Release Access Bearer Request
After Yesterday post on deletion of session and bearer in MME/SGW, later I am bit confused about Release Access Bearer Request, why again one more message to delete a bearer with a different name "release" :-) . So I have done some research to understand it which I am sharing with you below. Hope it will help you all.
. Release
Access Bearer Request
What
spec 29.274 says:
The
Release Access Bearers Request message shall sent on the S11 interface by the
MME to the SGW as part of the S1
release
procedure.
The
message shall also be sent on the S4 interface by the SGSN to the SGW as part
of the procedures:
-
RAB release using S4
-
Iu Release using S4
-
READY to STANDBY transition within the network
List of RABs
Shall be present on S4 interface
when this message is
used to release a subset of all
active RABs according to
the RAB release procedure.
Several IEs with this type and
instance values shall be
included as necessary to represent
a list of RABs to be
released.
|
23.401 5.3.5 says
The
MME sends a Release Access Bearers Request message to the S-GW that requests
the release of all S1-U bearers for the UE. This message is triggered either by
an S1 Release Request message from the eNodeB, or by another MME event.
The
S-GW releases all eNodeB related information (address and TEIDs) for the UE and
responds with a Release Access Bearers Response message to the MME. Other
elements of the UE's S-GW context are not affected, means MME-HSS and MME-SGW
interface is intact here and S-GW inside it retains the S1-U configuration that
the S-GW allocated for the UE's bearers, SGW only removed the connection
between SGW and serving ENB.
My Understanding:
Release
Access Bearer Request used as part of S1-release procedure, it will remove all
the active bearers (both default and dedicated) temporarily between SGW and ENB
S1-U interface due to user inactivity(or due to some other reason) and session
between S5/S8, S11, S6a will remain intact or you can say it is in preserve
mode(not active). It is done to save some resource of the MME, so that MME can
assign same user plane resource to other users(For network operators radio
resource and user plane S1-U resource is very precious for them). So once UE
context removed then Release Access Bearer Request will remove all the
bearers between SGW and ENB. It is not dependent on any EBI or LBI and spec is
also not telling to include any EBI or LBI value, but it can be vendor
dependent. If you check any network side logs you may not get any IE related to
EBI/LBI in Release Access Bearer Request messages.
After
reading my post, please post your comment below, if still some doubt left in
you ;-)
what are the other MME events that can trigger it, please explain that too.
ReplyDeleteUSer inactivity in what sense, not clear?
uncesna-a Jose Kadlecik Here
ReplyDeleteinasruduf