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Date:      Wed, 10 Feb 2010 20:11:22 -0800
From:      "Li, Qing" <qing.li@bluecoat.com>
To:        <current@freebsd.org>, <net@freebsd.org>
Cc:        qingli@freebsd.org
Subject:   ECMP enhancement
Message-ID:  <B583FBF374231F4A89607B4D08578A43046737AF@bcs-mail03.internal.cacheflow.com>

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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=20
that the interface link-state is not reflected in the route entry. For =
example,=20
if there are two interfaces on the same prefix, the cable on one =
interface is=20
unplugged, new and existing connections should switch over to the other =
interface.=20
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=20
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

This is not the final version. Your comments are welcome.

-- Qing




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