RE: Round Robin Load Balancing

["Daniel Chemko" <dchemko@smgtec.com>]

There is an extension that says something like every N packets, execute
this rule. I forgot what it was called though.. *doh*

Try looking back ~ 1 month ago. I know I saw it there somewhere.

-----Original Message-----
From: Javier Govea [mailto:jgovea@magma.ca] 
Sent: Thursday, July 17, 2003 1:30 PM
To: Ramin Dousti; Daniel Chemko
Cc: netfilter@lists.netfilter.org
Subject: Re: Round Robin Load Balancing

I undesrtand what you mean about perfect load balancing (i'm not
actually looking for a
perfect load balancer) I have two examples below, but first i will
responde some of the
questions.

> Do these two ppp accounts belong to the same ISP? 
Yes. I have four accounts, all of them with the same ISP
>Does the ISP drop forign src?
?????
> Is the gateway doing nat? 
Yes, im using iptables to setup the nat
> Do you have any preference on one of the ppp's than the other? 
No
>Can you bond (mppp)?
I haven't tried multilink ppp...i will look into this...

> You could also setup something like BGP to allow multiple routes
to....
I don't know if this would be the best approach. I already tried to
setup BGP and OSPF 
routes using zebra (http://zebra.org) and i never made it work....
I found a tool called EQLPlus
(http://www.cwareco.com/download/eqlplus.html) but i was
never able to compile it. Has anybody has tried eqlplus before???????

> If one user makes a request out of line X then the return packet HAS
to come back      
 > through line X. So, if one guy sends a huge request taking minutes to
fulfill, he / she
> will tie up the line until the job is finished

Absolutely. I can live with that, but here is my problem. I have 4 ppp
links on my router
(which is doing nat). Then if in a host, located in my LAN which
connected to my router, i
open four browsers and each browser is pointing to the same site then
i'm expepecting each
web page to be requested and returned in a different link. But that
doesn't happen. Some
times it does happen but most of the time i get three of the responses
on one link, one in
another and the other two links do nothing. Sometimes i get 2,1,1,0 ....

I did another test...i have website with has in its main web page has
only 4 images
(differnt images but all of them of exactely the same size). if i point
my browser to that
site, then i'm believe the browser is sending four http requests (one
for each image),
well i would expect one image on each link....but again sometimes i get
the four images on
the same link...some times i get 2 images in one link...

So, i don't want a perfect load balancer but i would like to fix the
problems on my two
examples... i thought about implementing a round robin algorithm for
load balancing where
my first request goes on my first available link, the second one on the
second available
link and so on....this idea fixes my problems in my two previous
examples, but i'm open to
suggestions....

any tips, pointer, ideas are all welcome...

cheers...
X



> Absolutely. Perfect load balancing needs to be coordinated on _all_
the
> endpoints of the links involved. In this case, 4 endpoints.
> 
> For a regular load balancing (which is going to be the case here)
> we still have lots of unknown variables. Do these two ppp
> accounts belong to the same ISP? Does the ISP drop forign src?
> Is the gateway doing nat? Do you have any preference on one of
> the ppp's than the other? Can you bond (mppp)? And so on.
> But a fun project, though, for someone who has time...
> 
> Ramin
> 
> On Tue, Jul 15, 2003 at 12:44:40PM -0700, Daniel Chemko wrote:
> 
> > Because of the nature of your setup, you cannot have a perfect equal
> > load balance setup. This is because you cannot control the inbound
flow
> > of data. If one user makes a request out of line X then the return
> > packet HAS to come back through line X. So, if one guy sends a huge
> > request taking minutes to fulfill, he / she will tie up the line
until
> > the job is finished. The load balancer should be smart enough to not
> > send any more requests to that line, but you are still seeing the
line
> > being monopolized by this single connection, hence it is not
balanced
> > over all lines equally.
> > 
> > In order to have fair balancing of all lines, I think you need to
set up
> > a deal with your ISP to load balance on their end as well.
> > 
> > You could also setup something like BGP to allow multiple routes to
the
> > same return address, but I am not familiar enough with BGP to be
much
> > help in this area. In all likelihood, you are better off with your
> > current solution or maybe the ISP solution if it is supported by
them
> > (more money usually).
> > 
> > 
> > 
> > -----Original Message-----
> > From: Javier Govea [mailto:jgovea@magma.ca] 
> > Sent: Tuesday, July 15, 2003 12:34 PM
> > To: netfilter@lists.netfilter.org
> > Subject: Round Robin Load Balancing 
> > 
> > Hi,
> > 
> > I'm trying to do some load balancing with four ppp connections. Here
is
> > what i have: a LAN
> > connected to a redhat box which has four ppp interfaces. All the
boxes
> > in the LAN are
> > accesing internet through the ppp interfaces in the redhat box. I'm
> > using iproute2, in my
> > redhat box, to setup the the four ppp interfaces as my default out
going
> > route (as
> > described in LART <a
href='http://lartc.org/howto/index.html'>http://lartc.org/howto/index.ht
ml</a>) and I'm using
> > iptables to masquerade
> > all the traffic comming from the LAN. 
> > 
> > My setup is working fine, ie. my LAN can access the net throught the
> > four ppp interfaces.
> > My problem is that i don't know how is the load balancing working.
Some
> > times one of the
> > ppp interfaces is used more than the others (and that is my
problem).
> > According to LART
> > the routes are cached, can someone go a bit into more details in
this
> > caching thing??? how
> > does it work?  which particular files in the kernel are doing this?

> > 
> > I would like to implement a simple round robing algorithm (with no
> > caching) for doing the
> > laod balancing. That is first connection established gose through
ppp0,
> > the second
> > connection on ppp1 and so on. 
> > 
> > I could hack iproute2 and/or iptables, but i'm not sure about which
> > particular files i
> > should hack in order to implement this round robin algorithm. I
actually
> > don't know if
> > what i want makes any sense
> > 
> > Any ideas or pointers are all very well appreaciated.
> > Thanx to all
> > X
> > 
> > 
>