Control And Data Interfaces; R-Ewag-Ggsn Gn' Interface - Cisco ASR 5000 Administration Manual

▀ Feature Description
Here, Wi-Fi AAA acts as the RADIUS accounting client and R-eWAG as the RADIUS accounting server. R-eWAG
extracts the necessary attributes required to create the GTP tunnel to GGSN. R-eWAG resolves the APN to get the
GGSN address to which to create the GTP tunnel. In this release, the PDP context will be created with a dynamic IP
address. On successful creation of the GTP tunnel, R-eWAG creates the association between the GGSN-assigned IP
address and the Wi-Fi IP address.
All IP data packets generated by the UE in the WLAN are directed to the R-eWAG. The R-eWAG NATs the outer
source IP address (Wi-Fi IP address) with the GGSN-assigned IP address (MPC IP address) and forwards it to the
GGSN via the GTP tunnel. The application servers in the PDN identify the UE by the GGSN-assigned IP address.
In the downlink direction, the R-eWAG NATs the outer destination address (MPC IP address) to the Wi-Fi IP address
so that it is correctly routed to the UE in the WLAN.

Control and Data Interfaces

eWAG supports the following control and data interfaces:
 WLC/Wi-Fi AAA – R-eWAG:
 Control Plane: The following RADIUS messages are supported on this interface:
 Data Plane: There is direct IP connectivity between WLC and R-eWAG. R-eWAG receives the original
 eWAG – GGSN (Gn'):
 PDP Activation Messages: The following messages are supported over the Gn' reference point:

R-eWAG-GGSN Gn' Interface

▄ Cisco ASR 5000 Enhanced Wireless Access Gateway Administration Guide
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 Accounting Start
 Accounting Interim
 Accounting Stop
 Disconnect Request
IP packets generated by UE in WLAN. There could be other network elements (routers) between
WLC and R-eWAG, which can provide Layer 2 or Layer 3 tunneling to route the WLAN-generated
packets across the public network.
Important:
ICMP Processing: ICMP packets in the downlink direction are remapped and sent to the UE.
 Create PDP Context Request / Response
 Update PDP Context Request / Response: R-eWAG-initiated Update PDP Context scenario is
supported as explained in the Session Update Call Flow section.
 Delete PDP Context Request / Response
 Error Indication
 Version Not Supported
 GTP Payload Forwarding
 GTP Echo
RADIUS-based Enhanced Wireless Access Gateway Overview
In this release, R-eWAG does not support Tunneling (IP over GRE).