Cisco Cisco Packet Data Gateway (PDG)
SaMOG Gateway Overview
▀ SaMOG Services
▄ SaMOG Administration Guide, StarOS Release 18
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Proxy MIP Support—CGW
The SaMOG Gateway's CGW service provides the underlying mechanism to terminate per-session Proxy Mobile IP
(PMIPv6) tunnels from the WLAN infrastructure. To accomplish this, the CGW service acts as an Local Mobility
Anchor (LMA) towards the Wireless LAN Controllers (WLCs), which acts as a Mobile Access Gateway (MAG) with
PMIPv6 functionality as defined in RFC 5213. The LMA and MAG functions use Proxy Mobile IPv6 signaling to
provide network-based mobility management on behalf of the UEs attached to the network. With this approach, the
attached UEs are no longer involved in the exchange of signaling messages for mobility.
(PMIPv6) tunnels from the WLAN infrastructure. To accomplish this, the CGW service acts as an Local Mobility
Anchor (LMA) towards the Wireless LAN Controllers (WLCs), which acts as a Mobile Access Gateway (MAG) with
PMIPv6 functionality as defined in RFC 5213. The LMA and MAG functions use Proxy Mobile IPv6 signaling to
provide network-based mobility management on behalf of the UEs attached to the network. With this approach, the
attached UEs are no longer involved in the exchange of signaling messages for mobility.
The LMA function on the SaMOG Gateway's CGW service and the MAG function on the WLCs maintain a single
shared tunnel. To distinguish between individual subscriber sessions, separate GRE keys are allocated in the Proxy-MIP
Binding Update (PBU) and Proxy-MIP Binding Acknowledgement (PBA) messages between the CGW service and the
WLCs. To handle AAA server initiated disconnections, the CGW service supports RFC 5846 for Binding Revocation
Indication (BRI) and Binding Revocation Acknowledgement (BRA) messaging with the WLCs.
shared tunnel. To distinguish between individual subscriber sessions, separate GRE keys are allocated in the Proxy-MIP
Binding Update (PBU) and Proxy-MIP Binding Acknowledgement (PBA) messages between the CGW service and the
WLCs. To handle AAA server initiated disconnections, the CGW service supports RFC 5846 for Binding Revocation
Indication (BRI) and Binding Revocation Acknowledgement (BRA) messaging with the WLCs.
EoGRE Support—CGW
CGW connects 3G/4G subscribers to EPC/Inernet through the Trusted Wifi SSIDs served by EoGRE enabled
Residential Gateways. CGW acts as the tunnel endpoint for the EoGRE tunnel initiated from the Residential Gateway.
With the use of SSID-based WLAN access, the subscribers are authenticated based on the SSID they use in order to
connect to the WLAN. The Residential-GW/WLC maintains a separate SSID for providing the 3G/4G access to help the
UE in selecting the correct SSID for obtaining 3G/4G access through Wifi network. SaMOG (MRME) actas as the AAA
server and DHCP server for the UE attaching to the WLAN network. This helps in processing all the control packets
from the UE and maintaining the subscriber session to provide 3G/4G access. While acting as DHCP-Server, CGW
creates the PDP-Context with GGSN/P-GW to obtain the IP Address to be allocated to UE through DHCP-Reponse in
the access side. The DHCP and data packets generated by UE will be tunneled over EoGRE by Residential-GW/WLC
node to SaMOG.
Residential Gateways. CGW acts as the tunnel endpoint for the EoGRE tunnel initiated from the Residential Gateway.
With the use of SSID-based WLAN access, the subscribers are authenticated based on the SSID they use in order to
connect to the WLAN. The Residential-GW/WLC maintains a separate SSID for providing the 3G/4G access to help the
UE in selecting the correct SSID for obtaining 3G/4G access through Wifi network. SaMOG (MRME) actas as the AAA
server and DHCP server for the UE attaching to the WLAN network. This helps in processing all the control packets
from the UE and maintaining the subscriber session to provide 3G/4G access. While acting as DHCP-Server, CGW
creates the PDP-Context with GGSN/P-GW to obtain the IP Address to be allocated to UE through DHCP-Reponse in
the access side. The DHCP and data packets generated by UE will be tunneled over EoGRE by Residential-GW/WLC
node to SaMOG.
S2a Interface using PMIPv6—CGW
In Release 18 and later, the SaMOG Gateway can connect to the P-GW service over the S2a interface based on the
PMIPv6 protocol as specified by 3GPP TS 29.275, Release 11 standards. The SaMOG Gateway performs a SNAPTR-
based DNS query towards the DNS server to get the P-GW IP address, and initiates a PMIPv6-based registration
procedure (acting as a Mobile Access Gateway (MAG)) by sending a Proxy Binding Update message to the P-GW. The
IP address of the User Equipment (UE) allocated by P-GW (acting as the Local Mobility Anchor (LMA)) is then
received in the Proxy Binding Acknowledge message.
PMIPv6 protocol as specified by 3GPP TS 29.275, Release 11 standards. The SaMOG Gateway performs a SNAPTR-
based DNS query towards the DNS server to get the P-GW IP address, and initiates a PMIPv6-based registration
procedure (acting as a Mobile Access Gateway (MAG)) by sending a Proxy Binding Update message to the P-GW. The
IP address of the User Equipment (UE) allocated by P-GW (acting as the Local Mobility Anchor (LMA)) is then
received in the Proxy Binding Acknowledge message.
How S2a Interface using PMIPv6 Works
The UE performs an 802.11 initial attach procedures and connect to Access Points (AP) and Wireless LAN Controllers
(WLC), which in turn triggers a RADIUS-based authentication with the SaMOG Gateway. The SaMOG Gateway
selects a RADIUS/Diameter-based AAA server or AAA proxy based on the local profile configuration and performs a
RADIUS/Diameter-based authentication with the AAA server. After multiple rounds of authentication, the AAA server
confirms the authentication status for the UE and shares the subscriber profile with the SaMOG Gateway. The SaMOG
Gateway selects the P-GW based on the subscribers authorization information and setup a PMIPv6-based session with
the P-GW. The data between the SaMOG Gateway and P-GW are exchanged through GRE tunnels using GRE keys for
uplink and downlink data.
(WLC), which in turn triggers a RADIUS-based authentication with the SaMOG Gateway. The SaMOG Gateway
selects a RADIUS/Diameter-based AAA server or AAA proxy based on the local profile configuration and performs a
RADIUS/Diameter-based authentication with the AAA server. After multiple rounds of authentication, the AAA server
confirms the authentication status for the UE and shares the subscriber profile with the SaMOG Gateway. The SaMOG
Gateway selects the P-GW based on the subscribers authorization information and setup a PMIPv6-based session with
the P-GW. The data between the SaMOG Gateway and P-GW are exchanged through GRE tunnels using GRE keys for
uplink and downlink data.
Limitations
The following are the current limitations for the SaMOG S2a interface using PMIPv6:
As a PMIPv6-based S2a interface on the SaMOG Gateway cannot be used with a GGSN service, the SaMOG 3G
license is not supported.