Abstract: Network delay is one of the important network performance parameters. End-to-end network delay inference could deal with the difficulties caused by other network measurements based on internal routers or muter cooperation.Under the condition of two assumptions, network topology structure is gotten and stable, link performance is temporally and spatially independent, network delay inference model was presented, a new approach to network internal link delay inference based on Pseudo Likelihood Estimation(PLE) with definite solution was proposed in this paper. Based on PLE solved with Expectation Maximum(EM) algorithm, inference units with definite solution were determined via back-to-back packet sending way. This approach could solve the problem of indefinite solution and lower the computation complexity. Experimental study was performed based on model computation. The experimental results show that the approach is accurate and effective.

Key words: Pseudo likelihood estimation(PLE) , Expectation maximum(EM) , Network link delay, Inference approach