Cisco Cisco Packet Data Gateway (PDG)
Evolved Packet Data Gateway Overview
▀ Network Deployment(s) and Interfaces
▄ ePDG Administration Guide, StarOS Release 18
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eNodeB
The eNodeB (evolved Node B) is the termination point for all radio-related protocols. As a network, E-UTRAN is
simply a mesh of eNodeBs connected to neighboring eNodeBs via the X2 interface.
simply a mesh of eNodeBs connected to neighboring eNodeBs via the X2 interface.
MME
The Cisco MME (Mobility Management Entity) is the key control node for the LTE access network. It works in
conjunction with the eNodeB and the Cisco S-GW to control bearer activation and deactivation. The MME is typically
responsible for selecting the Cisco P-GW for the UEs to access the PDN, but for secure access from untrusted non-
3GPP IP access networks, the ePDG is responsible for selecting the P-GW.
conjunction with the eNodeB and the Cisco S-GW to control bearer activation and deactivation. The MME is typically
responsible for selecting the Cisco P-GW for the UEs to access the PDN, but for secure access from untrusted non-
3GPP IP access networks, the ePDG is responsible for selecting the P-GW.
S-GW
The Cisco S-GW (Serving Gateway) routes and forwards data packets from the 3GPP UEs and acts as the mobility
anchor during inter-eNodeB handovers. The S-GW receives signals from the MME that control the data traffic. Every
3GPP UE accessing the EPC is associated with a single S-GW.
anchor during inter-eNodeB handovers. The S-GW receives signals from the MME that control the data traffic. Every
3GPP UE accessing the EPC is associated with a single S-GW.
P-GW
The Cisco P-GW (Packet Data Network Gateway) is the network node that terminates the SGi interface towards the
PDN. The P-GW provides connectivity to external PDNs for the subscriber UEs by being the point of entry and exit for
all subscriber UE traffic. A subscriber UE may have simultaneous connectivity with more than one P-GW for accessing
multiple PDNs. The P-GW performs policy enforcement, packet filtering, charging support, lawful interception, and
packet screening. The P-GW is the mobility anchor for both trusted and untrusted non-3GPP IP access networks. For
PMIP-based S2a and S2b interfaces, the P-GW hosts the LMA (Local Mobility Anchor) function.
PDN. The P-GW provides connectivity to external PDNs for the subscriber UEs by being the point of entry and exit for
all subscriber UE traffic. A subscriber UE may have simultaneous connectivity with more than one P-GW for accessing
multiple PDNs. The P-GW performs policy enforcement, packet filtering, charging support, lawful interception, and
packet screening. The P-GW is the mobility anchor for both trusted and untrusted non-3GPP IP access networks. For
PMIP-based S2a and S2b interfaces, the P-GW hosts the LMA (Local Mobility Anchor) function.
3GPP AAA Server
The 3GPP AAA (Authentication, Authorization, and Accounting) server provides UE authentication via the EAP-AKA
(Extensible Authentication Protocol - Authentication and Key Agreement) authentication method.
(Extensible Authentication Protocol - Authentication and Key Agreement) authentication method.
HSS
The HSS (Home Subscriber Server), is the master user database that supports the IMS (IP Multimedia Subsystem)
network entities. It contains subscriber profiles, performs subscriber authentication and authorization, and provides
information about the subscriber's location and IP information.
network entities. It contains subscriber profiles, performs subscriber authentication and authorization, and provides
information about the subscriber's location and IP information.
PCRF
The PCRF (Policy and Charging Rules Function) determines policy rules in the IMS network. The PCRF operates in the
network core, accesses subscriber databases and charging systems, and makes intelligent policy decisions for
subscribers.
network core, accesses subscriber databases and charging systems, and makes intelligent policy decisions for
subscribers.