  Internet service providers (ISPs) have a variety of quality attributes that
determine their attractiveness for data transmission, ranging from
quality-of-service metrics such as jitter to security properties such as the
presence of DDoS defense systems. ISPs should optimize these attributes in line
with their profit objective, i.e., maximize revenue from attracted traffic
while minimizing attribute-related cost, all in the context of alternative
offers by competing ISPs. However, this attribute optimization is difficult not
least because many aspects of ISP competition are barely understood on a
systematic level, e.g., the multi-dimensional and cost-driving nature of path
quality, and the distributed decision making of ISPs on the same path.
  In this paper, we improve this understanding by analyzing how ISP competition
affects path quality and ISP profits. To that end, we develop a game-theoretic
model in which ISPs (i) affect path quality via multiple attributes that entail
costs, (ii) are on paths together with other selfish ISPs, and (iii) are in
competition with alternative paths when attracting traffic. The model enables
an extensive theoretical analysis, surprisingly showing that competition can
have both positive and negative effects on path quality and ISP profits,
depending on the network topology and the cost structure of ISPs. However, a
large-scale simulation, which draws on real-world data to instantiate the
model, shows that the positive effects will likely prevail in practice: If the
number of selectable paths towards any destination increases from 1 to 5, the
prevalence of quality attributes increases by at least 50%, while 75% of ISPs
improve their profit.
