This article describes DNS, ARP, RARP, and MAC protocols in sequence.
DNS protocol
DescriptionDomain Name Server (Domain Name resolution system), simply put, this protocol is mainly responsible for converting Domain names into IP addresses that can be identified by the network, such as converting www.cce.com.cn to 221.122.32.15, domain names and IP addresses correspond one to one. The reason is that when you access a website, it is eventually converted to an IP address for access. If you directly set a DNS server, the network access speed can be improved and the access correctness can be ensured.
Application: To use the DNS protocol in Windows, you only need to set the corresponding DNS server address. The specific method is the same as setting the IP address. For example, in Windows XP, first open the "local connection" attribute window and double-click "Internet Protocol (TCP/IP)" on the "General" tab) "; then, in the Open Properties window, select" Use the following IP Address "to set the IP address, subnet mask, and default gateway, and select" Use the following DNS server address "(), enter the corresponding DNS server address in the preferred DNS server and the backup DNS server. Then, click OK.
ARP Protocol
Description: Address Resolution Protocol (Address Resolution Protocol). In short, ARP is mainly responsible for converting 32 IP addresses in the LAN into 48-bit physical addresses, that is, the MAC Address of the NIC, for example, if the IP address is 192.168.0.1, the MAC address of the NIC is 00-03-f-fd-1d-2b. During the entire conversion process, a host sends a broadcast packet containing IP address information to the target host, that is, an ARP request, and then the target host sends a packet containing IP address and MAC address to the host, you can transmit data between two hosts through the MAC address.
Application: A dedicated ARP cache exists on the computer where the Ethernet network adapter is installed. It contains one or more tables for storing IP addresses and resolved MAC addresses. You can use ARP commands to view or modify arp cache information in Windows, for example, you can enter "arp-a" or "arp-g" in the Windows XP Command Prompt window to view the content in the ARP cache; type "arp-d IPaddress" to delete the specified IP address ). For other arp commands, enter "arp /?" View.
RARP Protocol
Description: Reverse Address Resolution Protocol (Reverse Address Resolution Protocol). As the name suggests, it is to convert the physical Address of a host in the LAN to an IP Address, for example, if a host in the LAN only knows the physical address but does not know the IP address, then the RARP server can send a broadcast request requesting the IP address.
Application: RARP is widely used to obtain the IP address of a diskless workstation.
MAC protocol
DescriptionMedia Access Control (Media Access Control Sub-layer), which is located in the lower half of the data link layer in OSI Layer 7 protocol. It is mainly responsible for controlling and connecting physical Media at the physical layer. When sending data, the MAC protocol can determine whether data can be sent in advance. If data can be sent, it adds some control information to the data, and finally sends the data and control information to the physical layer in the specified format; when receiving data, the MAC protocol first checks the input information and determines whether a transmission error has occurred. If there is no error, the control information is removed and sent to the LLC layer.
Application: MAC protocols are widely used in traditional wired LAN or popular Wireless LAN. In traditional LAN, the physical layers of various transmission media correspond to the corresponding MAC layer. Currently, the commonly used network adopts the MAC layer standard of IEEE 802.3 and the CSMA/CD access control mode; in a wireless LAN, the MAC standard is IEEE 802.11. The working mode is DCF (Distributed Control) and PCF (central control ).
