diff options
| -rw-r--r-- | doc/manuals/chapters/gbproxy-details.adoc | 113 | ||||
| -rw-r--r-- | doc/manuals/chapters/gbproxy-overview.adoc | 11 | ||||
| -rw-r--r-- | doc/manuals/osmogbproxy-usermanual.adoc | 2 |
3 files changed, 121 insertions, 5 deletions
diff --git a/doc/manuals/chapters/gbproxy-details.adoc b/doc/manuals/chapters/gbproxy-details.adoc new file mode 100644 index 00000000..f77d40cf --- /dev/null +++ b/doc/manuals/chapters/gbproxy-details.adoc @@ -0,0 +1,113 @@ +[[chapter_details]] +== Proxy details + +=== BVC handling + +This section describes in more detail how BVCs are handled in OsmoGbProxy + +If a BSS connects to OsmoGbProxy while the SGSN is not available it will +acknowledge the BVC RESET on the signalling BVC, but ignore other messages +(especially any PTP BVC RESET). + +.BSS connects to OsmoGbProxy +[mscgen] +---- +msc { + hscale="1.8"; + bss1 [label="BSS1"], bss2 [label="BSS2"], gbproxy [label="GbProxy"], sgsn [label="SGSN"]; + bss1 <=> gbproxy [label="NS link available"]; + bss1 => gbproxy [label="BVC RESET (BVCI=0)"]; + gbproxy => bss1 [label="BVC RESET ACK"]; + bss1 -x gbproxy [label="PTP BVC RESET (ignored)"]; +} +---- + +As soon as the SGSN is reachable through NS OsmoGbProxy will send a BVC RESET +to the signalling BVC towards the SGSN. After that completes it will reset the +signalling BVC of all BSS connections. At this point the BSS will send a BVC +RESET for its PTP BVCs which will be forwarded to the SGSN, similarly the PTP +BVC RESET ACK from the SGSN will be sent back to the BSS. + +.SGSN connection to OsmoGbProxy +[mscgen] +---- +msc { + hscale="1.8"; + bss1 [label="BSS1"], bss2 [label="BSS2"], gbproxy [label="GbProxy"], sgsn [label="SGSN"]; + gbproxy <=> sgsn [label="NS link available"]; + gbproxy => sgsn [label="BVC RESET (BVCI=0)"]; + sgsn => gbproxy [label="BVC RESET ACK"]; + + gbproxy => bss1 [label="BVC RESET (BVCI=0)"]; + bss1 => gbproxy [label="BVC RESET ACK"]; + bss1 box bss1 [label="PTP BVCs need to be reset"]; + bss1 => gbproxy [label="PTP BVC RESET (BVCI=x)"]; + gbproxy => sgsn [label="PTP BVC RESET (BVCI=x)"]; + sgsn => gbproxy [label="PTP BVC RESET ACK (BVCI=x)"]; + gbproxy => bss1 [label="PTP BVC RESET ACK (BVCI=x)"]; + bss2 <=> sgsn [label="BVCI x established"]; +} +---- + +The communication on the PTP BVC will then be forwarded between the BSS and the +SGSN. + +If a BSS connects while the SGSN is up the PTP BVC RESET will directly be +forwarded. + +.BSS connects to OsmoGbProxy +[mscgen] +---- +msc { + hscale="1.8"; + bss1 [label="BSS1"], bss2 [label="BSS2"], gbproxy [label="GbProxy"], sgsn [label="SGSN"]; + bss2 <=> gbproxy [label="NS link available"]; + bss2 => gbproxy [label="BVC RESET (BVCI=0)"]; + gbproxy => bss2 [label="BVC RESET ACK"]; + bss2 => gbproxy [label="PTP BVC RESET (BVCI=y)"]; + gbproxy => sgsn [label="PTP BVC RESET (BVCI=y)"]; + sgsn => gbproxy [label="PTP BVC RESET ACK (BVCI=y)"]; + gbproxy => bss2 [label="PTP BVC RESET ACK (BVCI=y)"]; + bss2 <=> sgsn [label="BVCI y established"]; +} +---- + +If OsmoGbProxy looses the connection to the SGSN it will reset the signalling +BVC of all BSS connections. This ensures that the