nProbe

Port Mirror vs Network Tap
In order to analyze network traffic, it’s necessary to feed ntop/nProbe with network packets. There are two solutions to the problem: port mirror (also called SPAN in Cisco parlance) network tap Prior to explain the differences between these two solutions, it’s important to understand how ethernet works. In 100 Mbit and above, hosts usually speak in full duplex meaning that a hosts can both send and receive simultaneously. This means that on a 100 Mbit cable connected to a host, the total amount of traffic that a host can send/receive is …
PF_RING

IRQ Balancing
On Linux, interrupts are handled automatically by the kernel. In particular there's a process named irqbalancer that is responsible for balancing interrupts across processors. Unfortunately the default is to let all processors handle interrupts with the result that the overall performance is not optimal in particular on multi-core systems. This is because modern NICs can have multiple RX queues that work perfectly if cache coherency is respected. This means that interrupts for ethX-RX queue Y must be sent to 1 (one) core or at most to a core and its Hyper-Threaded (HT) companion. If multiple processors handle the same RX queue, this invalidates the cache and performance gets worse. For this reason IRQ balancing is the key for performance. In particular what I suggest is to have 1/2 (in case of HT) core(s) handle the same interrupt. For this reason on Linux interrupts are usually send to all processors hence /prox/irq/X/smp_affinity is set to ffffffff that means all processors. Instead as I have just stated above it's better to avoid that all processors handle all interrupts. Example Read more

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