HP Auto Port Aggregation Administrator's Guide HP-UX 11i v3 (766140-001, March 2014)
Therefore, HP prefers you use the algorithm that is recommended for each supported configuration.
See “Preparing for configuration” (page 23) for more information.
The load balancing algorithm consists of the following steps:
1. Data Flow Lookup — The load distribution algorithm determines an index into a hash table
that includes the physical port through which the outbound data flow is forwarded.
2. Data Flow Physical Port Assignment — If the hash index for the data flow has not been assigned
a physical port (the entry is empty), a physical port in the link aggregate is assigned to that
specific hash index. The physical port is selected on a Round Robin basis.
3. Aging Data Flows — Over time, each data flow is checked to determine if it is still active. If
the data flow has not been active in the last 30 seconds, its specific hash index is cleared
(aged out). If the data flow restarts after being cleared from the hash table, it is reassigned a
new physical port on a Round Robin basis. For information on clearing a data flow and
initiating the load balancing process, see “Resetting a data flow” (page 47).
Each load distribution algorithm guarantees that it will not introduce any severe ordering problems
within a specific data flow. This is required to ensure that the performance is not degraded
significantly as a result of turning on one of the algorithms.
Also, all packets for a specific data flow always flow out through the same physical port until the
data flow is aged out of the distribution table. This means that in order to generate simultaneous
load on each of the physical ports in a link aggregate, start multiple data flows over the link
aggregate. HP APA provides load balancing on outbound data transfers and inbound load
balancing is the responsibility of link partner.
Failover group
HP APA enables you to combine multiple physical link ports into one failover group. A failover
group is a link aggregate in LAN_MONITOR mode, but with the following differences:
• One port is the active link, and the others are standby links. Network traffic is sent and received
on the active port.
• LAN Monitor periodically exchanges APA packets between the links making up the failover
group. This enables better detection of non-operational links in the failover group.
• If the active port or its link partner fails, LAN Monitor automatically migrates the traffic to one
of the standby ports in the failover group. When a port with a higher priority than the current
active port recovers, the network traffic is migrated back to the previous active port. Sometimes,
it is desirable to have the network traffic remain on the current active port after the failure and
recovery of the previous active port. To achieve this, set the HP APA port priorities the same
for all ports in the failover group.
• You can use 100BT, Gigabit, 10 Gigabit Ethernet (10GbE), or InfiniBand IPoIB devices in the
failover group. However, all the devices in the failover group must be of one type: 100BT,
Gigabit, 10GbE, or IPoIB.
• The failover group can have one or more IP addresses assigned to it.
• By default, the physical ports in the failover group do not share a common MAC address. The
HP APA enables you to assign a fixed MAC address for the failover group. For more
information on assigning a fixed MAC address for failover groups, see “Editing configuration
files for failover groups” (page 86).
• You can include link aggregates in a failover group. This enables increased bandwidth and
load balancing in a failover group.
Proactive failover
By default, the port in a failover group with the highest priority is the active port. This is called
priority-based failover. However, HP APA also allows you to configure failover groups with proactive
failover.
Conceptual overview 9