H3C Technologies H3C SecBlade LB Cards - Manual (Page 7)

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Configuring load balancing
Load balancing can be configured only in the Web interface.
Load balancing (referred to as LB hereinafter) is a cluster technology to distribute specific services such as
network services and network traffic among multiple network devices (for example servers and firewalls),
enhancing service processing capability and ensuring high availability of services.
LB delivers the following advantages:
• High performance—LB distributes services to multiple network devices, enhancing the performance
of the whole system.
• Scalability—LB facilitates the addition of network devices in a cluster, meeting the ever-increasing
service requirements for servers without decreasing service quality.
• Reliability—Failure of a single or multiple devices will not result in service interruption, enhancing
the reliability of the entire system.
• Manageability—Administration is performed only on LB-enabled devices, and devices need only
common configuration and maintenance.
• Transparency—A cluster is like a device with high availability and performance, and users are not
aware of and do not care the specific network structure. In addition, increasing or decreasing
devices will not affect normal services.
LB generally falls into the following types:
• Server load balancing—Data centers generally adopt server load balancing for networking.
Network services are distributed to multiple servers to enhance service processing capabilities of
the data centers.
• Firewall load balancing—In networks where firewall processing capabilities have become the
bottleneck, firewall load balancing can be adopted to balance the network traffic among multiple
firewalls to enhance the processing capabilities of firewalls.
Working mechanism of server load balancing
Server load balancing comprises Layer 4 server load balancing and Layer 7 server load balancing:
• Layer 4 server load balancing—Supports IPv4 and IPv6, and is implemented based on streams. It
distributes packets in the same stream to the same server. Layer 4 server load balancing cannot
distribute HTTP-based Layer 7 services based on contents, restricting the application scope of load
balancing services. It can be classified into Network Address Translation (NAT)-mode server load
balancing and direct routing (DR)-mode server load balancing.
• Layer 7 server load balancing—Supports only IPv4, and is implemented based on contents. It
analyzes packet contents, such as HTTP and RTSP, distributes packets one by one based on the
contents, and distributes connections to the specified server according to the predefined policies.
Layer 7 server load balancing applies load balancing services to a large scope and only supports
NAT mode.