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SGSN detach flag

Viewing 13 posts - 1 through 13 (of 13 total)
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  • #57858 Reply
    kamal kotecha
    Guest

    Hi,

    In recent days,we have got issue with some ericson handset…

    1.IMSI get detach from our SGSN & MSC-VLR after inactivity of GPRS for morethan 4 or five hours…

    This happened some after changes have been made in SGSN…
    -We have implemented a feature called “GS” in SGSN,so that subscriber can receive a call during the GPRS is active…

    -We hae enabled an IMEI check in our SGSN..

    But,this can’t be the issue for the same…& the said issue happend after the this implimentation..that’s fact..

    We have set PLU timer 4.0 hours in all BTS..& 4.10 HRS in all MSC

    Who;e GPRS Detach flag is set to 3.5 hours…All these parameters are same as previous..

    And problem occur in recent days…

    Is there any issue in some eriscon handset that they are not able to LU simetiounesly in SGSN & VLR…

    Pls guide if anyone has faced this kind of problem..

    All this issue related to Nokia systems..

    #57859 Reply
    Pan
    Guest

    Dear, kamal kotecha! When network works in NMO1 (Gs-interface between MSC/VLR and SGSN) and MS is in both GPRS-attached and Imsi attached states then Implicit Detach Timer in MSC/VLR must be blocked by MSC/VLR and it must relys on Mobile Reachable Timer in the SGSN (MRT) 3,5???. Also there is no Periodic LA update in this situation – but only Periodic RA Update (PRU). You need to set the correct values for MRT and PRU timer (T3312) in SGSN!!! – not in BSS. See also 23.060 for overall description of combined procedures.

    #57860 Reply
    Pix
    Guest

    Pan,

    Excellent Pan, super useful info. thank you VERY much.

    #57861 Reply
    Pan
    Guest

    Thanks, Pix! But we must wait the response from Kamal. This problem may be deeper than we are thinking 🙂

    #57862 Reply
    Kamal
    Guest

    Hi,

    I we have following values for parameters:

    Can you explain a bit more..?

    READY STATE TIMER……………………………(RDY) 000-44 mmm-ss
    STANDBY STATE TIMER………………………….(STBY) 000-44 mmm-ss
    MS REACHABLE TIMER…………………………..(MSRT) 125-00 mmm-ss
    DETACH TIMER………………………………..(DET) 03-30 hh-mm
    PERIODIC RA UPDATE TIMER……………………..(PRAU) 054-00 mmm-ss
    VLR PERIODIC CLEANING START TIME………………(CTIM) 04:00 hh:mm
    DETACHED SUBSCRIBER STORAGE TIME………………(STT) 000-06 ddd-hh
    UTILISATION RATE DEPENDENT CLEANING……………(UDC) 80 %
    UTILISATION RATE ZERO LIMIT…………………..(UDL) 100 %
    FORCE TO STANDBY ……………………………(FTS) N
    OVERRIDE MS READY STATE TIMER…………………(ORDY) N

    Regards,
    Kamal

    #57863 Reply
    Pan
    Guest

    Hi, Kamal!

    READY STATE TIMER – the time during which the MS is staying in Ready state (performing cell updating) after the packet data transfer is completed.
    STANDBY STATE TIMER – is non-standart timer, see your documentation. May be it is the timer of the forced detach from SGSN to MS.
    MS REACHABLE TIMER – analog of the VLR Implicit Detach Timer in SGSN.
    DETACH TIMER – in SGSN or in VLR? See documentation. Probably Implicit Detach Timer in VLR.
    PERIODIC RA UPDATE TIMER – analog of GSM Periodic LA Update timer in GPRS.
    VLR PERIODIC CLEANING START TIME – see documentation. Probably – the start time of the VLR periodic cleaning (may be purging) after meeting some conditions (like STT, UDC below).
    DETACHED SUBSCRIBER STORAGE TIME – see documentation. Probably – the time after which the detached subscriber can be deleted from VLR after meeting condition below (UDC).
    UTILISATION RATE DEPENDENT CLEANING – see documentation. Probably, condition which cause VLR periodic cleaning above.
    UTILISATION RATE ZERO LIMIT – see documentation.
    FORCE TO STANDBY – the feature in SGSN, allowing the SGSN to reset the Ready Timer in MS and force it go to Standby (Yes/No).
    OVERRIDE MS READY STATE TIMER – see documentation. Probably, deactivation Ready timer in MS (Yes/No).

