An ad hoc network is a collection of wireless mobile hosts forming a temporary network without the aid of any established infrastructure or centralized administration. In such an environment, it may be necessary for one mobile host to enlist the aid of other hosts in forwarding a packet to its destination, due to the limited range of each mobile host’s wireless transmissions. This paper presents a protocol for routing in ad hoc networks that uses dynamic source routing. The protocol adapts quickly to routing changes when host movement is frequent, yet requires little or no overhead during periods in which hosts move less frequently. Based on results from a packet-level simulation of mobile hosts operating in an ad hoc network, the protocol performs well over a variety of environmental conditions such as host density and movement rates. For all but the highest rates of host movement simulated, the overhead of the protocol is quite low, falling to just 1 % of total data packets transmitted for moderate movement rates in a network of 24 mobile hosts. In all cases, the difference in length between the routes used and the optimal route lengths is negligible, and in most cases, route lengths are on average within a factor of 1.01 of optimal. 1.

We investigate the performance of TCP connections over ATM networks without ATM-level congestion control, and compare it to the performance of TCP over packet-based networks. For simulations of congested networks, the effective throughput of TCP over ATM can be quite low when cells are dropped at the congested ATM switch. The low throughput is due to wasted bandwidth as the congested link transmits cells from `corrupted' packets, i.e., packets in which at least one cell is dropped by the switch. We investigate two packet discard strategies which alleviate the effects of fragmentation. Partial Packet Discard, in which remaining cells are discarded after one cell has been dropped from a packet, somewhat improves throughput. We introduce Early Packet Discard, a strategy in which the switch drops whole packets prior to buffer overflow. This mechanism prevents fragmentation and restores throughput to maximal levels.

An ad hoc network is a collection of wireless mobile hosts forming a temporary network withoutthe aid of any centralized administration or standard support services. In such an environment, it may be necessary for one mobile host to enlist the aid of others in forwarding a packet to its destination, due to the limited propagation range of each mobile host's wireless transmissions. Some previous attempts have been made to use conventional routing protocols for routing in ad hoc networks, treating each mobile host as a router. This position paper points out a number of problems with this design and suggests a new approach based on separate route discovery and route maintenance protocols.

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 paper we will show the ideas that are the foundation for the Borderland architecture. We have looked at two views of how researchers are thinking about computers in the future, wearable computers and pervasive computing. Wearable computers is the view where the user is wearing a computer and by that augment the user's view on his environment with additional digital information. Wearable computers have their strength in that they mostly do not have any requirements on the environment and that the user is in control of his integrity and security.

The trade-off between protocol structure and protocol performance is usually treated as a balancing act, with improvements on one side coming at the expense of the other side. The goal of this thesis is to eliminate the structure/performance trade-off with a combination of structuring and compilation techniques. The structuring techniques are based on data-stream computations and give the protocol developer a convenient way of arranging and implementing certain types of protocol functions. The compilation techniques remove the inefficiencies introduced by the structuring techniques and further tailor the code to the host system, providing a high performance implementation. Prior Work has resulted in a data-stream architecture for data-touching protocol functions, built a compiler that translates a data-stream language into executable code, and implemented a set of data-touching protocol functions in the data-stream language to determine the feasibility of both the architecture and the ...

In recent years, a wide variety of mobile computing devices has emerged, including portables, palmtops, and personal digital assistants. Providing adequate network connectivity for these devices will require a new generation of wireless LAN technology. In this paper we study media access protocols for a single channel wireless LAN being developed at Xerox Corporation's Palo Alto Research Center. We start with the MACA media access protocol first proposed by Karn [9] and later refined by Biba [3] which uses an RTSCTS -DATA packet exchange and binary exponential backoff. Using packet-level simulations, we examine various performance and design issues in such protocols. Our analysis leads to a new protocol, MACAW, which uses an RTS-CTSDS -DATA-ACK message exchange and includes a significantly different backoff algorithm. 1 Introduction In recent years, a wide variety of mobile computing devices have emerged, including palmtops, personal digital assistants, and portable computers. While ...