Cisco Systems 78-11741-02 Wireless Office Headset User Manual


 
Configuring Server Load Balancing
IOS SLB Functions and Capabilities
IPC-135
Cisco IOS IP Configuration Guide
SynGuard
Dynamic Feedback Protocol for IOS SLB
Alternate IP Addresses
Transparent Web Cache Balancing
NAT
Redundancy Enhancement—Stateless Backup
Algorithms for Server Load Balancing
IOS SLB provides two load-balancing algorithms: weighted round robin and weighted least connections.
You may specify either algorithm as the basis for choosing a real server for each new connection request
that arrives at the virtual server.
Weighted Round Robin
The weighted round robin algorithm specifies that the real server used for a new connection to the virtual
server is chosen from the server farm in a circular fashion. Each real server is assigned a weight, n, that
represents its capacity to handle connections, as compared to the other real servers associated with the
virtual server. That is, new connections are assigned to a given real server n times before the next real
server in the server farm is chosen.
For example, assume a server farm comprises real server ServerA with n =3, ServerB with n =1, and
ServerC with n = 2. The first three connections to the virtual server are assigned to ServerA, the fourth
connection to ServerB, and the fifth and sixth connections to ServerC.
Note Assigning a weight of n = 1 to all of the servers in the server farm configures the IOS SLB switch to
use a simple round robin algorithm.
Weighted Least Connections
The weighted least connections algorithm specifies that the next real server chosen from a server farm
for a new connection to the virtual server is the server with the fewest number of active connections.
Each real server is assigned a weight for this algorithm also. When weights are assigned, the server with
the fewest number of connections is based on the number of active connections on each server, and on
the relative capacity of each server. The capacity of a given real server is calculated as the assigned
weight of that server divided by the sum of the assigned weights of all of the real servers associated with
that virtual server, or n
1
/(n
1
+ n
2
+ n
3
...).
For example, assume a server farm comprises real server ServerA with n =3, ServerB with n =1, and
ServerC with n = 2. ServerA would have a calculated capacity of 3/(3 + 1 + 2), or half of all active
connections on the virtual server, ServerB one-sixth of all active connections, and ServerC one-third of
all active connections. At any point in time, the next connection to the virtual server would be assigned
to the real server whose number of active connections is farthest below its calculated capacity.
Note Assigning a weight of n = 1 to all of the servers in the server farm configures the IOS SLB switch to
use a simple least-connection algorithm.