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BSC: Add series of message sequence charts about MGCP handling 

Change-Id: Id5948677d23a58ce112b57f91bea953a93baab4c
This commit is contained in:
Harald Welte 2017-05-31 21:22:42 +02:00 committed by Neels Hofmeyr
parent b75422f9d4
commit f1d4251461
7 changed files with 353 additions and 1 deletions
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6
doc/manuals/Makefile
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@ -15,13 +15,14 @@ docbooktotypes = pdf
# htmlcss =
TOPDIR := ..
ASCIIDOCS := osmobsc-usermanual osmux-reference
ASCIIDOCS := osmobsc-usermanual osmux-reference aoip-mgw-options
include $(TOPDIR)/build/Makefile.asciidoc.inc
include $(TOPDIR)/build/Makefile.inc
osmobsc-usermanual.pdf: chapters/*.adoc
osmux-reference.pdf: osmux-reference.adoc
aoip-mgw-options.pdf: aoip-mgw-options.adoc
clean:
-rm -rf $(cleanfiles)
@ -29,6 +30,9 @@ clean:
-rm osmobsc-usermanual__*.svg
-rm osmobsc-usermanual*.check
-rm osmux-reference*.check
-rm aoip-mgw-options*.png
-rm aoip-mgw-options*.svg
-rm aoip-mgw-options*.check
gen-bsc-vty-docbook: FORCE
$(call command,xsltproc -o generated/combined1.xml \

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doc/manuals/aoip-mgw-options-docinfo.xml Normal file
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@ -0,0 +1,47 @@
<revhistory>
<revision>
<revnumber>0.1</revnumber>
<date>31 May 2017</date>
<authorinitials>Harald Welte</authorinitials>
<revremark>
Initial version of the proposal for internal discussion.
</revremark>
</revision>
</revhistory>
<authorgroup>
<author>
<firstname>Harald</firstname>
<surname>Welte</surname>
<email>hwelte@sysmocom.de</email>
<authorinitials>HW</authorinitials>
<affiliation>
<shortaffil>sysmocom</shortaffil>
<orgname>sysmocom - s.f.m.c. GmbH</orgname>
<jobtitle>Managing Director</jobtitle>
</affiliation>
</author>
</authorgroup>
<copyright>
<year>2017</year>
<holder>sysmocom - s.f.m.c. GmbH</holder>
</copyright>
<legalnotice>
<para>
Permission is granted to copy, distribute and/or modify this
document under the terms of the GNU Free Documentation License,
Version 1.3 or any later version published by the Free Software
Foundation; with the Invariant Sections being just 'Foreword',
'Acknowledgements' and 'Preface', with no Front-Cover Texts,
and no Back-Cover Texts. A copy of the license is included in
the section entitled "GNU Free Documentation License".
</para>
<para>
The Asciidoc source code of this manual can be found at
<ulink url="http://git.osmocom.org/osmo-gsm-manuals/">
http://git.osmocom.org/osmo-gsm-manuals/
</ulink>
</para>
</legalnotice>

77
doc/manuals/aoip-mgw-options.adoc Normal file
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@ -0,0 +1,77 @@
= OsmoBSC A / SCCPlite / 3GPP AoIP Options
== Introduction
This document serves as a paper to illustrate the different
configurations of OsmoBSC in terms of integration with BTSs and MSCs.
The document should accompany us in the 2017 development cycle which
includes the _death of the NITB_, i.e. the move away from OsmoNITB to
having OsmoBSC in all configurations, whether with a
proprietary/external MSC or with OsmoMSC.
Particular attention is spent on the user plane, including aspects
such as
* user plane transport address handling
* use of MGCP (Media Gateway Control Protocol)
* the (required) evolution of `osmo-bsc_mgcp`
* not loosing classic TDM (E1/T1) BTS support when moving from
OsmoNITB to split OsmoBSC + OsmoMSC setup
== Overview
=== Classic GSM RAN with E1 based Abis and E1 A
This configuration was actually never supported by OpenBSC, as E1 BTS
support was so far for NITB only, but not for OsmoBSC.
[mscgen]
----
include::mgw/classic-bsc.msc[]
----
=== OsmoBSC 2010-2017: IPA-style A over SCCPlite
This configuration was introduced as early as 2010 in OpenBSC. It
allowed the use of IP based BTSs (ip.access nanoBTS as well as all the
OsmoBTS supported BTS models) in combination with third-party MSCs
implementing a pre-standard, proprietary way of transporting the A
interface over IP at a time where the 3GPP specifications only allowed
classic TDM transport.
[mscgen]
----
include::mgw/osmo-bsc-old-sccplite.msc[]
----
=== OsmoBSC 2017+: 3GPP AoIP + Abis/IP
Release 7 of 3GPP included an official specification on how an
interoperable A-over-IP (AoIP) interface shall look like.
As more modern MSCs at operators tend to favor implementing 3GPP AoIP
rather than the proprietary SCCPlite based A interface, it becomes
neccessary for OsmoBSC to support this.
At the same time, for compatibility reasons, the classic SCCPlite
support shall be kept, if possible with reasonable effort.
[mscgen]
----
include::mgw/osmo-bsc-new-mgw.msc[]
----
=== OsmoBSC 2017+: 3GPP AoIP + Abis/E1
Since OsmoNITB will soon be deprecated, we will use OsmoBSC in all
Osmocom GSM ntework setups, requiring the support for classic E1/T1
based BTSs from OsmoBSC.
[mscgen]
----
include::mgw/osmo-bsc-new-mgw-e1.msc[]
----

