Security Gateways

Security Gateways (Gateways without carrier license) can be deployed at these interfaces:

Interface	Located Between	Description
Gi/SGi	Home PLMN and Internet	Protects the network from threats originating from the Internet, such as the Overbilling attack.
Go	GGSNs and CSCF SIPserver	Protects the CSCF Call Session Control Function. A set of roles for SIP servers or proxies that handle SIP signal packets in the IP Multimedia Subsystem (IMS). (Call Session Control Function) SIP server and enforces the SIP protocol. A major feature of this Gateway is RTP pinholing - i.e., it dynamically follows the negotiated RTP sessions, opening only the UDP ports required.
S11	eNodeB, MME and SGW	Inspects SCTP Stream Control Transmission Protocol, SCTP was defined as a transport protocol for SS7 messages to be transmitted over IP networks. and Diameter An authentication, authorization and accounting protocol that has many features not included in the legacy RADIUS protocol. performs IPSec encryption on GTP GPRS Tunnel Protocol.-U traffic.

Note - Mobile to mobile IMS communications can also be protected by the Gateway on the Go interface. To do so, mobile to mobile traffic must be routed from the GGSN Gateway GSN (GPRS Support Node). to the Gateway and back to the GGSN.