Paper # 16

Effects of power conservation, wireless converage and cooperation on data 
dissemination among mobile devices

Problems

The paper presents 7DS, a novel p2p data sharing application. The highlights
of 7DS are 1) the peer might be mobile or stationary, and 2) the peer need
not be connected to the Internet

Strengths & New Ideas

1. 7DS allows for p2p data dissemination between peers that might not be connected
to the Internet. It does this in the following way. It assumes that at some
point the mobile host is connected to the Internet during which it downloads
useful information. Then when it needs to find something, it tries to connect
to the Internet using the URL but if the Internet connection is broken, it 
connects to the wireless LAN and queries it peers for that information. 

2. It is designed to run on heterogeneous devices(with different capabilities) that
can be mobile or stationary. For example, the device could be connected to the Internet
using a wired connection or just be an autonomous server attached to a data cache and
connected to a wireless LAN.

3. Data objects transmitted between peers can be encrypted for enhanced security and privacy.
This is done using PGP.

4. 7DS is designed to run in several modes based on the power available on the mobile device.
Based on the battery level, 7DS switches from playing a more active role(active querying, data
sharing) to a passive role (passive querying) or no role at all. The power management in
7DS is sophisticated as 7DS peers colloborate and synchronize the usage of their network
interfaces so that there is efficient utilization of power and bandwidth (as all the peers
would be active at the same time).

5. 7DS is easily deployed. The system can display both the reports as well as the complete
data information using any browser. It is also transparent to wired and wireless networks
as well as to different information providers.

6. The functional architecture of the 7DS networks is easily understood in the paper and
a comprehensive simulation has been carried out with good analysis of the results. This analysis
provides a good foundation for future work about high-density, energy constrained,pervasive, 
mobile p2p networks.

Weaknesses 

1. While the functional architecture is easily understood, a lot of the details have been
left out. For example, the paper explains that in case the Internet connection is unavaiable,
the host tries to retreive the information from a 7DS peer on its wireless LAN. However,
how the host connects to this Wireless LAN or knows about the peers on that LAN is unknown.

2. The MAC address of the host is used as part of the query paramater and is used as an
identifier. This compromises the identity of the host. The issue of anonymity has not been
addressed in this paper.

3. The 7DS results are based on simulations and have never been actually deployed in a live, functional
system. It would be interesting to see the results in a live environment
3. Once again, the entire system is a simulation.