Cisco Cisco ASR 5000
Serving GPRS Support Node (SGSN) Overview
Features and Functionality ▀
SGSN Administration Guide, StarOS Release 18 ▄
Bearer Request updates the QoS to the S-GW/P-GW after the PDP is active or UE activity is detected on S4-SGSN
respectively.
respectively.
UMTS-GSM AKA Support on the S4-SGSN
The S4-SGSN provides support for the following UMTS/GSM Authentication and Key Agreement (AKA) procedures:
SRNS relocation
Attach
PTMSI attach (foreign/local)
Service Request
Inter SGSN RAU
Timers Handling
Re-use of Vectors
Using the Peer SGSN/MME vectors (ISRAU/PTMSI attach) in the same or different PLMN
3G and 2G SGSN Routing Area Update
The S4-SGSN supports outbound Routing Area Update (RAU) procedures for a subscriber already attached on that
SGSN (that have PDP contexts anchored through S4 interface) and inbound RAU procedures for an EPC capable UE.
The RAU procedures are required to enable mobility across the UMTS and EPC core network coverage areas using the
S3 interface for context transfers.
SGSN (that have PDP contexts anchored through S4 interface) and inbound RAU procedures for an EPC capable UE.
The RAU procedures are required to enable mobility across the UMTS and EPC core network coverage areas using the
S3 interface for context transfers.
The S4-SGSN determines if the old peer node is an MME or SGSN based on the most significant bit of the LAC. If the
most significant bit of the LAC is set then the old peer node is an MME (and the RAI is mapped from GUTI). If the bit
is not set then the old RAI represents an SGSN.
most significant bit of the LAC is set then the old peer node is an MME (and the RAI is mapped from GUTI). If the bit
is not set then the old RAI represents an SGSN.
However, some operators have already used LAC values greater than 32768 (most significant bit set) for their existing
UMTS / GPRS networks. For such operators identification of a peer node through MSB bit of LAC will not work. In
these cases, operators can use the
UMTS / GPRS networks. For such operators identification of a peer node through MSB bit of LAC will not work. In
these cases, operators can use the
The following RAU procedures are supported for both 2G and 3G services:
2G and 3G Intra-SGSN RAU with and without S-GW relocation
2G and 3G Inter-SGSN/SGSN-MME RAU with and without S-GW relocation across S16 and S3 interfaces
Intra-SGSN Inter-RAT RAU with and without S-GW relocation
2G and 3G Intra RAU with and without S-GW Relocation
The S4-SGSN supports the intra-SGSN routing area update (ISRAU), which can occur in the following scenarios:
The MS changes its routing area
The periodic RAU timer expires for the MS
The MS changes its network capability
The S4-SGSN also supports intra SGSN, inter PLMN RAU requests. However, if the new PLMN’s operator policy is
configured to use the Gn interface, the PDP contexts are not transferred from the S4 interface to the Gn interface.
configured to use the Gn interface, the PDP contexts are not transferred from the S4 interface to the Gn interface.