Theoretical technology: TCP/IP protocol family (four) ICMP and IGMP protocol!
The IP protocol should be mentioned first, and then considering the hierarchy, it is better to introduce the supporting protocol first and then discuss the IP in detail! Because IP is my favorite and my pain! Ha ha!
1. ICMP Protocol
Why use ICMP! What is the reason for using ICMP?
Let's briefly talk about what IP can't do! IP does not provide error control and auxiliary mechanisms (eg host management and query)!
To this end, ICMP has undertaken this task very well!
ICMP is the Internet Control Packet Protocol. Its function is: Error reporting and querying
ICMP The ICMP packets sent by ICMP cannot be directly delivered to the next layer, and the IP header must be added! ICMP
packets are divided into two categories: 1 is an error report packet, 2 is a query packet For: 1) loopback request and answer 2) timestamp 3) address mask 4) router query and advertisement Here to emphasize 1 point: ICMP is a protocol for error reporting, not responsible for error correction! Introduce several commands and troubleshooting tools under Windows! 1, the command ping, this can not be familiar with it! (The detailed introduction will be made to everyone in the PING attack!) 2. Command tracert, this may be a little strange to everyone, it is to track the path from the source point to the end point of the package, open CMD, and command tracert www.2cto. com Look at how many routers the Red and Black Alliance has gone on your computer! 3. The command pathping is a combination of ping and tracert! Nice stuff! 2. IGMP protocol Two terms: 1. Multicast: 1 party sends information to multiple parties and receives it! The 1-to-many data transmission form is multicast! 2. Multicast router: a router with the ability to forward multicast packets!
To be honest, I learned IGMP very well! But the role of IGMP is not that important (a necessary but insufficient protocol), but that IP must have IGMP!
1 sentence IGMP is not important but necessary! A bit contradictory! Ha ha!
The IGMP protocol is also known as the Internet Group Management Protocol! Help multicast routers create and update "honest" membership tables associated with each router interface!
Concept explanation: This kind of situation often occurs in network communication. One-to-many multicast communication mode! Video-on-demand way! What kind of multicast is the most commonly used in QQ? Everyone should be able to think of it! IGMP takes care of this! Then the multicast router is for the final analysis: in order to avoid broadcast communication, isolate the broadcast domain, and save bandwidth costs, multicast is adopted, and the multicast group will be stored in the multicast routing table in the form of a table, and IGMP helps to establish and maintain this table. , and the so-called "honest" members are stable in a group, receiving and sending data! Like the people in our QQ group, either join or quit! No 1 will go in and 1 will come out!
Now there are 3 versions of IGMP, and the package of version 2 has 3 types: 1) query 2) member report 3) exit report
The query is divided into general query and special query! A multicast router can mean any network device that supports the multicast protocol! All the switching equipment of Cisco Systems , Huawei's quidway series routing switches , and things from ZTE, if you need to implement the multicast function on the network, buy their things! Ask the guy who sells the equipment for specific things!
Use the command to find out the multicast address supported by the interface of the device: netstat /nra The multicast address range is between 224.0.0.0-239.255.255.255! The division of IP will be explained in detail later!
Note that IGMP only appears on the LAN! Its original package cannot pass through the router!
Reference: https://www.2cto.com/net/201201/117741.html