Terrific! Thank you very much. This will make it much easier to add
sFlow to the project. When we have an implementation working, we'll
definitely take you up on your offer to help us test it.
By the way, I've already updated the bullet point on our project page
to say "sFlow(R)" to keep up our end of the license. ;-)
Thanks again!
--Justin
On Sep 4, 2009, at 4:02 PM, Neil McKee wrote:
Justin,
Please accept this email as written confirmation that you may use
and adapt the source code for the InMon Virtual Probe (http://inmon.com/products/virtual-probe/index.php
) for the implementation of an sFlow agent in the "Open vSwitch"
project (http://openvswitch.org/) under the terms of the sFlow
License (http://www.sflow.org/developers/licensing.php).
Neil McKee
Director
InMon Corp.
On Aug 28, 2009, at 10:38 PM, Neil Mckee wrote:
The sFlow SNMP MIB, while very useful, is optional. It can be
ignored for now.
The only counter-block you really need is the "generic" one, which
exports the basic MIB-II ifTable counters as a single snapshot. I
can see that this might be awkward because these counters must be
updated with every packet, in the fast-path. Still, you'll
probably be expected to provide them eventually one way or another.
The simplest sampling implementation is usually to have just one
packet-sampler for the whole switch, and the critical path there
is just to decrement the countdown to the next sample, so that
part is not going to slow you down at all. I guess it's just a
question of figuring out the best way to queue the samples for
processing in user-space.
There are patents involved, yes, but the main sFlow license
should not be an obstacle (http://www.sflow.org/developers/licensing.php
). The license you were looking at was specific to the virtual
probe implementation. I'll check what we need to do to, but it
looks like it's probably enough for me to say in writing that you
are welcome to use that code as long as you conform to the main
sFlow license. You'll probably rewrite the code anyway :). Our
main goal in putting it out there was just to say "wow, look how
easy this is".
regards,
Neil
On Aug 28, 2009, at 6:23 PM, Justin Pettit wrote:
Hi, Neil. Thanks for the information! We'd like to add native
support, but there are a few things that would need to be done:
- sFlow uses SNMP to communicate between the collector and
agents, and we do not yet have support for SNMP.
- For packet sampling, we'd need to make some modifications to
the protocol used to communicate with the datapath (in addition to
changes in the kernel and userspace).
- For counter sampling, we'd need to keep track of a lot more
information than we currently do.
Luckily, none of these technical issues are hard. Our biggest
concern has been related to licensing and patents, since this is
an open source project. Does InMon claim any patents or licensing
restrictions over projects that implement RFC 3176?
The Virtual Switch Probe looks like a neat program and should work
with the current version of Open vSwitch. However, clause 1(b) in
the license agreement that prevents using it for any commercial
purposes seems a bit worrying.
--Justin
On Aug 28, 2009, at 5:17 PM, Neil McKee wrote:
Hello all,
I saw you had sFlow on your list of features that are "under
development", so I thought I would offer to help if I can. If
you're just getting started, the source code linked from this
page might help:
http://inmon.com/products/virtual-probe/index.php
(It the C source code to an sFlow agent designed to connect to a
virtual SPAN port using libpcap).
If you already have something running, then I'd be happy to help
with the testing.
Neil McKee
InMon Corp.
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