Section: 4.3.15a.2 SIPTO at the Local Network with stand-alone GW (with S-GW and L-GW collocated) function
Content: SIPTO at the Local Network is achieved using a stand-alone GW (with S-GW and L-GW collocated) residing in the Local Network. A (H)eNB supporting SIPTO at the Local Network with the stand-alone GW includes the Local Home Network ID to the MME in every INITIAL UE MESSAGE, every UPLINK NAS TRANSPORT control message, HANDOVER NOTIFY and PATH SWITCH REQUEST messages. If a SIPTO PDN connection is initiated as an additional subsequent PDN connection, the MME should check if the S-GW is optimal for the user's current location. If it is not, and if the network supports S-GW relocation without being triggered by a mobility event, the MME may decide to perform an MME triggered Serving GW relocation according to clause 5.10.4, when possible (e.g. no other restrictions apply). For SIPTO at the Local Network with a stand-alone GW, the location of the Serving GW may be determined based on the operator policy and user's profile regarding support of SIPTO at Local Network so that: - At attachment to the (H)eNB, a local S-GW can always be selected independent of whether a SIPTO at the Local Network PDN connection is established or not. If mobility is performed to the macro network without having a SIPTO connection, a S-GW relocation can be performed as specified via existing mobility procedures with S-GW relocation. - At attachment to a (H)eNB, a macro S-GW may be allocated for PDN connection in the operator's network. If a new PDN connection is requested by the UE that requires that a local S-GW is selected to provide for SIPTO at the Local Network, S-GW relocation from the macro S-GW to the local S-GW shall be performed as specified in clause 5.10.4. As IP data session continuity for SIPTO at the Local Network PDN connection is not supported in this release of the specification, subsequent to handover completion the (target) MME should disconnect the SIPTO at the Local Network PDN connection with "reactivation requested" cause as specified in clause 5.10.3, unless the Local Home Network ID is not changed. The IP data session should be maintained if the Local Home Network ID is not changed. If the UE has no other PDN connection and the Local Home Network ID is changed, the (target) MME initiates "explicit detach with reattach required" procedure according to clause 5.3.8.3. Upon completion of Tracking Area Update procedure, the (new) MME shall trigger the re-establishment of the SIPTO at the Local Network PDN connection when it detects that the UE has moved away from the (H)eNB and to a (H)eNB with different Local Home Network ID, as specified in clause 5.3.3 and clause 5.3.4. NOTE: It is expected that all MMEs/SGSNs in a PLMN have support for SIPTO at the Local Network where the operator deploys this feature, in order to support mobility procedures. For a mobility event where target MME/SGSN does not support SIPTO at the Local Network, the handling of PDN deactivation for SIPTO at Local Network PDN connection is not specified.