STRUDEL: Supporting Trust in the Dynamic Establishment
of peering coaLitions
Daniele Quercia, Manish Lad, Stephen Hailes, Licia Capra, and Saleem Bhatti


Abstract

The Coalition Peering Domain (CPD) is a recent innovation within the field of mesh networking. 
It facilitates the management of community-area networks in a distributed and scalable form, 
allowing devices to pool their network resources (particularly egress links) to the common good.
However, as in P2P systems, this form of cooperative sharing architecture raises significant 
concerns about the effect of free-riders: nodes that utilise the bandwidth of others without 
providing an adequate return to the community.
To address this problem, we propose STRUDEL, a distributed framework that tackles the problem 
of free-riders and consists of: 
(i) a mechanism for the detection of malicious peers; 
(ii) a formal Bayesian trust model, to assess peers' trustworthiness; 
(iii) a forwarding mechanism based on the maximisation of trust-informed utility.


Extended Abstract (old)

Bandwidth demand imposed on networked devices has dramatically increased 
over the last few years, as a consequence of more sophisticated network 
applications being offered to a diverse spectrum of end-users. While 
data rates offered on local connections are usually higher than demand, 
the opposite happens with respect to Internet connectivity for most 
(especially mobile) devices. Therefore, we introduce a new genre of 
entity in the routing landscape, called Coalition Peering Domain (CPD), 
whose goal is fully exploit under-utilised local bandwidth so to 
maximise Internet connectivity.

A CPD consists of a local community (or mobile group) of users pooling 
their connectivity resources, through their combined connections to the 
Internet. Since the costs of network-equipped devices and Internet 
connectivity have significantly fallen in recent years, we can expect a 
growing number of users to be willing to participate to a CPD, thus 
creating the potential for an overall higher bandwidth availability.

However, Coalition Peering Domains rely on cooperative bandwidth 
sharing, which poses a "tragedy of the commons" dilemma: if too many 
people exploit others' connections, the excess of free-riders drives 
away the people that make the coalition valuable.

What if free-riders and, in general, misbehaving peers could be 
identified and, consequently, isolated? STRUDEL is a distributed trust 
management framework aiming at just that. It makes use of reputation 
evidence (i.e., direct experience evaluations and recommendations) to 
support trust and, consequently, the formation and sustenance of 
Coalition Peering Domains. STRUDEL supports a Bayesian formalization for 
trust formation and trust evolution, and it possesses a range of 
appropriate properties:
(i) support of a more fine-grained discrete trust metric than a binary 
one, which is used by current Bayesian trust models;
(ii) use of recommendations which are weighted according to 
recommenders' trustworthiness (to distinguish truth-telling from lying 
recommenders) and recommenders' subjective opinion (to resolve the 
different ontological views of the world held by different peers);
(iii) incorporation of the dimension of time to prevent from excessively 
capitalizing on past behavior.

Each node uses the Bayesian model to evaluate the trustworthiness of 
other nodes and thus to decide who to team up with. As a result, most of 
the traffic will flow through cooperating peers, while free-riders and 
misbehaving nodes will be excluded from the Coalition Peering Domain.