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Document osmux use in Abis interface 

Related: SYS#5987
Change-Id: Ic02d379f35f29f633d0fb14da3597481a0b8b8ba
This commit is contained in:
Pau Espin 2022-09-14 14:14:19 +02:00
parent 1ab6dbc62a
commit 4c9264e0ba
3 changed files with 106 additions and 0 deletions
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54
common/chapters/osmux/mo_call_osmux_abis.msc Normal file
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@ -0,0 +1,54 @@
# MO-call with Osmux enable on 3GPP AoIP
msc {
hscale=2;
ms [label="MS"], bts [label="OsmoBTS"], bsc[label="OsmoBSC"], mgw_bsc[label="OsmoMGW(bsc)"], m_sc[label="MSC"], mgw_msc[label="OsmoMGW(msc)"];
bsc <- m_sc [label="BSSMAP RESET (with extension IE: Osmux Support)"];
bsc -> m_sc [label="BSSMAP RESET ACK (with extension IE: Osmux Support)"];
...;
ms box mgw_msc [label="We assume a SDCCH is already established"];
...;
ms -> bsc [label="DTAP CM Service Request"];
bsc -> m_sc [label="Complete Layer 3 Information DTAP CM Service Request"];
# Allocate MGW/MSC Osmux endpoint
m_sc -> mgw_msc [label="MGCP CRCX rtpbridge/*@mgw, X-Osmux: *"];
mgw_msc box mgw_msc [label="Bind to MGW-local RTP Port (5000)\nAllocate new endpoint 1"];
mgw_msc -> m_sc [label="MGCP CRCX rtpbridge/1@mgw OK (MGW:5000)"];
bsc <- m_sc [label="BSSAP ASSGN REQ"];
bts <- bsc [label="RSL CHAN ACT"];
bts -> bsc [label="RSL CHAN ACT ACK"];
ms <- bsc [label="Assignment Command"];
ms -> bsc [label="Assignment Complete"];
...;
# connect BTS RTP with BSC-MGW RTP
bsc -> mgw_bsc [label="MGCP CRCX rtpbridge/*@mgw, X-Osmux: *"];
mgw_bsc box mgw_bsc [label="Bind to MGW-local Osmux Port (1984)\n\nAllocate new endpoint 2, MGW's local CID 5"];
bsc <- mgw_bsc [label="MGCP CRCX rtpbridge/2@mgw OK (MGW:1984, X-Osmux: 5)"];
bts <- bsc [label="IPA CRCX (Extension IE Osmux-CID 5)"];
bts box bts [label="Bind to BTS-local Osmux Port (1985), Allocate new BTS's local CID 7"];
bts -> bsc [label="IPA CRCX ACK (BTS:1985, Extension IE Osmux-CID 7)"];
bsc -> mgw_bsc [label="MGCP MDCX rtpbridge/2@mgw (BTS:1985, X-Osmux: 7)"];
mgw_bsc box mgw_bsc [label="\nConnect to BTS:1985 MGW's remote CID 7"];
bsc <- mgw_bsc [label="MGCP CRCX rtpbridge/2@mgw OK (MGW:1984, X-Osmux: 5)"];
...;
mgw_bsc <- bsc [label="MGCP CRCX rtpbridge/2@mgw (MSC:5000)"];
mgw_bsc box mgw_bsc [label="Bind to MGW-local RTP Port (2000)\nConnect to MSC:5000"];
mgw_bsc -> bsc [label="MGCP CRCX rtpbridge/2@mgw OK (MGW:2000)"];
...;
bsc -> m_sc [label="BSSAP ASSGN CMPL (3GPP AoIP MGW:2000)"];
m_sc box m_sc [label="Connect remote RTP to MGW addr from ASSGN CMPL"];
m_sc -> mgw_msc [label="MGCP MDCX rtpbridge/1@mgw (MGW:2000)"];
m_sc <- mgw_msc [label="MGCP MDCX rtpbridge/1@mgw OK"];
...;
mgw_bsc <=> mgw_msc [label="RTP Audio MGW:2000 MSC:5000"];
bts <=> mgw_bsc [label="Osmux Audio BTS:1985 MGW:1984, CID(uplink):5, CID(downlink):7"];
ms <=> bts [label="Um Audio (bidirectional)"];
ms <-> m_sc [label="DTAP CC ALERTING"];
}

32
common/chapters/osmux/network_osmux_abis.dot Normal file
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@ -0,0 +1,32 @@
digraph G {
rankdir = LR;
subgraph cluster_RAN {
OsmoBTS1 [label="OsmoBTS"];
OsmoBTS2 [label="OsmoBTS"];
OsmoBSC;
OsmoMGW [label="OsmoMGW\n(for BSC)"];
OsmoBTS1 -> OsmoBSC [label="Abis/IP", dir="both"];
OsmoBTS2 -> OsmoBSC [label="Abis/IP", dir="both"];
OsmoBSC -> OsmoMGW [label="MGCP", dir="both"];
{ rank = same; OsmoBSC; OsmoMGW }
OsmoBTS1 -> OsmoMGW [label="Osmux", dir="both", color=red];
OsmoBTS2 -> OsmoMGW [label="RTP", dir="both"];
label = "RAN";
}
subgraph cluster_CN {
OsmoMGW1 [label="OsmoMGW\n(for MSC)"];
OsmoMSC [label="MSC\ne.g. OsmoMSC"];
Core [label="Other CN Elements"];
OsmoMSC -> Core [label="MAP/ISUP/SIP/GSUP", dir="both"];
OsmoMSC -> OsmoMGW1 [label="MGCP", dir="both"];
{ rank = same; OsmoMSC; OsmoMGW1 }
OsmoMGW -> OsmoMGW1 [label="RTP", dir="both"];
OsmoMGW1 -> Core [label="RTP", dir="both"];
label = "CN";
}
OsmoBSC -> OsmoMSC [label="3GPP AoIP\nvia SIGTRAN/STP", dir="both"];
}

20
common/chapters/osmux/osmux.adoc
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@ -18,6 +18,11 @@ multiplex payload audio streams from call legs between OsmoBSC and OsmoMSC (or
OsmoBSCNAT). The MGW attached those components need of course also be aware of
`Osmux` existence in order to properly set up the audio data plane.
Under some specific circumstances, the operator may decide to set up the network
with a bandwidth-limited (e.g. satellite) link between BTS and BSC. Hence, use of
the `Osmux` protocol is also possible between an Osmux capable BTS (like
OsmoBTS) and OsmoBSC (and its co-located MGW).
=== Osmux and NAT
It is quite usual for satellite based links to use NATs, which means any or both
@ -139,3 +144,18 @@ include::mo_call_osmux_sccplite_nat.msc[]
----
include::mgcp_extension_osmux.adoc[]
=== Abis setup with Osmux
[[fig-network-osmux-aoip]]
.Sample node diagram of Osmux enabled in the Abis interface
[graphviz]
----
include::network_osmux_abis.dot[]
----
.MO-call with Osmux enabled on Abis
[mscgen]
----
include::mo_call_osmux_abis.msc[]
----