Cisco Cisco ASR 5000
Serving GPRS Support Node (SGSN) Overview
▀ Features and Functionality
▄ SGSN Administration Guide, StarOS Release 18
In an LTE network, the MME group code is mapped to the LAC and therefore the LAC and MME group code should be
separate. The S4-SGSN provides a customized solution for this problem by identifying the valid MME group codes,
which it uses to identify whether the received LAC is a native LAC or a LAC mapped from GUTI (i.e., an MME group
code part of GUTI).
separate. The S4-SGSN provides a customized solution for this problem by identifying the valid MME group codes,
which it uses to identify whether the received LAC is a native LAC or a LAC mapped from GUTI (i.e., an MME group
code part of GUTI).
S4-SGSN Support for Fallback to V1 Cause Code in GTPv2 Context Response
As per revised 3GPP TS 29.274 v8.6.0, the Context Response message received from a peer SGSN can have a cause
code “Fallback to GTP-V1”, if the peer SGSN had provided a Gn interface for a subscriber due to local policy. When a
new SGSN receives a Context Response with cause code as “Fallback to GTP-v1” it performs a GTP-v1 SGSN Context
Request, Context Response and Context Ack with the peer SGSN to obtain the subscribers MM and PDP contexts.
code “Fallback to GTP-V1”, if the peer SGSN had provided a Gn interface for a subscriber due to local policy. When a
new SGSN receives a Context Response with cause code as “Fallback to GTP-v1” it performs a GTP-v1 SGSN Context
Request, Context Response and Context Ack with the peer SGSN to obtain the subscribers MM and PDP contexts.
S4-SGSN Support for Mobility Management Procedures
To support the S6d/Gr interface, the S4-SGSN supports the following mobility management procedures over the those
(HSS/HLR) interfaces:
(HSS/HLR) interfaces:
Attach
Service request
Detach
Iu-Release procedures
Operator policy override for the Gn/S4 interface for EPC subscribers
Zone code
ARD
ADD
Operator policy-based Mobility Management context handling
QoS Mapping Support
The S4-SGSN supports the configuration of QoS parameters to ensure proper QoS parameter mapping between the S4-
SGSN and EPC S-GWs, P-GWs, and UEs.
SGSN and EPC S-GWs, P-GWs, and UEs.
The S4-SGSN communicates QoS parameters towards the S-GW and P-GW in EPC QoS. However, it sends QoS
towards the UE in the QoS format defined in the GMM/SM specification (TS 24.008). 3GPP defines a mapping for EPS
QoS to pre-release 8 QoS in TS 23.401, Annex E. On the S4-SGSN, operators can configure the quality of service
(QoS) parameters as call-control-profiles that will ensure proper QoS mapping between the S4-SGSN and the EPC
gateways (P-GW and S-GW) and UEs.
towards the UE in the QoS format defined in the GMM/SM specification (TS 24.008). 3GPP defines a mapping for EPS
QoS to pre-release 8 QoS in TS 23.401, Annex E. On the S4-SGSN, operators can configure the quality of service
(QoS) parameters as call-control-profiles that will ensure proper QoS mapping between the S4-SGSN and the EPC
gateways (P-GW and S-GW) and UEs.
The configured call-control-profiles will be used if the S4 interface is chosen for PDP activation, but the subscription
does not have an EPS subscription. Therefore, GPRS subscription data (which uses QoS in pre-release 8 format), will be
mapped to EPS QoS behavior. The Allocation and Retention policy will be mapped to EPS ARP using the configured
call control profiles.
does not have an EPS subscription. Therefore, GPRS subscription data (which uses QoS in pre-release 8 format), will be
mapped to EPS QoS behavior. The Allocation and Retention policy will be mapped to EPS ARP using the configured
call control profiles.
If the QoS mapping configuration is not used, the following default mappings are used:
Default ARP high-priority value = 5
Default ARP medium-priority value = 10
Default pre-emption capability = shall-not-trigger-pre-emption