Radware Alteon Application Manual page 181

Minimum Misses
The minmisses metric is optimized for cache redirection. It uses IP address information in the client
request to select a server. When selecting a server, Alteon calculates a value for each available real
server based on the relevant IP address information. The server with the highest value is assigned
the connection. This metric attempts to minimize the disruption of persistency when servers are
removed from service. This metric should be used only when persistence is required.
By default, the minmiss algorithm uses the upper 24 bits of the source IP address to calculate the
real server that the traffic should be sent to when the minmisses metric is selected. Alteon allows
the selection of all 32 bits of the source IP address to hash to the real server.
The source or destination IP address information used depends on the application:
• For application redirection, the client destination IP address is used. All requests for a specific IP
destination address are sent to the same server. This metric is particularly useful in caching
applications, helping to maximize successful cache hits. Best statistical load balancing is
achieved when the IP address destinations of load-balanced frames are spread across a broad
range of IP subnets.
• For SLB, the client source IP address and real server IP address are used. All requests from a
specific client are sent to the same server. This metric is useful for applications where client
information must be retained on the server between sessions. With this metric, server load
becomes most evenly balanced as the number of active clients with different source or
destination addresses increases.
To select all 32 bits of the source IP address, use the command,
. This 32-bit hash is most useful in the wireless world.
32
The minmisses metric cannot be used for Firewall Load Balancing (FWLB), since the real server IP
addresses used in calculating the score for this metric are different on each side of the firewall.
Hash
The hash metric uses IP address information in the client request to select a server. The specific IP
address information used depends on the application:
• For application redirection, the client destination IP address is used. All requests for a specific IP
destination address are sent to the same server. This is particularly useful for maximizing
successful cache hits.
• For SLB, the client source IP address is used. All requests from a specific client are sent to the
same server. This option is useful for applications where client information must be retained
between sessions.
• For FWLB, both the source and destination IP addresses are used to ensure that the two
unidirectional flows of a given session are redirected to the same firewall.
When selecting a server, a mathematical hash of the relevant IP address information is used as an
index into the list of currently available servers. Any given IP address information will always have
the same hash result, providing natural persistence, as long as the server list is stable. However, if a
server is added to or leaves the set, then a different server might be assigned to a subsequent
session with the same IP address information even though the original server is still available. Open
connections are not cleared. The phash metric can be used to maintain stable server assignment.
For more information, see
Note: The hash metric provides more distributed load balancing than minmisses at any given
instant. It should be used if the statistical load balancing achieved using minmisses is not as optimal
as desired. If the load-balancing statistics with minmisses indicate that one server is processing
significantly more requests over time than other servers, consider using the phash metric.
Document ID: RDWR-ALOS-V2900_AG1302
Alteon Application Switch Operating System Application Guide
Persistent Hash, page 182.
Server Load Balancing
/cfg/slb/group x/mhash
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