Cisco Cisco ASR 5000
SGSN Pooling
▀ How it Works
▄ SGSN Administration Guide, StarOS Release 18
Non-local RAI and Target-NRI
For “Non-local RAI and Null-NRI” and “Non-local RAI and Target-NRI” options, the NB-RAI of other SGSN is
considered. It is non-local to the SGSN. No other configuration entries are present at the SGSN other than cc-profile
entries.
considered. It is non-local to the SGSN. No other configuration entries are present at the SGSN other than cc-profile
entries.
Mobility Management
The MS performs RA Updates and Attachments, which result in a change of the serving SGSN. In these procedures the
new SGSN requests MS specific parameters from the old SGSN. The default SGSN node uses the old RA together with
the NRI to derive the signalling address of the old SGSN from its configuration data.
new SGSN requests MS specific parameters from the old SGSN. The default SGSN node uses the old RA together with
the NRI to derive the signalling address of the old SGSN from its configuration data.
Address and TEID for the Control Plane
The relaying SGSN forwards the Context Request message to the interface of the old SGSN. The incoming request can
arrive over a S3 interface in case of MME or S3 in case of S4-SGSN. However the old RAI interface will be always S16.
arrive over a S3 interface in case of MME or S3 in case of S4-SGSN. However the old RAI interface will be always S16.
When the default-sgsn relays the message, if the UDP port number is absent in the request received, the default-sgsn adds
the “UDP source port number” IE while relaying. This is applicable for both Context Request and Identification Request
relay functionality.
the “UDP source port number” IE while relaying. This is applicable for both Context Request and Identification Request
relay functionality.
If in an Identification request message, “Address for control plane” is an optional IE. A SGSN within the same SGSN
pool with the old SGSN receives the Identification request message it includes the old IP address of the received message
in this optional parameter if this IE is not present and relays the message to the old SGSN.
pool with the old SGSN receives the Identification request message it includes the old IP address of the received message
in this optional parameter if this IE is not present and relays the message to the old SGSN.
In cases where default-sgsn has to send a negative response, it sends the message to the IP as indicated in the “S3/S16
Address and TEID for Control Plane” IE and destination port set as indicated by “UDP source port number” IE.
Address and TEID for Control Plane” IE and destination port set as indicated by “UDP source port number” IE.
If an SGSN within the same SGSN pool with the old SGSN receives this message, the SGSN decrements the Hop
Counter if this IE is present in the received message. Otherwise, the SGSN includes a Hop Counter with a configured
value and relays the message to the old SGSN. This is applicable for both Context Request and Identification Request
relay functionality.
Counter if this IE is present in the received message. Otherwise, the SGSN includes a Hop Counter with a configured
value and relays the message to the old SGSN. This is applicable for both Context Request and Identification Request
relay functionality.
For more information refer to 3GPP TS 29.274 (Table 7.3.5-1: Information Elements in a Context Request, Table 7.3.8-
1: Information Elements in an Identification Request).
1: Information Elements in an Identification Request).
For information on procedure to configure Iu/Gb flex on S16/S3 interface refer to the section “Configuration of SGSN
Pooling - Procedure to configure default SGSN (S16/S3 interface)”.
Pooling - Procedure to configure default SGSN (S16/S3 interface)”.
Standards Compliance
The SGSN Pooling feature complies with the following standards:
3GPP TS 23.236
3GPP TS 29.274