Cisco Cisco IOS Software Release 12.2(8)YY

Platforms: Cisco 7200 series routers

The Packet Of Disconnect (POD) feature on GGSN gives an external IP node the ability to terminate a 
user session by sending a POD packet. The POD packet is a Radius Disconnect Req message. The 
contents of this message is not yet standardized and is hence Cisco proprietary. The primary motivation 
of POD support on GGSN comes from the billing requirements (both Pre-Paid & Hot Billing) wherein 
a user session (PDP context) on GGSN can be terminated from an external entity. However, the scope 
of the POD feature is not limited to just the billing requirements.

Cisco’s POD implementation uses Radius messages (Disconnect Request, Disconnect Ack/Nak) and 
attributes described in RFC 2882 and RFC 2865. The ‘Disconnect Request’ message in addition contains 
the attributes 3GPP-IMSI and 3GPP-NSAPI (3GPP attributes) and optional ‘Teardown indicator’ (Cisco 
attribute). The GGSN upon receiving the Disconnect Request message, uses IMSI and NSAPI to identify 
the PDP context for a user and terminates the PDP context. If ‘Teardown indicator’ is also included in 
the message, the GGSN terminates all PDP contexts for that user which share the same PDP address 
(applicable only for GTPv1). The GGSN then sends Disconnect Ack/Nak (no attributes) response.

In order to configure POD on GGSN, the following CLI is used:

The port defaults to the UDP port 1700 on GGSN. This is the port on which, GGSN      listens for the 
POD request

Presently, the GGSN sends an Accounting-Request START message to the AAA server upon PDP 
context creation and Accounting-Request STOP message upon the PDP context deletion. The Interim 
Accounting feature will enable the GGSN to send Accounting-Request INTERIM-UPDATE (IAU) 
messages to the AAA server during the lifetime of a PDP context. The IAU message is sent only when 
an ‘Update Context Request’ or a new ‘Create Context Request’ is received for an existing PDP context 
from the SGSN indicating changes to certain parameters (SGSN Signaling address, QoS negotiated) 
only. This feature is a value-added feature to facilitate IP based billing.

This feature is first switched on at the box level and then enabled/disabled for each required APN. The 
box level CLI command is as follows:

The APN level enabling of the feature is done by selecting the appropriate APN and then entering the 
following CLI:

Router (config-access-point) [no] aaa-accounting   interim   update

To obtain lists of supported MIBs by platform and Cisco IOS release, and to download MIB modules, 
go to the Cisco MIB website on Cisco.com at 
http://www.cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml.