The performance of simple error control protocols under correlated packet losses

A study is made of the effect of correlated packet losses for some simple automatic repeat request (ARQ) protocols: go-back-∞, and Blast. The packet losses are modeled by a two state Markov chain and it is assumed that the round trip delay is random. Expressions are derived for the z-transform and the first and second moments of the time [τ], taken to successfully transmit N packets for go-back-∞ and variations of the Blast protocol. For go-back-∞, bounds are derived for E[τ], and it is shown that for a fixed mean round trip delay, E[τ] is minimized when the distribution of the round trip delay is such that its variance is minimized. Some of the protocols investigated show a significant improvement in performance when packet losses occur in bursts. The authors propose and analyze a variation of the Blast protocol which seems particularly suited to bursty packet loss situations