catalyst 3750 and UDP traffic policing ?

Discussion in 'Cisco' started by RJ45, May 8, 2004.

  1. RJ45

    RJ45 Guest

    Hello,
    I noticed that traffic policing with C3750 (EMI) works only with
    TCP Streams and not UDP streams.
    anyone got the same result ?

    thanks

    Rick
     
    RJ45, May 8, 2004
    #1
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  2. In article <>,
    RJ45 <> wrote:
    :I noticed that traffic policing with C3750 (EMI) works only with
    :TCP Streams and not UDP streams.
    :anyone got the same result ?

    If I remember correctly, traffic policing works in part by dropping
    packets and expecting the other end to "notice" and start transport-level
    decongestion procedures. TCP has decongestion procedures based upon
    timeouts and window-sizes. UDP has no decongestion procedures: for
    UDP you can't inherently tell the difference between the packet never having
    been sent or it having been lost or it having been dropped for rate
    control reasons. So UDP doesn't inherently know enough to slow down.

    --
    Look out, there are llamas!
     
    Walter Roberson, May 8, 2004
    #2
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  3. Hello, Walter!
    You wrote on 8 May 2004 18:23:18 GMT:

    WR> :I noticed that traffic policing with C3750 (EMI) works only
    WR> with :TCP Streams and not UDP streams.
    WR> :anyone got the same result ?

    WR> If I remember correctly, traffic policing works in part by
    WR> dropping packets and expecting the other end to "notice" and
    WR> start transport-level decongestion procedures.

    That would be Random Early Discard, or Random Early Detection which is
    politically correct form of the former one :)

    With best regards,
    Andrey.
     
    Andrey Tarasov, May 8, 2004
    #3
  4. Hello, RJ45!
    You wrote on Sat, 8 May 2004 18:00:16 +0000 (UTC):

    R> Hello,
    R> I noticed that traffic policing with C3750 (EMI) works only
    R> with
    R> TCP Streams and not UDP streams.
    R> anyone got the same result ?

    Normally TCP traffic is overpoliced so you might get very different results for
    TCP and UDP even with policer working properly. How did you do the test and what
    was the results?

    With best regards,
    Andrey.
     
    Andrey Tarasov, May 8, 2004
    #4
  5. RJ45

    RJ45 Guest

    I did the test with iperf.
    with TCP streams I got good results, with UDP
    streams traffic is not shaped, is not policed.
    if I configure a policy rule of 10Mbit/s
    with TCP streams it works, with UDP streams it goes 100MBit/s
    without policing it at 10Mbit/s.

    my tests are 2 100Mbit/s machines connected to 2 different Layer 3 IP
    ports of the switch.

    Maybe traffic policy cannot work with UDP streams as Walter explained?

    thanks

    Rick

    On 2004-05-08, Andrey Tarasov <> wrote:
    > Hello, RJ45!
    > You wrote on Sat, 8 May 2004 18:00:16 +0000 (UTC):
    >
    > R> Hello,
    > R> I noticed that traffic policing with C3750 (EMI) works only
    > R> with
    > R> TCP Streams and not UDP streams.
    > R> anyone got the same result ?
    >
    > Normally TCP traffic is overpoliced so you might get very different results for
    > TCP and UDP even with policer working properly. How did you do the test and what
    > was the results?
    >
    > With best regards,
    > Andrey.
    >
     
    RJ45, May 11, 2004
    #5
  6. Hello, RJ45!
    You wrote on Tue, 11 May 2004 13:14:02 +0000 (UTC):


    R> I did the test with iperf.
    R> with TCP streams I got good results, with UDP streams traffic
    R> is not shaped, is not policed.
    R> if I configure a policy rule of 10Mbit/s with TCP streams it
    R> works, with UDP streams it goes 100MBit/s without policing it
    R> at 10Mbit/s.

    R> my tests are 2 100Mbit/s machines connected to 2 different
    R> Layer 3 IP ports of the switch.

    Can you post a config?

    R> Maybe traffic policy cannot work with UDP streams as Walter
    R> explained?

    What Walter mentioned is called RED - random early detect. That doesn't work
    with UDP streams indeed, because those streams are not sensitive to packet drops
    and don't throttle.
    Policer does the same thing to all traffic - either UDP or TCP - it drops (or
    mark) the packets violating configured transmit rate.

    With best regards,
    Andrey.
     
    Andrey Tarasov, May 13, 2004
    #6
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