Dual LAN’s do improve throughput; however, it is difficult to measure,
and certainly can’t be measured by just one virtual circuit using
send/receive/reply. In order to verify that load balancing does indeed
work, you need to create a reply driven server with lots of clients
(since you need to “fill up” the media to see the load balancing
starting to work - i.e. Net will only get to the point where it is
transmitting 2 different packets simultaneously over the two lans when
it has a sufficient amount of packets in the queue that it can fill up
one pipe). If you create a test app like the one described, you will
see that the aggregate throughput between all clients and the server
will exceed the bandwidth of one of the lan links (thus verifying that
load-balancing really does occur). I have done this; note, however,
that 2 lans will not give you double the throughput - I have found that
175% of the throughput of a single lan can be achieved on modest
From a real-time perspective load-balancing is a bit of a white
elephant. I think the Qnet approach of real redundancy (simultaneously
txing 2 identical packets), is much more appropriate for distributed
real-time systems (since worst case transmission time remains identical
when a link fails - this is not the case with QNX4).
From: firstname.lastname@example.org (Mario Charest)
Posted At: Friday, April 13, 2001 7:01 AM
Posted To: qnx4
Conversation: Net Manager not load balancing
Subject: Re: Net Manager not load balancing
On Thu, 12 Apr 2001 21:29:07 -0500, “scott krekling”
I personnaly know of no option to control this.
Dual lan on QNX4 is IMO only usefull for redudancies.
A few years ago a friend a mine try dual lan to improve
thoughput, apparently it didn’t help at all.
Does anyone know how to get the QNX 4 Net Manager to load balance
between two ethernet networks? It fails over to either network for
tolerance fine, but i see no load balancing for better throughput. OS
4.25J running on compaq ml350 servers.
Lan 1 consists of two corman fast ethernet cards using Net.tulip
with a netgear 10/100base T hub.
Lan 2 consists of two compaq feature boards w/ ethernet port using
Thanks for any help you can give.