Hi Terry
please find zbalance_ipc+tcpdump examples here:

https://github.com/ntop/PF_RING/blob/dev/userland/examples_zc/README.examples 
<https://github.com/ntop/PF_RING/blob/dev/userland/examples_zc/README.examples>

Alfredo

> On 2 Oct 2017, at 22:58, Terry <[email protected]> wrote:
> 
> Hey Alfredo,
> 
> Thank you. Is there documentation on zbalance beyond what I'm finding via 
> Google? I'm not seeing how to use it to create the queues for Tcpdump to 
> attach to.
> 
> -Terry
> 
> 
> On Friday, September 29, 2017 1:05 PM, Alfredo Cardigliano 
> <[email protected]> wrote:
> 
> 
> Hi Terry
> dummy interfaces are usually used with Bro because this consumer is well 
> known to be unstable (or at least it crashes from time to time for some 
> reason)
> leaving ZC queues in an inconsistent state, preventing it from reattaching to 
> the queue again (in order to reattach a zbalance_ipc restart is required).
> As long as tcpdump is closed correctly, there should be no problem attaching 
> to the queues directly. Please note dummy interfaces are slow as traffic
> goes through the kernel, and you loose most of the boost provided by ZC.
> 
> Alfredo
> 
>> On 29 Sep 2017, at 18:53, Terry <[email protected] 
>> <mailto:[email protected]>> wrote:
>> 
>> Hey Alfredo,
>> 
>> Thanks, the zbalance stuff looks encouraging. How would this look in the 
>> context of users constantly running/terminating their own instances of 
>> tcpdump? I see the "Best practices for using Bro IDS with PF_RING ZC" 
>> article, where ZC outputs to dummy interfaces which are then used by the 
>> application. Is this how we would do it -- set up one-to-one mappings of ZC 
>> Interface -> Dummy Interface, and then have users use the dummy interfaces 
>> with tcpdump rather than the ZC interfaces directly?
>> 
>> -Terry
>> 
>> 
>> On Friday, September 29, 2017 5:12 AM, Alfredo Cardigliano 
>> <[email protected] <mailto:[email protected]>> wrote:
>> 
>> 
>> Hi Terry
>> ZC is a kernel-bypass technology, this means that the application takes full 
>> control over the NIC
>> in order to access the card memory in zero-copy and maximise the 
>> performance. This implies that
>> one process at a time can open an interface, thus what you are seeing with 
>> tcpdump is expected.
>> This said, there is a way to overcome this: you can use zbalance_ipc to open 
>> the zc interface, and
>> let it distribute the traffic (fanout) to multiple applications by means of 
>> zc queues. Please note this
>> adds some overhead with respect to opening the zc interface directly from 
>> the application, however
>> you should not notice the difference as tcpdump itself is a bottleneck.
>> 
>> Alfredo
>> 
>>> On 29 Sep 2017, at 00:29, Tom J. <[email protected] 
>>> <mailto:[email protected]>> wrote:
>>> 
>>> Hello,
>>> 
>>> We're exploring using PF-RING ZC for our packet sniffers, but are looking 
>>> to get clarity on an issue before purchasing licenses.
>>> 
>>> The sniffers are standard servers running Linux, each with (16) 10G NIC 
>>> ports connected to SPAN ports on switches. Users log into the system and 
>>> run TCPDUMP to troubleshoot day-to-day connectivity issues in the 
>>> environment.
>>> 
>>> As traffic levels have increased we're seeing more and more drops on the 
>>> NICs, so the thought was to implement ZC to make things better. But it 
>>> looks like ZC may limit us to one capture per NIC at any given time. Is 
>>> this correct? I see text on the product page about not being able to do 
>>> standard networking activities on a given NIC when ZC is actively running, 
>>> but how about multiple ZC-enabled TCPDUMPs at once? It doesn't seem to work 
>>> for us (getting a "No such device" error), but maybe it's something we're 
>>> doing wrong.
>>> 
>>> Would appreciate any guidance.
>>> 
>>> -Terry
>>> 
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>> 
>> 
> 
> 
> 

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