Besides for frequently updated information, a user has to check the server periodically to get new or modified information. In general they simplify the implementation of such applications. However they also represent some drawbacks. First applications have to suffer from the heavy transmission latency. Second applications have to manage a lot of different connections when there are many users.
Third applications have no efficient means to avoid duplicated data traffic.
For one piece of information to get to one thousand users, applications have to send it at least one thousand times. In 1980's and early 90's, the pull applications were limited by the available networking technologies. By the model introduced by the emerging push technology, applications bring directly to mass consumers the information of interest rather than they having to fetch it themselves. This model overcomes the limitations of the pull model. It is very attractive because it allows users to get information as soon as it becomes available.