Server load Balancing Basic concepts

Server load Balancing Basic concepts

Server load Balancing: The literal understanding is that the network traffic load burden. According to different network levels can be divided into two-layer load, three-layer load, four-layer load, seven-layer load.

three-layer load: The three-layer load is best understood, so the three-layer load is first spoken. The three-tier load is shared based on the IP address. better understood for those who understand NAT technology. The general topology is as follows:

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load device ( slb) provides a Vip ip slb< Span style= "font-family: ' The song Body '; > The client traffic is dispatched to the server side. Similar to nat C1 first access Vip dispatch to server A nat do three-layer load.

four-layer load: in osi model four-layer only Tcp and Udp agreement. In layman's terms, it is more than the three-tier source ip "Purpose Ip multi-source port, destination port. such as slb provide 10.1.1.100:80 service, dispatch to S1 10.1.1.100:8080 service dispatch to S2 port hash algorithm or similar algorithm. There are also different services based on tcp, udp The difference between the protocols.

seven-layer load: More application-level protocols, commonly used http, radius< Span style= "font-family: ' The song Body '; >, dns can be based on Url:/abc/ Http://10.1.1.100/def/index.html dispatch to server s2 dns protocol, it can be scheduled according to the client request to query the different domain names. This enables more strategies to be realized by identifying application-layer data. such as http related policy modifications http Url Cookie session hold, http dispatch, etc., dns strategy User_name dispatch, etc.

two-layer load: Two-layer load is more special, SLB still provides a VIP(virtual IP), but the background server is the same IP, different MAC. as follows:

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clients access virtual services over an IP network, andSLB distributes them to different servers through a Mac. So the problem comes, the same server IP is not the IP conflict? Of course, these servers are very special, do not send ARP messages, also requires the SLB connection switch port also does not send ARP. As long as the SLB sends the message over, the switch is OK by forwarding it based on the Mac Address Table .

This article is from the "Ding classmate 1990" blog, please be sure to keep this source http://dingtongxue1990.blog.51cto.com/4959501/1816889

Server load Balancing Basic concepts