PDN Gateway Overview
▀ Features and Functionality - Base Software
▄ Cisco ASR 5x00 Packet Data Network Gateway Administration Guide
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SRVCC PS-to-CS Handover Indication Support
This feature helps in notifying the PCRF about the exact reason for PCC rule deactivation on Voice bearer deletion.
This exact cause will help PCRF to then take further action appropriately.
This feature ensures complete compliance for SRVCC, including support for PS-to-CS handover indication when voice
bearers are released. The support for SRVCC feature was first added in StarOS Release 12.2.
SRVCC service for LTE comes into the picture when a single radio User Equipment (UE) accessing IMS-anchored
voice call services switches from the LTE network to the Circuit Switched domain while it is able to transmit or receive
on only one of these access networks at a given time. This removes the need for a UE to have multiple Radio Access
Technology (RAT) capability.
After handing over the PS sessions to the target, the source MME shall remove the voice bearers by deactivating the
voice bearer(s) towards S-GW/P-GW and setting the VB (Voice Bearer) flag of Bearer Flags IE in the Delete Bearer
Command message (TS 29.274 v9.5.0).
If the IP-CAN bearer termination is caused by the PS to CS handover, the PCEF may report related PCC rules for this
IP-CAN bearer by including the Rule-Failure-Code AVP set to the value PS_TO_CS_HANDOVER (TS 29.212 v10.2.0
and TS 23.203 v10.3.0).
Support for new AVP PS-to-CS-Session-Continuity (added in 3GPP Release 11) inside Charging Rule Install, which
indicates if the bearer is selected for PS to CS continuity is not added.
Subscriber Level Trace
Provides a 3GPP standards-based session level trace function for call debugging and testing new functions and access
terminals in an LTE environment.
As a complement to Cisco's protocol monitoring function, the P-GW supports 3GPP standards based session level trace
capabilities to monitor all call control events on the respective monitored interfaces including S5/S8, S2a, SGi, and Gx.
The trace can be initiated using multiple methods:
Management initiation via direct CLI configuration
Management initiation at HSS with trace activation via authentication response messages over S6a reference
interface
Signaling based activation through signaling from subscriber access terminal
Important:
Once the trace is provisioned, it can be provisioned through the access cloud via various signaling
interfaces.
The session level trace function consists of trace activation followed by triggers. The time between the two events is
treated much like Lawful Intercept where the EPC network element buffers the trace activation instructions for the
provisioned subscriber in memory using camp-on monitoring. Trace files for active calls are buffered as XML files
using non-volatile memory on the local dual redundant hard drives on the ASR 5x00 platform. The Trace Depth defines
the granularity of data to be traced. Six levels are defined including Maximum, Minimum and Medium with ability to
configure additional levels based on vendor extensions.
All call control activity for active and recorded sessions is sent to an off-line Trace Collection Entity (TCE) using a
standards-based XML format over a FTP or secure FTP (SFTP) connection. In the current release the IPv4 interfaces are
used to provide connectivity to the TCE. Trace activation is based on IMSI or IMEI. Once a subscriber level trace
request is activated it can be propagated via the S5/S8 signaling to provision the corresponding trace for the same
subscriber call on the P-GW. The trace configuration will only be propagated if the P-GW is specified in the list of
