The mobile IP (MIP) protocol for IP version 4 provides continuous Internet connectivity to mobile hosts. However, currently it has some drawbacks in the areas of survivability, performance, interoperability with protocols for providing QoS. We have proposed an alternative protocol, mobile IP with location registers (MIP-LR), which overcomes some of these drawbacks and is closer to the "service node" database approach used in the public switched telephone network (PSTN): before launching a packet to the mobile host, the sender first queries a database, called the home location register (HLR), to obtain the recipient's current location. MIP-LR is designed for operation in enterprise environments or within logical administrative domains. We focus on showing how MIP-LR enhances the survivability of MIP by eliminating some of the functions which MIP introduces for mobility support, allowing the HLR to be placed outside the mobile's home network in case the latter is particularly vulnerable, and replicating and distributing HLRs. We present two schemes for managing the multiple HLRs and enabling mobile and correspondent hosts to dynamically discover the addresses of the HLRs serving a given mobile host. The first scheme introduces a set of translation server (TS) databases while the second uses a form of quorum consensus based on the triangle lattice (TL); for the latter we present an enhanced protocol called the optimistic TL(OTL). For both schemes we present algorithms for mobile host registration and packet delivery, protocols for recovery from HLR failures, and complexity analysis of the overhead involved.

The mobile IP (MIP) protocol for IP version 4 as being standardized by the Internet community provides continuous Internet connectivity to mobile hosts, without requiring any changes to existing routers and higher-layer applications. We propose an alternative protocol, mobile IP with location registers (MIP-LR) which is closer to the "service node" database approach used in the public switched telephone network (PSTN): before launching a packet to the mobile host, the sender first queries a database to obtain the recipient's current location. MIP-LR is designed for operation in enterprise environments or within logical administrative domains, as it requires a sending host to be aware of which hosts are potentially mobile and implement the MIP-LR protocol. The benefits of MIP-LR are that potentially long routes, called "triangle routes", from the sender to the mobile host are avoided, encapsulation of packets sent to a mobile host is not required, the load on the home network as well as the home and foreign agents is reduced, and there is substantially improved interoperability with protocols such as RSVP for providing QoS guarantees. We carry out a simplified average-case analysis of the costs and benefits of MIP-LR and show it can result in significant reductions in mean network costs compared to MIP.

This paper describes a new methodology for protocol design, using incremental construction of the protocol from elements called "protocol boosters" on an as-needed basis. Protocol boosters allow: (1) dynamic protocol customization to heterogeneous environments and (2) rapid protocol evolution. Unlike alternative adaptation approaches, such as link layer, conversion, and termination protocols, protocol boosters are both robust (end-to-end protocol messages are not modified) and efficient (do not replicate the functionality of the end-to-end protocol). We give examples of error and congestion control boosters, and give initial results from booster implementations.