06-19-2012 02:21 PM - edited 03-07-2019 07:20 AM
I am trying to tune the QoS on some data centre switches: 2960G and 3750. I have read the configuration guide chapter about QoS, and the relevant parts of Tim Szigeti's book, but there are still some points that are not clear to me. I just want to understand it right.
Finally, I would be interested to hear some thoughts about marking. I am using the usual baseline model as suggested by Tim Szigeti and others. I have a few Solaris 10 clusters spread across two data centres. Each cluster consists of two servers, one in each data centre. Between these, there are two interconnects that each run along a private VLAN, and they take different paths through the network. The traffic on these consists of heartbeats and synchronization. How would you treat this interconnect traffic? AF21? AF31? What do you do?
Kevin Dorrell
Luxembourg
06-19-2012 05:56 PM
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Kevin, have you seen this doc: https://supportforums.cisco.com/docs/DOC-8093 ?
#1 my understanding, those platforms support buffers reserved per interface and also a shared common pool.
#2 above reference shows how to do that, I recall.
#3 I understood with QoS disabled, there's only supposed to be a single FIFO queue. When QoS is globally disabled, you see the individual queue counters increment? What IOS version?
#4 and 5, the above reference might address.
For your cluster heartbeats and sync traffic, I would consider CS2, CS4 or CS5 but none of the AFxy classes, as you probably want to avoid dropping any of this traffic's packets.
06-20-2012 03:57 AM
Joseph, thank you for that.
Wow .. that is a really useful document, and I am still working my way through it. I'll come back here if I need to discuss.
Section 2.1.1 is particularly interesting because it seems to imply that without enabling mls qos there are still the four queues, but that the traffic just uses one of them for user traffic. Control plane traffic still goes on a different queue. That seems to be consistent with what I observe ... that the counters for Q4T3 increment enormously (default traffic), but there are also incrementing counters on Q2T2 and Q2T3 (control plane traffic).
It also makes the pertinent point that just introducing mls qos will probably increase the number of drops, until you tune it properly.
Thanks again
Kevin
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