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High RTT delay

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  • #63859 Reply
    718433
    Guest

    HI,

    We are using Huawei BSC and SGSN in of NSN in mumbai.We are getting RTT delay of 40 ms when we are pinging from BSC to SGSN.THis is ok.But when we are connecting LAptop to GPRS and than pinging ftp server than we are getting 600 ms RTT delay.Can any one help???

    #63860 Reply
    pix
    Guest

    hi,

    are you talking about the 1st ping ? or the “subsequent” pings ?
    in the 1st ping, the delay is due to the TBF establishment.
    Next pings are carried over the same TBF : there is no need for reestablishment. (the TBF is kept “open” for a while, so that the MS can reuse it quickly)

    try typing the command
    ping iii.iii.iii.iii -l 0 -n 10

    this will send 10 packets with a size = 0 bytes
    of course you can increase the size if you want. In any case, the MS will always send four bursts at least (that is the size of the radio block), that’s 4 TDMA frames = 4*4.615 = 20ms
    With 4 bursts, depending which coding scheme is used, a certain amount of load can be sent.
    But if you send ping with size of 10,000 bytes, this will take a much longer time to transmit 🙂

    Then add the time for TBF establishment, and the time for Abis and ATer-PS resource allocation (the GCH in ALU), and that expains why the first ping takes longer time.

    Next pings should be about 80ms to 100ms(as far as i recall)

    don’t hesitate to post the result of your ping messages !

    regards
    pix

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