PDN Gateway Overview
▀ Features and Functionality - Base Software
▄ Cisco ASR 5x00 Packet Data Network Gateway Administration Guide
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Local Breakout is a policy-based forwarding function that plays an important role in inter-provider roaming between
LTE service provider networks. Local Breakout is determined by the SLAs for handling roaming calls between visited
and home networks. In some cases, it is more beneficial to locally breakout a roaming call on a foreign network to the
visited P-W rather than incur the additional transport costs to backhaul the traffic to the Home network.
If two mobile operators have a roaming agreement in place, Local Break-Out enables the visited user to attach to the V-
PLMN network and be anchored by the local P-GW in the visited network. The roaming architecture relies on the HSS
in the home network and also introduces the concept of the S9 policy signaling interface between the H-PCRF in the H-
PLMN and the V-PCRF in the V-PLMN. When the user attaches to the EUTRAN cell and MME (Mobility
Management Entity) in the visited network, the requested APN name in the S6a NAS signaling is used by the HSS in
the H-PLMN to select the local S-GW (Serving Gateway) and P-GWs in the visited EPC network.
LTE Video Calling
In a Voice over LTE (VoLTE) scenario, the P-GW provides support for LTE Video Calling (LVC). No additional
configuration is required to support this functionality.
The P-GW checks the data usage quota for a subscriber at video call setup and periodically during an active video call.
The following functionality applies to post paid subscribers with data usage control:
Quota Check - Call Setup
If the P-GW determines that the subscriber has reached their data usage quota during the call setup:
The audio bearer portion of the call is activated.The video bearer portion of the call is NOT activated.The P-GW
sends the PCRF a Credit Control Request update (CCR-U) with “OUT_OF_CREDIT” event trigger and the
Final-Unit-Action (FUA) received from the OCS.The PCRF removes the Service Data Flow (SDF) from the P-
GW, and sends the P-CSCF indication of the failure of the video bearer channel setup.
Quota Check - During Active Video Call
If the subscriber exhausts their data usage during a video call:
The audio bearer portion of the call is preserved.The video bearer portion of the call is terminated.The P-GW
sends the PCRF CCR-U with “OUT_OF_CREDIT” event trigger and the Final-Unit-Action (FUA) received
from the OCS.The PCRF removes the SDF from the P-GW, and sends the P-CSCF indication of the failure of
the video bearer channel setup.
Management System Overview
The system's management capabilities are designed around the Telecommunications Management Network (TMN)
model for management - focusing on providing superior quality network element (NE) and element management system
(Cisco Web Element Manager) functions. The system provides element management applications that can easily be
integrated, using standards-based protocols (CORBA and SNMPv1, v2), into higher-level management systems - giving
wireless operators the ability to integrate the system into their overall network, service, and business management
systems. In addition, all management is performed out-of-band for security and to maintain system performance.
Cisco's O&M module offers comprehensive management capabilities to the operators and enables them to operate the
system more efficiently. There are multiple ways to manage the system either locally or remotely using its out-of-band
management interfaces.
These include:
Using the command line interface (CLI)
