  Network distance (Round Trip Time, RTT) is an important parameter for many
Internet distributed systems to optimize their performances. Network Coordinate
System (NCS) is assumed as a lightweight and scalable mechanism to predict
network distance between any two Internet hosts without explicit measurements.
Though many NCSes have been proposed in the literatures, they are not
satisfactory in terms of accuracy. In this paper, we propose to use delay
matrix to replace the NCS. This paper makes three contributions. First, we show
that not all the hosts need an independent network coordinate (NC). On the
contrary, most hosts can be represented as one or several nodes in NCS. Second,
we present an Internet Delay Matrix Service (IDMS) for representing network
distances without explicit measurements in Internet. Third, we describe two
delay matrices up to date delay matrix (UDM) and previous delay matrices (PDM)
for representing the network distances. Extensive simulations on our collected
Chinese Internet data sets show that IDMS is an accurate, efficient, scalable
and practical method for Chinese Internet. The performance of IDMS is better
than other existing approaches.
