daniel has uploaded this change for review. ( https://gerrit.osmocom.org/c/osmo-gsm-manuals/+/42190?usp=email )

Change subject: sigtran-osmocom.adoc: Describe tcap-aware loadshare ......................................................................

sigtran-osmocom.adoc: Describe tcap-aware loadshare

Change-Id: I58979e8f6c5156706b1016069eaaf2801ec9311b Related: OS#5423 --- M common/chapters/sigtran-osmocom.adoc 1 file changed, 18 insertions(+), 0 deletions(-)

git pull ssh://gerrit.osmocom.org:29418/osmo-gsm-manuals refs/changes/90/42190/1

diff --git a/common/chapters/sigtran-osmocom.adoc b/common/chapters/sigtran-osmocom.adoc index 32d03cf..dba73a8 100644 --- a/common/chapters/sigtran-osmocom.adoc +++ b/common/chapters/sigtran-osmocom.adoc @@ -181,6 +181,24 @@ user has no information (nor to worry about ) any "physical" signaling links.

+==== Loadshare with TCAP-aware routing + +A TCAP dialogue consists of multiple messages that depend on each other. +This means that simply load-sharing messages between ASPs will not work +unless the ASPs are able to share state about ongoing TCAP dialogues. + +<<ietf-rfc3868>> states in Ch. A.3.1 that "[...] when TCAP messages are +transported, load sharing is only possible for the first message in a +TCAP dialogue (TC_Begin, TC_Query, TC_Unidirectional). All other TCAP +messages in the same dialogue are sent to the same ASP that was selected +for the first message, unless the ASPs are able to share state and +maintain sequenced delivery." + +The Osmocom SIGTRAN stack supports TCAP-aware routing as described above +in traffic-mode loadshare. Additionally, ASPs connected through IPA/SCCPlite +can use an IPA-based protocol to register ranges of TCAP Ids. This ensures +that a TC_Begin with a given TCAP Id will already be routed to this specific +ASP.

=== Minimal Osmocom SIGTRAN configurations for small networks