Routing

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  • 1.  Poor outbound TCP throughput on 20 mpbs Internet circuit, UDP has no such problem

    Posted 03-27-2012 05:42

    Greetings.

     

    I implemented a 20 mpbs Internet circuit (on a J-series router fe interface) a few months back and have observed a puzzling phenonenon. Performance appears to be asymmetric when TCP is used but not UDP. I'm wondering if COS or something else might resolve this issue. I suspect connection oriented protocols are choking because they are expecting 100 mbps and only getting 20 mpbs... any suggestions are welcomed.

     

    I started testing various ways, both uploads and downloads using scp directly from the router to a site on the Internet and back along with bandwidth speed tests, etc. What I found is that receiving any sort of file or using another protocol like http, etc. I'm getting ~19.8 Mbps throughput however when I transmit a file via any TCP-based protocol I get 60-100 Kbps!

     

    If I blast UDP packets with iperf I'm getting all of it... and with TCP packets very poor again:

     

    C:\temp>iperf -c x.x.x.x -t 20 -u -b 20M
    ------------------------------------------------------------
    Client connecting to x.x.x.x, UDP port 5001
    Sending 1470 byte datagrams
    UDP buffer size: 8.00 KByte (default)
    ------------------------------------------------------------
    [1884] local 10.0.0.95 port 49934 connected with x.x.x.x port 5001
    [ ID] Interval Transfer Bandwidth
    [1884] 0.0-20.0 sec 47.7 MBytes 20.0 Mbits/sec
    [1884] Server Report:
    [1884] 0.0-20.0 sec 43.2 MBytes 18.1 Mbits/sec 1.717 ms 3224/34015 (9.5%)
    [1884] Sent 34015 datagrams

     

    C:\temp>iperf -c x.x.x.x -P 2 -w 128K -t 20
    ------------------------------------------------------------
    Client connecting to x.x.x.x, TCP port 5001
    TCP window size: 128 KByte
    ------------------------------------------------------------
    [1884] local 10.0.0.95 port 50025 connected with x.x.x.x port 5001
    [1868] local 10.0.0.95 port 50026 connected with x.x.x.x port 5001
    [ ID] Interval Transfer Bandwidth
    [1884] 0.0-27.3 sec 304 KBytes 91.1 Kbits/sec
    [1868] 0.0-31.5 sec 632 KBytes 164 Kbits/sec
    [SUM] 0.0-31.5 sec 936 KBytes 243 Kbits/sec

    C:\temp>

     



  • 2.  RE: Poor outbound TCP throughput on 20 mpbs Internet circuit, UDP has no such problem
    Best Answer

    Posted 03-28-2012 05:27

    It appears the carrier (V#@&!0N- can you hear me NOW?) had something awry in their configs.... I've never seen this behavior before so testing a new circuit with both TCP and UDP protocols using iperf is highly recommended.