Osmo-bscosmo-bscAoverIP » History » Version 2
laforge, 02/19/2016 10:48 PM
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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. |
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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 |