l4 switch load balancing

1. OverviewThe first two times in this article, we have been talking about the construction of Nginx + keepalived. At the beginning of this article, we are going to honor the promise of the previous article, the following two articles we will introduce the Nginx + keepalived and LVS + keepalived to build a highly available load layer system. If you do not know about Nginx and LVS, see my previous two articles, "Architecture Design:

Load BalancerIt can be a dedicated device or an application that runs on a common server. Distribute requests to servers that have the same content or provide the same services. Special purpose devices are generally only Ethernet interfaces, which can be said to be a multi-layer switch. The load balancer is typically assigned a virtual IP address, and all request

bandwidth. 4 to 7 layers of load balancing are now frequently used. Layer fourth load balance maps a legally registered IP address on the Internet to the IP address of multiple internal servers and dynamically uses one of the internal IP addresses for each TCP connection request to achieve load

address translation gateway can evenly convert each connection to a different internal server address, then the computers in the external network will communicate with the server on the address they have obtained, this achieves load balancing. Address translation can be implemented through software or hardware. Hardware-based operations are generally called exchanges. When the exchange must save TCP connec

can set the full Internet name of the cluster and determine its operating mode. A little explanation is needed here: 3.6.1 Unicast modeRefers to the host nodes to point to the same virtual MAC address, in this case, communication between the nodes can not be implemented. 3.6.2 multicast modemeans that each host node retains the original MAC address, in addition to the special for NLB communication MAC address, so that the normal communication between the nodes. However, not all routers or swi

As developers of back-end applications, we often develop, debug, test and publish our applications to the production environment, and users have direct access to our applications. But for Internet applications, there is a low profile or thick or thin layer of load balancing software between your application and users, and they do not show the dew silently playing an important role, so much so that we often

here:3.6.1 Unicast modeRefers to the host node to the same virtual MAC address, in which case communication between the nodes is not possible.3.6.2 multicast modemeans that each host node retains its original MAC address, plus the communication MAC address that is dedicated to NLB, so that communication between nodes can be achieved normally. However, not all routers or switches support multicast mode and need to be handled with care.3.6.3 IGMP multicast modeBased on the multicast mode feature,

requirements. Requirements for switches and routers When you plan to use VLANs to prevent the exchange of data floods, you must ensure that the switch supports VLAN settings; When using multicast, some routers do not support the mapping of a unicast IP address to a multicast MAC address and need to be set manually. Requirements for communication protocols network adapters that are bound to the cluster can only install the TCP/IP protocol, and you

requirements. Requirements for switches and routers When you plan to use VLANs to prevent the exchange of data floods, you must ensure that the switch supports VLAN settings; When using multicast, some routers do not support the mapping of a unicast IP address to a multicast MAC address and need to be set manually. Requirements for communication protocols network adapters that are bound to the cluster can only install the TCP/IP protocol, and you mus

longer; Uneven distribution, if the configuration between several Web servers, can withstand the pressure is different, but the DNS resolution allocation of access is evenly distributed. Unbalanced distribution of user groups results in an imbalance in DNS resolution. Session hold, if it is a Web site that requires authentication, this is fatal if the software architecture is not modified, because DNS resolution cannot permanently assign authenticated users access to the same server. Al

immediately switch to the Remote data center. The "minimum time" can be computed in two ways, from the time the request is sent to the top of the server to the response header, and from the time the request is sent to the full request body, header_time respectively response_time . Session consistency The session consistency (session persistence) problem can be achieved by specifying the Ip-hash equalization algorithm, and there is a more general imp

As developers of back-end applications, we often develop, debug, test and publish our applications to the production environment, and users have direct access to our applications. But for Internet applications, there is a low profile or thick or thin layer of load balancing software between your application and users, and they do not show the dew silently playing an important role, so much so that we often