Abstract not found

We explore the effects of host motion on the performance of active transport-level connections. Motion causes increased delays and packet losses while the network learns how to deliver data to a host's new location. Transport protocols incorrectly interpret these delays and losses as signs of network congestion. They consequently throttle their transmissions, further degrading performance. We quantify this degradation through measurements of protocol behavior in a wireless networking testbed. We show how retransmission backoffs introduce unacceptably long pauses in transport-level communication (0.9 seconds and longer), and how the slow growth of transmission windows prevents connections from again reaching maximum throughput for significant periods of time (1 second and longer). Our results demonstrate that transport protocols must be made aware of host motion, and identify which aspects of these protocols must be adapted to mobile computing environments. 1 Introduction Reliable tran...

Abstract- Host mobility is becoming an important issue due to the recent proliferation of notebook and palmtop computers, the development of wireless network interfaces, and the growth in global internetworking. This paper describes the design and implementation of a mobile host protocol, called the Internet Mobile Host Protocol (IMHP), that is compatible with the TCPDP protocol suite, and allows a mobile host to move around the Inter-net without changing its identity. In particular, IMHP provides host mobility over both the local and wide area, while remaining transparent to the user and to other hosts communicating with the mobile host. IMHP features route optimization and integrated authentication of all management packets. Route optimization allows a node to cache the location of a mobile host and to send future packets directly to that mobile host. By authenticating all management packets, IMHP guards against possible attacks on packet routing to mobile hosts, including the interception or redirection of arbitrary packets within the network. A simple new authentication mechanism is introduced that preserves the level of security found in the Internet today, while accommodating the transition to stronger authentication based on public key cryptog-raphy or shared keys that may either be manually administered or provided by a future Internet key management protocol. I.

Unlike distributed transactions, mobile transactions do not originate and end at the same site. The implication of the movement of such transactions is that classical atomicity, concurrency and recovery solutions must be revisited to capture the movement behavior. As an effort in this direction, we define a model of mobile transactions by building on the concepts of split transactions and global transactions in a multidatabase environment. Our view of mobile transactions, called Kangaroo Transactions, incorporates the property that transactions in a mobile computing system hop from one base station to another as the mobile unit moves through cells. Our model is the first to capture this movement behavior as well as the data behavior which reflects the access to data located in databases throughout the static network. The mobile behavior is dynamic and is realized in our model via the use of split operations. The data access behavior is captured by using the idea of global and local transactions in a multidatabase system. This research was partially supported by the National Science Foundation under Grant Number INT-9417907 and by a Massive Digital Data System (MDDS) effort sponsored by the Advanced Research and Development Committee of the Community Management Staff. Part of this research was performed while Margaret Dunham (then Margaret Eich) was on sabbatical at the University of Queensland in Brisbane, Australia. y This research was partially supported by Hughes Research Laboratories under Grant Number 906356. 1 1

This paper considers the problem of providing transparent support for very large numbers of mobile hosts within a large internetwork such as the Internet. The availability of powerful mobile computing devices and wireless networking products and services is increasing dramatically, but internetworking protocols such as IP used in the Internet do not currently support host movement. To address this need, the Internet Engineering Task Force (IETF) is currently developing protocols for mobile hosts in the Internet. This paper analyzes the problem to be solved, reviews the current state of that effort, and discusses its scalability to very large numbers of mobile hosts in a large internetwork. 1.

In this dissertation, we examine the problem of performing handoff quickly in cellular data networks. We define handoff as the process of reconfiguring the mobile host, wireless network and backbone wired network to support communication after a user enters a different cell of the wireless network. In order to support applications and protocols used on wired networks, the handoff processing must not significantly affect the typical end-to-end loss or delay of any communications. This dissertation concentrates on two specific areas of handoff processing: routing updates and state distribution. The techniques we use to solve these problems are: 1. Multicast to set up routing in advance of handoff. 2. Hints

This paper describes a mechanism, called "persistent connection," to preserve stream connections after the communicating peer exits and till it restarts. Such connections have many applications: to survive failures that crash one party, network partitions that cut off the two parties, and temporary disconnection in a mobile computing environment. They can also facilitate suspension of process execution in a limited resource environment and maintain connectivity when one party migrates from one machine to another. Persistent connection uses logical endpoints to hide disconnection from applications and to achieve location independent. It can be constructed from the normal "transient" connection that goes down with processes. Prototypes have been developed on Unix to provide persistent connections in both TCP-socket level and DCE RPC level. Many existing programs can benefit from this software to achieve transparence to disconnection and relocation. We conclude that persistent connection ...

This paper describes the Internet Mobile Host Protocol

Telecommunication service providers have recently begun to offer ubiquitous access to packetised data. As a result, the Internet is not limited to computers that are physically connected but is also available to users that are equipped with mobile devices. This ubiquitous access fuels the growth and the usage of the Internet even further, and thus the realisation of dynamic Internet. With the realisation of the dynamic Internet, increasing support is needed for Internet protocol (IP) and transmission control protocol (TCP) over wireless/mobile networks. Two areas

Host mobility is becoming an important issue due to the recent proliferation of notebook and palmtop computers, the development of wireless network interfaces, and the growth in global internetworking. This paper describes the design and implementation of a mobile host protocol, called the Internet Mobile Host Protocol (IMHP), that is compatible with the TCP/IP protocol suite, and allows a mobile host to move around the Internet without changing its identity. In particular, IMHP provides host mobility over both the local and wide area, while remaining transparent to the user and to other hosts communicating with the mobile host.