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no-drop buffer space?

jordanperks
Level 1
Level 1

**Edited for clarification

When configuring a no-drop queue it carves out 90240byte buffer space for it. All remaining buffer is assigned to the default class. I cannot find any document that says this specifically, but I am assuming that if that 90KB buffer is full it will use additional buffer space from the default class if available? Is this a correct assumption? If this assumption is incorrect, and 90KB is all it gets, then wouldnt enabling a no-drop queue be detrimental if there is no other traffic on the switch and you assigning no-drop to all traffic?

Maybe I can clarify the question. When configuring a no-drop class, as shown in the table below, it carves out 90.204KB of the available 478KB ingress buffer, for that system class. Does this mean that the no-drop class gets 90.204KB of buffer space and that is the limit or will the ingress buffer use all of the 478 total KB across all other classes in the event there is no other traffic present?

3-21-2013 11-29-22 AM.png

Switch1-5596# show queuing interface

Ethernet1/1 queuing information:

  TX Queuing

    qos-group  sched-type  oper-bandwidth

        0       WRR              5

        3       WRR             95

  RX Queuing

    qos-group 0

    q-size: 350080, HW MTU: 1500 (1500 configured)

    drop-type: drop, xon: 0, xoff: 350080

    Statistics:

        Pkts received over the port             : 0

        Ucast pkts sent to the cross-bar        : 0

        Mcast pkts sent to the cross-bar        : 0

        Ucast pkts received from the cross-bar  : 50435

        Pkts sent to the port                   : 181544

        Pkts discarded on ingress               : 0

        Per-priority-pause status               : Rx (Inactive), Tx (Inactive)

    qos-group 3

    q-size: 90240, HW MTU: 9216 (9216 configured)

    drop-type: no-drop, xon: 17280, xoff: 37120

    Statistics:

        Pkts received over the port             : 83772441

        Ucast pkts sent to the cross-bar        : 83771738

        Mcast pkts sent to the cross-bar        : 703

        Ucast pkts received from the cross-bar  : 320433145

        Pkts sent to the port                   : 320496330

        Pkts discarded on ingress               : 0

        Per-priority-pause status               : Rx (Active), Tx (Inactive)

Message was edited by: Jordan Perks

2 Replies 2

jordanperks
Level 1
Level 1

After some research I have answered my own question. By enabling pause no-drop it has sliced my available buffer from 470KB to 90KB. It now sends TX pause frames out at 37KB and Resume frames at 17KB. It will not use available buffer space in excess of 90.24KB It appears I will need to use a command similar to "pause no-drop buffer-size 442000 pause-threshold 300560 resume-threshold 243100”. My problem now is, what to set all those values to. I wonder what percentage of buffer usage I should have it send pause/resume frames.

DIdyou get past the max buffer issue? For a 5596T which we have the max buffer is 152k, well short of the 480k figure.