Manual

Cisco Packet Data Serving Node (PDSN) Release 2.0

Resource Management

12.3(11)T

On-Demand Address Pools (ODAP)

A PDSN Cluster can consist of up to ten MWAM cards, with one Cluster Controller and a Backup Cluster

Controller, and 48 PDSN IOS application image instances.

While MWAM cards provide a higher density of PDSNs, they make it necessary to allocate IP addresses

from a central source. This simplifies configuration so users will not have to configure a local pool of IP

addresses in each PDSN. With on-demand address pools, a DHCP/ODAP server manages a block of

addresses for each ODAP client application. The ODAP clients will request subnets from the ODAP

Subnet Allocation Server. These pools of subnetted IP addresses can dynamically increase or decrease

in size depending on the utilization of the IP addresses. A pool can be divided into subnets of various

sizes and the server assigns these subnets to routers running ODAP clients upon request. The PDSN will

run the ODAP client and use OSPF to aggregate the routes. The DHCP/ODAP Server can either be an

external Cisco AR, or run on a Cisco IOS image.

Note To use the ODAP feature, you must have Cisco IOS Release 12.2(15)T or later.

In this case, either the PDSN Cluster controller, or the backup cluster controller on one of the MWAM

cards, will be configured as the DHCP/ODAP Server. The local IP pools used for PDSN Home Agent

applications can also use the DHCP/ODAP Server for a subnet pool. A different name for the mobile IP

pools would be used in the configurations.

Pool Sizing Information

The PDSN configuration dictates that either the PDSN Cluster Controller or the PDSN Backup Cluster

Controller on one of the MWAM cards is configured as the DHCP Server with the ODAP Subnet

Allocation Server. These processors will have more capacity because they provide PDSN Clustering

functionality, and do not process the actual PDSN sessions. The ODAP clients reside on each of the

PDSN images.

You must decide how large to make the ODAP subnet pools based on the following variables:

• Number of MWAMs and number of PDSNs per MWAM

• How many total PDSN sessions will be required

• Incoming call rates

• Number of available IP addresses for the ODAP pool.

Use the following information to size the ODAP Subnet Allocation Server pool and to determine how

many IP addresses are required for all the PDSN applications.

• Each PDSN IOS application can support up to 20,000 PDSN sessions.

• Each MWAM contains:

–

Either a PDSN Cluster Controller or Backup Cluster Controller and up to 4 PDSN IOS images,

so each MWAM can support up to 80,000 sessions (4 * 20000).

Note If a Cluster Controller or Backup Cluster Controller is not configured, then 5 PDSN images

can be used allowing up to 100,000 sessions (5 * 20000).