Subject: [mif] MIF Problem Statement

From: Dominik Kaspar <[email-masked]>
Date: Thu, 3 Sep 2009 13:10:09 +0100

Hi,

I have been working on MIF-related topics for a while now, but only
recently discovered the existence of the MIF working group. Excuse me
if I ask questions that might have already been sorted out in the
meeting or on the list.

The MIF charter specifies (among other things) the following restrictions:

- The group shall not develop new protocol or policy mechanisms.
- No work will be done to enable traffic flows to move from one
interface to another.

To my knowledge, all major operating systems can cope with multiple
interfaces and make a decision about using one of them for all new
traffic flows. I am therefore curious if the group will work on
assigning new traffic flows to the available network interfaces (based
on known or measured link characteristics) or if that contradicts with
the goal of not developing new policy mechanisms?

One solution that already seems to work pretty well is Equal-Cost
Multipath Routing, which (after some non-standardized configuration
difficulties) can also be set up on MIF end-hosts. At least with
Linux, a small ECMP routing table entry can have great flow
aggregation effects when many transport connections are opened.

Best regards,
Dominik

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From: Zhen Cao <[email-masked]>
Date: Fri, 4 Sep 2009 14:37:04 +0800

Hi Dominik,

I am interested in the issues you raised here. See my comments in line.

Best regards,
Zhen

> - The group shall not develop new protocol or policy mechanisms.
some problems are not clear for multiple interfaces, so the WG would
like to be more informed of the problem before working on protocols
and mechanisms.

> - No work will be done to enable traffic flows to move from one
Move of the flows is out of scope, but IMO, source address selection,
which is related to this problem, is under consideration.

> the goal of not developing new policy mechanisms?

But many operation systems and connection managers have not fully
utilized all the available interfaces. For instance, my windows xp can
only send data flows via one default gateway.

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>

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From: Dominik Kaspar <[email-masked]>
Date: Fri, 4 Sep 2009 08:38:40 +0100

Hi Zhen,

Thanks for your feedback. I agree there is no such thing as a
connection manager in Windows XP. That would be very convenient.
However, if you connect to two networks and then explicitly bind a
socket to Interface 1 and another socket to Interface 2, then flow
aggregation should also work in Windows XP. Maybe the local routing
table needs some small modifications?

However, the problem about MIF is not only about technical and
configuration issues. If there are no user preferences about how and
when to use which interface, the OS has a big challenge of making a
good decision of how to assign flows to interfaces. If I were Windows
XP, I also wouldn't risk binding your real-time video stream to the
3.5G interface if there is also an Ethernet interface available ;-)

Dominik