Performance analysis studies of distributed database systems in the past have assumed that the message transmission time between any two nodes of a network is constant. They disregard the effect of communication network parameters such as network traffic, network topology, and capacity of transmission channels. In this paper, an analytical model is used to estimate the delays in transmission channels of the long haul network supporting the distributed database system. The analysis shows that the constant transmission time assumption cannot be justified in many cases, and that the response time is sensitive to the parameters mentioned above. Extensions and performance analysis in the context of interconnection networks are also discussed.