LARTC - Jan 2003 - Latest techniques for multiple PPP load-balancing

Hey,

I''ve been scouring the web these past few days trying to find a
suitable
technique to load balance my network. Unfortunately I think my setup is
very uncommon, so I''m looking to you guys to see if you can help.

I currently have 2 ADSL modems, provided by the same ISP and terminating
on the same gateway (I think having the same gateway is what is causing
the problems, since the nexthop is always the same for each interface).
I''ve tried using equal cost multipath (using ip route to set two
nexthops with equal weights).  Problem is I believe this uses route
lookups to determine which interface to use, and thus for sending data
to common destinations it only ever uses 1 interface.

Does anyone know if its even possible to send packets over each
interface "equally"?  I read somewhere that you might be able to clear
the route cache after every packet, but I''ve only seen people talk
about
it and don''t know if its true.

Can anyone help?

I''m running 2.4.20 on Debian (woody), with both ADSL modems using PPPoA
and with most of the QoS and network queuing modules installed.  AFAIK,
my provider doesn''t support multilink.

Thanks,
Andy.

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On Sun, Jan 19, 2003 at 01:32:15AM -0000, Andy Coates wrote:
> I currently have 2 ADSL modems, provided by the same ISP and terminating
> on the same gateway (I think having the same gateway is what is causing
> the problems, since the nexthop is always the same for each interface).
> I''ve tried using equal cost multipath (using ip route to set two
> nexthops with equal weights).  Problem is I believe this uses route
> lookups to determine which interface to use, and thus for sending data
> to common destinations it only ever uses 1 interface.
> 
> Does anyone know if its even possible to send packets over each
> interface "equally"?  I read somewhere that you might be able to
clear
> the route cache after every packet, but I''ve only seen people talk
about
> it and don''t know if its true.
> 
> Can anyone help?
> 
> I''m running 2.4.20 on Debian (woody), with both ADSL modems using
PPPoA
> and with most of the QoS and network queuing modules installed.  AFAIK,
> my provider doesn''t support multilink.
I''ve done this in a previous life on a [patched] 2.2 kernel with using
ISDN-interfaces, using the ''equalize'' parameter in the nexthop
statement.
Possibly, 2.4 supports this natively - but I cannot test it at home.

You could try something along the lines of the following though (note the
equalize!):

ip route add default scope global equalize nexthop dev ppp0 via 12.34.56.78 \
      nexthop dev ppp1 via 12.34.56.78

(It won''t give you doubled download speed of course, this will only
help you
while uploading - but only if your provider isn''t doing per-connection
egress filtering in the upstream gateway)

Regards,
-- 
Jasper Spaans
http://jsp.vs19.net/contact/

> On Sun, Jan 19, 2003 at 01:32:15AM -0000, Andy Coates wrote:
> 
> > I currently have 2 ADSL modems, provided by the same ISP and 
> > terminating on the same gateway (I think having the same gateway is 
> > what is causing the problems, since the nexthop is always 
> the same for 
> > each interface). I''ve tried using equal cost multipath 
> (using ip route 
> > to set two nexthops with equal weights).  Problem is I believe this 
> > uses route lookups to determine which interface to use, and 
> thus for 
> > sending data to common destinations it only ever uses 1 interface.
> > 
> > Does anyone know if its even possible to send packets over each 
> > interface "equally"?  I read somewhere that you might be 
> able to clear 
> > the route cache after every packet, but I''ve only seen people
talk
> > about it and don''t know if its true.
> > 
> > Can anyone help?
> > 
> > I''m running 2.4.20 on Debian (woody), with both ADSL modems
using
> > PPPoA and with most of the QoS and network queuing modules 
> installed.  
> > AFAIK, my provider doesn''t support multilink.
> 
> I''ve done this in a previous life on a [patched] 2.2 kernel 
> with using ISDN-interfaces, using the ''equalize''
parameter in
> the nexthop statement. Possibly, 2.4 supports this natively - 
> but I cannot test it at home.
> 
> You could try something along the lines of the following 
> though (note the
> equalize!):
> 
> ip route add default scope global equalize nexthop dev ppp0 
> via 12.34.56.78 \
>       nexthop dev ppp1 via 12.34.56.78
> 
> (It won''t give you doubled download speed of course, this 
> will only help you while uploading - but only if your 
> provider isn''t doing per-connection egress filtering in the 
> upstream gateway)
Hi,

I''ve tried that as well, but it still only seems to use one interface
when attempting to send data to a specific host (and even trying another
connection to the host results in the packets going over the same
interface).

Seems like its using this route caching to determine which interface to
go over still :(

"ip route" shows:
default equalize
        nexthop via 212.104.130.141  dev ppp0 weight 1
        nexthop via 212.104.130.141  dev ppp1 weight 1

So it at least appears to have set it correctly (it added the weights
itself)

Andy.

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Andy Coates wrote:
>Hi,
>
>I''ve tried that as well, but it still only seems to use one
interface
>when attempting to send data to a specific host (and even trying another
>connection to the host results in the packets going over the same
>interface).
>
>Seems like its using this route caching to determine which interface to
>go over still :(
>  
>
thats what the equalize patch prevents. btw, it is not included in 2.4 
(or 2.5), you
can find a 2.4.18 version at trash.net/~kaber.
>"ip route" shows:
>default equalize
>        nexthop via 212.104.130.141  dev ppp0 weight 1
>        nexthop via 212.104.130.141  dev ppp1 weight 1
>
>So it at least appears to have set it correctly (it added the weights
>itself)
>
without the patch its won''t do what you expect.

Patrick

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> Andy Coates wrote:
> 
> >Hi,
> >
> >I''ve tried that as well, but it still only seems to use one 
> >interface 
> >when attempting to send data to a specific host (and even trying 
> >another connection to the host results in the packets going over the 
> >same interface).
> >
> >Seems like its using this route caching to determine which 
> >interface to go over still :(
>
> thats what the equalize patch prevents. btw, it is not included 
> in 2.4 (or 2.5), you can find a 2.4.18 version at trash.net/~kaber.
Thanks for that, from what I''ve read I''d have never known it
wasn''t
included.
> >"ip route" shows:
> >default equalize
> >        nexthop via 212.104.130.141  dev ppp0 weight 1
> >        nexthop via 212.104.130.141  dev ppp1 weight 1
> >
> >So it at least appears to have set it correctly (it added the weights
> >itself)
> >
> without the patch its won''t do what you expect.
I''ve applied the patch and can confirm it does work as I expected!
Thank
you so much :)

Andy.

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Em Mon, Jan 20, 2003 at 06:16:48PM -0000, Andy Coates
escreveu:
> > without the patch its won''t do what you expect.
> 
> I''ve applied the patch and can confirm it does work as I expected!
Thank
> you so much :)
Let me get this straight.
Stock kernel has already multipath routing, right?
It also has the equalize option. BUT it doesn''t work as expected, so
there is this new patch which makes equalize better and sort of bypass
the routing cache, is that it?

Or was the equalize option from ip being silently ignored?
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