What is load balancing?

The size of the internet increases by one times every 100 days, and customers want to get 7 days and 24 hours of uninterrupted availability and faster system response times, rather than repeatedly seeing a site "Server
Too Busy "and frequent system failures.

With the increase of traffic volume and the rapid growth of traffic volume and data flow, the processing capacity and calculation intensity of the network are increased, which makes the single equipment unable to bear. In this case, if you throw
Remove existing equipment to do a lot of hardware upgrades, which will cause the waste of existing resources, and if faced with the next increase in business, this will lead to another hardware upgrade of the high cost of investment, or even performance
Excellent equipment also does not meet the current volume of business needs. Therefore, the load balancing mechanism arises.

Load-balancing (load Balance) is built on the existing network architecture, providing a cheap, efficient and transparent way to extend the bandwidth of network devices and servers, increase throughput, and enhance network data
Ability to handle, improve network flexibility and usability.

Load balancing has two meanings: first, a large number of concurrent access or data traffic sharing to multiple node devices to deal with, reduce the user waiting for response time;
Point device to do parallel processing, after each node device processing, the results are summarized, returned to the user, system processing capacity has been greatly improved.

The main application of load balancing technology

1, DNS load balancing the earliest load balancing technology is implemented through DNS, in DNS for multiple addresses to configure the same name, so the client query this name will get one of the addresses, from
and make different customers access different servers, to achieve load balancing purposes. DNS load balancing is a simple and efficient approach, but it does not differentiate between server differences and the server's current
Run state.

2, proxy server load balancing using a proxy server, you can forward the request to the internal server, using this acceleration mode can obviously improve the access speed of static Web pages. However, it is also possible to consider such a
Technology, using a proxy server to forward the request evenly to multiple servers, so as to achieve load balancing purposes.

3. Address translation Gateway load Balancing supports a load-balanced address translation gateway that maps an external IP address to multiple internal IP addresses and dynamically uses one of the internal locations for each TCP connection request
Address to achieve load balancing purposes.

4, the agreement to support the internal load balance in addition to these three load balancing methods, some of the protocols internally support load balancing related functions, such as the HTTP protocol in the redirection capability, HTTP running in
The highest level of TCP connections.

5. Nat Load Balancing NAT (Network address translation) simply translates an IP address into another IP location.
Address, typically used for conversion between unregistered internal addresses and legitimate, registered Internet IP addresses. Apply to resolve Internet IP address tension, do not want to leave the network outside
department to know the internal network structure and so on occasions.

6, reverse proxy load Balancing normal proxy mode is the proxy internal network users access to the Internet Server connection request, the client must specify a proxy server, and will be sent directly to the
The connection request for the server on the Internet is sent to the proxy server for processing. A reverse proxy (Reverse proxy) means that a proxy server is used to accept a connection on the Internet
The request is then forwarded to the server on the internal network and the results obtained from the server are returned to the client requesting the connection on the Internet, at which point the proxy server behaves as a service
The service device. The reverse proxy load balancing technique is to dynamically transfer the connection requests from the Internet to multiple servers on the internal network in a reverse proxy way to achieve load balancing
Objective.

7. Hybrid load balancing in some large networks, due to the differences in hardware devices, sizes and services provided by multiple server groups, we can consider using the most appropriate load balancer for each server group
, and then again load-balanced or clustered across multiple server clusters to provide services to the outside world (that is, to treat these multiple server groups as a new server farm) for optimal performance. I
We call this approach a hybrid load-balancing. This approach is sometimes used in situations where the performance of a single equalization device cannot satisfy a large number of connection requests.