[Openbts-discuss] CKSN clarification

Alexander Chemeris alexander.chemeris at gmail.com
Fri Apr 20 15:44:41 UTC 2012

On Fri, Apr 20, 2012 at 19:33, Alexander Chemeris
<alexander.chemeris at gmail.com> wrote:
> Max,
> On Fri, Apr 20, 2012 at 19:09, Max <Max.Suraev at fairwaves.ru> wrote:
>> - what is CKSN IEI and how do I calculate\use it?
> IEI is a Information Element Identifier, which is a part of TLV-coded
> (Type-Length-Value) Information Elements (IEs). In other words, IEI
> represents type (T) of the data payload which follows it. TLV is an
> encoding used in most of the classical GSM protocols. I don't recall
> where it is described in the Standard, but here is a nice paper which
> you easily find on Google which describes ciphering and described TLV
> structure as well (section 6.1.2):
> http://www.cs.ru.nl/~fabianbr/scriptie.pdf

But as Sylvain mentioned, in almost all cases CKSN is sent as "V" IE,
so no IEI is needed. The only place where you seem to need CKSN IEI is
in GPRS Mobility Management Messages "Authentication and ciphering
request" (section 9.4.9), where it CKSN is sent as "TV" IE. And there
in the table left column you see the IEI value "8-", meaning that it's

Alexander Chemeris.
CEO, Fairwaves LLC / ООО УмРадио

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