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Example annotated trace of Intra-PDSN handoff

Use this article as a reference of what an Intra-PDSN handoff trace looks like in a live network. In this case, three handoffs occurred within a few minutes, while the device remained dormant throughout the entire time period.

An Intra-PDSN handoff takes place when the PCF to which the PDSN is communicating with changes to a new PCF (with the PDSN staying the same). In this example, the handoffs are amongst EVDO PCFs.

The new PCF initiates a new connection via a Registration Request. No PPP renegotiation is needed. A radius accounting message is sent for the new leg of the call indicating connection-setup. An A11 Registration Update is sent to the previous PCF to tear down the previous session. A Radius accounting message is sent for that previous session indicating a disconnect reason of intra-pdsn-handoff. A final A11 registration request with lifetime = 0 is sent for the previous session to complete teardown. The appropriate acknowledgement and reply messages for all transactions are also exchanged. No MIP protocol exchanges are necessary, and neither is communication to the HA.

Color coding of the first handoff is used to distinguish messages for the previous and new sessions.

Significant datapoints

Here are all the significant IP addresses and IDs that you might consider relevant when trying to understand and analyze this trace:

Username/NAI (Network Access Identifier):

MSID/IMSI/Calling Station ID: 311281533730871

User IP address:

PCF (Packet Control Function), in order of handoffs and times:, 02:04:04, 02:05:09, session length = 64 seconds, 02:14:46, session length = 577 seconds

ST16 EVDO (Evolution Voice Data Only):

- PDSN (Packet Data Switching Network):

- NAS (Network Access Server) IP address:

- Radius Server:

- FA (Foreign Agent):

- HA (Home Agent):

- DNS servers:,

Note below that there had been 1 handoff already before the show sub or mon sub tracing was done. Another show sub full at the end shows that after the 3 handoffs traced, the total is 4.

See attached file for full details.

Imported from Starent Networks Knowledgebase Article # 10280