Frame Relay BE excess burst size

Discussion in 'Cisco' started by Chris T., May 4, 2005.

  1. Chris T.

    Chris T. Guest

    How do I calculate the excess bust size ( BE ) for frame relay?
    I am not sure what to set BE to, I have looked around on the internet and do
    not see a recommended setting or a way to calculate it.

    I know how to calculate BC:
    BC = TC x CIR
    12,800 = .02 x 640,000

    Thank You,

    Chris T., May 4, 2005
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  2. Chris T.

    Jonathan Guest

    Speed of link - CIR = Total Be

    Speed of link * Tc = Burst Size

    Burst Size is the total amount of data you can send in Tc

    Jonathan, May 5, 2005
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  3. Chris T.


    Sep 30, 2010
    Likes Received:
    I will give an example how to calculate FR BE, BC etc and traffic-shaping methodologies.

    Scenario: DS3 (45Mpbs port), provisioned though for 15Mbps traffic in DLCI, throttle down to 10Mbps in an event
    of congestion with an interval of Tc=50 ms, with traffic shapping. Work out values for FR traffic-Shaping (2 mthds):

    cir=15000000, mincir=10000000, bc=CIR*Tc=750000, be+bc=max port bandwidth in one Tc which is 45Mbps (but in 50ms).
    Hence, 45Mbps in 1 Sec or 2250000bps in 50 ms. So, Be=Max-Bc or 2250000-750000=1500000.

    a) method

    map-class frame-relay FR_SHAPE
    frame-relay cir 15000000
    frame-relay bc 750000
    frame-relay be 1500000
    frame-relay mincir 10000000
    frame-relay adaptive-shaping becn

    interface Serial2/0
    no ip address
    encapsulation frame-relay
    no keepalive
    no fair-queue
    frame-relay class FR_SHAPE
    frame-relay traffic-shaping

    b) method

    policy-map FRTS
    class class-default
    shape average 15000000 750000 1500000
    shape adaptive 10000000

    interface Serial2/0
    bandwidth 45000
    frame-relay interface-dlci 101
    service-policy out FRTS
    apikou, Sep 30, 2010
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