Cisco Cisco Packet Data Gateway (PDG)

 

The APN provided by the AAA server is mapped to the locally configured P-GW or GGSN service IP. This eliminates 
the need for a DNS. The local P-GW or local GGSN assigns the IP using a locally configured IP pool after receiving the 
subscriber information from the AAA server. The subscriber information is received from the SaMOG service to the 
local P-GW service or local GGSN service through a GTP tunnel. This tunnel is set up within the same chassis.  

The SaMOG Gateway decides whether an APN should be locally broken out based on the following parameters:  



 

A configuration in the APN profile indicating if LBO is enabled for the APN 



 

Whether a “DEA-Flags” is received in the DEA messages on the STa interface. If DEA-Flags are received, 

SaMOG will verify if the “NSWO-Authorization” flag is set.  

If the APN profile is configured for LBO, and either no “DEA-Flags” are received in the DEA messages, or “DEA-
Flags” is received with the “NSWO-Authorization” flag set, SaMOG performs LBO for that APN. 

The decision on whether LBO can be done for a call is based on the following factors: 



 

A DIAMETER-based server can provide the following information: 



 

The MIP6_FEATURE_VECTOR AVP in DEA message can have the GTPV2_SUPPORTED flag set 

to indicate that the AAA server authorizes the GTP call through the EPC core (GGSN/PGW). 



 

The Bit 0 of the DEA_FLAG AVP (NSWO Authorization) is set to indicate that LBO is authorized for 

a session by the AAA server. 



 

The DIAMETER AAA server sends the APN information in the APN-Configuration AVP in DEA. This AVP 

may however be absent in case the AAA server authorizes only LBO, to indicate that any APN can be used for 
LBO for the subscriber. 



 

The operator can configure "local-offload" for each APN supporting LBO under the APN profile. However, the 

authorization from the AAA server will always be given preference over the local configuration. Local 
configuration will be used to take a decision when AAA server authorizes GTP as well as LBO for a call.  

The following table indicates different scenarios where the occurance of LBO is determined: 

Both GTP and LBO 
NOT supported 

— 

— 

Always an error condition 

Only GTP Supported 

No 

— 

Error Condition 

Yes 

— 

GTP Call setup with GGSN/P-GW 

Only LBO Supported 

No 

Yes 

LBO session established with the first APN with 
“local-offload” configured in local policy. 

No 

No APN configured in local 
policy 

Error Condition 

Yes 

No 

Error Condition 

Yes 

Yes 

LBO session established with received APN. 

Both GTP and LBO 
Supported 

No 

— 

Error Condition 

Yes 

No 

GTP session established with received APN.