Cisco Cisco ASR 5000
Network Requested Secondary PDP Context Activation
How It Works ▀
SGSN Administration Guide, StarOS Release 18 ▄
The QoS Requested, TFT and PCO are transparently passed through the S4-SGSN. The MS sends an Activate
Secondary PDP Context Request (linked Ti, Ti, NSAPI, PCO, and QoS Requested). Linked Ti, Ti, Qos Requested will
be as same as received in a previous message from the S4-SGSN. The TFT sent to MS may contain both the uplink and
downlink packet filters.
Secondary PDP Context Request (linked Ti, Ti, NSAPI, PCO, and QoS Requested). Linked Ti, Ti, Qos Requested will
be as same as received in a previous message from the S4-SGSN. The TFT sent to MS may contain both the uplink and
downlink packet filters.
On receiving a successful response (Activate Secondary PDP Context Request) in UMTS access, the S4-SGSN
establishes RAB with the serving RNC and then sends a Create Bearer Response with Accepted cause to S-GW. For
GPRS access, the RAB establishment is skipped.
establishes RAB with the serving RNC and then sends a Create Bearer Response with Accepted cause to S-GW. For
GPRS access, the RAB establishment is skipped.
The S4-SGSN includes the S4-U SGW FTeid (received in Create Bearer Request) in the Create Bearer Response to S-
GW. S-GW uses this to correlate the Bearer Contexts in Response with that of Request. The S4-SGSN completes the
procedure by sending an Activate Secondary PDP Context Accept to the MS.
GW. S-GW uses this to correlate the Bearer Contexts in Response with that of Request. The S4-SGSN completes the
procedure by sending an Activate Secondary PDP Context Accept to the MS.
A successful Network Requested Secondary PDP Context Activation Procedure is illustrated in the figure below.
Figure 66. Call Flow: Successful Network Requested Secondary Activation (S4-SGSN)
Unsuccessful Activation for S4-SGSN
After sending a Requested Secondary PDP Context Activation to the MS, the S4-SGSN starts the T3385 radio interface
retransmission timer. Upon expiry the S4-SGSN resends the message, a maximum of four retries. Upon the fifth expiry,
the S4-SGSN releases all allocated resources and sends a Create Bearer Response to the S-GW/P-GW with cause as
“UE not responding”.
retransmission timer. Upon expiry the S4-SGSN resends the message, a maximum of four retries. Upon the fifth expiry,
the S4-SGSN releases all allocated resources and sends a Create Bearer Response to the S-GW/P-GW with cause as
“UE not responding”.
The MS may choose to reject a Secondary Activation by network. In such cases, the MS sends a Requested Secondary
PDP Context Activation Reject message with an appropriate cause. S4-SGSN informs the SGW/PGW by sending a
Create Bearer Response with an appropriate GTPv2 cause mapped from an SM cause as shown in the table below.
PDP Context Activation Reject message with an appropriate cause. S4-SGSN informs the SGW/PGW by sending a
Create Bearer Response with an appropriate GTPv2 cause mapped from an SM cause as shown in the table below.
Table 25.
SM Cause to GTPv2 Cause Mapping
SM Cause
GTPv2 Cause
#26, Insufficient resources
#73, No resources available