In the case of a GPRS access network, charging is usually done on the basis of the amount of data that is sent via a PDP context. The network operator can decide to charge specific PDP contexts differently: for example, a Multimedia Message Service (MMS) could be charged differently from "normal" Internet traffic. It is likely that operators will want to charge the signalling and media traffic that is related to the IMS in a different way than one based on the amount of transmitted data. To achieve this, IMS needs to correlate GPRS-specific charging records with IMS-specific charging information.
Figure 11.9. Media streams and transport in the example scenario.
Figure 11.10. Worst case scenario for media policing.
For the media session Tobias's UE needs to establish several media PDP contexts with the GGSN. The GGSN will start generating charging records whenever data (i.e., media) are sent over that PDP context. These charging records are based on the GPRS Charging ID (GCID) that is generated by the access network.
As described in Section 10.11, an IMS Charging ID (ICID) is created during initial registration by the P-CSCF. During a session the P-CSCF creates an additional ICID for the charging of media streams ...
With Safari, you learn the way you learn best. Get unlimited access to videos, live online training,
learning paths, books, interactive tutorials, and more.