I'm trying to analyse these two throughput graphs for a dissertation. Could anyone shed some light on what this actually means. FIFO looks worse (and it should be) than CBWFQ, but what does this actually mean.
I'm testing QoS schemes and this result comes from a congested 2MB serial link to see how each perform sending RTP, FTP and ICMP at the same time.
asked 16 Apr '13, 02:18
edited 16 Apr '13, 02:24
As you are talking about QoS, we need more information about the other traffic that passed your device while you measured one connection and the QoS policy for CBWFQ.
Without any further information, I would interpret the two graphs as follows.
The monitored session got a bandwidth of ~72 Kbyte/s (due to the CBWFQ configuration). The spikes are possibly due to a change in the 'line usage', meaning that there was less 'other traffic' and thus your session received more bandwidth as it got available.
I'm sure you know how CBWFQ works. I'm adding a link for all other readers here ;-)
As the name says, the packets are routed as they come in (First In First Out). There is a strong influence on the traffic pattern of a single session based on the rest of the traffic at that time. As we don't know that, I simply guess, that there were several other session and/or protocols passing your device during the time you capture the traffic.
With FIFO the bandwidth for a certain class of traffic is totally unpredictable, as it depends on the rest of the traffic, passing a device (which itself is unpredictable). CBWFQ is not 'better' than FIFO. It is just more predictable, as you can configure which traffic gets how much bandwidth.
answered 16 Apr '13, 04:08
Kurt Knochner ♦