| We discuss the design of network and transport layer protocols for mobile networking. The network architecture used is unique in that it separates the mobile network(s) from the fixed or wired networks and provides connectivity between the two via special gateways. These gateways split all transport connections into two segments, allowing the use of protocols optimized for the wireless environment without affecting the installed base of network users. We describe problems affecting the most essential Internet protocols, i.e., TCP, UDP, and the Real-Time Protocol (RTP), when deployed in the wireless environment. We justify the need for versions of these protocols which are designed to cope with the unique constraints of the wireless link. We then propose mobile analogs of each of these protocols which compensate for those constraints. This suite of mobility-aware protocols allows the installed base of users to communicate efficiently with mobile users without requiring any changes outside of the mobile networks. We describe the implementations of M-TCP, M-UDP, and M-RTP, and show their performance to be far superior to that of their fixed network analogs. We also justify the split connection gateway approach using performance results from these implementations. Finally, we describe an efficient protocol for transferring mobile host state between gateway nodes during handoffs. |
