Change in osmo-gsm-manuals[master]: cs7-config: Describe special meaning of M3UA routing context '0'

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laforge gerrit-no-reply at lists.osmocom.org
Fri Jan 29 21:15:50 UTC 2021


laforge has submitted this change. ( https://gerrit.osmocom.org/c/osmo-gsm-manuals/+/22528 )

Change subject: cs7-config: Describe special meaning of M3UA routing context '0'
......................................................................

cs7-config: Describe special meaning of M3UA routing context '0'

Osmocom has a special interpretation of the routing-context '0'.

Let's document that.

Change-Id: Iac0bc1e754d04b2e798263bfa029d26376e4e92f
---
M common/chapters/cs7-config.adoc
1 file changed, 26 insertions(+), 0 deletions(-)

Approvals:
  Jenkins Builder: Verified
  pespin: Looks good to me, but someone else must approve
  laforge: Looks good to me, approved



diff --git a/common/chapters/cs7-config.adoc b/common/chapters/cs7-config.adoc
index a0957fd..62e85bb 100644
--- a/common/chapters/cs7-config.adoc
+++ b/common/chapters/cs7-config.adoc
@@ -307,3 +307,29 @@
 routing-key RCONTEXT DPC ssn SSN
 routing-key RCONTEXT DPC si (aal2|bicc|b-isup|h248|isup|sat-isup|sccp|tup) ssn SSN
 ----
+
+==== M3UA without Routing Context IE / Routing Context '0'
+
+As per the M3UA specification, the use of the routing context IE is
+optional as long as there is only one AS within an ASP.  As soon as
+there are multiple different AS within one ASP, the routing context IE
+is mandatory, as it is the only clue to differentiate which of the ASs a
+given message belongs to.
+
+In the Osmocom M3UA implementation, it is generally assumed that a
+routing context IE is always used, for the sake of clarity.
+
+However, the routing context ID of '0' has the special meaning of _do
+not encode a routing context IE on transmit_.
+
+So if you configure an application like OsmoBSC to use routing context
+0, then no routing context IE will be included in outbound M3UA
+messages.
+
+This special interpretation of '0' within the Osmocom M3UA
+implementation however means that we can not represent M3UA with a
+routing context IE that actually contains '0' as a numeric identifier.
+
+So you only have the following options:
+* Using M3UA with routing context (1..N)
+* Using M3UA without routing context (0)

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Gerrit-Project: osmo-gsm-manuals
Gerrit-Branch: master
Gerrit-Change-Id: Iac0bc1e754d04b2e798263bfa029d26376e4e92f
Gerrit-Change-Number: 22528
Gerrit-PatchSet: 1
Gerrit-Owner: laforge <laforge at osmocom.org>
Gerrit-Reviewer: Jenkins Builder
Gerrit-Reviewer: laforge <laforge at osmocom.org>
Gerrit-Reviewer: pespin <pespin at sysmocom.de>
Gerrit-MessageType: merged
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