topic Re: APA LB_IP algorithm in Operating System - HP-UX

APA LB_IP algorithm

James Carbonaro — Fri, 01 Apr 2005 17:15:38 GMT

I have successfully installed APA on an HP 3440 connected to a Nortel 8600 switch. The load balancing algorithm is set to LB_IP. On the inbound side, the Nortel uses an XOR of the 6 least significant bits of the source's last octet in ordeer to determine which link to send traffic . Does anyone happen to know what algorithm APA uses to balance outbound traffic from the HP server when in LB_IP mode? The documentation mentions a portion of the source and destination addresses. How many bits from the source and/or destination address and from which octet(s)?

Re: APA LB_IP algorithm

rick jones — Sat, 02 Apr 2005 21:00:31 GMT

I don't know the specifics, but I doubt that anyone in the APA team would have been silly enough to try to use just the high-order bits :)

Do you think there is a problem with LB_IP in APA, or are you simply curious?

If nothing else, some judicious use of netperf or even just FTP I suspect to a system where you change that system's IP address would probably allow you to reverse-engineer it if the APA docs on docs.hp.com don't list it.

Re: APA LB_IP algorithm

Jim Keeble — Sun, 03 Apr 2005 10:51:44 GMT

It uses the last octet of the destination IP address in LB_IP mode.

You might consider using LB_PORT instead. This uses both the source and destination UDP or TCP port numbers (I don't recall id it is the sum or XOR or what of the two), but the combination of ephemeral and server port yields a different value for each connection. That way even if all your outbound traffic goes to the same destination IP, you can still get a reasonable distribution of traffic.

Re: APA LB_IP algorithm

Xianjie Zhang — Mon, 04 Apr 2005 12:44:48 GMT

Hi, James,

Both source and destination IP addresses are used. The last and second last octets are used. (e.g., with an IP of 1.2.3.4, 3 and 4 will be used.)

Regards,

Xianjie