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Bug #6461

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GSM 04.08 phase 1: Mobile terminated setup messages - octet 3a in case of speech

Added by nt2mku about 2 months ago. Updated about 2 months ago.

Status:
New
Priority:
Low
Assignee:
-
Category:
Call Control
Target version:
-
Start date:
05/22/2024
Due date:
% Done:

0%

Resolution:
Spec Reference:
GSM TS 04.08 v3.13.0

Description

Some early GSM phones implementing phase 1 specification (here: Siemens P1; S/W version 18.06.93 09:58:48) reject mobile terminated calls from OsmoMSC if octet 3a is present in the setup message.

picture326-1.png picture326-2.png
04.08 v3 states octets 3a (and 4-6) shall only be present in case of information transfer capability != speech (10.5.4.4; PDF page 373).

04.08 v4 states: "If the information transfer capability field (octet 3) indicates "speech", octet 3a etc shall be included only if the MS
supports at least one speech version other than: GSM full rate speech version 1; GSM half rate speech version 1." (10.5.4.5.1; PDF page 293)

With reference to Bug#6459 (OsmoBSC), the classmark 1 IE within location update request indicates if the MS is a phase 1 device. This could be an indication to omit octet 3a in encoding outgoing MT setup requests.

Refs:
https://www.3gpp.org/ftp/Specs/archive/04_series/04.08/0408-3d0.zip (GSM TS 04.08 v3.13.0)
https://www.3gpp.org/ftp/Specs/archive/04_series/04.08/0408-3E0.ZIP (GSM TS 04.08 v3.14.0)
https://www.3gpp.org/ftp/Specs/archive/04_series/04.08/0408-4p0.zip (GSM TS 04.08 v4.25.0)

Specification phases (from #6459):

Phase Freeze Date Spec Versions
1 1991 3.X.X
2 October 1995 4.X.X
2+ never 5.x.x; aka R96 and higher

Files

gsmts_0408sv031300p.pdf View gsmts_0408sv031300p.pdf 11.4 MB nt2mku, 05/22/2024 08:37 AM
0408-4p0.pdf View 0408-4p0.pdf 2.71 MB nt2mku, 05/22/2024 09:48 AM
picture326-1.png View picture326-1.png 145 KB nt2mku, 05/22/2024 10:23 AM
picture326-2.png View picture326-2.png 96.9 KB nt2mku, 05/22/2024 10:23 AM
Actions #1

Updated by nt2mku about 2 months ago

Related: https://gerrit.osmocom.org/c/libosmocore/+/36784 - but the encoding should consider the MS specification phase as mentioned above. OsmoMSC could remove all non-phase 1 codec offers for the outgoing call in this case, so octet 3a won't get encoded.

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