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# MO Call on a classic E1 Abis BTS with classic E1 A BSC
# not actually supported by OsmoBSC (nor planned), for refrence only
msc {
hscale=2;
ms [label="MS"], bts [label="E1 BTS"], bsc[label="OsmoBSC"], trau[label="TRAU"], m_sc[label="MSC"];
ms box m_sc [label="We assume a SDCCH is already established"];
...;
ms -> m_sc [label="DTAP CC SETUP"];
ms <- m_sc [label="DTAP CC CALL PROCEEDING"];
bsc <- m_sc [label="BSSAP ASSGN REQ"];
bsc box m_sc [label="E1 TS for PCM specified by CIC"];
bts <- bsc [label="RSL CHAN ACT"];
bts -> bsc [label="RSL CHAN ACT ACK"];
bts box bsc [label="E1 TS + 16k sub-slot configured for given lchan"];
ms <-> bsc [label="Assignment"];
bsc -> m_sc [label="BSSAP ASSGN CMPL"];
...;
trau <- m_sc [label="PCM Audio in full E1 slot"];
bts <- trau [label="A-bis TRAU frames on 16k sub-slot"];
...;
ms <- m_sc [label="DTAP CC CONNECT"];
ms -> m_sc [label="DTAP CC CONNECT ACK"];
trau <-> m_sc [label="PCM Audio in full E1 slot"];
bts <-> trau [label="A-bis TRAU frames on 16k sub-slot"];
--- [label="Voice Call in Progress"];
ms <- m_sc [label="DTAP CC DISCONNET"];
ms <- m_sc [label="DTAP CC RELEASE"];
ms <- m_sc [label="DTAP CC RELEASE COMPL"];
...;
bsc <- m_sc [label="BSSMAP CLEAR CMD"];
bsc -> m_sc [label="BSSMAP CLEAR COMPL"];
bsc <- m_sc [label="SCCP RLSD"];
bsc -> m_sc [label="SCCP RLC"];
}

