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]> wrote:
 

 Hi TerryZC 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 thatone 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, andlet 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]> 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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