Huawei quidway s7700 Configuration Manual page 238

Quidway S7700 Smart Routing Switch
Configuration Guide - SPU
The server load balancing supported by the SPU has the following characteristics:
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Issue 01 (2011-07-15)
Figure 6-3 Typical networking of server load balancing in DMAC mode
Host
IP
Network
As shown in Figure 6-3, multiple servers provide services through the virtual IP address.
Switch A functions as the load balancing device and is responsible for allocating user
requests to multiple servers. Switch B functions as a common switch and is responsible for
forwarding user requests to the load balancing device or returning response packets of
servers to users. The process of server load balancing in DMAC mode is as follows:
1. Users send requests to Switch B.
2. Switch B forwards the received request packets to Switch A.
3. After receiving the response packets, Switch A classifies packets at Layer 3 or Layer
7 according to service traffic features and selects a load balancing group. Then Switch
A selects a real server according to the configured load balancing algorithm, weights,
priorities, inbound/outbound bandwidth limits, connection quantity limits, and
connection rate limits, and replaces the destination MAC address of the request
packets (the destination IP address is still the virtual IP address) with the MAC address
of the real server. Switch A sends the request packets to the real server.
4. The real server sends the response packets to Switch B, and Switch B sends the
response packets to users. The load balancing process is complete.
Load balancing algorithm
It supports the WRR algorithm, least connection algorithm, hash algorithm based on the
IP address, and hash algorithm based on the URL in HTTP packets.
Server health detection
You can configure different probes on the load balancing device to detect the health status
of servers according to different services. Currently, the SPU supports ICMP, Transmassion
Control Protocol (TCP), User Datagram Protocol (UDP), and HTTP probes.
Forwarding mode
In server load balancing, the SPU supports DNAT and DMAC modes.
Session stickiness
Session stickiness indicates that multiple connections of an application layer session are
directed to a server.
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SwitchA
VIP
SwitchB
6 Load Balancing Configuration
ServerA
IPA
ServerB
IPB
ServerC
IPC
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