Osmo-bscosmo-bscAoverIP » History » Version 2
laforge, 02/19/2016 10:48 PM
| 1 | 1 | laforge | |
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| 2 | 2 | laforge | h1. 3GPP compliange A over IP interface |
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| 5 | 1 | laforge | In more recent versions of the A interface specification (used to be GSM TS 08.08, now is 3GPP TS 48.008), |
| 6 | the A protocol is officially specified over IP as an alternative bearer. This is a great alternative |
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| 7 | to the slightly hackish existing implementations using SCCPLite (SCCP in an IPA multiplex) and MGCP for |
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| 8 | mapping of CICs to RTP port numbers. |
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| 10 | 2 | laforge | [[osmo-bsc]] does not yet support this standardized version of A-over-IP. |
| 11 | 1 | laforge | |
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| 13 | 2 | laforge | h2. Differences from classic A interface |
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| 16 | 1 | laforge | The major differences from classic A interface (over E1 or SCCPLite+RTCP) are: |
| 17 | * BSSAP ASSIGNMENT COMMAND includes |
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| 18 | 2 | laforge | * no CIC! |
| 19 | * MSC-side IP/port |
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| 20 | * list of MSC preferred speech codecs |
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| 21 | * call identifier (random 4bytes of MSC) |
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| 22 | 1 | laforge | * BSSAP ASSIGNMENT COMPLETE includes |
| 23 | 2 | laforge | * no CIC! |
| 24 | * BSC-side IP/port |
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| 25 | * chosen speech codec |
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| 26 | 1 | laforge | * BSSAP RESET IP RESOURCE |
| 27 | 2 | laforge | * replacement for (RESET RESOURCE with CIC) |
| 28 | * MSC sends list of call identifiers which are to be reset |
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| 29 | 1 | laforge | |
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| 31 | 2 | laforge | h2. Required changes to osmo-bsc for [[AoIP]] support |
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| 34 | 1 | laforge | Architecturally, the bsc-mgcp and any media related handling can be completely replaced by |
| 35 | * ASSIGNMENT COMMAND handling |
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| 36 | 2 | laforge | * checking if [[AoIP]] transport address IEI is present and distinguishing old A and [[AoIP]] based on that |
| 37 | * storing call identifier IE in connection |
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| 38 | * sending IPA_CRCX to the BTS |
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| 39 | * saving BTS side IP/Port from IPA_CRCX_ACK |
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| 40 | * sending IPA MDCX to the BTS, using MSC-side IP/port |
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| 41 | * selecting codec based on MSC preferred speech codec list IE |
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| 42 | 1 | laforge | * ASSIGNMENT COMPLETE handling |
| 43 | 2 | laforge | * including IP/port from IPA_CRCX_ACK |
| 44 | * including selected/chosen speech codec |
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| 45 | 1 | laforge | * RESET IP RESOURCE handling |
| 46 | 2 | laforge | * iterate over list of call identifiers in msg |
| 47 | * delete/reset any connection (and lchan, ...) for given call identifier |
