What is Server Network Load Balancing
Load balancing is a server set composed of multiple servers in a symmetrical manner. Each server has an equivalent status and can provide services independently without the assistance of other servers. Through a certain load sharing technology, the requests sent from the outside are evenly distributed to a server in the symmetric structure, and the server that receives the request responds to the client's request independently. Load balancing can evenly distribute client requests to the server array, thereby providing quick access to important data and solving the problem of a large number of concurrent access services. This clustering technique can achieve near mainframe performance with minimal investment.
Advantages of Network Load Balancing
First, network load balancing can spread incoming requests to up to 32 servers, that is, up to 32 servers can be used to share outbound network request services. Network load balancing technology ensures that the server can respond quickly even under heavy load;
Second, network load balancing only needs to provide an IP address (or domain name) to the outside world;
Third, when one or several servers in the network load balancing are unavailable, the service will not be interrupted. When Network Load Balancing automatically detects that a server is unavailable, it can quickly reassign client traffic among the remaining servers. This protection measure can help you provide uninterrupted services for critical business programs, and can increase the number of network load balancing servers according to the increase in network traffic;
Fourth, network load balancing can be implemented on ordinary computers.
The realization process of network load balancing
In Windows Server 2003, network load balancing applications include Internet Information Services (IIS), ISA Server 2000 firewall and proxy server, VPN virtual private network, terminal server, Windows Media Services (Windows video on demand, video broadcasting) and other services. At the same time, network load balancing helps improve server performance and scalability to meet the growing demands of Internet-based clients.
Network Load Balancing allows clients to access the cluster with a logical Internet name and virtual IP address (also known as the cluster IP address), while preserving each computer's individual name. Below, we will introduce the implementation and application of network load balancing on two ordinary computers with Windows Server 2003 installed.
Among the two computers, one is named A and has an IP address of 192.168.0.7; the other is named B and has an IP address of 192.168.0.8. The network load balancing dedicated virtual IP address is planned to be 192.168.0.9. When officially applied, the client only needs to use the IP address 192.168.0.9 to access the server, and the network service balancer will automatically select 192.168.0.7 or 192.168.0.8 to provide external services according to the load of each server. The specific implementation process is as follows:
On each computer that implements network load balancing, only TCP/IP protocol can be installed, do not install any other protocol (such as IPX protocol or NetBEUI protocol), which can be viewed from "Network Connection Properties".
The first step is to log in to computer A and computer B respectively as an administrator, open the "Local Area Connection" property interface of the two computers, check the "Load Balance" item in "This connection uses the following items" and enter the "Properties" dialog. box, set the IP addresses to 192.168.0.9 (that is, the dedicated IP for load balancing), and set the subnet mask to 255.255.255.0;
The second step, enter the "Internet Protocol (TCP/IP)" property setting interface of machine A and machine B respectively, click the "Advanced" button, and add the IP address 192.168.0.9 in the pop-up "Advanced TCP/IP Setting" interface And the subnet mask is set to 255.255.255.0.
The third step is to exit the "Local Area Connection Properties" window of the two computers, and wait patiently for a while for the system to complete the settings.
Later, if the two servers cannot meet the requirements, you can add the third and fourth computers to the network load balancing system according to the above steps to meet the requirements.
Verify Network Load Balancing with IIS Service
After the network load balancing is configured, in order to implement a specific service, the corresponding service needs to be installed on the network load balancing computer. For example, in order to achieve load balancing of an IIS website, it is necessary to install the IIS service on the corresponding network load balancing server. In order for each user to access consistent data when accessing different computers through network load balancing, data consistency needs to be maintained on each computer in network load balancing. For example, to implement network load balancing of IIS on two nodes, in order to ensure the consistency of the content of the two websites, except that the configurations of the two IIS servers are the same, the corresponding website data must be consistent.
为了检验网络负载均衡，我们可以通过IIS来进行验证，其他的一些应用如终端服务、Windows Media服务与IIS的应用与之相类似。在其他计算机上的IE浏览器中键入192.168.0.9，根据网络的负载，网络负载均衡会自动转发到A机或B机。为了验证效果，你可以在浏览的时候，拔掉第一台计算机的网线或拔掉第二台机器的网线，将会发现浏览到的将是不同内容。当然，我们在测试的时候，为了验证网络负载均衡的效果，把两个网站设置成不一致的内容，而在正式应用的时候，网络负载均衡群集的每个节点计算机的内容将是一致的，这样不管使用哪一个节点响应，都能保证访问的内容是一致的。
负载均衡在校园网中的应用
校园网的应用除了用于教学、科研、管理、图书情报资料检索外，还承担任着校内外信息交流、电子邮件、公告、新闻发布，以及各种公共网络口的访问等任务。由于在网络上传输的信息不只是数字、文字和图形，还会随应用水平的提高，逐步增加语音、活动图像及视频图像等高带宽的应用。因此，网络的建设，尤其是主干网要求高带宽与高速度，在校园网的服务器中应用负载均衡技术不失为一种廉价的解决方案。