Cisco Cisco ASR 5000
SGSN-MME Combo Optimization
How It Works ▀
SGSN Administration Guide, StarOS Release 18 ▄
How It Works
Subscriber Movement from MME to SGSN: Subscription information is first fetched by the MME. On subscriber
movement to a co-located SGSN, the SGSN sends a ULR with "skip-subscriber-data" flag set and the HSS sends a ULA
(with or without subscription data depending on time of MME update).
movement to a co-located SGSN, the SGSN sends a ULR with "skip-subscriber-data" flag set and the HSS sends a ULA
(with or without subscription data depending on time of MME update).
Subscriber Movement from SGSN to MME: Subscription information is first fetched by the SGSN. On subscriber
movement to a co-located MME, the MME sends a ULR with "skip-subscriber-data" flag set and the HSS sends a ULA
(with or without subscription data depending on time of SGSN update).
movement to a co-located MME, the MME sends a ULR with "skip-subscriber-data" flag set and the HSS sends a ULA
(with or without subscription data depending on time of SGSN update).
Architecture
Figure 89. SGSN-MME Combo Node
The above diagram displays the interworking of various modules when the Combo Optimization feature is enabled in a
co-located SGSN-MME setup.
co-located SGSN-MME setup.
When the subscriber does RAU from MME to SGSN, or vice versa, a DNS query is initiated to fetch the address of the
peer node. Based on the IP address obtained, the peer MME or SGSN is selected. When a DNS response is received
with a list of peer SGSN addresses, the MME matches the configured EGTP/SGTP SGSN service address in the system
and uses it for the S3/Gn UE Context Transfer procedures. If a DNS response is not received and a locally configured
EGTP/SGTP SGSN service is present as a peer-SGSN, the peer-SGSN will be selected. Context transfer and copying of
subscription information happens internally between the SGSN and the MME nodes. The SGSN maintains the s6d
interface towards the HSS and the MME maintains the S6a interface towards the HSS. All network-initiated messages
are sent separately towards the SGSN and the MME nodes respectively.
peer node. Based on the IP address obtained, the peer MME or SGSN is selected. When a DNS response is received
with a list of peer SGSN addresses, the MME matches the configured EGTP/SGTP SGSN service address in the system
and uses it for the S3/Gn UE Context Transfer procedures. If a DNS response is not received and a locally configured
EGTP/SGTP SGSN service is present as a peer-SGSN, the peer-SGSN will be selected. Context transfer and copying of
subscription information happens internally between the SGSN and the MME nodes. The SGSN maintains the s6d
interface towards the HSS and the MME maintains the S6a interface towards the HSS. All network-initiated messages
are sent separately towards the SGSN and the MME nodes respectively.