Cisco Cisco ASR 5000
Direct Tunnelling for the S4-SGSN
▀ How It Works
▄ SGSN Administration Guide, StarOS Release 18
Scenario
Old
RNC
RNC
Status
Old
RNC
RNC
RAB
Old RNC
DT Status
DT Status
PLMN
Change
Change
NEW RNC
DT Status
DT Status
S-GW
Change
Change
SGSN Action
Intra
RAU
RAU
Not
Present
Present
No
RAB
RAB
Not
Supported
Supported
No
Supported
No
No RAB establishment with new RNC.
Modify Bearer Request to S-GW with DTF set
and no user FTEID.
Modify Bearer Request to S-GW with DTF set
and no user FTEID.
Intra
RAU
RAU
Present
No
RAB
RAB
Not
Supported
Supported
No
Supported
No
Same as above.
Intra
RAU
RAU
Present
Some
RABs
RABs
Not
Supported
Supported
Do not
care
care
Supported
No
Only the present RABs are established. MBR
sent to S-GW with the bearers with RABs to
be modified and the rest to be released. The
bearers without RABs will be deactivated post
RAU. If PLMN changed then MBR will carry
the new PLMN ID.Modify Bearer.
sent to S-GW with the bearers with RABs to
be modified and the rest to be released. The
bearers without RABs will be deactivated post
RAU. If PLMN changed then MBR will carry
the new PLMN ID.Modify Bearer.
Intra
RAU
RAU
Not
Present
Present
No
RAB
RAB
Not
Supported
Supported
Yes
Supported
No
No RAB establishment with new RNC. MBR
is sent with only PLMN change. SGSN will
page / Service req / establish RABs when a
downlink data notification is received.
is sent with only PLMN change. SGSN will
page / Service req / establish RABs when a
downlink data notification is received.
Intra
RAU
RAU
Present
No
RAB
RAB
Not
Supported
Supported
Yes
Supported
No
Same as above.
Intra RAU: New RNC does not support Direct Tunnel. No SGW relocation
Intra
RAU
RAU
Not
Present
Present
No
RAB
RAB
Supported
Do not
care
care
Not
Supported
Supported
No
No RAB establishment with new RNC. SGSN
sends Modify Bearer Request to S-GW with
S4U TEID. If there is change in PLMN ID,
then new PLMN ID will be carried.
sends Modify Bearer Request to S-GW with
S4U TEID. If there is change in PLMN ID,
then new PLMN ID will be carried.
Intra
RAU
RAU
Present
No
RAB
RAB
Supported
Do not
care
care
No
Supported
Supported
No
Same as above.
Intra
RAU
RAU
Present
Some
RABs
RABs
Supported
Do not
care
care
Not
supported
supported
No
Only the present RABs are established. MBR
sent to S-GW with all bearers having S4U
TEID. If there is change in PLMN ID, the new
PLMN ID will be carried.
sent to S-GW with all bearers having S4U
TEID. If there is change in PLMN ID, the new
PLMN ID will be carried.
Routing Area Update with S-GW Change
In a Routing Area Update with an S-GW change, the SGSN sends a Create Session Request with DTF flag set and no
user plane FTEID. In its Create Session Response,. the S-GW sends an S12U FTEID which is forwarded to the RNC via
a RAB Assignment Request.
user plane FTEID. In its Create Session Response,. the S-GW sends an S12U FTEID which is forwarded to the RNC via
a RAB Assignment Request.
The SGSN sends the RNC FTEID received in the RAB Assignment Response to the S-GW in a Modify Bearer Request.
There are many scenarios to consider during Intra SGSN RAU.
There are many scenarios to consider during Intra SGSN RAU.