BSS will not send traffic +over a PTP BVC before its reset procedure has been completed. + +.SGSN connection fails +[mscgen] +---- +msc { + hscale="1.8"; + bss1 [label="BSS1"], bss2 [label="BSS2"], gbproxy [label="GbProxy"], sgsn [label="SGSN"]; + gbproxy <=> sgsn [label="NS link fails"]; + gbproxy => bss1 [label="BVC RESET (BVCI=0)"]; + gbproxy => bss2 [label="BVC RESET (BVCI=0)"]; +} +---- + +When the connection to the SGSN is eventually restored the signalling BVC +between OsmoGbProxy and SGSN will be reset. + +After that completes OsmoGbProxy will reset the signalling BVC on all BSS NS +connections and forward the PTP BVC RESET messages. + +.SGSN connection restored +[mscgen] +---- +msc { + hscale="1.8"; + bss1 [label="BSS1"], bss2 [label="BSS2"], gbproxy [label="GbProxy"], sgsn [label="SGSN"]; + gbproxy <=> sgsn [label="NS link available"]; + gbproxy => sgsn [label="BVC RESET (BVCI=0)"]; + sgsn => gbproxy [label="BVC RESET ACK"]; + gbproxy => bss1 [label="BVC RESET (BVCI=0)"]; + bss1 => gbproxy [label="BVC RESET ACK"]; + bss1 box bss1 [label="PTP BVCs need to be reset"]; + gbproxy => bss2 [label="BVC RESET (BVCI=0)"]; + bss2 => gbproxy [label="BVC RESET ACK"]; + bss2 box bss2 [label="PTP BVCs need to be reset"]; +} +---- diff --git a/doc/manuals/chapters/gbproxy-overview.adoc b/doc/manuals/chapters/gbproxy-overview.adoc index 580afae6..1564157a 100644 --- a/doc/manuals/chapters/gbproxy-overview.adoc +++ b/doc/manuals/chapters/gbproxy-overview.adoc @@ -1,18 +1,18 @@ [[chapter_overview]] == Overview -=== About OsmoGbPROXY +=== About OsmoGbProxy -OsmoGbPROXY is the Osmocom proxy for the 3GPP Gb interface. The Gb +OsmoGbProxy is the Osmocom proxy for the 3GPP Gb interface. The Gb interface is defined by 3GPP as the protocol between the BSS and the SGSN inside the 2G/2.5G/2.75G packet switched network domain. As Osmocom implements a BTS-colocated PCU, there are potentially many Gb interface connections between all those many PCUs in the network and the SGSN. This can be cumbersome to configure/maintain at the -SGSN sine. +SGSN side. -OsmoGbPROXY aggregates many PCU-facing Gb connections into one Gb +OsmoGbProxy aggregates many PCU-facing Gb connections into one Gb connection to the SGSN. This is achieved by * maintaining sepaate NS-VCs on the PCU side and on the SGSN side @@ -21,11 +21,12 @@ connection to the SGSN. This is achieved by * having some special handling for the signaling BVC (BVCI=0) which is shared among all the PCUs connected to the proxy + === Data Model ==== gbproxy_config -This contains the parsed configuration of the OsmoGbPROXY. +This contains the parsed configuration of the OsmoGbProxy. ==== gproxy_peer diff --git a/doc/manuals/osmogbproxy-usermanual.adoc b/doc/manuals/osmogbproxy-usermanual.adoc index c4e0b9d0..c93ebecf 100644 --- a/doc/manuals/osmogbproxy-usermanual.adoc +++ b/doc/manuals/osmogbproxy-usermanual.adoc @@ -9,6 +9,8 @@ include::./common/chapters/preface.adoc[] include::{srcdir}/chapters/gbproxy-overview.adoc[] +include::{srcdir}/chapters/gbproxy-details.adoc[] + include::{srcdir}/chapters/gbproxy-running.adoc[] include::{srcdir}/chapters/gbproxy-control.adoc[] |