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# MO-Call with E1 BTS + OsmoBSC with true 3GPP AoIP (planned
# osmo-bsc_mgcp has to be extended to true MGW functionality!
msc {
hscale=2;
ms [label="MS"], bts [label="E1 BTS"], bsc[label="OsmoBSC"], mgcp[label="osmo-bsc_mgcp"], m_sc[label="MSC"];
ms box m_sc [label="We assume a SDCCH is already established"];
...;
ms -> m_sc [label="DTAP CC SETUP"];
ms <- m_sc [label="DTAP CC CALL PROCEEDING"];
m_sc box m_sc [label="Bind arbitrary local port (4000)"];
bsc <- m_sc [label="BSSAP ASSGN REQ (3GPP AoIP MSC:4000)"];
bts <- bsc [label="RSL CHAN ACT"];
bts -> bsc [label="RSL CHAN ACT ACK"];
ms <-> bsc [label="Assignment"];
...;
mgcp <- bsc [label="MGCP CRCX ts1/ss2@abis (MSC:4000)"];
mgcp box mgcp [label="Bind to MGW-local RTP Port (3000)\nConnect to MSC:4000"];
mgcp -> bsc [label="MGCP CRCX ts1/ss2@a OK (MGW:3000)"];
...;
bsc -> m_sc [label="BSSAP ASSGN CMPL (3GPP AoIP MGW:3000)"];
m_sc box m_sc [label="Connect remote RTP to MGW addr from ASSGN CMPL"];
...;
mgcp <=> m_sc [label="RTP Audio MGW:3000 MSC:4000"];
bts <=> mgcp [label="TRAU Frame Audio (E1 TS1 SS2)"];
ms <=> bts [label="Um Audio (bidirectional)"];
ms <-> m_sc [label="DTAP CC ALERTING"];
...;
ms <- m_sc [label="DTAP CC CONNECT"];
ms -> m_sc [label="DTAP CC CONNECT ACK"];
--- [label="Voice Call in Progress"];
ms <- m_sc [label="DTAP CC DISCONNET"];
ms <- m_sc [label="DTAP CC RELEASE"];
ms <- m_sc [label="DTAP CC RELEASE COMPL"];
...;
bsc <- m_sc [label="BSSMAP CLEAR CMD"];
bsc -> m_sc [label="BSSMAP CLEAR COMPL"];
bsc <- m_sc [label="SCCP RLSD"];
bsc -> m_sc [label="SCCP RLC"];
...;
mgcp <- bsc [label="MGCP DLCX ts1/ss2@a"];
mgcp box mgcp [label="Release MSC-facing local RTP port (3000)"];
mgcp -> bsc [label="MGCP DLCX ts1/ss2@a OK"];
}

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# MO-Call with OsmoBTS + OsmoBSC with true 3GPP AoIP (planned)
msc {
hscale=2;
ms [label="MS"], bts [label="OsmoBTS"], bsc[label="OsmoBSC"], mgcp[label="osmo-bsc_mgcp"], m_sc[label="MSC"];
ms box m_sc [label="We assume a SDCCH is already established"];
...;
ms -> m_sc [label="DTAP CC SETUP"];
ms <- m_sc [label="DTAP CC CALL PROCEEDING"];
m_sc box m_sc [label="Bind arbitrary local port (4000)"];
bsc <- m_sc [label="BSSAP ASSGN REQ (3GPP AoIP MSC:4000)"];
bts <- bsc [label="RSL CHAN ACT"];
bts -> bsc [label="RSL CHAN ACT ACK"];
ms <-> bsc [label="Assignment"];
...;
# connect BTS RTP with BSC-MGW RTP
bts <- bsc [label="IPA CRCX"];
bts box bts [label="Bind to BTS-local RTP Port (1000)"];
bts -> bsc [label="IPA CRCX ACK (BTS:1000)"];
bsc -> mgcp [label="MGCP CRCX 2@abis (BTS:1000)"];
mgcp box mgcp [label="Bind to MGW-local RTP Port (2000)\nConnect to BTS:1000"];
bsc <- mgcp [label="MGCP CRCX 2@abis OK (MGW:2000)"];
bts <- bsc [label="IPA MDCX 2@abis (MGW:2000)"];
bts box bts [label="Connect RTP socket to remote (MGW) RTP Port"];
bts -> bsc [label="IPA MDCX 2@abis ACK"];
#bsc -> mgcp [label="MGCP MDCX 2@abis (optional)"];
#bsc <- mgcp [label="MGCP MDCX 2@abis OK (optional)"];
...;
mgcp <- bsc [label="MGCP CRCX 1@a (MSC:4000)"];
mgcp box mgcp [label="Bind to MGW-local RTP Port (3000)\nConnect to MSC:4000"];
mgcp -> bsc [label="MGCP CRCX 1@a OK (MGW:3000)"];
...;
bsc -> m_sc [label="BSSAP ASSGN CMPL (3GPP AoIP MGW:3000)"];
m_sc box m_sc [label="Connect remote RTP to MGW addr from ASSGN CMPL"];
...;
mgcp <=> m_sc [label="RTP Audio MGW:3000 MSC:4000"];
bts <=> mgcp [label="RTP Audio BTS:1000 MGW:2000"];
ms <=> bts [label="Um Audio (bidirectional)"];
ms <-> m_sc [label="DTAP CC ALERTING"];
...;
ms <- m_sc [label="DTAP CC CONNECT"];
ms -> m_sc [label="DTAP CC CONNECT ACK"];
--- [label="Voice Call in Progress"];
ms <- m_sc [label="DTAP CC DISCONNET"];
ms <- m_sc [label="DTAP CC RELEASE"];
ms <- m_sc [label="DTAP CC RELEASE COMPL"];
...;
bsc <- m_sc [label="BSSMAP CLEAR CMD"];
bsc -> m_sc [label="BSSMAP CLEAR COMPL"];
bsc <- m_sc [label="SCCP RLSD"];
bsc -> m_sc [label="SCCP RLC"];
...;
mgcp <- bsc [label="MGCP DLCX 1@a"];
mgcp box mgcp [label="Release MSC-facing local RTP port (3000)"];
mgcp -> bsc [label="MGCP DLCX 1@a OK"];
bsc -> mgcp [label="MGCP DLCX 2@abis"];
mgcp box mgcp [label="Release BTS-facing local RTP port (2000)"];
bsc <- mgcp [label="MGCP DLCX 2@abis OK"];
bts <- bsc [label="IPA DLCX"];
bts box bts [label="Release BTS-local RTP port (1000)"];
bts -> bsc [label="IPA DLCX OK"];
}

