Using APA to Build a Screaming Fast Network Server Connection for HP-UX 11i v2 and v3

Using APA to Build a Screaming Fast Network Server Connections

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IP-based and MAC-based Load Balancing

The IP-based and MAC-based load balancing algorithms both hash the 8 least significant

bits of addressing information stored within an Ethernet packet. From the standpoint of

APA, the only difference is whether the address bits come from the IP address or the DA

address segment of the packet.

Another similarity is that the IP-based and MAC-based load balancing algorithms greatly

resemble the simple, time-proven algorithms used by 802.3 Ethernet switches. The only

difference here is that APA uses four times more addressing data than a switch, when

assigning packets to specific links within a Fast Ethernet or Gigabit Ethernet link

aggregate as shown in the MAC-based illustration above.

A consistent result in load balancing comparisons between switches and HP 9000

servers with APA is that using APA results in a more evenly balanced outbound stream.

Of course, APA could be extended with even more elaborate load balancing algorithms

that use more than the 8 least significant address bits, but only by sacrificing additional

processor resources.

HP APA software hashes the 8

least significant bits of each

address, for switcher-style load

balancing, using a data table with

256 options.

Full Duplex 8Gb Aggregate

FROM SWITCH

A typical switch hashes the 2

least significant bits of each

address for load balancing with

limited results.

Note: APA never negotiates load

balancing of inbound packets with

a switch or even another server

running APA.

TO SWITCH

SWITCH

Gigabit Backbone