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  • 1.  QoS queuing based on DSCP alone?

    Posted Feb 14, 2014 06:29 AM

    I have the following setup:

     

     

    SwA---SwB---SwC

     

     

    Where the middle switch is 3500 and switches either side are 5800.

     

     

    SwC contains 2 hosts and is configured so that host A has its DSCP altered to EF while the other host is Best Effort, but no queuing takes place here as intended. These hosts run Jperf.

     


    Switch A contains Jperf server.

     

     

    SwC is configured with qos dscp-map 101110 priority 5 and qos typ-of-service diff-services, with the expectation that traffic coming from SwC host A is put into a high priority queue and given more bandwidth as it traverses the switch to destination SwA Jperf server.

     

     

    With the jPerf server on SwA I ran a constant ping to host A and ran wireshark. This confirmed that SwA was receiving packets from host A with  expected DSCP value of EF.

     

     

    I then configured SwB to alter DSCP EF to AF11, to see if SwB was recognising the DSCP from host A. Wireshark confirmed that SwB did alter the DSCP.

     

     

    Why does SwB not perform queuing? does queuing only pertain to other classifiers such as device IP, VLAN ID, interface and port number? if so, then it's impossible to put call signalling traffic into a queue, and VoIP traffic would only be queued if I used VLAN ID.

     

    Also, show qos queue-config shows the 8 queues mapped to 802.1p priorities and memory %.  Does the memory % mean that the switch performs weighted fair queuing based on these weights? if not, what queuing mechanism does it use and what are the weights? queues 4-8 each have memory of 10% assigned while queue 3 has 30%, is this buffer size?

     



  • 2.  RE: QoS queuing based on DSCP alone?

    Posted Feb 14, 2014 09:53 AM

    I moved host b to Sw B and then it worked.

     

    Host A transmitted at 6.5Mbit/sec and Host B at 2.5Mbit/sec over a 10Mbit/sec link.

     

    So SwB won't queue traffic from other switches unless SwB has its own hosts transmitting data.

     

    show qos queue-config shows buffers

    show bandwidth output shows guarenteed minimum bandwidth per queue



  • 3.  RE: QoS queuing based on DSCP alone?

    Posted Feb 17, 2014 03:25 PM

    It would be helpful if you could post the configuration of all switches.