Riverstone Networks WICT1-12 - Manual (Page 500)

22-2 Riverstone Networks RS Switch Router User Guide Release 8.0
Load Balancing Web Hosting Configuration
22.1.1 Creating the Server Group
To use load balancing, you create a logical group of load balancing servers and define a virtual IP address that the
clients will use to access the server pool.
The following example configures the “abccompany-www” load balancing group:
Specifying a Protocol
When you configure a load balancing group, you need to specify the protocol of the traffic that will be load balanced.
There is no default. Select the protocol based on what you think the majority of traffic will be for that group. For
example, you may want to specify TCP if you expect the majority of traffic to be HTTP requests.
• Specify
ip
to perform Layer 3 load balancing. This protocol uses an IP-hash algorithm to load
balance.
• Specify
tcp
if you want the RS to perform application load balancing and application health checks.
You can specify a port to control which port performs the load balancing. If you don’t specify a port,
any one of the ports in the group will be used for load balancing. When you specify
tcp
as the
protocol, the default load balancing policy is round robin. You can change the load balancing policy
to weighted round-robin, fastest, predictive, or least loaded. (See "Specifying a Load Balancing
Policy" for more information about these policies.) UDP traffic through a TCP load-balanced group
is load balanced using the IP hash algorithm.
• Specify
udp
to perform UDP load balancing, such as DNS. For UDP sessions, it is difficult to signal
the end of a session because UDP is connectionless. Therefore, a fixed IP-hash policy is used to
ensure that the client always goes to the same server.
Intrinsic Persistence Checking
Load balancing clients connect to a virtual IP address, which in reality is redirected to one of several physical servers
in a load balancing group. In many web page display applications, a client may have its requests redirected to and
serviced by different servers in the group. In certain situations, however, it may be critical that all traffic for the client
be directed to the same physical server for the duration of the session; this is the concept of session persistence.
When the RS receives a new session request from a client for a specific virtual address, the RS creates a binding
between the client (source) IP address/port socket and the (destination) IP address/port socket of the load balancing
server selected for this client. Subsequent packets from clients are compared to the list of bindings: if there is a match,
the packet is sent to the same server previously selected for this client; if there is not a match, a new binding is created.
How the RS determines the binding match for session persistence is configured with the
persistence-level
option
when the load balancing group is created.
rs(config)# load-balance create group-name abccompany-www virtual-ip
207.135.89.16 virtual-port 80 protocol tcp