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
Do not
care
care
Supported
Yes
Send CSR request to new S-GW with DTF flag
but no S4U / S12U FTEID. S-GW sends its
S12U TEID that SGSN stores as part of our
DP's remote TEID. SGSN will not initiate any
MBR request to S-GW since no RABs are
established with new RNC. If S-GW
subsequently gets downlink data, SGSN gets
DDN and establishes RABs and sends MBR.
but no S4U / S12U FTEID. S-GW sends its
S12U TEID that SGSN stores as part of our
DP's remote TEID. SGSN will not initiate any
MBR request to S-GW since no RABs are
established with new RNC. If S-GW
subsequently gets downlink data, SGSN gets
DDN and establishes RABs and sends MBR.
Intra
RAU
RAU
present
No
RAB
RAB
Not
Supported
Supported
Do not
care
care
Supported
Yes
Same as above.
Intra
RAU
RAU
Present
Some
RABs
RABs
Not
SUpported
SUpported
Do not
care
care
Supported
Yes
Send CSR request to new S-GW with DTF flag
but no S4U / S12U FTEID. S-GW sends its
S12U TEID. RABs that are present will be
established with new RNC and MBR will be
initiated only with those RABs that are present
and the rest as bearers to be removed.
but no S4U / S12U FTEID. S-GW sends its
S12U TEID. RABs that are present will be
established with new RNC and MBR will be
initiated only with those RABs that are present
and the rest as bearers to be removed.
Intra RAU: New RNC does not support Direct Tunnel. SGW relocation
Intra
RAU
RAU
Not
Present
Present
No
RAB
RAB
Supported
Do not
care
care
Not
Supported
Supported
Yes
CSR request without DTF flag and with S4U
FTEID.
FTEID.
Intra
RAU
RAU
Present
No
RAB
RAB
Supported
Do not
care
care
Not
Supported
Supported
Yes
CSR request without DTF flag and with S4U
FTEID.
FTEID.
Intra
RAU
RAU
Present
Some
rABs
rABs
Supported
Do not
care
care
Not
Supported
Supported
Yes
CSR request without DTF flag and with S4U
FTEID. No deactivation of PDPs.
FTEID. No deactivation of PDPs.
Intra SRNS with S-GW Change
In Intra SRNS (Serving Radio Network Subsystem) with S-GW change, the SGSN sends a Create Session Request with
DTF flag set and no user plane FTEID. The Create Session Response from the new S-GW contains the SGW S12U
FTEID which the SGSN forwards to the Target RNC in a Relocation Request.
DTF flag set and no user plane FTEID. The Create Session Response from the new S-GW contains the SGW S12U
FTEID which the SGSN forwards to the Target RNC in a Relocation Request.
The SGSN sends the RNC S12U FTEID to the new S-GW in a Modify Bearer Request.