Ingress buffers on 4000 series oversubscribed gigabit line cards

Discussion in 'Cisco' started by Peter Yardley, Nov 11, 2003.

  1. Hi,

    Does anybody know the size and configuration and in fact if there are
    any packet buffers for incoming data on the oversubscribed 24/48 port
    4000 series gigabit copper line cards. These cards seem to use the
    lemans stub asic to provide port access but I can't find any other

    Thanks in advance,

    _--_|\ Peter Yardley |
    / \ Network & UNIX Systems Manager |
    \_.--._* Faculty of Engineering, | Ph: +61 2 9514-2358
    v University of Technology, Sydney.| Fax: +61 2 9514-2435
    Peter Yardley, Nov 11, 2003
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  2. Peter Yardley

    Chris Thomas Guest

    Yes, the blades in question run the Lemans ASIC. The ports are
    overbooked 4:1 (24p) or 8:1 (48p). They are mapped in groups of 4
    (8). If you drive any group of 4 (8) at more than 1 Gb/s and exceed
    the input buffer depth, packets are dropped. You can determine the
    switch port to Lemans mapping with the undocumented command
    show platform portmap interface gi 3/1

    You can see overbooking congestion with
    show interface gi 3/1 counters all
    Look at the TX and RX pause frames. Do the command for all the ports
    on a given Lemans. RX pause frames incrementing means the switch
    input (ie, overbooking) is congested.

    Don't forget to keep in mind that what is significant is the ratio of
    pause (slow down) frames to total frames. The occurrance of
    occasional pause frames isn't a big deal. If you have a few really
    busy ports, try to use every fourth or eight port for them, and fill
    in will less busy links.

    /Chris, UCLA
    Chris Thomas, Nov 11, 2003
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  3. Thanks for the info Chris, however I was primarily interested in the
    buffer sizes on the blade itself to get an idea how quickly the links
    get stalled.

    Peter Yardley, Nov 14, 2003
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