Showing papers by "Mary Baker published in 2001"

Nettimer: a tool for measuring bottleneck link, bandwidth

Abstract: Measuring the bottleneck link bandwidth along a path is important for understanding the performance of many Internet applications Existing tools to measure bottleneck bandwidth are relatively slow, can only measure bandwidth in one direction, and/or actively send probe packets We present the nettimer bottleneck link bandwidth measurement tool, the libdpcap distributed packet capture library, and experiments quantifying their utility We test nettimer across a variety of bottleneck network technologies ranging from 192Kb/s to 100Mb/s, wired and wireless, symmetric and asymmetric bandwidth, across local area and cross-country paths, while using both one and two packet capture hosts In most cases, nettimer has an error of less than 10%, but at worst has an error of 40%, even on cross-country paths of 17 or more hops It converges within 10KB of the first large packet arrival while consuming less than 7% of the network traffic being measured

Flexible network support for mobile hosts

Abstract: Fueled by the large number of powerful light-weight portable computers, the expanding availability of wireless networks, and the popularity of the Internet, there is an increasing demand to connect portable computers to the Internet at any time and in any place. However, the dynamic nature of a mobile host's connectivity and its use of multiple network interfaces require more flexible network support than has typically been available for stationary workstations. This paper introduces two flow-oriented mechanisms, in the context of Mobile IP [25], to ensure a mobile host's robust and efficient communication with other hosts in a changing environment. One mechanism supports multiple packet delivery methods (such as regular IP or Mobile IP) and adaptively selects the most appropriate one to use according to the characteristics of each traffic flow. The other mechanism enables a mobile host to make use of multiple network interfaces simultaneously and to control the selection of the most desirable network interfaces for both outgoing and incoming packets for different traffic flows. We demonstrate the usefulness of these two network layer mechanisms and describe their implementation and performance.

Enabling the Long-Term Archival of Signed Documents through Time Stamping

Abstract: In this paper we describe how to build a trusted reliable distributed service across administrative domains in a peer-to-peer network. The application we use to motivate our work is a public key time stamping service called Prokopius. The service provides a secure, verifiable but distributable stable archive that maintains time stamped snapshots of public keys over time. This in turn allows clients to verify time stamped documents or certificates that rely on formerly trusted public keys that are no longer in service or where the signer no longer exists. We find that such a service can time stamp the snapshots of public keys in a network of 148 nodes at the granularity of a couple of days, even in the worst case where an adversary causes the maximal amount of damage allowable within our fault model.

Analysis of HTTP/1.1 performance on a wireless network

Abstract: We compare the performance of HTTP/1.0 and 1.1 on a high latency, low bandwidth wireless network. HTTP/1.0 is known to have low throughput and consume excessive network and server resources on today''s graphics-intensive web pages. A high latency, low bandwidth network only magnifies these problems. HTTP/1.1 was developed to remedy these problems. We show that on a Ricochet wireless network, HTTP/1.1 doubles throughput over HTTP/1.0 and decreases the number of packets sent by 60%.