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# MO-Call with OsmoBTS + OsmoBSC using A/IP with IPA/SCCPlite
# Supported since 2010 using osmo-bsc + osmo-bsc_nat
msc {
hscale=2;
ms [label="MS"], bts [label="OsmoBTS"], bsc[label="OsmoBSC"], mgcp[label="osmo-bsc_mgcp"], m_sc[label="MSC"];
ms box m_sc [label="We assume a SDCCH is already established"];
...;
ms -> m_sc [label="DTAP CC SETUP"];
ms <- m_sc [label="DTAP CC CALL PROCEEDING"];
bsc <- m_sc [label="BSSAP ASSGN REQ"];
bts <- bsc [label="RSL CHAN ACT"];
bts -> bsc [label="RSL CHAN ACT ACK"];
ms <-> bsc [label="Assignment"];
bsc -> m_sc [label="BSSAP ASSGN CMPL"];
...;
bts <- bsc [label="IPA CRCX"];
bts box bts [label="Bind to BSC-local RTP Port"];
bts -> bsc [label="IPA CRCX ACK"];
bts <- bsc [label="IPA MDCX"];
bts box bts [label="Connect RTP socket to remote (bsc_mgcp) RTP Port"];
bts -> bsc [label="IPA MDCX ACK"];
mgcp <- m_sc [label="MGCP CRCX"];
mgcp box mgcp [label="Bind to BTS-local RTP Port"];
mgcp -> m_sc [label="MGCP CRCX OK"];
mgcp <- m_sc [label="MGCP MDCX (recvonly) "];
mgcp box mgcp [label="Connect RTP socket to remote (MSC) RTP Port"];
mgcp -> m_sc [label="MGCP MDCX OK"];
mgcp <= m_sc [label="RTP Audio"];
bts <= mgcp [label="RTP Audio"];
ms <= bts [label="Um Audio (unidirectional)"];
ms <- m_sc [label="DTAP CC ALERTING"];
...;
mgcp <- m_sc [label="MGCP MDCX (sndrecv) "];
mgcp box mgcp [label="Switch to bi-directional audio"];
mgcp -> m_sc [label="MGCP MDCX OK"];
mgcp <=> m_sc [label="RTP Audio"];
bts <=> mgcp [label="RTP Audio"];
ms <=> bts [label="Um Audio (bidirectional)"];
...;
ms <- m_sc [label="DTAP CC CONNECT"];
ms -> m_sc [label="DTAP CC CONNECT ACK"];
mgcp <- m_sc [label="MGCP MDCX (sndrecv) "];
mgcp box mgcp [label="Why?"];
mgcp -> m_sc [label="MGCP MDCX OK"];
--- [label="Voice Call in Progress"];
ms <- m_sc [label="DTAP CC DISCONNET"];
ms <- m_sc [label="DTAP CC RELEASE"];
ms <- m_sc [label="DTAP CC RELEASE COMPL"];
...;
bsc <- m_sc [label="BSSMAP CLEAR CMD"];
bsc -> m_sc [label="BSSMAP CLEAR COMPL"];
bsc <- m_sc [label="SCCP RLSD"];
bsc -> m_sc [label="SCCP RLC"];
...;
mgcp <- m_sc [label="MGCP DLCX"];
mgcp box mgcp [label="Release local RTP port"];
mgcp -> m_sc [label="MGCP DLCX OK"];
}