GGSN Support in GPRS/UMTS Wireless Data Services  
▀ Network Deployment and Interfaces 
▄ Cisco ASR 5000 Series Product Overview 
  Gx: This is an optional Diameter protocol-based interface over which the GGSN communicates with a Charging 
Rule Function (CRF) for the provisioning of charging rules that are based on the dynamic analysis of flows 
used for an IP Multimedia Subsystem (IMS) session. The system provides enhanced support for use of Service 
Based Local Policy (SBLP) to provision and control the resources used by the IMS subscriber. It also provides 
Flow based Charging (FBC) mechanism to charge the subscriber dynamically based on content usage. 
Important:  The Gx interface is a license-enabled support. For more information on this support, refer Gx 
Interface Support in Features and Functionality - Optional Enhanced Feature Software section. 
 
  Gy: This is an optional Diameter protocol-based interface over which the GGSN communicates with a Charging 
Trigger Function (CTF) server that provides online charging data. Gy interface support provides an online 
charging interface that works with the ECS deep packet inspection feature. With Gy, customer traffic can be 
gated and billed in an ―online‖ or ―prepaid‖ style. Both time- and volume-based charging models are 
supported. In all of these models, differentiated rates can be applied to different services based on shallow or 
deep packet inspection. 
Important:  This interface is supported through Enhanced Charging Service. For more information on this 
support, refer Enhanced Charging Service Administration Guide. 
 
  GRE: This new protocol interface in GGSN platform adds one additional protocol to support mobile users to 
connect to their enterprise networks: Generic Routing Encapsulation (GRE). GRE Tunneling is a common 
technique to enable multi-protocol local networks over a single-protocol backbone, to connect non-contiguous 
networks and allow virtual private networks across WANs. This mechanism encapsulates data packets from 
one protocol inside a different protocol and transports the data packets unchanged across a foreign network. It 
is important to note that GRE tunneling does not provide security to the encapsulated protocol, as there is no 
encryption involved (like IPSEC offers, for example). 
Important:  The GRE protocol interface is a license-enabled support. For more information on this support, refer 
GRE Protocol Interface Support in Features and Functionality - Optional Enhanced Feature Software section. 
 
  S6b: This is an optional Diameter protocol-based interface over which the GGSN communicates with 3G 
AAA/HSS in LTE/SAE network for subscriber authorization. 
Important:  This interface is supported through license-enabled feature. For more information on this support, 
refer Common Gateway Access Support in guide. 
Important:  GGSN Software also supports additional interfaces. For more information on additional interfaces, 
refer Features and Functionality - Optional Enhanced Feature Software section.