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Routing area Update

Viewing 15 posts - 1 through 15 (of 19 total)
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  • #61521 Reply
    Hellsing
    Guest

    Hi all, i’m new @ Core staff and would like to know if Routing Area update is presented on Gn interface?? because we swapped Gn traffic over IP MPLS backbone and suddenly RAU decrease, is this normal? Thanks in advance

    #61522 Reply
    Pix
    Guest

    Hello Hellsing,

    “Gn” interface, between SGSN and GGSN ? I cannot find any valid reason why it would behave in such a way. It is not normal, and should not even be possible ! 🙂

    Have you done any other change ? For example, activation of the Gs interface, or actvation of LA/RA combined update ? Change of LAC planning, or RAC planning, on the radio side ?

    Cheers,
    pix

    #61523 Reply
    Hellsing
    Guest

    Changing LAC/RAC @ Radio side i think yes, another detail that we have Two SGSN and we finish migration from old SGSN last weekend but the problem just apperead after swap on IP/MPLS backbone and i think it’s not a possbile reason for this problem.

    could the problem be related with Inter SGSN RA?

    #61524 Reply
    pix
    Guest

    hellsing,

    yes, if there is only one SGSN instead of 2, then you should see less inter-SGSN RA updates. But the number of RAU (inter+intra) should be the same as before.

    The RAU is a procedure starter by the MS. The MS doesn’t care about your Gn interface… it just cares about the RA in the new cell : same or different than before ?
    If different, then a RAU is done.

    I’m not familiar with interSGSN RAU : are they going through the GGSN ? I thought the SGSN would contact the other SGSN directly… (to be verified !)

    #61525 Reply
    Hellsing
    Guest

    Whats exactly the relation betwenn periodic RA and normal RA? shoul the number be the same?

    #61526 Reply
    pix
    Guest

    periodic RA : after expiry of a timer, the MS is forced to perform a RA update, even if it didn’t move

    normal RA : the MS has moved and changed RA, physically.

    #61527 Reply
    Hellsing
    Guest

    so i think the only reason that periodic RA change is LAC/RAC redesign, or timer change? isn’t it

    #61528 Reply
    Pix
    Guest

    Periodic RA increase is due to timer change only.

    Check out 23.060
    ————————
    6.2.2.
    The Periodic RA Update Timer function monitors the periodic RA update procedure in the MS. The length of the periodic RA update timer is sent in the Routeing Area Update Accept or Attach Accept message. The periodic RA update timer is unique within an RA. Upon expiry of the periodic RA update timer, the MS shall start a periodic routeing area update procedure.
    ——————

    and also 24.008
    ————————-
    4.7.5.1
    Periodic routing area updating is used to periodically notify the availability of the MS to the network. The value of the update type IE in the ROUTING AREA UPDATE REQUEST message shall indicate “periodic updating”. The procedure is controlled in the MS by timer T3312. When timer T3312 expires, the periodic routing area updating procedure is started. Start and reset of timer T3312 is described in subclause 4.7.2.2.
    —————————

    So the timer is called T3312 ! Default value is 54mn.
    The value of this timer is used if the network does not indicate another value in a GMM signalling procedure. For example in the Routing Area Update Accept : the SGSN can indicate a different timer.

    Cheers,
    Pix

    #61529 Reply
    Hellsing
    Guest

    Thanks pix, but really i’m a little bit confused about this, as in our case no LAC/RAC change was done and no timer change and RAU and periodic RAU decreased. any other suggestions?

    #61530 Reply
    Hellsing
    Guest

    In the same context, i take a Gn (Inter SGSN) Trace with wireshark to investigate about Inter SGSN RAU failure, how can i find Inter SGSN RAU message among my trace?

    #61531 Reply
    pix
    Guest

    hellsing,

    you should read the 3GPP documents I pointed out earlier ^^

    3GPP 23.060
    http://www.3gpp.org/ftp/Specs/html-info/23060.htm

    6.9.1.2.2 Inter SGSN Routeing Area Update

    The new SGSN sends SGSN Context Request (old RAI, TLLI, old P TMSI Signature, New SGSN Address) to the old SGSN to get the MM and PDP contexts for the MS.

    #61532 Reply
    Hellsing
    Guest

    Thanks pix , i’m on it now.

    #61533 Reply
    Hellsing
    Guest

    ok for the whole procedure but in order to investigate about Inter SGSN RAU failure (Nokia SGSN), what are the ways to investigate? otherwise what are the IP frames in the trace that could be helpful?

    #61534 Reply
    kamal kotecha
    Guest

    Hi,

    You must have same RAC in unique PAPU..Otherwise it will cause failure & 2955 will be triggered..

    Ultimately,RAC planning should be done in such as way that same RAC remain unique between PAPU…you should use same RAC in bsc such a way that you can manage these BSC in same PAPU..Thats all..!

    #61535 Reply
    thakur
    Guest

    How to analysis call fail in 3G

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