http://www.linkedin.com/answers/technology/information-technology/telecommunications/TCH_ITS_TCI/350373-28185065
Regarding your APN selection clarification question: There's two features at play here: 

1) The Basic APN selection algorithm says, that if the mobile defines no APN _AND_ there is a wildcard (*) in the subscriber's HLR subscription, then the SGSN shall use the default APN defined in the SGSN. This should work the same way on all vendor's SGSNs as it should follow the specs (as one of the answers stated). 

However, if the subscriber defines an APN that doesn't match the subscription or the subscriber doesn't define an APN at all and the HLR has no wildcard APN for the user then the APN selection would fail and the user would get a PDP context activation failure. 

2) For these reasons, you have the APN override feature in your SGSN. It allows the SGSN to try to "guess" at which APN the user would like in the case of a terminal misconfiguration (typo in the APN for example). In this case, the SGSN will take the SGSN's own default APN or the user's APN if such is defined in the HLR. 

Note that this feature is there to help misconfigured mobiles get at least some service and is optional.



On Wed, Jun 29, 2011 at 8:55 AM, John Gitau <jgitau@gmail.com> wrote:
all undefined APN's default to a pre-defined one/

On Tue, Jun 28, 2011 at 8:13 PM, Bernard Mwagiru <bmwagiru@gmail.com> wrote:
> APN override /APN auto-correction.
>
> ./bernard
> sent from my android device.
>
> On Jun 28, 2011 7:46 PM, "Memusi" <tonatech@gmail.com> wrote:
>> apn overwrite
>>
>> On Tue, Jun 28, 2011 at 7:43 PM, James Mutuku <listmutuku@gmail.com>
>> wrote:
>>
>>> been doing this for long. I am not sure how they handle it on their end
>>>
>>> On 6/28/11, Memusi <tonatech@gmail.com> wrote:
>>> > Did you know that you can just configure your apn e.g kubaff and you
>>> > will
>>> > still browse.?
>>> >
>>> > Interesting .Try.
>>> >
>>> > --
>>> > Regards
>>> >
>>> > Memusi
>>> >
>>> > Communication is vital in this century....
>>> >
>>>
>>>
>>> --
>>> Best Regards,
>>> James Mutuku Ndeti
>>> Agile Systems Limited
>>> +254722490994
>>> www.agile.co.ke
>>> www.zetu.co.ke
>>>
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>>> (CRM)system? visit http://www.agile.co.ke/crm.php and find out how our
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>>
>>
>>
>> --
>> Regards
>>
>> Memusi
>>
>> Communication is vital in this century....
>
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--
Regards

Memusi

Communication is vital in this century....