Manual

Cisco Packet Data Serving Node (PDSN) Release 2.0
Redundancy and Load Balancing
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12.3(11)T
The Cisco PDSN also supports service provisioning using AAA servers and a user service profile. This
profile is defined by the user’s home network. It is referenced by the NAI. It is typically stored in the
AAA server in the user’s home network, along with the user authentication information, and is retrieved
as part of authorization reply.
Packet Transport for VPDN
The Cisco PDSN supports the transport of VPDN packets. If the operator offers VPDN services, the
mobile station can securely access private resources through a public Internet or dedicated links. The
VPDN tunnel extends from the PDSN/FA to the home IP network. The home IP network is the IP
network associated with the NAI.
Proxy Mobile IP
With Proxy Mobile IP as part of the PPP link initiation, the PDSN registers with a HA on behalf of the
mobile station. It obtains an address from the HA and forwards that address to the mobile station as part
of IPCP during PPP initialization.
Multiple Mobile IP Flows
The Cisco PDSN allows multiple IP access points from the same mobile station, as long as each IP flow
registers individually (each IP flow requires a unique NAI). This enables multiple IP hosts to
communicate through the same mobile access device and share a single PPP connection to the operator’s
network. For accounting purposes, it is important that the PDSN generate separate usage data records
(UDRs) for each flow to the AAA server.
Redundancy and Load Balancing
This section provides information about Intelligent PDSN Selection and Load Balancing for both the
Controller - Member cluster model, and for the Peer-to-Peer cluster model.
PDSN Clustering Peer-to-Peer and Controller / Member Architecture
The PDSN Clustering Peer-to-Peer Architecture (or PDSN Intelligent Selection and Load Balancing
feature), functions in a peer-to-peer model. All the PDSNs in the cluster share their load and served
MSID, and multicast their load and MSID to all other PDSNs in the cluster. This drains resources
because large MSID tables need to be stored on all the PDSNs, and because a large amount of traffic is
generated to exchange the information among the cluster members. This results in constraints on the
cluster size.
Currently, you can choose between Peer-to-Peer clustering, or Controller-Member clustering. In
Controller-Member clustering, a controller maintains load and session (such as A10 connection)
information for each member in the cluster, and performs member selection for load-balancing or
inter-PDSN handoff avoidance. The controller identifies the operational state of each member and
detects the failure of a member, or the failure of another controller. A member notifies the controller
about its load and session information.