Cisco ASR 5000 series Product Overview page 289

GGSN Support in GPRS/UMTS Wireless Data Services
In support of both mobile and network originated subscriber PDP contexts, the system GGSN provides the following
network interfaces:
Gn: This is the interface used by the GGSN to communicate with SGSNs on the same GPRS/UMTS Public
Land Mobile Network (PLMN). This interface serves as both the signaling and data path for establishing and
maintaining subscriber PDP contexts.
The GGSN communicates with SGSNs on the PLMN using the GPRS Tunnelling Protocol (GTP). The
signaling or control aspect of this protocol is referred to as the GTP Control Plane (GTPC) while the
encapsulated user data traffic is referred to as the GTP User Plane (GTPU).
One or more Gn interfaces can be configured per system context.
Ga: This is the interface used by the GGSN to communicate with the Charging Gateway (CG). The charging
gateway is responsible for sending GGSN Charging Data Records (G-CDRs) received from the GGSN for each
PDP context to the billing system. System supports TCP and UDP as transport layer for this interface.
The GGSN communicates with the CGs on the PLMN using GTP Prime (GTPP).
One or more Ga interfaces can be configured per system context.
Gc: This is the interface used by the GGSN to communicate with the Home Location Register (HLR) via a GTP-
to-MAP (Mobile Application Part) protocol convertor. This interface is used for network initiated PDP
contexts.
For network initiated PDP contexts, the GGSN will communicate with the protocol convertor using GTP. The
convertor, in turn, will communicate with the HLR using MAP over Signaling System 7 (SS7).
One Gc interface can be configured per system context.
Gi: This is the interface used by the GGSN to communicate with Packet Data Networks (PDNs) external to the
PLMN. Examples of PDNs are the Internet or corporate intranets.
Inbound packets received on this interface could initiate a network requested PDP context if the intended MS is
not currently connected.
For systems configured as a GGSN/FA, this interface is used to communicate with HAs for Mobile IP and
Proxy Mobile IP support.
One or more Gi interfaces can be configured per system context. For Mobile IP and Proxy Mobile IP, at least
one Gi interface must be configured for each configured FA service. Note that when the system is
simultaneously supporting GGSN, FA, and HA services, traffic that would otherwise be routed over the Gi
interface is routed inside the chassis.
Gp: This is the interface used by the GGSN to communicate with GPRS Support Nodes (GSNs, e.g. GGSNs
and/or SGSNs) on different PLMNs. Within the system, a single interface can serve as both a Gn and a Gp
interface.
One or more Gn/Gp interfaces can be configured per system context.
AAA: This is the interface used by the GGSN to communicate with an authorization, authentication, and
accounting (AAA) server on the network. The system GGSN communicates with the AAA server using the
Remote Authentication Dial In User Service (RADIUS) protocol.
This is an optional interface that can be used by the GGSN for subscriber PDP context authentication and
accounting.
DHCP: This is the interface used by the GGSN to communicate with a Dynamic Host Control Protocol (DHCP)
Server. The system can be configured as DHCP-Proxy or DHCP Client to provide IP addresses to MS on PDP
contexts activation the DHCP server dynamically.
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