PPP migration: a technique for low-latency handoff in CDMA2000 networks

In current CDMA2000 standard, a packet data serving node (PDSN) acts as an IP gateway to the Internet. Mobile nodes (MN) connect to a PDSN using a point-to-point (PPP) session and IP packets are tunneled over the PPP session from the client to the PDSN which then routes the packets onto a packet network. A CDMA2000 network is a hierarchical network where packets from an MN to the PDSN are transported over a radio-access network (RAN). An MN could move from one RAN to another and still be anchored under the same PDSN; it is also possible that when an MN moves from one RAN to another, the anchor PDSN itself becomes different. In the latter case, there are two ways to handle mobility: (i) tear down the PPP session from the MN to the old PDSN and establish a new PPP session from the MN to the new PDSN, and (ii) use the fast-handoff mechanism as specified in the CDMA2000 standard where a P-P (PDSN to PDSN) tunnel is established to tunnel PPP frames from the old PDSN to the new PDSN and then to the MN. In this paper, we present a better approach to handling mobility than either of the above two techniques. The method is to migrate the PPP state from the old PDSN to the new PDSN transparent to the MN; once the PPP state migration is completed, the new PDSN will serve as the IP gateway to the MN. We have implemented the PPP migration technique and through experimental measurements show its benefits.