| Daniel Willmann | 376aa9e | 2020-09-24 20:23:34 +0200 | [diff] [blame] | 1 | [[chapter_details]] |
| 2 | == Proxy details |
| 3 | |
| 4 | === BVC handling |
| 5 | |
| 6 | This section describes in more detail how BVCs are handled in OsmoGbProxy |
| 7 | |
| 8 | If a BSS connects to OsmoGbProxy while the SGSN is not available it will |
| 9 | acknowledge the BVC RESET on the signalling BVC, but ignore other messages |
| 10 | (especially any PTP BVC RESET). |
| 11 | |
| 12 | .BSS connects to OsmoGbProxy |
| 13 | [mscgen] |
| 14 | ---- |
| 15 | msc { |
| 16 | hscale="1.8"; |
| 17 | bss1 [label="BSS1"], bss2 [label="BSS2"], gbproxy [label="GbProxy"], sgsn [label="SGSN"]; |
| 18 | bss1 <=> gbproxy [label="NS link available"]; |
| 19 | bss1 => gbproxy [label="BVC RESET (BVCI=0)"]; |
| 20 | gbproxy => bss1 [label="BVC RESET ACK"]; |
| 21 | bss1 -x gbproxy [label="PTP BVC RESET (ignored)"]; |
| 22 | } |
| 23 | ---- |
| 24 | |
| 25 | As soon as the SGSN is reachable through NS OsmoGbProxy will send a BVC RESET |
| 26 | to the signalling BVC towards the SGSN. After that completes it will reset the |
| 27 | signalling BVC of all BSS connections. At this point the BSS will send a BVC |
| 28 | RESET for its PTP BVCs which will be forwarded to the SGSN, similarly the PTP |
| 29 | BVC RESET ACK from the SGSN will be sent back to the BSS. |
| 30 | |
| 31 | .SGSN connection to OsmoGbProxy |
| 32 | [mscgen] |
| 33 | ---- |
| 34 | msc { |
| 35 | hscale="1.8"; |
| 36 | bss1 [label="BSS1"], bss2 [label="BSS2"], gbproxy [label="GbProxy"], sgsn [label="SGSN"]; |
| 37 | gbproxy <=> sgsn [label="NS link available"]; |
| 38 | gbproxy => sgsn [label="BVC RESET (BVCI=0)"]; |
| 39 | sgsn => gbproxy [label="BVC RESET ACK"]; |
| 40 | |
| 41 | gbproxy => bss1 [label="BVC RESET (BVCI=0)"]; |
| 42 | bss1 => gbproxy [label="BVC RESET ACK"]; |
| 43 | bss1 box bss1 [label="PTP BVCs need to be reset"]; |
| 44 | bss1 => gbproxy [label="PTP BVC RESET (BVCI=x)"]; |
| 45 | gbproxy => sgsn [label="PTP BVC RESET (BVCI=x)"]; |
| 46 | sgsn => gbproxy [label="PTP BVC RESET ACK (BVCI=x)"]; |
| 47 | gbproxy => bss1 [label="PTP BVC RESET ACK (BVCI=x)"]; |
| 48 | bss2 <=> sgsn [label="BVCI x established"]; |
| 49 | } |
| 50 | ---- |
| 51 | |
| 52 | The communication on the PTP BVC will then be forwarded between the BSS and the |
| 53 | SGSN. |
| 54 | |
| 55 | If a BSS connects while the SGSN is up the PTP BVC RESET will directly be |
| 56 | forwarded. |
| 57 | |
| 58 | .BSS connects to OsmoGbProxy |
| 59 | [mscgen] |
| 60 | ---- |
| 61 | msc { |
| 62 | hscale="1.8"; |
| 63 | bss1 [label="BSS1"], bss2 [label="BSS2"], gbproxy [label="GbProxy"], sgsn [label="SGSN"]; |
| 64 | bss2 <=> gbproxy [label="NS link available"]; |
| 65 | bss2 => gbproxy [label="BVC RESET (BVCI=0)"]; |
| 66 | gbproxy => bss2 [label="BVC RESET ACK"]; |
| 67 | bss2 => gbproxy [label="PTP BVC RESET (BVCI=y)"]; |
| 68 | gbproxy => sgsn [label="PTP BVC RESET (BVCI=y)"]; |
| 69 | sgsn => gbproxy [label="PTP BVC RESET ACK (BVCI=y)"]; |
| 70 | gbproxy => bss2 [label="PTP BVC RESET ACK (BVCI=y)"]; |
| 71 | bss2 <=> sgsn [label="BVCI y established"]; |
| 72 | } |
| 73 | ---- |
| 74 | |
| 75 | If OsmoGbProxy looses the connection to the SGSN it will reset the signalling |
| 76 | BVC of all BSS connections. This ensures that the BSS will not send traffic |
| 77 | over a PTP BVC before its reset procedure has been completed. |
| 78 | |
| 79 | .SGSN connection fails |
| 80 | [mscgen] |
| 81 | ---- |
| 82 | msc { |
| 83 | hscale="1.8"; |
| 84 | bss1 [label="BSS1"], bss2 [label="BSS2"], gbproxy [label="GbProxy"], sgsn [label="SGSN"]; |
| 85 | gbproxy <=> sgsn [label="NS link fails"]; |
| 86 | gbproxy => bss1 [label="BVC RESET (BVCI=0)"]; |
| 87 | gbproxy => bss2 [label="BVC RESET (BVCI=0)"]; |
| 88 | } |
| 89 | ---- |
| 90 | |
| 91 | When the connection to the SGSN is eventually restored the signalling BVC |
| 92 | between OsmoGbProxy and SGSN will be reset. |
| 93 | |
| 94 | After that completes OsmoGbProxy will reset the signalling BVC on all BSS NS |
| 95 | connections and forward the PTP BVC RESET messages. |
| 96 | |
| 97 | .SGSN connection restored |
| 98 | [mscgen] |
| 99 | ---- |
| 100 | msc { |
| 101 | hscale="1.8"; |
| 102 | bss1 [label="BSS1"], bss2 [label="BSS2"], gbproxy [label="GbProxy"], sgsn [label="SGSN"]; |
| 103 | gbproxy <=> sgsn [label="NS link available"]; |
| 104 | gbproxy => sgsn [label="BVC RESET (BVCI=0)"]; |
| 105 | sgsn => gbproxy [label="BVC RESET ACK"]; |
| 106 | gbproxy => bss1 [label="BVC RESET (BVCI=0)"]; |
| 107 | bss1 => gbproxy [label="BVC RESET ACK"]; |
| 108 | bss1 box bss1 [label="PTP BVCs need to be reset"]; |
| 109 | gbproxy => bss2 [label="BVC RESET (BVCI=0)"]; |
| 110 | bss2 => gbproxy [label="BVC RESET ACK"]; |
| 111 | bss2 box bss2 [label="PTP BVCs need to be reset"]; |
| 112 | } |
| 113 | ---- |