neil.mckee at inmon.com
Fri Sep 4 23:02:46 UTC 2009
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/
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".
> 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.
>> 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:
>>> (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.
>>> discuss mailing list
>>> discuss at openvswitch.org
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