing, a bit like a courier company's delivery process. People want to send express, as long as their goods to the distribution center, the courier company will know whether the pit recipient sender, address for service of the courier company distribution center for cargo inspections, a clear area of the next station which sent the Distribution center. Then, the distribution center that will determine whether the region can be sent from the other side of the home. Through this parable illustrates, no matter which computer, which network devices, they can not fully grasp the details of the Internet.
To ensure the reliability of the TCP protocol
Divided by level, TCP located on the transport layer, provides reliable byte stream service.
The so-called service is a byte stream, in order to facilitate transfer large blocks of data divided into units of segments in a message packet management.
Reliable transport service means that data can pass each other accurately and reliably. In a nutshell TCP protocol make it easier to transfer large data only then split data, and TCP protocol can confirm whether or not the final data delivery to the other party.
Ensure that data can reach the target
In order to reach the target accurately at the data, TCP protocol uses a three-way handshake strategy. After using the TCP protocol packets sent out, TCP will not ignore the case of the transfer, it will be delivered to the other party to confirm successful. Handshake used during the CP flags (flag) --- SYN (synchronize) and ACK (acknowledgement).
Data sender first sends a packet with SYN flag of the other party. After the receiver receives, with a return SYN / ACK packet flag to indicate convey acknowledgment information. Finally, the transmitting end band pass a return packet ACK flag representative of a "handshake" end.
If some stage inexplicably interrupted during the handshake, TCP protocol will once again send the same data packets in the same order.
In addition to the above-mentioned three-way handshake, TCP protocol as well as a variety of other means to ensure the reliability of communication.
Responsible for domain name resolution DNS service
DNS (Domain Name System) service and the HTTP protocol is the same as the application layer protocol. It provides service between the domain name to resolve IP addresses.
The computer can either be assigned an IP address, it can also be given to the host name and domain name.
Users typically use a host name or domain name to access each other's computer, rather than direct access by IP address. As compared with a set of numeric IP addresses, with the representation of the letters with numbers to specify the computer name more in line with human memory habits.
But if you want the computer to understand the name, it becomes relatively difficult. Because computers are better at handling long string of numbers.
To solve these problems, DNS service came into being. DNS protocol provides domain name lookup by IP address, or reverse domain name from IP address reverse lookup service.
