Mobile operators and service providers have been looking for efficient solutions to the inter-domain IP mobility for the past fifteen years or so. The main motivation for this effort was the ability to continue an IP session when a host IP address had to change due to mobility. Client Mobile IP (CMIP for short) was introduced by Internet Engineering Task Force (IETF) to overcome this problem. The CMIP allows a mobile terminal (e.g., a laptop or a PDA) to keep its transport connection opened and continue to be reachable while moving. The CMIP also provides a common IP layer mobility across different access technologies. This would be quite attractive for mobile operators who might own several access networks of different types such as WiMax, 3GPP2 High Rate Packet Data (HRPD), or 3GPP Long Term Evolution (LTE), etc.While CMIP ensures seamless mobility for the user session but it introduces some deficiencies such as waste of airlink capacity due to signaling overhead and added complexity to the mobile terminal by requiring the client IP mobility software.To alleviate this problem IETF NETLMM WG is currently developing a protocol so called Proxy Mobile IP (PMIP) based on a network-based mobility management approach. The PMIP eliminates signaling overhead, reduces software complexity/cost and poses no requirement for a network interface to change IP address when the mobile node changes to a new router. The IETF standards for PMIP (PMIPv4 and PMIPv6 drafts) are primarily authored by Cisco IP mobility experts and SP network architects. Both drafts are near completion and will be published as new RFCs soon.