congesting a back-to-back link on a switch

Discussion in 'Cisco' started by akmann7@gmail.com, Jul 7, 2007.

  1. Guest

    Hello experts,

    Traffic source1 -------- Catalyst1 --------------Catalyst2
    ---------Traffic source 2

    ----------------------------------------Direction of Traffic
    flow ----------------------->>>

    Is there any way to congest the RX link on catalyst2 in above setup.
    Basically I am trying to force the generation of flow control frames
    between catalyst2 and catalyst1. Idea is if catalyst2 gets congested
    on RX side, it will trigger flowcontrol frames to catalyst1 and then
    catalyst1 should react to it.

    I think the only way to congest will be to decrease the RX buffer
    size on
    catalyst2. Does anybody know how to achieve that on a RX port which
    has following capablity....

    GigabitEthernet1/1
    Dot1x: yes
    Model: WS-X6748-SFP
    Type: 1000BaseT
    Speed: 1000
    Duplex: full
    Trunk encap. type: 802.1Q,ISL
    Trunk mode: on,off,desirable,nonegotiate
    Channel: yes
    Broadcast suppression: percentage(0-100)
    Flowcontrol: rx-(off,on,desired),tx-(off,on,desired)
    Membership: static
    Fast Start: yes
    QOS scheduling: rx-(1q8t), tx-(1p3q8t)
    CoS rewrite: yes
    ToS rewrite: yes
    Inline power: no
    SPAN: source/destination
    UDLD yes
    Link Debounce: yes
    Link Debounce Time: no
    Ports on ASIC: "bunch of ports"
    Port-Security: yes

    Any advide will be helpful. Thanks, Akmann
    , Jul 7, 2007
    #1
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  2. stephen Guest

    <> wrote in message
    news:...
    > Hello experts,
    >
    > Traffic source1 -------- Catalyst1 --------------Catalyst2
    > ---------Traffic source 2
    >
    > ----------------------------------------Direction of Traffic
    > flow ----------------------->>>
    >
    > Is there any way to congest the RX link on catalyst2 in above setup.
    > Basically I am trying to force the generation of flow control frames
    > between catalyst2 and catalyst1. Idea is if catalyst2 gets congested
    > on RX side, it will trigger flowcontrol frames to catalyst1 and then
    > catalyst1 should react to it.


    The 6724 card has 20 Gbps full duplex backplane link, and is split into 2 12
    port sections fed by separate chips.

    and if there is a DFC on this blade, then L3 forwarding happens locally, so
    the backplane doesnt get touched for local traffic.
    >
    > I think the only way to congest will be to decrease the RX buffer
    > size on
    > catalyst2. Does anybody know how to achieve that on a RX port which
    > has following capablity....


    reducing the buffer pool would only help if there was more traffic coming in
    that could get out again. Otherwise there is very little in the buffers
    since packets go straight thru to the backplane.

    basically if you want congestion you are going to have to load that and lots
    of other ports with wire speed traffic - preferably using small packets to
    increase the overhead in the backplane.

    >
    > GigabitEthernet1/1
    > Dot1x: yes
    > Model: WS-X6748-SFP
    > Type: 1000BaseT
    > Speed: 1000
    > Duplex: full
    > Trunk encap. type: 802.1Q,ISL
    > Trunk mode: on,off,desirable,nonegotiate
    > Channel: yes
    > Broadcast suppression: percentage(0-100)
    > Flowcontrol: rx-(off,on,desired),tx-(off,on,desired)
    > Membership: static
    > Fast Start: yes
    > QOS scheduling: rx-(1q8t), tx-(1p3q8t)
    > CoS rewrite: yes
    > ToS rewrite: yes
    > Inline power: no
    > SPAN: source/destination
    > UDLD yes
    > Link Debounce: yes
    > Link Debounce Time: no
    > Ports on ASIC: "bunch of ports"
    > Port-Security: yes
    >
    > Any advide will be helpful. Thanks, Akmann


    you need to congest somewhere else unless you have a 15 to 20 port GigE
    traffic generator.....
    >

    --
    Regards

    - replace xyz with ntl
    stephen, Jul 7, 2007
    #2
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