    #57864 Reply
    kamal
    Guest

    Ya,but I just wanted to know that which timer will affect for the issu mentioned below..?

    #57865 Reply
    Pan
    Guest

    Kamal! Could you answer the questions:
    DETACH TIMER – in SGSN or in VLR? If SGSN then what is it’s meaning?
    DETACHED SUBSCRIBER STORAGE TIME – in VLR or SGSN?
    UTILISATION RATE DEPENDENT CLEANING – in VLR or SGSN?

    #57866 Reply
    kamal
    Guest

    I have mentioned all below para of SGSN only…

    Detach Timer:It will enable right after MS ends the GPRS seassion..
    But,only if ,always online state is not activated..

    VLR PERIODIC CLEANING START TIME:
    It mean on the mentioned time(here 4o’clock morning),VLR will remove the IMSI whose Detach time has exceded the timer limit..

    Detach Sub storage time:While,SGSN will still store the data of sub till this time..

    My question is which timer I need to change after all these changes have been made..?

    Regards,
    Kamal

    #57867 Reply
    Pan
    Guest

    Kamal!
    1)You said “I have mentioned all below para of SGSN only…” But VLR PERIODIC CLEANING START TIME parametr concerns VLR only, isn’t it?
    2)Is Detach Timer resets, if MS performs Periodic RA Updatig only when Detach Timer is running?
    3)Can you do a tests with suspect Ericsson mobile – switch on, GPRS attach+IMSI attach and wait while IMSI detach will occurs (without establishment GPRS sessions and voice call). Is it occured in VLR only, SGSN only or both SGSN and VLR? Exact time expired after switch on?

    #57868 Reply
    kamal
    Guest

    ya,all the parameters are SGSN parameters..

    VLR cleaning is also timer given is SGSN…

    According to me,this para come in picture only after enabling GS..Otherwise SGSN will always thnks that the IMSI get detached has been removed from VLR..

    Detach timer resets only when someone try to access GPRS…after the session is closed,again it rolls over…

    In case of Always online mode,it never trigger..

    Case:
    Person is having Ericson handset,gets detach during night hours..When he tries to access web,suddenly he receives lots of messages of missed calls..(He has a missed call alert facility)

    This happens after no activity of call or GPRS & during night hours only…(probably..)

    No such case have been seen in nokia handsets(victim has tried both..)

    We are working on other ericson handsets…

    By the way,r u nokia guy..?

    Regards,
    Kamal

    #57869 Reply
    Pan
    Guest

    hi, Kamal!
    I am thinking that most Nokia mobiles (when switching on) not perform Combined Attach and stay in GMM Idle (GPRS Detached) state on default. But I don’t know about others.
    On your place, I would try to do as follows:
    1)take the suspect mobile and switch it on;
    2)then check out the subscriber status in SGSN (GPRS Attach/detach?) and VLR (Imsi attach/detach?).
    3)If both flags are attached then wait without making any voice or data activities..It is very desirably to observe the signalling exchange concerning that subscriber on Gb- (e.g. Periodic RA Update, Detach message from SGSN etc.) and Gs-(e.g. Imsi Detach Indication etc.) interfaces.
    4) If for example you will find out that after Detach timer expiry (3,5 h) in SGSN IMSI is detached also in VLR then more likely than not that your SGSN have abnormal behavior.
    p.s. I am not working with Nokia equipment (with the exclusion of my Nokia handset:)
    B.R.

    #57870 Reply
    ask
    Guest

    We are facing lot of IntraSGSN RAU failure with most of the causes being implicit detach timer further giving ( Periodic/intra RAU for unknown subscriber). What could be the reason for this.

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