The hybrid fiber coax (HFC) network is a widely-used technology of broadband access networks to the home. The data-over-cable service interface specifications (DOCSIS) designed by the Multimedia Cable Network System Partners (MCNS) is the de facto standard in the cable industry. This paper studies the contention effect of DOCSIS in HFC networks. In particular, we focus on the performance of TCP. We develop a Markov model to estimate the probability of a CM transmitting a request in a randomly selected mini-slot. Based on the derived request transmission probability, the mean access delay for TCP transfers is calculated. We also conduct simulations via network simulator version 2 (ns-2) to validate the analysis.