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authorHarald Welte <laforge@gnumonks.org>2019-02-04 22:42:16 +0100
committerHarald Welte <laforge@gnumonks.org>2019-02-05 14:45:26 +0000
commit9e276081db33694ddb50d0cd1e90dc8e6f80035d (patch)
tree5d69c166351f86b0f4dc5621a6f4397a391e3d96
parent57658ecdc74b7072c05cca6c2bc931f23b1460f6 (diff)
manual: It's not "A over SCCP" but "BSSAP over SCCP"
In GSM specs, the entire interface between two elements is designated with some letter, like the A interface between BSC and MSC. The interface uses a variety of protocols stacked on each other. In the specific case of A, there is no "A" on top of SCCP, but there's "BSSAP" on top of SCCP. This is followed somewhat un-orthodox by 3GPP, as "A over IP" is a violation of that principle. It should have been called "A utilizing IP", "A based on IP", "A with IP" or something the like. In any case, at no point do the specs ever claim that "A" is stacked on top of SCCP, so let's fix this. Change-Id: Ieb0d8f6c71debe1234aff343a994c2096326da1b
-rw-r--r--doc/manuals/chapters/overview.adoc28
1 files changed, 14 insertions, 14 deletions
diff --git a/doc/manuals/chapters/overview.adoc b/doc/manuals/chapters/overview.adoc
index 9b619fb..d3deb27 100644
--- a/doc/manuals/chapters/overview.adoc
+++ b/doc/manuals/chapters/overview.adoc
@@ -38,20 +38,20 @@ OsmoBSC implements a sub-set of the GSM A interface as specified in TS 08.08
Osmocom offers two variants of the 'A' interface's protocol stacking:
-- 'A/SCCPlite'
-- 'A/SCCP/M3UA'
+- 'BSSAP/SCCPlite'
+- 'BSSAP/SCCP/M3UA'
-Traditionally, OsmoBSC only implemented the A/SCCPlite protocol, but since a
+Traditionally, OsmoBSC only implemented the BSSAP/SCCPlite protocol, but since a
proper M3UA implementation is available from 'libosmo-sigtran'
-('libosmo-sccp.git'), the stock OsmoBSC now supports only A/SCCP/M3UA. (The
+('libosmo-sccp.git'), the stock OsmoBSC now supports only BSSAP/SCCP/M3UA. (The
idea is that SCCPlite support may be added to libosmo-sigtran at some point
in the future, after which the new `osmo-bsc` would support both variants of
the A interface.)
-The difference between an A/SCCPlite and A/SCCP/M3UA is illustrated in
+The difference between an BSSAP/SCCPlite and BSSAP/SCCP/M3UA is illustrated in
<<fig-sccplite>> and <<fig-sccp-m3ua>>.
-===== A/SCCPlite
+===== BSSAP/SCCPlite
Unlike classic A interface implementations for E1 interfacs,
`osmo-bsc-sccplite` implements a variant of encapsulating the A interface over
@@ -60,12 +60,12 @@ communicated over TCP. The audio channels are mapped to RTP streams.
This protocol stacking is sometimes called "SCCPlite".
-At the time of writing, if you would like to use the old A/SCCPlite protocol,
+At the time of writing, if you would like to use the old BSSAP/SCCPlite protocol,
look for binary packages named `osmo-bsc-sccplite`, or compile `osmo-bsc` from
the 'openbsc.git' repository.
[[fig-sccplite]]
-.`osmo-bsc-sccplite` operation using 'A/SCCPlite'
+.`osmo-bsc-sccplite` operation using 'BSSAP/SCCPlite'
[graphviz]
----
digraph G {
@@ -81,24 +81,24 @@ digraph G {
{MS0,MS1}->BTS0 [label="Um"];
{MS2,MS3}->BTS1 [label="Um"];
{BTS0,BTS1}->BSC [label="Abis\nTCP\nIP"];
- BSC->MSC [label="A\nSCCP\nTCP\nIP"];
+ BSC->MSC [label="BSSAP\nSCCP\nTCP\nIP"];
}
----
-===== A/SCCP/M3UA
+===== BSSAP/SCCP/M3UA
The default OsmoBSC's A interface uses the M3UA variant of SIGTRAN protocol
stacking:
|=====
-|A
+|BSSAP
|SCCP
|M3UA
|SCTP
|IP
|=====
-To use the now-default A/SCCP/M3UA protocol, look for binary packages named
+To use the now-default BSSAP/SCCP/M3UA protocol, look for binary packages named
`osmo-bsc`, or compile `osmo-bsc` from the 'osmo-bsc.git' repository. It is
recommended to use the M3UA variant, which is required to operate with OsmoMSC.
@@ -106,7 +106,7 @@ To route SCCP/M3UA messages between OsmoBSC and and MSC, an STP instance like
OsmoSTP is required.
[[fig-sccp-m3ua]]
-.`osmo-bsc` operation using 'A/SCCP/M3UA'
+.`osmo-bsc` operation using 'BSSAP/SCCP/M3UA'
[graphviz]
----
digraph G {
@@ -123,7 +123,7 @@ digraph G {
{MS0,MS1}->BTS0 [label="Um"];
{MS2,MS3}->BTS1 [label="Um"];
{BTS0,BTS1}->BSC [label="Abis\nTCP\nIP"];
- BSC->STP->MSC [label="A\nSCCP\nM3UA\nSCTP\nIP"];
+ BSC->STP->MSC [label="BSSAP\nSCCP\nM3UA\nSCTP\nIP"];
}
----