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nhưng nói chung, họ có xu hướng tối đa hiện tại khoảng 70 đến 80 Mbps (megabit mỗi giây) của thông. Giống như SLB, FWLB cho phép để thực hiện một số bức tường lửa chia sẻ tải trọng một cách tương tự như SLB. Bởi vì bản chất của giao thông, tuy nhiên, cấu hình và công nghệ là khác nhau. Hình 1-4 cho thấy một cấu hình FWLB chung. | Direct Server Return 27 Direct Server Return As introduced in Chapter 2 Direct Server Return DSR is a method of bypassing the load balancer on the outbound connection. This can increase the performance of the load balancer by significantly reducing the amount of traffic running through the device and its packet rewrite processes. DSR does this by skipping step 3 in the previous table. It tricks a real server into sending out a packet with the source address already rewritten to the address of the VIP in this case 192. 168.0.200 . DSR accomplishes this by manipulating packets on the Layer 2 level to perform SLB. This is done through a process known as MAC Address Translation MAT . To understand this process and how DSR works let s take a look at some of the characteristics of Layer 2 packets and their relation to SLB. MAC addresses are Layer 2 Ethernet hardware addresses assigned to every Ethernet network interface when they are manufactured. With the exception of redundancy scenarios MAC addresses are generally unique and do not change at all with a given device. On an Ethernet network MAC addresses guide IP packets to the correct physical device. They are just another layer of the abstraction of network workings. DSR uses a combination of MAT and special real-server configuration to perform SLB without going through the load balancer on the way out. A real server is configured with an IP address as it would normally be but it is also given the IP address of the VIP. Normally you cannot have two machines on a network with the same IP address because two MAC addresses can t bind the same IP address. To get around this instead of binding the VIP address to the network interface it is bound to the loopback interface. A loopback interface is a pseudointerface used for the internal communications of a server and is usually of no consequence to the configuration and utilization of a server. The loopback interface s universal IP address is 127.0.0.1. However in the same .
