ECMP enhancement

[Li, Qing]

Balaji,
 
This patch came out of an offline discussion I had 
with someone else about a month ago. That person was
asking about the ECMP usage in general, and he reported a 
couple of problems with ECMP operation to me privately.
 
This patch was created to address those reported issues.
This patch has nothing to do with you and it's not a reply 
to your email.
 
I have not had any time to review what you sent to me,
which was why I asked you to send whatever you have
to the mailing lists for anyone else who might be
interested in looking at what you've done.
 
But I recommended to you privately to hold off on any
back port because there are multiple pieces involved
to make the ECMP code effective. For example, the 
flow-table code needs to be there, too. Both Kip 
and I are still evolving the implementation. 
 
Since you are new to both FreeBSD and the networking
kernel, I told you the ECMP code is probably not the best 
piece to start with, but you seem to ignore whatever I have 
said completely ...
 
-- Qing
 



________________________________

From: owner-freebsd-current at freebsd.org on behalf of Balaji G
Sent: Thu 2/11/2010 12:21 AM
To: Li, Qing
Cc: qingli at freebsd.org; current at freebsd.org; net at freebsd.org
Subject: Re: ECMP enhancement



Hi Qing

> I have a patch that addresses the above issues. The patch is available at:

>   http://people.freebsd.org/~qingli/ecmp-linkstate-patch.diff<http://people.freebsd.org/%7Eqingli/ecmp-linkstate-patch.diff <http://people.freebsd.org/~qingli/ecmp-linkstate-patch.diff> >

Thanks for the reply. I had sent you an email to you on load balancing
couple of days back and thanks for the reply. I ll roll in the patch and
give it a shot.

Cheers,
  - Balaji



On Thu, Feb 11, 2010 at 9:41 AM, Li, Qing <qing.li at bluecoat.com> wrote:

>
> One of the advantages of enabling ECMP is to allow for connection load
> balancing.
> Currently the address alias handling method is colliding with the ECMP
> code.
> For example, when two interfaces are configured on the same prefix, only
> one prefix route is installed. So connection load balancing is not
> possible.
>
> The other advantage of ECMP is for failover. The issue with the current
> code, is
> that the interface link-state is not reflected in the route entry. For
> example,
> if there are two interfaces on the same prefix, the cable on one interface
> is
> unplugged, new and existing connections should switch over to the other
> interface.
> This is not done today and packets go into a black hole.
>
> I discussed about these issues on the list about a month ago.
>
> Also, there is a small bug in the kernel where deleting ECMP routes in the
> userland will always return an error even though the command is
> successfully
> executed.
>
> I have a patch that addresses the above issues. The patch is available at:
>
>   http://people.freebsd.org/~qingli/ecmp-linkstate-patch.diff<http://people.freebsd.org/%7Eqingli/ecmp-linkstate-patch.diff <http://people.freebsd.org/~qingli/ecmp-linkstate-patch.diff> >
>
> This is not the final version. Your comments are welcome.
>
> -- Qing
>
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